Drive circuit and liquid ejecting apparatus

The present application is based on, and claims priority from JP Application Serial Number 2019-157937, filed Aug. 30, 2019, the disclosure of which is hereby incorporated by reference here in its entirety.

BACKGROUND
1. Technical Field

The present disclosure relates to a drive circuit and a liquid ejecting apparatus.

2. Related Art

It is known that an ink jet printer which is an example of a liquid ejecting apparatus ejecting a liquid such as ink to print an image or a document uses a piezoelectric element such as a piezo element. The piezoelectric element in a print head is provided to correspond to a plurality of nozzles for ejecting ink and a cavity for storing the ink ejected from the nozzles. As the piezoelectric element is displaced according to a drive signal, a vibration plate provided between the piezoelectric element and the cavity bends, and a volume of the cavity changes. Thereby, a predetermined amount of ink is ejected from the nozzles at a predetermined timing, and dots are formed on a medium.

JP-A-2017-043007 discloses a liquid ejecting apparatus that supplies a drive signal generated based on printing data to an upper electrode, supplies a reference voltage to a lower electrode, of a piezoelectric element that is displaced based on a potential difference between the upper electrode and a lower electrode and controls whether or not the drive signal is supplied by a selection circuit (switch circuit), for a piezoelectric element that is displaced based on a potential difference between the upper electrode and a lower electrode, thereby, controlling displacement of the piezoelectric element and ejecting ink.

Before a piezoelectric element used in a liquid ejecting apparatus that ejects ink based on displacement of the piezoelectric element as described in JP-A-2017-043007 is incorporated in a printing head, a polarization process of applying a predetermined DC electric field to a piezoelectric body of the piezoelectric element to align polarization directions is performed. Piezoelectric characteristics of the piezoelectric body are developed by the polarization process.

However, if an electric field in a direction opposite to the polarized DC electric field is supplied to the polarized piezoelectric element, disorder occurs in the polarization directions of the piezoelectric body aligned by the polarization process. The disorder in the polarization directions degrades the piezoelectric characteristics of the piezoelectric element, and as a result, there is a possibility that the piezoelectric element may perform an abnormal operation.

SUMMARY

In one aspect of a drive circuit according to the present disclosure, a drive circuit for driving a first drive element having a first terminal and a second terminal and driving a second drive element having a third terminal and a fourth terminal, includes a first drive signal output circuit that is electrically coupled to the first terminal and outputs a first drive signal for driving the first drive element, and a second drive signal output circuit that is electrically coupled to the third terminal and outputs a second drive signal for driving the second drive element. The first drive signal output circuit includes a first reference voltage signal output circuit that outputs a first reference voltage signal. The first reference voltage signal output circuit is electrically coupled to the second terminal and the fourth terminal. The second drive signal output circuit is not electrically coupled to the second terminal and the fourth terminal. The first drive signal output circuit starts startup after the second drive signal output circuit.

In the one aspect of the drive circuit, the first drive signal output circuit may stop an operation before the second drive signal output circuit.

In the one aspect of the drive circuit, the second drive signal output circuit may include a second reference voltage signal output circuit that outputs a second reference voltage signal, and an output terminal that outputs the second reference voltage signal, and the output terminal may be electrically decoupled.

In the one aspect of the drive circuit, a drive circuit may further include a third drive element having a fifth terminal and a sixth terminal and a fourth drive element having a seventh terminal and an eighth terminal, and a third drive signal output circuit that is electrically coupled to the fifth terminal and outputs a drive signal for driving the drive element and a fourth drive signal output circuit that is electrically coupled to the seventh terminal and outputs a fourth drive signal for driving the fourth drive element. The third drive signal output circuit may include a third reference voltage signal output circuit that outputs a third reference voltage signal. The third reference voltage signal output circuit may be electrically coupled to the sixth terminal and the eighth terminal. The fourth drive signal output circuit may not be electrically coupled to the sixth terminal and the eighth terminal. The third drive signal output circuit may start startup after the fourth drive signal output circuit.

One aspect of a liquid ejecting apparatus according to the present disclosure includes one aspect of the drive circuit, and a liquid ejecting head that includes the first drive element and the second drive element and ejects a liquid by driving at least one of the first drive element and the second drive element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating a schematic configuration of a liquid ejecting apparatus.

FIG. 2 is a diagram illustrating an electrical configuration of the liquid ejecting apparatus.

FIG. 3A is a first half of a diagram illustrating an example of configurations and electrical coupling of a drive circuit and a head unit.

FIG. 3B is a second half of the diagram illustrating the example of the configurations and electrical coupling of the drive circuit and the head unit.

FIG. 4 is a diagram illustrating a schematic configuration of one of a plurality of ejecting sections.

FIG. 5 is a diagram illustrating an example of a waveform of a drive signal COM.

FIG. 6 is a diagram illustrating an electrical configuration of a drive signal selection control circuit.

FIG. 7 is a diagram illustrating an electrical configuration of a selection circuit corresponding to one ejecting section.

FIG. 8 is a diagram illustrating decoding content in a decoder.

FIG. 9 is a diagram illustrating an operation of the drive signal selection control circuit.

FIG. 10 is a diagram illustrating a configuration of a power supply voltage control circuit.

FIG. 11 illustrates an example of a configuration of a power supply voltage blocking circuit and a power supply voltage discharging circuit.

FIG. 12 is a diagram illustrating a configuration of an inrush current reduction circuit.

FIG. 13 is a diagram illustrating an example of a configuration of the drive control circuit.

FIG. 14 is a diagram illustrating an example of a configuration of a drive signal discharging circuit.

FIG. 15 is a diagram illustrating a configuration of a reference voltage signal output circuit.

FIG. 16 is a diagram illustrating a configuration of a VHV control signal output circuit.

FIG. 17 is a diagram illustrating a configuration of a state signal input/output circuit.

FIG. 18 is a diagram illustrating a configuration of a abnormality signal input/output circuit.

FIG. 19 is a diagram illustrating an example of a configuration of a constant voltage output circuit.

FIG. 20 is a diagram illustrating an example of state transition of the drive control circuit.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, preferred embodiments of the present disclosure will be described with reference to the drawings. The drawings are used for the sake of convenient description. The embodiments which will be described below do not unduly limit contents of the present disclosure described in claims. Further, all configurations which will be described below are not necessarily essential configuration elements of the disclosure.

1. Configuration of Liquid Ejecting Apparatus

A printing apparatus which is an example of a liquid ejecting apparatus according to the present embodiment is an ink jet printer that prints an image including characters, figures, and the like according to image data onto a medium such as paper by ejecting ink from nozzles according to the image data input from an external host computer or the like.

FIG. 1 is a diagram illustrating a schematic configuration of a liquid ejecting apparatus 1. FIG. 1 illustrates a direction X in which a medium P is transported, a direction Y which intersects with the direction X and in which a moving object 2 reciprocates, and a direction Z in which ink is ejected. Hereinafter, the direction X, the direction Y, and the direction Z are described as being orthogonal to each other, but a configuration included in the liquid ejecting apparatus 1 is not limited to being disposed to be orthogonal to each other. Further, in the following description, the direction Y in which the moving object 2 moves may be referred to as a main scanning direction, and the direction X in which the medium P is transported may be referred to as a transport direction.

As illustrated in FIG. 1, the liquid ejecting apparatus 1 includes the moving object 2 and a moving mechanism 3 that reciprocates the moving object 2 in the direction Y. The moving mechanism 3 includes a carriage motor 31 serving as a drive source of the moving object 2, a carriage guide shaft 32 having both ends fixed, and a timing belt 33 which extends substantially parallel to the carriage guide shaft 32 and is driven by the carriage motor 31.

The carriage 24 included in the moving object 2 is supported by a carriage guide shaft 32 so as to be able to reciprocate and is fixed to a part of the timing belt 33. The timing belt 33 is driven by the carriage motor 31, and thereby, the carriage 24 is guided by the carriage guide shaft 32 to reciprocate in the direction Y. Further, a head unit 20 including many nozzles is provided in a part of the moving object 2 facing the medium P. A control signal and the like are input to the head unit 20 via a cable 190. Then, the head unit 20 ejects ink which is an example of a liquid from the nozzles based on the control signal which is input.

The liquid ejecting apparatus 1 includes a transport mechanism 4 that transports the medium P on the platen 40 in the direction X. The transport mechanism 4 includes a transport motor 41 that is a drive source, and a transport roller 42 that is rotated by the transport motor 41 to transport the medium P in the direction X.

In the liquid ejecting apparatus 1 configured as described above, an image is formed on a surface of the medium P by ejecting ink from the head unit 20 at a timing when the medium P is transported by the transport mechanism 4.

2. Electrical Configuration of Liquid Ejecting Apparatus

FIG. 2 is a diagram illustrating an electrical configuration of the liquid ejecting apparatus 1. As illustrated in FIG. 2, the liquid ejecting apparatus 1 includes a control signal output circuit 100, a carriage motor driver 35, the carriage motor 31, a transport motor driver 45, the transport motor 41, a drive circuit 50, a first power supply circuit 90a, and a second power supply circuit 90b, an oscillation circuit 91, and a head unit 20.

The control signal output circuit 100 generates a plurality of control signals for controlling various configuration elements based on image data input from a host computer, and outputs the signals to the corresponding configuration elements. Specifically, the control signal output circuit 100 generates a control signal CTR1 and outputs the control signal CTR1 to the carriage motor driver 35. The carriage motor driver 35 drives the carriage motor 31 according to the input control signal CTR1. Thereby, movement of the carriage 24 in the direction Y is controlled. Further, the control signal output circuit 100 generates a control signal CTR2 and outputs the control signal CTR2 to the transport motor driver 45. The transport motor driver 45 drives the transport motor 41 according to the input control signal CTR2. Thereby, transport of the medium P in the direction X is controlled.

Further, the control signal output circuit 100 generates drive data signals DATA1 to DATA4 for controlling an operation of the drive circuit 50 and outputs the drive data signals to the drive circuit 50. Further, a state signal BUSY and an abnormality signal ERR are mutually propagated between the control signal output circuit 100 and the drive circuit 50. Further, the control signal output circuit 100 generates a clock signal SCK, a printing data signal SI1 to SI4, a latch signal LAT, and a change signal CH that are used for controlling an operation of the head unit 20, and outputs the generated signals to the head unit 20.

The first power supply circuit 90a generates a voltage signal VHV1 having a voltage value of, for example, DC 42 V. The first power supply circuit 90a outputs the voltage signal VHV1 to the drive circuit 50. The second power supply circuit 90b generates a voltage signal VDD having a voltage value of, for example, DC 3.3 V. The second power supply circuit 90b outputs the voltage signal VDD to the drive circuit 50. The voltage signals VHV1 and VDD may be used as drive voltages of respective sections included in the liquid ejecting apparatus 1. Further, the first power supply circuit 90a and the second power supply circuit 90b may generate and output a plurality of voltage signals having voltage values different from the voltage signal VHV1 having the above-described voltage value and the voltage signal VDD.

The oscillation circuit 91 generates a clock signal MCK and outputs the clock signal MCK to the drive circuit 50. Here, the oscillation circuit 91 may be provided independently of the control signal output circuit 100 as illustrated in FIG. 2 or may be provided inside the control signal output circuit 100. Furthermore, the clock signal MCK output from the oscillation circuit 91 may be supplied to respective sections included in the liquid ejecting apparatus 1 in addition to the drive circuit 50.

The drive circuit 50 generates drive signals COM1 to COM4 by amplifying signals having waveforms respectively defined by the drive data signals DATA1 to DATA4 to a voltage value based on the voltage signal VHV1, and outputs the drive signals to the head unit 20. Further, the drive circuit 50 generates reference voltage signals VBS1 and VBS3 and outputs the reference voltage signals to the head unit 20. Furthermore, the drive circuit 50 propagates the voltage signal VHV1 input from the first power supply circuit 90a, branches the voltage signal, and outputs the divided voltage signals as voltage signals VHV2-1 and VHV2-2.

The head unit 20 includes ejecting modules 21-1 to 21-4. The ejecting modules 21-1 to 21-4 receive the clock signals SCK, the printing data signals SI1 to SI4, the latch signal LAT, and the change signal CH, and receive the voltage signals VHV2-1 and VHV2-2, the drive signals COM1 to COM4, and the reference voltage signals VBS1 and VBS3 output from the drive circuit 50. The head unit 20 ejects a predetermined amount of ink at a desired timing based on input various signals.

Here, a specific example of configurations and electrical coupling of the drive circuit 50 and the head unit 20 will be described with reference to FIGS. 3A and 3B. FIGS. 3A and 3B are diagrams illustrating an example of the configurations and electrical coupling of the drive circuit 50 and the head unit 20.

As illustrated in FIG. 3A, the drive circuit 50 includes power supply voltage control circuits 70-1 and 70-2, drive control circuits 51-1 to 51-4, and fuses F1 and F2.

The voltage signal VHV1 is input to the power supply voltage control circuit 70-1 from the first power supply circuit 90a. The power supply voltage control circuit 70-1 switches whether or not to output the input voltage signal VHV1 as a voltage signal VHVa. The voltage signal VHVa output from the power supply voltage control circuit 70-1 is input to the fuse F1. The voltage signal VHVa input to the fuse F1 is output from the fuse F1 as the voltage signal VHV2-1. The voltage signal VHV2-1 is output to the head unit 20 after being branched by the drive circuit 50. Further, the voltage signals VHVa and VHV2-1 are also input to the drive control circuits 51-1 and 51-2.

Likewise, the voltage signal VHV1 is input to the power supply voltage control circuit 70-2 from the first power supply circuit 90a. The power supply voltage control circuit 70-2 switches whether or not to output the input voltage signal VHV1 as a voltage signal VHVb. The voltage signal VHVb output from the power supply voltage control circuit 70-2 is input to the fuse F2. The voltage signal VHVb input to the fuse F2 is output from the fuse F2 as the voltage signal VHV2-2. The voltage signal VHV2-2 is output to the head unit 20 after being branched by the drive circuit 50. Further, the voltage signals VHVb and VHV2-2 are also input to the drive control circuits 51-3 and 51-4.

The drive control circuit 51-1 receives the voltage signal VDD output from the second power supply circuit 90b, the clock signal MCK output from the oscillation circuit 91, and the drive data signal DATA1 output from the control signal output circuit 100 in addition to the voltage signals VHVa and VHV2-1 described above. The drive control circuit 51-1 generates and outputs the drive signal COM1 and the reference voltage signal VBS1 based on the voltage signals VHVa, VHV2-1, and VDD, the clock signal MCK, and the drive data signal DATA1 which are input. Furthermore, the drive control circuit 51-1 receives the abnormality signal ERR and the state signal BUSY, and generates and outputs an abnormality signal ERR1 indicating whether or not the drive control circuit 51-1 is abnormal and a state signal BUSY1 indicating an operation state. Further, the drive control circuit 51-1 outputs a VHV control signal VHV_CNT1 for controlling the power supply voltage control circuit 70-1.

The drive control circuit 51-2 receives the voltage signal VDD output from the second power supply circuit 90b, the clock signal MCK output from the oscillation circuit 91, and the drive data signal DATA2 output from the control signal output circuit 100 in addition to the voltage signals VHVa and VHV2-1 described above. The drive control circuit 51-2 generates and outputs the drive signal COM2 and the reference voltage signal VBS2 based on the voltage signals VHVa, VHV2-1, and VDD, the clock signal MCK, and the drive data signal DATA2 which are input. Furthermore, the drive control circuit 51-2 receives the abnormality signal ERR and the state signal BUSY, and generates and outputs an abnormality signal ERR2 indicating whether or not the drive control circuit 51-2 is abnormal and a state signal BUSY2 indicating an operation state. Further, the drive control circuit 51-2 outputs a VHV control signal VHV_CNT2 for controlling the power supply voltage control circuit 70-1.

The drive control circuit 51-3 receives the voltage signal VDD output from the second power supply circuit 90b, the clock signal MCK output from the oscillation circuit 91, and the drive data signal DATA3 output from the control signal output circuit 100 in addition to the voltage signals VHVb and VHV2-2 described above. The drive control circuit 51-3 generates and outputs the drive signal COM3 the reference voltage signal VBS3 based on the voltage signals VHVb, VHV2-2, and VDD, the clock signal MCK, and the drive data signal DATA3 which are input. Furthermore, the drive control circuit 51-3 receives the abnormality signal ERR and the state signal BUSY, and generates and outputs an abnormality signal ERR3 indicating whether or not the drive control circuit 51-3 is abnormal and a state signal BUSY3 indicating an operation state. Further, the drive control circuit 51-3 outputs a VHV control signal VHV_CNT3 for controlling the power supply voltage control circuit 70-2.

The drive control circuit 51-4 receives the voltage signal VDD output from the second power supply circuit 90b, the clock signal MCK output from the oscillation circuit 91, and the drive data signal DATA4 output from the control signal output circuit 100 in addition to the voltage signals VHVb and VHV2-2 described above. The drive control circuit 51-4 generates the drive signal COM4 and a reference voltage signal VBS4 based on the voltage signals VHVb, VHV2-2, and VDD, the clock signal MCK, and the drive data signal DATA4 which are input, and outputs the generated signals to the head unit 20. Furthermore, the drive control circuit 51-4 receives the abnormality signal ERR and the state signal BUSY, and outputs an abnormality signal ERR4 indicating whether or not the drive control circuit 51-4 is abnormal and a state signal BUSY4 indicating an operation state. Further, the drive control circuit 51-4 outputs a VHV control signal VHV_CNT4 for controlling the power supply voltage control circuit 70-2 and a VBS control signal VBS_CNT4 for controlling the VBS supply control circuit 80-2.

The head unit 20 includes ejecting modules 21-1 to 21-4.

The ejecting module 21-1 includes a drive signal selection control circuit 200-1 and a head 22-1. The ejecting module 21-1 receives the voltage signal VHV2-1, the drive signal COM1, the reference voltage signal VBS1, the clock signal SCK, the printing data signal SI1, the latch signal LAT, and the change signal CH. The drive signal selection control circuit 200-1 selects or deselects a signal waveform included in the drive signal COM1 at the timing defined by the clock signal SCK, the printing data signal SI1, the latch signal LAT and the change signal CH to generate a drive signal VOUT1 and outputs the generated drive signal to the head 22-1.

The head 22-1 includes a plurality of ejecting sections 600. Further, each ejecting section 600 includes a piezoelectric element 60. The drive signal VOUT1 output from the drive signal selection control circuit 200-1 is supplied to one end of the piezoelectric element 60, and the reference voltage signal VBS1 is supplied to the other end of the piezoelectric element 60. The piezoelectric element 60 is driven by a potential difference between the drive signal VOUT1 and the reference voltage signal VBS1. Thereby, ink is ejected from the corresponding ejecting section 600.

The ejecting module 21-2 includes a drive signal selection control circuit 200-2 and a head 22-2. The ejecting module 21-2 receives the voltage signal VHV2-1, the drive signal COM2, the reference voltage signal VBS1, the clock signal SCK, the printing data signal SI2, the latch signal LAT, and the change signal CH. The drive signal selection control circuit 200-2 selects or deselects a signal waveform included in the drive signal COM2 at the timing defined by the clock signal SCK, the printing data signal SI2, the latch signal LAT, and the change signal CH to generate a drive signal VOUT2 and outputs the generated drive signal to the head 22-2.

The head 22-2 includes a plurality of ejecting sections 600. Further, each ejecting section 600 includes a piezoelectric element 60. The drive signal VOUT2 output from the drive signal selection control circuit 200-2 is supplied to one end of the piezoelectric element 60, and the reference voltage signal VBS1 is supplied to the other end of the piezoelectric element 60. The piezoelectric element 60 is driven by a potential difference between the drive signal VOUT2 and the reference voltage signal VBS1. Thereby, ink is ejected from the corresponding ejecting section 600.

The ejecting module 21-3 includes a drive signal selection control circuit 200-3 and a head 22-3. The ejecting module 21-3 receives the voltage signal VHV2-2, the drive signal COM3, the reference voltage signal VBS3, the clock signal SCK, the printing data signal S13, the latch signal LAT, and the change signal CH. The drive signal selection control circuit 200-3 selects or deselects a signal waveform included in the drive signal COM3 at the timing defined by the clock signal SCK, the printing data signal S13, the latch signal LAT, and the change signal CH to generate a drive signal VOUT3 and outputs the generated drive signal to the head 22-3.

The head 22-3 includes a plurality of ejecting sections 600. Further, each ejecting section 600 includes a piezoelectric element 60. The drive signal VOUT3 output from the drive signal selection control circuit 200-3 is supplied to one end of the piezoelectric element 60, and the reference voltage signal VBS3 is supplied to the other end of the piezoelectric element 60. The piezoelectric element 60 is driven by a potential difference between the drive signal VOUT3 and the reference voltage signal VBS3. Thereby, ink is ejected from the corresponding ejecting section 600.

The ejecting module 21-4 includes a drive signal selection control circuit 200-4 and a head 22-4. The ejecting module 21-4 receives the voltage signal VHV2-2, the drive signal COM4, the reference voltage signal VBS3, the clock signal SCK, the printing data signal SI4, the latch signal LAT, and the change signal CH. The drive signal selection control circuit 200-4 selects or deselects a signal waveform included in the drive signal COM4 at the timing defined by the clock signal SCK, the printing data signal SI4, the latch signal LAT, and the change signal CH to generate a drive signal VOUT4 and outputs the generated drive signal to the head 22-4.

The head 22-4 includes a plurality of ejecting sections 600. Further, each ejecting section 600 includes a piezoelectric element 60. The drive signal VOUT4 output from the drive signal selection control circuit 200-4 is supplied to one end of the piezoelectric element 60, and the reference voltage signal VBS3 is supplied to the other end of the piezoelectric element 60. As the piezoelectric element 60 is driven by a potential difference between the drive signal VOUT4 and the reference voltage signal VBS3, ink is ejected from the corresponding ejecting section 600.

Here, any one of the plurality of piezoelectric elements 60 included in the head 22-1 is an example of a first drive element, any one of the plurality of piezoelectric elements 60 included in the head 22-2 is an example of a second drive element, any one of the plurality of piezoelectric elements 60 included in the head 22-3 is an example of a third drive element, and any one of the plurality of piezoelectric elements 60 included in the head 22-4 is an example of a fourth drive element. Further, the drive circuit 50 drives the plurality of piezoelectric elements 60 included in the heads 22-1 to 22-4. The head unit 20 that ejects ink as a liquid by driving the plurality of piezoelectric elements 60 included in the heads 22-1 to 22-4 is an example of a liquid ejecting head.

Here, the power supply voltage control circuits 70-1 and 70-2 have the same configuration, and in the following description, when it is not necessary to distinguish therebetween, the power supply voltage control circuits 70-1 and 70-2 are simply referred to as a power supply voltage control circuit 70. Likewise, the drive control circuits 51-1 to 51-4 have the same configuration, and in the following description, when it is not necessary to distinguish therebetween, the drive control circuits 51-1 to 51-4 are simply referred to as a drive control circuit 51. Likewise, the fuses F1 and F2 have the same configuration, and in the following description, when it is not necessary to distinguish therebetween, the fuses F1 and F2 are simply referred to as a fuse F. Likewise, the ejecting modules 21-1 to 21-4 have the same configuration, and in the following description, when it is not necessary to distinguish therebetween, the ejecting modules 21-1 to 21-4 are simply referred to as an ejecting module 21. Likewise, the drive signal selection control circuits 200-1 to 200-4 have the same configuration, and in the following description, when it is not necessary to distinguish therebetween, the drive signal selection control circuits 200-1 to 200-4 are simply referred to as a drive signal selection control circuit 200. Likewise, the heads 22-1 to 22-4 have the same configuration, and in the following description, when it is not necessary to distinguish therebetween, the heads 22-1 to 22-4 are simply referred to as a head 22.

It will be described that the power supply voltage control circuit 70 receives the voltage signal VHV1 and outputs a voltage signal VHVab corresponding to one of the voltage signals VHVa and VHVb. Further, the description will be made on the assumption that the fuse F receives the voltage signal VHVab and outputs the voltage signal VHV2. Further, description will be made on the assumption that the drive control circuit 51 receives a drive data signal DATA corresponding to either of the drive data signals DATA1 to DATA4 and outputs a VHV control signal VHV_CNT corresponding to either of the VHV control signals VHV_CNT1 to VHV_CNT4, an abnormality signal ERR corresponding to either of the abnormality signals ERR1 to ERR4, a state signal BUSY corresponding to either of the state signals BUSY1 to BUSY4, and a drive signal COM corresponding to either of the drive signals COM1 to COM4. Description will be made on the assumption that the drive signal selection control circuit 200 receives the voltage signal VHV2 and the drive signal COM which are described above, and the clock signal SCK, the printing data signal SI corresponding to either of the printing data signals SI1 to SI4, the latch signal LAT, and the change signal CH which are output from the control signal output circuit 100, and outputs a drive signal VOUT corresponding to either of the drive signals VOUT1 to VOUT4, and the head 22 receives the drive signal VOUT and the reference voltage signal VBS.

3. Configuration of Ejecting Section

Here, a configuration of the ejecting section 600 included in each of the heads 22-1 to 22-4 will be described with reference to FIG. 4. FIG. 4 is a cross-sectional view illustrating a schematic configuration of one ejecting section 600.

FIG. 4 is a view illustrating a schematic configuration of one of the plurality of ejecting sections 600. As illustrated in FIG. 4, the ejecting section 600 includes the piezoelectric element 60, a vibration plate 621, a cavity 631, and a nozzle 651.

The cavity 631 is filled with ink supplied from a reservoir 641. Further, Ink is introduced into the reservoir 641 from an ink cartridge (not illustrated) via a supply hole 661. That is, the cavity 631 is filled with the ink stored in the corresponding ink cartridge.

The vibration plate 621 is displaced by driving the piezoelectric element 60 provided on an upper surface in FIG. 4. As the vibration plate 621 is displaced, an internal volume of the cavity 631 filled with ink is increased or reduced. That is, the vibration plate 621 functions as a diaphragm that changes the internal volume of the cavity 631.

The nozzle 651 is an opening which is provided in a nozzle plate 632 and communicates with the cavity 631. As the internal volume of the cavity 631 changes, ink of an amount corresponding to the change of the internal volume is ejected from the nozzle 651.

The piezoelectric element 60 has a structure in which a piezoelectric body 601 is interposed between a pair of electrodes 611 and electrodes 612. In the piezoelectric body 601 having the structure, central portions of the electrodes 611 and 612 bend in the vertical direction together with the vibration plate 621 according to a potential difference between voltages supplied by the electrodes 611 and 612. Specifically, the drive signal VOUT is supplied to the electrode 611 of the piezoelectric element 60, and the corresponding reference voltage signal VBS is supplied to the electrode 612. If a voltage level of the drive signal VOUT supplied to the electrode 611 is increased, the corresponding piezoelectric element 60 bends upward, and if the voltage level of the drive signal VOUT supplied to the electrode 611 is decreased, the corresponding piezoelectric element 60 bends downward.

In the ejecting section 600 configured as described above, as the piezoelectric element 60 bends upward, the vibrating plate 621 is displaced and the internal volume of the cavity 631 is increased. As a result, ink is drawn in from the reservoir 641. Meanwhile, as the piezoelectric element 60 bends downward, the vibration plate 621 is displaced and the internal volume of the cavity 631 is reduced. As a result, the amount of ink corresponding to the degree of reduction is ejected from the nozzle 651.

The piezoelectric element 60 is not limited to the structure illustrated in FIG. 4, and the ejecting section 600 may have any structure as long as ink can be ejected as the piezoelectric element 60 is driven. Thus, the piezoelectric element 60 is not limited to the configuration of a bending vibration described above and may have, for example, a configuration of using a longitudinal vibration.

Here, the electrode 611 included in each of the plurality of piezoelectric elements 60 included in the head 22-1 is an example of a first terminal, and the electrode 612 is an example of a second terminal. Further, the electrode 611 included in each of the plurality of piezoelectric elements 60 included in the head 22-2 is an example of a third terminal, and the electrode 612 is an example of a fourth terminal. Further, the electrode 611 included in each of the plurality of piezoelectric elements 60 included in the head 22-3 is an example of a fifth terminal, and the electrode 612 is an example of a sixth terminal. Further, the electrode 611 included in each of the plurality of piezoelectric elements 60 included in the head 22-4 is an example of a seventh terminal, and the electrode 612 is an example of an eighth terminal.

4. Configuration and Operation of Print Head

Next, a configuration and an operation of the ejecting module 21 included in the head unit 20 will be described. In describing the configuration and operation of the ejecting module 21, an example of a waveform of the drive signal COM input to the ejecting module 21 will be first described with reference to FIG. 5. After that, a configuration and an operation of the drive signal selection control circuit 200 included in the ejecting module 21 will be described with reference to FIGS. 6 to 9.

FIG. 5 is a diagram illustrating an example of the waveform of the drive signal COM. FIG. 5 illustrates a period T1 from a rise of the latch signal LAT to a rise of the change signal CH, a period T2 from the period T1 to a next rise of the change signal CH, and a period T3 from the period T2 to a rise of the latch signal LAT. A period Ta configured by the periods T1, T2, and T3 corresponds to a printing cycle for forming new dots on the medium P. That is, as illustrated in FIG. 5, the latch signal LAT defines the printing cycle in which a new dot is formed on the medium P, and the change signal CH defines a switch timing of a waveform included in the drive signal COM.

As illustrated in FIG. 5, the drive signal COM includes a trapezoidal waveform Adp in the period T1. When the trapezoidal waveform Adp is supplied to the piezoelectric element 60, a predetermined amount, specifically, a medium amount of ink is ejected from the corresponding ejecting section 600. Further, the drive signal COM includes a trapezoidal waveform Bdp in the period T2. When the trapezoidal waveform Bdp is supplied to the piezoelectric element 60, a small amount of ink less than the predetermined amount is ejected from the corresponding ejecting section 600. Further, the drive signal COM includes a trapezoidal waveform Cdp in the period T3. When the trapezoidal waveform Cdp is supplied to the piezoelectric element 60, the piezoelectric element 60 is driven to such an extent that ink is not ejected from the corresponding ejecting section 600. Thus, when the trapezoidal waveform Cdp is supplied to the piezoelectric element 60, no dot is formed on the medium P. The trapezoidal waveform Cdp performs micro-vibration of ink near a nozzle opening of the ejecting section 600 to prevent viscosity of the ink from increasing. In the following description, driving the piezoelectric element 60 to such an extent that the ink is not ejected from the ejecting section 600 in order to prevent the viscosity of the ink from increasing is referred to as “micro vibration”.

Here, a voltage value at a start timing and a voltage value at an end timing of each of the trapezoidal waveform Adp, the trapezoidal waveform Bdp, and the trapezoidal waveform Cdp are common as the voltage Vc. That is, the trapezoidal waveforms Adp, Bdp, and Cdp are waveforms whose voltage values start at the voltage Vc and end at the voltage Vc. As described above, the drive circuit 50 outputs the drive signal COM having a waveform in which the trapezoidal waveforms Adp, Bdp, and Cdp are continuous in the period Ta. The waveform of the drive signal COM illustrated in FIG. 5 is an example, and the present disclosure is not limited to this. Further, the drive signals COM1 to COM4 may have different waveforms from each other.

FIG. 6 is a diagram illustrating an electrical configuration of the drive signal selection control circuit 200. The drive signal selection control circuit 200 switches whether or not to select the trapezoidal waveforms Adp, Bdp, and Cdp included in the drive signal COM in each of the periods T1, T2, and T3, thereby, generating and outputting the drive signal VOUT to be supplied to the piezoelectric element 60 in the period Ta. As illustrated in FIG. 6, the drive signal selection control circuit 200 includes a selection control circuit 210 and a plurality of selection circuits 230.

The selection control circuit 210 is supplied with the clock signal SCK, the printing data signal SI, the latch signal LAT, the change signal CH, and the voltage signal VHV2. In the selection control circuit 210, a set of a shift register 212 (S/R), a latch circuit 214, and a decoder 216 is provided to correspond to each of the ejecting sections 600. That is, the ejecting module 21 is provided with the same number of sets of the shift register 212, the latch circuit 214, and the decoder 216 as a total number n of the ejecting sections 600.

The shift register 212 temporarily holds the 2-bit printing data [SIH, SIL] included in the printing data signal SI for each corresponding ejecting section 600. Specifically, the shift registers 212 of multiple stages corresponding to the ejecting sections 600 are cascade-coupled to each other, and the printing data signal SI supplied in serial is sequentially transferred to the subsequent stage according to the clock signal SCK. In FIG. 6, in order to distinguish between the shift registers 212, a first stage, a second stage, . . . , and an nth stage are described in order from an upstream to which the printing data signal SI is supplied.

Each of the n latch circuits 214 latches the printing data [SIH, SIL] held by the corresponding shift register 212 at a rising edge of the latch signal LAT. Each of the n decoders 216 decodes the 2-bit printing data [SIH, SIL] latched by the corresponding latch circuit 214, generates the selection signal S, and supplies the selection signal S to the selection circuit 230.

The selection circuits 230 are provided to correspond to the respective ejecting sections 600. That is, the number of selection circuits 230 included in one ejecting module 21 is n, which is the same as the total number of the ejecting sections 600 included in the ejecting module 21. The selection circuit 230 controls supply of the drive signal COM to the piezoelectric element 60 based on the selection signal S supplied from the decoder 216.

FIG. 7 is a diagram illustrating an electrical configuration of the selection circuit 230 corresponding to one ejecting section 600. As illustrated in FIG. 7, the selection circuit 230 includes an inverter 232 and a transfer gate 234. Further, the transfer gate 234 includes a transistor 235 that is an NMOS transistor and a transistor 236 that is a PMOS transistor.

The selection signal S is supplied from the decoder 216 to a gate terminal of the transistor 235. The selection signal S is logically inverted by the inverter 232 and is also supplied to a gate terminal of the transistor 236. A drain terminal of the transistor 235 and a source terminal of the transistor 236 are coupled to a terminal TG-In which is one end of the transfer gate 234. The drive signal COM is input to the terminal TG-In of the transfer gate 234. As the transistors 235 and 236 are turned on or off according to the selection signal S, the drive signal VOUT is output from a terminal TG-Out which is the other end of the transfer gate 234 to which a source terminal of the transistor 235 and a drain terminal of the transistor 236 are commonly coupled. The terminal TG-Out of the transfer gate 234 from which the drive signal VOUT is output is electrically coupled to an electrode 611, which will be described below, of the piezoelectric element 60.

Next, the decoding content of the decoder 216 will be described with reference to FIG. 8FIG. 8 is a diagram illustrating the decoding content in the decoder 216. The decoder 216 receives the 2-bit printing data [SIH, SIL], the latch signal LAT, and the change signal CH. For example, when the printing data [SIH, SIL] is [1, 0] defining a “medium dot”, the decoder 216 outputs the selection signal S having H, L, and L levels in the periods T1, T2, and T3. Here, the logic level of the selection signal S is level-shifted to a high amplitude logic based on the voltage signal VHV2 by a level shifter (not illustrated).

FIG. 9 is a diagram illustrating an operation of the drive signal selection control circuit 200. As illustrated in FIG. 9, the printing data [SIH, SIL] included in the printing data signal SI are serially supplied to the drive signal selection control circuit 200 in synchronization with the clock signal SCK, and are sequentially transferred the shift register 212 corresponding to the ejecting section 600. If supply of the clock signal SCK is stopped, the printing data [SIH, SIL] corresponding to the ejecting section 600 is held in each of the shift registers 212. The printing data signal SI is supplied in the order corresponding to a last nth stage ejecting section 600, . . . , a second stage ejecting section 600, and a first stage ejecting section 600 in the shift register 212.

If the latch signal LAT rises, each of the latch circuits 214 simultaneously latches the printing data [SIH, SIL] held in the corresponding shift register 212. LT1, LT2, . . . , LTn illustrated in FIG. 9 indicate the printing data [SIH, SIL] latched by the latch circuits 214 corresponding to the first stage shift registers 212, the second stage shift registers 212, . . . , the nth stage shift registers 212.

The decoder 216 outputs the selection signal S having a logic level according to the contents illustrated in FIG. 8 in each of the periods T1, T2, and T3 according to the dots size defined by the latched printing data [SIH, SIL].

When the printing data [SIH, SIL] is [1, 1], the selection circuit 230 selects the trapezoidal waveform Adp in the period T1, selects the trapezoidal waveform Bdp in the period T2, and does not select the trapezoidal waveform Cdp in the period T3, according to the selection signal S. As a result, the drive signal VOUT corresponding to the large dot illustrated in FIG. 9 is generated. Thus, the ejecting section 600 ejects a medium amount of ink and a small amount of ink. The large dot is formed on the medium P by combining ink on the medium P. Further, when the printing data [SIH, SIL] is [1, 0], the selection circuit 230 selects the trapezoidal waveform Adp in the period T1, does not select the trapezoidal waveform Bdp in the period T2, and does not select the trapezoidal waveform Cdp in the period T3, according to the selection signal S. As a result, the drive signal VOUT corresponding to a medium dot illustrated in FIG. 9 is generated. Thus, the ejecting section 600 ejects a medium amount of ink. Thus, the medium dot is formed on the medium P. Further, when the printing data [SIH, SIL] is [0, 1], the selection circuit 230 does not select the trapezoidal waveform Adp in the period T1, selects the trapezoidal waveform Bdp in the period T2, and does not select the trapezoidal waveform Cdp in the period T3, according to the selection signal S. As a result, the drive signal VOUT corresponding to the small dot illustrated in FIG. 9 is generated. Thus, a small amount of ink is ejected from the ejecting section 600. Thus, the small dot is formed on the medium P. When the printing data [SIH, SIL] is [0, 0], the selection circuit 230 does not select the trapezoidal waveform Adp in the period T1, does not select the trapezoidal waveform Bdp in the period T2, and select the trapezoidal waveform Cdp in the period T3, according to the selection signal S. As a result, the drive signal VOUT corresponding to the micro-vibration illustrated in FIG. 9 is generated. Thus, ink is not ejected from the ejecting section 600, and the micro-vibration is generated.

5. Configuration and Operation of Drive Circuit

Next, a configuration and an operation of the drive circuit 50 will be described. As illustrated in FIG. 3A, the drive circuit 50 includes the power supply voltage control circuits 70-1 and 70-2, the drive control circuits 51-1 to 51-4, and the fuses F1 and F2.

Here, as shown in FIGS. 3A and 3B, the drive signal COM1 output from the drive control circuit 51-1 is supplied to the electrode 611 of the piezoelectric element 60 included in the head 22-1 via the drive signal selection control circuit 200-1 as the drive signal VOUT1. The piezoelectric element 60 included in the head 22-1 is driven based on the drive signal VOUT1 to be supplied. That is, the drive control circuit 51-1 is electrically coupled to the electrode 611 of the piezoelectric element 60 included in the head 22-1 via the drive signal selection control circuit 200-1 and outputs the drive signal COM1 for driving the piezoelectric element 60 included in the head 22-1. The drive control circuit 51-1 is an example of a first drive signal output circuit, and the drive signal COM1 output by the drive control circuit 51-1 is an example of a first drive signal. Further, the drive signal VOUT1 is generated by selecting or deselecting the trapezoidal waveforms Adp, Bdp, and Cdp included in the drive signal COM1. Thus, it can be said that the drive signal VOUT1 is also an example of the first drive signal.

Likewise, the drive signal COM2 output from the drive control circuit 51-2 is supplied to the electrode 611 of the piezoelectric element 60 included in the head 22-2 via the drive signal selection control circuit 200-2 as the drive signal VOUT2. The piezoelectric element 60 included in the head 22-2 is driven based on the drive signal VOUT2 to be supplied. That is, the drive control circuit 51-2 is electrically coupled to the electrode 611 of the piezoelectric element 60 included in the head 22-2 via the drive signal selection control circuit 200-2, and outputs the drive signal COM2 for driving the piezoelectric element 60 included in the head 22-2. The drive control circuit 51-2 is an example of a second drive signal output circuit, and the drive signal COM2 output by the drive control circuit 51-2 is an example of a second drive signal. Further, the drive signal VOUT2 is generated by selecting or deselecting the trapezoidal waveforms Adp, Bdp, and Cdp included in the drive signal COM2. Thus, it can be said that the drive signal VOUT2 is also an example of the second drive signal.

Likewise, the drive signal COM3 output from the drive control circuit 51-3 is supplied to the electrode 611 of the piezoelectric element 60 included in the head 22-3 via the drive signal selection control circuit 200-3 as the drive signal VOUT3. The piezoelectric element 60 included in the head 22-3 is driven based on the drive signal VOUT3 to be supplied. That is, the drive control circuit 51-3 is electrically coupled to the electrode 611 of the piezoelectric element 60 included in the head 22-3 via the drive signal selection control circuit 200-3, and outputs the drive signal COM3 for driving the piezoelectric element 60 included in the head 22-3. The drive control circuit 51-3 is an example of a third drive signal output circuit, and the drive signal COM3 output by the drive control circuit 51-3 is an example of a third drive signal. The drive signal VOUT3 is generated by selecting or deselecting the trapezoidal waveforms Adp, Bdp, and Cdp included in the drive signal COM3. Thus, it can be said that the drive signal VOUT3 is also an example of the third drive signal.

Likewise, the drive signal COM4 output from the drive control circuit 51-4 is supplied to the electrode 611 of the piezoelectric element 60 included in the head 22-4 via the drive signal selection control circuit 200-4 as the drive signal VOUT4. The piezoelectric element 60 included in the head 22-4 is driven based on the drive signal VOUT4 to be supplied. That is, the drive control circuit 51-4 is electrically coupled to the electrode 611 of the piezoelectric element 60 included in the head 22-4 via the drive signal selection control circuit 200-4, and outputs the drive signal COM4 for driving the piezoelectric element 60 included in the head 22-4. The drive control circuit 51-4 is an example of a fourth drive signal output circuit, and the drive signal COM4 output by the drive control circuit 51-4 is an example of a fourth drive signal. The drive signal VOUT4 is generated by selecting or deselecting the trapezoidal waveforms Adp, Bdp, and Cdp included in the drive signal COM4. Thus, it can be said that the drive signal VOUT4 is also an example of the fourth drive signal.

5.1. Configuration and Operation of Power Supply Voltage Control Circuit

FIG. 10 is a diagram illustrating the configuration of the power supply voltage control circuit 70. As illustrated in FIG. 10, the power supply voltage control circuit 70 includes a power supply voltage blocking circuit 71, a power supply voltage discharging circuit 72, and an inrush current reduction circuit 73. The voltage signal VHV1 input to the power supply voltage control circuit 70 is input to the power supply voltage blocking circuit 71. The power supply voltage blocking circuit 71 controls whether or not to supply the input voltage signal VHV1 to the inrush current reduction circuit 73 as a voltage signal VHV1a. The inrush current reduction circuit 73 reduces an inrush current generated when supply of the voltage signal VHV1a is started, in a state where the supply of the voltage signal VHV1a is blocked by the power supply voltage blocking circuit 71. In other words, the inrush current reduction circuit 73 reduces a possibility of generating an inrush current of a large current based on the voltage signal VHV1a output from the power supply voltage control circuit 70. The power supply voltage discharging circuit 72 is electrically coupled to the power supply voltage blocking circuit 71 and the inrush current reduction circuit 73 and is electrically coupled to a wire through which the voltage signal VHV1a propagates. The power supply voltage discharging circuit 72 controls release of electric charges stored in a path to which the voltage signal VHV1a output from the power supply voltage blocking circuit 71 is supplied.

Specific examples of configurations of the power supply voltage blocking circuit 71, the power supply voltage discharging circuit 72, and the inrush current reduction circuit 73 included in the power supply voltage control circuit 70 will be described with reference to FIGS. 11 and 12. FIG. 11 is a diagram illustrating the example of the configuration of the power supply voltage blocking circuit 71 and the power supply voltage discharging circuit 72. As illustrated in FIG. 11, the power supply voltage blocking circuit 71 includes transistors 711 and 712, resistors 713 and 714, and a capacitor 715. Here, description will be made on the assumption that the transistor 711 is a PMOS transistor and the transistor 712 is an NMOS transistor.

The voltage signal VHV1 is input to a source terminal of the transistor 711. As conduction between a source terminal and a drain terminal of the transistor 711 is enabled, the voltage signal VHV1 is output from the drain terminal of the transistor 711 as the voltage signal VHV1a. In other words, the power supply voltage control circuit 70 switches conduction or non-conduction between the source terminal and the drain terminal of the transistor 711, thereby, switching whether or not to output the voltage signal VHV1 as the voltage signal VHV1a. A gate terminal of the transistor 711 is electrically coupled to one end of the resistor 713, one end of the resistor 714, and one end of the capacitor 715.

The voltage signal VHV1 is input to the other end of the resistor 713 and the other end of the capacitor 715. That is, the resistor 713 and the capacitor 715 are provided in parallel with the transistor 711 between the source terminal and the gate terminal of the transistor 711. The other end of the resistor 714 is electrically coupled to a drain terminal of the transistor 712. A ground potential is supplied to a source terminal of the transistor 712. Further, the VHV control signal VHV_CNT is input from the drive control circuit 51 to a gate terminal of the transistor 712.

When an VHV control signal VHV_CNT of an H level is input to the power supply voltage blocking circuit 71 configured as described above, the transistor 712 is turned on. As the transistor 712 is turned on, the transistor 711 is turned on. As a result, conduction between the source terminal and the drain terminal of the transistor 711 is enabled. Thus, the voltage signal VHV1 is output as the voltage signal VHV1a. Meanwhile, when the VHV control signal VHV_CNT of an L level is input to the power supply voltage blocking circuit 71, the transistor 712 is turned off. When the transistor 712 is turned off, the transistor 711 is turned off. As a result, conduction between the source terminal and the drain terminal of the transistor 711 is disabled. Thus, the voltage signal VHV1 is not output as the voltage signal VHV1a. As described above, the power supply voltage blocking circuit 71 switches whether or not to output the voltage signal VHV1 as the voltage signal VHV1a based on a logic level of the VHV control signal VHV_CNT.

The power supply voltage discharging circuit 72 includes transistors 721 and 722, resistors 723 and 724, and a capacitor 725. Here, description will be made on the assumption that both the transistors 721 and 722 are NMOS transistors.

One end of the resistor 723 is electrically coupled to a wire through which the voltage signal VHV1a is propagated, and the other end of the resistor 723 is electrically coupled to a drain terminal of the transistor 721. The ground potential is supplied to a source terminal of the transistor 721. A gate terminal of the transistor 721 is electrically coupled to one end of the resistor 724, one end of the capacitor 725, and a drain terminal of the transistor 722. The other end of the resistor 724 is supplied to the voltage signal VDD. The ground potential is supplied to the other end of the capacitor 725 and a source terminal of the transistor 722. The VHV control signal VHV_CNT is input to a gate terminal of the transistor 722.

The power supply voltage discharging circuit 72 configured as described above is electrically coupled to a wire that electrically couples the power supply voltage blocking circuit 71 to the inrush current reduction circuit 73. The power supply voltage discharging circuit 72 controls release of stored electric charges based on the voltage signal VHV1a according to a logic level of the VHV control signal VHV_CNT. Specifically, when the VHV control signal VHV_CNT of an H level is input to the power supply voltage discharging circuit 72, the transistor 722 is turned on. As the transistor 722 is turned on, the transistor 721 is turned off. Thus, a path through which the voltage signal VHV1a is propagated and a path through which the ground potential is supplied are controlled to be non-conductive by the transistor 721. As a result, the power supply voltage discharging circuit 72 does not release electric charges based on the voltage signal VHV1a. Meanwhile, when the VHV control signal VHV_CNT of an L level is input to the power supply voltage discharging circuit 72, the transistor 722 is turned off. As the transistor 722 is turned off, the voltage signal VDD is supplied to the gate terminal of the transistor 721. Thus, the transistor 721 is turned on. Thereby, the path through which the voltage signal VHV1a is propagated and the path through which the ground potential is supplied are electrically coupled to each other via the resistor 723. Thereby, the power supply voltage discharging circuit 72 releases the electric charge stored in the path through which the voltage signal VHV1a is propagated.

As described above, the power supply voltage blocking circuit 71 and the power supply voltage discharging circuit 72 switches whether to output the voltage signal VHV1 to the inrush current reduction circuit 73 as the voltage signal VHV1a based on the logic level of the VHV control signal VHV_CNT or to release the electric charges stored in the path through which the voltage signal VHV1a is propagated.

FIG. 12 is a diagram illustrating a configuration of the inrush current reduction circuit 73. As illustrated in FIG. 12, the inrush current reduction circuit 73 includes transistors 731 and 732, resistors 733, 734, 735, 736, and 737, a capacitor 738, and a constant voltage diode 739. Here, description will be made on the assumption that the transistor 731 is a PMOS transistor and the transistor 732 is an N-type bipolar transistor.

The voltage signal VHV1a is input to a source terminal of the transistor 731. As a drain terminal and the source terminal of the transistor 731 are controlled to be conductive, the voltage signal VHV1a is output from the drain terminal of the transistor 731 as the voltage signal VHVab. A gate terminal of the transistor 731 is electrically coupled to one end of the resistor 734 and one end of the resistor 735. The voltage signal VHV1a is input to the other end of the resistor 734. That is, the resistor 734 is provided in parallel with the transistor 731 between the source terminal and the gate terminal of the transistor 731. The resistor 733 has one end electrically coupled to the source terminal of the transistor 731 and the other end electrically coupled to the drain terminal of the transistor 731.

The other end of the resistor 735 is electrically coupled to a collector terminal of the transistor 732. A ground potential is supplied to an emitter terminal of the transistor 732. A base terminal of the transistor 732 is electrically coupled to one end of the resistor 736, one end of the resistor 737, and one end of the capacitor 738. The ground potential is supplied to the other end of the resistor 737 and the other end of the capacitor 738. That is, the resistor 737 and the capacitor 738 are provided between the base terminal and the emitter terminal of the transistor 732 in parallel with the transistor 732.

The other end of the resistor 736 is electrically coupled to an anode terminal of the constant voltage diode 739. The voltage signal VHVa is input to a cathode terminal of the constant voltage diode 739.

The inrush current reduction circuit 73 configured as described above does not receive the voltage signal VHV1a, when supply of the voltage signal VHV1a is blocked by the power supply voltage blocking circuit 71. Thus, the inrush current reduction circuit 73 does not output the voltage signal VHVab. Since the voltage signal VHVab is not output, a potential of the anode terminal of the constant voltage diode 739 becomes the ground potential supplied through the resistor 737. Thus, the transistor 732 is turned off, and the transistor 731 is also turned off.

In a state where supply of the voltage signal VHV1a is blocked by the power supply voltage blocking circuit 71, when the supply of the voltage signal VHV1a is started, the voltage signal VHV1a is input to the inrush current reduction circuit 73. In this case, the transistor 731 is turned off, and thus, the voltage signal VHV1a is input to the drain terminal of the transistor 731 via the resistor 733 as the voltage signal VHVab. At this time, a current generated by the voltage signal VHV1a and the voltage signal VHVab is limited by the resistor 733. Thus, a possibility of generating an inrush current of a large current is reduced.

As a predetermined period elapses after input of the voltage signal VHV1a to the inrush current reduction circuit 73 starts, a voltage value of the voltage signal VHVab increases. When the voltage value of the voltage signal VHVab is greater than or equal to a predetermined value defined by the constant voltage diode 739, a voltage value of the anode terminal of the constant voltage diode 739 increases. After that, When the voltage value of the anode terminal of the constant voltage diode 739 exceeds a threshold voltage of the transistor 732, the transistor 732 is turned on. If the transistor 732 is turned on, the transistor 731 is turned on. As a result, conduction between the drain terminal and the source terminal of the transistor 731 is enabled, and the voltage signal VHV1a is output from the power supply voltage control circuit 70 via the transistor 731 as the voltage signal VHVab.

In the inrush current reduction circuit 73 configured as described above, in a state where the supply of the voltage signal VHV1a is blocked, immediately after the supply of the voltage signal VHV1a is started, the voltage signal VHV1a is propagated to the drain terminal of the transistor 731 via the resistor 733. Thereby, it is possible to reduce a possibility that an inrush current of a large current is generated. Further, as a voltage value of voltage signal VHVab is greater than or equal to a predetermined value defined by the constant voltage diode 739, the transistor 731 is turned on. Thereby, it is possible to reduce a power loss generated by the resistor 733.

The voltage signal VHVab output from the power supply voltage control circuit 70 is input to the drive control circuit 51, is input to the drive control circuit 51 via the fuse F1 as the voltage signal VHV2, and is output from the drive circuit 50 to the head unit 20.

5.2. Configuration and Operation of Drive Control Circuit

Next, a configuration and an operation of the drive control circuit 51 will be described with reference to FIG. 13. FIG. 13 is a diagram illustrating an example of the configuration of the drive control circuit 51. The drive control circuit 51 includes an integrated circuit 500, an amplification circuit 550, a demodulation circuit 560, and a feedback circuit 570.

The integrated circuit 500 includes an amplification control signal generation circuit 502, an internal voltage generation circuit 400, an oscillation circuit 410, a clock selection circuit 411, an abnormality detection circuit 430, a register control circuit 440, a constant voltage output circuit 420, a drive signal discharging circuit 450, a reference voltage signal output circuit 460, a VHV control signal output circuit 470, a state signal input/output circuit 480, and an abnormality signal input/output circuit 490.

The voltage signal VDD is supplied to the internal voltage generation circuit 400. The internal voltage generation circuit 400 generates a voltage signal GVDD having, for example, a voltage value of DC 7.5 V by boosting or dropping a voltage of the input voltage signal VDD. The voltage signal GVDD is input to various configurations of the integrated circuit 500 including a gate driver 540 which will be described below.

The amplification control signal generation circuit 502 generates amplification control signals Hgd and Lgd based on a data signal that defines a waveform of the drive signal COM included in the drive data signal DATA input from a terminal DATA-In. The amplification control signal generation circuit 502 includes a DAC interface (DAC_I/F: Digital to Analog Converter Interface) 510, a DAC section 520, a modulator 530, and the gate driver 540.

The drive data signal DATA supplied from the terminal DATA-In and the clock signal MCK supplied from the terminal MCK-In are input to the DAC interface 510. The DAC interface 510 integrates the drive data signal DATA based on the clock signal MCK, and generates, for example, 10-bit drive data dA that defines a waveform of the drive signal COM. The drive data dA is input to the DAC section 520. The DAC section 520 converts the drive data dA which is input into an original drive signal aA of an analog signal. The original drive signal aA is a target signal before the drive signal COM is amplified. The modulator 530 receives the original drive signal aA. The modulator 530 outputs a modulation signal Ms obtained by performing a pulse width modulation of the original drive signal aA. In other words, the modulator 530 modulates the original drive signal aA and outputs the modulation signal Ms. The gate driver 540 receives the voltage signals VHVab and GVDD, and the modulation signal Ms. The gate driver 540 amplifies the input modulation signal Ms based on the voltage signal GVDD and generates the amplification control signal Hgd that is level-shifted to a high amplitude logic based on the voltage signal VHVab, and the amplification control signal Lgd obtained by inverting a logic level of the input modulation signal Ms and amplifying the modulation signal MS based on the voltage signal GVDD. That is, the amplification control signal Hgd and the amplification control signal Lgd are exclusively at an H level.

Here, being exclusively at an H level includes that the amplification control signal Hgd and the amplification control signal Lgd are not at the H level at the same time. Thus, the gate driver 540 may control timing at which the amplification control signal Hgd and the amplification control signal Lgd go to the H level such that the amplification control signal Hgd and the amplification control signal Lgd do not go to the H level at the same time, and may include, for example, a timing controller.

The amplification control signal Hgd is output from the integrated circuit 500 via a terminal Hg-Out and is input to the amplification circuit 550. Likewise, the amplification control signal Lgd is output from the integrated circuit 500 via a terminal Lg-Out and is input to the amplification circuit 550. Here, the amplification control signal Hgd is obtained by level-shifting a logic level of the modulation signal Ms, and the amplification control signal Lgd is obtained by inverting the logic level of the modulation signal Ms. Thus, the amplification control signal Hgd and the amplification control signal Lgd also correspond to a modulation signal generated by the modulator 530 in a broad sense.

The amplification circuit 550 outputs an amplification modulation signal AMs by operating based on the amplification control signals Hgd and Lgd. In other words, the amplification circuit 550 amplifies the modulation signal Ms and outputs the amplification modulation signal AMs. The amplification circuit 550 includes transistors 551 and 552. Each of the transistors 551 and 552 is, for example, an N-channel field effect transistor (FET).

The voltage signal VHVab is supplied to a drain terminal of the transistor 551. The amplification control signal Hgd is supplied to a gate terminal of the transistor 551 via the terminal Hg-Out. A source terminal of the transistor 551 is electrically coupled to a drain terminal of the transistor 552. The amplification control signal Lgd is supplied to a gate terminal of the transistor 552 via the terminal Lg-Out. A ground potential is supplied to a source terminal of the transistor 552. The transistor 551 coupled as described above operates according to the amplification control signal Hgd, and the transistor 552 operates according to the amplification control signal Lgd that is exclusively at an H level with respect to the amplification control signal Hgd. That is, the transistors 551 and 552 are exclusively turned on. Thereby, the amplification modulation signal AMs obtained by amplifying the modulation signal Ms based on the voltage signal VHV is generated at a coupling point between the source terminal of the transistor 551 and the drain terminal of the transistor 552.

The amplification modulation signal AMs generated by the amplification circuit 550 is input to a demodulation circuit 560. The demodulation circuit 560 includes a coil 561 and a capacitor 562. One end of the coil 561 is electrically coupled to the source terminal of the transistor 551 and the drain terminal of the transistor 552. Further, the other end of the coil 561 is electrically coupled to one end of the capacitor 562. The other end of the capacitor 562 receives the ground potential. That is, the coil 561 and the capacitor 562 configure a low-pass filter. As the amplification modulation signal AMs is supplied to the demodulation circuit 560, the amplification modulation signal AMs is demodulated, and the drive signal COM is generated. That is, the demodulation circuit 560 generates the drive signal COM by demodulating the amplification modulation signal AMs and outputs the generated drive signal COM from a terminal COM-Out.

Further, the drive signal COM generated by the demodulation circuit 560 is fed back to the modulator 530 via the feedback circuit 570. In other words, the feedback circuit 570 feeds back the drive signal COM to the modulator 530. The feedback circuit 570 includes resistors 571 and 572. One end of the resistor 571 is electrically coupled to the other end of the coil 561, and the other end of the resistor 571 is electrically coupled to one end of the resistor 572. The other end of the resistor 572 receives the voltage signal VHV2. The other end of the resistor 571 and one end of the resistor 572 are electrically coupled to the modulator 530 via a terminal Com-Dis. That is, the drive signal COM is pulled up by the voltage signal VHV2 via the feedback circuit 570 and is fed back to the modulator 530.

As described above, the amplification control signal generation circuit 502, the amplification circuit 550, the demodulation circuit 560, and the feedback circuit 570 included in the integrated circuit 500 generate the drive signal COM for driving the piezoelectric element 60 based on the drive data signal DATA. The generated drive signal COM is supplied to the electrode 611 of the piezoelectric element 60. Here, the drive signal output circuit 501 outputs a signal, which includes the trapezoidal waveforms Adp, Bdp, and Cdp illustrated in FIG. 5 as a drive signal COM, for driving the piezoelectric element 60, and can also output a signal having a constant voltage value as the drive signal COM when the drive data signal DATA indicating a constant voltage value is supplied.

As described above, a configuration including the amplification control signal generation circuit 502, the amplification circuit 550, the demodulation circuit 560, and the feedback circuit 570 corresponds to the drive signal output circuit 501. The terminal COM-Out from which the drive signal COM generated by the drive signal output circuit 501 is output is electrically coupled to the terminal TG-In of the selection circuit 230 illustrated in FIG. 7.

The oscillation circuit 410 generates and outputs a clock signal LCK that defines an operation timing of the integrated circuit 500. The clock signal LCK is input to the clock selection circuit 411 and the abnormality detection circuit 430.

The clock signals MCK and LCK and a clock selection signal CSW are input to the clock selection circuit 411. The clock selection circuit 411 switches whether to output the clock signal MCK as a clock signal RCK to a register control circuit 440 based on a logic level of the clock selection signal CSW or to output the clock signal LCK to the register control circuit 440 as the clock signal RCK. In the present embodiment, description will be made on the assumption that the clock selection circuit 411 outputs the clock signal MCK to the register control circuit 440 as the clock signal RCK when the clock selection signal CSW is at an H level and outputs the clock signal LCK to the register control circuit 440 as the clock signal RCK when the clock selection signal CSW is at an L level.

The abnormality detection circuit 430 includes an oscillation abnormality detector 431, an operation abnormality detector 432, and a power supply voltage abnormality detector 433.

The clock signal LCK output from the oscillation circuit 410 is input to the oscillation abnormality detector 431. The oscillation abnormality detector 431 detects whether or not the input clock signal LCK is normal, and outputs the clock selection signal CSW and an error signal NES of a logic level based on the detection result. For example, the oscillation abnormality detector 431 detects at least one of a frequency and a voltage value of the clock signal LCK. When it is detected that at least one of the frequency and the voltage value of the clock signal LCK is abnormal, the oscillation abnormality detector 431 outputs the clock selection signal CSW and the error signal NES indicating abnormality to each of the clock selection circuit 411 and the register control circuits 440. Further, when both the frequency and the voltage value of the clock signal LCK are normal, the oscillation abnormality detector 431 outputs the clock selection signal CSW and the error signal NES indicating that the clock signal LCK is normal to each of the clock selection circuit 411 and the register control circuit 440.

An operation state signal ASS indicating operation states of various configuration elements of the drive control circuit 51 is input to the operation abnormality detector 432. The operation abnormality detector 432 detects whether or not various configuration elements of the drive control circuit 51 normally operate based on the input operation state signal ASS. In the present embodiment, when any of the various configurations of the drive control circuit 51 is abnormal, the operation state signal ASS indicating the abnormality is input to the operation abnormality detector 432. When the operation state signal ASS indicating the abnormality is input to the operation abnormality detector 432, the operation abnormality detector 432 outputs the error signal NES indicating the abnormality to the register control circuit 440.

The voltage signal VHV2 which is output from the drive circuit 50 and is supplied to the ejecting module 21 is input to the power supply voltage abnormality detector 433. The power supply voltage abnormality detector 433 detects a voltage value of the voltage signal VHV2. The power supply voltage abnormality detector 433 detects whether or not the voltage value of the voltage signal VHV2 supplied to the ejecting module 21 is normal based on the voltage value of the voltage signal VHV2. When it is determined that the voltage value of the voltage signal VHV2 supplied to the ejecting module 21 is abnormal, the power supply voltage abnormality detector 433 outputs an error signal FES indicating abnormality to the register control circuit 440.

Here, the power supply voltage abnormality detection section 433 may detect a voltage value of the reference voltage signal VBS1 and detect whether or not the voltage value of the reference voltage signal VBS1 is normal. In that case, when it is determined that the voltage value of the reference voltage signal VBS1 is abnormal, the power supply voltage abnormality detector 433 may output the error signal FES indicating the abnormality to the register control circuit 440.

The register control circuit 440 includes a sequence register 441, a state register 442, and a register controller 443. The sequence register 441 and the state register 442 hold operation information and the like input as the drive data signal DATA in synchronization with the clock signal MCK. The register controller 443 generates control signals CNT1 to CNT5 based on the information held in the sequence register 441 and the state register 442 in synchronization with the clock signal RCK, and outputs the generated signals to the corresponding configurations.

The control signal CNT1 is input to the drive signal discharging circuit 450. The drive signal discharging circuit 450 controls whether or not to release the stored electric charges based on the drive signal COM output from the demodulation circuit 560 via the feedback circuit 570. The drive signal discharging circuit 450 is electrically coupled to a propagation path through which the drive signal COM output from the demodulation circuit 560 is propagated, via the feedback circuit 570 and the terminal Com-Dis.

FIG. 14 is a diagram illustrating an example of a configuration of the drive signal discharging circuit 450. The drive signal discharging circuit 450 includes a resistor 451, a transistor 452, and an inverter 453. Description will be made on the assumption that the transistor 452 is an NMOS transistor.

One end of the resistor 451 is electrically coupled to the terminal Com-Dis. The other end of the resistor 451 is electrically coupled to a drain terminal of the transistor 452. A ground potential is supplied to a source terminal of the transistor 452. The control signal CNT1 is input to a gate terminal of the transistor 452 via the inverter 453. When the control signal CNT1 of an H level is input to the drive signal discharging circuit 450 configured as described above, the transistor 452 is turned off. Thus, the drive signal discharging circuit 450 does not release the electric charges stored in a propagation path through which the drive signal COM is propagated. Meanwhile, when the control signal CNT1 of an L level is input to the drive signal discharging circuit 450, the transistor 452 is turned on. Thus, the drive signal discharging circuit 450 releases the electric charges stored in the propagation path through which the drive signal COM is propagated via the feedback circuit 570, via the resistor 451 and the transistor 452. As described above, the drive signal discharging circuit 450 controls whether or not to release the electric charges stored in the propagation path through which the drive signal COM is supplied to the ejecting module 21, based on the control signal CNT1.

The control signal CNT2 is input to the reference voltage signal output circuit 460. The reference voltage signal output circuit 460 outputs the reference voltage signal VBS supplied to the electrode 612 of the piezoelectric element 60. That is, the reference voltage signal output circuit 460 is electrically coupled to the electrode 612 of the piezoelectric element 60 and outputs the reference voltage signal VBS which has a constant voltage value at the voltage Vbs and is supplied to the electrode 612 of the piezoelectric element 60.

FIG. 15 is a diagram illustrating a configuration of the reference voltage signal output circuit 460. The reference voltage signal output circuit 460 includes a comparator 461, transistors 462 and 463, resistors 464, 465, and 466, and an inverter 467. Description will be made on the assumption that the transistor 462 is a PMOS transistor and the transistor 463 is an NMOS transistor.

The reference voltage Vref is supplied to a negative input end of the comparator 461. Further, a positive input end of the comparator 461 is electrically coupled to one end of the resistor 464 and one end of the resistor 465. An output end of the comparator 461 is electrically coupled to a gate terminal of the transistor 462. The voltage signal GVDD is supplied to a source terminal of the transistor 462. A drain terminal of the transistor 462 is electrically coupled to the other end of the resistor 464, one end of the resistor 466, and a terminal VBS-Out from which the reference voltage signal VBS is output. The other end of the resistor 466 is electrically coupled to a drain terminal of the transistor 463. The control signal CNT2 is input to a gate terminal of the transistor 463 via the inverter 467. The ground potential is supplied to a source terminal of the transistor 463 and the other end of the resistor 465.

In the reference voltage signal output circuit 460 configured as described above, when a voltage value supplied to the positive input end of the comparator 461 is greater than a voltage value of the reference voltage Vref supplied to the negative input end of the comparator 461, the comparator 461 outputs a signal of an H level. At this time, the transistor 462 is turned off. Thus, the voltage signal GVDD is not supplied to the terminal VBS-Out. Meanwhile, when the voltage value supplied to the negative input end of the comparator 461 is less than the voltage value of the reference voltage Vref supplied to the negative input end of the comparator 461, the comparator 461 outputs a signal of an L level. At this time, the transistor 462 is turned on. Thus, the voltage signal GVDD is supplied to the terminal VBS-Out. That is, as the comparator 461 operates to make a voltage value obtained by dividing the reference voltage signal VBS by the resistors 464 and 465 be equal to the voltage value of the reference voltage Vref, the reference voltage signal output circuit 460 generates the reference voltage signal VBS having a constant voltage value at the voltage Vbs based on the voltage signal GVDD.

Further, the control signal CNT2 is input to the reference voltage signal output circuit 460. When the control signal CNT2 of an H level is input to the reference voltage signal output circuit 460, the transistor 463 is turned off. Thus, the terminal VBS-Out and a propagation path through which the ground potential is propagated are controlled to have a high impedance. As a result, the reference voltage signal VBS having a constant voltage value at the voltage Vbs is output from the terminal VBS-Out. Meanwhile, when the control signal CNT2 of an L level is input to the reference voltage signal output circuit 460, the transistor 463 is turned on. Thus, the ground potential is supplied to the terminal VBS-Out through the resistor 466 and the transistor 463. As a result, the reference voltage signal output circuit 460 outputs the reference voltage signal VBS which is constant at the ground potential. In other words, when the control signal CNT2 of an L level is input to the reference voltage signal output circuit 460, the reference voltage signal output circuit 460 stops outputting the reference voltage signal VBS and sets a voltage value of the terminal VBS-Out to the ground potential, and thereby, electric charges stored in the terminal VBS-Out are released.

The control signal CNT3 is input to the VHV control signal output circuit 470. The VHV control signal output circuit 470 outputs the VHV control signal VHV_CNT supplied to the power supply voltage control circuit 70.

FIG. 16 is a diagram illustrating a structure of the VHV control signal output circuit 470. The VHV control signal output circuit 470 includes a transistor 471 and a resistor 472. Description will be made on the assumption that the transistor 471 is a PMOS transistor.

The voltage signal GVDD is supplied to a source terminal of the transistor 471. A drain terminal of the transistor 471 is electrically coupled to one end of the resistor 472 and a terminal VHV_CNT-Out. The control signal CNT3 is input to a gate terminal of the transistor 471. The ground potential is supplied to the other end of the resistor 472. When the control signal CNT3 of an L level is input to the VHV control signal output circuit 470 configured as described above, the voltage signal GVDD is supplied to the terminal VHV_CNT-Out, and when the control signal CNT3 of an H level is input, the ground potential is supplied to the terminal VHV_CNT-Out via the resistor 472.

The VHV control signal VHV_CNT output from the VHV control signal output circuit 470 is input to the power supply voltage control circuit 70 as illustrated in FIG. 3A. The power supply voltage control circuit 70 switches whether or not to supply the voltage signal VHV1 to the ejecting module 21 as the voltage signal VHV2, based on a logic level of the input VHV control signal VHV_CNT.

The control signal CNT4 is input to the state signal input/output circuit 480. The state signal input/output circuit 480 outputs the state signal BUSY indicating an operation state of the drive control circuit 51 and also receives the state signal BUSY output from another configuration. Here, for example, another configuration may be any one of the drive control circuits 51-1 to 51-4 included in the liquid ejecting apparatus 1 or may be the control signal output circuit 100.

FIG. 17 is a diagram illustrating a configuration of the state signal input/output circuit 480. The state signal input/output circuit 480 includes a transistor 481, an inverter 482, and a resistor 483. Description will be made on the assumption that the transistor 481 is a PMOS transistor. Further, the inverter 482 functions as a COMS input terminal of the integrated circuit 500. That is, the state signal input/output circuit 480 outputs the state signal BUSY from the terminal BUSY-Out and inputs a signal input to a terminal BUSY-Out to the register control circuit 440, based on the control signal CNT4 output from the register control circuit 440. In FIG. 17, the control signal CNT4 output from the register control circuit 440 is illustrated as a control signal CNT4-out, and the control signal CNT4 input to the register control circuit 440 is illustrated as a control signal CNT4-in.

The voltage signal GVDD is supplied to a source terminal of the transistor 481. A drain terminal of the transistor 481 is coupled to an input end of the inverter 482, one end of the resistor 483, and a terminal BUSY-Out. Further, the control signal CNT4-out output from the register control circuit 440 is input to a gate terminal of the transistor 481. Further, the control signal CNT4-in is output from an output end of the inverter 482 to the register control circuit 440. The ground potential is supplied to the other end of the resistor 483. When the control signal CNT4 of an L level is input to the state signal input/output circuit 480 configured as described above, the voltage signal GVDD is supplied to the terminal BUSY-Out. That is, the state signal BUSY of an H level is output.

The control signal CNT5 is input to the abnormality signal input/output circuit 490. The abnormality signal input/output circuit 490 outputs the abnormality signal ERR indicating whether or not the drive control circuit 51 is abnormal, and receives the abnormality signal ERR output from another configuration. Here, for example, another configuration may be any one of the drive control circuits 51-1 to 51-4 included in the liquid ejecting apparatus 1 or may be the control signal output circuit 100.

FIG. 18 is a diagram illustrating a configuration of the abnormality signal input/output circuit 490. The abnormality signal input/output circuit 490 includes a transistor 491, an inverter 492, and a resistor 493. In the following description, the transistor 491 will be described as a PMOS transistor. Further, the inverter 492 functions as a COMS input terminal of the integrated circuit 500. That is, the abnormality signal input/output circuit 490 outputs the abnormality signal ERR from a terminal ERR-Out based on the control signal CNT5 output from the register control circuit 440, and inputs the signal input to the terminal ERR-Out to the register control circuit 440. In FIG. 18, the control signal CNT5 output from the register control circuit 440 is illustrated as a control signal CNT5-out, and the control signal CNT5 input to the register control circuit 440 is illustrated as a control signal CNT5-in.

The voltage signal GVDD is supplied to a source terminal of the transistor 491. A drain terminal of the transistor 491 is electrically coupled to an input end of the inverter 492, one end of the resistor 493, and the terminal ERR-Out. Further, the control signal CNT5-out output from the register control circuit 440 is input to a gate terminal of the transistor 491. The control signal CNT5-in is output to the register control circuit 440 from an output end of the inverter 492. Further, the ground potential is supplied to the other end of the resistor 493. When the control signal CNT5 of an L level is input to the abnormality signal input/output circuit 490 configured as described above, the voltage signal GVDD is supplied to the terminal ERR-Out. That is, the abnormality signal ERR of an H level is output.

As described above, in the drive circuit 50 according to the present embodiment, each of the drive control circuits 51-1 to 51-4 includes the abnormality signal input/output circuit 490 coupled to each other by a wired OR. Thereby, when any of the drive control circuits 51-1 to 51-4 is abnormal, abnormality information can be propagated to the normal drive control circuits 51-1 to 51-4. It is possible to control whether operations of the normal drive control circuits 51-1 to 51-4 are continued or stopped, according to the propagated abnormality information. Thus, both convenience and safety of the liquid ejecting apparatus 1 can be further enhanced.

Further, the register control circuit 440 generates drive data dC1 for outputting the drive signal COM having a constant voltage value at the voltage Vos from the drive signal output circuit 501 based on the input drive data signal DATA and inputs the drive data to the DAC section 520. The drive data dC1 output by the register control circuit 440 may be changeable, and thereby, it is possible to randomly change the voltage Vos which is a voltage value of the drive signal COM defined by the drive data dC1. Thereby, it is possible to randomly change the voltage Vos, which is the voltage value of the drive signal COM defined by the drive data dC1.

The DAC section 520 converts the drive data dC1 input from the register control circuit 440 into the original drive signal aA that is an analog signal. The original drive signal aA is a target signal before amplification of the drive signal COM having a constant voltage value. The modulator 530 receives the original drive signal aA. The modulator 530 outputs a modulation signal Ms obtained by performing a pulse width modulation of the original drive signal aA. The gate driver 540 amplifies the input modulation signal Ms based on the voltage signal GVDD and generates the amplification control signal Hgd that is level-shifted to a high amplitude logic based on the voltage signal VHVab, and the amplification control signal Lgd obtained by inverting a logic level of the input modulation signal Ms and amplifying the modulation signal MS based on the voltage signal GVDD. The amplification circuit 550 operates based on the amplification control signals Hgd and Lgd to output the amplification modulation signal AMs, and the demodulation circuit 560 demodulates the amplification modulation signal to generate the drive signal COM having a constant voltage value at the voltage Vos.

Further, the register control circuit 440 generates drive data dC2 and outputs the drive signal to the constant voltage output circuit 420. The constant voltage output circuit 420 generates a voltage signal VCNT having a constant voltage value at a voltage Vcnt based on the input drive data dC2 and outputs the voltage signal VCNT to the terminal Com-Dis. In other words, the constant voltage output circuit 420 makes a voltage value of the terminal Com-Dis constant at the voltage Vcnt based on the drive data dC2. Here, the terminal Com-Dis is electrically coupled to a wire through which the drive signal COM is propagated via the resistor 571. That is, the constant voltage output circuit 420 is electrically coupled to the electrode 611 of the piezoelectric element 60 in the same manner as the drive signal output circuit 501, and controls a voltage value of the wire through which the drive signal COM is propagated to be constant at the voltage Vcnt.

FIG. 19 is a diagram illustrating an example of a configuration of the constant voltage output circuit 420. The constant voltage output circuit 420 includes a comparator 421, a transistor 422, and a DAC 423. Description will be made on the assumption that the transistor 422 is an NMOS transistor.

The drive data dC2 is input to the DAC 423. The DAC 423 inputs a signal having of a voltage value corresponding to the input drive data dC2 to a negative input end of the comparator 421. Here, the DAC 423 may include a variable DC power supply that outputs a signal having a voltage value according to the input drive data dC2. A positive input end of the comparator 421 is electrically coupled to the terminal Com-Dis. An output end of the comparator 421 is electrically coupled to a gate terminal of the transistor 422. A drain terminal of the transistor 422 is electrically coupled to the terminal Com-Dis. Further, the ground potential is supplied to a source terminal of the transistor 422.

In the constant voltage output circuit 420 configured as described above, when a voltage value supplied to the positive input end of the comparator 421 is greater than a voltage value supplied to the negative input end of the comparator 421, the comparator 421 outputs a signal of an H level. That is, when a voltage value of the terminal Com-Dis is greater than a voltage value output from the DAC 423 defined by the drive data dC2, the comparator 421 outputs the signal of an H level. Thus, the transistor 422 is turned on. As a result, the voltage value of the terminal Com-Dis is reduced. Meanwhile, when the voltage value supplied to the positive input end of the comparator 421 is less than the voltage value supplied to the negative input end of the comparator 421, the comparator 421 outputs a signal of an L level. That is, when the voltage value of the terminal Com-Dis is less than a voltage value output from the DAC section 423 defined by the drive data dC2, the comparator 421 outputs the signal of an L level. Thus, the transistor 422 is turned off. As a result, the voltage signal VHV2 is supplied to the terminal Com-Dis via the resistor 572, and the voltage value of the terminal Com-Dis is increased.

Thus, the constant voltage output circuit 420 controls an operation of the transistor 422 such that the voltage value of the terminal Com-Dis becomes the voltage Vcnt defined by the drive data dC2 output from the DAC 423. Here, the drive data dC1 and dC2 output by the register control circuit 440 may be obtained by reading in advance a value stored in a register (not illustrated) by the register control circuit 440, or may be appropriately changed based on the drive data signal DATA input to the drive circuit 50.

Here, as illustrated in FIG. 3A, the drive circuit 50 according to the present embodiment includes four drive control circuits 51, specifically, the drive control circuits 51-1 to 51-4.

The reference voltage signal VBS1 output from the reference voltage signal output circuit 460 included in the drive control circuit 51-1 is supplied to the electrode 612 of the piezoelectric element 60 included in the head 22-1 of the ejecting module 21-1 and the electrode 612 of the piezoelectric element 60 included in the head 22-2 of the ejecting module 21-2. In other words, the drive control circuit 51-1 includes the reference voltage signal output circuit 460 that outputs the reference voltage signal VBS1, and the reference voltage signal output circuit 460 included in the drive control circuit 51-1 is electrically coupled to the electrode 612 of the piezoelectric element 60 included in the head 22-1 included in the head 22-1 of the ejecting module 21-1 and the electrode 612 of the piezoelectric element 60 included in the head 22-2 of the ejecting module 21-2.

Further, the reference voltage signal VBS2 output from the reference voltage signal output circuit 460 included in the drive control circuit 51-2 is not supplied to any of the ejecting modules 21-1 to 21-4, and the terminal VBS-Out from which the reference voltage signal VBS2 from the drive control circuit 51-2 is output is electrically decoupled. In other words, the drive control circuit 51-1 includes the reference voltage signal output circuit 460 that outputs the reference voltage signal VBS1 and the terminal VBS-Out from which the reference voltage signal VBS2 is output, and the terminal VBS-Out from which the reference voltage signal VBS2 is output is electrically decoupled. Thus, the drive control circuit 51-2 is not electrically coupled to the electrode 612 of the piezoelectric element 60 included in the head 22-1 of the ejecting module 21-1 and the electrode 612 of the piezoelectric element 60 included in the head 22-2 of the ejecting module 21-2.

Likewise, the reference voltage signal VBS3 output from the reference voltage signal output circuit 460 included in the drive control circuit 51-3 is supplied to the electrode 612 of the piezoelectric element 60 included in the head 22-3 of the ejecting module 21-3 and the electrode 612 of the piezoelectric element 60 included in the head 22-4 included in the ejecting module 21-4. In other words, the drive control circuit 51-3 includes the reference voltage signal output circuit 460 that outputs the reference voltage signal VBS3, and the reference voltage signal output circuit 460 included in the drive control circuit 51-3 is electrically coupled to the electrode 612 of the piezoelectric element 60 included in the head 22-3 of the ejecting module 21-3 and the electrode 612 of the piezoelectric element 60 included in the head 22-4 of the ejecting module 21-4.

Further, the reference voltage signal VBS4 output from the reference voltage signal output circuit 460 included in the drive control circuit 51-4 is not supplied to any of the ejecting modules 21-1 to 21-4, and thus, the terminal VBS-Out of the drive control circuit 51-4 from which the reference voltage signal VBS4 is output is electrically decoupled. In other words, the drive control circuit 51-4 includes the reference voltage signal output circuit 460 that outputs the reference voltage signal VBS4 and the terminal VBS-Out from which the reference voltage signal VBS4 is output, and the terminal VBS-Out from which the reference voltage signal VBS4 is output is electrically decoupled. Thus, the drive control circuit 51-4 is not electrically coupled to the electrode 612 of the piezoelectric element 60 included in the head 22-3 of the ejecting module 21-3 and the electrode 612 of the piezoelectric element 60 included in the head 22-4 of the ejecting module 21-4.

Here, the reference voltage signal output circuit 460 included in the drive control circuit 51-1 is an example of a first reference voltage signal output circuit, and the reference voltage signal VBS1 output by the reference voltage signal output circuit 460 included in the drive control circuit 51-1 is an example of a first reference voltage signal. Further, the reference voltage signal output circuit 460 included in the drive control circuit 51-2 is an example of a second reference voltage signal output circuit, and the reference voltage signal VBS2 output by the reference voltage signal output circuit 460 included in the drive control circuit 51-2 is an example of a second reference voltage signal. The terminal VBS-Out of the drive control circuit 51 from which the reference voltage signal VBS2 is output corresponds to an output terminal. Further, the reference voltage signal output circuit 460 included in the drive control circuit 51-3 is an example of a third reference voltage signal output circuit, and the reference voltage signal VBS2 output by the reference voltage signal output circuit 460 included in the drive control circuit 51-3 is an example of a third reference voltage signal.

Here, in FIG. 3A, the terminal VBS-Out which is included in the drive control circuit 51-2 and from which the reference voltage signal VBS2 is output, and the terminal VBS-Out which is included in the drive control circuit 51-4 and from which the reference voltage signal VBS4 is output, are illustrated as being electrically decoupled, but may be electrically coupled to the ground via a capacitor not illustrated.

By decoupling the terminal VBS-Out which is included in the drive control circuit 51-2 and from which the reference voltage signal VBS2 is output and the terminal VBS-Out which is included in the drive control circuit 51-4 and from which the reference voltage signal VBS4 is output, the number of components provided in the drive circuit 50 can be reduced, and the drive circuit 50 can be downsized. Meanwhile, by providing capacitors electrically coupled to the ground to the terminal VBS-Out which is included in the drive control circuit 51-2 and from which the reference voltage signal VBS2 is output, and the terminal VBS-Out which is included in the drive control circuit 51-4 and from which the reference voltage signal VBS4 is output, it is possible to reduce a possibility that the drive circuit 50 abnormally operates due to noise or the like being superimposed on the terminal.

5.3. Operation of Drive Control Circuit

In the drive control circuit 51 configured as described above, state transition information included in the drive data signal DATA is held in the sequence register 441 included in the register control circuit 440 in synchronization with the clock signal MCK. The register controller 443 included in the register control circuit 440 causes the drive control circuit 51 to perform a sequence control based on the state transition information held in the sequence register 441. As the sequence control of the drive control circuit 51 is performed, operation state information indicating an operation state of the drive control circuit 51 is appropriately held in the state register 442. The register control circuit 440 outputs the control signals CNT1 to CNT5 and the drive data dC1 and dC2 according to the operation state information held in the state register 442.

Here, the sequence control of the drive control circuit 51 will be described with reference to FIG. 20. FIG. 20 is a diagram illustrating an example of state transition of the drive control circuit 51.

As illustrated in FIG. 20, the drive control circuit 51 has operation states of a startup mode M1, a first standby mode M2, a printing mode M3, and a second standby mode M4. The drive control circuit 51 performs the state transition among the startup mode M1, the first standby mode M2, the printing mode M3, and the second standby mode M4 based on the state transition information held in the sequence register 441. The drive control circuit 51 may include an operation state such as an abnormality processing mode for performing transition when abnormality occurs in the drive control circuit 51 in addition to the four operation states of the startup mode M1, the first standby mode M2, the printing mode M3, and the second standby mode M4.

If power is supplied to the liquid ejecting apparatus 1, transition to the startup mode M1 is performed by the drive control circuit 51.

In the startup mode M1, initial setting of the liquid ejecting apparatus 1 and the drive control circuit 51 is performed. After the initial setting is completed, the drive control circuit 51 stands by. Here, in the initial setting of the liquid ejecting apparatus 1, the first power supply circuit 90a starts generating the voltage signal VHV1, the second power supply circuit 90b starts generating the voltage signal VDD, the control signal output circuit 100 controls all the selection circuits 230 to be non-conductive, and the like. Further, the initial setting of the drive control circuit 51 includes, for example, that the register control circuit 440 controls all the control signals CNT1 to CNT3 to an L level. Thereby, supply of the voltage signal VHV2 to the ejecting module 21 is blocked, electric charges in a propagation path through which the drive signal COM is propagated are released, and furthermore, supply of the reference voltage signal VBS to the ejecting module 21 stops. Thus, in the startup mode M1, voltage values of both the electrodes 611 and 612 of the piezoelectric element 60 are controlled to the ground potential. As a result, a possibility that a potential difference occurs between the electrodes 611 and 612 of the piezoelectric element 60 is reduced, and a possibility that unintended stress is generated in the piezoelectric element 60 and a possibility that a reverse voltage is supplied to the piezoelectric element 60 are reduced.

In the startup mode M1, if the state transition information for performing a startup sequence (SEQ: Sequence) S110 is held in the sequence register 441, the register control circuit 440 performs the startup sequence S110.

In the startup sequence S110, the register control circuit 440 sequentially outputs the control signals CNT1 to CNT3 and the drive data dC1 and dC2 at a predetermined timing. Specifically, in the startup sequence S110, the register control circuit 440 raises the control signal CNT3 to an H level. Thereby, supply of the voltage signal VHV to the head unit 20 starts. Thereafter, the register control circuit 440 raises the control signal CNT2 to an H level. Thereby, the reference voltage signal output circuit 460 starts generating the reference voltage signal VBS and outputs the generated reference voltage signal to the electrode 612 of the piezoelectric element 60. In this case, since the selection circuit 230 is controlled to be non-conductive, a voltage value of the electrode 611 of the piezoelectric element 60 is raised to a state in which a voltage value substantially equal to the voltage value of the reference voltage signal VBS supplied to the electrode 612 is held. The register control circuit 440 raises the control signal CNT1 to an H level. Thereby, release of electric charges in a propagation path through which the drive signal COM is propagated stops. Thereafter, the drive signal output circuit 501 starts a self-excited oscillation and outputs the drive signal COM having a constant voltage value at the voltage Vos. Thereby, the drive control circuit 51 performs transition to the first standby mode M2.

In the first standby mode M2, the register control circuit 440 controls all the control signals CNT1 to CNT3 to an L level. Thereby, the voltage signal VHV2 is supplied to the ejecting module 21, release of the electric charges in the propagation path through which the drive signal COM is propagated stops, and the reference voltage signal VBS is supplied to the ejecting module 21. The drive control circuit 51 enters a first idling state in which the drive signal output circuit 501 performs a self-excited oscillation and ink is not ejected from the ejecting module 21. In this case, a voltage value of the electrode 611 of the piezoelectric element 60 is controlled based on the drive signal COM which has a voltage value that is constant at the voltage Vos and which is output from the drive signal output circuit 501, and a voltage value of the electrode 612 is controlled to the reference voltage signal VBS which has a voltage value that is constant at the voltage Vos and which is output from the reference voltage signal output circuit 460. That is, in the first standby mode M2, a voltage value supplied to the electrode 611 of the piezoelectric element 60 and a voltage value supplied to the electrode 612 thereof are controlled by the register control circuit 440. Thus, a possibility that the voltage values supplied to the electrodes 611 and 612 of the piezoelectric element 60 are unstable is reduced, and as a result, a possibility that unintended stress is generated in the piezoelectric element 60 and a possibility that an unintended reverse voltage is supplied to the piezoelectric element 60 are reduced. Here, in the present embodiment, it means that the voltage value supplied to the electrode 611 is smaller than the voltage value supplied to the electrode 612, but in a broad sense, the voltage is a voltage of an electric field in the opposite direction to a DC electric field obtained by performing polarization processing for the piezoelectric element 60, and is a voltage in a direction in which the piezoelectric body 601 may be disturbed in a polarization direction aligned by the polarization process.

Furthermore, in the first standby mode M2, the voltage Vos, which is a voltage value defined based on drive data dC1, is preferably controlled to a value that is the same as the voltage Vbs which is a voltage value of reference voltage signal VBS. Here, the same value is not limited to a voltage value in which the voltage Vos completely coincides with the voltage Vbs, includes a case where the voltage values are substantially the same, and includes a case where the voltage Vos and the voltage Vbs have substantially the same voltage value, for example, when a circuit variation of the drive signal output circuit 501 and a circuit variation of the reference voltage signal output circuit 460 are added. Thereby, a possibility that unintended stress is generated in the piezoelectric element 60 is further reduced.

In the first standby mode M2, when state transition information for state transition to the printing mode M3 is held in the sequence register 441, the register control circuit 440 performs a printing process start sequence S210.

By performing the printing process start sequence S210, the register control circuit 440 controls such that the drive signal output circuit 501 generates the drive signal COM having a constant voltage value at the voltage Vc, based on the drive data signal DATA input by the control signal output circuit 100. Thereby, the drive control circuit 51 performs transition to the printing mode M3.

In the printing mode M3, the drive signal output circuit 501 generates the drive signal COM which is obtained by amplifying a signal having a waveform defined by the drive data signal DATA input from the control signal output circuit 100, for example, in which the voltage value illustrated in FIG. 5 varies, and supplied the generated drive signal to the ejecting module 21. Further, in the printing mode M3, the control signal output circuit 100 generates the clock signal SCK, the printing data signal SI, the latch signal LAT, and the change signal CH for individually controlling the selection circuit 230 to be conductive or non-conductive, and outputs the signals to the drive signal selection control circuit 200. That is, in the printing mode M3, the selection circuit 230 is controlled to be conductive or non-conductive according to the clock signal SCK, the printing data signal SI, the latch signal LAT, and the change signal CH. Thus, in the printing mode M3, the piezoelectric element 60 is supplied with the drive signal COM whose voltage value changes at a timing expected by the clock signal SCK, the printing data signal SI, the latch signal LAT, and the change signal CH. As a result, the piezoelectric element 60 is driven based on a potential difference between the drive signal COM supplied to the electrode 611 and the reference voltage signal VBS supplied to the electrode 612, and an amount of ink corresponding to the drive of the piezoelectric element 60 is ejected from the nozzle 651. That is, the printing process is performed.

In the printing mode M3, if a printing process ends, the state transition information for state transition to the first standby mode M2 is held in the sequence register 441. Thereby, the register control circuit 440 performs a printing process end sequence S310.

By performing the printing process end sequence S310, the register control circuit 440 controls the drive signal output circuit 501 to generate the drive signal COM having a constant voltage value at the voltage Vos, based on the drive data dC1. Thereby, the drive control circuit 51 performs transition to the first standby mode M2.

Further, in the first standby mode M2, the state transition information for state transition to the second standby mode M4 is held in the sequence register 441, the register control circuit 440 performs a self-excited oscillation stop sequence S220.

By performing the self-excited oscillation stop sequence S220, the register control circuit 440 controls the constant voltage output circuit 420 to generate the voltage signal VCNT having a constant voltage value at the voltage Vcnt, based on the drive data dC2. Thereby, the drive control circuit 51 performs transition to the second standby mode M4.

In the second standby mode M4, the drive control circuit 51 enters a second idling state in which the drive signal output circuit 501 stops the self-excited oscillation and ink is not ejected from the ejecting module 21. In this case, the voltage value of the electrode 611 of the piezoelectric element 60 is controlled based on the voltage signal VCNT which is output from the constant voltage output circuit 420 and has a constant voltage value at the voltage Vcnt, and the voltage value of the electrode 612 is controlled to the reference voltage signal VBS which is output from the reference voltage signal output circuit 460 and has a constant voltage value at the voltage Vbs. That is, in the second standby mode M4, the voltage value supplied to the electrode 611 of the piezoelectric element 60 and the voltage value supplied to the electrode 612 thereof are controlled by the register control circuit 440. Thus, a possibility that the voltage values supplied to the electrodes 611 and 612 of the piezoelectric element 60 are unstable is reduced, and as a result, a possibility that unintended stress is generated in the piezoelectric element 60 and a possibility that an unintended reverse voltage is supplied to the piezoelectric element 60 are reduced.

Furthermore, in the second standby mode M4, the voltage Vcnt having a voltage value defined based on the drive data dC2 is preferably controlled to a value that is equal to the voltage Vbs which is a voltage value of the reference voltage signal VBS. Here, the same value is not limited to a voltage value in which the voltage Vos completely coincides with the voltage Vcnt, includes a case where the voltage values are substantially the same, and includes a case where the voltage Vcnt and the voltage Vbs have substantially the same voltage value, for example, when a circuit variation of the constant voltage output circuit 420 and a circuit variation of the reference voltage signal output circuit 460 are added. Thereby, a possibility that unintended stress is generated in the piezoelectric element 60 is further reduced.

As described above, the second standby mode M4 is different from the first standby mode M2 in that the liquid ejecting apparatus 1 stands by in a state where the drive signal output circuit 501 stops an oscillation. In the first standby mode M2, the liquid ejecting apparatus 1 stands by in a state where the drive signal output circuit 501 oscillates, and thus, when the printing process is requested to perform, transition of an operation state of the liquid ejecting apparatus 1 to the printing mode M3 can be performed in a short time. In contrast to this, in the second standby mode M4, the liquid ejecting apparatus 1 stands by in a state where the drive signal output circuit 501 stops the oscillation, and thus, a standby power of the liquid ejecting apparatus 1 generated when standing by can be reduced.

In the second standby mode M4, when the state transition information for state transition to the first standby mode M2 is held in the sequence register 441, the register control circuit 440 performs a self-excited oscillation start sequence S420.

By performing the self-excited oscillation start sequence S420, the register control circuit 440 controls the drive signal output circuit 501 to start a self-excited oscillation and output the drive signal COM having a constant voltage value at the voltage Vos, based on the drive data dC1. Thereby, the drive control circuit 51 performs transition to the first standby mode M2.

Further, when the drive control circuit 51 stops the operation, transition to the startup mode M1 of the operation state of the drive control circuit 51 is performed.

In the first standby mode M2 and the second standby mode M4, if the state transition information for performing the stop sequence S230 for stopping the operation of the drive control circuit 51 is held in the sequence register 441, the register control circuit 440 performs the stop sequence S230.

In the stop sequence S230, the register control circuit 440 sequentially outputs the control signals CNT1 to CNT3 and the drive data dC1 and dC2 at a predetermined timing. Specifically, in the stop sequence S230, the register control circuit 440 lowers the control signal CNT2 to an L level. Thereby, the reference voltage signal output circuit 460 stops generation of the reference voltage signal VBS and releases the electric charges stored in the electrode 612 of the piezoelectric element 60. Thereafter, the drive signal output circuit 501 outputs the drive signal COM having a constant voltage value at the voltage Vos based on the drive data dC1. The register control circuit 440 raises the control signal CNT1 to an H level. Thereby, electric charges in a propagation path through which the drive signal COM is propagated are released. Thereafter, the register control circuit 440 raises the control signal CNT3 to an H level. Thereby, supply of the voltage signal VHV to the head unit 20 stops. Thereby, the drive control circuit 51 performs transition to the startup mode M1.

As described above, in the liquid ejecting apparatus 1 according to the present embodiment, state transitions of the operation state of the drive control circuit 51 are performed among the startup mode M1, the first standby mode M2, the printing mode M3, and the second standby mode M4. The state transition of the drive control circuit 51 is performed by the sequence control performed in the register control circuit 440. By performing the sequence control of the drive control circuit 51 according to the above-described sequence, a possibility that unintended stress is generated in the piezoelectric element 60 and a possibility that a reverse voltage is applied to the piezoelectric element 60 are reduced even during a period in which the liquid ejecting apparatus 1 performs the state transition.

Further, the drive circuit 50 according to the present embodiment includes a plurality of the drive control circuits 51, specifically, drive control circuits 51-1 to 51-4. In this case, the drive control circuit 51-1 starts startup after the drive control circuit 51-2, and the drive control circuit 51-1 stops an operation before the drive control circuit 51-2. Further, the drive control circuit 51-3 starts startup after the drive control circuit 51-4, and the drive control circuit 51-3 stops an operation before the drive control circuit 51-4.

Here, start of the startup of the drive control circuits 51-1 to 51-4 corresponds to start of the startup sequence S110 when each of the drive control circuits 51-1 to S1-4 is in the startup mode M1. Further, stop of the operation of the drive control circuits 51-1 to 51-4 corresponds to start of the stop sequence S230 when each of the drive control circuits 51-1 to 51-4 is in the first standby mode M2 or the second standby mode M4.

As illustrated in FIGS. 3A and 3B, the reference voltage signal VBS1 output from the drive control circuit 51-1 is also supplied to the electrode 612 of the piezoelectric element 60 included in the head 22-2 to which the drive control circuit 51-2 outputs the drive signal COM2. Accordingly, when the drive control circuit 51-1 starts an operation before the drive control circuit 51-2, the reference voltage signal VBS1 is supplied to the electrode 612 of piezoelectric element 60 before a voltage of the electrode 611 of the piezoelectric element 60 included in the head 22-2 is controlled. As a result, a voltage value of the electrode 612 is controlled before a voltage value of the electrode 611 of the piezoelectric element 60 is controlled, and as a result, there is a possibility that a reverse voltage is generated in which a potential of the electrode 612 of the piezoelectric element 60 included in the head 22-2 is higher than a potential of electrode 612. In contrast to this, the drive control circuit 51-1 starts startup after the drive control circuit 51-2, and thus, a voltage value of the electrode 611 of the piezoelectric element 60 is controlled by the drive control circuit 51-2 before a voltage is supplied to the electrode 612 of the piezoelectric element 60 included in the head 22-2. Thus, it is possible to reduce a possibility that a reverse voltage is generated in the piezoelectric element 60 included in the head 22-2.

Further, when the drive control circuit 51-1 stops an operation after the drive control circuit 51-2, the voltage value of the electrode 611 of the piezoelectric element 60 becomes indefinite regardless of supply of the reference voltage signal VBS1 to the electrode 612 of the piezoelectric element 60 included in the head 22-2. As a result, there is a possibility that a so-called reverse voltage is generated in which the voltage value of the electrode 611 of the piezoelectric element 60 is lower than the voltage value of the electrode 612 of the piezoelectric element 60. In contrast to this, as the drive control circuit 51-1 stops an operation before the drive control circuit 51-2, supply of the reference voltage signal VBS1 to the electrode 612 stops in a state where the drive control circuit 51-2 supplies the drive signal COM to the electrode 611 of the piezoelectric element 60 included in the head 22-2, and furthermore, electric charges stored by the reference voltage signal VBS1 are released. Thus, it is possible to reduce a possibility that a reverse voltage is generated in the piezoelectric element 60 included in the head 22-2.

Likewise, as illustrated in FIGS. 3A and 3B, since the reference voltage signal VBS3 output from the drive control circuit 51-3 is also supplied to the electrode 612 of the piezoelectric element 60 included in the head 22-4 from which the drive control circuit 51-4 outputs the drive signal COM4, as the drive control circuit 51-3 starts the startup after the drive control circuit 51-4 and stops the operation before the drive control circuit 51-4, a possibility that a reverse voltage is generated in the piezoelectric element 60 included in the head 22-4 is reduced.

6. Action and Effect

As described above, in the drive circuit 50 according to the present embodiment, the drive control circuit 51-1 includes the reference voltage signal output circuit 460 that outputs the reference voltage signal VBS1. The reference voltage signal output circuit 460 included in the drive control circuit 51-1 is electrically coupled to both the electrode 612 of the piezoelectric element 60 included in the head 22-1 that is driven based on the drive signal COM1 output from the drive control circuit 51-1, and the electrode 612 of the piezoelectric element 60 included in the head 22-2 that is driven based on the drive signal COM2 output from the drive control circuit 51-2. That is, the reference voltage signal VBS output by the reference voltage signal output circuit 460 included in the drive control circuit 51-1 is supplied to both the electrode 612 of piezoelectric element 60 included in the head 22-1 that is driven based on the drive signal COM1 output from the drive control circuit 51-1, and the electrode 612 of the piezoelectric element 60 included in the head 22-2 that is driven based on the drive signal COM2 output from the drive control circuit 51-2. Thereby, a reference potential for driving the piezoelectric element 60 included in each of the different heads 22-1 and 22-2 is stabilized, and as a result, a drive accuracy of the piezoelectric element 60 included in each of the heads 22-1 and 22-2 is increased.

As the drive control circuit 51-1 that supplies the reference voltage signal VBS1 to both the piezoelectric element 60 included in the head 22-1 and the piezoelectric element 60 included in the head 22-2 starts startup after the drive control circuit 51-2 that does not supply the reference voltage signal VBS2 to the piezoelectric element 60 included in in the head 22-1. and the piezoelectric element 60 included in the head 22-2, it is possible to reduce a possibility that the reference voltage signal VBS1 is supplied to the electrode 612 of the piezoelectric element 60 included in the head 22-2 before the drive control circuit 51-2 starts to control a potential of the electrode 611 of the piezoelectric element 60 included in the head 22-2. As a result, a possibility that a reverse voltage is supplied to the piezoelectric element 60 included in the head 22-2 is reduced, and a possibility that the piezoelectric element performs an abnormal operation is reduced.

As such, although embodiments and modification examples are described above, the present disclosure is not limited to the embodiments and can be implemented in various forms without departing from the gist of the disclosure. For example, the above embodiments can be appropriately combined.

The present disclosure includes substantially the same configuration (for example, a configuration having the same function, method, and result, or a configuration having the same object and effect) as the configuration described in the embodiment. Further, the present disclosure includes a configuration in which a non-essential portion of the configuration described in the embodiment is replaced. Further, the present disclosure includes a configuration having the same action and effect as in the configuration described in the embodiment or a configuration capable of achieving the same object. Further, the present disclosure includes a configuration in which a known technology is added to the configuration described in the embodiment.

Number	Name	Date	Kind
8807680	Takagi	Aug 2014	B2
9669621	Nozawa	Jun 2017	B2
9937712	Nozawa	Apr 2018	B2
10328690	Chino	Jun 2019	B2
20160339690	Matsumoto	Nov 2016	A1
20170173948	Fujisawa	Jun 2017	A1

Drive circuit and liquid ejecting apparatus

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