Patent Grant
9250641
1. Technical Field
The present invention relates to a technology for generating a predetermined voltage waveform, thereby driving a load.
2. Related Arts
Today, quite a number of devices use electricity as energy sources, and have various types of components operating with electricity incorporated therein. Although most of the components incorporated in the devices are arranged to exert predetermined functions only by supplying standardized electrical power, on the other hand, there are many components (components operating in an analog manner) which require power supply with a precisely controlled voltage value or voltage waveform in order for exerting predetermined functions. Further, the devices incorporating such components operating in an analog manner also incorporate dedicated circuits (driving circuits) for generating electric power with target voltage values or voltage waveforms to drive such analog-like components. It should be noted that the component driven by the driving circuit may sometimes be called a load of the driving circuit (or simply a load).
In such driving circuits, it is required to supply electrical power with the most accurate possible voltage value or voltage waveform. Therefore, the voltage supplied to the load may sometimes be detected to perform negative feedback control (feedback control) so that the voltage becomes a target voltage. Further, there is proposed a technology, in the case of driving a plurality of loads, attempting to use counter-electromotive force generated in one load for driving of another load in order for reducing power consumption (e.g., JP-A-9-23643, JP-A-2002-281770).
However, since these proposed technologies are not applicable unless a plurality of loads are driven and the loads are types of load generating counter electromotive force, there arises a problem that the scope of application is significantly limited.
An advantage of some aspects of the invention is to provide a load driving circuit providing a driving technology capable of reducing the power consumption, and adopts the following configurations.
A load driving circuit according to an aspect of the invention is adapted to generate a desired voltage waveform to drive a load, and includes a target voltage waveform output section adapted to output a target voltage waveform to be applied to the load, a plurality of power supply sections generating electrical power with voltage values different from each other, a plurality of negative feedback control sections disposed between the power supply sections and the load so as to correspond respectively to the power supply sections, and adapted to supply electrical power from the respective power supply sections to the load, and execute negative feedback control of a value of a voltage applied to the load for matching the voltage value and the target voltage waveform with each other, and a power supply connection section adapted to select one of the power supply sections based on one of the value of the voltage applied to the load and the voltage value of the target voltage waveform, and connect the selected power supply section to the load and disconnect the rest of the power supply sections from the load.
Further, a load driving method according to another aspect of the invention corresponds to the load driving circuit described above and is adapted to generate a desired voltage waveform to drive a load, including the steps of outputting a target voltage waveform to be applied to the load, generating electrical power with voltage values different from each other from a plurality of power supply sections, selecting one of the power supply sections based on one of a value of a voltage applied to the load and a voltage value of the target voltage waveform, and executing a negative feedback control of a value of a voltage to be applied to the load for receiving the electrical power from the selected power supply section to supply the load with the electrical power, and matching the value of the voltage applied to the load and the target voltage waveform with each other.
In the load driving circuit and the load driving method according to the aspects of the invention, there is provided a plurality of power supply sections generating electrical power with voltage values different from each other. Further, the negative feedback control sections are provided to the respective power supply sections, and the target voltage waveform to be applied to the load is input to each of the negative feedback control sections. As a result, it becomes possible in each of the negative feedback control sections to supply the load with the electrical power received from the corresponding power supply section while performing the negative feedback control along the target voltage waveform. Further, one power supply section (and the negative feedback control section) is selected among the plurality of power supply sections (and the negative feedback control sections) thus configured based on the value of the voltage applied to the load or the voltage value of the target voltage waveform and is connected to the load, and at the same time, the remaining power supply sections (and the negative feedback control sections) are disconnected from the load.
By adopting such a configuration, it is possible to drive the load using the power supply section selected among the plurality of power supply sections generating the electrical power with voltage values different from each other in accordance with the value of the voltage to be applied. Therefore, since the difference between the value of the voltage generated in the power supply section and the value of the voltage applied to the load can be made smaller, the electrical power consumed between the power supply section and the load can be reduced. As a result, it becomes possible to reduce the power consumed when driving the load. Further, since nothing is required other than providing a plurality of power supply sections with values of generation voltages different from each other and negative feedback control sections, and driving the load while switching the power supply sections and the negative feedback control sections, the configuration can be applied to any types of loads.
Further, in the load driving circuit according to the aspect of the invention, in the case of driving the load (the load capable of storing at least a part of the electrical power supplied thereto) including a capacitive component, the following is also possible. Firstly, power supply sections capable of storing the electrical power supplied thereto are used as the power supply sections. For example, a power supply capacitor (preferably having a capacitance sufficiently larger than the capacitance of the load) has previously been incorporated in the power supply section. Further, when the value of the voltage applied to the load rises, the load is driven using the power supply section generating the voltage with a value higher than the value of the voltage applied to the load. In contrast, when the value of the voltage applied to the load decreases, the load is driven using the power supply section generating the voltage with a value lower than the value of the voltage applied to the load.
By adopting such a configuration, the electrical power supplied from the power supply sections (the power supply capacitor) is stored in the load during the period in which the value of the voltage applied to the load is rising, and when the value of the voltage applied to the load decreases, the electrical power stored in the load is refluxed to the power supply section (the power supply capacitor) and stored therein. Further, when the value of the voltage applied to the load subsequently rises, it is possible to drive the load using the electrical power refluxed from the load and stored in the power supply section (the power supply capacitor). As a result, it becomes possible to significantly reduce the electrical power for driving the load.
Further, in the load driving circuit according to the aspect of the invention, the following configuration can also be adopted. Firstly, a variable resistance section having a variable resistance value has previously been disposed between each of the power supply sections and the load, and it is arranged that the negative feedback control can be executed on the resistance value of the variable resistance section using the resistance value control section so that the value of the voltage applied to the load and the target voltage waveform match with each other. Further, it is also possible to configure that during the period in which the output of the resistance value control section is supplied to the variable resistance section to execute the negative feedback control on the resistance value, the electrical power is supplied to the load from the power supply section connected to the variable resistance section, and in contrast, when electrically disconnecting the output of the resistance value control section and the variable resistance section from each other, the resistance value of the variable resistance section increases to a substantially infinite value to disconnect the power supply section, which is connected to the variable resistance section, from the load.
By adopting such a configuration, since the load driving circuit can be configured using universal components with sufficient reliability such as operational amplifiers or transistors, it becomes possible to simply and easily configure the driving circuit with high reliability.
Although a plurality of negative feedback circuits is formed in the load driving circuit according to the aspect of the invention configured as described above, not all of the circuits perform the negative feedback control at a time, and only one of the negative feedback circuits can actually perform the negative feedback control. Therefore, it is also possible to adopt the configuration in which the resistance value control section for controlling the resistance value is shared by a plurality of variable resistance sections, and used while switching the variable resistance sections.
By adopting such a configuration, since it becomes unnecessary to provide the corresponding number of resistance value control sections to the number of power supply sections, the configuration of the load driving circuit can be simplified.
Further, in the load driving circuit according to the aspect of the invention described above, the following is also possible. Firstly, the values of the voltages generated by the respective power supply sections have previously been detected. Then, when selecting the power supply section for driving the load, it is also possible to select the power supply section based not only on the value of the voltage applied to the load, but also on the values of the voltages generated by the respective power supply sections.
By adopting such a configuration, since the load can be driven always using the appropriate power supply section even in the case in which the value of the voltage generated by the power supply section becomes unstable, it become possible to significantly reduce the power consumption.
The invention will now be described with reference to the accompanying drawings, wherein like numbers reference like elements.
Hereinafter, the embodiments will be explained in the following order.
A. Outline of the Embodiments
B. First Embodiment
B-1. Configuration of Resistive Load Driving Circuit
B-2. Operation of Resistive Load Driving Circuit
C. Second Embodiment
C-1. Configuration of Capacitive Load Driving Circuit
C-2. Operation of Capacitive Load Driving Circuit
D. Modified Examples
D-1. First Modified Example
D-2. Second Modified Example
As the load driving circuit of the invention, various forms of embodiments, which will hereinafter be explained, can be considered, and before all, the outline common to the embodiments will briefly be explained for the sake of convenience of better understanding.
In other words, it is conceivable that each of the sets of the power supply section 10 and the negative feedback control section 30 corresponding to the power supply section 10 forms a small drive circuit, so to speak. Further, it is arranged that the target voltage waveform output section 20 supplies the target voltage waveform, thereby making it possible to drive the load 50. In
A power supply connection section 40 selects one power supply section 10 (i.e., the driving circuit including the power supply section 10) among the plurality of power supply sections 10 based on the voltage value applied to the load 50 or the voltage value of the target voltage waveform output by the target voltage waveform output section 20. For example, when the voltage value to be applied to the load 50 is low, the power supply connection section 40 selects the driving circuit including the power supply section 10 with a low voltage value. In the example shown in
As described above, the load driving circuit 100 of the present embodiments is provided with the plurality of power supply sections 10 differing in a generating voltage value and the negative feedback control sections 30 corresponding respectively to the power supply sections 10. Further, the load driving circuit 100 drives the load 50 while switching the power supply sections 10 and the negative feedback control sections 30 in accordance with the voltage value to be applied to the load 50. Since the power supply sections 10 and the negative feedback control sections 30 are switched in accordance with the voltage value to be applied as described above, it is possible to reduce the voltage difference between the voltage value generated in the power supply section 10 and the voltage value applied to the load 50. As a result, it becomes possible to reduce the power consumption in the negative feedback control section 30 and the power supply connection section 40 intervening between the power supply sections 10 and the load 50. Further, since the switching of the power supply sections 10 and the negative feedback control sections 30 is performed only in accordance with the voltage value to be applied to the load 50, it becomes possible to apply the configuration when driving any types of load 50 regardless of, for example, the number of loads and whether or not the load generates counter electromotive force.
It should be noted that although an arbitrary number equal to or greater than two can be taken as the number of power supply sections 10 as described above, the larger the number of power supply sections 10 becomes, the more the voltage difference between the voltage value generated in the power supply section 10 and the voltage value applied to the load 50 can be reduced, and it becomes possible to further reduce the power consumption.
Further, in the example shown in
The same can be applied to the power supply sections 10 and the negative feedback control sections 30. For example,
It should be noted that the reason why diodes are inserted between the transistors NTr1 through NTr4 and the load 50 in
The gate electrode of each of the transistors NTr1 through NTr4 is coupled to an output terminal of an operational amplifier Opamp. It should be noted that a pull-down arrangement is applied to the gate electrode of each of the transistors NTr1 through NTr4 in order for preventing malfunctions, which is omitted from the drawing in order for preventing the drawing from becoming complicated. As well known to the public, when applying a positive voltage between the gate electrode and the source electrode, the NMOS transistor is provided with a path of charge (electrons here) called a channel formed inside the transistor. Further, the higher the value of the voltage applied between the gate electrode and the source electrode is set, the larger channel is formed to make the charge easy to pass through (to reduce the equivalent resistance value), or in contrast, if the value of the voltage applied between the gate electrode and the source electrode is lowered, it becomes difficult for the charge to pass through to increase the equivalent resistance value.
It should be noted that PMOS transistors can also be used as the transistors NTr1 through NTr4 instead of the NMOS transistors. As shown in
The operational amplifier Opamp is provided with two input terminals. One of the input terminals is provided with an analog voltage output from the DA converter (hereinafter described as DAC), and the other of the input terminals is provided with the voltage applied to the load 50 via the input resistor Rs. Further, the output of the operational amplifier Opamp is fed-back to the input terminal via the feedback resistor Rf, thereby forming a so-called negative feedback circuit.
For example, if the value of the voltage applied to the load 50 is lower than the analog voltage output by the DAC, the output of the operational amplifier Opamp increases to raise the voltage applied to the gate electrode, thus the equivalent resistance value of the transistor is reduced. As a result, since an amount of voltage drop in the transistor decreases, the value of the voltage applied to the load 50 is increased. In contrast, when the value of the voltage applied to the load 50 rises beyond the analog voltage output by the DAC, the output of the operational amplifier Opamp decreases, and therefore, the voltage applied to the gate electrode decreases to increase the equivalent resistance value of the transistor. As a result, since an amount of voltage drop in the transistor increases, the value of the voltage applied to the load 50 is decreased. Thus, the value of the voltage applied to the load 50 can be varied in accordance with the analog voltage output from the DAC.
It should be noted that the load driving circuit 100 shown in
Further, the output from the operational amplifier Opamp is connected to the gate electrodes of the transistors NTr1 through NTr4 via switches SN1 through SN4, respectively, and the switches SN1 through SN4 are controlled by a gate selector circuit 140. The gate selector circuit 140 has a function of detecting the analog voltage output by the DAC and the value of the voltage (the output voltage of the operational amplifier Opamp in some cases) applied to the load 50 to put either one of the switches SN1 through SN4 into the connected state while putting the other switches into the disconnected state. Since the pull-down arrangement is applied to the gate electrodes of the transistors NTr1 through NTr4, as described above, when the switch is put into the disconnected state, the voltage is no more applied to the gate electrode of the transistor corresponding to the switch. As a result, the channel in the transistor disappears to stop the current flowing, and there is created the state in which the power supply disposed on the upstream side of the transistor is electrically disconnected from the load 50.
As described above, in the load driving circuit 100 shown in
The case in which the analog voltage output from the DAC increases from 0(V) is now considered. As described above using
Here, the equivalent resistance value of the transistor NTr1 can be reduced by raising the voltage applied to the gate electrode, and the smaller the equivalent resistance value is made, the higher the value of the voltage applied to the load 50 can be made. However, as is obvious, it is not achievable to raise the voltage beyond the voltage value (i.e., E1) generated by the power supply E1. Further, in a strict sense, it is not achievable to make the equivalent resistance value of the transistor NTr1 completely zero, and the diode also has some small amount of resistance. Therefore, it is not achievable to raise the value of the voltage applied to the load 50 beyond the voltage value, which is lower than the voltage value generated by the power supply E1 as much as the voltage drop caused in the transistor NTr1, the diode, and so on.
As described above, there is an upper limit value in the value of the voltage applied to the load 50 by the negative feedback circuit illustrated with the thick solid lines in
It is obvious that the value of the voltage, which can be applied by the power supply E2 to the load 50 also has an upper limit value. However, if the value of the voltage output by the DAC (or the value of the voltage applied to the load 50) reaches the upper limit value, it is then possible to switch OFF the switch SN2 and to switch ON the switch SN3, thereby supplying the load 50 with the electrical power using the power supply E3.
When the voltage (the drive voltage) to be applied to the load 50 rises beyond the voltage value E1, the electrical power from the power supply E2 is supplied to the load 50 using the negative feedback circuit illustrated with the thick broken lines in
As described above, in the load driving circuit 100 of the first embodiment, the range of the voltage, which can be applied to the load 50, is divided into four voltage ranges, namely 0(V) through E1, E1 through E2, E2 through E3, and E3 through E4, and the power supply and the negative feedback circuit are previously set for each of the voltage ranges. Further, when the voltage to be applied to the load 50 is within either one of the voltage ranges, the load 50 is driven using the power supply and the negative feedback circuit corresponding to that voltage range, but if the drive voltage of the load 50 exceed a boundary of the voltage ranges, the power supply and the negative feedback circuit are switched, and the load 50 is driven using the power supply and the negative feedback circuit corresponding to the new voltage range. According to this operation, it becomes possible to reduce the power consumption when driving the load 50. The reason therefor will hereinafter be explained.
The power supply E4 constantly generates the electrical power with the voltage value E4. Therefore, in the driving circuit shown in
In contrast, the load driving circuit 100 of the first embodiment shown in
It should be noted that the explanations are presented hereinabove assuming that the drive voltage applied to the load 50 takes 0(v) or a positive voltage value. However, it is also possible to apply the drive voltage taking a negative value by using a power supply generating a voltage with a negative value. It is obvious that it becomes possible to apply the drive voltage with a voltage value varying from a negative value to a positive value to the load 50 by using a power supply generating a negative voltage value and a power supply generating a positive voltage value.
Further, assuming that the levels of the values E1 through E8 of the voltage generated by these power supplies satisfy the inequality of E1<E2<E3<E4<O<E5<E6<E8<E8, if the drive voltage applied to the load 50 takes a positive voltage value, it is possible to apply the drive voltage in a range of 0(V) through E8 (a positive voltage value) to the load 50 by switching the switch to be switched ON from the switch SN5 to the switch SN8 as the voltage value grows. Further, if the drive voltage to be applied takes a negative voltage value, it becomes possible to apply the drive voltage in a range of 0(V) through E1 (a negative voltage value) to the load 50 by switching the switch to be switched ON from the switch SN4 towards the switch SN1 as the voltage value decreases (the absolute value thereof increases).
In the first embodiment described hereinabove, the explanations are presented assuming that the load 50 is a resistive load. However, in the case in which the load 50 is a capacitive load, it becomes possible to more significantly reduce the power consumption. It should be noted here that the capacitive load is a load having a characteristic of storing at least a part of the electrical power supplied thereto, and a load incorporating a piezoelectric element can be cited as a representative example thereof. Further, liquid crystal panels constitutionally cause large parasitic capacitances, and therefore, can also be regarded as capacitive loads. Further, by applying the load driving circuit 100 of the second embodiment to a load composed of a capacitive load and a resistive load coupled in parallel to each other, the power consumption can significantly be reduced. Hereinafter, the load driving circuit 100 of the second embodiment for driving such a capacitive load 50 will be explained.
C-1. Configuration of Capacitive Load Driving Circuit
It should be noted that also in the second embodiment, any power supplies such as primary batteries, secondary batteries, mere capacitors, or so-called power supply circuits can be used as the power supplies E1 through E4, providing the power supplies generate voltages with the values different from each other. However, in the second embodiment, the power supplies such as secondary batteries or capacitors capable of storing at least a part of electrical power supplied from the outside are used, thereby making it possible to more significantly reduce the power consumption. This point will be explained later in detail.
Further, as shown in
The output terminal of the operational amplifier Opamp is connected to the gate electrodes of the transistors NTr1 through NTr4 for supplying the load 50 with the electrical power of the power supplies E1 through E4 via the switches SN1 through SN4, respectively. This configuration is substantially the same as that of the load driving circuit 100 of the first embodiment shown in
The gate selector circuit 140 switches the states of the switches SN1 through SN4 and the switches SPO through SP3 between an ON state and an OFF state. Further, depending on which one of the switches SN1 through SN4 and SPO through SP3 is switched ON, a negative feedback circuit is formed with the corresponding transistor NTr1 through NTr4 or PTrO through PTr3 and the operational amplifier Opamp. As a result, it becomes possible to execute the negative feedback control on the value of the voltage applied to the load 50 so that the voltage follows the analog voltage output by the DAC. This point will hereinafter be explained in detail.
C-2. Operation of Capacitive Load Driving Circuit
In the case in which the drive voltage (the analog voltage output by the DAC) to be applied to the load 50 increases, the load driving circuit 100 of the second embodiment operates in the completely the same manner as in the first embodiment described above using
In contrast, in the case in which the drive voltage (the analog voltage output by the DAC) to be applied to the load 50 decreases, the gate selector circuit 140 switches OFF all of the switches SN1 through SN4, and at the same time, switches ON either one of the switches SPO through SP3 in accordance with the drive voltage. For example, the case of reducing the drive voltage from E2 towards E1 will be considered. In the case in which the drive voltage is within the range of E1 through E2, and is lowered, the gate selector 140 switches ON the switch SP1. Then, the output of the operational amplifier Opamp is input to the gate electrode of the transistor PIr1 to form a channel by the hole inside the transistor PIr1, thereby electrically connecting the load 50 and the power supply E1 to each other. Since the voltage value E2 has been applied to the load 50, the electrical power stored in the load 50 is refluxed to the power supply E1. Then, in the case in which the power supply E1 is the power supply such as a secondary battery capable of storing the electrical power supplied externally, it is possible to drive the load 50 using the stored electrical power, and therefore, it becomes possible to significantly reduce the power consumption.
Further, the lower the voltage applied to the gate electrode of the transistor PIr1 becomes, the smaller the equivalent resistance value of the transistor PIr1 becomes. Therefore, the negative feedback circuit is formed by inputting the analog voltage (the target voltage to be applied to the load 50) output by the DAC and the drive voltage actually applied to the load 50 into the operational amplifier Opamp, and applying the output of the operational amplifier Opamp to the gate electrode, thereby making it possible to control the drive voltage applied to the load 50. For example, in the case in which the drive voltage applied to the load 50 is higher than the target voltage output by the DAC, since the output of the operational amplifier Opamp decreases, the equivalent resistance value of the transistor PTr1 is reduced. As a result, the drive voltage applied to the load 50 is reduced to come closer to the target voltage output by the DAC.
In
When the drive voltage of the load 50 becomes lower than the voltage value E1, the switch SP1 is switched OFF and the switch SPO is switched ON using the gate selector circuit 140. As a result, the negative feedback circuit (the circuit illustrated with the thick solid lines in
As described above, also in the load driving circuit 100 of the second embodiment, the range of the voltage, which can be applied to the load 50, is divided into four voltage ranges, namely 0 (V) through E1, E1 through E2, E2 through E3, and E3 through E4, and the power supplies E1 through E4 having charge of the respective voltage ranges have been set previously. Further, in the case of raising the drive voltage to be applied to the load 50, the power supply having charge of the voltage range is connected to the load 50, and the drive voltage is applied to the load 50 while performing the negative feedback control. For example, it is arranged that if the drive voltage is in between the voltage value E1 and the voltage value E2, the load 50 is driven using the power supply E2 having charge of the voltage range of E1 through E2. In contrast, in the case in which the drive voltage to be applied to the load 50 is to be reduced, the power supply having charge of the voltage range one step lower than the present voltage is coupled to the load 50. Then, the drive voltage applied to the load 50 is reduced by executing the negative feedback control while refluxing the electrical power stored in the load 50 to the power supply. For example, in the case in which the drive voltage is in between the voltage value E1 and the voltage value E2, the power supply E1 having charge of the voltage range of 0 (V) through E1 is coupled to the load 50, thereby storing the electrical power of the load 50 in the power supply E1. According to this operation, it is possible to reduce the power consumption when driving the load 50. In particular in the case in which the power supplies E1 through E4 are the power supplies such as secondary batteries or capacitors capable of storing at least a part of the electrical power supplied from the outside, it becomes possible to further significantly reduce the power consumption. The reason therefor will hereinafter be explained.
Then, when reducing the drove voltage from E4, firstly the switch SN4 is switched OFF, and then the switch SP3 is switched ON. Then, the electrical power stored in the load 50 is refluxed to the power supply E3 via the transistor PTr3, and the drive voltage applied to the load 50 is reduced in conjunction therewith. In this occasion, if the power supply E3 is a power supply capable of storing the electrical power supplied, the electrical power refluxed from the load 50 is to be stored in the power supply E3. When the drive voltage of the load 50 is reduced to the voltage value E3, the electrical power of the load 50 is then refluxed to the power supply E2 via the transistor PTr2 by switching OFF the switch SP3 and switching ON the switch SP2. Further, when the drive voltage of the load 50 is reduced to the voltage value E2, the electrical power of the load 50 is refluxed to the power supply E1 via the transistor PTr1 by switching OFF the switch SP2 and switching ON the switch SP1. If the power supply E2 or the power supply E1 is capable of storing the electrical power, the electrical power refluxed from the load 50 is stored in the power supply E2 or the power supply E1. When the drive voltage is reduced to the voltage value E1, the switch SP1 is switched OFF and the switch SPO is switched ON at the end. Then, the electrical power of the load 50 is released to the ground via the transistor PTrO, and the drive voltage applied to the load 50 is reduced to 0(V) in conjunction therewith.
Further, since the load 50 is the capacitive load, in the load driving circuit 100 of the second embodiment, the power consumption can further significantly be reduced by adopting the power supply, such as a secondary battery, capable of storing the electrical power supplied from the outside as the power supplies E1 through E3 to which the electrical power is refluxed from the load 50. The arrow illustrated with thick solid lines in
By storing the electrical power from the load 50 in the power supplies when reducing the drive voltage as described above, the electrical power thus stored can be used when subsequently raising the drive voltage. For example, when subsequently raising the drive voltage in the range of 0(V) through E1, the electrical power is to be supplied from the power supply E1. In this case, by supplying the electrical power having been refluxed from the load 50 and stored, the drive voltage of the load 50 can be raised without substantially supplying any new electrical power. Since the electrical power from the load 50 is similarly stored in the power supplies E2 and E3, when raising the drive voltage in the range of E1 through E2, and when further raising the drive voltage in the range of E2 through E3, by supplying the load 50 with the electrical power having been stored in the power supplies E2 and E3, the drive voltage applied to the load 50 can be raised without substantially supplying any new electrical power. In the result, by storing the electrical power refluxed from the load 50 in the power supplies, it becomes possible to apply the drive voltage without supplying new electrical power providing the drive voltage is in a range of 0(V) through E3, and as a result, it becomes possible to significantly reduce the power consumption.
It should be noted that the explanations are presented hereinabove assuming that the load driving circuit 100 is provided with the four power supplies E1 through E4. However, by providing a larger number of power supplies, and more finely dividing the range of the voltage applied to the load 50, it is possible to expand the range of the drive voltage, which can be applied to the load 50 without supplying new electrical power. As a result, it becomes possible to more significantly reduce the power consumption. Further, similarly to the case with the first embodiment, also in the load driving circuit 100 of the second embodiment, it is also possible to apply the negative drive voltage or apply the drive voltage varying from a negative value to a positive value to the load 50.
Besides the various types of embodiments explained hereinabove, some modified examples can be considered. Hereinafter, these modified examples will briefly be explained.
In the various types of embodiments described above, the explanations are presented assuming that either of the power supplies E1 through E4 always generates the electrical power with a stable voltage value. However, there exist power supplies, such as capacitors, having the voltage value dropping as the electrical power is supplied, or power supplies, such as secondary batteries, not necessarily generating the electrical power with a stable voltage value. Further, there can be caused the case in which it is difficult to supply the electrical power with a stable voltage value because the electrical power to be supplied to the load 50 is too much in comparison with the capacity of the power supply. In such a case, it is also possible to monitor the value of the voltage generated by each of the power supplies, and switch the switches SN1 through SN4 or the switches SPO through SP3 so that the power supply generating the voltage with the optimum value is coupled to the load 50 in accordance with the drive voltage to be applied to the load 50.
Further, in the various types of embodiments described above, the explanations are presented assuming that the drive voltage applied to the load 50 is directly input to the operational amplifier Opamp to perform the negative feedback control. However, it is also possible to input the drive voltage into the operational amplifier Opamp after once dividing the drive voltage instead of inputting the drive voltage directly into the operational amplifier Opamp.
Although the various types of load driving circuits are explained hereinabove, the invention is not limited to the entire embodiments described above, but can be put into practice in various forms within the scope or spirit of the invention.
For example, since so-called inkjet printers emit jets of ink by driving piezoelectric elements as capacitive loads, the various types of load driving circuit 100 described above can preferably be used as the load driving circuit for driving the piezoelectric element. Alternatively, since liquid crystal panels also have large amount of parasitic capacitance generated therein, and are a type of capacitive load, the various types of load driving circuits 100 described above can preferably be used for the driving circuit of the liquid crystal panel.
The entire disclosure of Japanese Patent Application No. 2008-153907 filed on Jun. 12, 2008 is expressly incorporated by reference herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-153907 | Jun 2008 | JP | national |
This application is a continuation of U.S. patent application Ser. No. 12/483,077, filed Jun. 11, 2009. The foregoing application is incorporated herein by reference. U.S. patent application Ser. No. 12/483,077 claims priority to Japanese application 2008-153907, filed Jun. 12, 2008.
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| 52-110454 | Sep 1977 | JP |
| 05-088763 | Apr 1993 | JP |
| 07-005941 | Jan 1995 | JP |
| 07-130484 | May 1995 | JP |
| 07-170676 | Jul 1995 | JP |
| 09-023643 | Jan 1997 | JP |
| 10-111723 | Apr 1998 | JP |
| 10-293617 | Nov 1998 | JP |
| 2002-281770 | Sep 2002 | JP |
| 2003-285441 | Oct 2003 | JP |
| 2003-323220 | Nov 2003 | JP |
| 2006-246682 | Sep 2006 | JP |
| Number | Date | Country | |
|---|---|---|---|
| 20110298291 A1 | Dec 2011 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12483077 | Jun 2009 | US |
| Child | 13211110 | US |
