A circuit that uses an analog switch to switch an externally-attached resistor to change a magnitude of a reference electric current has been proposed.
PTL 1: Japanese Unexamined Patent Application Publication (Published Japanese Translation of PCT Application) No. JP 2006-65242
In such electric current control circuits, improvement of performance has been demanded.
It has been demanded to provide an electric current control circuit having proper performance.
An electric current control circuit according to an embodiment of the present disclosure includes: an amplifier including a first inputter, a second inputter, and an outputter; a first resistance element and a second resistance element; a first switch provided between the first resistance element and the second inputter; a second switch provided between the second resistance element and the second inputter; a third switch and a fourth switch electrically coupled to the outputter; a first transistor provided between the first resistance element and a first terminal, the first transistor being to be inputted with an output voltage of the outputter via the third switch; and a second transistor provided between the second resistance element and the first terminal, the second transistor being to be inputted with an output voltage of the outputter via the fourth switch.
A control device according to the embodiment of the present disclosure includes: a light emitting element; and an electric current control circuit configured to control supplying of an electric current to the light emitting element. The electric current control circuit includes: an amplifier including a first inputter, a second inputter, and an outputter; a first resistance element and a second resistance element; a first switch provided between the first resistance element and the second inputter; a second switch provided between the second resistance element and the second inputter; a third switch and a fourth switch electrically coupled to the outputter; a first transistor provided between the first resistance element and the light emitting element, the first transistor being to be inputted with an output voltage of the outputter via the third switch; and a second transistor provided between the second resistance element and the light emitting element, the second transistor being to be inputted with an output voltage of the outputter via the fourth switch.
A display device according to the embodiment of the present disclosure includes: a plurality of light emitting elements; and an electric current control circuit configured to control supplying of an electric current to the light emitting elements. The electric current control circuit includes: an amplifier including a first inputter, a second inputter, and an outputter; a first resistance element and a second resistance element; a first switch provided between the first resistance element and the second inputter; a second switch provided between the second resistance element and the second inputter; a third switch and a fourth switch electrically coupled to the outputter; a first transistor provided between the first resistance element and each of the light emitting elements, the first transistor being to be inputted with an output voltage of the outputter via the third switch; and a second transistor provided between the second resistance element and each of the light emitting elements, the second transistor being to be inputted with an output voltage of the outputter via the fourth switch.
In the following, an embodiment of the present disclosure will be described in detail with reference to the drawings. It is to be noted that description will be given in the following order.
The control device 1 includes the light emitting element 110. The light emitting element 110 is, for example, a light emitting diode (LED). Furthermore, the control device 1 includes, as illustrated in
The signal controller 101 is a signal control circuit, and is configured to perform signal processing. Note that the signal controller 101 and the electric current controller 102 may be integrated with each other.
The signal controller 101 is configured to control each component of the control device 1. The signal controller 101 controls, for example, operation of the electric current controller 102. The signal controller 101 generates and outputs, to the electric current controller 102, a signal regarding an electric current for the light emitting element 110 (hereinafter referred to as an electric current setting signal). The signal controller 101 generates, for example, as an electric current setting signal, a digital signal regarding a magnitude of an electric current to be supplied to the light emitting element 110. An electric current setting signal is a signal indicating a setting value of an electric current for the light emitting element 110, and is also referred to as a signal indicating a gradation.
The signal controller 101 may receive a clock signal provided externally and data that instructs an operation mode, and, furthermore, may output data of internal information of the control device 1, for example. Furthermore, pulse signals, which on-off controls each switch in the electric current controller 102, clock signals, and other signals are supplied to the electric current controller 102, for example.
The electric current controller 102 is configured to control an electric current for the light emitting element 110. The electric current controller 102 is an electric current control circuit, and includes a digital-to-analog converter (DA converter or DAC) and a plurality of circuits including an amplifier circuit, for example. The electric current controller 102 is configured to supply an electric current to the light emitting element 110 to control the light emitting element 110.
The electric current controller 102 is, for example, provided per the light emitting element 110. The electric current controller 102 may supply an electric current for driving the light emitting element 110 to the light emitting element 110 to control light emission by the light emitting element 110. The electric current controller 102 is a driver configured to control driving of the light emitting element 110, and is also referred to as a driver integrated circuit (IC) (a driver circuit).
The signal controller 101 and the electric current controller 102 may be formed on an identical substrate. The drive circuit (chip) 100 provided with the signal controller 101 and the electric current controller 102 is, for example, an element including a semiconductor substrate (also referred to as an electric current control element). The drive circuit 100 including the signal controller 101 and the electric current controller 102 is, for example, as schematically illustrated in
Note that the signal controller 101 and the electric current controller 102 may be provided per a plurality of light emitting elements 110. For example, as illustrated in the example in
Furthermore, the electric current controller 102 includes a plurality of resistance elements R1 (in
The DA converter 20 is configured to generate a voltage in accordance with a digital signal to be inputted. The DA converter 20 is inputted with an electric current setting signal from the signal controller 101. The DA converter 20 converts the electric current setting signal that is a digital signal into an analog signal. In the example illustrated in
The amplifier 50 includes, for example, an amplifier circuit that includes an inputter 51a, an inputter 51b, and an outputter 52 and that is configured to amplitude a signal. In the example illustrated in
The inputter 51b in the amplifier 50 is a second input terminal. The inputter 51b is electrically coupled to the switch SW1a to the switch SW1d. Note that, in the example illustrated in
The switch SW1a is provided between the resistance element R1a and the inputter 51b in the amplifier 50. An end of the switch SW1a is coupled to the resistance element R1a and the transistor M1a. Another end of the switch SW1a is coupled to the inputter 51b. The switch SW1a is configured to electrically couple a node N1 coupling the resistance element R1a and the transistor M1a to the inputter 51b. The switch SW1a electrically couples or decouples the node N1 and the inputter 51b.
The switch SW1b is provided between the resistance element R1b and the inputter 51b in the amplifier 50. An end of the switch SW1b is coupled to the resistance element R1b and the transistor M1b. Another end of the switch SW1b is coupled to the inputter 51b. The switch SW 1b is configured to electrically couple a node N2 coupling the resistance element R1b and the transistor M1b to the inputter 51b. The switch SW1b electrically couples or decouples the node N2 and the inputter 51b.
The switch SW1c is provided between the resistance element R1c and the inputter 51b in the amplifier 50. An end of the switch SW1c is coupled to the resistance element R1c and the transistor M1c. Another end of the switch SW1c is coupled to the inputter 51b. The switch SW 1c is configured to electrically couple a node N3 coupling the resistance element R1c and the transistor M1c to the inputter 51b. The switch SW1c electrically couples or decouples the node N3 and the inputter 51b.
The switch SW1d is provided between the resistance element R1d and the inputter 51b in the amplifier 50. An end of the switch SW1d is coupled to the resistance element R1d and the transistor M1d. Another end of the switch SW1d is coupled to the inputter 51b. The switch SW 1d is configured to electrically couple a node N4 coupling the resistance element R1d and the transistor M1d to the inputter 51b. The switch SW1d electrically couples or decouples the node N4 and the inputter 51b. The switches SW1a, SW1b, SW1c, and SW1d each include a transistor.
The switch SW2a is provided between the outputter 52 in the amplifier 50 and the transistor M1a. An end of the switch SW2a is coupled to the outputter 52. Another end of the switch SW2a is coupled to a gate of the transistor M1a. The switch SW2a is configured to electrically couple the outputter 52 and the gate of the transistor M1a. The switch SW2a electrically couples or decouples the outputter 52 and the gate of the transistor M1a.
The switch SW2b is provided between the outputter 52 in the amplifier 50 and the transistor M1b. An end of the switch SW2b is coupled to the outputter 52. Another end of the switch SW2b is coupled to a gate of the transistor M1b. The switch SW2b is configured to electrically couple the outputter 52 and the gate of the transistor M1b. The switch SW2b electrically couples or decouples the outputter 52 and the gate of the transistor M1b.
The switch SW2c is provided between the outputter 52 in the amplifier 50 and the transistor M1c. An end of the switch SW2c is coupled to the outputter 52. Another end of the switch SW2c is coupled to a gate of the transistor M1c. The switch SW2c is configured to electrically couple the outputter 52 and the gate of the transistor M1c. The switch SW2c electrically couples or decouples the outputter 52 and the gate of the transistor M1c.
The switch SW2d is provided between the outputter 52 in the amplifier 50 and the transistor M1d. An end of the switch SW2d is coupled to the outputter 52. Another end of the switch SW2d is coupled to a gate of the transistor M1d. The switch SW2d is configured to electrically couple the outputter 52 and the gate of the transistor M1d. The switch SW2d electrically couples or decouples the outputter 52 and the gate of the transistor M1d. The switches SW2a, SW2b, SW2c, and SW2d each include a transistor.
The resistance element R1a to the resistance element R1d are resistance bodies, and, as illustrated in
An end of the resistance element R1b is coupled to the transistor M1b and the switch SW1b. Another end of the resistance element R1b is coupled to the reference electric potential line. An end of the resistance element R1c is coupled to the transistor M1c and the switch SW1c. Another end of the resistance element R1c is coupled to the reference electric potential line. Furthermore, an end of the resistance element R1d is coupled to the transistor M1d and the switch SW1d. Another end of the resistance element R1d is coupled to the reference electric potential line.
The transistor M1a to the transistor M1d are metal-oxide-semiconductor (MOS) transistors (MOS field-effect transistors or MOSFETs) each having terminals for the gate, a source, and a drain, respectively. In the example illustrated in
One of the source and the drain of the transistor M1a is electrically coupled to the light emitting element 110 via the terminal 60. Another one of the source and the drain of the transistor M1a is coupled to the resistance element R1a and the switch SW1a. The gate of the transistor M1a is electrically coupled to the switch SW2a. Furthermore, one of the source and the drain of the transistor M1b is electrically coupled to the light emitting element 110 via the terminal 60. Another one of the source and the drain of the transistor M1b is coupled to the resistance element R1b and the switch SW1b. The gate of the transistor M1b is electrically coupled to the switch SW2b.
One of the source and the drain of the transistor M1c is electrically coupled to the light emitting element 110 via the terminal 60. Another one of the source and the drain of the transistor M1c is coupled to the resistance element R1c and the switch SW1c. The gate of the transistor M1c is electrically coupled to the switch SW2c. Furthermore, one of the source and the drain of the transistor M1d is electrically coupled to the light emitting element 110 via the terminal 60. Another one of the source and the drain of the transistor M1d is coupled to the resistance element R1d and the switch SW1d. The gate of the transistor M1d is electrically coupled to the switch SW2d.
The signal controller 101 (see
In the electric current controller 102, the amplifier 50 adjusts an electric current Iout flowing between the terminal 60 and the reference electric potential line to make a voltage at each of the nodes coupled to the inputter 51b in the amplifier 50 identical in voltage to the voltage VIN inputted to the inputter 51a. Therefore, the signal controller 101 switches each of the transistors and each of resistors coupled between the outputter 52 and the inputter 51b, making it possible to change the electric current Iout to be supplied to the light emitting element 110.
In the example illustrated in
As resistance elements coupled to the inputter 51b increase in number, among the resistance element R1a to the resistance element R1d, the electric current Iout that is possible to be supplied to the light emitting element 110 via the terminal 60 increases. Furthermore, the electric current Iout becomes an electric current having a magnitude in accordance with a voltage value of the voltage VIN generated in accordance with a value of an electric current setting signal.
Furthermore, the signal controller 101 may adjust a pulse width of a control signal to be supplied to each of the switches in the electric current controller 102 (for example, a high-level pulse width) to change a timing and a period of time of supplying an electric current to the light emitting element 110. The signal controller 101 and the electric current controller 102 are possible to use a pulse width modulation (PWM) method to control supplying of an electric current to the light emitting element 110.
In the present embodiment, it is possible to set coupling states of the resistance element R1a to the resistance element R1d and values of electric current setting signals to adjust an electric current to be supplied to the light emitting element 110 and to adjust brightness of light and a period of time of light emission by the light emitting element 110, for example. It is possible to adjust the resistance values of the resistance element R1a to the resistance element R1d by using an electric current to be supplied to the light emitting element 110, resolution (a number of bits) of the DA converter 20, and gradations, for example. The resistance element R1a to the resistance element R1d may have weighted resistance values to acquire desired gradation characteristics. The resistance element R1a to the resistance element R1d may have resistance values that are different from each other.
The resistance value of the resistance element R1a is 360Ω, and the resistance value of the resistance element R1b is 120Ω. The resistance value of the resistance element R1c is 90Ω, and the resistance value of the resistance element R1d is 45Ω. Furthermore, as illustrated in
The control device 1 has a plurality of operation modes where the coupling states of the switches in the electric current controller 102 are different from each other. The control device 1 has, for example, as the operation modes, a first electric current mode, a second electric current mode, a third electric current mode, and a fourth electric current mode. The signal controller 101 turns, in a case of the first electric current mode, for example, the switch SW1a and the switch SW2a to the on state, and the other switches to the off state, among the switches in the electric current controller 102 (the switch SW1a to the switch SW1d and the switch SW2a to the switch SW2d). In the first electric current mode, the electric current controller 102 is in a state where the transistor M1a is possible to supply the electric current Iout having a maximum value of 2.5 mA to the light emitting element 110.
In a case of the second electric current mode, the signal controller 101 turns the switch SW1a and the switch SW2a and the switch SW1b and the switch SW2b to the on state, and the other switches to the off state, among the switches in the electric current controller 102. In the second electric current mode, the electric current controller 102 is possible to cause the transistors M1a and M1b to supply the electric current Iout having a maximum value of 10 mA to the light emitting element 110.
In a case of the third electric current mode, the signal controller 101 turns the switches SW1a, SW1b, SW1c, SW2a, SW2b, and SW2c to the on state, and the other switches to the off state, among the switches in the electric current controller 102. In the third electric current mode, the electric current controller 102 is possible to cause the transistors M1a, M1b, and M1c to supply the electric current lout having a maximum value of 20 mA to the light emitting element 110.
Furthermore, in a case of the fourth electric current mode, the signal controller 101 turns all the switches in the electric current controller 102, that is, the switches SW1a to SW1d and SW2a to SW2d to the on state. In the fourth electric current mode, the electric current controller 102 is possible to cause the transistors M1a to M1d to supply the electric current Iout having a maximum value of 40 mA to the light emitting element 110. As described above, switching of the operation modes makes it is possible to supply the electric current Iout having a magnitude of up to 40 mA to the light emitting element 110, for example, making it possible to achieve a wide dynamic range.
In the present embodiment, the resistance elements used to generate a low electric current, that is, an electric current for a low brightness region, which is supplied to the light emitting element 110, have relatively high resistance values. As the resistance values are weighted in the example illustrated in
Thereby, in the control device 1 according to the present embodiment, it is possible to suppress occurrence of deviation in the electric current value of the electric current Iout, which may occur due to the offset voltage of the amplifier 50. Even in a case of a low electric current range (a low brightness range) within which a low electric current is supplied to the light emitting element 110, it is possible to accurately generate and supply, to the light emitting element 110, the electric current Iout that is a low electric current, making it possible to perform fine gradation expression. Even in the low electric current range, it is possible to achieve multi-gradations. In a case where the control device 1 is applied as a back light control device or a display device, for example, it is possible to achieve high-definition image display.
As described above, in the present embodiment, it is possible to reduce errors in the electric current lout, making it possible to achieve characteristics similar to target gamma characteristics. As illustrated in the example in
In the control device 1, as described above, switching the coupling states of the switches in the electric current controller 102 makes it possible to perform fine adjustments on the electric current Iout. Therefore, it is possible to use the DA converter 20 having relatively low resolution, making it possible to reduce an area of the DA converter 20, compared with a case where electric current control for the light emitting element 110 is performed only on the basis of control of an output voltage of the DA converter 20. It is possible to suppress an increase in chip area, making it possible to suppress an increase in cost of manufacturing the control device 1. Furthermore, it is possible to reduce electric power to be consumed.
Furthermore, in the present embodiment, the switches SW1 (the switch SW1a to the switch SW1d) are coupled to the inputter 51b in the amplifier 50 having high input impedance, and thus provided on high impedance routes. The switches SW1 are disposed on a feedback loop for the amplifier 50. Therefore, it is possible to avoid addition of parasitic resistance for the switches on the routes between the terminal 60 and the reference electric potential line, making it possible to suppress errors in the electric current lout. It is possible to prevent an increase in electric power to be consumed, which may occur due to negative effects of parasitic resistance.
An electric current control circuit (the electric current controller 102) according to the present embodiment includes: an amplifier (the amplifier 50) including a first inputter, a second inputter, and an outputter; a first resistance element and a second resistance element (for example, the resistance element R1a and the resistance element R1b); a first switch (the switch SW1a) provided between the first resistance element and the second inputter; a second switch (the switch SW1b) provided between the second resistance element and the second inputter; a third switch and a fourth switch (the switch SW2a and the switch SW2b) electrically coupled to the outputter; a first transistor (the transistor M1a) provided between the first resistance element and a first terminal (the terminal 60), the first transistor being to be inputted with an output voltage of the outputter via the third switch; and a second transistor (the transistor M1b) provided between the second resistance element and the first terminal, the second transistor being to be inputted with an output voltage of the outputter via the fourth switch.
The electric current control circuit (the electric current controller 102) according to the present embodiment is provided with the switches SW1a, SW1b, SW2a, and SW2b, the transistors M1a and M1b, and the resistance elements R1a and R1b. It is possible to control the switches SW1a, SW1b, SW2a, and SW2b to accurately generate an electric current for the light emitting element, making it possible to achieve a high-performance electric current control circuit.
Next, modification examples of the present disclosure will now be described herein. Like reference numerals designate identical or similar components in the embodiment described above, and some descriptions are thus appropriately omitted below.
Although, in the embodiment described above, the configuration example of the electric current controller 102 has been described, numbers of the switches SW1 and SW2 and a number and the resistance values of the resistance elements R in the electric current controller 102, for example, are not limited to the illustrated example.
As an example, as illustrated in the example in
Furthermore, as another example, as illustrated in the example in
Although the present disclosure has been described with reference to the embodiment and the modification examples, the present technique is not limited to the embodiment and the modification examples described above, but may be modified in a wide variety of ways. For example, although the modification examples described above have been described as modification examples of the embodiment described above, it is possible to appropriately combine the configurations of the modification examples.
Note that the effects described in the specification are mere examples. The effects of the technique are not limited to the effects described in the specification. There may be any other effects than those described herein. Furthermore, it is possible that the present disclosure has configurations described below.
(1)
An electric current control circuit including:
The electric current control circuit described in (1), in which
The electric current control circuit described in (1) or (2), in which
The electric current control circuit described in any one of (1) to (3), in which
The electric current control circuit described in any one of (1) to (4), in which
The electric current control circuit described in any one of (1) to (5),
The electric current control circuit described in any one of (1) to (6), in which
The electric current control circuit described in any one of (1) to (7), in which the first resistance element and the second resistance element have resistance values different from each other.
(9)
The electric current control circuit described in any one of (1) to (8), further including a light emitting element electrically coupled to the first terminal.
(10)
The electric current control circuit described in any one of (1) to (9), further including:
A control device including:
The control device described in (11), further including:
A display device including:
The display device described in (13), further including:
The present application claims the benefit of Japanese Priority Patent Application JP 2022-045967 filed with the Japan Patent Office on Mar. 22, 2022, the entire contents of which are incorporated herein by reference.
It should be understood by those skilled in the art that various modifications, combinations, sub-combinations, and alterations may occur depending on design requirements and other factors insofar as they are within the scope of the appended claims or the equivalents thereof.
Number | Date | Country | Kind |
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2022-045967 | Mar 2022 | JP | national |
The present disclosure relates to an electric current control circuit, a control device, and a display device.
Filing Document | Filing Date | Country | Kind |
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PCT/JP2023/004420 | 2/9/2023 | WO |