Drive circuit

Abstract

According to the present invention, a bridge circuit (30) alternately applies a first voltage and a second voltage of mutually different polarities to a capacitor (200). A diode (41) is connected to one end of the capacitor (200). A diode (42) is connected to the other end of the capacitor (200). A capacitor (50) is connected to the diode (41) and the diode (42). A control circuit (60) controls a plurality of switching elements provided to the bridge circuit (30), such that when the voltage applied to the capacitor (200) transitions from the first voltage to the second voltage, the charge accumulated in the capacitor (200) moves to the capacitor (50) via the diode (41), and when the voltage applied to the capacitor (200) transitions from the second voltage to the first voltage, the charge accumulated in the capacitor (200) moves to the capacitor (50) via the diode (42).

Description

[Technical field]

[0001] The present disclosure relates to a drive circuit. [Background technology]

[0002] A driving circuit for driving a capacitive load is known. The capacitive load is, for example, a piezoelectric element including a piezoelectric body and two electrodes sandwiching the piezoelectric body. The capacitive load is incorporated in various devices that generate sound or vibration, such as a game controller, a smartphone, a piezoelectric buzzer, and a liquid ejection device in an inkjet printer.

[0003] In order to increase the sound pressure during sound generation or to increase the amount of displacement during vibration, it is necessary to increase the capacity of the capacitive load. However, if the capacity of the capacitive load is large, the electrical energy stored in the capacitive load is also large, and the electrical energy converted into thermal energy is also large, resulting in high power consumption. For this reason, a technology is desired that effectively utilizes the electrical energy stored in the capacitive load to reduce power consumption.

[0004] For example, Patent Document 1 describes a liquid ejection device having a liquid ejection head that ejects droplets from a nozzle opening by utilizing pressure caused by the displacement of a piezoelectric element. In this liquid ejection device, in order to reduce the power consumed by the charge pump, the charge accumulated in the piezoelectric element, which is a capacitive load, is transferred to a capacitor in the charge pump. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5083546 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the liquid ejection device described in Patent Document 1, the charge stored in the piezoelectric element is transferred to a capacitor in the charge pump over multiple stages. Therefore, in the liquid ejection device described in Patent Document 1, the electric energy stored in the piezoelectric element cannot be used efficiently, and the power consumption when driving the capacitive load is not reduced significantly. For this reason, a technology for reducing the power consumption when driving the capacitive load is desired.

[0007] The present disclosure has been made in consideration of the above-mentioned problems, and has an object to reduce power consumption when driving a capacitive load. [Means for solving the problem]

[0008] In order to solve the above problem, a drive circuit according to an embodiment of the present disclosure includes: 1. A drive circuit for driving a capacitive load, comprising: a bridge circuit including a plurality of switch elements, and configured to alternately apply a first voltage and a second voltage having mutually opposite polarities to the capacitive load; a first rectifying element connected to one end of the capacitive load; a second rectifying element connected to the other end of the capacitive load; a storage element connected to the first rectifying element and the second rectifying element; and a control circuit that controls the multiple switch elements so that, when the voltage applied to the capacitive load transitions from the first voltage to the second voltage, the charge stored in the capacitive load transfers to the storage element via the first rectifier element, and, when the voltage applied to the capacitive load transitions from the second voltage to the first voltage, the charge stored in the capacitive load transfers to the storage element via the second rectifier element. Effect of the Invention

[0009] According to the drive circuit having the above configuration, it is possible to reduce power consumption when driving a capacitive load. [Brief description of the drawings]

[0010] [Figure 1] Circuit diagram of a drive circuit according to the first embodiment [Diagram 2] FIG. 1 is a diagram showing a switch change order according to the first embodiment; [Diagram 3] 1A and 1B are diagrams showing changes over time in signals of various parts of the drive circuit according to the first embodiment, in which (A) is a diagram showing changes over time in VG1, (B) is a diagram showing changes over time in VG2, (C) is a diagram showing changes over time in VG3, (D) is a diagram showing changes over time in VG4, (E) is a diagram showing changes over time in I1, and (F) is a diagram showing changes over time in I2. [Figure 4] Circuit state diagram at T1 [Diagram 5] Diagram of the circuit state at T2 [Figure 6] Circuit state diagram at T3 [Figure 7] Circuit state diagram for T4 [Figure 8] Circuit state diagram for T5 [Figure 9] Circuit state diagram for T6 [Figure 10] Circuit state diagram at T7 [Figure 11] Circuit state diagram for T8 [Figure 12] Circuit diagram of a drive circuit according to a second embodiment [Figure 13] FIG. 11 is a circuit diagram of a first voltage conversion circuit and a second voltage conversion circuit according to a third embodiment; [Figure 14] FIG. 13 is a diagram showing a switch change order according to the fourth embodiment. [Figure 15] 11A and 11B are diagrams showing changes over time in signals of various parts of a drive circuit according to a fourth embodiment, in which (A) is a diagram showing changes over time in VG1, (B) is a diagram showing changes over time in VG2, (C) is a diagram showing changes over time in VG3, (D) is a diagram showing changes over time in VG4, (E) is a diagram showing changes over time in I1, and (F) is a diagram showing changes over time in I2. [Figure 16] Circuit diagram of a drive circuit according to a fifth embodiment DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, a power transmission system according to an embodiment of the technology disclosed herein will be described with reference to the drawings. In the following embodiments, the same components are denoted by the same reference numerals. In addition, the size ratio and shape of the components shown in each drawing are not necessarily the same as those in the actual implementation.

[0012] (Embodiment 1) First, the configuration of a drive circuit 100 according to this embodiment will be described with reference to Fig. 1. The drive circuit 100 is a circuit that drives a capacitive load with an AC current. In other words, the drive circuit 100 is a circuit that applies positive and negative voltages alternately to the capacitive load. In this embodiment, the capacitive load is a piezoelectric element that includes a piezoelectric body and two electrodes that sandwich the piezoelectric body. The piezoelectric element is incorporated and used in various devices that generate sound or vibration, such as game controllers, smartphones, piezoelectric buzzers, and liquid ejection devices in inkjet printers.

[0013] In general, electrical energy stored in a capacitive load is converted into thermal energy and consumed. However, it is desirable to effectively utilize the electrical energy stored in the capacitive load as electrical energy rather than consuming it as thermal energy. Therefore, the driving circuit 100 according to the present embodiment reduces the power consumption of the driving circuit 100 as a whole by storing the electrical energy stored in the capacitive load in a power storage element and utilizing it.

[0014] 1, the drive circuit 100 includes a power supply 10, a power supply 20, a load 23, a bridge circuit 30, a diode 41, a diode 42, a capacitor 50, a control circuit 60, a diode 71, and a diode 72. A capacitor 200 that is the drive target of the drive circuit 100 corresponds to the capacitance of a piezoelectric element that is a capacitive load.

[0015] The power supply 10 is a power supply that supplies DC power. The power supply 10 supplies power for driving the piezoelectric element. The power supply voltage V1 of the power supply 10 is a relatively high voltage. In this embodiment, V1 is 15V. The power supply 10 includes a high potential side output terminal 11 and a low potential side output terminal 12. The high potential side output terminal 11 is an output terminal that is set to a higher potential than the low potential side output terminal 12. V1 is applied between the high potential side output terminal 11 and the low potential side output terminal 12. In this embodiment, the high potential side output terminal 11 is set to V1, and the low potential side output terminal 12 is grounded and set to 0V. The power supply 10 is an example of a first power supply.

[0016] The power supply 20 is a power supply provided separately from the power supply 10, and supplies DC power. The power supply 20 supplies power for driving the load 23. The power supply voltage V2 of the power supply 20 may be the same voltage as V1 or may be a voltage different from V1. In the present embodiment, V2 is the same voltage as V1, which is 15V. The power supply 20 includes a high potential side output terminal 21 and a low potential side output terminal 22. The high potential side output terminal 21 is an output terminal set to a higher potential than the low potential side output terminal 22. V2 is applied between the high potential side output terminal 21 and the low potential side output terminal 22. In the present embodiment, the high potential side output terminal 21 is set to V2, and the low potential side output terminal 22 is grounded and set to 0V. The power supply 20 is an example of a second power supply.

[0017] The load 23 is a load that receives power from the power source 20, and is a load other than the piezoelectric element shown as the capacitor 200 in Fig. 1. The load 23 may be another piezoelectric element or the control circuit 60. When the drive circuit 100 drives a plurality of piezoelectric elements, the other piezoelectric element is a piezoelectric element other than the piezoelectric element shown as the capacitor 200 in Fig. 1 among the plurality of piezoelectric elements.

[0018] The bridge circuit 30 supplies the power supplied from the power source 10 to the capacitor 200. The bridge circuit 30 includes a switch element 31, a switch element 32, a switch element 33, and a switch element 34, and is a circuit that alternately applies a first voltage and a second voltage of mutually opposite polarities to the capacitor 200, which is a capacitive load. The bridge circuit 30 is controlled by a control circuit 60. In this embodiment, the switch elements 31, 32, 33, and 34 are N (Negative) channel type MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors). The switch elements 31, 32, 33, and 34 are controlled by a gate drive signal supplied from the control circuit 60.

[0019] The switch element 31 is connected between the high potential side output terminal 11 of the power supply 10 and one end of the capacitor 200. The switch element 32 is connected between the low potential side output terminal 12 of the power supply 10 and one end of the capacitor 200. The switch element 33 is connected between the high potential side output terminal 11 of the power supply 10 and the other end of the capacitor 200. The switch element 34 is connected between the low potential side output terminal 12 of the power supply 10 and the other end of the capacitor 200.

[0020] The switch element 31 includes a parasitic diode 35 that allows a current to flow from the source of the switch element 31 to the drain of the switch element 31. The switch element 32 includes a parasitic diode 36 that allows a current to flow from the source of the switch element 32 to the drain of the switch element 32. The switch element 33 includes a parasitic diode 37 that allows a current to flow from the source of the switch element 33 to the drain of the switch element 33. The switch element 34 includes a parasitic diode 38 that allows a current to flow from the source of the switch element 34 to the drain of the switch element 34. The switch element 31 is an example of a first switch element. The switch element 32 is an example of a second switch element. The switch element 33 is an example of a third switch element. The switch element 34 is an example of a fourth switch element.

[0021] Diode 41 is a rectifying element connected to one end of capacitor 200, which is a capacitive load. Diode 42 is a rectifying element connected to the other end of capacitor 200, which is a capacitive load. Diode 41 and diode 42 serve to supply the charge stored in capacitor 200 to capacitor 50, which is a power storage element. Diode 41 is an example of a first rectifying element. Diode 42 is an example of a second rectifying element.

[0022] The capacitor 50 is a storage element connected to the diode 41 and the diode 42. The capacitor 50 is connected in parallel to the load 23 when viewed from the power source 20. The capacitor 50 temporarily stores the charge supplied from the capacitor 200, which is a capacitive load, and supplies the stored charge to the load 23. While the capacitor 50 supplies charge to the load 23, the power source 20 can supply less charge to the load 23, and the power consumption of the power source 20 is reduced. It is preferable that the capacitance of the capacitor 50 is equal to or greater than the capacitance of the capacitor 200. In this embodiment, the capacitance of the capacitor 50 is ten times the capacitance of the capacitor 200. In this case, when the capacitor 50 is charged with the charge supplied from the capacitor 200, the voltage across the capacitor 50 is prevented from rising excessively. The capacitor 50 is an example of a storage element.

[0023] The control circuit 60 controls the bridge circuit 30 so that a first voltage and a second voltage are applied to the capacitor 200. The control circuit 60 controls the bridge circuit 30 by supplying gate drive signals to each of the switch elements 31, 32, 33, and 34. The first voltage is a voltage slightly lower than V1. The second voltage is a voltage approximately equal in magnitude to the first voltage and has a polarity opposite to that of the first voltage. In this embodiment, the first voltage is a positive voltage, and the second voltage is a negative voltage.

[0024] In this embodiment, applying a voltage to capacitor 200 such that the potential at one end of capacitor 200 is higher than the potential at the other end of capacitor 200 is referred to as applying a positive voltage to capacitor 200. Also, applying a voltage to capacitor 200 such that the potential at one end of capacitor 200 is lower than the potential at the other end of capacitor 200 is referred to as applying a negative voltage to capacitor 200. Also, applying a positive voltage to capacitor 200 is referred to as driving capacitor 200 in the positive direction, and applying a negative voltage to capacitor 200 is referred to as driving capacitor 200 in the negative direction.

[0025] Here, when bridge circuit 30 is in a first state, a first voltage is applied to capacitor 200, and when bridge circuit 30 is in a second state, a second voltage is applied to capacitor 200. The first state is a state in which a first pair, which is a pair of switch element 31 and switch element 34, is ON, and a second pair, which is a pair of switch element 32 and switch element 33, is OFF. The second state is a state in which the first pair is OFF, and the second pair is ON. Note that ON means that the drain and source are conductive, and OFF means that the drain and source are not conductive.

[0026] In the control of a general bridge circuit 30, each switch element is AC driven so that the first pair and the second pair are alternately turned ON / OFF. In the control of the general bridge circuit 30, the electric energy stored in the capacitor 200 is not utilized but is consumed as heat energy. When the capacitive load is a piezoelectric buzzer, the scale of the output sound is adjusted by adjusting the frequency of the gate drive signal. For example, when a PFM (Pulse Frequency Modulation) modulated signal is used as the gate drive signal, various musical pieces can be reproduced. When the PFM modulated gate drive signal is at H level, the switch element is turned ON, and when the PFM modulated gate drive signal is at L level, the switch element is turned OFF.

[0027] In this embodiment, the switch element is an N-channel MOSFET. Therefore, the switch element is turned on when the gate voltage is higher than the source voltage by at least the gate threshold voltage. For example, when the control circuit 60 turns on the switch element 31, it supplies a gate drive signal of a voltage (e.g., V1) higher than the source voltage of the switch element 31 by at least the gate threshold voltage to the gate of the switch element 31. When the control circuit 60 turns on the switch element 32, it supplies a gate drive signal of a voltage (e.g., 3V) higher than the source voltage of the switch element 32 by at least the gate threshold voltage to the gate of the switch element 32.

[0028] Here, when bridge circuit 30 is controlled to repeat the first state and the second state, the electric energy stored in capacitor 200 is not utilized and is consumed as heat energy. Therefore, in the present embodiment, control circuit 60 provides an intermediate state between the first state and the second state in order to transfer the charge stored in capacitor 200 to capacitor 50 for utilization.

[0029] Specifically, control circuit 60 controls switch element 31, switch element 32, switch element 33, and switch element 34 so that when the voltage applied to capacitor 200 transitions from a first voltage to a second voltage, the charge stored in capacitor 200 transfers to capacitor 50 via diode 41, and when the voltage applied to capacitor 200 transitions from the second voltage to the first voltage, the charge stored in capacitor 200 transfers to capacitor 50 via diode 42.

[0030] Diodes 71 and 72 are rectifying elements that suppress a current from flowing back from capacitor 200 to power source 10 via bridge circuit 30. Diode 71 suppresses a charge from flowing from capacitor 200 to power source 10 via switch element 31. Diode 72 suppresses a charge from flowing from capacitor 200 to power source 10 via switch element 33. Diodes 71 and 72 are examples of rectifying elements.

[0031] Next, the switching order of each switch element by the control circuit 60 will be described with reference to Fig. 2 and Fig. 3. Fig. 2 shows the switch switching order according to this embodiment. As shown in Fig. 2, in this embodiment, the state of each switch element is switched so that the periods T1, T2, T3, T4, T5, T6, T7, and T8 occur in sequence and repeatedly.

[0032] A period T1 is a period during which switch element 31 and switch element 34 are ON, and switch element 32 and switch element 33 are OFF. A period T2 is a period during which switch element 31 is ON, and switch element 32, switch element 33, and switch element 34 are OFF. A period T3 is a period during which switch element 31 and switch element 33 are ON, and switch element 32 and switch element 34 are OFF. A period T4 is a period during which switch element 33 is ON, and switch element 31, switch element 32, and switch element 34 are OFF.

[0033] The period T5 is a period during which switch element 32 and switch element 33 are ON, and switch element 31 and switch element 34 are OFF. The period T6 is a period during which switch element 33 is ON, and switch element 31, switch element 32, and switch element 34 are OFF. The period T7 is a period during which switch element 31 and switch element 33 are ON, and switch element 32 and switch element 34 are OFF. The period T8 is a period during which switch element 31 is ON, and switch element 32, switch element 33, and switch element 34 are OFF.

[0034] FIG. 3 shows a timing chart illustrating the time change of signals of each part of the drive circuit 100 according to the present embodiment. FIG. 3(A) shows a voltage waveform illustrating the time change of VG1 which is the gate voltage of the switch element 31. FIG. 3(B) shows a voltage waveform illustrating the time change of VG2 which is the gate voltage of the switch element 32. FIG. 3(C) shows a voltage waveform illustrating the time change of VG3 which is the gate voltage of the switch element 33. FIG. 3(D) shows a voltage waveform illustrating the time change of VG4 which is the gate voltage of the switch element 34. FIG. 3(E) shows a current waveform illustrating the time change of I1 which is the current flowing from the capacitor 200 to the capacitor 50. FIG. 3(F) shows a current waveform illustrating the time change of I2 which is the current output by the power supply 20.

[0035] The period before t1 is T1. The period from t1 to t2 is T2. The period from t2 to t3 is T3. The period from t3 to t4 is T4. The period from t4 to t5 is T5. The period from t5 to t6 is T6. The period from t6 to t7 is T7. The period from t7 to t8 is T8. The period from t8 to t9 is T1. The period from t9 to t10 is T2. The period from t10 to t11 is T3. The period from t11 to t12 is T4. The period from t12 onwards is T5.

[0036] Up to t1, the control circuit 60 supplies a gate drive signal that turns switch element 31 ON to the gate of switch element 31, supplies a gate drive signal that turns switch element 32 OFF to the gate of switch element 32, supplies a gate drive signal that turns switch element 33 OFF to the gate of switch element 33, and supplies a gate drive signal that turns switch element 34 ON to the gate of switch element 34. V11 is the gate voltage that turns switch element 31 ON, and V12 is the gate voltage that turns switch element 31 OFF. V21 is the gate voltage that turns switch element 32 ON, and V22 is the gate voltage that turns switch element 32 OFF. V31 is the gate voltage that turns switch element 33 ON, and V32 is the gate voltage that turns switch element 33 OFF. V41 is the gate voltage that turns switch element 34 ON, and V42 is the gate voltage that turns switch element 34 OFF. For example, V11 and V31 are V1, V21 and V41 are 3V, and V12, V22, V32 and V42 are 0V.

[0037] First, at t1, the control circuit 60 supplies a gate drive signal to the gate of the switch element 34, which turns the switch element 34 OFF. Next, at t2, the control circuit 60 supplies a gate drive signal to the gate of the switch element 33, which turns the switch element 33 ON. At t2, the charge stored in the capacitor 200 moves to the capacitor 50, and I1 increases rapidly. Furthermore, after t2, charge is supplied from the capacitor 50 to the load 23, which reduces the charge supplied from the power source 20 to the load 23, and I2 decreases.

[0038] At t3, control circuit 60 supplies a gate drive signal to the gate of switch element 31 to turn OFF switch element 31. At t4, control circuit 60 supplies a gate drive signal to the gate of switch element 32 to turn ON switch element 32. After t4, charge stops moving from capacitor 200 to capacitor 50, and I1 becomes approximately 0. Furthermore, after t4, the charge supplied from capacitor 50 to load 23 decreases, so the charge supplied from power supply 20 to load 23 increases, and I2 increases.

[0039] At t5, the control circuit 60 supplies a gate drive signal to the gate of the switch element 32, which turns the switch element 32 OFF. Next, at t6, the control circuit 60 supplies a gate drive signal to the gate of the switch element 31, which turns the switch element 31 ON. At t6, the charge stored in the capacitor 200 moves to the capacitor 50, and I1 increases rapidly. Furthermore, after t6, charge is supplied from the capacitor 50 to the load 23, which reduces the charge supplied from the power source 20 to the load 23, and I2 decreases.

[0040] At t7, the control circuit 60 supplies a gate drive signal to the gate of the switch element 33 to turn the switch element 33 OFF. At t8, the control circuit 60 supplies a gate drive signal to the gate of the switch element 34 to turn the switch element 34 ON. After t8, the transfer of charge from the capacitor 200 to the capacitor 50 stops, and I1 becomes approximately 0. Furthermore, after t8, the charge supplied from the capacitor 50 to the load 23 decreases, so that the charge supplied from the power source 20 to the load 23 increases, and I2 increases. Thereafter, the control circuit 60 repeats the switch control executed from t1 to t8.

[0041] In this way, when the control circuit 60 switches the state of the bridge circuit 30 from the first state to the second state, it turns off the switch element 31 and turns on the switch element 33 between the time when it turns off the switch element 34 and the time when it turns on the switch element 32, thereby transferring the charge stored in the capacitor 200 to the capacitor 50 via the diode 41. Furthermore, when the control circuit 60 switches the state of the bridge circuit 30 from the second state to the first state, it turns on the switch element 31 and turns off the switch element 33 between the time when it turns off the switch element 32 and the time when it turns on the switch element 34, thereby transferring the charge stored in the capacitor 200 to the capacitor 50 via the diode 42.

[0042] Next, the operation of the driving circuit 100 will be described in detail with reference to FIGS.

[0043] First, the operating state of the drive circuit 100 in the period T1 will be described with reference to Fig. 4. In the period T1, the control circuit 60 turns on the switch elements 31 and 34, and turns off the switch elements 32 and 33. In the period T1, charge flows from the high potential side output terminal 11 of the power supply 10 to one end of the capacitor 200 via the switch element 31, and charge flows from the other end of the capacitor 200 to the low potential side output terminal 12 of the power supply 10 via the switch element 34. That is, in the period T1, the capacitor 200 is driven in the positive direction.

[0044] A diode 42 for preventing reverse current is connected between the other end of the capacitor 200 and the high potential side output terminal 21 of the power supply 20. Due to the presence of the diode 42, even if the switch element 34 is ON, a current is prevented from flowing from the high potential side output terminal 21 of the power supply 20 to the low potential side output terminal 12 of the power supply 10 via the switch element 34. In other words, the diode 42 prevents a short circuit. In addition, in a period before T1, the capacitor 50 may not be sufficiently charged, and the voltage across the capacitor 50 may not reach V1. In this case, in the period T1, a current flows from the power supply 10 to the capacitor 50 via the diode 71, the switch element 31, and the diode 41, and the capacitor 50 is charged so that the voltage across the capacitor 50 becomes approximately V1.

[0045] Next, the operating state of the drive circuit 100 in the period T2 will be described with reference to Fig. 5. In the period T2, the control circuit 60 turns on the switch element 31, and turns off the switch elements 32, 33, and 34. The period T2 is the period immediately after the switch element 34 is switched from ON to OFF, and immediately after the driving of the capacitor 200 in the positive direction is completed. In the period T2, the capacitor 200 maintains a state in which a charge is stored, and the voltage across the capacitor 200 is maintained at approximately V1.

[0046] Next, referring to FIG. 6, the operating state of the drive circuit 100 in the period T3 will be described. In the period T3, the control circuit 60 turns on the switch elements 31 and 33, and turns off the switch elements 32 and 34. The period T3 is the period immediately after the switch element 33 is turned on. Therefore, in the period T3, a current flows from the power source 10 to the other end of the capacitor 200 via the diode 72 and the switch element 33. Therefore, the potential of the other end of the capacitor 200 rises from approximately 0V to a potential of V1-Vf2. Vf2 is the forward voltage of the diode 72.

[0047] At this time, the potential at one end of capacitor 200 also rises with the rise in the potential at the other end of capacitor 200. As a result, diode 41 becomes conductive and charge is discharged from one end of capacitor 200 to capacitor 50. Note that, since diode 71 for preventing reverse current is present on the path connecting one end of capacitor 200 and high potential side output terminal 11 of power supply 10, charge does not flow from one end of capacitor 200 to power supply 10.

[0048] Next, the operating state of the drive circuit 100 in the period T4 will be described with reference to Fig. 7. In the period T4, the control circuit 60 turns on the switch element 33 and turns off the switch elements 31, 32, and 34. In the period T4, as in the period T3, the charge stored in the capacitor 200 is discharged to the capacitor 50 via the diode 41. Note that if the discharge is completed in the period T3, the discharge is not performed in the period T4.

[0049] The sum of the periods T3 and T4 is preferably adjusted to a discharge time that is the time required to discharge the charge stored in the capacitor 200 to the capacitor 50. Here, the period T2 may be extremely short. Therefore, in this embodiment, the time required to switch from the first state to the second state increases only by this discharge time, compared to general control in which the capacitor 50 is not charged. This discharge time is determined, for example, according to the conduction speed of the diode 41, the diode 72, and the switch element 33, and the transient response characteristics of the power source 10, the capacitor 50, and the capacitor 200 in the path through which the charge flows.

[0050] Next, the operating state of the drive circuit 100 during the period T5 will be described with reference to Fig. 8. During the period T5, the control circuit 60 turns on the switch elements 32 and 33, and turns off the switch elements 31 and 34. During the period T5, charge flows from the high potential output terminal 11 of the power supply 10 to the other end of the capacitor 200 via the switch element 33, and charge flows from one end of the capacitor 200 to the low potential output terminal 12 of the power supply 10 via the switch element 32. That is, during the period T5, the capacitor 200 is driven in the negative direction.

[0051] A diode 41 for preventing reverse current is connected between one end of the capacitor 200 and the high potential side output terminal 21 of the power supply 20. Due to the presence of the diode 41, even if the switch element 32 is ON, a current is prevented from flowing from the high potential side output terminal 21 of the power supply 20 to the low potential side output terminal 12 of the power supply 10 via the switch element 32. In other words, the diode 41 prevents a short circuit. In addition, in a period before T5, the capacitor 50 may not be sufficiently charged, and the voltage across the capacitor 50 may not reach V1. In this case, in the period T5, a current flows from the power supply 10 to the capacitor 50 via the diode 72, the switch element 33, and the diode 42, and the capacitor 50 is charged so that the voltage across the capacitor 50 becomes approximately V1.

[0052] Next, the operating state of the drive circuit 100 in the period T6 will be described with reference to Fig. 9. In the period T6, the control circuit 60 turns on the switch element 33, and turns off the switch elements 31, 32, and 34. The period T6 is the period immediately after the switch element 32 is switched from ON to OFF, and immediately after the driving of the capacitor 200 in the negative direction is completed. In the period T6, the capacitor 200 maintains a state in which it stores a charge, and the voltage across the capacitor 200 is maintained at approximately V1.

[0053] Next, the operating state of the drive circuit 100 in the period T7 will be described with reference to Fig. 10. In the period T7, the control circuit 60 turns on the switch elements 31 and 33, and turns off the switch elements 32 and 34. The period T7 is the period immediately after the switch element 31 is turned on. Therefore, in the period T7, a current flows from the power source 10 to one end of the capacitor 200 via the diode 71 and the switch element 31. Therefore, the potential of the one end of the capacitor 200 rises from approximately 0V to the potential of V1-Vf2.

[0054] At this time, as the potential at one end of capacitor 200 rises, the potential at the other end of capacitor 200 also rises. As a result, diode 42 becomes conductive and charge is discharged from the other end of capacitor 200 to capacitor 50. Note that, since diode 72 for preventing reverse current is present on the path connecting the other end of capacitor 200 and high potential side output terminal 11 of power supply 10, charge does not flow from the other end of capacitor 200 to power supply 10.

[0055] Next, the operating state of the drive circuit 100 in the period T8 will be described with reference to Fig. 11. In the period T8, the control circuit 60 turns on the switch element 31 and turns off the switch elements 32, 33, and 34. In the period T8, as in the period T7, the charge stored in the capacitor 200 is discharged to the capacitor 50 via the diode 42. Note that if the discharge is completed in the period T7, the discharge is not performed in the period T8.

[0056] The sum of the periods T7 and T8 is preferably adjusted to a discharge time that is the time required to discharge the charge stored in the capacitor 200 to the capacitor 50. Here, the period T6 may be extremely short. Therefore, in this embodiment, the time required to switch from the second state to the first state increases only by this discharge time, compared to general control in which the capacitor 50 is not charged. This discharge time is determined, for example, according to the conduction speed of the diode 42, the diode 71, and the switch element 31, and the transient response characteristics of the power source 10, the capacitor 50, and the capacitor 200 in the path through which the charge flows.

[0057] As described above, in this embodiment, when the polarity of the voltage applied to capacitor 200 transitions, bridge circuit 30 is controlled so that the charge stored in capacitor 200 moves to capacitor 50 via diode 41 or diode 42. Therefore, according to this embodiment, the electrical energy stored in capacitor 200 can be utilized, thereby reducing power consumption when capacitor 200 is driven.

[0058] Furthermore, in this embodiment, a power supply 20 for driving another load 23 is prepared in addition to the power supply 10 for driving the bridge circuit, and the capacitor 50 is connected in parallel to the power supply 20 and the load 23. Therefore, according to this embodiment, the power supply 20 can utilize the electric energy stored in the capacitor 200, and the power consumption of the power supply 20 is reduced.

[0059] Furthermore, in this embodiment, diodes 71 and 72 are provided to suppress a current from flowing back from capacitor 200 to power source 10. Therefore, according to this embodiment, the electrical energy stored in capacitor 200 is prevented from being consumed as thermal energy due to a short circuit.

[0060] Furthermore, in this embodiment, when the state of bridge circuit 30 is switched between the first state and the second state, switch element 31, switch element 32, switch element 33, and switch element 34 are not switched simultaneously but are switched in an appropriate order. Therefore, according to this embodiment, when the state of bridge circuit 30 is switched, the charge stored in capacitor 200 can be appropriately transferred to capacitor 50.

[0061] (Embodiment 2) In the first embodiment, an example has been described in which V1, which is the power supply voltage of the power supply 10, and V2, which is the power supply voltage of the power supply 20, are the same. V1 and V2 may be different. In the present embodiment, a drive circuit 110 that can be applied when V1 is higher than V2 will be described. Note that descriptions of configurations and processes similar to those in the first embodiment will be omitted or simplified.

[0062] Hereinafter, the configuration of the drive circuit 110 according to this embodiment will be described with reference to Fig. 12. The drive circuit 110 differs from the drive circuit 100 in that it includes a step-down circuit 80. The step-down circuit 80 is a circuit that steps down a voltage. The step-down circuit 80 is a circuit that converts V1 to V2 to appropriately connect a circuit operated by a power supply 10 and a circuit operated by a power supply 20. In this embodiment, V1 is 15V and V2 is 5V.

[0063] The step-down circuit 80 is provided between the diode 41 and the diode 42 connected to the capacitor 200 and a parallel circuit of the power supply 20, the load 23, and the capacitor 50. The step-down circuit 80 includes a switch element 81, a resistor 83, and a resistor 84.

[0064] The switch element 81 steps down the voltage applied to the input terminal in accordance with the voltage applied to the control terminal, and applies the voltage obtained by stepping down to the output terminal. In this embodiment, the switch element 81 is an N-channel MOSFET. The switch element 81 includes a parasitic diode 82 that passes a current from the source of the switch element 81 to the drain of the switch element 81. Resistors 83 and 84 are resistors for adjusting the gate voltage of the switch element 81. The resistance values ​​of the resistors 83 and 84 are determined in accordance with V1 and V2.

[0065] The drain of the switch element 81 is connected to the cathode of the diode 41, the cathode of the diode 42, and one end of the resistor 83. The source of the switch element 81 is connected to the high potential side output terminal 21 of the power supply 20, one end of the load 23, one end of the capacitor 50, and one end of the resistor 84. The gate of the switch element 81 is connected to the other end of the resistor 83 and the other end of the resistor 84.

[0066] When the state of the bridge circuit 30 changes from the first state to the second state, the charge stored in the capacitor 200 is supplied to the capacitor 50 via the diode 41 and the step-down circuit 80. When the state of the bridge circuit 30 changes from the second state to the first state, the charge stored in the capacitor 200 is supplied to the capacitor 50 via the diode 42 and the step-down circuit 80. The voltage applied to the power supply 20, the load 23, the capacitor 50, etc. via the step-down circuit 80 is the stepped-down voltage. Therefore, a voltage exceeding the rated voltage is prevented from being applied to the power supply 20, the load 23, the capacitor 50, etc.

[0067] In this embodiment, the diodes 41 and 42 are connected to the capacitor 50 via a step-down circuit. Therefore, according to this embodiment, even if the power supply voltage of the power supply 10 used to drive the capacitive load is different from the power supply voltage of the power supply 20 used to drive the other load 23, the electric energy stored in the capacitive load can be appropriately used by the power supply 20.

[0068] (Embodiment 3) In the first and second embodiments, an example has been described in which a power supply 10 that generates a power supply voltage V1 for driving a capacitive load and a power supply 20 that generates a power supply voltage V2 for driving another load 23 are prepared. In the present embodiment, with reference to Fig. 13, an example will be described in which a power supply voltage V1 for driving a capacitive load and a power supply voltage V2 for driving another load 23 are generated from one power supply 300. Note that descriptions of configurations and processes similar to those of the first and second embodiments will be omitted or simplified.

[0069] The power supply 300 is a power supply that supplies DC power. The power supply 300 supplies power for driving the capacitive load and the other load 23. The power supply voltage V3 of the power supply 300 is higher than the power supply voltage V1 of the power supply 10 and the power supply voltage V2 of the power supply 20. In this embodiment, V3 is 20V. The power supply 300 outputs V3 between a high potential side output terminal 331 and a low potential side output terminal 332. The low potential side output terminal 332 is grounded and set to 0V. The power supply 300 is an example of a third power supply.

[0070] The voltage conversion circuit 310 is connected between the power supply 300 and the bridge circuit 30, and converts V3, which is a power supply voltage of the power supply 300, into V1, which is a first power supply voltage. The voltage conversion circuit 310 includes a switch element 301, a constant voltage diode 303, a resistor 304, a resistor 305, a resistor 306, a resistor 307, and a capacitor 308. The voltage conversion circuit 310 generates a power supply voltage V1 from a power supply voltage V3 applied between a high potential side output terminal 331 and a low potential side output terminal 332, and outputs the generated power supply voltage V1 between a high potential side output terminal 11 and a low potential side output terminal 12. The voltage conversion circuit 310 is an example of a first voltage conversion circuit.

[0071] The voltage conversion circuit 320 converts V3, which is a power supply voltage of the power supply 300, into V2, which is a second power supply voltage. The voltage conversion circuit 320 includes a switch element 302, a constant voltage diode 303, a resistor 304, a resistor 305, a resistor 306, a resistor 307, and a capacitor 308. The voltage conversion circuit 320 generates a power supply voltage V2 from the power supply voltage V3 applied between a high potential side output terminal 331 and a low potential side output terminal 332, and outputs the generated power supply voltage V2 between a high potential side output terminal 21 and a low potential side output terminal 22. The voltage conversion circuit 320 is an example of a second voltage conversion circuit.

[0072] Among the components included in the voltage conversion circuit 310 and the voltage conversion circuit 320, the components except for the switch element 301 and the switch element 302 are shared. The switch element 301 and the switch element 302 can be controlled independently, and the first power supply voltage V1 and the second power supply voltage V2 can be controlled independently. The switch element 301 and the switch element 302 are, for example, NPN (Negative Positive Negative) type transistors. It is preferable that the switch element 301 and the switch element 302 are products with the same characteristics and packaged in the same package. Note that a multi-emitter transistor may be adopted instead of the switch element 301 and the switch element 302.

[0073] In this embodiment, bridge circuit 30 supplies power supplied from voltage conversion circuit 310 to capacitor 200, which is a capacitive load. Capacitor 50, which is a power storage element, is connected in parallel to voltage conversion circuit 320 and load 23 that receives power from voltage conversion circuit 320. That is, the drive circuit according to this embodiment is a circuit in which power source 10 in drive circuit 100 shown in FIG. 1 is replaced with voltage conversion circuit 310 and power source 300, and power source 20 is replaced with voltage conversion circuit 320 and power source 300.

[0074] In this embodiment, a power supply voltage V1 for driving the capacitive load and a power supply voltage V2 for driving the other load 23 are generated from one power supply 300. Therefore, according to this embodiment, the capacitive load and the other load 23 are driven using one power supply 300, and the electrical energy stored in the capacitive load can be utilized to drive the other load 23.

[0075] (Embodiment 4) In the first embodiment, an example has been described in which the switch element 33 is turned ON and then the switch element 31 is turned OFF when the state of the bridge circuit 30 is switched from the first state to the second state, and the switch element 31 is turned ON and then the switch element 33 is turned OFF when the state of the bridge circuit 30 is switched from the second state to the first state. The timing of switching each switch element is not limited to this example. In the present embodiment, an example will be described in which the switch element 31 is turned OFF before the switch element 33 is turned ON when the state of the bridge circuit 30 is switched from the first state to the second state, and the switch element 33 is turned OFF before the switch element 31 is turned ON when the state of the bridge circuit 30 is switched from the second state to the first state. Note that the description of the same configuration and processing as in the first to third embodiments will be omitted or simplified.

[0076] Hereinafter, the switching order of each switch element by the control circuit 60 will be described with reference to Fig. 14 and Fig. 15. Fig. 14 shows the switch switching order according to this embodiment. As shown in Fig. 14, in this embodiment, the state of each switch element is switched so that the periods T1, T2, T3, T4, T5, T6, T7, and T8 occur in sequence and repeatedly.

[0077] A period T1 is a period during which switch element 31 and switch element 34 are ON, and switch element 32 and switch element 33 are OFF. A period T2 is a period during which switch element 31 is ON, and switch element 32, switch element 33, and switch element 34 are OFF. A period T3 is a period during which switch element 31, switch element 32, switch element 33, and switch element 34 are OFF. A period T4 is a period during which switch element 33 is ON, and switch element 31, switch element 32, and switch element 34 are OFF.

[0078] The period T5 is a period during which switch element 32 and switch element 33 are ON, and switch element 31 and switch element 34 are OFF. The period T6 is a period during which switch element 33 is ON, and switch element 31, switch element 32, and switch element 34 are OFF. The period T7 is a period during which switch element 31, switch element 32, switch element 33, and switch element 34 are OFF. The period T8 is a period during which switch element 31 is ON, and switch element 32, switch element 33, and switch element 34 are OFF.

[0079] FIG. 15 shows a timing chart illustrating the time change of signals of each part of the drive circuit 100 according to the present embodiment. FIG. 15(A) shows a voltage waveform illustrating the time change of VG1 which is the gate voltage of the switch element 31. FIG. 15(B) shows a voltage waveform illustrating the time change of VG2 which is the gate voltage of the switch element 32. FIG. 15(C) shows a voltage waveform illustrating the time change of VG3 which is the gate voltage of the switch element 33. FIG. 15(D) shows a voltage waveform illustrating the time change of VG4 which is the gate voltage of the switch element 34. FIG. 15(E) shows a current waveform illustrating the time change of I1 which is the current flowing from the capacitor 200 to the capacitor 50. FIG. 15(F) shows a current waveform illustrating the time change of I2 which is the current output by the power supply 20.

[0080] Up until t1, control circuit 60 supplies a gate drive signal to the gate of switch element 31 that turns switch element 31 ON, supplies a gate drive signal to the gate of switch element 32 that turns switch element 32 OFF, supplies a gate drive signal to the gate of switch element 33 that turns switch element 33 OFF, and supplies a gate drive signal to the gate of switch element 34 that turns switch element 34 ON.

[0081] First, at t1, the control circuit 60 supplies a gate drive signal to the gate of the switch element 34, which turns the switch element 34 OFF. Next, at t2, the control circuit 60 supplies a gate drive signal to the gate of the switch element 31, which turns the switch element 31 OFF. At t3, the control circuit 60 supplies a gate drive signal to the gate of the switch element 33, which turns the switch element 33 ON. At t3, the charge stored in the capacitor 200 moves to the capacitor 50, and I1 increases rapidly. Furthermore, after t3, charge is supplied from the capacitor 50 to the load 23, which reduces the charge supplied from the power source 20 to the load 23, and I2 decreases.

[0082] At t4, control circuit 60 supplies a gate drive signal to the gate of switch element 32 to turn on switch element 32. After t4, charge stops moving from capacitor 200 to capacitor 50, and I1 becomes approximately 0. Furthermore, after t4, the charge supplied from capacitor 50 to load 23 decreases, so the charge supplied from power supply 20 to load 23 increases, and I2 increases.

[0083] At t5, the control circuit 60 supplies a gate drive signal to the gate of the switch element 32, which turns the switch element 32 OFF. At t6, the control circuit 60 supplies a gate drive signal to the gate of the switch element 33, which turns the switch element 33 OFF. Next, at t7, the control circuit 60 supplies a gate drive signal to the gate of the switch element 31, which turns the switch element 31 ON. At t7, the charge stored in the capacitor 200 moves to the capacitor 50, and I1 increases rapidly. Furthermore, after t7, charge is supplied from the capacitor 50 to the load 23, which reduces the charge supplied from the power source 20 to the load 23, and I2 decreases.

[0084] At t8, control circuit 60 supplies a gate drive signal to the gate of switch element 34 to turn on switch element 34. After t8, charge stops moving from capacitor 200 to capacitor 50, and I1 becomes approximately 0. Also, after t8, the charge supplied from capacitor 50 to load 23 decreases, so the charge supplied from power source 20 to load 23 increases, and I2 increases. Thereafter, control circuit 60 repeats the switch control executed from t1 to t8.

[0085] In the present embodiment as well, when the state of bridge circuit 30 is switched between the first state and the second state, switch element 31, switch element 32, switch element 33, and switch element 34 are not switched simultaneously but are switched in an appropriate order. Therefore, according to the present embodiment, when the state of bridge circuit 30 is switched, the charge stored in capacitor 200 can be appropriately transferred to capacitor 50.

[0086] (Embodiment 5) In the first embodiment, an example in which each switch element is a MOSFET has been described. As each switch element, various elements capable of controlling the conductive state can be used. In the present embodiment, an example in which each switch element is a bipolar transistor will be described. Note that the description of the same configuration and processing as in the first to fourth embodiments will be omitted or simplified.

[0087] The configuration of a drive circuit 120 according to this embodiment will be described below with reference to Fig. 16. Drive circuit 120 differs from drive circuit 100 in that drive circuit 120 includes a bridge circuit 90 instead of bridge circuit 30 and does not include diodes 71 and 72.

[0088] The bridge circuit 90 supplies power supplied from the power source 10 to the capacitor 200. The bridge circuit 90 includes a switch element 91, a switch element 92, a switch element 93, and a switch element 94, and is a circuit that alternately applies a first voltage and a second voltage of mutually opposite polarities to the capacitor 200, which is a capacitive load. The bridge circuit 90 is controlled by a control circuit 60. In this embodiment, the switch elements 91, 92, 93, and 94 are NPN type transistors. The switch elements 91, 92, 93, and 94 are controlled by a gate drive signal supplied from the control circuit 60.

[0089] The switch element 91 is connected between the high potential side output terminal 11 of the power supply 10 and one end of the capacitor 200. The switch element 92 is connected between the low potential side output terminal 12 of the power supply 10 and one end of the capacitor 200. The switch element 93 is connected between the high potential side output terminal 11 of the power supply 10 and the other end of the capacitor 200. The switch element 94 is connected between the low potential side output terminal 12 of the power supply 10 and the other end of the capacitor 200. The switch element 91 is an example of a first switch element. The switch element 92 is an example of a second switch element. The switch element 93 is an example of a third switch element. The switch element 94 is an example of a fourth switch element.

[0090] The control circuit 60 controls the bridge circuit 90 so that a first voltage and a second voltage are applied to the capacitor 200. The control circuit 60 controls the bridge circuit 90 by supplying gate drive signals to each of the switch elements 91, 92, 93, and 94.

[0091] In this embodiment, each switch element is an NPN transistor. Therefore, when the base voltage is higher than the emitter voltage by about the base-emitter saturation voltage, the switch element is turned on. For example, when the control circuit 60 turns on the switch element 91, it supplies to the base of the switch element 91 a gate drive signal having a voltage higher than the emitter voltage of the switch element 91 by about the base-emitter saturation voltage. When the control circuit 60 turns on the switch element 92, it supplies to the base of the switch element 92 a gate drive signal having a voltage higher than the emitter voltage of the switch element 92, which is 0V, by about the base-emitter saturation voltage.

[0092] In this embodiment, the parasitic diode 35 is not formed in the switch element 91, and the parasitic diode 37 is not formed in the switch element 93. Therefore, the diodes 71 and 72 are not necessary.

[0093] In the present embodiment as well, when the state of bridge circuit 90 is switched between the first state and the second state, switch element 91, switch element 92, switch element 93, and switch element 94 are not switched simultaneously but are switched in an appropriate order. Therefore, according to the present embodiment, when the state of bridge circuit 90 is switched, the charge stored in capacitor 200 can be appropriately transferred to capacitor 50.

[0094] (Modification) Although the embodiments of the present disclosure have been described above, various modifications and applications are possible when implementing the present disclosure. In the present disclosure, it is optional which parts of the configurations, functions, and operations described in the above embodiments are adopted. In addition to the above-mentioned configurations, functions, and operations, further configurations, functions, and operations may be adopted in the present disclosure. The above embodiments can be freely combined as appropriate. The number of components described in the above embodiments can be adjusted as appropriate. Of course, the materials, sizes, electrical characteristics, and the like that can be adopted in the present disclosure are not limited to those shown in the above embodiments.

[0095] In the first embodiment, an example has been described in which the power source 20 supplying power to the load 23 is a power source without a power storage function. The power source 20 may be a storage battery, which is a power source with a power storage function. When the power source 20 is a storage battery, the power source 20 can also function as the capacitor 50, so that the capacitor 50 does not need to be provided in the drive circuit 100. In this case, a part of the charge discharged by the capacitor 200 is consumed by the load 23, and the remaining charge discharged by the capacitor 200 is stored in the power source 20.

[0096] In the first embodiment, an example has been described in which the drive circuit 100 includes the power supply 10, the power supply 20, and the load 23. The drive circuit 100 may not include the power supply 10, the power supply 20, and the load 23, and the power supply 10, the power supply 20, and the load 23 may be provided outside the drive circuit 100.

[0097] Various embodiments and modifications of the present disclosure are possible without departing from the broad spirit and scope of the present disclosure. The above-described embodiments are for explaining the present disclosure and do not limit the scope of the present disclosure. That is, the scope of the present disclosure is indicated by the claims, not the embodiments. Various modifications made within the scope of the claims and the scope of the disclosure equivalent thereto are considered to be within the scope of the present disclosure. [Explanation of symbols]

[0098] 10,20,300 Power supply 11, 21, 331 High potential output terminal 12, 22, 332 Low potential output terminal 23 Load 30,90 Bridge circuit 31, 32, 33, 34, 81, 91, 92, 93, 94, 301, 302 Switching elements 35, 36, 37, 38, 82 Parasitic diodes 41,42,71,72 Diodes 50,200,308 Capacitor 60 Control circuit 80 Step-down circuit 83,84,304,305,306,307 Resistance 100,110,120 Drive circuit 303 Constant voltage diode 310,320 Voltage conversion circuit

Claims

1. 1. A drive circuit for driving a capacitive load, comprising: a bridge circuit including a plurality of switch elements, and configured to alternately apply a first voltage and a second voltage having mutually opposite polarities to the capacitive load; a first rectifying element connected to one end of the capacitive load; a second rectifying element connected to the other end of the capacitive load; a storage element connected to the first rectifying element and the second rectifying element; a control circuit that controls the plurality of switch elements so that, when a voltage applied to the capacitive load transitions from the first voltage to the second voltage, a charge stored in the capacitive load transfers to the storage element via the first rectifier element, and, when a voltage applied to the capacitive load transitions from the second voltage to the first voltage, a charge stored in the capacitive load transfers to the storage element via the second rectifier element. Drive circuit.

2. The bridge circuit supplies power supplied from a first power supply to the capacitive load; The storage element is connected in parallel to a second power source and a load that receives power from the second power source.

2. The drive circuit according to claim 1.

3. a rectifying element that suppresses a reverse current flow from the capacitive load to the first power supply through the bridge circuit, 3. The drive circuit according to claim 2.

4. a power supply voltage of the first power supply is higher than a power supply voltage of the second power supply; Further comprising a step-down circuit for stepping down the voltage, the first rectifier element and the second rectifier element are connected to the storage element via the step-down circuit; 4. A drive circuit according to claim 2 or 3.

5. the plurality of switch elements include a first switch element connected between a high potential side output terminal of the first power supply and one end of the capacitive load, a second switch element connected between a low potential side output terminal of the first power supply and one end of the capacitive load, a third switch element connected between the high potential side output terminal of the first power supply and the other end of the capacitive load, and a fourth switch element connected between the low potential side output terminal of the first power supply and the other end of the capacitive load; The control circuit includes: when switching the state of the bridge circuit from a first state in which the first switch element and the fourth switch element are on and the second switch element and the third switch element are off to a second state in which the first switch element and the fourth switch element are off and the second switch element and the third switch element are on, by turning off the first switch element and turning on the third switch element during the period from turning off the fourth switch element to turning on the second switch element, the charge stored in the capacitive load is transferred to the storage element via the first rectifying element, when switching the state of the bridge circuit from the second state to the first state, the first switch element is turned on and the third switch element is turned off during a period from when the second switch element is turned off until when the fourth switch element is turned on, thereby transferring the charge stored in the capacitive load to the storage element via the second rectifier element. A driving circuit according to any one of claims 2 to 4.

6. a first voltage conversion circuit connected between a third power supply and the bridge circuit, for converting a power supply voltage of the third power supply into a first power supply voltage; a second voltage conversion circuit that converts a power supply voltage of the third power supply into a second power supply voltage; the bridge circuit supplies the power supplied from the first voltage conversion circuit to the capacitive load; the storage element is connected in parallel to the second voltage conversion circuit and a load that receives power from the second voltage conversion circuit; 2. The drive circuit according to claim 1.

7. a rectifying element that suppresses a reverse current flow from the capacitive load to the first voltage conversion circuit through the bridge circuit, 7. The drive circuit according to claim 6.

8. the first power supply voltage is higher than the second power supply voltage; Further comprising a step-down circuit for stepping down the voltage, the first rectifier element and the second rectifier element are connected to the storage element via the step-down circuit; 8. A driving circuit according to claim 6 or 7.

9. the plurality of switch elements include a first switch element connected between a high potential side output terminal of the first voltage conversion circuit and one end of the capacitive load, a second switch element connected between a low potential side output terminal of the first voltage conversion circuit and one end of the capacitive load, a third switch element connected between the high potential side output terminal of the first voltage conversion circuit and the other end of the capacitive load, and a fourth switch element connected between the low potential side output terminal of the first voltage conversion circuit and the other end of the capacitive load, when switching the state of the bridge circuit from a first state in which the first switch element and the fourth switch element are on and the second switch element and the third switch element are off to a second state in which the first switch element and the fourth switch element are off and the second switch element and the third switch element are on, by turning off the first switch element and turning on the third switch element during the period from turning off the fourth switch element to turning on the second switch element, the charge stored in the capacitive load is transferred to the storage element via the first rectifying element, when switching the state of the bridge circuit from the second state to the first state, the first switch element is turned on and the third switch element is turned off during a period from when the second switch element is turned off until when the fourth switch element is turned on, thereby transferring the charge stored in the capacitive load to the storage element via the second rectifier element. A driving circuit according to any one of claims 6 to 8.

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