JP2000341971A - Drive circuit of inverter equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To promote miniaturization and weight reduction and enable stable switching drive. SOLUTION: This drive circuit is provided with a first low voltage power source part 3, a second low voltage power source part 4, first drive parts 11U-11W drive switching elements 13U-13W, second drive parts 12U-12W drive switching elements 14U-14W connected in series with the switching elements 13U-13W, a control part 5 which drive controls the first drive parts 11U-11W and the second driving parts 12U-12W and generates desired AC output from connection points PU-PW of the switching elements 13U-13W and the switching elements 14U-14W, capacitors CU-CW connecting the connection points PU-PW with power source input terminals of the first drive parts 11U-11W, and diodes DU-DW, which connect power source input terminal sides of the capacitors CU-CW with the first low voltage power source part 3 and make the direction of the first low voltage power source part 3 to the power source input terminal sides to be the direction of electrical continuity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive circuit of an inverter device used for driving an electric motor or the like, and more particularly to a drive circuit for a switching device constituting an inverter device, which is reliably driven by a simple configuration to obtain a desired inverter output. The present invention relates to a drive circuit of an inverter device that can be obtained.

[0002]

2. Description of the Related Art Conventionally, in order to perform variable speed control of an electric motor such as an induction motor, an inverter device capable of obtaining an AC output having a desired frequency has been used. ing.

FIG. 3 is a block diagram showing an entire configuration of an inverter device including a drive circuit of a conventional inverter device. In FIG. 3, an AC power supply 10 having a constant frequency
1 is supplied to a rectifier circuit 102 such as a full-wave rectifier circuit.
Rectified by A rectified output from the rectifier circuit 102 is input to a U-phase generator 106, a V-phase generator 107, and a W-phase generator 108, and each of the U-phase, V-phase, and W-phase of three-phase AC output having a desired frequency. Generate

The U-phase generation unit 106, the V-phase generation unit 107, and the W-phase generation unit 108
13U, 114U, 113V, 114V, 113W, 1
Switching elements 113U, 114U, 113V, 11
4 V, 113 W, and 114 W are respectively connected to the rectifier circuit 102.
Are connected in parallel. Switching elements 113U to 113
W is switching-driven by the first driving units 111U to 111W, respectively, and the switching elements 114U to 1
14W is switching-driven by 2nd drive parts 112U-112W, respectively.

The first driving units 111U to 111W and the second
The driving units 112U to 112W are driven and controlled by the control unit 105, and the first driving unit 111
U to 111W and the second driving units 112U to 112W
Switching elements 113U to 113W, 114U to 11
By applying a predetermined voltage to the 4 W gate, each of the switching elements 113U to 113W, 114U to 114
Turn W on and off. That is, the control unit 105
Drive units 111U to 111W and second drive units 112U to 112U
2W and switching elements 113U to 113W,
By turning on and off 114U to 114W, a desired three-phase AC output is output. The low-voltage power supply unit 104 uses the rectified output from the rectifier circuit 102 to output the first drive units 111U to 111W and 112U to 112W.
Supplies power for driving.

The operation of generating a U-phase AC output will now be described with reference to FIGS. FIG. 4 is a diagram mainly showing the U-phase generation unit 106, and the first drive unit 111U
And the second drive unit 112U are connected to the low-voltage power supply unit 1
Switching element 11 using the charge supplied from
3U and 114U are turned on and off.

FIG. 5 is a timing chart showing ON / OFF operations of switching elements (FETs) 113U and 114U in U-phase generating section 106 and a change in potential at connection point Pa between switching element 113U and switching element 114U. . In FIG. 4, the switching element 11
When the switching element 113U is turned on while 4U is off, the potential VPa at the connection point Pa becomes +
The potential rises to the potential VP (+) of the terminal P (+). Thereafter, when the switching element 114U is turned on, the potential VPa of the connection point Pa falls to the potential VP (-) of the -terminal P (-). This potential VP (-) is a ground potential.

Here, the voltage drop between the positive terminal P (+) and the connection point Pa and the voltage drop between the negative terminal P (-) and the connection point Pa can be regarded as substantially equal. Therefore, by extracting the output from the connection point Pa, a U-phase AC output can be obtained. Similarly, the V-phase generator 1
07 and W-phase generator 108 provide V-phase and W-phase AC outputs, respectively, and an equivalent three-phase AC output can be obtained. The phase intervals of the U phase, V phase, and W phase are realized by drive control of the control unit 105.

[0009] Japanese Patent Publication No. 5-84151 discloses that
Similarly to the drive circuit of the inverter device described above, switching elements 113U to 113W and switching element 114
A drive circuit of an inverter device capable of obtaining an inverter output having a desired frequency by alternately turning on and off U to 114W is described.

[0010]

However, in the drive circuit of the above-described conventional inverter device, the low-voltage power supply unit 104 used when the first drive unit 111U is driven is used.
Is connected to the connection point Pa because the voltage applied by the first drive unit 111U is the voltage between the gate and the drain, and the potential VPa at the connection point Pa is
There is a problem that stable power cannot be supplied to the first drive unit 111U because the power becomes unstable when 13U and 114U are turned on and off.

That is, in a state where the switching element 113U is turned on and the switching element 114U is turned off, the potential of the connection point VPa is maintained at a constant potential VP (+), the switching element 113U is turned off, and the switching element 113U is turned off. While 114U is on, it is maintained at a constant potential VP (−), but the switching element 113U
When both the switching element 114U and the switching element 114U are in the off state, the potential of the connection point VPa is not determined. As a result, the reference potential supplied to the first driving unit 111U is not fixed, resulting in unstable power supply, Element 11
3U switching cannot be performed stably. The low-voltage power supply unit 1 that supplies power to the second drive unit 112U
The reference potential of 04 is always fixed by the potential VP (−) of the −terminal P (−).

In order to solve this problem, for example, it is conceivable to apply a magnetic coupling circuit that is electrically insulated using a transformer or the like to the low-voltage power supply unit 104 to supply power to the first drive unit 111U. However, there is a problem that the addition of a magnetic coupling circuit such as a transformer impedes the downsizing of the entire inverter device, and cannot promote the reduction in weight and size of the inverter device. In particular, a magnetic coupling circuit such as a transformer prevents the inverter device from being reduced in weight and size.

The present invention has been made in view of the above,
An object of the present invention is to provide a drive circuit of an inverter device which can promote downsizing and weight reduction and can perform stable switching drive.

[0014]

In order to achieve the above object, a drive circuit for an inverter device according to the present invention generates a predetermined power supply voltage based on a rectified output from a rectifier for rectifying an AC power supply output. A first power supply; a second power supply that generates a predetermined power supply voltage based on the rectified output;
A first switching element that switches by driving the second driving means and a second switching element that switches by driving the second driving means are connected in series, and the first switching element and the second switching are connected in series. A switching unit in which a circuit composed of elements is connected in parallel to the rectifying unit; and a driving point of the first driving unit and the second driving unit, and a connection point between the first switching element and the second switching element. Inverter control means for generating a desired AC output from the power supply, a capacitor connected between the connection point and a power input terminal of the first drive means, a power input terminal side of the capacitor and the first power supply And a diode having a conduction direction from the first power supply to the power supply input terminal. The second power supply supplies power when the second drive means drives and outputs, the first power supply charges the capacitor, and the first drive means drives the first drive means. It is characterized in that the charge stored in the capacitor is used when outputting.

According to the present invention, the first power supply generates a predetermined power supply voltage based on the rectified output from the rectifying means for rectifying the output of the AC power supply. When the switching element is in the ON state, the capacitor is charged via the diode, and the charge of the charged capacitor is charged in the first state when the first switching element is ON and the second switching element is OFF. Since the power is supplied to the driving means, the first switching element performs stable switching, while the second power supply generates a predetermined power supply voltage based on the rectified output, and generates the predetermined power supply voltage. And the second switching element is switched by the second driving means, and the second switching element is switched by the inverter control means. Obtain an AC output.

A drive circuit for an inverter device according to the next invention comprises: a first power supply for generating a predetermined power supply voltage based on a rectified output from a rectifier for rectifying an AC power output; A second power supply that generates a predetermined power supply voltage, a first switching element that switches by driving the first driving means, and a second switching element that switches by driving the second driving means, are connected in series. A plurality of switching means each including a plurality of circuits each including the first switching element and the second switching element connected in series and connected in parallel to the rectifying means; and the first driving means and the second driving means. Drive control to generate a desired AC output from each connection point between the first switching element and the second switching element. Barter control means, a plurality of capacitors connecting between the connection points and the power supply input terminals of the first drive means, and between the power supply input terminal side of each of the capacitors and the first power supply And a plurality of diodes each having a conducting direction from the first power supply to each of the power supply input terminals, wherein the second power supply has a plurality of drive outputs. The first power supply charges a plurality of the capacitors, and the plurality of the first driving means store the power in a connected capacitor when the first driving means drives and outputs the power. Characterized in that the charge is used.

According to the present invention, the first power supply generates a predetermined power supply voltage based on the rectified output from the rectifying means for rectifying the AC power supply output, and the first switching element of each switching means is turned off. When the second switching element is in the ON state, the respective capacitors are sequentially charged via the respective diodes, and the charged charges of the respective capacitors are transferred to the second switching element when the first switching element of the respective switching means is turned on. Since the switching elements are supplied to the respective first driving means when the switching elements are in the off state, the respective first switching elements perform stable switching, respectively, while the second power supply is based on the rectified output. A predetermined power supply voltage is generated, and the generated power supply voltage is supplied to each second driving unit, and each second switching element is switched by each second driving unit. And, by alternate switching drive control by the inverter control means, for example, the desired 3
Obtain phase alternating current output.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a drive circuit for an inverter device according to the present invention will be described below in detail with reference to the accompanying drawings.

Embodiment 1 First, a first embodiment of the present invention will be described. FIG. 1 is a block diagram showing a configuration of an inverter device including a drive circuit of the inverter device according to Embodiment 1 of the present invention. In FIG. 1, an AC output from an AC power supply 1 having a constant frequency is rectified by a rectifier circuit 2 such as a full-wave rectifier circuit. Rectifier circuit 2
Are input to a U-phase generation unit 6, a V-phase generation unit 7, and a W-phase generation unit 8 to generate U-phase, V-phase, and W-phase of three-phase AC output having a desired frequency, respectively. .

The U-phase generator 6, the V-phase generator 7, and the W-phase generator 8 include switching elements 13U and 14U, respectively.
U, 13V, 14V, 13W, and 14W, each being connected in series, and the switching element 13 connected in series.
U, 14U, 13V, 14V, 13W, and 14W are connected in parallel to the rectifier circuit 2, respectively. Switching element 1
The switching units 3U to 13W are driven by the first driving units 11U to 11W, respectively.
-14W are switching-driven by the second drive units 12U-12W, respectively.

The first drive units 11U to 11W and the second drive units 12U to 12W are drive-controlled by the control unit 5,
By this driving control, the first driving units 11U to 11W and the second driving units 12U to 12W
By applying a predetermined voltage to the gates of U-13W and 14U-14W, each of the switching elements 13U-13
W, 14U to 14W are turned on and off. That is, the control unit 5 includes the first driving units 11U to 11W and the second driving unit 12U.
Switching elements 13U to 13W through １２12W,
By turning on and off the 14U to 14W, a desired three-phase AC output is output.

The first low-voltage power supply 3 is connected to the rectifier circuit 2 in parallel. The second low-voltage power supply unit 4 is connected to the rectifier circuit 2 in parallel. The first low-voltage power supply unit 3 and the second low-voltage power supply unit 4 are each configured by, for example, a switching power supply, and generate a low voltage from the voltage obtained by the rectifier circuit 2, respectively, and generate a diode D3 and a smoothing capacitor C3. And a diode D4 and a smoothing capacitor C4. The first low-voltage power supply unit 3 supplies the electric charge accumulated in the smoothing capacitor C3 to each of the power supply units 10U to 10W, and the second low-voltage power supply unit 4
Supplies the electric charge accumulated in the smoothing capacitor C4 to each of the second driving units 12U to 12W, and
W uses the charge accumulated in the smoothing capacitor C4 as a drive voltage for each of the switching elements 14U to 14W.

The power supply units 10U to 10W connect the power supply input terminals of the first driving units 11U to 11W with the connection points PU to PW of the switching elements 13U to 13W and the switching elements 14U to 14W, respectively. Capacitor C
U to CW, and a connection point between the diode D3 of the first low-voltage power supply unit 3 and the smoothing capacitor C3;
The drive units 11U to 11W have diodes DU to DW, respectively, which are connected to the power supply input terminals and have the first drive units 11U to 11W in the forward direction. Then, each of the first driving units 11U to 11W uses the charge accumulated in the capacitors CU to CW of each of the power supply units 10U to 10W as a driving voltage for each of the switching elements 13U to 13W.

As described above, the control unit 5 controls the driving of the first driving unit 11U and the second driving unit 12U to turn on and off the switching elements 13U and 14U alternately, as shown in FIG. As a result, a U-phase AC output is output from the connection point PU, and the first drive unit 11V and the second drive unit 1
2V is drive-controlled to alternately turn on and off the switching elements 13V and 14V, thereby outputting a V-phase AC output from the connection point PV to drive-control the first drive unit 11W and the second drive unit 12W. Switching element 13W, 1
4W is turned on and off alternately, thereby outputting a W-phase AC output from the connection point PW.

The control unit 5 controls the inverter output of each phase by controlling the driving of the first driving units 11U to 11W and the second driving units 12U to 12W, thereby controlling the motor M such as a three-phase induction motor. Is controlled for its rotation speed and the like. Since the inverter output from each of the connection points PU to PW is a three-phase AC output, the phase interval between the U, V, and W phases is controlled to 120 °.

Here, a description will be given of the stabilization of the voltage supply to the first driving units 11U to 11W by using the power supply units 10U to 10W. The other power supply unit 1
The operation at 0 V and 10 W is the same as that of the power supply unit 10U. Here, the operation of the power supply unit 10U will be described.

First, when the switching element 13U is off and the switching element 14U is on, the connection point PU
Is the same as the potential of the negative terminal P (−), in this case, the ground voltage, and the potential of the diode D3 from the connection point between the diode D3 and the smoothing capacitor C3 in the first low-voltage power supply unit 3.
Charge flows into the capacitor CU via U, the capacitor CU is charged, and the charge is accumulated.

Next, when the switching element 13U is on and the switching element 14U is off, the connection point P
The potential of U becomes the same as the potential of the positive terminal P (+), that is, the potential of the high voltage side of the rectifier circuit 2, and the potential is higher than the potential of the connection point between the diode D 3 and the smoothing capacitor C 3 in the first low-voltage power supply unit 3. Although higher, the direction of the diode DU prevents the direction of current flow from the capacitor CU toward the connection point between the diode D3 and the smoothing capacitor C3, and the charge stored in the capacitor CU is maintained. Therefore, when the switching element 13U is ON, the first driving unit 11U can use the electric charge accumulated in the capacitor CU, and the first driving unit 1U using this electric charge can be used.
The ON state is maintained by the voltage application to the gate of the switching element 13U by 1U.

Therefore, regardless of whether the potential at the connection point PU is high or low, the electric charge accumulated in the capacitor CU can always be used.
A stable power supply can be supplied to U, and as a result, the switching element 13U can be stably turned on and off. Since the drain side of the switching element 14U is always grounded, the power supply voltage from the second low-voltage power supply unit 4 can be used as it is as the power supply voltage for the second drive unit 12U.

According to the first embodiment, the first driving unit 1
A first low-voltage supply unit 3 for supplying a power supply voltage used by 1U to 11W and a second low-voltage power supply unit 4 for supplying a power supply voltage used by the second drive units 12U to 12W are separately provided, and By providing the power supply units 10U to 10W between the voltage power supply unit 3 and the first drive units 11U to 11W, the first drive units 11U to 11W can stably store in the capacitors CU to CW of the power supply units 10U to 10W. Since the used charges are used, a stable switching operation can be obtained, and the power supply units 10U to 10W can be realized by a simple circuit configuration including diodes DU to DW and capacitors CU to CW. Since it is not necessary to use an electrical insulating circuit using a magnetic coupling circuit or the like which is increased in size, the drive circuit of the inverter device can be reduced in weight and size.

In the first embodiment, the first low voltage supply unit 3 for supplying the power supply voltage used by the first driving units 11U to 11W, and the first low voltage supply unit 3 for supplying the power supply voltage used by the second driving units 12U to 12W. Since the second low-voltage power supply unit 4 is provided separately, the load current flowing through the first low-voltage supply unit 3 and the load current flowing through the second low-voltage supply unit 4 can be separated. The capacity of the smoothing capacitor C3 forming the voltage power supply section 3 and the capacity of the smoothing capacitor C4 forming the second low voltage power supply section 4 can be reduced, respectively, thereby promoting the reduction in the weight and size of the drive circuit of the inverter device. Can be.

Embodiment 2 FIG. Next, a second embodiment of the present invention will be described. In the first embodiment, power supply units 10U to 1U corresponding to first drive units 11U to 11W, respectively.
Although the power supply to 0 W is supplied by one first low-voltage power supply unit 3, the power supply to each of the power supply units 10 U to 10 W is individually performed in the second embodiment.

FIG. 2 is a block diagram showing a configuration of an inverter device including a drive circuit of the inverter device according to the second embodiment of the present invention. In FIG. 2, first low-voltage power supply units 3a to 3c correspond to first low-voltage power supply unit 3 in the first embodiment, and first low-voltage power supply units 3a to 3c are connected in parallel to rectifier circuit 2, respectively. Power supply units 10U to 10U
Power is supplied to each of the first driving units 11U to 11W via W.

That is, the first low-voltage power supply unit 3 in the first embodiment is connected to all of the power supply units 10U to 10W, and is connected to each of the first drive units 11 via the respective power supply units 10U to 10W.
Although power is supplied to all of the U to 11W, in the second embodiment, a plurality of first low voltage supply units 3a to 3c corresponding to the number of the first driving units 11U to 11W are provided. The first low voltage supply units 3a to 3c are connected to the power supply units 10U to 10U, respectively.
10W, and power is supplied to each of the first driving units 11U to 11W connected to the power units 10U to 10W. The other configuration is the same as the configuration shown in FIG. 1, and the same components are denoted by the same reference numerals.

Each of the first low-voltage supply units 3a to 3c, like the first low-voltage supply unit 3, is constituted by, for example, a switching power supply, and generates a low voltage from the voltage obtained by the rectifier circuit 2. And the diodes Da to Dc and the smoothing capacitor C
a to Cc. The connection points between the diodes Da to Dc and the smoothing capacitors Ca to Cc are connected to the power supply unit 10 respectively.
U to 10W.

The second low voltage supply unit 4 not only supplies power to the second drive units 12U to 12W, but also supplies the second
Power is also supplied to a portion using the power supply voltage supplied by the low voltage supply unit 4, for example, the control unit 5. As described above, the second low-voltage supply unit 4 may supply power to other components such as the control unit 5, and can be similarly applied to the first embodiment.

According to the second embodiment, the first embodiment
Since the load of the first low-voltage power supply unit 3 is distributed to the three first low-voltage power supply units 3a to 3c, the load on each of the first low-voltage power supply units 3a to 3c is reduced. 1 Smoothing capacitors Ca to C in low voltage power supply units 3a to 3c
Since the capacity of c can be reduced and the required withstand voltage performance can be low, further reduction in weight and size can be promoted.

[0038]

As described above, according to the present invention, the first power supply generates a predetermined power supply voltage based on the rectified output from the rectifying means for rectifying the AC power supply output. When the switching element is off and the second switching element is on, the capacitor is charged via the diode, and the charged capacitor charges the first switching element on and the second switching element off. Is supplied to the first driving means in the state of, the first switching element performs stable switching, while
The second power supply generates a predetermined power supply voltage based on the rectified output, supplies the generated power supply voltage to the second driving unit, and causes the second driving unit to switch the second switching element. As a result, a desired AC output is obtained by alternate switching drive control by the inverter control means, so that a stable charge can be supplied from the capacitor to the first drive means, and the stable charge The configuration for supply is realized by adding a simple circuit consisting of a capacitor and a diode, instead of adding a circuit having both a large weight and a large scale such as a magnetic coupling circuit for performing electrical insulation. Therefore, it is possible to reduce the size and weight of the inverter device.

Further, since the first power supply for supplying power to the first drive means and the second power supply for supplying power to the second drive means are separated, the power supply for the inverter output is provided. The power supply load is distributed, and the capacity of circuit elements such as capacitors in the first power supply means and the second power supply means can be reduced. As a result, the use of small and lightweight circuit elements makes it possible to reduce the entire inverter device. There is an effect that reduction in size and weight can be promoted.

According to the next invention, the first power supply generates a predetermined power supply voltage based on the rectified output from the rectifying means for rectifying the AC power supply output, and the first switching element of each switching means has When the second switching element is off and the second switching element is on, each capacitor is sequentially charged via each diode, and the charged charge of each capacitor is stored in the second switching element of each switching means when the first switching element is on.
Are supplied to the respective first driving means when the switching elements are in an off state, the respective first switching elements perform stable switching, respectively, while the second power supply is based on the rectified output. , A predetermined power supply voltage is generated, and the generated power supply voltage is supplied to each second driving means, and each second switching element is switched by each second driving means. By switching drive control, for example, a desired 3
Since the phase AC output is obtained, the above-described effects of the invention are obtained, and when a desired AC output obtained by combining the inverter outputs output from the plurality of switching means is obtained, the plurality of first switching elements are provided. This has the effect that the power required for driving the device can be stably supplied by one first power supply.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an inverter device including a drive circuit of the inverter device according to Embodiment 1 of the present invention;

FIG. 2 is a block diagram showing a configuration of an inverter device including a drive circuit of the inverter device according to Embodiment 2 of the present invention;

FIG. 3 is a diagram showing an entire configuration of a conventional inverter device including a drive circuit of the inverter device.

FIG. 4 is a block diagram showing a partial configuration of a drive circuit of a conventional inverter device.

FIG. 5 is a timing chart showing an example of an inverter output generated by turning on and off a switching element directly connected.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 AC power supply, 2 rectifier circuit, 3, 3 a to 3 c first low-voltage power supply section, 4 second low-voltage power supply section, 5 control section, 6
U phase generator, 7 V phase generator, 8 W phase generator, 9 motor, 10 U to 10 W power supply unit, 11 U to 11 W first
Drive unit, 12U to 12W Second drive unit, 13U to 13
W, 14U-14W switching element, DU-DW,
D3, Da to Dc, D4 diode, CU to CW capacitor, C3, Ca to Cc, C4 smoothing capacitor,
PU to PW connection point.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Kunihiko Yagi 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) in Mitsubishi Electric Corporation 5H007 BB06 CA02 CB05 CC23 DB03 DB09

Claims (2)

[Claims] 1. A first power supply that generates a predetermined power supply voltage based on a rectified output from a rectifier that rectifies an AC power supply output, and a second power supply that generates a predetermined power supply voltage based on the rectified output. Power supply, a first switching element that switches by driving the first driving means, and a second switching element that switches by driving the second driving means, are connected in series, and the first switching is connected in series. A switching unit in which a circuit including an element and a second switching element is connected in parallel to the rectifying unit; and a drive control of the first driving unit and the second driving unit to control the first switching element and the second switching unit. An inverter control unit for generating a desired AC output from a connection point with the switching element; and a connection between the connection point and a power input terminal of the first drive unit. And a diode that connects between the power supply input terminal side of the capacitor and the first power supply, and has a conduction direction from the first power supply to the power supply input terminal side. The second power supply supplies power when the second drive means drives and outputs, the first power supply charges the capacitor, and the first drive means is provided by the first drive means. A drive circuit for an inverter device, wherein electric charge stored in the capacitor is used when driving and outputting. 2. A first power supply that generates a predetermined power supply voltage based on a rectified output from a rectifier that rectifies an AC power supply output, and a second power supply that generates a predetermined power supply voltage based on the rectified output. Power supply, a first switching element that switches by driving the first driving means, and a second switching element that switches by driving the second driving means, are connected in series, and the first switching is connected in series. A plurality of switching means each including a plurality of circuits each composed of an element and a second switching element connected in parallel to the rectifying means; and controlling the first driving means and the second driving means to perform the first switching. An inverter control means for generating a desired AC output from each connection point between the element and the second switching element; and A plurality of capacitors connecting between the power supply input terminals of the driving means, and a connection between the power supply input terminal side of each of the capacitors and the first power supply. A plurality of diodes having a conduction direction in a direction toward the input terminal, wherein the second power supply supplies power when the plurality of second driving units drive and output, and the first power supply is A plurality of the first capacitors are charged, and a plurality of the first driving units use electric charges accumulated in a connected capacitor when the first driving unit outputs a drive signal. circuit.