JP2014124025A - Switching element drive power supply circuit of inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an upper arm switching element to be continuously held in an on state by a simple scheme.SOLUTION: A main power supply circuit 10 shared by upper arm drive circuits 16-1, 16-2 and lower arm drive circuits 14-1, 14-2 comprises a switching element S connected in series to a primary-side coil TC1 of a transformer T connected to a battery 12, and a diode 13 connected to a secondary-side coil TC2 of the transformer T. Power supply capacitors C2, C4 for the respective lower arm drive circuits are connected in parallel on the input side of the respective lower arm drive circuits. Bootstrap circuit capacitors CB are connected in parallel on the input side of the respective upper arm drive circuits, and each of the bootstrap circuits 17-1, 17-2 is connected at one end to the corresponding power supply capacitors C2, C4. An auxiliary power supply 18 is connected to the primary side of the transformer T, and is provided with power feeding circuits 19-1, 19-2 for connecting the auxiliary power supply 18 to positive-side terminals of the bootstrap circuit capacitors CB.

Description

  The present invention relates to a switching element drive power supply circuit for an inverter device, and more particularly to a switching element drive power supply circuit for an inverter device characterized by a circuit for driving a switching element of an upper arm.

  The inverter device is configured by connecting a plurality of series circuits in which switching elements called upper and lower arms are connected in series. The three-phase inverter includes three sets of series circuits, and the single-phase inverter includes two sets of series circuits. It has a series circuit. Then, the switching elements of the upper arm and the lower arm of different series circuits are controlled to be turned on and off in a predetermined order to convert DC power into AC power and output it.

As a configuration for obtaining a plurality of independent power supplies for the switching element of the upper arm, a system using a multi-output transformer, a system using a bootstrap circuit, and the like are known.
In the system using a multi-output transformer, a primary winding connected between the positive and negative poles of the power supply of the inverter circuit and a plurality of secondary windings corresponding to each drive circuit are provided.

  Further, as a system using a bootstrap circuit, one shown in FIG. 3 has been proposed (see Patent Document 1). This inverter is connected to a converter connected to a solar cell module (not shown) and supplied with DC power. The inverter 50 includes switching elements Q1 to Q4, gate driving circuits 51-1 to 51-4 for applying gate pulses to the switching elements Q1 to Q4, and a gate driving circuit 51-2 for driving the switching elements Q2 and Q4 for the lower arm. , 51-4, a gate power supply circuit 52 for supplying a gate power supply, and gate power supply capacitors C1, C3 that operate as power supplies for the gate drive circuits 51-1, 51-3 of the switching elements Q1, Q3 for the upper arm. A bootstrap circuit is included.

JP 2010-57337 A

  However, the method using a multi-output transformer causes problems such as an increase in the size of the power supply circuit and an increase in the cost of the inverter device. In the system using the bootstrap circuit of Patent Document 1, the gate power supply capacitor C1 of the upper arm is charged only when the switching element Q2 of the lower arm is turned on, and the gate power supply capacitor C3 is charged by the switching element Q4 of the lower arm. Since the battery is charged only when is turned on, there is a problem that the on-time of the upper arm switching elements Q1 and Q3 is limited. For example, when an inverter is used for driving a motor, the duty ratio cannot be set to 100% when it must be driven at a duty ratio of 100% in order to supply desired power to the motor in PWM control. May occur, resulting in poor controllability.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a switching element drive power supply circuit for an inverter device capable of continuously turning on the switching element of the upper arm in a simple manner. It is to provide.

  A switching element driving power supply circuit for an inverter device that solves the above problems includes a plurality of series circuits of upper arm switching elements and lower arm switching elements connected in series constituting the upper arm and the lower arm. An upper arm driving circuit is provided corresponding to each arm switching element, and a lower arm driving circuit is provided corresponding to each lower arm switching element. The switching element drive power supply circuit includes a transformer connected to a DC power supply, a switching element connected in series to a primary coil of the transformer, and a rectifier connected to a secondary coil of the transformer, A main power supply circuit common to each upper arm drive circuit and each lower arm drive circuit, and a power supply capacitor for the lower arm drive circuit connected in parallel to the power input side of each lower arm drive circuit. . Also, the power supply capacitor for the lower arm driving circuit connected to the power input side of each of the upper arm driving circuits and having a capacitor for a bootstrap circuit connected in parallel with each of the upper arm driving circuits and having one end corresponding thereto A bootstrap circuit connected to the transformer, an auxiliary power supply connected to the primary side of the transformer and storing energy using a switching surge of the switching element, and a positive side terminal of the capacitor for the bootstrap circuit using the auxiliary power supply And a power feeding circuit connected to. Here, the “corresponding power supply capacitor for the lower arm driving circuit” is parallel to the lower arm driving circuit for driving the lower arm switching element connected in series with the upper arm switching element driven by the upper arm driving circuit. Means a capacitor connected to

  According to this configuration, each lower arm drive circuit includes power supplied from a main power supply circuit common to each upper arm drive circuit and each lower arm drive circuit, and energy stored in a power supply capacitor for each lower arm drive circuit. To drive the lower arm switching element. On the other hand, energy is stored in the auxiliary power source connected to each upper arm drive circuit via a power feeding circuit by a surge voltage when the switching element of the main power circuit is turned off. Each upper arm drive circuit is supplied with power not only from the main power supply circuit common to each upper arm drive circuit and each lower arm drive circuit, but also from the auxiliary power supply. Therefore, unlike the conventional bootstrap system, power is also supplied from the auxiliary power source to the capacitor for the bootstrap circuit, so the on-time of the upper arm is not limited and there is no problem even if the on-time is extended. Therefore, the switching element of the upper arm can be continuously turned on by a simple method.

  Preferably, the auxiliary power source includes a diode and a capacitor, and the diode has an anode connected to a connection point between the primary coil and the switching element, and a cathode connected to the capacitor. According to this configuration, since the auxiliary power supply is configured by a series circuit of a diode and a capacitor, the configuration is simplified.

  The power supply circuit is configured by connecting a diode and a resistor in series, an anode side of the diode is connected to a connection point between the diode and the capacitor of the auxiliary power supply, and a cathode side of the diode is used for the bootstrap circuit. It is preferable to be connected to the positive terminal side of the capacitor. In this configuration, energy stored in the bootstrap circuit capacitor is prevented from being discharged to the auxiliary power supply side through the power feeding circuit.

  According to the present invention, the switching element of the upper arm can be continuously turned on in a simple manner.

1 is a circuit diagram showing a configuration of a first embodiment. The circuit diagram of a 2nd embodiment. The circuit diagram which shows the structure of a prior art.

(First embodiment)
Hereinafter, a first embodiment of the inverter device will be described.
FIG. 1 shows a circuit configuration for two phases constituting a switching element driving power supply circuit of an inverter device.

  As shown in FIG. 1, a lower arm driving power supply circuit 11 for driving a switching element Q2 as a lower arm switching element constituting the lower arm of the first phase includes a transformer T connected to a battery 12 as a DC power supply. , A transformer switching element S, a capacitor C0, a diode 13 as a rectifier, and a power supply capacitor C2 for the lower arm drive circuit 14-1. The transformer switching element S is connected in series to the primary coil TC1 of the transformer T, and the capacitor C0 is connected in parallel to the battery 12 on the primary side of the transformer T. The diode 13 has an anode connected to the secondary coil TC2 of the transformer T and a cathode connected to the positive terminal side of the power supply capacitor C2. A power supply capacitor C2 for the lower arm driving circuit is connected in parallel to the lower arm driving circuit 14-1. The transformer T connected to the battery 12, the switching element S connected in series to the primary side coil TC1 of the transformer T, and the diode 13 as a rectifying means connected to the secondary side coil TC2 of the transformer T, A main power supply circuit 10 common to the upper arm drive circuit and each lower arm drive circuit is configured.

  An upper arm driving power supply circuit 15-1 for driving a switching element Q1 as an upper arm switching element constituting the upper arm of the first phase includes a bootstrap circuit 17-1, an auxiliary power supply 18, and a power feeding circuit 19-1. And. The bootstrap circuit 17-1 includes a bootstrap circuit capacitor CB connected in parallel with the upper arm drive circuit 16-1, and a boot connected between the capacitor CB and the power supply capacitor C2 for the lower arm drive circuit. The strap circuit includes a resistor RB and a series circuit of a diode DB. The anode of the diode DB is connected to the connection point between the diode 13 and the power supply capacitor C2.

  The auxiliary power source 18 is connected to the primary side of the transformer T, and includes an auxiliary power source diode DA and an auxiliary power source capacitor CA. The diode DA has an anode between the primary side coil TC1 and the switching element S. Connected to the connection point, the cathode is connected to the capacitor CA.

  The power feeding circuit 19-1 is configured by connecting a diode DS and a resistor RS in series. The diode DS has an anode connected to a connection point between the diode DA of the auxiliary power supply 18 and the capacitor CA, and a cathode via the resistor RS. It is connected to the positive terminal side of the capacitor CB for the bootstrap circuit. That is, the anode side of the diode DS is connected to the connection point between the diode DA of the auxiliary power supply 18 and the capacitor CA, and the cathode side is connected to the plus terminal side of the capacitor CB for the bootstrap circuit.

  Further, in the lower arm driving power supply circuit for driving the switching element Q4 as the lower arm switching element constituting the lower arm of the second phase, the power capacitor C4 for the lower arm driving circuit is in parallel with the lower arm driving circuit 14-2. It is connected to the. The cathode of the diode 13 of the main power supply circuit 10 is connected to the positive terminal side of the power supply capacitor C4. That is, in the second-phase lower arm driving power supply circuit, the power supply capacitor C4 is charged by driving the switching element S.

  The upper arm driving power supply circuit 15-2 for driving the switching element Q3 as the upper arm switching element constituting the upper arm of the second phase includes a bootstrap circuit 17-2, an auxiliary power supply 18, and a power feeding circuit 19. -2. The bootstrap circuit 17-2 includes a bootstrap circuit capacitor CB connected in parallel with the upper arm drive circuit 16-2, and a boot connected between the capacitor CB and the power supply capacitor C4 for the lower arm drive circuit. The strap circuit includes a resistor RB and a series circuit of a diode DB.

  The auxiliary power supply 18 is shared with the upper arm driving power supply circuit 15-1 for driving the first-phase switching element Q1, and the power feeding circuit 19-2 is configured by connecting a diode DS and a resistor RS in series with one end thereof. The auxiliary power supply 18 is connected to a connection point between the diode DA and the capacitor CA, and the other end is connected to the plus terminal side of the capacitor CB for the bootstrap circuit.

  MOSFETs are used as the switching elements Q1, Q2, Q3, Q4, the drains of the switching elements Q1, Q3 of the upper arm are connected to the positive terminal of the battery 12, and the sources of the switching elements Q2, Q4 of the lower arm are grounded Yes. Although not shown, a parasitic diode of MOSFET is connected in antiparallel to each switching element Q1 to Q4. A connection point between the first-phase switching elements Q1 and Q2 is a first output terminal, and a connection point between the second-phase switching elements Q3 and Q4 is a second output terminal.

  That is, the inverter device includes a series circuit of switching elements Q1, Q3 and switching elements Q2, Q4 in which switching elements Q1, Q3 constituting the upper arm and switching elements Q2, Q4 constituting the lower arm are connected in series. Are connected in parallel. Upper arm drive circuits 16-1 and 16-2 are provided corresponding to switching elements Q1 and Q3, respectively, and lower arm drive circuits 14-1 and 14-2 are provided corresponding to switching elements Q2 and Q4, respectively. ing.

  When the inverter device is a single-phase inverter, the series circuit of the upper arm and the lower arm has two phases (two sets), and when the inverter device is a three-phase inverter, the switching that constitutes the upper arm and the lower arm of the third phase A series circuit in which the elements are connected in series is further provided.

  The third-phase lower-arm drive power supply circuit is configured in the same manner as the second-phase lower-arm drive power supply circuit, and a lower-arm drive circuit power supply capacitor connected in parallel to the lower-arm drive circuit includes Charging is performed by driving the switching element S of the lower arm driving power supply circuit 11 of the phase. The third-phase upper arm drive power supply circuit is configured in the same manner as the second-phase upper arm drive power supply circuit 15-2, and the auxiliary power supply 18 is shared with the first-phase upper arm drive power supply circuit 15-1. To do. The connection point between the upper arm switching element and the lower arm switching element is the third output terminal.

  The control device 20 controls the switching element S, the lower arm drive circuits 14-1 and 14-2, and the upper arm drive circuits 16-1 and 16-2. When there is a series circuit of the upper arm and the lower arm of the third phase, the lower arm driving circuit and the upper arm driving circuit are also controlled. The control device 20 switches the switching element S at a cycle shorter than the switching cycle of the lower arm drive circuits 14-1, 14-2 and the like.

Next, the operation of the inverter device configured as described above will be described.
The upper arm drive circuits 16-1 and 16-2 and the lower arm drive circuits 14-1 and 14-2 of the inverter device perform switching control of the switching elements Q1 to Q4 by a control signal from the control device 20. The switching elements Q1 and Q3 of the upper arm of each phase are not turned on at the same time, but are turned on alternately. When the switching element Q1 is on, the switching element Q2 is off, when the switching element Q2 is on, the switching element Q1 is off, and when the switching element Q3 is on, the switching element Q4 is off, When the switching element Q4 is on, the switching element Q3 is off.

  The switching element S is switched by the drive signal from the control device 20, that is, is turned on / off. When the switching element S is turned on, current flows from the battery 12 to the primary coil TC1 of the transformer T, and current also flows to the secondary coil TC2 due to the induced electromotive force. The current flowing through the secondary coil TC2 charges the power supply capacitors C2 and C4 of the lower arm drive circuits 14-1 and 14-2.

  When the switching element S is turned off, the capacitor CA of the auxiliary power supply 18 is charged by a surge voltage (spike-like high voltage) generated in the primary circuit. That is, energy is stored in the capacitor CA of the auxiliary power supply 18 using the switching surge of the switching element S. The capacitor CA is charged in a voltage state higher than the voltage of the capacitor CB of the bootstrap circuits 17-1 and 17-2. Since the switching element S is switching-controlled independently of the driving of the lower arm driving circuits 14-1 and 14-2 and the upper arm driving circuits 16-1 and 16-2, the capacitor CA of the auxiliary power source 18 is used. Is always higher than the voltage of the capacitor CB of the bootstrap circuits 17-1 and 17-2. Further, since the switching cycle of the switching element S is set shorter than the switching cycle of the lower arm drive circuits 14-1 and 14-2, the capacitor CA of the auxiliary power supply 18 is always the bootstrap circuits 17-1 and 17-2. It becomes possible to supply power to the capacitor CB. Then, a current from the capacitor CA to the capacitor CB flows through the power supply circuits 19-1 and 19-2.

  Similarly to the conventional bootstrap system, the lower arm driving circuit 14-1 (or the lower arm driving circuit 14-2) is turned on, that is, the switching element Q2 (or the switching element Q4) is turned on. When power flows through the secondary coil TC2, the current charges the capacitor CB of the bootstrap circuit 17-1 (or the bootstrap circuit 17-2).

  Therefore, the capacitors CB of the upper arm drive circuits 16-1 and 16-2 are not only charged when the corresponding lower arm drive circuit is in the ON state, as in the conventional bootstrap type, but also from the auxiliary power supply 18. It is charged with the supplied power. As a result, unlike the conventional bootstrap system, the on-time of the upper arm is not limited, and there is no problem even if the on-time is extended. The upper arm drive power supply circuits 15-1 and 15-2 have a simple configuration in which an auxiliary power supply 18 and power supply circuits 19-1 and 19-2 are added to the conventional bootstrap configuration, and a multi-output transformer is provided. Unlike the case of using it, the cost does not increase. Therefore, the switching element of the upper arm can be continuously turned on by a simple method.

According to this embodiment, the following effects can be obtained.
(1) The switching element driving power supply circuit includes an upper arm switching element Q1 and a lower arm switching element Q2 that are connected in series, and an upper arm switching element Q3 and a lower arm. A series circuit of the switching element Q4 is connected in parallel. Upper arm driving circuits 16-1 and 16-2 are provided corresponding to the switching elements Q1 and Q3 of the upper arms, respectively, and the lower arm driving circuits 14-1 are respectively corresponding to the switching elements Q2 and Q4 of the lower arms. , 14-2. The switching element drive power supply circuit includes a transformer T connected to the battery 12, a switching element S connected in series to the primary side coil TC1 of the transformer T, and a diode 13 connected to the secondary side coil TC2 of the transformer T. And a main power supply circuit 10 common to the upper arm drive circuits 16-1 and 16-2 and the lower arm drive circuits 14-1 and 14-2. The power supply capacitors C2 and C4 for the lower arm drive circuit are respectively connected in parallel to the power input sides of the lower arm drive circuits 14-1 and 14-2. A bootstrap circuit capacitor CB is connected in parallel to the power input side of each of the upper arm drive circuits 16-1 and 16-2, and one end of each of the bootstrap circuits 17-1 and 17-2 corresponds to the lower arm drive. It is connected to circuit power supply capacitors C2 and C4. Further, the upper arm driving power supply circuits 15-1 and 15-2 as the power sources of the upper arm driving circuits 16-1 and 16-2 are connected to the primary side of the transformer T and use the switching surge of the switching element S. Thus, an auxiliary power source 18 for storing energy and power supply circuits 19-1 and 19-2 for connecting the auxiliary power source 18 to the positive side terminal of the capacitor CB for the bootstrap circuit are provided. Therefore, the switching elements Q1 and Q3 of the upper arm can be continuously turned on by a simple method.

  (2) The auxiliary power supply 18 includes a diode DA and a capacitor CA. The diode DA has an anode connected to the connection point between the primary coil TC1 and the switching element S, and a cathode connected to the capacitor CA. preferable. According to this configuration, since the auxiliary power supply 18 is configured by a series circuit of the diode DA and the capacitor CA, the configuration is simplified.

  (3) The power feeding circuits 19-1 and 19-2 are configured by connecting a diode DS and a resistor RS in series, one end is connected to a connection point between the diode DA of the auxiliary power supply 18 and the capacitor CA, and the other end is connected. It is preferably connected to the positive terminal side of the capacitor CB for the bootstrap circuit. In this configuration, energy stored in the capacitor CB for the bootstrap circuit is prevented from being released to the auxiliary power supply 18 side through the power supply circuits 19-1 and 19-2.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIG. This embodiment is different from the first embodiment in that the power supply circuits 19-1 and 19-2 are provided with a switch circuit (switching circuit) linked to the drive signals of the upper arm drive circuits 16-1 and 16-2. Different. The same parts as those in the first embodiment are denoted by the same reference numerals and detailed description thereof is omitted. FIG. 2 shows only the circuit configuration for driving the upper and lower arms of the first phase.

  As shown in FIG. 2, a switch circuit 21 is provided in the power supply circuit 19-1 that connects the auxiliary power supply 18 and the capacitor CB of the bootstrap circuit 17-1. The switch circuit 21 is composed of, for example, a switching element and is driven by a drive signal from the control device 20. The drive signal for turning on the switch circuit 21 is output in synchronization with the drive signal to the upper arm drive circuit 16-1, and the switch circuit 21 is turned on only when the upper arm drive circuit 16-1 is turned on. . Similarly, the circuit configuration for driving the upper arm of the second phase is provided with a similar switch circuit in the power feeding circuit 19-2.

Therefore, according to the second embodiment, the following effects can be obtained in addition to the effects (1) to (3) described in the first embodiment.
(4) The switching element S is driven independently of the driving of the upper arm driving circuits 16-1 and 16-2. Therefore, when there is no switch circuit 21, the voltage charged in the capacitor CB of the bootstrap circuit 17-1 becomes higher than necessary, and the upper arm drive circuits 16-1 and 16-2 can be driven (switched) smoothly. There is a risk that it will not be performed. However, in this embodiment, the capacitor CB can be charged from the auxiliary power supply 18 only when the upper arm drive circuits 16-1 and 16-2 are turned on. As a result, it is avoided that the voltage of the charged capacitor CB becomes higher than necessary. In addition, the capacity of the auxiliary power source 18 can be reduced, and the size can be reduced.

The embodiment is not limited to the above, and may be embodied as follows, for example.
The switching elements Q1 to Q4 are not limited to MOSFETs, and other power transistors (for example, IGBT (insulated gate bipolar transistor)) or thyristors may be used.

  ○ The position of the diode DS constituting the power supply circuits 19-1 and 19-2 is such that when the switching element S is on, a current is passed from the capacitor CB of the bootstrap circuits 17-1 and 17-2 to the capacitor CA of the auxiliary power supply 18. Any position that prevents flow can be used. For example, in the series circuit of the diode DS and the resistor RS, the cathode of the diode DS is connected to the positive terminal side of the capacitor CB for the bootstrap circuit, and the anode of the diode DS is connected to the diode DA and the capacitor of the auxiliary power supply 18 via the resistor RS. You may connect to the connection point with CA. That is, the anode side of the diode DS is connected to the connection point between the diode DA of the auxiliary power supply 18 and the capacitor CA, and the cathode side of the diode DS is connected to the plus terminal side of the capacitor CB for the bootstrap circuit.

  The switch circuit 21 provided in the power supply circuits 19-1 and 19-2 is not limited to be provided between the resistor RS and the capacitor CB, and may be provided between the diode DS and the resistor RS or on the anode side of the diode DS. Good.

  The switching cycle of the switching element S connected to the primary coil TC1 of the transformer T is set shorter than the on / off cycle of the lower arm drive circuits 14-1 and 14-2, and the lower arm drive circuit 14-1 It may be changed corresponding to the change of the ON / OFF cycle of 14-2. If the switching cycle of the switching element S is set shorter than the switching cycle of the lower arm drive circuits 14-1 and 14-2, the capacitor CA of the auxiliary power supply 18 is always the capacitor of the bootstrap circuits 17-1 and 17-2. It becomes possible to supply power to CB. However, the ON / OFF cycle of the lower arm drive circuits 14-1 and 14-2 is not always constant and may be changed depending on the output state required for the inverter device. If the switching cycle of the switching element S is set to be shorter than the shortest switching cycle of the lower arm drive circuits 14-1 and 14-2, the capacitor CA of the auxiliary power supply 18 is always connected to the bootstrap circuits 17-1 and 17-2. The electric power can be supplied to the capacitor CB. However, in this case, if the switching cycle of the lower arm driving circuits 14-1 and 14-2 continues to be long, the capacitor CA is charged more than necessary, so the capacitance of the capacitor CA needs to be increased. . By changing the switching cycle of the switching element S in accordance with the change of the ON / OFF cycle of the lower arm drive circuits 14-1 and 14-2, it is not necessary to increase the capacitance of the capacitor CA.

  The capacitor C0 connected in parallel with the battery 12 on the primary side of the transformer T may be omitted. However, in the configuration in which the capacitor C0 is connected in parallel, when the switching element S is turned on, the current is smoothly supplied even when a large current is required for the primary coil TC1.

  ○ Each upper arm and each lower arm has been described as being composed of one switching element and one diode, but if the amount of current flowing through each arm is large, each arm is connected to the switching element and diode. There may be a configuration in which a plurality of sets are connected in parallel.

The direct current power supply is not limited to the battery 12 and may be configured to supply direct current obtained by converting a commercial alternating current power supply using an AC / DC converter.
○ The inverter device is not limited to the motor drive power source, but may be used as a power source for AC electrical equipment other than the motor.

The following technical idea (invention) can be understood from the embodiment.
(1) In the invention according to any one of claims 1 to 3, the power supply circuit is a switch that is turned on only when the upper arm drive circuit to which the power supply circuit is connected is in an on state. It has a circuit.

  (2) In the invention according to any one of claims 1 to 3 and the technical idea (1), the switching cycle of the switching element connected to the primary coil of the transformer is the lower arm drive. It is set shorter than the on / off cycle of the circuit, and is changed in response to the change of the on / off cycle of the lower arm drive circuit.

  T: Transformer, S: Switching element, C0, CA, CB: Capacitor, C2, C4: Power supply capacitor, DA, DB, DS, 13: Diode, Q1, Q3: Switching element as upper arm switching element, Q2, Q4 ... switching element as lower arm switching element, RB, RS ... resistor, TC1 ... primary side coil, TC2 ... secondary side coil, 10 ... main power supply circuit, 14-1, 14-2 ... lower arm drive circuit, 16- DESCRIPTION OF SYMBOLS 1,16-2 ... Upper arm drive circuit, 17-1, 17-2 ... Bootstrap circuit, 18 ... Auxiliary power supply, 19-1, 19-2 ... Power feeding circuit.

Claims (3)

A plurality of series circuits of upper arm switching elements and lower arm switching elements connected in series constituting the upper arm and the lower arm are connected in parallel, and an upper arm driving circuit is provided for each of the upper arm switching elements. A switching element driving power supply circuit of an inverter device provided with a lower arm driving circuit corresponding to each of the lower arm switching elements,
A transformer connected to a DC power source, a switching element connected in series to a primary coil of the transformer, and a rectifier connected to a secondary coil of the transformer, each upper arm drive circuit and the A main power supply circuit common to each lower arm drive circuit;
A power capacitor for the lower arm drive circuit connected in parallel to the power input side of each lower arm drive circuit, and
Connected to the power input side of each upper arm driving circuit, and a capacitor for a bootstrap circuit is connected in parallel with each upper arm driving circuit, and one end is connected to the corresponding power capacitor for the lower arm driving circuit. Bootstrap circuit,
An auxiliary power source connected to the primary side of the transformer and storing energy using a switching surge of the switching element;
A switching element driving power supply circuit for an inverter device, comprising: a power supply circuit for connecting the auxiliary power supply to a positive terminal of a capacitor for the bootstrap circuit.   The inverter according to claim 1, wherein the auxiliary power source includes a diode and a capacitor, and the diode has an anode connected to a connection point between the primary coil and the switching element, and a cathode connected to the capacitor. Switching element drive power supply circuit of the device.   The power supply circuit is configured by connecting a diode and a resistor in series, an anode side of the diode is connected to a connection point between the diode and the capacitor of the auxiliary power supply, and a cathode side of the diode is used for the bootstrap circuit. The switching element driving power supply circuit of the inverter device according to claim 2, wherein the switching element driving power supply circuit is connected to a positive terminal side of the capacitor.