JP2015076979A - Leakage current suppression circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a leakage current suppression circuit that uses a compact active filter applicable even to an inverter with a high voltage rating, and has favorable responsiveness.SOLUTION: A common mode voltage detection section 6 detects from a power line a common mode voltage generated by a switching operation of a power conversion apparatus. A feedback section 8 computes an amplification voltage which brings the detected common mode voltage to the same potential as a neutral potential of a DC current line. A cancellation voltage application section 10 applies the amplification voltage to the power line of the power conversion apparatus. A voltage-controlled power supply section 9 comprises a plurality of NPN transistors and a plurality of PNP transistors arranged polarity-symmetrically. The plurality of NPN transistors are connected so as to divide a voltage between the detected common mode voltage and a positive DC current side of the DC current line. The plurality of PNP transistors are connected so as to divide a voltage between the detected common mode voltage and a negative DC current side of the DC current line.

Description

  Embodiments described herein relate generally to a leakage current suppressing circuit.

  A power converter represented by an inverter performs power conversion by a switching operation of a semiconductor switching element. Taking a three-phase PWM inverter that drives a motor as an example, a command value of a voltage to be output is compared with a carrier such as a triangular wave, and the semiconductor elements of each phase are switched based on the comparison result.

  At this time, on the principle, the common mode voltage indicating the average value of the three-phase UVW phase output voltages is not zero, and a large voltage is generated in synchronization with the carrier. This common mode voltage causes a leakage current (high-frequency noise) that flows to the ground via the stray capacitance of the motor. Since leakage current causes problems such as causing trouble to other devices, countermeasures against leakage current are indispensable. As an effective countermeasure, there is a filter circuit composed of passive elements such as coils and capacitors (see Patent Documents 1 and 2).

  In addition to LC passive filters such as Patent Documents 1 and 2, an active filter circuit that actively cancels a common mode voltage using a semiconductor element has been proposed (see Patent Document 3). In FIG. 10, a common mode voltage generated by switching of an inverter is detected by a capacitor, and an emitter follower composed of a bipolar transistor is used as a voltage control type power source, and a voltage is applied to a common mode transformer. The common mode transformer is a transformer wound around the three-phase output line of the inverter, and the voltage output from the emitter follower is applied to the three-phase line. As a result, the common mode voltage generated from the three-phase output is canceled.

Japanese Patent No. 4351916 Japanese Patent No. 3596694 Japanese Patent Laid-Open No. 10-94244

  However, in the filter circuit having the configuration as disclosed in Patent Documents 1 and 2, the bypass circuit is large such that the common mode current extraction circuit includes three single-phase reactors, which leads to an increase in the size of the entire filter circuit. In addition, when the DC voltage of the inverter circuit is high, the emitter follower type active filter circuit as in Patent Document 3 is limited by the breakdown voltage of the transistor, and the application range is limited.

  Furthermore, when a voltage that cancels the common mode voltage is generated using a filter circuit, a delay occurs due to the response performance of the transistors in the filter. The delay is caused by the response speed of the transistors in the filter. In particular, when a transistor with a high breakdown voltage is used, a transistor with a high breakdown voltage has a slow response performance, and thus the delay increases.

  Therefore, the embodiment of the present invention has been proposed to solve the above-described problems of the prior art, uses a small active filter that can be applied to a high voltage rated inverter, and has excellent responsiveness. A leakage current suppression circuit is provided.

In order to achieve the above object, an embodiment of the present invention is a leakage current suppression circuit of a power conversion device that performs power conversion by switching a power semiconductor element and has the following configuration.
(A) A common mode voltage detector that detects a common mode voltage generated by a switching operation of the power conversion device from a power supply line.
(B) A neutral point potential detection unit that detects a neutral point potential of the DC current line of the power conversion device.
(C) A feedback unit that calculates an amplification voltage that makes the detected common mode voltage the same potential as the neutral point potential of the DC current line.
(D) A voltage-controlled power supply unit that generates an amplified voltage calculated by the feedback unit.
(E) A cancel voltage application unit that applies the generated amplified voltage to a power supply line of the power conversion device.
(F) The voltage-controlled power supply unit arranges a plurality of NPN transistors and a plurality of PNP transistors symmetrically.
(G) The plurality of NPN transistors are connected so as to divide a voltage between a common mode voltage detected by a common mode voltage detector and a DC current positive side of the DC current line.
(H) The plurality of PNP transistors are connected so as to divide a voltage between the common mode voltage detected by the common mode voltage detection unit and the DC current negative side of the DC current line.

It is a block diagram which shows the structure of the leakage current suppression circuit of 1st Embodiment. It is a block diagram of the emitter follower circuit which is a voltage control type power supply part of 1st Embodiment. It is a figure which shows a common mode equivalent circuit when there is no filter. It is a figure which shows the common mode equivalent circuit of 1st Embodiment. It is a graph which shows the leakage current at the time of applying the leakage current suppression circuit of 1st Embodiment. 3 is a timing chart of inverter three-phase switching, common mode voltage, and leakage current. It is a timing chart of three-phase switching of an inverter, common mode voltage, and leakage current (when three-phase switching is complete). FIG. 5 is a circuit diagram in the case of using a push-pull type emitter follower circuit using one NPN type transistor and one PNP type transistor. It is a graph which shows the emitter voltage of the transistors 17, 18, and 19 when the leakage current suppression circuit is operating. It is a block diagram which shows the structure of the leakage current suppression circuit of 2nd Embodiment.

  Hereinafter, embodiments of a leakage current suppressing circuit according to the present invention will be described in detail with reference to the drawings. In the embodiment, description of overlapping drawings is omitted.

[1. First Embodiment]
Hereinafter, the leakage current suppressing circuit according to the first embodiment will be described with reference to FIGS. The leakage current suppression circuit of the present embodiment is provided in a power converter, and detects a common mode voltage with respect to the ground of the power converter. A voltage at which the common mode voltage becomes the same potential as that of the ground is generated by the voltage control type power supply unit in the leakage current suppression circuit and applied to the power converter. That is, the common mode voltage of the power conversion device is canceled out by a voltage having the same amplitude in the opposite phase generated in the voltage-controlled power supply unit. That is, it is canceled.

In the present embodiment, the voltage control type power supply unit is configured by a plurality of transistors, so that the voltage applied to one transistor is divided and the characteristics of the capacitor are selected depending on the arrangement location. Further, in order to improve the responsiveness, feedback control is performed so that the detected common mode voltage becomes the same potential as the neutral point potential of the DC current line.
[1-1. Constitution]
[Basic configuration]

  FIG. 1 is a diagram schematically illustrating a configuration example of a leakage current suppression circuit A in the power conversion device B of the first embodiment. The leakage current suppression circuit A of the present embodiment is provided in the power conversion device B. The power conversion device B performs power conversion by the switching operation of the semiconductor switching element. The power converter B includes a converter 1, a smoothing capacitor 2, an inverter 3, a load 4, and a power supply 5.

  The converter 1 is connected to a power source 5 through a power line, and converts a three-phase voltage supplied from the power source 5 into a DC voltage. The converter 1 inputs a three-phase voltage from the power supply line and outputs it to the DC current line. The power supply line is composed of three phases of U, V, and W. The DC current line is composed of a DC current positive side and a DC current negative side line.

  The smoothing capacitor 2 is connected to a direct current line connected between the converter 1 and the inverter 3. One terminal of the smoothing capacitor 2 is connected to the DC current positive side line of the DC current line, and the other terminal is connected to the DC current negative side.

  The inverter 3 is a so-called PWM inverter that converts direct current into alternating current by switching. The inverter 3 receives the direct current smoothed by the smoothing capacitor 2 from the direct current line, converts it into a three-phase alternating current having a desired magnitude and frequency, and outputs it to the output line. Each phase of the output of the inverter 3 includes two switching elements and constitutes three phases of U, V, and W.

  The load 4 is a load connected to the inverter 3 and is applied with the three-phase AC voltage output from the inverter 3. Examples of the load 4 include a motor. The load 4 is connected to the ground, and when a motor is used as the load 4, the frame of the motor is connected to the ground.

  The power source 5 is a three-phase AC power source, and is an AC power source combining three systems of single-phase AC with current or voltage phases shifted from each other. The three-phase power output from the power supply 5 constitutes three phases of U, V, and W.

  In the present embodiment, the leakage current suppression circuit A is connected to the power conversion device B having the above configuration. The current suppression circuit A of the present embodiment detects a common mode voltage with respect to the ground of the power converter B and applies a voltage to the power converter B such that this voltage has the same potential as the ground. The current suppression circuit A includes a common mode voltage detection unit 6, a neutral point potential detection unit 7, a feedback unit 8, a voltage control type power supply unit 9, and a cancel voltage application unit 10.

  The common mode voltage detection unit 6 detects a common mode voltage generated by switching of the power converter B. The common mode voltage detection unit 6 is configured to be able to detect the common mode voltage flowing in the three phases U, V, and W of the output line of the power converter B. That is, the common mode voltage detection unit 6 includes three capacitors, and one terminal of each capacitor is connected to the three phases U, V, and W of the three-phase power line of the power converter B. The other terminal of the capacitor is connected to one and connected to the feedback unit 8.

  The neutral point potential detector 7 detects the neutral point voltage of the direct current line. The neutral point potential detector 7 is composed of two capacitors. One terminal of each capacitor is connected to the DC current line of the power converter B. One of the two capacitors connects one of the terminals to the DC current positive side, and the other of the two capacitors connects one of the terminals to the DC current negative line. That is, the two capacitors are connected to different lines. The other terminal of each capacitor is connected to one and connected to the feedback unit 8.

  The feedback unit 8 calculates an amplified voltage that makes the common mode voltage detected by the common mode voltage detection unit 6 the same potential as the neutral point potential of the DC current line detected by the neutral point potential detection unit 7. This amplified voltage is output to the voltage controlled power supply unit 9. A so-called feedback circuit can be used as the feedback unit 8. The output side of the voltage controlled power supply unit 9 is connected to the voltage controlled power supply unit 9.

  The voltage-controlled power supply unit 9 impedance-converts the amplified voltage amplified by the feedback unit 8 and outputs it. The voltage control type power supply unit 9 of this embodiment is a push-pull type emitter follower circuit using a plurality of NPN and PNP type transistors. The emitter follower circuit of the voltage control type power supply unit 9 has the same number of NPN and PNP type transistors, and has the same number of voltage dividing resistors and voltage dividing capacitors as the NPN and PNP type transistors. Although the number of NPN and PNP transistors is arbitrary, the configuration of a push-pull emitter follower circuit using three NPN and PNP transistors will be described below.

  A push-pull type emitter follower circuit is a circuit in which two groups of amplifying elements are connected symmetrically. As shown in FIG. 2, one group includes three NPN transistors 12, 13, and 14, three voltage dividing resistors 15a, b, and c, and three voltage dividing capacitors 16a, b, and c. .

  The base side of one group of transistors 12 is connected to the feedback unit 8. The emitter side of the transistor 12 is connected to the cancel voltage applying unit 10, and the collector side is connected to the emitter side of the transistor 13. The collector side of the transistor 13 is connected to the emitter side of the transistor 14. The base sides of the transistors 13 and 14 and the emitter side of the transistor 12 are connected to a direct current line via a voltage dividing resistor 15 and a voltage dividing capacitor 16.

  The cancel voltage application unit 10 in FIG. 1 is a so-called common mode transformer, and includes three coils connected to the three-phase power supply line and one coil connected to the voltage-controlled power supply unit 9. Each coil is wound in such a direction that a voltage having a phase opposite to that applied to the coil connected to the voltage-controlled power supply unit 9 is applied to the three-phase power supply line. That is, by the combination of the coils, a voltage having an opposite phase to the amplified voltage output from the voltage control type power supply unit 9 is applied to the three-phase power supply line.

  The cancel voltage application unit 10 includes a main winding 11a connected to each phase wiring extending from the power supply 5, an auxiliary winding 11b connected to the voltage control type power supply unit 9, a main winding 11a, and an auxiliary winding 11b. And a attached core. In this embodiment, the direction in which the main winding 11a and the auxiliary winding 26b are wound around the core is the same. The ratio of the number of turns of the main winding and the auxiliary winding is 1: 1.

[1-2. Action]
In the present embodiment, leakage current generated by switching in the power conversion device B is suppressed.

  FIG. 3 shows a common mode equivalent circuit of a conventional inverter system. The power supply side is connected to the ground via a LISN (Line Impedance Stabilization Network) of a noise measurement circuit. The motor side is connected to the ground through a stray capacitance between the motor winding and the frame (the frame is grounded). In addition, there is a parasitic inductance of the circuit, and common mode potential fluctuation due to switching is expressed as a switching voltage source. That is, the leakage current flows due to the switching voltage generated with respect to the impedance of the series LCR circuit of various parasitic components.

  On the other hand, FIG. 4 shows a common mode equivalent circuit when the leakage current suppression circuit A of the present embodiment is added. A common mode voltage is detected by the common mode voltage detector 6. Further, since the potential detected by the voltage control type power supply unit 9 is substantially the same potential as the ground, it is shown as detection of the ground potential. The feedback unit 8 operates so that these two potential differences become zero, and outputs the calculation result to the voltage source. The voltage source is a part constituted by a voltage control type power supply unit 9 and a cancel voltage application unit 10. It operates so that the common mode potential fluctuation of the output part of the circuit by these structures becomes zero.

  As a result, the leakage current is reduced as shown in FIG. When there is no leakage current suppression circuit A, a leakage current close to 6 A flows, whereas when there is a leakage current suppression circuit A, almost no leakage current is detected.

  Hereinafter, the operation of the leakage current suppression circuit of the present embodiment will be described in detail.

(Generation of common mode voltage)
The inverter 3 is a voltage type PWM inverter, and the common mode voltage fluctuates every time switching is performed. That is, the common mode voltage generated by the switching of the power converter B causes a leakage current flowing to the ground via the motor frame. Since this leakage current flows in both the DC current positive side and the DC current negative side of the DC current line, voltage fluctuation occurs with respect to the ground on both the DC current positive side and the DC current negative side.

  FIG. 6 shows a change in common mode voltage and a leakage current due to a change in the three-phase inverter terminal voltage due to switching. Each time the U-phase voltage, V-phase voltage, and W-phase voltage are applied, the common mode voltage changes from 0 V to 1/3 Vdclink, 2/3 Vdclink, and Vdclink. The leakage current flows at the moment of change of the common mode voltage, and increases as the change of the common mode voltage increases.

  In the case of three phases, the change of the common mode voltage is the largest when the switching timings of the three phases shown in FIG. In this case, the output voltage of the inverter 3 is zero.

(Common mode voltage detection)
The common mode voltage detector 6 detects a common mode voltage with respect to the ground. Voltage fluctuation occurs with respect to the ground on both the DC current positive side and DC current negative side lines. The common mode voltage generated in this way is detected by the common mode voltage detector 6. The frequency of the common mode voltage that can be detected depends on the capacitance of the capacitor. The common mode voltage detection unit 6 outputs the detected common mode voltage to the feedback unit 8.

(Detection of neutral point potential)
The neutral point potential detector 7 detects the neutral point potential of the direct current line. Since the neutral point potential of the DC current line is substantially the same potential as the ground, the detected potential can be treated as the ground potential. The potential detected by the neutral point potential detection unit 7 is output to the feedback unit 8.

(Feedback control)
The feedback unit 8 calculates an amplified voltage that makes the detected common mode voltage the same potential as the neutral point potential of the DC current line. The feedback unit 8 determines the amplified voltage to be output so that the amplified voltage that is the result of the calculation is the same potential as the neutral point potential of the DC current line.

(Voltage control)
The voltage control type power supply unit 9 generates the amplified voltage amplified by the feedback unit 8. The voltage control type power supply unit 9 performs voltage control by impedance-converting and outputting the amplified voltage amplified by the feedback unit 8.

  FIG. 8 is a circuit diagram when a push-pull type emitter follower circuit using NPN and PNP type transistors one by one is used as the voltage control type power supply unit 9. When the voltage input to the base side of the transistor is output from the emitter side in the voltage-controlled power supply unit 9 of FIG. 8, the maximum Vce of each transistor includes the collector side of the upper transistor, that is, the DC link voltage positive side. A voltage between the collector of the lower transistor, that is, the negative side of the DC link voltage may be applied.

  For example, when the DC link voltage is 600V and the base potential is 0V, Vce of the upper transistor reaches 600V. It is difficult to apply such a high breakdown voltage transistor.

  On the other hand, in this embodiment, as shown in FIG. 2, the emitter-follower circuit of the voltage-controlled power supply unit 9 has the same number of NPN and PNP transistors, and the total number of NPN and PNP transistors. It has the same number of voltage dividing resistors and voltage dividing capacitors. In the voltage controlled power supply unit 9 of this embodiment, the output voltage of the feedback unit 8 is input to the bases of the transistor 12 and the transistor 20. The transistors 12 and 17 output from the emitter a voltage substantially equal to the base voltage (strictly speaking, there is a difference of Vbe = 0.6 to 0.7 V).

  The output voltage of the feedback unit 8 is input to the transistor 12 and the transistor 17. Whether the transistor 12 or the transistor 17 operates depends on whether the input base voltage is larger or smaller than the midpoint voltage of the DC link voltage. Determined by. Therefore, Vce of the transistors 12 and 17 changes so that the output voltage of the feedback circuit is output from the emitter.

  As shown in FIG. 8, when the voltage controlled power supply unit 9 has only two transistors, the difference between the DC link voltage Vdclink and the base voltage becomes Vce as it is. On the other hand, in the emitter follower circuit of this embodiment, the transistors 13 and 14 (or 18, 19) act so as to disperse Vce.

  As the base voltages of the transistors 13 and 14, a voltage obtained by dividing the output voltage of the emitter follower circuit of the transistors 12 and 17 and the DC link voltage Vdclink by the resistor 23 is input.

  For example, the output voltage of the feedback circuit is 0V, the DC link voltage Vdclink is 600V, and the voltage dividing ratio of the resistor 23 is 23a: 23b: 23c: 23d: 23e: 23f = 2: 2: 1: 1: 2: 2. To do. At this time, if the emitters of the transistors 12 and 17 output 0 V, the base voltage of the transistor 14 is 600 V × (1 + 2) / 5 = 240 V. Similarly, the base voltage of the transistor 13 is 600V × 1/5 = 120V.

  Since the transistors 14 and 13 also perform the emitter follower operation, the emitter voltage of the transistor 14 is 240V and the emitter voltage of the transistor 13 is 120V. At this time, considering the Vce of each transistor, the Vce of the transistor 12 is 120 V, the Vce of the transistors 13 and 14 is 240 V, and each Vce is dispersed by the resistance.

  While the upper emitter follower operation by the NPN transistors 12, 13, and 14 has been described above, the operation of the lower PNP transistors 17, 18, and 19 is the same.

  Further, as shown in the example, if the Vce of the central transistors 12 and 17 is set to be the smallest as shown in the example, the transistors 12 and 17 can use a high-speed transistor with a low breakdown voltage. . That is, since the emitter week force of the transistors 12 and 17 determines the voltage to be applied to the cancel voltage application unit 11, an effect of suppressing EMI up to a high frequency can be obtained by using a faster transistor. On the other hand, since the main purpose of the transistors 12, 14, 18, and 19 is to distribute the breakdown voltage, it is desirable to select a high breakdown voltage and low speed transistor. The voltage dividing capacitor 16 connected in parallel with the voltage dividing resistor 15 has an effect of suppressing transient voltage fluctuations.

  FIG. 9 shows the emitter voltages of the transistors 12, 13, and 14 when the leakage current suppression circuit A is operating. The DC link voltage is 600 V, and the voltage division ratio is 1: 1: 1: 1: 1: 1. The emitter voltage of the transistor 12 is almost the same voltage as the detected common mode voltage, and it can be seen that the transistors 13 and 14 output a voltage corresponding to the voltage division ratio and distribute Vce.

(Cancel common mode voltage)
The cancel voltage application unit 10 applies the voltage output from the voltage control type power supply unit 9 to the three-phase power line. As a result, the potential of the converter with respect to the ground fluctuates so that the potential fluctuation of the three-phase output voltage becomes a neutral point potential, that is, zero, so that the influence of the common mode voltage generated by the power converter B is cancelled. .

[1-3. effect]
According to the leakage current suppression circuit A of the present embodiment, the common mode voltage with respect to the ground of the power converter B is detected, and the voltage at which the common mode voltage becomes the same potential as the ground is controlled by the voltage control in the current suppression circuit A. It is generated by the mold power supply unit 9 and applied to the power converter B.

  When the DC voltage rating of the inverter circuit is high, the DC link voltage of the voltage-controlled power supply unit 9 is often high. For this reason, it is necessary to increase the breakdown voltage of the transistor of the voltage-controlled power supply unit 9, which is a limitation. However, in this embodiment, by using a plurality of transistors in the voltage controlled power supply unit 9, the voltage applied to the transistors of the voltage controlled power supply unit 9 can be distributed. Can be achieved.

  Furthermore, in this embodiment, since the voltage applied to the transistors of the voltage-controlled power supply unit 9 can be distributed, it is possible to select a portion of the transistors that contribute to responsiveness with priority on responsiveness. Thereby, the delay with respect to the common mode voltage of the current which cancels the common mode voltage can be reduced.

  Further, the voltage input to the voltage control type power supply unit 9 is calculated in advance so as to be feedback controlled by the feedback unit 8. Therefore, the common mode voltage generated by switching is brought close to the ground potential in a short time. It is possible.

  As described above, in the present embodiment, the portion of the transistor that contributes to the responsiveness of the voltage controlled power supply unit 9 is selected with priority given to the responsiveness, and the voltage input to the voltage controlled power supply unit 9 is Responsiveness can be improved by performing feedback control.

[2. Second Embodiment]
[2-1. Constitution]
The leakage current suppression circuit A according to the second embodiment is obtained by adding a common mode choke coil 22 to the three-phase output line to the leakage current suppression circuit A of the first embodiment, and with respect to the common mode current flowing in the high frequency band. Impedance.

  A second embodiment will be described with reference to FIG. As shown in FIG. 10, a common mode choke coil 22 is connected to the three-phase output line. The common mode choke coil 22 has a characteristic of acting with a large impedance against a current flowing in a high frequency band.

[2-2. Effect]
In the current suppression circuit A having the above configuration, in addition to the effect of the first embodiment, a common mode current that slightly flows in a high frequency band is caused to be generated in the common mode choke coil 20 due to the limitation of the high frequency characteristics of the transistor. It can be suppressed by impedance.

[3. Other Embodiments]
In the present specification, a plurality of embodiments according to the present invention have been described. However, these embodiments are presented as examples and are not intended to limit the scope of the invention. Specifically, various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and equivalents thereof as well as included in the scope and gist of the invention.

  Further, a combination of all or any of the first to second embodiments is also included, and the present invention can be implemented in various other forms.

A ... Leakage current suppression circuit B ... Power conversion device 1 ... Converter 2 ... Smoothing capacitor 3 ... Inverter 4 ... Load 5 ... Power supply 6 ... Common mode voltage detection unit 7 ... Neutral point potential detection unit 8 ... Feedback unit 9 ... Voltage control Type power supply 10 ... Cancel voltage application 11a ... Main winding 11b ... Main winding 12 ... NPN transistor 13 ... NPN transistor 14 ... NPN transistors 15, 15a-c ... Voltage dividing resistors 16, 16a-c ... min Capacitor 17 ... PNP transistor 18 ... PNP transistor 19 ... PNP transistor 20 ... NPN transistor 21 ... PNP transistor 22 ... Common mode choke coil

Claims (7)

A leakage current suppression circuit for a power conversion device that performs power conversion by switching a power semiconductor element,
A common mode voltage detector that detects a common mode voltage generated by a switching operation of the power conversion device from a power supply line;
A neutral point potential detection unit for detecting a neutral point potential of the DC current line of the power conversion device;
A feedback unit that calculates an amplification voltage that makes the detected common mode voltage the same potential as a neutral point potential of the DC current line;
A voltage-controlled power supply unit that generates an amplified voltage calculated by the feedback unit;
A cancel voltage application unit for applying the generated amplified voltage to a power supply line of the power conversion device;
With
The voltage-controlled power supply unit is
A plurality of NPN-type transistors and a plurality of PNP-type transistors are arranged symmetrically.
The plurality of NPN transistors are connected so as to divide a voltage between a common mode voltage detected by a common mode voltage detector and a DC current positive side of the DC current line,
The plurality of PNP transistors are connected so as to divide a voltage between a common mode voltage detected by a common mode voltage detection unit and a DC current negative side of the DC current line. circuit. The NPN transistor of the voltage control type power supply unit is
A first NPN transistor connected to the cancel voltage application unit;
A base side comprising a second NPN transistor connected to the DC current positive side of the DC current line;
2. The leakage according to claim 1, wherein the emitter side of the first NPN transistor and the base side of the second NPN transistor are connected to the DC current positive side via a voltage dividing resistor. Current suppression circuit. The NPN transistor of the voltage control type power supply unit is
A first NPN transistor connected to the cancel voltage application unit;
A base side comprising a second NPN transistor connected to the DC current positive side of the DC current line;
The leakage according to claim 1, wherein the collector side of the first PNP transistor and the base side of the second NPN transistor are connected to the DC current positive side via a voltage dividing resistor. Current suppression circuit.   The leakage current suppression circuit according to claim 2, wherein the voltage dividing resistors are plural.   5. The voltage dividing ratio with respect to the PNP type transistor or the NPN type transistor is set such that a voltage dividing ratio of a transistor connected to a cancel voltage applying unit is smaller than a voltage dividing ratio of another transistor. The leakage current suppression circuit according to item. The cancel voltage application unit
6. The leakage current suppression circuit according to claim 1, wherein a winding ratio between the winding connected to the power supply line and the auxiliary winding is 1: 1.   The leakage current suppression circuit according to claim 1, wherein a common mode choke coil is provided in a power supply line of the inverter device.