JP2016181970A - Power conversion device and power conversion device control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power conversion device and a power conversion device control method, which can discharge power stored in a smoothing capacitor without an increase in device scale.SOLUTION: A power conversion device comprises: a semiconductor switch group which includes a smoothing capacitor C1 and a plurality of series connected circuits of a plurality of semiconductor switches; and a control part for switching ON and OFF of each of semiconductor switches Tr1-Tr6 included in the semiconductor switch group. The control part includes a gate drive circuit 21, a main control circuit 22 and a vehicle control circuit 15. When DC power is converted to AC power, a turn-on time of each semiconductor switch is assumed to be a first turn-on time and when power stored in the smoothing capacitor is discharged, the turn-on time of at least one semiconductor switch included in each series-connected circuit is changed to a second turn-on time longer than the first turn-on time.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a power conversion device that converts direct current power into alternating current power, and a control method for the power conversion device, and more particularly to a technique for discharging power stored in a smoothing capacitor.

  For example, a power converter such as an inverter provided in an electric vehicle includes a smoothing capacitor. In such a power converter, it is necessary to discharge the electric power (residual charge) accumulated in the smoothing capacitor when the vehicle is stopped or an accident occurs. As a conventional example of a method for discharging a smoothing capacitor, for example, one disclosed in JP 2012-205428 A (Patent Document 1) is known. In Patent Document 1, a series connection circuit of a discharge resistor and a semiconductor switch is mounted in parallel with a smoothing capacitor. Then, when the relay that connects the inverter and the power supply is released when stopping the drive of the inverter, the semiconductor switch is turned on in conjunction with this, and the current stored in the smoothing capacitor is caused to flow through the discharge resistor. Is consumed.

JP 2012-205428 A

  However, in the conventional technique disclosed in Patent Document 1 described above, in order to discharge the electric power stored in the smoothing capacitor, it is necessary to additionally mount a semiconductor switch capable of withstanding a high voltage, which increases the scale of the device. Problem occurs.

  The present invention has been made to solve such a conventional problem, and the object of the present invention is to discharge the electric power stored in the smoothing capacitor without increasing the scale of the apparatus. An object of the present invention is to provide a power converter and a method for controlling the power converter.

  To achieve the above object, a power conversion device according to the present invention includes a smoothing capacitor, a semiconductor switch group including a plurality of series connection circuits of a plurality of semiconductor switches, and a control unit that switches each semiconductor switch included in the semiconductor switch group. With. Then, the control unit sets the turn-on time of each semiconductor switch as the first turn-on time when converting DC power to AC power, and discharges the power stored in the smoothing capacitor in series of each system. A turn-on time of at least one semiconductor switch included in the connection circuit is set as a second turn-on time longer than the first turn-on time.

  Further, according to the control method of the power conversion device of the present invention, when converting DC power to AC power, the turn-on time of each semiconductor switch of a semiconductor switch group including a plurality of series connection circuits of a plurality of semiconductor switches is set. The semiconductor switch is switched at the first turn-on time. When discharging the electric power stored in the smoothing capacitor for smoothing the DC power, the turn-on time of at least one semiconductor switch included in the series connection circuit of each system is set to a second time longer than the first turn-on time. Each semiconductor switch is turned on as a turn-on time.

  In the power conversion device and the method for controlling the power conversion device according to the present invention, the semiconductor switch is turned on in the second turn-on time, so that the electric power stored in the smoothing capacitor is discharged without increasing the device scale. Is possible.

It is a block diagram which shows the structure of the power converter device which concerns on 1st-5th embodiment of this invention, and its peripheral device. It is a circuit diagram which shows the structure of the gate drive circuit provided in the power converter device which concerns on 1st Embodiment of this invention. It is a flowchart which shows the operation | movement at the time of abnormality detection of the power converter device which concerns on 1st Embodiment of this invention. It is a flowchart which shows the operation | movement at the time of abnormality solution of the power converter device which concerns on 1st Embodiment of this invention. It is a timing chart which shows change of each signal at the time of abnormality detection of a power converter concerning a 1st embodiment of the present invention. It is a timing chart which shows the change of each signal at the time of abnormality solution of the power converter concerning a 1st embodiment of the present invention. 6 is a graph showing changes in the voltage and current of the semiconductor switch that change with the first turn-on time and the second turn-on time according to the first embodiment of the present invention. It is explanatory drawing which shows the flow of the electric current at the time of discharging the smoothing capacitor of the power converter device which concerns on 1st Embodiment of this invention. It is a circuit diagram which shows the structure of the gate drive circuit provided in the power converter device which concerns on 2nd Embodiment of this invention. It is a circuit diagram which shows the structure of the gate drive circuit provided in the power converter device which concerns on 3rd Embodiment of this invention. It is a circuit diagram which shows the structure of the gate drive circuit provided in the power converter device which concerns on 4th Embodiment of this invention. It is a timing chart which shows change of each signal at the time of abnormality detection of a power converter concerning a 5th embodiment of the present invention. It is a block diagram which shows the structure of the power converter device which concerns on 6th Embodiment of this invention, and its peripheral device. It is a timing chart which shows the change of each signal at the time of abnormality detection of the power converter concerning a 6th embodiment of the present invention. It is a block diagram which shows the structure of the power converter device which concerns on 7th Embodiment of this invention, and its peripheral device.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, a power conversion device mounted on a vehicle will be described as an example.

[Description of First Embodiment]
FIG. 1 is a block diagram illustrating a configuration of a power conversion device according to the first embodiment of the present invention and peripheral devices thereof. The power conversion device according to the first embodiment includes a relay circuit 12, an inverter device 13, and a vehicle control circuit 15 that outputs a drive command to the inverter device 13 and the relay circuit 12. A DC power source 11 and a motor 14 (load) are connected as peripheral devices. The DC power source 11 is, for example, a high-power battery mounted on a vehicle, and the motor 14 is a motor used for driving an electric vehicle.

  The relay circuit 12 includes relays 31, 32, and 33. The relay 31 includes a relay coil 31 c and a relay contact 31 r, and the relay contact 31 r is connected to the plus side terminal of the DC power supply 11. The relay 32 includes a relay coil 32c and a relay contact 32r. The relay contact 32r is connected to the negative terminal of the DC power supply 11, and a resistor R101 is connected in series. The relay 33 includes a relay coil 33 c and a relay contact 33 r, and the relay contact 33 r is connected to the negative terminal of the DC power supply 11. Then, at the start of driving of the inverter device 13, the relay contacts 31r and 32r are turned on and current is passed through the resistor R101 to suppress overcurrent, and then the relay contact 32r is turned off and the relay contacts 31r and 33r are turned on. Switch as follows. Further, when the ignition is turned off or an abnormality such as a collision is detected, all the relay contacts 31r, 32r, 33r are opened, and the power supply from the DC power supply 11 is stopped.

  The inverter device 13 includes a smoothing capacitor C1 that smoothes the DC power supplied from the DC power supply 11, a semiconductor switch group that includes six semiconductor switches Tr1 to Tr6, a gate drive circuit 21, and a main control circuit 22. ing. Then, the DC voltage output from the DC power supply 11 is converted into a three-phase AC voltage, and the AC voltage is supplied to the motor 14. In the present embodiment, an IGBT (insulated gate bipolar transistor) will be described as an example of the semiconductor switch. The semiconductor switch used in the present invention is not limited to the IGBT.

  The semiconductor switches Tr1 and Tr2 are connected in series, the semiconductor switch Tr1 is a U-phase upper arm, and the semiconductor switch Tr2 is a U-phase lower arm, forming a U-phase half-bridge circuit. Each semiconductor switch Tr1, Tr2 is provided with diodes D1, D2.

  The semiconductor switches Tr3 and Tr4 are connected in series, the semiconductor switch Tr3 is a V-phase upper arm, and the semiconductor switch Tr4 is a V-phase lower arm, forming a V-phase half-bridge circuit. Each semiconductor switch Tr3, Tr4 is provided with diodes D3, D4. The semiconductor switches Tr5 and Tr6 are connected in series, the semiconductor switch Tr5 is a W-phase upper arm, and the semiconductor switch Tr6 is a W-phase lower arm, forming a W-phase half-bridge circuit. Further, diodes D5 and D6 are provided in the semiconductor switches Tr5 and Tr6, respectively. That is, a plurality of series connection circuits of a plurality of semiconductor switches are provided.

  Further, a discharge resistor Rd (resistance for power consumption) is provided in parallel with the smoothing capacitor C1. The discharging resistor is a resistor for gradually discharging the electric power stored in the smoothing capacitor C1 when the inverter device 13 does not operate for a long time while the smoothing capacitor C1 is charged. It is mounted on the inverter device as standard.

  The gate drive circuit 21 supplies a drive signal to the gates of the semiconductor switches Tr1 to Tr6 to control on / off of the semiconductor switches Tr1 to Tr6.

  The main control circuit 22 generally controls the inverter device 13. In particular, the rotational speed data of the motor 14 is acquired from the rotational speed sensor 51, and a drive command is output to the gate drive circuit 21 so that the motor 14 is driven at a desired rotational speed. Further, when a discharge mode signal (switching signal to the second turn-on time) is given from the vehicle control circuit 15, all the semiconductor switches Tr1 to Tr6 are turned on, and the electric power stored in the smoothing capacitor C1 is consumed. A discharge process is performed.

  The vehicle control circuit 15 is a circuit included in, for example, an ECU (electronic control unit) mounted on the vehicle, and outputs a signal that instructs the relay circuit 12 to open and connect. Specifically, when the ignition of the vehicle is turned on, the relay contacts 31r and 32r are turned on, the contact 32r is turned off, the contact 33r is turned on, and the voltage output from the DC power supply 11 is converted into the inverter device. 13 is controlled. Further, when the ignition is turned off, or when the inverter device 13 is stopped due to the occurrence of an accident, a control to turn off the relays 31 to 33 is performed by outputting an open command signal to the relay circuit 12. Furthermore, voltage data detected by voltage sensors (not shown) connected to both ends of the smoothing capacitor C1 is output to the main control circuit 22, and when the relays 31 to 33 are turned off or a collision occurs. If so, a discharge mode signal is output to the main control circuit 22.

  The gate drive circuit 21, the main control circuit 22, and the vehicle control circuit 15 have a function as a control unit that switches on and off the semiconductor switches Tr1 to Tr6 included in the semiconductor switch group including the semiconductor switches Tr1 to Tr6. Yes.

  The vehicle control circuit 15 also has a function as a stop detection unit that detects when the relay circuit 12 is opened due to the ignition being turned off or the occurrence of an accident and the supply of power is stopped. . Further, the vehicle control circuit 15 performs a process of discharging the electric power accumulated in the smoothing capacitor C1 when the supply of DC power from the DC power supply 11 to the smoothing capacitor C1 is detected by the stop detection unit. It has.

  The gate drive circuit 21, the main control circuit 22, and the vehicle control circuit 15 can be configured as an integrated computer including a central processing unit (CPU) and storage means such as a RAM, a ROM, and a hard disk. .

  2 is a circuit diagram showing a part of the configuration of the gate drive circuit 21 shown in FIG. 1, FIG. 2 (a) shows the circuit configuration, and FIG. 2 (b) shows the flow of current. The gate drive circuit 21 performs control to output drive signals to the gates of the semiconductor switches Tr1 to Tr6. FIG. 2 shows a control circuit for the semiconductor switch Tr6 (W-phase lower arm) among the six semiconductor switches Tr1 to Tr6. That is, the circuit shown in FIG. 2 is provided for each of the semiconductor switches Tr1 to Tr6. Note that the gate drive IC (31) can be shared between at least two of the semiconductor switches Tr1 to Tr6 depending on the function.

  As shown in FIG. 2A, the gate drive circuit 21 includes a gate drive IC (31), gate charge capacitors C21 and C22, a push-pull circuit 36, and a gate resistor R11 (control terminal resistor). Yes.

  The gate drive IC (31) includes a VCC terminal and a VEE terminal, and voltages output from the power supply terminals Vout + and Vout− of the insulated power supply 35 (power supply unit) are supplied to these terminals, respectively. The gate drive IC (31) includes an output terminal “OUT” and a ground terminal “GND”, and the output terminal “OUT” is a control input (transistor element) of each transistor Q1, Q2 (semiconductor element) constituting the push-pull circuit 36. For example, it is connected to the base of a bipolar transistor. That is, the electric wire connected to the “OUT” terminal is branched into two systems, one branch line is connected to the base of the transistor Q1, and the other branch line is connected to the base of the transistor Q2. The ground terminal “GND” is connected to a connection point between the two gate charge capacitors C21 and C22, and is further connected to one terminal (for example, an emitter of the IGBT) of the semiconductor switch Tr6.

  The gate charge capacitors C21 and C22 are capacitors that accumulate a voltage supplied from the outside, that is, power supplied from the insulated power supply 35, as power for supplying a current to the gate (control terminal) of the semiconductor switch Tr6. .

  The push-pull circuit 36 includes a series connection circuit of transistors Q1 and Q2 and an electronic switch Q11, and switches connection and release between the gate charge capacitors C21 and C22 and the gate of the semiconductor switch Tr6. Therefore, the gate charge capacitors C21 and C22 and the push-pull circuit 36 have a function as a buffer circuit that accumulates the power supplied from the insulated power supply 35 and generates the power supplied to the control terminal (the gate of Tr6). Yes.

  The push-pull circuit 36 is connected in series with a circuit opening electronic switch Q11. The electronic switch Q11 is a normally-on type MOSFET (normally-on type switch), and a photocoupler PC1 for switching the electronic switch Q11 on and off is provided at the gate of the electronic switch Q11. The photocoupler PC1 is composed of, for example, a phototransistor and a light emitting diode. When a discharge mode signal (described later) is output from the main control circuit 22 shown in FIG. 1, the light emitting diode emits light and the phototransistor is turned on. Then, the electronic switch Q11 is opened. That is, the electronic switch Q11 has a function as a buffer invalidation circuit that invalidates the function of the buffer circuit by opening the push-pull circuit 36 (cutting off the current).

  Next, the operation of the inverter device 13 according to the first embodiment configured as described above will be described with reference to the flowcharts shown in FIGS. 3 and 4 and the timing charts shown in FIGS. FIG. 3 shows a processing procedure when an abnormality occurs in the vehicle, and FIG. 4 shows a processing procedure after the abnormality is solved. 5A shows an abnormality detection signal (for example, a signal indicating a vehicle collision) detected by the vehicle control circuit 15 (see FIG. 1), FIG. 5B shows the operation of the relay circuit 12, c) shows the change of the discharge mode signal output from the main control circuit 22, (d) shows the timing of the discharge instruction of the smoothing capacitor C1 by the gate drive circuit 21, and (e) shows each semiconductor by the gate drive circuit 21. The timing of all the gate-off signals of the switches Tr1 to Tr6 is shown, and (f) shows the change in the voltage between the terminals of the smoothing capacitor C1.

  First, in step S11 of FIG. 3, for example, when a vehicle collides and an abnormality of the vehicle is detected by the vehicle control circuit 15, the vehicle control circuit 15 displays the time as shown in FIG. An abnormality detection signal is detected at t1.

  In step S12, the vehicle control circuit 15 detects each of the relays 31, 32, 32 provided in the relay circuit 12 at time t2, which is slightly delayed from time t1, as shown in FIG. The 33 relay contacts 31r, 32r, 33r are opened. Therefore, since the space between the DC power supply 11 and the inverter device 13 is electrically opened, the supply of the power output from the DC power supply 11 to the smoothing capacitor C1 is blocked. Further, the vehicle control circuit 15 outputs a discharge start command to the main control circuit 22 when the relay contacts 31r to 33r are opened.

  In step S13, the main control circuit 22 turns on the discharge mode at time t2 when the relays 31 to 33 are opened as shown in FIG. That is, a discharge mode signal is output to the gate drive circuit 21. By outputting the discharge mode signal, the photocoupler PC1 shown in FIG. 2 is turned on, and accordingly, the electronic switch Q11 is turned off and the push-pull circuit 36 is opened. That is, the buffer circuit is invalidated.

  Further, in step S14, the main control circuit 22 outputs a discharge instruction signal to the gate drive circuit 21 at time t3, which is delayed by time T1 from time t2, as shown in FIG. 5 (d). By outputting the discharge instruction signal, in step S15, all the semiconductor switches, that is, the semiconductor switches Tr1, Tr3, Tr5 of the upper arm and the semiconductor switches Tr2, Tr4, Tr6 of the lower arm are slow ( It switches from off to on at a second turn-on time (to be described later). That is, since the current flowing through the gate of the semiconductor switch Tr6 shown in FIG. 2A is suppressed, the current increases and flows between the collector and emitter of the semiconductor switch Tr6 at a low speed. The same applies to the other semiconductor switches Tr1 to Tr5. Details of this operation will be described later.

  As the current flows through each of the semiconductor switches Tr1 to Tr6, the electric power stored in the smoothing capacitor C1 is gradually consumed. Therefore, as shown in FIG. Gradually decreases from t3.

  The vehicle control circuit 15 monitors the voltage between the terminals of the smoothing capacitor C1 with a voltage sensor (not shown), and when the voltage between the terminals drops to the threshold voltage Vth in step S16 of FIG. 3 (step S16). In step S17, the main control circuit 22 cancels the output of the discharge instruction signal. Specifically, as shown in FIG. 5 (f), the voltage across the terminals of the smoothing capacitor C1 falls below the threshold voltage Vth at time t4. Therefore, at time t4, as shown in FIG. Release the command signal output. Thereby, as shown in FIG.5 (e), all the semiconductor switches Tr1-Tr6 are turned off.

  In the flowchart shown in FIG. 3, when an abnormality is detected in the vehicle, the relay contacts 31r to 33r are opened and the smoothing capacitor C1 is discharged. However, the ignition of the vehicle is turned off. The same operation is performed even in the case where That is, when the ignition is turned off, the relay contacts 31r to 33r are opened. In this case, the smoothing capacitor C1 is discharged in the same procedure as described above.

  Next, processing when the abnormality of the vehicle is canceled will be described with reference to a flowchart shown in FIG. 4 and a timing chart shown in FIG. 6A shows an abnormality detection signal detected by the vehicle control circuit 15 (see FIG. 1), FIG. 6B shows the operation of the relay circuit 12, and FIG. 6C is output from the main control circuit 22. (D) shows execution (on) and stop (off) of PWM control by each semiconductor switch Tr1 to Tr6, and (e) shows each semiconductor switch Tr1 to Tr6 by the gate drive circuit 21. (F) shows the change in the voltage between the terminals of the smoothing capacitor C1.

  When the abnormality that has occurred in the vehicle is canceled in step S31 of FIG. 4, as shown in FIG. 6A, the abnormality detection signal detected by the vehicle control circuit 15 is turned off at time t11. .

  In step S32, the vehicle control circuit 15 cancels the abnormality detection and stops outputting the discharge instruction signal.

  In step S33, as shown in FIG. 6B, the vehicle control circuit 15 turns on (closes) the relays 31 to 33 provided in the relay circuit 12 at a time t12 slightly delayed from the time t11. . Specifically, first, the relay contacts 31r and 32r of the relays 31 and 32 are turned on, and then the relay contact 33r of the relay 33 is turned on, whereby the DC power output from the DC power supply 11 is supplied to the inverter device 13. Supply. That is, the vehicle control circuit 15 (control unit) discharges the electric power stored in the smoothing capacitor C1 when the relay circuit 12 is switched from connection to open, and then the voltage of the smoothing capacitor C1 is preset. After the threshold voltage Vth is lowered, the semiconductor switches Tr1 to Tr6 have a function of setting so that driving for conversion to AC power is possible.

  Further, the main control circuit 22 turns off the discharge mode signal as shown in FIG. As a result, the photocoupler PC1 shown in FIG. 2 is turned off and the normally-on type electronic switch Q11 is turned on, so that the push-pull circuit 36 becomes conductive.

  In step S34, the smoothing capacitor C1 is precharged when the relays 31 and 33 are turned on. Then, as shown in FIG. 6F, the voltage across the terminals of the smoothing capacitor C1 increases.

  Thereafter, in step S35, the gate drive circuit 21 cancels all the gate-offs of the semiconductor switches Tr1 to Tr6 at time t13 when time T2 has elapsed from time t12, as shown in FIG. As shown in (d), PWM control of each of the semiconductor switches Tr1 to Tr6 provided in the inverter device 13 is started, an AC voltage is generated and supplied to the motor 14.

  Thus, when any abnormality occurs in the vehicle, or when the ignition is turned off, the electric power stored in the smoothing capacitor C1 can be discharged at a low speed, and further, the abnormality is avoided. In other words, the inverter 13 can be operated by precharging the smoothing capacitor C1.

  Next, the process shown in step S15 of FIG. 3, that is, the operation of turning on each of the semiconductor switches Tr1 to Tr6 at a slow speed will be described. As shown in FIG. 2A, the gate drive circuit 21 is provided with a push-pull circuit 36 for the semiconductor switch Tr6. The other semiconductor switches Tr1 to Tr5 have the same configuration. The push-pull circuit 36 is provided with a normally-on type electronic switch Q11. When no discharge mode signal is given, that is, when the smoothing capacitor C1 is not discharged, the photocoupler PC1 is turned off. The electronic switch Q11 is kept on.

  In this state, when the semiconductor switch Tr6 is turned on, a drive voltage is output from the “OUT” terminal of the gate drive IC (31). Thereby, the transistor Q1 is turned on. A voltage between the power supply terminals Vout + and Vout− is applied to the gate charge capacitors C21 and C22. The gate charge capacitors C21 and C22 are charged with a predetermined voltage, and the electronic switch Q11 is turned on. Therefore, when the transistor Q1 is turned on, a current flows through a path indicated by an arrow Y1 (solid line) shown in FIG. That is, the current flows from the gate charge capacitor C21 through the collector and emitter of the transistor Q1, further through the gate resistor R11, from the gate to the emitter of the semiconductor switch Tr6, and further toward the gate charge capacitor C21.

  At this time, since the current flowing through the gate of the semiconductor switch Tr6 increases instantaneously, the semiconductor switch Tr6 is switched from off to on at a high speed. That is, when the inverter device 13 is operating to generate an AC voltage, the semiconductor switches Tr1 to Tr6 are switched from OFF to ON in a short time (this is referred to as “first turn-on time”). . That is, when the semiconductor switch Tr6 is turned on at the first turn-on time, the power stored in the gate charge capacitor C21 is supplied to the control terminal (gate) of the semiconductor switch Tr6 via the transistor Q1 (semiconductor element). .

  On the other hand, when the discharge mode signal is output from the main control circuit 22, the photocoupler PC1 is turned on and the electronic switch Q11 is turned off. When the electronic switch Q11 is turned off, no current flows between the collector and emitter of the transistor Q1 even if a drive voltage is output from the “OUT” terminal of the gate drive IC (31). Accordingly, as indicated by an arrow Y2 (broken line) in FIG. 2B, the “OUT” terminal passes through the base of the transistor Q1, the gate resistor R11, the gate and emitter of the semiconductor switch Tr6, and further “GND”. Current flows through the terminals. At this time, the current flowing through the gate of the semiconductor switch Tr6 is a very small current because it flows through the base of the transistor Q1. For this reason, the semiconductor switch Tr6 is switched from off to on at an extremely low speed. In other words, it is switched from off to on in a long time (this is referred to as “second turn-on time”). That is, by opening the electronic switch Q11 (buffer invalidation circuit) and supplying the current flowing through the base (control input) of the transistor Q1 (semiconductor element) to the control terminal (gate) of the semiconductor switch Tr6, the semiconductor switch Tr6 is turned on. Turn on at the second turn-on time.

  Hereinafter, a difference in current flowing through the gate of the semiconductor switch Tr6 when the electronic switch Q11 is turned on and when it is turned off will be described with reference to a graph shown in FIG.

  FIG. 7A shows the change of the collector-emitter voltage VCE over time, and FIG. 7B shows the change of the collector current IC over time. In FIG. 7A, a curve q2 shows a change in the voltage VCE when the semiconductor switch is turned on at the first turn-on time (ton1), and a curve q1 turns on the semiconductor switch at the second turn-on time (ton2). The change of the voltage VCE in the case of In FIG. 7B, a curve q4 shows a change in the collector current IC when the semiconductor switch is turned on at the first turn-on time, and a curve q3 is a case where the semiconductor switch is turned on at the second turn-on time. The change in the collector current Ic of is shown.

  As can be understood from FIGS. 7A and 7B, an increase in current flowing between the collector and emitter of the semiconductor switch Tr6 when the electronic switch Q11 is turned on and when the electronic switch Q11 is turned off. The speed has changed significantly. According to the experiments by the inventors, the second turn-on time (ton2) is a long time exceeding 1 [ms], and the first turn-on time (ton1) is a short time below 1 [μs]. It was confirmed that the difference of 1000 times or more. For this reason, it is understood that the electric power accumulated in the smoothing capacitor C1 can be gradually consumed at a slow speed by passing a current between the collector and the emitter of the semiconductor switch Tr6.

  Here, the second turn-on time is set to consume power faster than the power consumption in the discharging resistor Rd (see FIG. 1) connected in parallel to the smoothing capacitor C1. That is, the power consumption per unit time by turning on the semiconductor switches Tr1 to Tr6 in the second turn-on time is set to be larger than the power consumption consumed per unit time by the discharging resistor Rd. ing.

  FIG. 8 is an explanatory diagram showing the flow of current when all the semiconductor switches Tr1 to Tr6 are turned on in the second turn-on time. As shown in FIG. 8, when the semiconductor switches Tr1 to Tr6 are turned on in the second turn-on time, currents I21, I22, and I23 flow, and the electric power accumulated in the smoothing capacitor C1 can be consumed.

  In this manner, in the inverter device 13 according to the first embodiment, the normally-pull type electronic switch Q11 is provided in the push-pull circuit 36 provided in the gate drive circuit 21. When a discharge mode signal is output from the main control circuit 22, the electronic switch Q11 is turned off and the push-pull circuit 36 is opened. Further, all the semiconductor switches Tr1 to Tr6 are turned on.

  Therefore, the current flowing through the gates of the semiconductor switches Tr1 to Tr6 constituting the inverter device 13 can be remarkably reduced, and the turn-on time of the semiconductor switches Tr1 to Tr6 can be extended. Specifically, the first turn-on time can be changed to the second turn-on time. As a result, since the electric power stored in the smoothing capacitor C1 can be gradually discharged through the semiconductor switches Tr1 to Tr6, the electric power can be consumed without generating a large amount of heat. For this reason, the electric power stored in the smoothing capacitor C1 can be discharged without separately providing a semiconductor element for discharge as in the prior art.

  In addition, when the vehicle control circuit 15 (stop detection unit) detects that the supply of DC power to the smoothing capacitor C1 is stopped, the electric power stored in the smoothing capacitor C1 is discharged, so that it can be used for a long time. The state where electric power is stored in the smoothing capacitor C1 can be reliably prevented.

  Further, the power consumption per unit time by turning on the semiconductor switches Tr1 to Tr6 in the second turn-on time is set to be larger than the power consumption consumed per unit time by the discharging resistor Rd. Therefore, the smoothing capacitor C1 can be discharged at a point earlier than the discharge by the discharge resistor Rd provided as a standard.

  Further, the vehicle control circuit 15 (control unit) discharges the electric power stored in the smoothing capacitor C1 when the relay circuit 12 is switched from connection to open, and then the voltage of the smoothing capacitor C1 is set in advance. After the threshold voltage Vth is lowered, the semiconductor switches Tr1 to Tr6 are set so that they can be driven for conversion to AC power. Therefore, when the discharge of the smoothing capacitor C1 is finished, the inverter device 13 can be operated immediately.

  Further, since both the upper arm and the lower arm, that is, all the semiconductor switches Tr1 to Tr6 are changed from the first turn-on time to the second turn-on time, the electric power stored in the smoothing capacitor C1 is discharged. It is possible to discharge quickly and quickly.

  In the first embodiment described above, the power stored in the smoothing capacitor C1 is discharged by changing all the turn-on times of the semiconductor switches Tr1 to Tr6 from the first turn-on time to the second turn-on time. Showed about.

  The present invention may be configured such that one of the upper arm and lower arm semiconductor switches provided in one half-bridge circuit is changed from the first turn-on time to the second turn-on time. For example, if only the three semiconductor switches Tr2, Tr4, Tr6 serving as the lower arm are provided with the photocoupler PC1 and the electronic switch Q11, only the semiconductor switches Tr2, Tr4, Tr6 serving as the lower arm are the second. The semiconductor switches Tr1, Tr3, Tr5 that are the upper arms are switched from OFF to ON at the first turn-on time.

  That is, it is also possible to adopt a configuration in which one semiconductor switch of the upper arm and the lower arm of the half-bridge circuit is turned on at the first turn-on time and the other semiconductor switch is turned on at the second turn-on time. . Even in this case, in each system, the rate of increase in current can be reduced, so that the electric power stored in the smoothing capacitor C1 can be discharged without significant heat generation. In this case, it is only necessary to change the turn-on time of one of the semiconductor switches, so that the control load can be reduced.

  In the first embodiment described above, the inverter device 13 includes two semiconductor switches connected in series for each of the U phase, the V phase, and the W phase (for example, two semiconductor switches in the case of the U phase). Tr1 and Tr2) are provided, but the present invention can also be applied to an inverter device having a configuration in which three or more semiconductor switches are connected in series. At this time, the effect of this embodiment can be achieved by setting the turn-on time of at least one semiconductor switch as the second turn-on time in one system.

  Furthermore, in the first embodiment, when the semiconductor switches Tr1 to Tr6 are turned on in the second turn-on time, the circuit connected to the gate charge capacitors C21 and C22 is opened, and the gate charge capacitors C21 and C22 (that is, In this case, the current flowing through the transistors Q1 and Q2 can be suppressed, and as a result, the gate currents of the semiconductor switches Tr1 to Tr6 can be reliably reduced.

  In addition, the gate charge capacitors C21 and C22 and the push-pull circuit 36 constitute a buffer circuit, and the electronic switch Q11 (buffer invalidation circuit) is used to invalidate the buffer circuit. Since the time is changed, the turn-on time can be set to the second turn-on time by a simple operation of opening the electronic switch Q11 when the smoothing capacitor C1 is discharged.

  Further, since a normally-on type switch is used as the electronic switch Q11 used as the buffer invalidation circuit, the push-pull circuit 36 can be reliably operated during normal operation, and the inverter device 13 can be stably operated. Can do.

[Description of Second Embodiment]
Next, a second embodiment of the present invention will be described. The power converter according to the second embodiment is different from the first embodiment described above only in the configuration of the gate drive circuit 21. Other configurations are the same as those in the first embodiment. Therefore, only the configuration of the gate driving circuit will be described below. FIG. 9 is a circuit diagram showing a partial configuration of the gate drive circuit 21a used in the inverter device 13a according to the second embodiment. FIG. 9A shows a circuit configuration, and FIG. 9B shows a current flow. Although FIG. 9 shows only a circuit for driving the semiconductor switch Tr6, similar circuits are provided for the other semiconductor switches Tr1 to Tr5.

  The gate drive circuit 21a shown in FIG. 9 differs from the gate drive circuit 21 shown in FIG. 2 in the installation position of the circuit opening electronic switch Q11. That is, in the second embodiment, the electronic switch Q11 is provided between the gate charge capacitor C21 and the power supply terminal Vout +. The electronic switch Q11 is a normally-on type switch. As in the first embodiment, when a discharge mode signal is given from the main control circuit 22, the photocoupler PC1 is turned on and the electronic switch Q11 is opened.

  Hereinafter, the operation of the power conversion device according to the second embodiment will be described. As in the first embodiment, when conversion from DC power to AC power is performed by the inverter device 13a (see FIG. 1), the photocoupler PC1 is turned off. Accordingly, the normally-on type electronic switch Q11 shown in FIG. 9A is turned on, and current flows through the path indicated by the arrow Y1 shown in FIG. 2B by the electric power stored in the gate charge capacitor C21. . For this reason, the current flowing through the gate of the semiconductor switch Tr6 becomes a relatively large current, and the semiconductor switch Tr6 is switched from OFF to ON in the first turn-on time.

  On the other hand, when the discharge mode signal is output from the main control circuit 22, the photocoupler PC1 is turned on and the electronic switch Q11 is opened. When the electronic switch Q11 is opened, the circuit connected to the gate charge capacitor C21 is opened, and the voltage output from the power supply terminal Vout + of the insulated power supply 35 is supplied to the push-pull circuit 36. Therefore, a current flows through the path indicated by the arrow Y3 shown in FIG. Since the output current of the insulated power supply 35 is limited, the current flowing through the gate of the semiconductor switch Tr6 is suppressed, and the current becomes extremely small. For this reason, the semiconductor switch Tr6 is switched from off to on in a second turn-on time longer than the first turn-on time.

  As a result, similarly to the first embodiment, the electric power stored in the smoothing capacitor C1 can be gradually consumed. Thus, in the inverter device 13a according to the second embodiment, when the discharge mode signal is output from the main control circuit 22, the gate charge capacitors C21 and C22 are opened and output from the power supply terminal Vout + of the insulated power supply 35. The supplied voltage is supplied to the gates of the semiconductor switches Tr1 to Tr6 to control the current flowing between the collectors and emitters of the semiconductor switches Tr1 to Tr6. And since the electric current supplied to the gate of each semiconductor switch Tr1-Tr6 reduces remarkably, the turn-on time of each semiconductor switch Tr1-Tr6 can be lengthened. That is, the second turn-on time can be set. As a result, the electric power stored in the smoothing capacitor C1 can be gradually discharged, so that the electric power can be consumed without generating a large amount of heat. For this reason, the electric power stored in the smoothing capacitor C1 can be discharged without separately providing a semiconductor element for discharge as in the prior art.

  Note that it does not matter whether the second turn-on time shown in the first embodiment matches the second turn-on time shown in the second embodiment.

[Description of Third Embodiment]
Next, a third embodiment of the present invention will be described. The power conversion device according to the third embodiment is different from the first embodiment described above only in the configuration of the gate drive circuit. Other configurations are the same as those in the first embodiment. Therefore, only the configuration of the gate driving circuit will be described below. FIG. 10 is a circuit diagram showing a partial configuration of the gate drive circuit 21b provided in the inverter device 13b according to the third embodiment. FIG. 10A shows a circuit configuration, and FIG. 10B shows a current flow. Although FIG. 10 shows only a circuit for driving the semiconductor switch Tr6, similar circuits are provided for the other semiconductor switches Tr1 to Tr5.

  The gate drive circuit 21b shown in FIG. 10 is provided with two gate resistors (control terminal resistors) connected to the gate of the semiconductor switch Tr6. That is, a parallel connection circuit of resistors R21 (first resistor) and R22 (second resistor) is connected to the gate of the semiconductor switch Tr6. The resistor R21 has a very small resistance value with respect to the resistor R22. That is, there is a relationship of resistors R21 << R22. In other words, the second resistor is set to be larger than the first resistor. An electronic switch Q11 (resistance switching circuit) for opening the circuit is provided in series with the resistor R21. The electronic switch Q11 is a normally-on type switch. Further, a photocoupler PC1 is connected to the electronic switch Q11. Further, the resistance switching circuit, that is, the electronic switch Q11 is controlled to be switched off (opened) when a switching signal to the second turn-on time is given.

  Next, the operation of the gate drive circuit 21b will be described. As in the first and second embodiments, when conversion from DC power to AC power is performed by the inverter device 13b (see FIG. 1), the photocoupler PC1 is turned off. Accordingly, the normally-on type electronic switch Q11 shown in FIG. 10A is turned on, and the electric current accumulated in the paths Y4, Y5, and Y7 shown in FIG. Flowing.

  Specifically, the power stored in the gate charge capacitor C21 flows between the collector and emitter of the transistor Q1 and further flows through the resistor R21 to the gate of the semiconductor switch Tr6. In this case, since the current flows through the gate resistor R21 having a small resistance value (since R21 << R22, most of the current flows through the resistor R21), a relatively large current flows through the gate of the semiconductor switch Tr6. The semiconductor switch Tr6 is switched from off to on in the first turn-on time.

  On the other hand, when the discharge mode signal is given from the main control circuit 22, the photocoupler PC1 is turned on and the electronic switch Q11 is turned off. For this reason, the path of the gate resistor R21 is opened. Therefore, the power stored in the gate charge capacitor C21 flows between the collector and emitter of the transistor Q1 and further flows through the gate resistor R22 to the gate of the semiconductor switch Tr6. That is, current flows along arrows Y4, Y6, and Y7 shown in FIG. In this case, since the current flows through the gate resistor R22 having a large resistance value, the current flowing through the gate of the semiconductor switch Tr6 is limited and becomes a very small current. For this reason, the semiconductor switch Tr6 is switched from off to on in the second turn-on time.

  That is, when the electronic switch Q11 is turned on (connected), the semiconductor switches Tr1 to Tr6 are driven for the first turn-on time, and when turned off (opened), the second turn-on is performed. It has a function as a resistance switching circuit driven by time. As a result, similarly to the first and second embodiments, the power accumulated in the smoothing capacitor C1 can be gradually consumed.

  Thus, in the inverter device 13b according to the third embodiment, when the discharge mode signal is output from the main control circuit 22, switching is performed so that the gate resistance of each of the semiconductor switches Tr1 to Tr6 is increased. In other words, when the semiconductor switches Tr1 to Tr6 are turned on at the second turn-on time, the gate resistance (control terminal resistance) is changed to be larger than when the semiconductor switches Tr1 to Tr6 are turned on at the first turn-on time. . Accordingly, the turn-on time of each of the semiconductor switches Tr1 to Tr6 can be lengthened, and the electric power stored in the smoothing capacitor C1 can be gradually discharged, so that the electric power can be consumed without generating a large amount of heat.

  Further, when a discharge mode signal is output from the main control circuit 22, the gate resistance of each of the semiconductor switches Tr1 to Tr6 is switched from the resistance R21 to the resistance R22 having a relatively larger resistance value than the resistance R21. To control. For this reason, the electric power stored in the smoothing capacitor C1 can be discharged without separately providing a semiconductor element for discharge as in the prior art.

  Further, since a normally-on type switch is used as the electronic switch Q11 used as the resistance switching circuit, current can be surely passed through the resistor R21 in normal times, so that the inverter device 13 can be stably operated. it can.

  It does not matter whether the second turn-on time shown in the first and second embodiments matches the second turn-on time shown in the third embodiment.

[Description of Fourth Embodiment]
Next, a fourth embodiment of the present invention will be described. The inverter device 13c according to the fourth embodiment is different from the third embodiment described above only in the configuration of the gate drive circuit. Other configurations are the same as those of the third embodiment. Therefore, only the configuration of the gate driving circuit will be described below. FIG. 11 is a circuit diagram showing a partial configuration of the gate drive circuit 21c according to the fourth embodiment. FIG. 11A shows a circuit configuration, and FIG. 11B shows a current flow. Although FIG. 11 shows only a circuit for driving the semiconductor switch Tr6, similar circuits are provided for the other semiconductor switches Tr1 to Tr5.

  The gate drive circuit 21c shown in FIG. 11 is provided with three gate resistors connected to the gate of the semiconductor switch Tr6. That is, a parallel connection circuit of resistors R21, R22, and R23 is connected to the gate of the semiconductor switch Tr6, and has a relationship of resistors R21, R23 << R22. That is, the resistors R21 and R23 have extremely small resistance values as compared with the resistor R22. Further, a normally-on type electronic switch Q11 is provided in series with the resistor R21. Further, a photocoupler PC1 is connected to the electronic switch Q11. In addition, the resistor R21 is provided with a diode D21 whose forward direction is toward the gate, and the resistor R23 is provided with a diode D23 whose forward direction is opposite to the gate.

  Next, the operation of the gate drive circuit 21c will be described. As in the first to third embodiments, when conversion from DC power to AC power is executed by the inverter device 13c (see FIG. 1), the photocoupler PC1 is turned off. Accordingly, the normally-on type electronic switch Q11 shown in FIG. 11A is turned on, and the electric current accumulated in the paths Y11, Y12, and Y15 shown in FIG. Flowing.

  Specifically, the power stored in the gate charge capacitor C21 flows between the collector and emitter of the transistor Q1, and further flows to the gate of the semiconductor switch Tr6 via the resistor R21 and the diode D21. In this case, since the current flows through the gate resistor R21 having a small resistance value, a relatively large current flows through the gate of the semiconductor switch Tr6. The semiconductor switch Tr6 is turned on from off in the first turn-on time. Switch to

  On the other hand, when the discharge mode signal is given from the main control circuit 22, the photocoupler PC1 is turned on and the electronic switch Q11 is turned off. For this reason, the path of the gate resistor R21 is opened. Accordingly, the power stored in the gate charge capacitor C21 flows between the collector and emitter of the transistor Q1 and further flows through the resistor R22 to the gate of the semiconductor switch Tr6. That is, current flows along arrows Y11, Y13, and Y15 shown in FIG. In this case, since the current flows through the gate resistor R22 having a large resistance value, the current flowing through the gate of the semiconductor switch Tr6 is extremely small. For this reason, the semiconductor switch Tr6 is switched from off to on in the second turn-on time.

  As a result, the electric power stored in the smoothing capacitor C1 can be gradually consumed. Further, when the semiconductor switch Tr6 is switched from on to off, as shown by an arrow Y14 in FIG. 11B, a current flows through the resistor R23, so that the time is substantially the same as the first turn-on time. Can be switched from on to off.

  Thus, in the inverter device 13c according to the fourth embodiment, when the discharge mode signal is output from the main control circuit 22, the gate resistance of each of the semiconductor switches Tr1 to Tr6 is switched from the resistor R21 to the resistor R22. To control. As a result, the turn-on time of each of the semiconductor switches Tr1 to Tr6 can be extended. Specifically, the second turn-on time may be relatively longer than the first turn-on time.

  For this reason, since the electric power stored in the smoothing capacitor C1 can be discharged gradually, the electric power can be consumed without causing a large amount of heat generation. Therefore, the electric power stored in the smoothing capacitor C1 can be discharged without separately providing a semiconductor element for discharge as in the prior art. Further, when each of the semiconductor switches Tr1 to Tr6 is switched from on to off, since a current flows through the resistor R23 and the diode D23, the switching can be performed in a short time.

  Note that it does not matter whether the second turn-on time shown in the first to third embodiments matches the second turn-on time shown in the fourth embodiment.

[Description of Fifth Embodiment]
Next, a fifth embodiment of the present invention will be described. The inverter device 13d according to the fifth embodiment (see FIG. 1) has the same configuration as that of the first embodiment described above, and the voltage output from the insulated power source 35 shown in FIG. 2 is controlled. Is different. In the fifth embodiment, when all the semiconductor switches Tr1 to Tr6 are turned on and the electric power stored in the smoothing capacitor C1 is discharged, the voltage output from the power supply terminal Vout + of the insulated power supply 35 is controlled to be reduced.

  Specifically, when the semiconductor switch group (semiconductor switches Tr1 to Tr6) converts DC power to AC power, the voltage output from the power supply terminal Vout + is set as the first output voltage and stored in the smoothing capacitor C1. When discharging electric power, this voltage is set as a second output voltage lower than the first output voltage. Further, the second output voltage is set higher than the minimum drive voltage of each of the semiconductor switches Tr1 to Tr6.

  Since the device configuration is the same as that of the first embodiment, the operation of the inverter device 13d according to the fifth embodiment will be described below with reference to the circuit diagram shown in FIG. 2 and the timing chart shown in FIG. explain. 12A shows an abnormality detection signal detected by the vehicle control circuit 15 (see FIG. 1), FIG. 12B shows the operation of the relay circuit 12, and FIG. 12C shows the discharge output from the main control circuit 22. (D) shows the timing of discharge instruction of the smoothing capacitor C1 by the gate drive circuit 21, and (e) shows the timing of all gate-off signals of the semiconductor switches Tr1 to Tr6 by the gate drive circuit 21. (F) shows the change in the voltage output from the power supply terminal Vout + of the insulated power supply 35.

  The operations according to the characteristic diagrams shown in FIGS. 12A to 12E are the same as those described with reference to FIGS. In the inverter device 13d according to the fifth embodiment, at the time t3 when the discharge instruction is output, the voltage output from the power supply terminal Vout + of the insulated power supply 35 is controlled relative to the normal time by the control of the main control circuit 22. Reduce.

  As a result, the voltage output from the “OUT” terminal of the gate drive IC (31) shown in FIG. 2 decreases, and accordingly, the current flowing through the base of the transistor Q1 decreases. As a result, the current supplied to the gates of the semiconductor switches Tr1 to TR6 can be further reduced. Specifically, since the current indicated by the arrow Y2 in FIG. 2B can be reduced as compared with the case of the first embodiment, when the electric power stored in the smoothing capacitor C1 is discharged, the second The turn-on time can be further increased. As a result, it is possible to discharge the electric power stored in the smoothing capacitor C1 without causing significant heat generation.

  In the fifth embodiment, the example of reducing the voltage at the power supply terminal Vout + in the inverter device shown in the first embodiment has been described. However, the second embodiment (gate charge capacitor C21, The present invention can also be applied to an example in which an electronic switch Q11 is provided in series with C22.

[Explanation of Sixth Embodiment]
Next, a sixth embodiment of the present invention will be described. The inverter device according to the sixth embodiment is different from the inverter device shown in the first to fifth embodiments in the configuration of the relay circuit 12. That is, in the inverter device according to the sixth embodiment, as shown in FIG. 13, a semiconductor relay circuit 12e (relay circuit) is provided as a relay circuit provided between the DC power supply 11 and the smoothing capacitor C1.

  The semiconductor relay circuit 12e includes semiconductor switches 41, 42, and 43. The semiconductor switch 41 is connected to the plus side terminal of the DC power supply 11. The semiconductor switch 42 is connected to the negative terminal of the DC power supply 11, and a resistor R101 is connected in series. The semiconductor switch 43 is connected to the negative terminal of the DC power supply 11. At the start of driving of the inverter device 13, the semiconductor switches 41 and 42 are turned on and current is passed through the resistor R101 to suppress overcurrent, and then the semiconductor switch 42 is turned off and the semiconductor switch 43 is turned on. Switch.

  In the sixth embodiment, the gate drive circuit 21 outputs a discharge instruction signal to each of the semiconductor switches Tr1 to Tr6 in synchronization with the opening command signal of the semiconductor relay circuit 12e output from the vehicle control circuit 15. That is, the open command signal of the semiconductor relay circuit 12e is used as a switching signal from the first turn-on time to the second turn-on time.

  The operation of the sixth embodiment will be described below with reference to the timing chart shown in FIG. 14A shows an abnormality detection signal detected by the vehicle control circuit 15, FIG. 14B shows the operation of the semiconductor relay circuit 12e, and FIG. 14C shows a change in the discharge mode signal output from the main control circuit 22. (D) shows the timing of the discharge instruction of the smoothing capacitor C1 by the gate drive circuit 21, (e) shows the timing of all gate-off signals of the semiconductor switches Tr1 to Tr6 by the gate drive circuit 21, and (f) Indicates changes in the voltage across the terminals of the smoothing capacitor C1.

  Then, when an abnormality is detected in the vehicle at time t1 shown in FIG. 14, the semiconductor relay circuit 12e is turned on at time t2 slightly delayed. At the same time, a discharge mode signal is output, and a discharge instruction signal is output to each of the semiconductor switches Tr1 to Tr6. That is, in the first embodiment, since a mechanical relay circuit having a relay coil and a relay contact is used, the relay contact is actually turned on from the relay circuit ON command as shown in the flowchart of FIG. A time difference occurred. In contrast, in the sixth embodiment, since the semiconductor relay circuit 12e is used, the smoothing capacitor C1 can be discharged by turning on all the semiconductor switches Tr1 to Tr6 almost simultaneously with the relay opening instruction. That is, as shown by reference numeral P1 in FIG. 14, the timing of the relay contact ON, the discharge mode ON, and the discharge instruction can be matched, so that the smoothing capacitor C1 is earlier as shown in FIG. 14 (f). It is possible to reduce the inter-terminal voltage to the threshold voltage Vth.

  Thus, in the power converter device according to the sixth embodiment, since the semiconductor relay circuit 12e is used as a relay circuit for switching between connection and release between the DC power supply 11 and the inverter device 13, the relay The time from when the contact is turned on to when the discharge is started can be shortened. As a result, the discharge of the smoothing capacitor C1 can be started at an earlier time point, and the electric power accumulated in the smoothing capacitor C1 can be discharged in a shorter time.

  Further, the output of the discharge mode signal and the output of the discharge instruction can be set using the relay contact opening signal. Specifically, as shown by the symbol P in FIG. 14, since the three signals are executed at the same timing, the control burden can be reduced.

[Description of Seventh Embodiment]
FIG. 15 is a circuit diagram showing a configuration of a power conversion device according to the seventh embodiment. The seventh embodiment is different from FIG. 1 described above in that a fuse F1 is provided between the relay circuit 12 and the inverter device 13. When the fusing detection signal of the fuse F1 is detected, the vehicle control circuit 15 shifts to discharge of the smoothing capacitor C1 as a trigger. By doing so, even when the inverter device 13 is stopped while the relay circuit 12 is conductive, the electric power stored in the smoothing capacitor C1 can be discharged.

  As mentioned above, although the power converter device and the control method of the power converter device of the present invention have been described based on the illustrated embodiment, the present invention is not limited to this, and the configuration of each unit is an arbitrary function having the same function. It can be replaced with that of the configuration.

  For example, in each of the above-described embodiments, the example in which the electronic switch Q11 is switched on and off using the photocoupler PC1 has been described. However, the present invention is not limited to this, and has insulation properties such as an insulation relay. A relay can be used.

11 DC power supply 12 Relay circuit 12e Semiconductor relay circuit 13, 13a, 13b, 13c, 13d Inverter device 14 Motor 15 Vehicle control circuit 21, 21a, 21b, 21c Gate drive circuit 22 Main control circuit 31, 32, 33 Relay 31c, 32b , 33c Relay coil 31r, 32r, 33r Relay contact 35 Insulated power supply 36 Push-pull circuit 41-43 Semiconductor switch C1 Smoothing capacitor C21, C22 Gate charge capacitor F1 Fuse Q11 Electronic switch

Claims (16)

In a power converter that converts DC power supplied from a DC power source into AC power,
A smoothing capacitor for smoothing the DC power;
A semiconductor switch group including a plurality of systems of series connection circuits of a plurality of semiconductor switches, and
A control unit that switches on and off each semiconductor switch included in the semiconductor switch group, and
The controller is
When converting the DC power to AC power, the turn-on time of each semiconductor switch is set as the first turn-on time, and when discharging the power stored in the smoothing capacitor, the series connection circuit of each system is connected. A power conversion device, wherein a turn-on time of at least one semiconductor switch included is changed to a second turn-on time longer than the first turn-on time. The controller is
A stop detection unit for detecting that the supply of the DC power to the smoothing capacitor is stopped;
2. The electric power according to claim 1, wherein the control unit discharges the electric power stored in the smoothing capacitor when the stop detection unit detects that the supply of the DC power is stopped. 3. Conversion device. A power consumption resistor is provided in parallel to the smoothing capacitor, and the power consumption per unit time due to turning on the semiconductor switch in the second turn-on time is the unit time of the power consumption resistor. The power conversion device according to claim 1, wherein the power conversion device is larger than a power consumption consumed per hit. Provided between the DC power supply and the smoothing capacitor, further comprising a relay circuit for switching between connection and release of the DC power supply and the smoothing capacitor;
When the relay circuit is switched from connection to open, the control unit discharges the electric power stored in the smoothing capacitor, and then the voltage of the smoothing capacitor drops to a preset threshold voltage, It sets so that the drive for conversion to alternating current power by each semiconductor switch is attained. The power converter device of any one of Claims 1-3 characterized by these. The series connection circuit of each system includes a half bridge circuit composed of two semiconductor switches constituting the upper arm and the lower arm, and is provided in the series connection circuit of all systems when discharging the smoothing capacitor. 5. The power conversion device according to claim 1, wherein the semiconductor switches of both the upper arm and the lower arm of a half-bridge circuit are turned on in the second turn-on time. . The series connection circuit of each system includes a half bridge circuit composed of two semiconductor switches constituting the upper arm and the lower arm, and is provided in the series connection circuit of all systems when discharging the smoothing capacitor. One semiconductor switch of the upper arm and the lower arm of the half bridge circuit is turned on at the first turn-on time, and the other semiconductor switch is turned on at the second turn-on time. The power converter device of any one of Claims 1-4. The control unit includes a gate drive circuit that outputs a drive signal supplied to a control terminal of each semiconductor switch,
The gate driving circuit includes:
A buffer circuit for accumulating power supplied from the outside and generating power supplied to the control terminal;
When the semiconductor switch is turned on at the first turn-on time, power stored in the buffer circuit is supplied to the control terminal,
The power converter according to claim 1, wherein when the semiconductor switch is turned on at the second turn-on time, the function of the buffer circuit is invalidated. The buffer circuit is
A gate charge capacitor for storing power supplied from the outside;
A semiconductor element that switches between supply and stop of the power stored in the gate charge capacitor to the control terminal; and
A buffer invalidation circuit that cuts off a current flowing from the gate charge capacitor to the semiconductor element, and
When the semiconductor switch is turned on at the first turn-on time, the power stored in the gate charge capacitor is supplied to the control terminal of the semiconductor switch via the semiconductor element,
When the semiconductor switch is turned on at the second turn-on time, the buffer invalidation circuit is opened, and a current flowing through a control input of the semiconductor element is supplied to a control terminal of the semiconductor switch. The power conversion device according to claim 7.   9. The power conversion device according to claim 8, wherein the buffer invalidation circuit includes a normally-on type switch, and is switched off when a switching signal to the second turn-on time is given. . Provided between the DC power supply and the smoothing capacitor, further comprising a relay circuit for switching between connection and release of the DC power supply and the smoothing capacitor;
The power conversion device according to claim 9, wherein the switching signal to the second turn-on time is an open command signal for the relay circuit. The control unit includes a gate drive circuit that outputs a drive signal supplied to a control terminal of each semiconductor switch,
The gate driving circuit includes:
A buffer circuit that accumulates power supplied from a power supply unit and generates power to be supplied to the control terminal, and a control terminal resistor provided between the buffer circuit and the control terminal,
The control terminal resistance is changed to be larger when the semiconductor switch is turned on at the second turn-on time than when the semiconductor switch is turned on at the first turn-on time. The power conversion device according to any one of 6. The control terminal resistance forms a parallel connection circuit of a first resistance and a second resistance larger than the first resistance,
A resistance switching circuit is mounted in series with the first resistor,
When the semiconductor switch is turned on in the first turn-on time, the resistance switching circuit is connected,
The power conversion device according to claim 11, wherein when the semiconductor switch is turned on in the second turn-on time, the resistance switching circuit is opened.   The power conversion device according to claim 12, wherein the resistance switching circuit includes a normally-on type switch, and is switched off when a switching signal to the second turn-on time is given. Provided between the DC power supply and the smoothing capacitor, further comprising a relay circuit for switching between connection and release of the DC power supply and the smoothing capacitor;
The power conversion device according to claim 13, wherein the switching signal to the second turn-on time is an open command signal for the relay circuit. The power supply unit further outputs power to be supplied to the control terminal of each semiconductor switch,
When the semiconductor switch group converts DC power to AC power, the first output voltage is used. When the power stored in the smoothing capacitor is discharged, the semiconductor switch group is lower than the first output voltage, and The power converter according to any one of claims 1 to 14, wherein the second output voltage is higher than a minimum drive voltage of each of the semiconductor switches. In a control method of a power converter that converts DC power supplied from a DC power source into AC power,
When converting the DC power into AC power, the semiconductor switch group including a plurality of series connected circuits of a plurality of semiconductor switches is set to a first turn-on time for each semiconductor switch. Switch on, off,
When discharging the power stored in the smoothing capacitor for smoothing the DC power, the turn-on time of at least one semiconductor switch included in the series connection circuit of each system is longer than the first turn-on time. A control method for a power converter, wherein each semiconductor switch is turned on with a turn-on time of 2.

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