JP7591698B2 - Power Conversion Equipment - Google Patents

Description

The present disclosure relates to a power conversion device having a smoothing capacitor.

Patent document 1 describes a generator motor drive device. This generator motor drive device has a generator motor, a capacitor, a driver, a booster, and a controller. The controller performs discharge control when an instruction is input. In the discharge control, the controller operates the booster and the driver, and controls the generator motor as a load to discharge the power stored in the capacitor. When the terminal voltage of the capacitor reaches a threshold value, the controller keeps the switching element of the booster on to form a closed circuit including the capacitor. As a result, the power stored in the capacitor is discharged, and the terminal voltage of the capacitor reaches a voltage value close to the zero level.

Patent No. 5529393

In the above generator motor drive device, the charge in the capacitor is discharged by driving the inverter circuit of the booster. Therefore, when discharging the charge in the capacitor, the multiple semiconductor elements that make up the inverter circuit and the load of the generator motor must all be in a normal state. Therefore, if any one of these semiconductor elements or the generator motor becomes abnormal, there is a problem that the charge in the capacitor cannot be discharged.

This disclosure has been made to solve the problems described above, and aims to provide a power conversion device that can more reliably discharge the residual charge in the smoothing capacitor.

The power conversion device according to the present disclosure includes a power conversion circuit having bridge-connected power semiconductor elements and connected to a DC power source via a switch, a smoothing capacitor connected between the power supply line and the ground line of the power conversion circuit, a charge pump circuit having multiple charge pump capacitors, a drive circuit that drives the power semiconductor elements using power generated by the charge pump circuit, a voltage detection circuit that detects the voltage of the smoothing capacitor, and a control circuit, wherein the charge pump circuit is capable of performing an operation of alternately connecting at least one of the multiple charge pump capacitors to the power supply line and the ground line, and the control circuit is configured to cause the charge pump circuit to perform a discharge operation in which the at least one charge pump capacitor is alternately connected to the power supply line and the ground line after the switch is opened, and to stop the discharge operation of the charge pump circuit when the voltage of the smoothing capacitor becomes equal to or lower than a threshold voltage or when the elapsed time since the start of the discharge operation exceeds a threshold time.

According to the present disclosure, residual charge in the smoothing capacitor can be discharged more reliably.

1 is a diagram showing a schematic configuration of a power conversion device according to a first embodiment; 5A to 5C are diagrams illustrating a discharge operation in the power conversion device according to the first embodiment. 4 is a flowchart showing a flow of a discharge process in the power conversion device according to the first embodiment.

Embodiment 1.
A power conversion device according to a first embodiment will be described. Fig. 1 is a diagram showing a schematic configuration of a power conversion device according to the present embodiment. In the present embodiment, a power conversion device 14 used in a mechanically and electrically integrated generator-motor for a vehicle will be described as an example.

As shown in Fig. 1, the power conversion device 14 includes a power conversion circuit 7, a charge pump circuit 8, a drive circuit 6, a control circuit 10, and a voltage detection circuit 11. The power conversion device 14 is configured to operate a generator motor 12. The generator motor 12 is the rotating machine portion of a mechanically and electrically integrated generator motor that serves as an auxiliary device for an automobile.

The power conversion circuit 7 is connected to the first DC power source 1 via the power line 1a and the first switch 3. The first DC power source 1 is provided outside the power conversion device 14. The first switch 3 is provided on the power line 1a. The first switch 3 performs an opening and closing operation based on a command from an electronic control unit (ECU: Electronic Control Unit) 13. When the first switch 3 is in a closed state, DC power is supplied from the first DC power source 1 to the power conversion circuit 7 via the power line 1a. When the first switch 3 is in an open state, the power supply from the first DC power source 1 to the power conversion circuit 7 is cut off.

The power conversion circuit 7 has a plurality of power semiconductor elements 9. The plurality of power semiconductor elements 9 are bridge-connected between the power supply line 1a and the ground line 1b. The power conversion circuit 7 is configured to generate the required output power by the switching operation of each power semiconductor element 9. When driving the motor, the power conversion circuit 7 converts the DC power supplied from the first DC power source 1 into AC. The converted AC power is supplied to the generator motor 12. When generating power, the power conversion circuit 7 rectifies the AC power supplied from the generator motor 12 and converts it into DC.

The drive circuit 6 is configured to drive multiple power semiconductor elements 9 of the power conversion circuit 7 based on commands from the control circuit 10. A drive circuit 6 is provided for each phase of the generator motor 12.

A smoothing capacitor 5 is connected between the power supply line 1a and the ground line 1b. The smoothing capacitor 5 has the function of smoothing the ripple voltage generated during power conversion. For the smoothing capacitor 5, it is preferable to use a capacitor with a low equivalent series resistance (ESR) and a relatively large capacitance. For example, an electrolytic capacitor or the like is used for the smoothing capacitor 5.

The charge pump circuit 8 is configured to generate power for driving the power semiconductor elements 9. The charge pump circuit 8 has a configuration in which a capacitor, a diode, and a switch are combined. In the charge pump circuit 8, the switch is alternately switched between the power supply side and the ground side, thereby raising the lower end voltage and boosting the output voltage. The driving power generated by the charge pump circuit 8 is supplied to each power semiconductor element 9 via the drive circuit 6.

The charge pump circuit 8 has a low-side charge pump capacitor 8b, a high-side charge pump capacitor 8a, a charge pump drive circuit 8c, a switch 8d and a switch 8e.

The switch 8d is provided corresponding to the high-side charge pump capacitor 8a. The switch 8e is provided corresponding to the low-side charge pump capacitor 8b. The operation of each switch 8d, 8e is switched by the charge pump drive circuit 8c.

When the switch 8e is switched to the power supply side, the low-side charge pump capacitor 8b is connected to the power supply line 1c. Power is supplied to the power supply line 1c from the second DC power supply 2 via the control power supply generating circuit 15. A second switch 4 is provided between the second DC power supply 2 and the control power supply generating circuit 15. The second switch 4 performs an opening and closing operation based on a command from the ECU 13. When the second switch 4 is in a closed state, power is supplied from the second DC power supply 2 to the control circuit 10 and the power supply line 1c via the control power supply generating circuit 15. When the second switch 4 is in an open state, the power supply to the control circuit 10 and the power supply line 1c is cut off. When the switch 8e is switched to the ground side, the low-side charge pump capacitor 8b is connected to the ground line 1b.

When the switch 8d is switched to the power supply side, the high-side charge pump capacitor 8a is connected to the power supply line 1a. Power is supplied to the power supply line 1a from the first DC power supply 1. When the switch 8d is switched to the ground side, the high-side charge pump capacitor 8a is connected to the ground line 1b.

In this way, the charge pump circuit 8 can perform an operation of alternately connecting each of the low-side charge pump capacitor 8b and the high-side charge pump capacitor 8a to the power supply line and the ground line. The output voltage is boosted by alternately connecting each of the low-side charge pump capacitor 8b and the high-side charge pump capacitor 8a to the power supply line and the ground line.

On the high side, a voltage is output that is the sum of the output voltage boosted on the low side and the voltage on the power supply line 1a. The output of the high side is supplied to the power semiconductor element 9 of the upper arm via the drive circuit 6 as drive power. The output of the low side is supplied to the power semiconductor element 9 of the lower arm via the drive circuit 6 as drive power.

It is desirable that the low-side charge pump capacitor 8b and the high-side charge pump capacitor 8a used in the charge pump operation can input and output electric charges at high speed. For this reason, it is preferable that the low-side charge pump capacitor 8b and the high-side charge pump capacitor 8a each use a capacitor with low ESR and low equivalent series inductance (ESL). For example, a ceramic capacitor or the like is used for each of the low-side charge pump capacitor 8b and the high-side charge pump capacitor 8a.

In order to mitigate the effects of fluctuations in the second DC power supply 2, it is preferable that power is supplied to each control circuit, including the charge pump circuit 8, via a control power supply generating circuit 15. The control power supply generating circuit 15 is composed of a DC/DC converter, a linear regulator, etc.

The control circuit 10 is configured to control each function of the power conversion device 14. The control circuit 10 mainly operates with power supplied from the second DC power source 2 via the control power generation circuit 15. The control circuit 10 is configured, for example, mainly with a microcomputer IC. The control circuit 10 communicates with a higher-level ECU 13 mounted on the vehicle side. In response to an operation request from the ECU 13, the control circuit 10 executes operations such as determining whether to permit operation of the charge pump circuit 8 and issuing commands to the drive control circuit 6a of the drive circuit 6.

The charge pump circuit 8 and the drive circuit 6 may be functions realized by a single IC such as a driver IC. It is sufficient that a means is provided for enabling and disabling the operation of each function of the charge pump circuit 8 and the drive circuit 6.

The ECU 13 mainly has the role of aggregating and controlling the various sensor information of the vehicle. The ECU 13 has a function of commanding the opening and closing operations of the first switch 3 and the second switch 4. When the vehicle is stopped, it is preferable that the first switch 3 and the second switch 4 are both controlled to the open state in order to ensure safety during vehicle maintenance and to prevent the battery from running out due to dark current. In the communication between the ECU 13 and the control circuit 10, information on the vehicle side status, including the opening and closing status of the first switch 3 and the second switch 4, and information on the status of the power conversion device 14 are exchanged.

Various types of power storage devices such as lead acid batteries, secondary batteries, fuel cells, and capacitors can be applied to each of the first DC power source 1 and the second DC power source 2. The first DC power source 1 and the second DC power source 2 are of the same voltage system. Alternatively, the voltage of the first DC power source 1, which requires relatively large power, is higher than the voltage of the second DC power source 2. If the voltages of the first DC power source 1 and the second DC power source 2 are different, internal insulation may be required. If the grounding systems of the smoothing capacitor 5 and the charge pump circuit 8, which require discharge, are the same, internal insulation can be achieved by various measures. For example, internal insulation can be achieved by using an insulating power source in the control power generation circuit 15, or by performing insulation processing between a low-current system such as the control circuit 10 and a high-current system such as the charge pump circuit 8 and the drive circuit 6.

The voltage detection circuit 11 is configured to detect the voltage of the power supply line 1a of the first DC power supply 1. The voltage detection circuit 11 is one of the sensors. While the control circuit 10 is operating, the voltage detection circuit 11 can monitor the residual voltage of the smoothing capacitor 5.

Figure 2 is a diagram explaining the discharge operation in the power conversion device according to this embodiment. The charge pump circuit 8 in Figure 2 has a connection configuration equivalent to that of the charge pump circuit 8 in Figure 1. In Figure 1, the low-side charge pump capacitor 8b is alternately connected to the power supply line 1c and the ground line 1b by the switch 8e. The power supply line 1c is connected to the second DC power supply 2 via the control power supply generating circuit 15. The high-side charge pump capacitor 8a is alternately connected to the power supply line 1a and the ground line 1b by the switch 8d. The power supply line 1a is connected to the smoothing capacitor 5. Based on this, the charge pump circuit 8 in Figure 2 is represented diagrammatically using a variable DC power supply and a variable capacitor.

The drive circuit 6 has a push-pull circuit 6b and an inverting level shift circuit 6c. The push-pull circuit 6b is configured by connecting complementary transistors in two stages. The push-pull circuit 6b amplifies the current to drive the power semiconductor element 9. In the example shown in FIG. 2, the power semiconductor element 9 is an N-channel MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor). In the push-pull circuit 6b, an NPN-type bipolar transistor is used for the upper transistor, and a PNP-type bipolar transistor is used for the lower transistor.

In the push-pull circuit 6b, the collector of the upper transistor is connected to the output stage of the high-side charge pump capacitor 8a. The collector of the lower transistor is connected to the source terminal of the power semiconductor element 9. The midpoint where the emitters of the upper and lower transistors are connected to each other forms the output stage of the push-pull circuit 6b. The output stage of the push-pull circuit 6b is connected to the gate terminal of the power semiconductor element 9 via a gate resistor.

When a Hi signal is input to the push-pull circuit 6b, the upper NPN transistor becomes conductive, and a push operation applies a gate voltage to the power semiconductor element 9. This causes the power semiconductor element 9 to become conductive. When a Lo signal is input to the push-pull circuit 6b, the lower PNP transistor becomes conductive, and a pull operation causes the gate and source of the power semiconductor element 9 to have the same potential. This causes the power semiconductor element 9 to become cut off.

The level shift circuit 6c has a pull-up resistor 16 and a switching element 17. The pull-up resistor 16 is connected to the output stage of the high-side charge pump capacitor 8a. The switching element 17 is connected in series between the pull-up resistor 16 and the ground line 1b. The output of the level shift circuit 6c is input to the push-pull circuit 6b via a base resistor.

When the switching element 17 is turned on, the push-pull circuit 6b operates in a pull state, and the power semiconductor element 9 is turned off. When the switching element 17 is turned off, the push-pull circuit 6b operates in a push state, and the power semiconductor element 9 is turned on.

Therefore, when the operation of the power conversion circuit 7 is stopped, the switching element 17 is in a conductive state and the pull-up resistor 16 is connected to ground. Therefore, the charge of the high-side charge pump capacitor 8a is consumed via the pull-up resistor 16.

Furthermore, when switch 8d is switched to the power supply side, the consumed charge is supplied to high-side charge pump capacitor 8a from smoothing capacitor 5. Because first switch 3 is open, no charge is supplied to smoothing capacitor 5 from first DC power supply 1. Therefore, smoothing capacitor 5 continues to discharge without being charged. This causes the capacitor voltage of smoothing capacitor 5 to decrease. Thus, in this embodiment, the residual charge in smoothing capacitor 5 is discharged by the discharging operation of charge pump circuit 8.

Here, it is preferable that the voltage detection circuit 11 has a resistor 11a for voltage division, as shown in Figure 2. The resistor 11a is connected in series between the control circuit 10 and the smoothing capacitor 5. As a result, even if the operation stop process of the control circuit 10 is performed after the discharge process is completed, the charge of the smoothing capacitor 5 is consumed via the resistor 11a. Therefore, the residual charge of the smoothing capacitor 5 can be more completely discharged.

In this embodiment, the charge in the smoothing capacitor 5 can be discharged by continuing to operate the charge pump circuit 8 while the power semiconductor element 9 is stopped. Therefore, even if the power conversion circuit 7 or the generator motor 12 is in an abnormal state, the charge in the smoothing capacitor 5 can be discharged. If the power semiconductor element 9 is operated while the power conversion circuit 7 or the generator motor 12 is in an abnormal state, there is a risk of a large current being generated due to a power supply short circuit, etc. In contrast, in this embodiment, discharge can be performed without operating the power conversion circuit 7, so the charge in the smoothing capacitor 5 can be discharged more safely.

Next, the procedure of the discharge process in the power conversion device according to this embodiment will be described. Figure 3 is a flowchart showing the flow of the discharge process in the power conversion device according to this embodiment. The discharge process shown in Figure 3 is executed by the control circuit 10 when the operation of the power conversion device 14 stops.

3, the control circuit 10 determines whether the first switch 3 is open or not based on a notification from the higher-level ECU 13. If the first switch 3 is open, the process from step S102 onward is executed. If the first switch 3 is closed, the process of step S101 is repeated. The control circuit 10 may start the process of step S101 when it receives a notification from the ECU 13.

In step S102, the control circuit 10 outputs a stop signal to the drive control circuit 6a. This causes the drive circuit 6 to stop driving the power conversion circuit 7, and the power conversion circuit 7 stops operating. Instead of the process of step S102, the control circuit 10 may perform a process to confirm that the drive circuit 6 is in a stopped state.

Next, in step S103, the control circuit 10 calculates the threshold time Tth. Details of the processing in step S103 will be described later.

Next, in step S104, the control circuit 10 outputs an operation permission signal to the charge pump circuit 8 to permit operation of the charge pump circuit 8. As a result, in step S105, the discharge operation of the charge pump circuit 8 is executed. The residual charge in the smoothing capacitor 5 is gradually discharged by the discharge operation of the charge pump circuit 8. That is, in this embodiment, the smoothing capacitor 5 can be discharged by utilizing the circuit function used in the normal operation of the power conversion device 14. In this embodiment, since there is no need to provide a separate discharge circuit, the configuration of the power conversion device 14 can be simplified.

Next, in step S106, the control circuit 10 determines whether the elapsed time T from when the discharge operation of the charge pump circuit 8 started exceeds the threshold time Tth. If the elapsed time T exceeds the threshold time Tth, the process of step S107 is executed. If the elapsed time T is equal to or less than the threshold time Tth, the discharge operation of the charge pump circuit 8 continues.

In step S107, the control circuit 10 determines whether the voltage Vcon of the smoothing capacitor 5 is equal to or lower than the threshold voltage Vth. The voltage Vcon is detected by the voltage detection circuit 11. The threshold voltage Vth is set in advance. If the voltage Vcon is equal to or lower than the threshold voltage Vth, the process proceeds to step S108. On the other hand, if the voltage Vcon is greater than the threshold voltage Vth, the process proceeds to step S109.

In step S108, the control circuit 10 outputs an operation stop signal to the charge pump circuit 8 to stop the operation of the charge pump circuit 8. This stops the discharge operation of the charge pump circuit 8.

In step S109, the control circuit 10 determines that the first switch 3 is faulty. The fault of the first switch 3 includes a fault in the control system related to the first switch 3. That is, if the voltage Vcon does not become equal to or lower than the threshold voltage Vth even when the elapsed time T exceeds the threshold time Tth, it is presumed that the first switch 3 is stuck or that the ECU 13 is not able to control the first switch 3 normally. If the control circuit 10 determines that the first switch 3 is faulty, it notifies the ECU 13 of this information, for example. This makes it possible to notify the user of the fault of the first switch 3 by a warning light or the like provided in the vehicle.

In this embodiment, it is desirable to calculate the threshold time Tth, which is a variable value, before allowing the operation of the charge pump circuit 8. The voltage applied to the smoothing capacitor 5 varies depending on the state of the first DC power source 1 and the operation of the power conversion circuit 7. For this reason, the time required for discharging the smoothing capacitor 5 is likely to vary.

Therefore, the control circuit 10 estimates the load current or the load resistance value in advance. The load current is the current consumed in the charge pump circuit 8 and the drive circuit 6 for all phases in the generator motor 12. The load resistance value is the resistance value of the charge pump circuit 8 and the drive circuit 6 for all phases in the generator motor 12. In step S103, the control circuit 10 calculates the threshold time Tth based on the voltage Vcon of the smoothing capacitor 5 immediately before the discharge process is performed, the load current or the load resistance value estimated in advance, and the target value of the voltage Vcon after the discharge process. The target value of the voltage Vcon after the discharge process is, for example, the threshold voltage Vth. This makes it possible to set an appropriate discharge time taking into account the influence of the variation in the voltage Vcon at the start of the discharge process. Therefore, the residual charge of the smoothing capacitor 5 can be discharged more reliably, and the failure of the first switch 3 or the control system related to the first switch 3 can be detected with high accuracy.

In the discharge process shown in FIG. 3, the processes of steps S107 and S109 can be omitted. In this case, when the elapsed time T exceeds the threshold time Tth, the control circuit 10 outputs an operation stop signal to the charge pump circuit 8 regardless of the voltage Vcon. Also, in the discharge process shown in FIG. 3, the process of step S106 can be omitted. In this case, when the voltage Vcon becomes equal to or lower than the threshold voltage Vth, the control circuit 10 outputs an operation stop signal to the charge pump circuit 8 regardless of the elapsed time T. That is, in this embodiment, the control circuit 10 outputs an operation stop signal to the charge pump circuit 8 when the voltage Vcon becomes equal to or lower than the threshold voltage Vth, or when the elapsed time T exceeds the threshold time Tth.

As described above, the power conversion device 14 according to this embodiment includes a power conversion circuit 7, a smoothing capacitor 5, a charge pump circuit 8, a drive circuit 6, a voltage detection circuit 11, and a control circuit 10. The power conversion circuit 7 has a bridge-connected power semiconductor element 9. The power conversion circuit 7 is connected to the first DC power source 1 via the first switch 3. The smoothing capacitor 5 is connected between the power supply line 1a and the ground line 1b of the power conversion circuit 7. The charge pump circuit 8 has a plurality of charge pump capacitors. The drive circuit 6 drives the power semiconductor element 9 using the power generated by the charge pump circuit 8. The voltage detection circuit 11 detects the voltage of the smoothing capacitor 5. The charge pump circuit 8 is capable of performing an operation of alternately connecting at least one high-side charge pump capacitor 8a among the plurality of charge pump capacitors to the power supply line 1a and the ground line 1b.

After the first switch 3 is opened, the control circuit 10 causes the charge pump circuit 8 to execute a discharge operation in which the high-side charge pump capacitor 8a is alternately connected to the power supply line 1a and the ground line 1b. The control circuit 10 is configured to stop the discharge operation of the charge pump circuit 8 when the voltage Vcon of the smoothing capacitor 5 becomes equal to or lower than the threshold voltage Vth, or when the elapsed time T from the start of the discharge operation exceeds the threshold time Tth. Here, the first switch 3 is an example of a switch. The first DC power supply 1 is an example of a DC power supply. The high-side charge pump capacitor 8a is an example of a charge pump capacitor.

According to this configuration, the charge in the smoothing capacitor 5 can be discharged by the discharge operation of the charge pump circuit 8 without operating the power conversion circuit 7. This allows the residual charge in the smoothing capacitor 5 to be more reliably discharged, regardless of the state of the power conversion circuit 7 and the generator motor 12. In addition, since discharge can be performed using the circuit used in the normal operation of the power conversion device 14 without providing a separate dedicated discharge circuit, the configuration of the power conversion device 14 can be simplified.

In the power conversion device 14 according to the present embodiment, the drive circuit 6 has an inverting level shift circuit 6c. The level shift circuit 6c has a switching element 17 and a pull-up resistor 16. The switching element 17 and the pull-up resistor 16 are connected in series between the output stage of the charge pump circuit 8 and the ground line 1b. When the power semiconductor element 9 is in a cut-off state, the switching element 17 is in a conductive state. According to this configuration, when the operation of the power conversion circuit 7 is stopped, the pull-up resistor 16 is connected to ground via the switching element 17 in a conductive state. Therefore, the charge of the high-side charge pump capacitor 8a can be consumed by the pull-up resistor 16.

In the power conversion device 14 according to the present embodiment, the control circuit 10 determines that the first switch 3 is faulty if the voltage Vcon of the smoothing capacitor 5 does not become equal to or lower than the threshold voltage Vth even when the elapsed time T exceeds the threshold time Tth. With this configuration, it is possible to notify the user of the fault in the first switch 3.

In the power conversion device 14 according to the present embodiment, the control circuit 10 calculates the threshold time Tth based on the voltage of the smoothing capacitor 5 before the discharge operation is started, the load current consumed in the charge pump circuit 8 and the drive circuit 6, and the threshold voltage Vth. With this configuration, the threshold time Tth can be appropriately set according to the time required for discharge.

In the power conversion device 14 according to this embodiment, the voltage detection circuit 11 has a resistor 11a. The resistor 11a is connected in series between the control circuit 10 and the smoothing capacitor 5. With this configuration, even if the operation of the control circuit 10 stops after the discharge process is completed, the charge in the smoothing capacitor 5 is consumed via the resistor 11a. Therefore, the residual charge in the smoothing capacitor 5 can be more completely discharged.

In the above embodiment, a power conversion device used in a mechanically and electrically integrated generator-motor for a vehicle is given as an example, but the present disclosure is not limited to this. The present disclosure can be applied to various power conversion devices that require discharge processing of a smoothing capacitor.

It goes without saying that the embodiments of the present disclosure should be considered in all respects as illustrative and not limiting, and that various modifications are possible without departing from the technical spirit of the present disclosure.

1 first DC power supply, 1a power supply line, 1b ground line, 1c power supply line, 2 second DC power supply, 3 first switch, 4 second switch, 5 smoothing capacitor, 6 drive circuit, 6a drive control circuit, 6b push-pull circuit, 6c level shift circuit, 7 power conversion circuit, 8 charge pump circuit, 8a high side charge pump capacitor, 8b low side charge pump capacitor, 8c charge pump drive circuit, 8d switch, 8e switch, 9 power semiconductor element, 10 control circuit, 11 voltage detection circuit, 11a resistor, 12 generator motor, 13 ECU, 14 power conversion device, 15 control power supply generation circuit, 16 pull-up resistor, 17 switching element, T elapsed time, Tth threshold time, Vcon voltage, Vth threshold voltage.

Claims (5)

a power conversion circuit having bridge-connected power semiconductor elements and connected to a DC power source via a switch;
a smoothing capacitor connected between a power supply line and a ground line of the power conversion circuit;
a charge pump circuit having a plurality of charge pump capacitors;
a drive circuit that drives the power semiconductor device by using the power generated by the charge pump circuit;
a voltage detection circuit for detecting a voltage of the smoothing capacitor;
A control circuit;
Equipped with
the charge pump circuit is capable of performing an operation of alternately connecting at least one charge pump capacitor among the plurality of charge pump capacitors to the power supply line and the ground line;
The control circuit includes:
causing the charge pump circuit to perform a discharging operation in which the at least one charge pump capacitor is alternately connected to the power supply line and the ground line after the switch is opened;
A power conversion device configured to stop the discharge operation of the charge pump circuit when the voltage of the smoothing capacitor falls below a threshold voltage or when the elapsed time since the discharge operation began exceeds a threshold time. the drive circuit has an inverting level shift circuit,
the level shift circuit has a switching element and a pull-up resistor connected in series between an output stage of the charge pump circuit and the ground line,
The power conversion device according to claim 1 , wherein the switching element is in a conductive state when the power semiconductor element is in a cutoff state. The power conversion device according to claim 1 or claim 2, wherein the control circuit determines that the switch is faulty if the voltage of the smoothing capacitor does not become equal to or lower than the threshold voltage even when the elapsed time exceeds the threshold time. A power conversion device as described in any one of claims 1 to 3, wherein the control circuit calculates the threshold time based on the voltage of the smoothing capacitor before the discharge operation is started, the load current consumed in the charge pump circuit and the drive circuit, and the threshold voltage. A power conversion device as described in any one of claims 1 to 4, wherein the voltage detection circuit has a resistor connected in series between the control circuit and the smoothing capacitor.

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