JP7309472B2 - POWER CONVERSION DEVICE AND CONTROL METHOD FOR POWER CONVERSION DEVICE - Google Patents

Description

The present invention relates to a power converter and a control method for the power converter.

In conventional power converters, when a voltage higher than a safe voltage is held in a DC voltage smoothing capacitor inside the product when operation is stopped, an operation is required to quickly discharge electric charges inside the product.

For example, in a power converter that discharges using a conventional discharge resistor, in addition to adding a circuit for discharge, a discharge resistor with a large allowable power is required in consideration of an increase in ambient temperature and repeated operation.

As a result, it is necessary to select a large-sized discharge resistor, and there is a problem that the power conversion device becomes large-sized.

Furthermore, for example, in another conventional power converter disclosed in Patent Document 1, a smoothing capacitor is discharged by switching a switch element of a power module for outputting a voltage for driving a three-phase motor that is a load. .

However, Patent Document 1 does not describe that the output voltage output by the power module is controlled to a safe voltage (for example, 0 V) during the discharge operation.

JP 2016-123202

Accordingly, it is an object of the present invention to provide a power converter capable of discharging electric charge accumulated in a DC voltage smoothing capacitor and controlling the output voltage to a safe voltage when the operation is stopped, while achieving miniaturization. aim.

A power conversion device according to an aspect of the present invention includes:
A power conversion device that converts a battery voltage output by a battery into power and outputs an AC output voltage to be supplied to a load,
a smoothing capacitor connected between a first DC voltage terminal to which a DC voltage based on the battery voltage is supplied and a second DC voltage terminal;
a bridge circuit that receives the DC voltage and outputs a converted voltage between a first converted voltage terminal and a second converted voltage terminal by switching operation of a switch element;
a filter that filters the converted voltage output by the bridge circuit and outputs the output voltage;
a control unit for outputting the output voltage based on the converted voltage between a first output voltage terminal and a second output voltage terminal by controlling the bridge circuit;
The control unit
During normal operation of the power converter, the switch elements of the bridge circuit are controlled at a drive frequency within a predetermined range, and the output voltage of a preset target value is applied to the first output voltage terminal and the second output voltage terminal. and the output voltage terminal of
On the other hand, when the operation of the power converter is stopped, the switch element of the bridge circuit is controlled at an output stop frequency higher than the drive frequency within a preset period after the output is stopped, and the smoothing capacitor is A safety voltage lower than the target value is set between the first output voltage terminal and the second output voltage terminal while discharging.

In the power converter,
The control unit
By operating the switch element of the bridge circuit so that the voltage between the first output voltage terminal and the second output voltage terminal becomes the safe voltage, the switch element of the bridge circuit A loss is used to discharge the electric charge of the smoothing capacitor.

In the power converter,
The safety voltage is 0V.

In the power converter,
discharge means connected between said first DC voltage terminal and said second DC voltage terminal;
a control switch element connected in series with the discharge means between the first DC voltage terminal and the second DC voltage terminal and controlled by the control unit;
a detection circuit that detects current flowing through the control switch element,
A circuit including the discharge means and the control switch element is connected in parallel with the smoothing capacitor between the first DC voltage terminal and the second DC voltage terminal.

In the power converter,
The discharge means is a discharge resistor connected in series with the control switch element between the first DC voltage terminal and the second DC voltage terminal.

In the power converter,
The control unit
It is designed to operate by supplying control power,
The control unit
When the control power supply is supplied and is operating, the control switch element is controlled to be turned off, and when the power conversion device is stopped, a discharge operation is performed by a bridge circuit,
On the other hand, when the supply of the control power source to the control unit is interrupted and the control unit stops, the discharge means is adapted to perform discharge.

In the power converter,
further comprising a DC/DC converter that receives the battery voltage and outputs the DC voltage between the first DC voltage terminal and the second DC voltage terminal;
The control unit
It is characterized by controlling the operation of the DC/DC converter.

In the power converter,
The control unit
When the current detected by the detection circuit for detecting the current flowing through the control switch element is out of a preset range while the DC/DC converter is operating, the operation of the DC/DC converter is stopped. It is characterized by a forced stop.

In the power converter,
The control unit
By turning on the control switch element in accordance with an external signal input by a user, a discharge current is caused to flow through the discharge means, thereby discharging the smoothing capacitor.

In the power converter,
The power conversion device is mounted on a vehicle, and the output voltage output from the power conversion device is supplied to a load of the vehicle.

In the power converter,
The control unit
Since the bridge circuit cannot operate when the control power supply is lost, the smoothing capacitor is discharged by turning on the control switch element so that a discharge current flows through the discharge means. .

In the power converter,
The bridge circuit is
It is characterized by being a single-phase full-bridge circuit or a three-phase full-bridge circuit.

A control method for a power conversion device according to an aspect of the present invention includes:
A power conversion device for converting a battery voltage output by a battery into power and outputting an AC output voltage to be supplied to a load, wherein a first DC voltage terminal is supplied with a DC voltage based on the battery voltage. and a smoothing capacitor connected between and a second DC voltage terminal, the DC voltage is input, and the conversion voltage is transferred to the first conversion voltage terminal and the second conversion voltage terminal by the switching operation of the switch element a bridge circuit that outputs between, a filter that filters the converted voltage output by the bridge circuit and outputs the output voltage, and a filter that outputs the output voltage by controlling the bridge circuit to output the output voltage based on the converted voltage A control method for a power conversion device comprising: a control unit for outputting between a first output voltage terminal and a second output voltage terminal,
The control unit
During normal operation of the power converter, the switch elements of the bridge circuit are controlled at a drive frequency within a predetermined range, and the output voltage of a preset target value is applied to the first output voltage terminal and the second output voltage terminal. and the output voltage terminal of
On the other hand, when the operation of the power converter is stopped, the switch element of the bridge circuit is controlled at an output stop frequency higher than the drive frequency within a preset period after the output is stopped, and the smoothing capacitor is A safety voltage lower than the target value is set between the first output voltage terminal and the second output voltage terminal while discharging.

A power conversion device according to an aspect of the present invention is a power conversion device that converts a battery voltage output by a battery into power and outputs an AC output voltage to be supplied to a load. A smoothing capacitor is connected between a first DC voltage terminal to which a voltage is supplied and a second DC voltage terminal. By controlling the bridge circuit that outputs between the voltage terminal and the second converted voltage terminal, the filter that filters the converted voltage output by the bridge circuit and outputs the output voltage, and the bridge circuit, a control unit for outputting the output voltage between the first output voltage terminal and the second output voltage terminal.

During normal operation of the power converter, the control unit controls the switch elements of the bridge circuit at a drive frequency within a predetermined range, and outputs a preset target value to the first output voltage terminal and the second output voltage terminal. and the output voltage terminal of

On the other hand, when the operation of the power converter is stopped, the control unit controls the switch elements of the bridge circuit at an output stop frequency higher than the drive frequency within a preset period after the output is stopped, and discharges the smoothing capacitor. and a safe voltage lower than the target value between the first output voltage terminal and the second output voltage terminal.

As a result, according to the power conversion apparatus of the present invention, it is possible to discharge electric charges accumulated in the DC voltage smoothing capacitor and control the output voltage to a safe voltage when the operation is stopped while miniaturization is achieved.

FIG. 1 is a circuit diagram showing an example of the configuration of a power converter 100 according to an embodiment of the invention. FIG. 2 is a waveform diagram showing an example of the waveform of the converted voltage VY during normal operation of the power converter 100 shown in FIG. FIG. 3 is a waveform diagram showing an example of the waveform of the output voltage VO during normal operation of the power converter 100 shown in FIG. FIG. 4 is a waveform diagram showing an example of the waveform of the converted voltage VY during the discharging operation of the power converter 100 shown in FIG. FIG. 5 is a waveform diagram showing an example of the output voltage VO waveform during the discharge operation of the power converter 100 shown in FIG.

Hereinafter, a power conversion device according to the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing an example of the configuration of a power converter 100 according to an embodiment of the present invention.

Here, the power conversion device 100 shown in FIG. 1 performs power conversion on the battery voltage VB output by the battery B, and outputs an AC output voltage VO to be supplied to the load Load.

This power conversion device 100 is, for example, loaded on a vehicle (not shown). In this case, the battery B is loaded on the vehicle, and the output voltage VO output by the power converter 100 is supplied to the load LOAD of the vehicle.

For example, as shown in FIG. 1, the power converter 100 includes a first battery terminal TB1, a second battery terminal TB2, a DC/DC converter X, a smoothing capacitor CS, a discharge resistor (discharge means ) RD, a detection circuit ID, a control switch element CSW, a first DC voltage terminal TV1, a second DC voltage terminal TV2, a bridge circuit Y, a first conversion voltage terminal TY1, a second It has a conversion voltage terminal TY2, an LC filter (filter) F, a first output voltage terminal TO1 and a second output voltage terminal TO2.

A positive electrode of the battery B is connected to the first battery terminal TB1.

A negative electrode of the battery B is connected to the second battery terminal TB2.

That is, the battery voltage VB of the battery B is applied between the first battery terminal TB1 and the second battery terminal TB2.

The input side of the DC/DC converter X is connected to the first battery terminal TB1 and the second battery terminal TB2.

The output side of the DC/DC converter X is connected to the first DC voltage terminal TV1 and the second DC voltage terminal TV2.

That is, the DC/DC converter X receives the battery voltage VB of the battery B via the first and second battery terminals TB1 and TB2, and connects the first DC voltage terminal TV1 and the second DC voltage terminal TV2. A DC voltage VD is output during the period.

Also, the first DC voltage terminal TV1 is connected to the high voltage side of the output of the DC/DC converter X.

A second DC voltage terminal TV2 is connected to the low voltage side of the output of the DC/DC converter X.

That is, a DC voltage VD based on the battery voltage VB is supplied between the first DC voltage terminal TV1 and the second DC voltage terminal TV2.

A smoothing capacitor CS is also connected between the first DC voltage terminal TV1 and the second DC voltage terminal TV2.

The smoothing capacitor CS is supplied with a DC voltage VD based on the battery voltage VB via a first DC voltage terminal TV1 and a second DC voltage terminal TV2.

Further, the discharge resistor RD, which is the discharge means, is connected in series with the control switch element CSW between the first DC voltage terminal TV1 and the second DC voltage terminal TV2, as shown in FIG. there is In particular, in the example of FIG. 1, the discharge resistor RD has one end connected to the first DC voltage terminal TV1 and the other end connected to one end (drain) of the control switch element CSW.

Further, the control switch element CSW is connected in series with the discharge resistor RD between the first DC voltage terminal TV1 and the second DC voltage terminal TV2, for example, as shown in FIG.

A circuit including a discharge resistor RD and a control switch element CSW is connected in parallel with the smoothing capacitor CS between the first DC voltage terminal TV1 and the second DC voltage terminal TV2.

The control switch element CSW is controlled by the controller CNT.

In particular, in the example of FIG. 1, the control switch element CSW has one end (drain) connected to the other end of the discharge resistor RD and the other end (source) connected to the detection circuit ID.

In the example of FIG. 1, the control switch element CSW is an nMOS transistor whose gate voltage is controlled by the control unit CNT. A body diode is connected between the source and drain of this nMOS transistor as shown in FIG.

Therefore, when there is a predetermined potential difference between the first DC voltage terminal TV1 and the second DC voltage terminal TV2, the control switch element CSW is turned on, thereby causing a discharge current to flow through the discharge resistor RD. becomes.

On the other hand, when the control switch element CSW is turned off, no discharge current flows through the discharge resistor RD.

Further, the detection circuit ID detects, for example, the current flowing through the control switch element CSW (that is, the discharge current flowing through the discharge resistor), as shown in FIG.

In particular, in the example of FIG. 1, the detection circuit ID is connected between the other end (source) of the control switch element CSW and the second DC voltage terminal TV2.

Therefore, when the control switch element CSW is turned on and the detection circuit ID detects a predetermined current, it is determined that a discharge current is flowing through the discharge resistor RD.

Further, as will be described later, the control unit CNT turns off the control switch element CSW when operating normally. Then, for example, when the control unit CNT malfunctions and the control switch element CSW is turned on, a discharge current flows through the discharge resistor RD, and the detection circuit ID detects the current. The operation of the DC/DC converter X may be stopped based on the current detection by the detection circuit ID.

Also, as shown in FIG. 1, for example, the bridge circuit Y receives a DC voltage VD, and converts the converted voltage VY to a first It is designed to output between the converted voltage terminal TY1 and the second converted voltage terminal TY2.

Although this bridge circuit Y is a single-phase full bridge circuit in the example of FIG. 1, it may be a three-phase full bridge circuit if necessary.

For example, as shown in FIG. 1, the bridge circuit Y includes a first switch element SW1, a second switch element SW2, a third switch element SW3, and a fourth switch element SW4.

The first switch element SW1 has one end (drain) connected to the first DC voltage terminal TV1 and the other end (source) connected to the first converted voltage terminal TY1.

The first switch element SW1 is an nMOS transistor whose gate voltage is controlled by the control unit CNT in the example of FIG. A body diode is connected between the source and drain of this nMOS transistor as shown in FIG.

The second switch element SW2 is an nMOS transistor having one end (drain) connected to the first converted voltage terminal TY1 and the other end (source) connected to the second DC voltage terminal TV2.

The second switch element SW2 is an nMOS transistor whose gate voltage is controlled by the control unit CNT in the example of FIG. A body diode is connected between the source and drain of this nMOS transistor as shown in FIG.

The third switch element SW3 is an nMOS transistor having one end (drain) connected to the first DC voltage terminal TV1 and the other end (source) connected to the second converted voltage terminal TY2.

The third switch element SW3 is an nMOS transistor whose gate voltage is controlled by the control unit CNT in the example of FIG. A body diode is connected between the source and drain of this nMOS transistor as shown in FIG.

The fourth switch element SW4 is an nMOS transistor having one end (drain) connected to the second converted voltage terminal TY2 and the other end (source) connected to the second DC voltage terminal TV2.

The fourth switch element SW4 is an nMOS transistor whose gate voltage is controlled by the control unit CNT in the example of FIG. A body diode is connected between the source and drain of this nMOS transistor as shown in FIG.

As described above, the bridge circuit Y having such a configuration receives the DC voltage VD, and converts the converted voltage VY to the first is output between the converted voltage terminal TY1 and the second converted voltage terminal TY2.

The first converted voltage terminal TY1 is connected between the other end of the first switch element SW1 and one end of the second switch element SW2, and is connected to one input of the LC filter F. .

The second converted voltage terminal TY2 is connected between the other end of the third switch element SW3 and one end of the fourth switch element SW4, and is connected to the other input of the LC filter F. .

The converted voltage VY is supplied to the LC filter F from the first converted voltage terminal TY1 and the second converted voltage terminal TY2.

Further, the LC filter F, for example, as shown in FIG. 1, filters the converted voltage VY output by the bridge circuit Y to pass the output voltage VO between the first output voltage terminal TO1 and the second output voltage terminal TO2. It is designed to output between

This LC filter F includes, for example, a first choke coil L1, a second choke coil L2, and an output capacitor CO, as shown in FIG.

The first choke coil L1 has one end connected to the first converted voltage terminal TY1 and the other end connected to the first output voltage terminal TO1, as shown in FIG.

The second choke coil L2 has one end connected to the second converted voltage terminal TY2 and the other end connected to the second output voltage terminal TO2, as shown in FIG.

The second choke coil L2 constitutes a transformer together with the first choke coil L1.

Also, the output capacitor CO is connected between the first output voltage terminal TO1 and the second output voltage terminal TO2, for example, as shown in FIG.

As described above, the LC filter F having such a configuration filters the converted voltage VY output by the bridge circuit Y to transfer the output voltage VO to the first output voltage terminal TO1 and the second output voltage terminal TO2. output between

Note that, instead of the LC filter F shown in FIG. 1, another filter having a similar function may be applied to the power converter 100. FIG.

One end of a load LOAD is connected to the first output voltage terminal TO1.

The other end of the load LOAD is connected to the second output voltage terminal TO2.

The output voltage VO filtered from between the first output voltage terminal TO1 and the second output voltage terminal TO2 is supplied to the load Load.

Here, the control unit CNT controls the bridge circuit Y. As shown in FIG. More specifically, the controller CNT controls the first to fourth switch elements SW1 to SW4.

For example, during normal operation of the power conversion device 100, the control unit CNT controls the first to fourth switch elements SW1 to SW4 of the bridge circuit Y at a drive frequency within a predetermined range to achieve a preset target value. An output voltage VO is output between the first output voltage terminal TO1 and the second output voltage terminal TO2.

In this way, the control unit CNT controls the bridge circuit Y so as to output the output voltage VO based on the converted voltage VY between the first output voltage terminal TO1 and the second output voltage terminal TO2. It has become.

On the other hand, when the operation of the power conversion device 100 is stopped, the control unit CNT controls the first to fourth switch elements SW1 to SW4 of the bridge circuit Y within a preset period (for example, 3 seconds) after the output is stopped. to discharge the smoothing capacitor CS and set the voltage between the first output voltage terminal TO1 and the second output voltage terminal TO2 to a safe voltage lower than the target value. It's like

In particular, the control unit CNT controls the first to fourth switches of the bridge circuit Y so that the voltage between the first output voltage terminal TO1 and the second output voltage terminal TO2 becomes a preset safe voltage. By operating the elements SW1 to SW4, the loss of the first to fourth switch elements SW1 to SW4 of the bridge circuit Y causes the charge of the smoothing capacitor CS to be discharged.

In addition, the safety voltage described above is, for example, 0V.

Here, the control unit CNT is operated by being supplied with control power.

This control unit CNT controls to turn off the control switch element CSW when the control power supply described above is supplied and is operating, and when the power conversion device 100 is stopped, the bridge circuit Y discharges is set to run.

On the other hand, when the supply of control power to the control unit CNT is interrupted and the control unit CNT is stopped, the control switch element CSW is turned on and discharge is performed by the discharge resistor RD. It's becoming

That is, since the control unit CNT cannot operate (control) the bridge circuit Y when the control power supply is lost, the control switch element CSW is turned on so that the discharge current flows through the discharge resistor RD. The smoothing capacitor CS is discharged.

As described above, the control unit CNT cannot operate (control) the bridge circuit Y when the control power supply is lost, so the control unit CNT executes discharge by the discharge resistor RD as a backup operation.

Since the operation of the control unit CNT is a single-shot operation only in an emergency and no repetitive operation occurs, a small resistor with a low rated power can be selected as the discharge resistor RD.

Also, this control unit CNT controls the operation of the DC/DC converter X. As shown in FIG.

When the current detected by the detection circuit ID is out of a preset range while the DC/DC converter X is operating, the control unit CNT forces the DC/DC converter X to operate. It is designed to stop at

Further, as described above, the control unit CNT turns off the control switch element CSW when operating normally. Then, for example, when the control unit CNT malfunctions and the control switch element CSW is turned on, a discharge current flows through the discharge resistor RD, and the detection circuit ID detects the current. The operation of the DC/DC converter X may be stopped based on the current detection by the detection circuit ID.

In addition, the control unit CNT turns on the control switch element CSW in response to an external signal SA input by the user, thereby causing a discharge current to flow through the discharge resistor RD, thereby discharging the smoothing capacitor CS. ing.

Next, an example of a control method for the power conversion device 100 having the configuration as described above will be described.

Here, FIG. 2 is a waveform diagram showing an example of the waveform of the converted voltage VY during normal operation of the power converter 100 shown in FIG. FIG. 3 is a waveform diagram showing an example of the waveform of the output voltage VO during normal operation of the power converter 100 shown in FIG. FIG. 4 is a waveform diagram showing an example of the waveform of the converted voltage VY during the discharge operation of the power converter 100 shown in FIG. FIG. 5 is a waveform diagram showing an example of the output voltage VO waveform during the discharge operation of the power conversion device 100 shown in FIG.

As described above, during normal operation of the power converter 100, the control unit CNT controls the first to fourth switch elements SW1 to SW4 of the bridge circuit Y at a driving frequency within a predetermined range to set the preset frequency. The output voltage VO of the target value is output between the first output voltage terminal TO1 and the second output voltage terminal TO2.

In this case, for example, the bridge circuit Y outputs a converted voltage VY having a waveform as shown in FIG. 2, and the output voltage VO filtered by the LC filter F has an AC waveform as shown in FIG.

On the other hand, when the operation of the power conversion device 100 is stopped, the control unit CNT controls the first to fourth switch elements SW1 to SW4 of the bridge circuit Y within a preset period (for example, 3 seconds) after the output is stopped. to discharge the smoothing capacitor CS and set the voltage between the first output voltage terminal TO1 and the second output voltage terminal TO2 to a safe voltage lower than the target value. .

In particular, the control unit CNT controls the first to fourth switches of the bridge circuit Y so that the voltage between the first output voltage terminal TO1 and the second output voltage terminal TO2 becomes a preset safe voltage. By operating the elements SW1 to SW4, the losses of the first to fourth switch elements SW1 to SW4 of the bridge circuit Y cause the smoothing capacitor CS to discharge.

In this case, for example, the bridge circuit Y outputs a converted voltage VY having a waveform as shown in FIG. 4, and the output voltage VO filtered by the LC filter F becomes a safe voltage of 0V as shown in FIG.

Here, as described above, the control unit CNT operates by being supplied with control power.

This control unit CNT controls to turn off the control switch element CSW when the control power supply described above is supplied and is operating, and when the power conversion device 100 is stopped, the bridge circuit Y discharges to run.

As a result, a safe voltage lower than the target value can be set between the first output voltage terminal TO1 and the second output voltage terminal TO2.

On the other hand, when the supply of control power to the control unit CNT is interrupted and the control unit CNT stops, the control switch element CSW is turned on and discharge is performed by the discharge resistor RD.

That is, since the control unit CNT cannot operate (control) the bridge circuit Y when the control power supply is lost, the control switch element CSW is turned on so that the discharge current flows through the discharge resistor RD. Discharge the smoothing capacitor CS.

As described above, the control unit CNT cannot operate (control) the bridge circuit Y when the control power supply is lost, so the control unit CNT executes discharge by the discharge resistor RD as a backup operation.

Since the operation of the control unit CNT is a single-shot operation only in an emergency and no repetitive operation occurs, a small resistor with a low rated power can be selected as the discharge resistor RD.

Further, when the current detected by the detection circuit ID is out of the preset range while the DC/DC converter X is operating, the control unit CNT forces the operation of the DC/DC converter X. to stop.

As a result, for example, when the DC/DC converter X malfunctions and the DC voltage VD becomes too large, it is possible to prevent an overvoltage from being applied to the inside of the circuit.

In addition, the control unit CNT turns on the control switch element CSW in response to an external signal SA input by the user, thereby allowing a discharge current to flow through the discharge resistor RD and discharging the smoothing capacitor CS.

As a result, according to the user's operation, a discharge current flows through the discharge resistor RD, the smoothing capacitor CS is discharged, and the voltage between the first output voltage terminal TO1 and the second output voltage terminal TO2 is reduced. Voltage can be controlled to a safe voltage.

As described above, the power conversion device 100 according to one aspect of the present invention performs power conversion on the battery voltage VB output by the battery B, and outputs the AC output voltage VO to be supplied to the load Load. 100, a smoothing capacitor CS connected between a first DC voltage terminal TV1 to which a DC voltage VD based on a battery voltage VB is supplied and a second DC voltage terminal TV2; and a bridge circuit Y that outputs the converted voltage VY between the first converted voltage terminal TY1 and the second converted voltage terminal TY2 by the switching operations of the switch elements SW1 to SW4, and the conversion that the bridge circuit Y outputs. By controlling a filter (LC filter) F for filtering the voltage VY and outputting an output voltage VO, and a bridge circuit Y, the output voltage VO based on the converted voltage VY is applied to the first output voltage terminal TO1 and the second output voltage terminal TO1. and a control unit CNT for output between the output voltage terminal TO2.

Then, during normal operation of the power conversion device 100, the control unit CNT controls the switch elements SW1 to SW4 of the bridge circuit Y at a driving frequency within a predetermined range to set the preset target value output voltage VO to the first value. is output between the output voltage terminal TO1 and the second output voltage terminal TO2.

On the other hand, when the operation of the power converter 100 is stopped, the control unit CNT controls the switch elements SW1 to SW4 of the bridge circuit Y at an output stop frequency higher than the drive frequency within a preset period after the output is stopped. , the smoothing capacitor CS is discharged, and a safe voltage lower than the target value is set between the first output voltage terminal TO1 and the second output voltage terminal TO2.

As a result, according to the power conversion apparatus of the present invention, it is possible to discharge electric charges accumulated in the DC voltage smoothing capacitor and control the output voltage to a safe voltage when the operation is stopped while miniaturization is achieved.

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

100 Power converter CNT Control unit B Battery Load Load TB1 First battery terminal TB2 Second battery terminal X DC/DC converter CS Smoothing capacitor RD Discharging resistor (discharging means)
ID detection circuit CSW control switch element TV1 first DC voltage terminal TV2 second DC voltage terminal Y bridge circuit TY1 first converted voltage terminal TY2 second converted voltage terminal FLC filter (filter)
TO1 First output voltage terminal TO2 Second output voltage terminal SW1 First switch element SW2 Second switch element SW3 Third switch element SW4 Fourth switch element L1 First choke coil L2 Second choke coil CO Output capacitor VO Output voltage VY Conversion voltage VD DC voltage

Claims (11)

A power conversion device that converts a battery voltage output by a battery into power and outputs an AC output voltage to be supplied to a load,
a smoothing capacitor connected between a first DC voltage terminal to which a DC voltage based on the battery voltage is supplied and a second DC voltage terminal;
a bridge circuit that receives the DC voltage and outputs a converted voltage between a first converted voltage terminal and a second converted voltage terminal by switching operation of a switch element;
a filter that filters the converted voltage output by the bridge circuit and outputs the output voltage;
a control unit for outputting the output voltage based on the converted voltage between a first output voltage terminal and a second output voltage terminal by controlling the bridge circuit;
discharge means connected between said first DC voltage terminal and said second DC voltage terminal;
a control switch element connected in series with the discharge means between the first DC voltage terminal and the second DC voltage terminal and controlled by the control unit;
a detection circuit that detects a current flowing through the control switch element;
a DC/DC converter to which the battery voltage is input and which outputs the DC voltage between the first DC voltage terminal and the second DC voltage terminal;
The control unit
During normal operation of the power converter, the switch elements of the bridge circuit are controlled at a drive frequency within a predetermined range, and the output voltage of a preset target value is applied to the first output voltage terminal and the second output voltage terminal. and the output voltage terminal of
On the other hand, when the operation of the power converter is stopped, the switch element of the bridge circuit is controlled at an output stop frequency higher than the drive frequency within a preset period after the output is stopped, and the smoothing capacitor is Discharging and setting a safe voltage lower than the target value between the first output voltage terminal and the second output voltage terminal,
When the current detected by the detection circuit is out of a preset range while the operation of the DC/DC converter is controlled and the DC/DC converter is operated, the DC/DC converter force the operation to stop
A power conversion device characterized by: The control unit
By operating the switch element of the bridge circuit so that the voltage between the first output voltage terminal and the second output voltage terminal becomes the safe voltage, the switch element of the bridge circuit 2. The power converter according to claim 1, wherein the loss discharges the electric charge of the smoothing capacitor. 3. The power converter according to claim 1, wherein the safe voltage is 0V. A circuit including the discharge means and the control switch element is connected in parallel with the smoothing capacitor between the first DC voltage terminal and the second DC voltage terminal. 4. The power converter according to any one of items 1 to 3. 5. The apparatus according to claim 4, wherein said discharge means is a discharge resistor connected in series with said control switch element between said first DC voltage terminal and said second DC voltage terminal. Power converter. The control unit
It is designed to operate by supplying control power,
The control unit
When the control power supply is supplied and is operating, the control switch element is controlled to be turned off, and when the power conversion device is stopped, the bridge circuit performs a discharge operation. ,
On the other hand, when the supply of the control power source to the control unit is interrupted and the control unit stops, the discharging is performed by the discharging means. A power converter as described. The control unit
7. The smoothing capacitor is discharged by turning on the control switch element according to an external signal input by a user so that a discharge current flows through the discharge means. The power conversion device according to any one of the items. The electric power according to any one of claims 1 to 7 , wherein the power conversion device is mounted on a vehicle, and the output voltage output from the power conversion device is supplied to a load of the vehicle. conversion device. The control unit
Since the bridge circuit cannot operate when the control power supply is lost, the smoothing capacitor is discharged by turning on the control switch element so that a discharge current flows through the discharge means. The power converter according to claim 6 . The bridge circuit is
10. The power converter according to any one of claims 1 to 9 , wherein the power converter is a single-phase full-bridge circuit or a three-phase full-bridge circuit. A power conversion device for converting a battery voltage output by a battery into power and outputting an AC output voltage to be supplied to a load, wherein a first DC voltage terminal is supplied with a DC voltage based on the battery voltage. and a smoothing capacitor connected between and a second DC voltage terminal, the DC voltage is input, and the conversion voltage is transferred to the first conversion voltage terminal and the second conversion voltage terminal by the switching operation of the switch element a bridge circuit that outputs between, a filter that filters the converted voltage output by the bridge circuit and outputs the output voltage, and a filter that outputs the output voltage by controlling the bridge circuit to output the output voltage based on the converted voltage a controller for outputting between a first output voltage terminal and a second output voltage terminal; a discharging means connected between the first DC voltage terminal and the second DC voltage terminal; A control switch element connected in series with the discharge means and controlled by the control unit between the first DC voltage terminal and the second DC voltage terminal, and detecting a current flowing through the control switch element and a DC/DC converter to which the battery voltage is input and which outputs the DC voltage between the first DC voltage terminal and the second DC voltage terminal. a method,
The control unit
During normal operation of the power converter, the switch elements of the bridge circuit are controlled at a drive frequency within a predetermined range, and the output voltage of a preset target value is applied to the first output voltage terminal and the second output voltage terminal. and the output voltage terminal of
On the other hand, when the operation of the power converter is stopped, the switch element of the bridge circuit is controlled at an output stop frequency higher than the drive frequency within a preset period after the output is stopped, and the smoothing capacitor is Discharging and setting a safe voltage lower than the target value between the first output voltage terminal and the second output voltage terminal,
When the current detected by the detection circuit is out of a preset range while the operation of the DC/DC converter is controlled and the DC/DC converter is operated, the DC/DC converter force the operation to stop
A control method for a power converter, characterized by:

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