JPH09275674A - Power converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve efficiency of a converter by forming a snubber circuit of self-arc-extinguishing type element out of a DC circuit consisting of a diode and a capacitor, and forming a voltage clamp circuit consisting of a snubber capacitor 3 out of a resistor, a switching element and a control circuit. SOLUTION: An overvoltage control circuit is constituted of a snubber circuit consisting of a series circuit having a snubber diode 2 and a snubber capacitor 3 parallel-connected to a self-arc-extinguishing type element 1, a series circuit having a resistor 9 and a switching element 11 parallel-connected to the snubber capacitor 3, and a voltage clamp type snubber circuit which clamps the voltage of the snubber capacitor 3 to a fixed value or lower by on-off-controlling the switching element 11 according to the voltage of the snubber capacitor 3 and spending the energy of the snubber capacitor 3 with the resistor 9. It is thus possible to improve efficiency of a small converter suitable for forming a power converter by serial-connecting a plurality of self-arc-extinguishing type elements such as IGBT.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power converter including self-extinguishing elements in which overvoltage suppressing circuits are connected in parallel, and more particularly to a power converter having an improved overvoltage suppressing circuit.

[0002]

2. Description of the Related Art A power converter using a self-extinguishing type switching element can supply a sinusoidal AC voltage / current to a load by PWM (Pulse Width Modulation) control, and the harmonics on the power supply side and the load side. Advantages such as wave suppression, power factor improvement, and device miniaturization are obtained.

Recently, IGBT (Insulated Gate Bip)
olar Transistor) and MCT (MOS Controlled)
Thyristor) and other new self-extinguishing elements are becoming higher in voltage and current. These self-extinguishing elements are GTO (G
ate Turn Off) It has various advantages over thyristors. One of them is miniaturization of the snubber circuit that suppresses overvoltage applied to the self-arc-extinguishing element.

The snubber circuit suppresses a transient current or abrupt increase in voltage generated when the self-extinguishing element performs a switching operation, thereby reducing loss of the switching element and protecting the element. Circuit. In the case of a GTO thyristor, the snubber circuit must be constructed so that the voltage when the device turns off rises relatively slowly from 0, and that when it turns off, the device current rises relatively slowly from 0. I have to. Therefore, the snubber circuit of the GTO thyristor must be equipped with a large-sized snubber capacitor and reactor, and the energy stored in the snubber circuit must be transferred from the snubber circuit to the snubber circuit in some form at each switching operation. Need to release.

On the other hand, recent switching elements such as IGBTs have relatively moderate requirements for snubber circuits due to the characteristics of the elements. For example, when the element turns off, even if the voltage of the element rises in an extremely short time, there is no problem in the operation of the element, and even if the current of the element rises in an extremely short time when the element turns on. No problem occurs. Therefore, in a self-extinguishing element such as an IGBT, the snubber capacitor and reactor can be made extremely small compared to the case of a GTO thyristor, and the energy that needs to be stored and released in the snubber circuit can also be obtained. Very few. Therefore, if a power conversion circuit is configured using a new self-extinguishing element such as an IGBT, the device can be downsized as compared with the case where a GTO thyristor is used, and the efficiency of the converter accompanying snubber energy consumption can be increased. Can be avoided.

However, with the current technology, the withstand voltage of the self-turn-off device such as the IGBT can be obtained at most about several thousand volts. In order to apply it to a high-voltage / high-power converter whose output voltage exceeds tens of thousands of volts, the withstand voltage is insufficient to form a switching valve with a single element. In such a case, a number of self-extinguishing type elements are connected in series to form one switching valve, and a number of elements connected in series are controlled by the same switching signal to create a high withstand voltage switching valve. You will get it. When such a large number of elements are connected in series and used, it is difficult to reduce the size of the snubber circuit. The reason will be described below.

FIG. 7 shows an example of the structure of a switching valve in the case where a large number of IGBTs are connected in series to form a power converter according to a conventionally used technique. In FIG. 7, 1a to 1d are IGBTs connected in series, 2a to 2d are snubber diodes, and 3a to 3d
Is a snubber capacitor, and the snubber circuit is composed of a snubber diode and a snubber capacitor. 4a to 4d are snubber resistors, and the resistors consume the energy stored in the snubber circuit each time the IGBT switches.

In the circuit of FIG. 7, an RDC (Resistor Diode Capacitor) snubber having the same configuration as that used in a GTO thyristor is used as the IGBT snubber circuit.

As described above, the IGBT allows a steep rise in the element voltage at the time of turn-off, so that it is not necessary to use a snubber such as the RDC snubber which makes the voltage of the snubber capacitor zero at every switching. . A voltage clamp type snubber that simply clamps the voltage of the snubber capacitor at a constant level may be used. However, when a large number of elements are connected in series, it is difficult to construct a circuit for clamping the voltage of the snubber capacitor to an appropriate voltage level. Therefore, in the conventional technique, the RDC snubber has to be used.

Also, the capacity of the snubber capacitor should be small because the voltage increase rate that the IGBT can tolerate is originally high. However, when a large number of elements are connected in series, the snubber capacitor having a large capacity is required. Will be required. This is because a large number of elements connected in series do not always switch at the same time, but perform switching operation with some variations. When the capacity of the snubber capacitor is small, when the element turns off,
Among the elements connected in series, the voltage of the first turned-off element rises sharply, and the voltage sharing of the first turned-off element is distributed to the other elements in a short time until the other elements start the turn-off operation. Compared to this, the price is extremely high. When the shared voltage of only one of the many elements connected in series is higher than that of other elements, a large stress concentrates only on the element with the high shared voltage, which shortens the life or is unacceptable. Will lead to the destruction of the element.

For the above reason, even if the conventional technique uses a self-arc-extinguishing element such as an IGBT, in order to use a large number of elements connected in series, the snubber circuit has the same size as a conventional GTO. Has to use a snubber circuit that greatly reduces the efficiency of the converter.

Further, in the conventional technique shown in FIG. 7, the power source of the gate control circuit for driving the IGBT is the insulating transformers 7a to 7a.
Each IGBT is insulated and supplied at d. This is because the gate control circuit needs insulation because each IGBT has a different potential. However, when this prior art is applied to a high voltage converter of tens of thousands of volts, the insulation transformer 7a
Insulation transformer 7
It is disadvantageous in terms of size and cost of a to 7d. Since the insulating transformers 7a to 7d are required for each IGBT, the size and cost of the insulating transformers 7a to 7d greatly affect the size and cost of the entire transformer.

[0013]

In the prior art, the IGB is used.
Even when using a self-extinguishing element such as T, in order to use a large number of elements connected in series, it is necessary to use G as a snubber circuit.
As with the TO and the like, there is a problem that a snubber circuit that has a large size and causes a reduction in the efficiency of the converter must be used. Further, in the prior art, when a self-extinguishing element such as an IGBT is used for a high voltage converter, the size of the insulating transformer required to supply the power source for the gate control circuit is large, which is disadvantageous in terms of cost. There was a problem to say.

Therefore, an object of the present invention is to improve an overvoltage suppressing circuit connected in parallel to a self-extinguishing element and to configure a power converter by connecting a large number of self-extinguishing elements such as IGBTs in series. An object of the present invention is to provide a power conversion device that is suitable and can improve the efficiency of the converter.

[0015]

In order to achieve the above object, a power converter according to the present invention is a power converter comprising self-extinguishing elements in which overvoltage suppressing circuits are connected in parallel. A snubber circuit comprising the series circuit of a snubber diode and a snubber capacitor connected in parallel to the self-extinguishing element, the series circuit of a resistor and a switching element connected in parallel to the snubber capacitor, A voltage clamp type snubber circuit that clamps the voltage of the snubber capacitor to a certain value or less by controlling the switching element on / off according to the voltage of the snubber capacitor and causing the energy of the snubber capacitor to be consumed by the resistor. It is characterized by being configured.

According to a second aspect of the present invention, there is provided a power conversion device comprising a self-extinguishing element in which an overvoltage suppressing circuit is connected in parallel, wherein the overvoltage suppressing circuit includes the self-extinguishing circuit. DC circuit comprising a snubber circuit composed of a series circuit of a snubber diode and a snubber capacitor connected in parallel with the snubber capacitor, and a switching element connected in parallel with the snubber capacitor and controlled to be turned on / off in accordance with the voltage of the snubber capacitor. A DC converter circuit, which switches the switching element when the voltage of the snubber capacitor of the snubber circuit exceeds a certain limit, and is constituted by the switching element.
A surplus energy of the snubber capacitor is used as a power source for the gate control circuit of the self-turn-off device by a C-DC converter circuit. This eliminates the need for an insulation transformer, which was required in the past, to supply power to the gate control circuit.

Further, the power converter according to the invention of claim 3 is a power converter comprising self-extinguishing elements in which overvoltage suppressing circuits are connected in parallel. DC circuit comprising a snubber circuit composed of a series circuit of a snubber diode and a snubber capacitor connected in parallel with the snubber capacitor, and a switching element connected in parallel with the snubber capacitor and controlled to be turned on / off in accordance with the voltage of the snubber capacitor. A DC-DC circuit configured by a DC converter circuit, which switches the switching element when the voltage of the snubber capacitor exceeds a certain limit, and is configured by the switching element.
The converter circuit regenerates the surplus energy of the snubber capacitor into the DC capacitor of the main circuit of the power conversion device including the self-extinguishing element to improve the efficiency of the power converter.

The power converter according to a fourth aspect of the present invention is a power converter configured by a self-extinguishing element that does not require a snubber in which overvoltage suppressing circuits are connected in parallel.
The overvoltage suppressing circuit is composed of a series circuit of a switching element and a resistor connected in parallel to the self-extinguishing element and a control circuit for performing on / off control of the switching element according to the terminal voltage of the self-extinguishing element. However, when the voltage of the self-arc-extinguishing element exceeds a certain limit, the switching element is switched, and the surge energy applied to the self-arc-extinguishing element is consumed by the resistor.

Further, the power converter according to the invention of claim 5 is a power converter comprising a self-extinguishing element which does not require a snubber, in which the overvoltage suppressing circuits are connected in parallel. A series circuit of a switching element and a resistor connected in parallel to the self-extinguishing element,
A capacitor is connected in parallel to the resistor as a means for increasing the surge absorption capacity, and the switching element is constituted by a control circuit for performing on / off control according to the terminal voltage of the self-arc-extinguishing element. The surge energy applied to is once absorbed by the capacitor and then consumed by the resistor.

Furthermore, the power converter according to the invention of claim 6 is the self-extinguishing element of the power converter according to the invention of claim 4 or 5. The self-extinguishing element is provided by providing temperature detecting means for detecting the temperature, inputting a temperature signal from the temperature detecting means to the control circuit, and changing the allowable value of the overvoltage suppression level according to the element temperature. To improve the utilization rate of.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a power conversion device according to the invention described in claim 1 will be described below with reference to FIG. FIG. 1 is a configuration diagram of an embodiment showing only a main part of a power conversion device according to a first aspect of the invention.

The invention according to claim 1 is characterized in that a voltage clamp circuit composed of a switching element, a resistor and a control circuit is added to form a voltage clamp type snubber circuit as compared with the prior art.

That is, in FIG. 1, the series circuit of the diode 2 and the capacitor 3 constitutes a snubber circuit of the self-extinguishing element 1, and the resistor 9, the switching element 11, and the control circuit 10 clamp the voltage of the snubber capacitor 3. A circuit is constructed, and a voltage clamp type snubber circuit is constructed by these two circuits.

When the self-arc-extinguishing element 1 of the main circuit is turned off, the current flowing through the self-arc-extinguishing element 1 flows into the snubber capacitor 3 via the snubber diode 2 and the voltage of the snubber capacitor 3 is temporarily changed. To rise. When the control circuit 10 detects that the voltage of the snubber capacitor 3 has risen above a certain voltage, it turns on the switching element 11. Then, the electric charge accumulated in the snubber capacitor 3 is discharged through the resistor 9, so that the voltage of the snubber capacitor 3 gradually decreases.

When the control circuit 10 detects that the voltage of the snubber capacitor 3 has become a certain voltage or less, it turns off the switching element 11, and as a result,
The voltage of the snubber capacitor 3 is normally clamped within a certain voltage range.

As can be seen from the above description, the switching element 11 is applied with the same voltage as that of the self-extinguishing element 1 constituting the power converter, so that the withstand voltage of the switching element 11 is self-extinguishing. It is necessary as much as the element 1. As described above, since it is necessary to prepare a high withstand voltage switching element for each self-arc-extinguishing element of the main circuit, it seems that there is a concern that the cost of the power conversion device may increase in this embodiment. To be

However, in reality, the switching element 11
The current rating may be much smaller than that of the self-arc-extinguishing element 1, and therefore the increase in cost is negligible. The reason will be described below with reference to specific numerical examples.

If an element such as a recent IGBT is used as a switching element, the capacity of the snubber capacitor 3 is 0.3 μF when the element has a rated current of 3000 A class.
About. Rated voltage of self-extinguishing element 1 is 3000V
As the voltage of the snubber capacitor 3 in the steady state,
00V. If the voltage of the snubber capacitor 3 temporarily rises to 2000V and the voltage of this rise is returned to 1500V in 50 μs, the time constant of the resistor 9 and the snubber capacitor 3 is 36 μs.
The value of the resistor 9 is 72Ω.

Therefore, the maximum current flowing through the switching element 11 is a very small value of 28A. Moreover, since this current only needs to flow in pulses, the current rating of the switching element 11 may be much smaller than that of the self-arc-extinguishing element 1. Therefore, the cost of the switching element 11 is sufficiently smaller than that of the self-arc-extinguishing element 1, and the increase in the cost of replacing the power conversion device due to the addition of the switching element 11 is negligible.

When a power conversion device is constructed by using a plurality of self-arc-extinguishing elements shown in FIG. 1 connected in series as a switching valve, by adopting such a configuration, a large number of self-arc-extinguishing elements are connected in series. It is possible to independently clamp the voltage of the snubber capacitor 3 of each element to a constant voltage. Therefore, the voltage difference between the self-extinguishing elements connected in series can be kept within a predetermined range.
It is not necessary to increase the capacity of the snubber capacitor.

In the power converter according to the invention described in claim 1, the electric charge accumulated in the snubber capacitor 3 is consumed by the resistor 9. It is conceivable that the energy consumed by the resistor 9 is converted into DC power by a DC-DC converter circuit constituted by the switching element 11, for example, a chopper circuit, and used.

The force conversion device according to the second aspect of the present invention can be applied to such a case. Hereinafter, one embodiment of the power conversion device according to the invention described in claim 2,
This will be described with reference to FIG. FIG. 2 is a configuration diagram of an embodiment showing only a main part of a power conversion device according to a second aspect of the invention.

In FIG. 2, a chopper circuit composed of a switching element 11, a diode 12, a reactor 13 and a capacitor 14 converts energy of the voltage rise of the snubber capacitor 3 into low-voltage DC power.

In FIG. 2, the low-voltage DC power obtained in the capacitor 14 is used as the power supply for the gate control circuit 5 of the self-arc-extinguishing element 1. In the embodiment shown in FIG. 2, when the snubber circuit is clamped in this way, the snubber capacitor 3
The energy released from the device is converted into low-voltage DC power for use.

In the embodiment shown in FIG. 2, the output power of the chopper circuit constituted by the switching element 11 is used as the power source of the gate control circuit 5 of the self-arc-extinguishing element 1, but the present invention is not limited to this. Can be used as a power source for various electric appliances required for each switching element, such as a cooling fan and a failure signal generating circuit. Further, snubber loss can be reduced by converting the output power of the chopper circuit into a DC circuit of the main circuit of the power converter or converting the DC power into AC power and regenerating it into another AC power supply.

Further, in the above description, the circuit constituted by the switching element 11 is explained as a chopper circuit, but there is no problem even if it is a widely used general DC-DC converter circuit as well as the chopper circuit. It is also possible to configure a DC-DC converter circuit by the switching element 11 and regenerate the output power of the DC circuit of the main circuit of the power converter, for example.

The force conversion device according to the third aspect of the present invention can be applied to such a case. Hereinafter, an embodiment of the power conversion device according to the invention described in claim 3,
This will be described with reference to FIG. FIG. 3 is a configuration diagram of an embodiment showing only a main part of a power conversion device according to a third aspect of the invention.

In FIG. 3, the outputs of four DC-DC converter circuits composed of switching elements 11a to 11d, control circuits 10a to 10d, transformers 16a to 16d, and diodes 15a to 15d are connected in series to form a power converter. Is connected to the DC circuit of the main circuit. In this embodiment, the switching elements 11a to 11d are
Energy is transmitted to the secondary side of the transformers 16a to 16d via the transformers 16a to 16d each time the switch is turned on. When the voltage of the snubber capacitors 3a to 3d rises above a certain limit due to the switching operation of the self-extinguishing type elements 1a to 1d, the switching elements 11a to 11d are switched to perform the snubber operation on the secondary side of the transformers 16a to 16d. By sending the energy extracted from the capacitors 3a to 3d, the voltage of the snubber capacitors 3a to 3d is lowered, and at the same time, the excess energy is regenerated to a DC capacitor or the like (not shown) in the main circuit of the power converter.

In the power converters described so far,
The self-extinguishing element 1 is always connected to a snubber circuit in which a snubber diode and a snubber capacitor are connected in series. However, recent power switching elements have improved breakdown resistance and expanded the safe operation area. Some don't necessarily need a snubber circuit. For example, it is applied to a high breakdown voltage, small current converter or the like, which requires a high breakdown voltage but requires a relatively small current. Even when a power switching element is used for such an application, there is always a possibility of element destruction due to a transient surge voltage, so a circuit that selectively absorbs only the transient surge voltage is necessary.

The force conversion device according to the fourth aspect of the present invention can be applied to such a case. Hereinafter, one embodiment of the power conversion device according to the invention described in claim 4,
This will be described with reference to FIG. FIG. 4 is a configuration diagram of an embodiment showing only a main part of a power conversion device according to a fourth aspect of the invention.

In FIG. 4, the overvoltage suppressing circuit is composed of the switching element 11, the control circuit 10, and the resistor 17. When the control circuit 10 detects that the voltage of the self-extinguishing element 1 exceeds a certain constant value, the switching element 11 is turned on and the surge energy is consumed by the resistor 17. With such a configuration, it is possible to protect the self-arc-extinguishing element 1 from a breakdown due to a surge voltage with a simple configuration.

When handling an output current larger than that of the embodiment of FIG. 4, it becomes difficult to instantaneously divide the surge energy into the resistor 17. When a large current is shunted to the resistor 17, the voltage of the resistor 17 is proportional to the current,
As a result, the effect of suppressing the surge voltage is reduced.

The force conversion device according to the fifth aspect of the present invention can be applied to such a case. An embodiment of the power conversion device according to the invention described in claim 5 will be described below.
This will be described with reference to FIG.

In FIG. 5, a capacitor 18 is newly added in parallel with the resistor 17. Even when it is necessary to process a surge pulse having a relatively large energy, it is possible to suppress the surge voltage to a lower level than when only the resistor 17 is used, by turning on the switching element 11 and shunting the surge current to the capacitor 18. become. The surge energy once stored in the capacitor 18 is gradually discharged through the resistor 17 and finally consumed by the resistor 17.

As is generally known, the safe operating area, which is the range of voltage and current at which the switching element can be safely operated, varies depending on the temperature of the switching element. In order to effectively use the switching element, it is possible to effectively use the switching element if the allowable value of the surge voltage applied to the element is also determined in consideration of the temperature.

The power converter according to the sixth aspect of the present invention can be applied to such a case. Hereinafter, an embodiment of the power conversion device according to the invention described in claim 6,
This will be described with reference to FIG.

In FIG. 6, the temperature of the self-arc-extinguishing element 1 is detected by the element temperature detecting means 19, and the allowable overvoltage value in the control circuit 10 is varied according to the temperature of the self-arc-extinguishing element 1. With such a configuration, the optimum overvoltage allowable value can be set according to the temperature of the self-extinguishing element 1, and as a result, the utilization rate of the self-extinguishing element is improved, and It is possible to improve efficiency and reduce cost.

The power converter according to the invention described in claim 6 is an example in which the element temperature detecting means is provided in the embodiment shown in FIG. 5, but the element temperature detecting means is provided in the embodiment shown in FIG. Even if provided, the same effect as described above can be obtained.

[0049]

As described above, according to the power conversion circuit of the present invention, it is possible to clamp the voltage of the snubber capacitor of the self-arc-extinguishing element to a constant value. As a result, a snubber circuit with less loss can be constructed.

According to the power converter of the second aspect of the present invention, the surplus energy stored in the snubber capacitor can be used as the power source for the gate control circuit of the self-extinguishing element. This eliminates the need for an insulation transformer, which was required in the past.

Furthermore, according to the power conversion device of the third aspect of the present invention, the excess energy stored in the snubber capacitor is used as the regenerative power, so that the efficiency can be improved.

Furthermore, according to the power conversion device of the fourth aspect of the present invention, the overvoltage can be suppressed with a low loss which does not require a snubber. Further, according to the power conversion device according to the invention described in claim 5, it is possible to cope with surge energy larger than that of the power conversion device according to the invention described in claim 4,
Overvoltage can be suppressed with low loss.

Further, according to the power conversion device of the invention described in claim 6, in the power conversion device of claim 4 or 5, fluctuations in the safe operation area due to temperature changes of the self-extinguishing element. The operating characteristics can be optimized according to the above, and the utilization rate of the self-arc-extinguishing element can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an embodiment showing only a main part of a power conversion device according to a first aspect of the invention.

FIG. 2 is a configuration diagram of an embodiment showing only a main part of a power conversion device according to a second aspect of the invention.

FIG. 3 is a configuration diagram of an embodiment showing only a main part of a power conversion device according to a third aspect of the invention.

FIG. 4 is a configuration diagram of an embodiment showing only a main part of a power conversion device according to a fourth aspect of the invention.

FIG. 5 is a configuration diagram of an embodiment showing only a main part of a power conversion device according to a fifth aspect of the invention.

FIG. 6 is a configuration diagram of an embodiment showing only a main part of a power conversion device according to a sixth aspect of the invention.

FIG. 7 is a configuration diagram showing only a main part of a conventional power conversion device.

[Explanation of symbols]

1, 1a to 1d ... Self-extinguishing type element 2, 2a to 2d
... Snubber diodes 3, 3a to 3d ... Snubber capacitors 4a to 4d
... Snubber resistors 5, 5a to 5d ... Gate control circuits 6a to 6d
... Rectifier circuit 7a to 7d ... Insulation transformer 8a to 8d
… Optical fiber 9,17… Resistors 10,10a to 10d
... Control circuits 11, 11a to 11d ... Switching element 12
… Diode 13… Reactor 14
… Capacitors 15a to 15d… Die-auto 16a to 16d
… Transformer

Claims (6)

[Claims] 1. A power conversion device comprising a self-extinguishing element in which an overvoltage suppressing circuit is connected in parallel, wherein the overvoltage suppressing circuit includes a series of a snubber diode and a snubber capacitor connected in parallel to the self-extinguishing element. A voltage clamp type snubber circuit comprising a snubber circuit composed of a circuit, a series circuit of a resistor and a switching element connected in parallel to the snubber capacitor, and a control circuit for ON / OFF controlling the switching element according to the voltage of the snubber capacitor. A power converter characterized by being configured. 2. A power conversion device comprising a self-extinguishing element in which an overvoltage suppressing circuit is connected in parallel, wherein the overvoltage suppressing circuit is a series connection of a snubber diode and a snubber capacitor connected in parallel to the self-extinguishing element. DC-DC including a snubber circuit composed of a circuit and a switching element which is connected in parallel to the snubber capacitor and which is on / off controlled according to at least the voltage of the snubber capacitor.
A power conversion device comprising a converter circuit, wherein output power of the DC-DC converter circuit is used as a power source of a gate control circuit of the self-turn-off device. 3. A power converter comprising a self-extinguishing element in which an overvoltage suppressing circuit is connected in parallel, wherein the overvoltage suppressing circuit is a series connection of a snubber diode and a snubber capacitor connected in parallel to the self-extinguishing element. DC-DC including a snubber circuit composed of a circuit and a switching element which is connected in parallel to the snubber capacitor and which is on / off controlled according to at least the voltage of the snubber capacitor.
A power conversion device comprising a converter circuit, wherein output power of the DC-DC converter circuit is used as regenerative power. 4. A power conversion device comprising self-extinguishing elements in which an overvoltage suppressing circuit is connected in parallel, wherein the overvoltage suppressing circuit includes a switching element and a resistor connected in parallel to the self-extinguishing element. A power conversion device comprising a series circuit and a control circuit for performing on / off control of the switching element according to a terminal voltage of the self-extinguishing element. 5. A power conversion device comprising a self-extinguishing element in which an overvoltage suppressing circuit is connected in parallel, wherein the overvoltage suppressing circuit includes a switching element and a resistor connected in parallel to the self-extinguishing element. A power conversion device comprising a series circuit, a capacitor connected in parallel with the resistor, and a control circuit for performing on / off control of the switching element in accordance with a terminal voltage of the self-extinguishing element. 6. The self-extinguishing element is provided with temperature detecting means for detecting the temperature of the self-extinguishing element, and a temperature signal from the temperature detecting means is input to the control circuit to set the overvoltage suppression level. It is variable, It is characterized by the above-mentioned.
Alternatively, the power conversion device according to claim 6.