JPH10201247A - Power converter using auxiliary resonant commutation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability by connecting a snubber capacitor between the connecting point of snubber diode and intermediate connecting point of both-way auxiliary switch and the connecting a diode between the positive and negative poles of a DC power supply depending on the polarity of the connecting point and auxiliary switch. SOLUTION: Since an inverse recovery current bypass circuit is provided, a currents commutates through the resonance reactor L1 → snubber diode DS4 → snubber capacitor C → diode DA2 → inductance L2 of wiring and a current by the resonance reactor L1 by inverse recovery current and residual magnetic energy of inductance L2 of wiring flows into the snubber capacitor C to charge it as the electrostatic energy. Therefore, a large voltage is no longer applied to an auxiliary switch element SA2 and disadvantage such as breakdown of element can be eliminated. In this commutating mode, a small current flows to the resistor R even when the diode DS4 is on but the current charged in the snubber capacitor C after the diode DS4 turns off is almost discharged by the predetermined current path.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a series circuit of a bidirectional auxiliary switch element and a resonance reactor disposed between a connection point between a self-extinguishing type main switch element and a connection point between voltage dividing and smoothing capacitors. The present invention relates to a power converter using an auxiliary resonance commutation circuit.

[0002]

2. Description of the Related Art As a power converter using an auxiliary resonance commutation circuit, a circuit by William McMurray of the United States has been disclosed, and it can be said that it is a system that can be practically used as a large-capacity power converter. Although the description of the operation of this circuit is omitted, the reverse current due to the accumulated charge flows through the diode of the auxiliary switch element, and at the time of reverse recovery of the diode, high-frequency oscillation occurs due to the resonance reactor and the junction capacitance of the auxiliary switch element, and a large voltage is generated. There is a problem that the element is destroyed by being applied to the auxiliary element. However, a solution to this is not mentioned in the above document. As a method for solving this problem, there is Japanese Patent Application Laid-Open No. 7-337022 shown in FIG. 4, which has been proved to be an effective means. Hereinafter, the details will be described.

In FIG. 4, E denotes a DC power source, CD1 and CD2 denote voltage dividing smoothing capacitors connected in series to divide the DC power source E, S1 and S2 denote self-extinguishing type main switch elements, and D
1, D2 are diodes connected in parallel with the self-extinguishing type main switch elements S1 and S2 and of opposite polarity, C1 and C2 are resonant capacitors connected in parallel to the self-extinguishing type main switch elements S1 and S2, L1 Is a resonance reactor, L2 is an inductance of wiring, SA1 and SA2 are auxiliary switch elements constituting a bidirectional switch, in which an insulated gate bipolar transistor (hereinafter referred to as IGBT) is used, and diodes DA2 and DA1 are connected in parallel to each other. Have been. (The above is a power conversion device using an auxiliary resonance commutation circuit published by William Mmc Murray.)

[0004] CS1 and CS2 are snubber capacitors, DS
Reference numerals 1 and DS2 denote snubber diodes, and R1 and R2 denote resistors, which are added by JP-A-7-337022. By adding this circuit, the reverse recovery charge after the conduction of the diode DA1 is diverted to the snubber diode DS1 and flows into the snubber capacitor CS1, so that high-frequency oscillation is suppressed, and the auxiliary switching elements SA1,
It has been proven that this is an effective means for the problem of destruction of SA2.

[0005]

Although such an effect is obtained, in the case of the conventional circuit shown in FIG. 4, the circuit is relatively complicated, and the voltage applied to the snubber diode becomes a DC power supply voltage. When the DC power supply voltage is as high as 1500 V as in a power converter for an electric car, there is no high-speed diode suitable as a snubber diode, which hinders the realization of a power converter using this circuit.

An object of the present invention is to provide a special device which has an effect more than that of the conventional example, can reduce the number of parts, and can reduce the voltage applied to the snubber diode to half that of the conventional system. Is to do.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and is a self-extinguishing type main switch provided with a resonant capacitor and a diode in parallel, and the diode is provided with reverse polarity. Two elements are connected in series between the positive and negative electrodes of a DC power supply, and between a connection point of the series connection and a voltage dividing point between voltage dividing and smoothing capacitors connected in parallel to the DC power supply.
In a power converter using an auxiliary resonance commutation circuit including a series circuit of a bidirectional auxiliary switch element having a reverse-polarity parallel diode and a resonance reactor, both ends of the bidirectional auxiliary switch element have opposite polarities. A snubber diode connected in series is connected, a snubber capacitor is connected between a connection point of the snubber diode and an intermediate connection point of the bidirectional auxiliary switch, and a connection point of the snubber diode and a polarity of the auxiliary switch element are connected. A diode is connected between the positive and negative poles of the DC power supply according to the following.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings by way of embodiments. FIG. 1 shows a first embodiment of the present invention, and the portions denoted by the same reference numerals as those in FIG. 4 of the conventional example have the same configuration and the same function. In FIG. 1, snubber diodes DS4 and DS3 are provided in which the respective anodes are connected to both ends of the bidirectional switch, that is, the collectors of SA1 and SA2, and the cathodes are connected, and the connection point between DS3 and DS4 and the connection point between the auxiliary switch element and That is, a snubber capacitor C is connected between the connection point between the emitters of SA1 and SA2, and a series circuit of a diode DS and a resistor R is connected between the connection point of DS3 and DS4 and the positive electrode of the DC power supply. It is connected to the positive side of the DC power supply.

In describing the operation, the load current is assumed to be zero for simplicity, and the commutation operation of the self-extinguishing type main switch from S2 to S1 will be described. FIG. 3 is a waveform diagram for explaining the operation of the embodiment. When the self-extinguishing main switch element S2 and the auxiliary switch element SA1 are turned off at time T0, the resonance reactor including the wiring inductance L2 is turned on. L1 and resonance capacitors C1 and C2
As a result, a sinusoidal current flows to zero at time T1 as shown.

However, the reverse current due to the electric charge accumulated in the diode DA1 existing in the path where the resonance current flows is determined at the time T2 determined by the characteristics of the diode, the current reduction rate, and the like.
At time T2, the diode reversely recovers and rapidly turns off, so that a large voltage tends to be generated in the resonance reactor L1 and the wiring inductance L2.

However, in the present invention, since there is a bypass circuit for the reverse recovery current, the resonance reactor L1 → snubber diode DS4 → snubber capacitor C → diode DA
(2) The current is commutated to the wiring inductance L2, and the current due to the remanent magnetic energy of the resonance reactor L1 and the wiring inductance L2 due to the reverse recovery current flows through the snubber capacitor C and is charged as electrostatic energy. Therefore, a large voltage is not applied to the auxiliary switch element SA2 (DA1), and the problem of element destruction is eliminated. In this commutation mode, a small amount of current flows through the resistor R even when the diode DS4 is turned on. However, most of the current charged in the snubber capacitor C after DS4 is turned off is the snubber capacitor C → discharge resistor R → discharge diode → positive power supply → A current that discharges to E / 2 flows through the auxiliary switch element SA1.

Although the case where the diode DA1 performs reverse recovery has been described above, the operation at the time of reverse recovery of the diode DA2 is slightly different, and while the current flows through the snubber diode DS3, the resistance of the resistor R is increased by the action of the discharging diode DS. No current flows, and the snubber capacitor is discharged next time when the auxiliary switch element SA1 is turned on, and the same effect can be obtained as the operation of the snubber circuit.

FIG. 2 shows a second embodiment of the present invention. The operation is exactly the same except that the polarity of the auxiliary switch element is changed and the insertion point of the discharge circuit is changed. In addition, the self-extinguishing type main switch element and auxiliary switch element are not limited to those shown by the symbols, and any switch element that satisfies the characteristics such as a transistor may be used. Needless to say.

[0014]

As described above, according to the present invention, since a snubber circuit can be provided closer to each auxiliary switching element than in the conventional method, the amount of surge voltage applied to the auxiliary switching elements can be reduced. Used diode DS3
The voltage rating of DS4 and DS can be reduced to 1/2 of that of the conventional system, it is possible to use a small diode with better characteristics, and the number of parts can be reduced. It greatly contributes to downsizing.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a main part of a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a main configuration of a second embodiment of the present invention.

FIG. 3 is a waveform chart shown for explaining the operation of FIG. 1;

FIG. 4 is a conventional circuit diagram of a power conversion device using an auxiliary resonance commutation circuit.

[Explanation of symbols]

E DC power supply CD1, CD2 Voltage division smoothing capacitor S1, S2 Self-extinguishing type main switch element D1, D2 Anti-parallel diode C1, C2 Resonance capacitor L1 Resonance reactor L2 Wiring inductance SA1, SA2 Auxiliary switch element DS1, DS2, DS3 DS4 snubber diode DS discharge diode R, R1, R2 discharge resistance

Claims (1)

[Claims] 1. A resonance capacitor and a diode in parallel,
The diode has two self-extinguishing main switch elements having opposite polarities connected in series between the positive and negative poles of a DC power supply, and a connection point of the series connection and a voltage division smoothing connected in parallel to the DC power supply. In a power converter using an auxiliary resonance commutation circuit including a series circuit of a bidirectional auxiliary switch element having a reverse-polarity parallel diode and a resonance reactor between a voltage dividing point between capacitors and a bidirectional auxiliary switch element, A snubber diode connected in series so as to have opposite polarities is connected to both ends of the switch element, and a snubber capacitor is connected between a connection point of the snubber diode and an intermediate connection point of the bidirectional auxiliary switch. An auxiliary resonance commutation comprising a diode connected between a connection point of the diode and a positive or negative pole of the DC power supply according to a polarity of the auxiliary switch element. Power conversion apparatus using the road.