JPH10136637A - Snubber circuit of semiconductor switch element - Google Patents

Abstract

(57) Abstract: Provided is a snubber circuit that suppresses a voltage jump when a semiconductor switch element used in a power conversion circuit is turned off. A diode 11, a capacitor 12, and a resistor 1 are provided.
Diode 1 of discharge blocking RCD snubber circuit consisting of
1 and a capacitor 21 connected in parallel is added to both ends of IG.
When the BT 3 is turned off, the surge voltage due to the parasitic inductance 14 of the snubber circuit 20 is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a snubber circuit of a semiconductor switch element such as a diode, a thyristor, and a transistor used in a power conversion circuit.

[0002]

2. Description of the Related Art FIG. 8 is a circuit diagram showing a conventional example of a snubber circuit of a semiconductor switch element of this kind, wherein 1 is a DC power supply constituting a DC circuit, 2 is a load of this power conversion circuit, and 3 is An insulated gate bipolar transistor (hereinafter simply referred to as IGBT) as a semiconductor switch element,
4 parasitic inductance of the main circuit wiring of the power conversion circuit (L _M), 5 the return diode recirculates load 2 current at the OFF time of the IGBT 3, 10 is a snubber circuit of IGBT 3.

[0003] The snubber circuit 10 is composed of a diode 11, a capacitor 12 as a first capacitor, resistor 13, the parasitic inductance of the wiring of the snubber circuit (L _S) 14 serving as a first diode. The IGBT 3 of the power conversion circuit shown in FIG. 8 performs a switch operation based on a drive signal from a drive circuit (not shown), and converts the power of the DC power supply 1 to a desired value by this operation.
Power.

The operation of the snubber circuit 10 will be described below with reference to a waveform diagram shown in FIG. The initial value of the voltage across the capacitor 12 of snubber circuit 10 (V _S), the resistance 1
3 and has a value equal to the voltage (E) of the DC power supply 1. In FIG. 8, when the IGBT 3 changes from on to off based on the drive signal,
During turn-off of BT3, the main circuit current by the change in (I _M) to both ends of the parasitic inductance 4 L _M · dI _M /
dt is generated. Here, L _M is the inductance value of the parasitic inductance 4. In order to prevent the IGBT 3 from being damaged by overvoltage due to the voltage generated at both ends of the parasitic inductance 4, the snubber circuit 10
Is provided.

First, when the IGBT 3 is turned off, the IGB
T3 of the collector current (I _C, FIG. 9 (b) refer) begins to decrease, the collector-emitter voltage across the terminals of IGBT3 in this case (V _CE, see FIG. 9 (a)) at both ends of the parasitic inductance 4 above Voltage E due to the voltage generated at
, The die auto 11 becomes conductive, and a current (I _S , see FIG. 9C) flows through a path of DC power supply 1 → load 2 → inductance 14 → diode 11 → capacitor 12 → inductance 4 → DC power supply 1. the current I _C of IGBT3 is decreased in response to increase of the current I _S,
A so-called commutation operation is started.

During this time, the rate of change of the main circuit current I _M becomes smaller than the rate of change of the current I _C , so that the voltage (L _M · dI _M / dt) across the parasitic inductance 4.
And the peak value of the voltage V _CE of the IGBT 3 is suppressed. Here, since the parasitic inductance 14 is present in the snubber circuit 10, the current rate of change of the current _{I S, ΔV P = L S} · dI S / dt becomes a voltage is generated across the parasitic inductances 14. This L _S
Is the inductance value of the parasitic inductance 14.
That is, immediately after the start of the turn-off, the voltage V _S across the capacitor 12 is substantially equal to the voltage E of the DC power supply 1, so that the voltage V _{CE of the} IGBT 3 becomes E + ΔV _P.

[0007] The rise of the voltage V _S across the capacitor 12 due to the current I _S is discharged to the DC power supply 1 via the resistor 13.

[0008]

When the conventional snubber circuit of the semiconductor switch element is used, especially when the power conversion circuit is large and large in capacity, the current change rate of the main circuit current ( _IM ) becomes large. and it is difficult to parasitic inductance of the snubber circuit (L _S) smaller. As a result, a higher voltage is applied to the semiconductor switch element at the time of turn-off.

For this reason, in order to prevent the semiconductor switch element from being damaged by overvoltage due to the above-mentioned voltage, a semiconductor switch element having a higher withstand voltage is required. As a result, the power conversion circuit becomes larger and the manufacturing cost is increased. Also increased. SUMMARY OF THE INVENTION An object of the present invention is to provide a snubber circuit of a semiconductor switch element which solves the above-mentioned problems.

[0010]

According to a first aspect of the present invention, there is provided a semiconductor switching element used in a power conversion circuit, wherein the switching element is connected between an anode and a cathode terminal, between a collector and an emitter terminal, or between a source and a drain of each semiconductor switching element. In a snubber circuit of a semiconductor switch element having a configuration in which a series circuit including a first diode and a first capacitor is connected in parallel between terminals, a second capacitor connected in parallel to both ends of the first diode is added.

According to a second aspect of the present invention, in the snubber circuit of the semiconductor switch element, a series circuit including a second capacitor and a resistor connected in parallel to both ends of the first diode is added. A third invention is a semiconductor switch element used in a power conversion circuit, wherein a plurality of semiconductor switch elements are connected in series between an anode and a cathode terminal, between collector and emitter terminals, or between a source and a drain terminal of each semiconductor switch element. In a snubber circuit of a semiconductor switch element having a configuration in which a series circuit including a diode and a first capacitor is connected in parallel, a second capacitor connected in parallel is added to both ends of each of the plurality of series-connected diodes.

According to a fourth aspect of the present invention, in the snubber circuit of the semiconductor switch element, a series circuit including a second capacitor and a resistor connected in parallel to both ends of each of the plurality of series-connected diodes is added. In a fifth aspect based on the first or third aspect, the semiconductor switch element is a self-extinguishing device, and a driving circuit or a driving signal of the self-extinguishing device is used.
The turn-on time of the self-extinguishing device is adjusted to a predetermined value.

According to the present invention, the above-described commutation operation can be started by the capacitor added in parallel with the diode of the snubber circuit before the voltage applied to the semiconductor switch element exceeds the voltage of the DC circuit at the time of turn-off. Since the period is long, the current change rate of the current flowing through the snubber circuit is reduced, and as a result, the voltage generated by the parasitic inductance of the snubber circuit can be reduced.

[0014]

FIG. 1 is a circuit diagram of a snubber circuit of a semiconductor switch element according to a first embodiment of the present invention. The same elements as those of the conventional example shown in FIG. The reference numerals are attached and the description is omitted. That is, FIG.
, A capacitor 21 as a second capacitor is connected in parallel with the diode 11 to the snubber circuit 20.

The operation of the snubber circuit 20 will be described below with reference to the waveform diagram shown in FIG. The voltage (V _S ) across capacitor 12 of snubber circuit 20 and capacitor 2
The voltage (V _D ) across the IGBT 3 is turned on (V _CE ≒
(0 volts), it is charged by the resistor 13 and has a value substantially equal to the voltage (E) of the DC power supply 1. IGBT
3 starts to turn off, and when the voltage V _{CE of the} IGBT 3 rises slightly from almost 0 volts (see FIG. 2A), the capacitors 12, 2 immediately before turn-off as described above.
Since 1 each voltage is approximately equal (V _S ≒ V _D) state, a current starts I _S of the snubber circuit 20 flows (Fig. 2
(See (c)), the commutation operation described above is started.

[0016] That is, compared to the conventional snubber circuit, faster commutation start timing, resulting commutation period becomes longer, thus the current change rate of the current I _C (see FIG. 2 (b)) and the current The current change rate of I _S (see FIG. 2C) decreases, and the above-mentioned ΔV _P (= L _S · dI _S / d
t, see FIG. 2A) also has a small value. The solid line in the waveform diagram of FIG. 2 corresponds to the characteristic of the first embodiment of the present invention shown in FIG. 1, and the broken line shows the characteristic of the conventional example shown in FIG.

FIG. 3 is a circuit diagram of a snubber circuit of a semiconductor switch device according to a second embodiment of the present invention. Elements having the same functions as those of the snubber circuits shown in FIGS. And description thereof is omitted. That is, in FIG. 3, the IGBT 3 and the IGBT 6 are connected in series at both ends of the DC power supply 1 and supply power to a load from an intermediate connection point between the IGBT 3 and the IGBT 6. One end of the resistor 13 of the DC power supply 1 is connected to the positive electrode side of the DC power supply 1, and one end of the resistor 33 of the snubber circuit 30 of the IGBT 6 is connected to the negative electrode side of the DC power supply 1. The operation of each of the snubber circuits 20 and 30 in this power conversion circuit is the same as in the first embodiment of the present invention.

FIG. 4 is a circuit diagram showing a snubber circuit of a semiconductor switch device according to a third embodiment of the present invention. In FIG. 4, components having the same functions as those of the snubber circuits shown in FIGS. And description thereof is omitted. That is, in FIG. 4, a series circuit of a capacitor 41 as a second capacitor and a resistor 41 is connected in parallel to the diode 11 in the snubber circuit 40.

The capacitor 4 in the snubber circuit 40
1 has the same function as the capacitor 21 shown in FIG.
The resistor 41 suppresses the peak value of the current flowing through the path of the capacitor 12 → the resistor 41 → the capacitor 41 → the parasitic inductance 14 → the IGBT 3 → the capacitor 12 when the IGBT 3 is turned on from the off state, that is, at the time of turn-on. The effect of reducing the noise and preventing electromagnetic noise interference due to the current is provided.

FIG. 5 is a circuit diagram of a snubber circuit of a semiconductor switch device according to a fourth embodiment of the present invention, wherein parts having the same functions as those of the snubber circuits shown in FIGS. And description thereof is omitted. That is, in FIG. 5, the two diodes 51 and 52 and the two capacitors 53 and 54 in the snubber circuit 50 correspond to the diode 11 and the capacitor 21 shown in FIG. 1, respectively. This allows the use of diodes. In this snubber circuit, capacitors 53 and 54 are diodes 51 and 52 connected in series.
Also functions as a voltage divider.

FIG. 6 is a circuit diagram of a snubber circuit of a semiconductor switch device according to a fifth embodiment of the present invention. Elements having the same functions as those of the snubber circuits shown in FIGS. And description thereof is omitted. That is, in FIG. 6, two diodes 61 and 62 and two capacitors 63, 64 and 2 in this snubber circuit 60 are used.
The resistors 65 and 66 correspond to the diode 11, the capacitor 41, and the resistor 42 shown in FIG.

FIG. 7 is a circuit diagram of a snubber circuit of a semiconductor switch device according to a sixth embodiment of the present invention. Elements having the same functions as those of the snubber circuits shown in FIGS. And description thereof is omitted. That is, in FIG. 7, a driving circuit 70 for outputting a driving signal of the IGBT 3 is provided.
And a diode 73. When the signal goes high, the gate of the IGBT 3 is
Since the voltage is applied between the emitters, the voltage between the gate and the emitter rises slowly, and when the signal goes low, the voltage is applied between the gate and the emitter of the IGBT 3 via the diode 72. By lowering, the IGBT 3 is slowly turned on and quickly turned off, so that the peak value of the current flowing through the path of the capacitor 12 → the capacitor 21 → the parasitic inductance 14 → the IGBT 3 → the capacitor 12 at the time of turning on is suppressed. Is a snubber circuit equivalent to the snubber circuit 40 shown in FIG.

[0023]

According to the present invention, when the semiconductor switch element is turned off, the voltage (E + ΔV _P ) applied to the element is turned off.
Therefore, a semiconductor switch element having a low withstand voltage can be used, and as a result, a power conversion circuit having a large capacity can be reduced in size and cost.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a snubber circuit of a semiconductor switch element showing a first embodiment of the present invention;

FIG. 2 is a waveform chart illustrating the operation of FIG.

FIG. 3 is a configuration diagram of a snubber circuit of a semiconductor switch element according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a snubber circuit of a semiconductor switch element showing a third embodiment of the present invention.

FIG. 5 is a configuration diagram of a snubber circuit of a semiconductor switch element showing a fourth embodiment of the present invention.

FIG. 6 is a configuration diagram of a snubber circuit of a semiconductor switch element according to a fifth embodiment of the present invention.

FIG. 7 is a configuration diagram of a snubber circuit of a semiconductor switch element according to a sixth embodiment of the present invention.

FIG. 8 is a configuration diagram of a snubber circuit of a semiconductor switch element showing a conventional example.

9 is a waveform chart illustrating the operation of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... DC power supply, 2 ... Load, 3 ... IGBT, 4 ... Parasitic inductance, 5 ... Reflux diode, 6 ... IGBT, 10
... Snubber circuit, 11 ... Diode, 12 ... Capacitor,
13 resistance, 14 parasitic inductance, 20 snubber circuit, 21 capacitor, 30 snubber circuit, 31 diode, 32 capacitor, 33 resistance, 34 parasitic inductance, 40 snubber circuit, 41 capacitor, 42 ... Resistance, 50 ... Snubber circuit, 51,52 ... Diode, 53,54 ... Capacitor, 60 ... Snubber circuit,
61, 62 ... diode, 63, 64 ... capacitor, 6
5, 66: resistor, 70: drive circuit, 71: signal generator,
72: resistor, 73: diode.

Claims (5)

[Claims] 1. A semiconductor switching element used in a power conversion circuit, comprising: a first diode and a first capacitor between an anode and a cathode terminal, between a collector and an emitter terminal, or between a source and a drain terminal of each semiconductor switching element. A snubber circuit for a semiconductor switch element, wherein a second capacitor connected in parallel to both ends of the first diode is added to a snubber circuit for a semiconductor switch element having a configuration in which a series circuit composed of: 2. A semiconductor switching element for use in a power conversion circuit, comprising: a first diode and a first capacitor between an anode and a cathode terminal, between a collector and an emitter terminal, or between a source and a drain terminal of each semiconductor switching element. A snubber circuit of a semiconductor switch element having a configuration in which a series circuit consisting of: is connected in parallel, wherein a series circuit comprising a second capacitor and a resistor connected in parallel to both ends of the first diode is added. Snubber circuit. 3. A semiconductor switching element used in a power conversion circuit, wherein a plurality of diodes are connected in series between anode and cathode terminals, between collector and emitter terminals, or between source and drain terminals of each semiconductor switching element. A semiconductor switch device having a configuration in which a series circuit including one capacitor is connected in parallel, wherein a second capacitor connected in parallel is added to both ends of each of the plurality of series-connected diodes. Snubber circuit. 4. A semiconductor switching element used in a power conversion circuit, wherein a plurality of diodes are connected in series between anode and cathode terminals, between collector and emitter terminals, or between source and drain terminals of each semiconductor switching element. In a snubber circuit of a semiconductor switch element having a configuration in which a series circuit including one capacitor is connected in parallel, a series circuit including a second capacitor and a resistor connected in parallel to both ends of each of the plurality of series-connected diodes is added. A snubber circuit for a semiconductor switch element. 5. A snubber circuit for a semiconductor switch device according to claim 1, wherein said semiconductor switch device is a self-extinguishing device, and a driving circuit or a driving signal for said self-extinguishing device. The turn-on time of the self-extinguishing device is adjusted to a predetermined value by a snubber circuit of a semiconductor switch element.