JPH11136928A - Snubber circuit of semiconductor switching device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the snubber circuit of a semiconductor switching device, by which the rising rate of a device current can be suppressed and hindrances due to the increase in the rising rate of the device current can be avoided. SOLUTION: A snubber circuit has a series circuit which consists of a diode 11 and a capacitor 13 and is connected in parallel to a semiconductor switching device 1 inserted in a main circuit, a series circuit which consists of a snubber reactor 12 and the primary winding 21 of a saturable reactor 14 and is connected in parallel to the diode 11 and a current source 23, which is connected to the secondary winding 22 of the saturable reactor 14. When the semiconductor switching device 1 is turned on, the rise in the discharge current of the capacitor 13 is delayed by the saturable characteristics of the saturable reactor 14, which is magnetically saturated in a predetermined direction beforehand by the current source 23. After the saturable reactor 14 has been magnetically saturated in a reverse direction and the capacitor 13 has been discharged, the saturable reactor 14 is saturated magnetically in the predetermined direction again by the current source 23.

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 switching element used for an inverter and other power conversion devices.

[0002]

2. Description of the Related Art FIGS. 2A and 2B are diagrams showing a snubber circuit of a semiconductor switching element according to a conventional example. FIG. 2A is a diagram showing a circuit configuration of the snubber circuit, and FIG. 2B is an operation waveform of each part of the circuit shown in FIG. FIG. FIG. 2A is a diagram showing an example of a snubber circuit of a semiconductor switching element which has been widely known from the prior art, wherein 1 is a semiconductor switching element inserted in a main circuit, 2 is a main circuit voltage source, 3 Is a main circuit resistance, 4 is a main circuit inductance, and 10 'is a snubber circuit.

[0003] The snubber circuit 10 'is a circuit in which a parallel circuit of a diode 11 and a snubber resistor 12 and a snubber capacitor 13 are connected in series, and is connected in parallel to the semiconductor switching element 1.

FIG. 2 (b) is a diagram showing operation waveforms of respective parts of the circuit shown in FIG. 2 (a). As shown in FIG. 2B, during a period T1 during which the semiconductor switching element 1 is on, a main circuit current Im flows through the element 1.

When the semiconductor switching element 1 performs a turn-off operation in the period T2, the element current Ie decreases as shown by a broken line in the figure. At this time, the main circuit current Im is commutated to the series circuit of the diode 11 and the capacitor 13, and the energy stored in the inductance 4 of the main circuit is absorbed by the snubber capacitor 13. As a result, a surge voltage and a voltage increase rate generated at both ends of the semiconductor switching element 1 are suppressed. During the period T3 in which the semiconductor switching element 1 is in the off state, the snubber capacitor 13 is charged to a predetermined voltage level by the main circuit voltage source 2.

When the semiconductor switching element 1 is turned on during the period T4, the voltage Ve across the semiconductor switching element 1 drops sharply. At the same time, the main circuit current Im and the discharge current Isr of the snubber capacitor 13 start flowing into the semiconductor switching element 1.

Here, focusing on the capacitance of the snubber capacitor 13, the greater the capacitance is, the greater the effect of suppressing the surge voltage and the rate of voltage increase at both ends of the semiconductor switching element 1. However, the discharge current Isr increases accordingly.

The charge of the snubber capacitor 13 that has been charged when the semiconductor switching element 1 is turned off must be discharged between the time when the semiconductor switching element 1 is turned on and the time when the semiconductor switching element 1 is turned off next time. Therefore, it is necessary to discharge the charged electric charges relatively quickly. For this reason, the resistance value of the snubber resistor 12 is usually set to a relatively small value so that a relatively small discharge time constant is obtained. When the resistance value of the snubber resistor 12 is reduced, the peak value of the snubber discharge current Isr at the time of turn-on increases. Then, if the inductances of the discharge paths are the same, the current increase rate of the snubber discharge current Isr increases and the current increase rate of the element current Ie increases by an amount corresponding to the increase in the peak value.

If the rate of rise of the device current Ie at the time of turn-on is large, the turn-on loss, which is the time integral value of the product of the device voltage Ve and the device current Ie, increases. If the rise rate of the device current Ie exceeds the upper limit of the current rise rate at the time of turn-on specified for the semiconductor switching device 1, the device 1 may be broken.

[0010]

As described above, in the conventional snubber circuit 10 'of the semiconductor switching device 1,
When the semiconductor switching element 1 is turned on, the main circuit current, Im, and the discharge current Isr of the snubber capacitor 13 flow into the semiconductor switching element 1 at the same time. If the capacitance of the snubber capacitor 13 is increased, or if the value of the snubber resistor 12 is decreased in order to quickly discharge the charge of the snubber capacitor 13, the current rise rate of the element current Ie increases, and the turn-on loss increases. There was a disadvantage that the problem described above occurred.

An object of the present invention is to provide a snubber circuit of a semiconductor switching element which can suppress the rate of increase of the element current when the semiconductor switching element is turned on and can avoid the adverse effects caused by the increase of the rate of increase of the element current. It is in.

[0012]

In order to solve the above problems and achieve the object, a snubber circuit of a semiconductor switching device according to the present invention is configured as follows. The snubber circuit of the semiconductor switching element of the present invention includes a series circuit of a diode and a capacitor connected in parallel with the semiconductor switching element inserted in the main circuit, a snubber resistor connected in parallel with the diode in the series circuit, and A series circuit of a saturable reactor, wherein when the semiconductor switching element is turned on, the rise of the discharge current of the capacitor is delayed by the saturable characteristic of the saturable reactor.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment [Configuration] FIG. 1 is a diagram illustrating a snubber circuit of a semiconductor switching element according to a first embodiment, (a) is a diagram illustrating a circuit configuration of a snubber circuit, and (b) is a diagram (a). FIG. 5 is a diagram showing operation waveforms of respective parts of the circuit shown in FIG.

As shown in FIG. 1A, a semiconductor switching element 1 is connected to a main circuit voltage source 2 via a main circuit resistor 3 and a main circuit inductance 4 in series. A so-called snubber circuit 10 enclosed by a two-dot chain line is connected to the semiconductor switching element 1 in parallel.

The snubber circuit 10 includes a diode 11 and a capacitor 13 connected in series.
In addition, a series circuit of a snubber resistor 12 and a saturable reactor (saturable coil) 14 is connected in parallel.

The saturable reactor 14 has a primary winding 21 and a secondary winding 22 wound around an annular core material 20 having a saturable characteristic, and the primary winding 21 is connected to the snubber resistor 12.
And the secondary winding 22 is connected to a current source 23 for supplying a current for core material magnetic flux saturation.

By passing the output current from the current source 23 through the secondary winding 22 of the saturable reactor 14, the core member 20 is magnetically saturated in a predetermined direction by the generated magnetic field. The direction of the magnetic saturation is a direction for canceling the magnetic field generated in the core member 20 by the discharge current Isr of the snubber capacitor 13 flowing through the primary winding 21 when the semiconductor switching element 1 is turned on.

[Operation] FIG. 1B is a diagram showing operation waveforms of various parts of the circuit shown in FIG. 1A. As shown in FIG. 1B, during a period T1 during which the semiconductor switching element 1 is on, a main circuit current Im flows through the element 1.

When the semiconductor switching element 1 is turned off in the period T2, the element current Ie decreases as shown by the broken line in the figure. At this time, the main circuit current Im is commutated to the series circuit of the diode 11 and the capacitor 13, and the energy stored in the inductance 4 of the main circuit is absorbed by the snubber capacitor 13. As a result, a surge voltage and a voltage increase rate generated at both ends of the semiconductor switching element 1 are suppressed.

During the period T3 in which the semiconductor switching element 1 is in the off state, the snubber capacitor 13 is charged to a predetermined voltage level by the main circuit voltage source 2. When the semiconductor switching element 1 is turned on during the period T4, the voltage across the semiconductor switching element 1 drops sharply. At the same time, the main circuit current Im and the discharge current Isr of the snubber capacitor 13
Begin to flow into.

[Operation and Effect] Snubber circuit 1 of the present embodiment
0, when the discharge current Isr of the snubber capacitor 13 flows through the primary winding 21 of the saturable reactor 14, the core material 20 of the saturable reactor 14 is magnetically saturated in a predetermined direction in advance. -H characteristic
The discharge current Isr of the snubber capacitor 13 causes the core material 20 to delay the rise of the discharge current Isr only during a period of high magnetic permeability until the core material 20 is magnetically saturated in the reverse direction.

That is, as shown in FIG. 1B, the rise of the discharge current Isr is larger than that in the case where the saturable reactor 14 is not present (the case shown by the broken line A = corresponding to the conventional example).
The characteristic curve B has a phase delayed by the delay time DT.

When the core member 20 is magnetically saturated in the reverse direction, a discharge current Isr flows and the electric charge of the snubber capacitor 13 is discharged. After that, the core material 20 of the saturable reactor 14 is
Due to the output current of the current source 23, magnetic saturation occurs again in a predetermined direction until the next turn-on.

The turn-on loss is reduced by setting the rise delay time DT of the discharge current Isr of the snubber capacitor 13 to 1 to 2 μs until the voltage Ve across the semiconductor switching element 1 drops from the OFF voltage to the steady ON voltage. You.

(Modification) The snubber circuit of the semiconductor switching element shown in the embodiment includes the following modifications.

A material using a non-annular core material as the core material 20. The one using a variable capacitor as the snubber capacitor 13. The one using a variable resistor as the snubber resistor 12.

[0027]

According to the present invention, the rise of the snubber discharge current is delayed by the saturable reactor connected in series with the snubber resistor, the phase of the snubber discharge current is shifted, and as a result, the snubber discharge current is reduced. For example, the capacitance of the snubber capacitor is increased to increase the surge voltage at both ends of the semiconductor switching element and the effect of suppressing the voltage rise rate, and the snubber is discharged to quickly discharge the charge of the snubber capacitor. Even if the resistance value is reduced, the rate of rise of the element current can be suppressed, and a snubber circuit of a semiconductor switching element that can avoid the adverse effects caused by the increase of the rate of rise of the element current can be provided.

[Brief description of the drawings]

FIGS. 1A and 1B are diagrams showing a snubber circuit of a semiconductor switching element according to a first embodiment of the present invention, in which FIG. 1A shows a circuit configuration of a snubber circuit, and FIG. 1B shows each part of the circuit shown in FIG. The figure which shows an operation waveform.

2A and 2B are diagrams illustrating a snubber circuit of a semiconductor switching element according to a conventional example, in which FIG. 2A illustrates a circuit configuration of a snubber circuit, and FIG. 2B illustrates operation waveforms of respective parts of the circuit illustrated in FIG. .

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Semiconductor switching element 2 ... Main circuit voltage source 3 ... Main circuit resistance 4 ... Main circuit inductance 10 '... Snubber circuit 11 ... Snubber diode 12 ... Snubber resistance 13 ... Snubber capacitor 14 ... Saturable reactor (saturable coil) 20 ... Annular core material 21: primary winding 22: secondary winding 23: current source

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[Procedure amendment]

[Submission date] April 10, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction contents]

[0012]

In order to solve the above problems and achieve the object, a snubber circuit of a semiconductor switching device according to the present invention is configured as follows. The snubber circuit of the semiconductor switching element of the present invention includes a series circuit of a diode and a capacitor connected in parallel with the semiconductor switching element interposed in the main circuit, and a snubber resistor connected in parallel with the diode in the series circuit. And saturable
A series circuit with the primary winding of the reactor, and the saturable reactor;
; And a current source connected to the secondary winding of the torque, when the semiconductor switching element is turned on, in advance the
Due to the saturable characteristics of the saturable reactor magnetically saturated in a predetermined direction by a current source, the rise of the discharge current of the capacitor is delayed, and the saturable reactor moves in the opposite direction.
After the capacitor is discharged due to magnetic saturation, the semiconductor
Until the switching element turns on next time,
The current source causes the saturable reactor to return to a predetermined
It is characterized in that it is configured so as to magnetically saturate in the direction .

Claims (1)

[Claims] 1. A series circuit of a diode and a capacitor connected in parallel with a semiconductor switching element inserted in a main circuit, and a series circuit of a snubber resistor and a saturable reactor connected in parallel with the diode in the series circuit. A saturable characteristic of the saturable reactor that delays a rise of a discharge current of the capacitor when the semiconductor switching element is turned on.