JPS59188373A - Snubber circuit for self-extinguishing semiconductor devices - Google Patents

Abstract

PURPOSE:To provide a snubber circuit of a self-extinguishing type semiconductor element adapted for a large capacity without loss by providing a switch element in a circuit for transferring the charge of a snubber capacitor to the second capacitor. CONSTITUTION:A thyristor ThR is provided in series with a reactor LR, and a snubber capacitor of a freewheel diode DF is commonly used as a regenerative capacitor CR. When an ON signal is applied to the thyristor ThR substantially in synchronization with the turn ON of a GTO thyristor, the charge of a snubber capacitor CS is transferred to the capacitor CR, and the thyristor ThR is then turned OFF. When the GTO thyristor is turned OFF, the charge of the capacitor CR is applied to a load, while the capacitor CS is overcharged. When the GTO thyristor is then turned ON, the charge of the capacitor CS is transferred to the capacitor CR.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] The present invention relates to a snubber circuit for a self-extinguishing semiconductor device, and more particularly to a lossless snubber circuit system for reducing loss in the snubber circuit.

[Prior art]

Figure 1 is a diagram showing an example of a lossless snubber circuit for a conventional self-extinguishing semiconductor device (shown here as a gate turn-off thyristor GTO), and Figure 2 is an explanatory diagram of the operation of the circuit in Figure 1. . In Figure 1, a snubber circuit consisting of a series body of a diode Ds and a capacitor Cs is connected in parallel to the GTO thyristor connected in series to the load, and a freewheeling diode Dy and its snubber circuit (resistance Rny and a series body of capacitor CDF) are connected in parallel. Then, from the connection point of the diode Ds, which is the snubber circuit of the GTO thyristor, and the capacitor Cs, the series body of the accelerator LR and the diode DR is connected so that the cathode of the diode DB and the cathode of the freewheeling diode DF are at the same potential. Further, a second capacitor CB is connected between the connection point of the reactor LR and the diode DR and the anode of the freewheeling diode Dy. Note that VB is the power supply voltage,
Ijt indicates wiring inductance.

The operation of this circuit will be explained with reference to the operation explanatory diagram of FIG.

When the GTO thyristor is in the OFF state, the capacitor CsK power supply voltage v8 is charged, but when the GTO thyristor is turned on from this state, the voltage of the capacitor Cs becomes ACDOLE LR → CAPACITOR CR- + GTO thyristor →
The capacitor Cs is discharged in a closed circuit, and the voltage of the capacitor Cs is finally transferred to the second capacitor CR. Then, when the GTO thyristor is turned off, the voltage of capacitor CR is diode DR → load → capacitor C
The capacitor CR is discharged in the closed circuit of R, and due to the turn-off of the GTO thyristor that supplies power to the load, current flows through the capacitor Cs again via the diode Ds, and the rate of voltage increase is reapplied to the GTO thyristor. Almost the power supply voltage Vs' while suppressing it to the required value! : Charged with.

In the conventional circuit shown in FIG. 1 described above, most of the energy stored in the snubber capacitor Cs of the GTO thyristor is supplied to the load via the second capacitor CR, so that the so-called Lossless
It is a snubber circuit.

By the way, when this circuit is used in a large-capacity chopper device or inverter device, the influence of the wiring inductance LL shown in FIG. 1 cannot be ignored, and the following problems occur. That is, in a large-capacity device, the wiring inductance LL is large and the current flowing through it is also large, so when the GTO thyristor is turned off, the snubber capacitor Cs is charged with a voltage higher than the power supply voltage Vs, as shown by the dotted line in Fig. 2. The terminal voltage of the GTO thyristor becomes oscillatory. This vibration occurs because first, the overcharge voltage of the capacitor Cs is discharged in a closed circuit of reactor Ln → diode DR → wiring inductance Lt → power supply voltage V8 → capacitor Cs, and then the wiring inductance Lt accumulated at this time The energy discharge occurs in the closed circuit of diode DF (current in the load circulates and is in a conductive state) → diode Ds → capacitor Cs → power supply voltage VII → wiring inductance LL, thereby charging and discharging capacitor Ca. This occurs due to repeated actions. When diode Da is conducting due to this oscillating current, G
When TOSirisk is turned on, diode DB
The charge in the capacitor Cs is discharged to the GTO thyristor until the voltage blocking ability is recovered and the GTO
Current flows into the thyristor at an excessively high rate of current rise, damaging the GTO thyristor.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and provide a lossless snubber circuit suitable for large-capacity devices.

[Key points of the invention]

A feature of the invention is the provision of a switching element within the circuit that transfers the charge of the snubber capacitor to the second capacitor.

[Embodiments of the invention]

FIG. 3 shows an embodiment of the present invention. In the circuit shown in Figure 3, a thyristor T is connected in series with the axle LR in the conventional circuit shown in Figure 1.
h R is provided, and a freewheel diode Dr
The snubber capacitor CDF is shared with the regeneration capacitor CR. In the circuit of Fig. 3, when an on signal is given to the thyristor Thi almost in synchronization with the turn-on of the GTO thyristor, the negative voltage of the snubber capacitor Cs is transferred to the capacitor Cn, as in the conventional circuit of Fig. 1, and then the thyristor ThR is turned off. be done. When the GTO thyristor is turned off, the voltage across the capacitor CR is applied to the load, while the snubber capacitor C8 is overcharged with a voltage equal to or higher than the power supply voltage 711, similar to the conventional circuit of FIG. However, in the circuit of FIG. 3, this overcharge voltage is blocked by the thyristor ThR and does not discharge, so the first
The defects that occurred in the figure are not only removed, but also the next GTO
The effect is that it is transferred to capacitor CR at turn-on of the thyristor and then supplied to the load at turn-off of the GTO thyristor. That is, the circuit shown in FIG. 1 has the characteristic that the energy stored in the wiring inductance Lt, which was consumed in the wiring resistance of the circuit, can also be supplied to the load.

FIG. 4 shows another embodiment of the invention. In large-capacity devices, the power supply voltage VB is generally high, and the current for recovering the freewheel diode DF when the GTO thyristor is turned on is suppressed only by the wiring inductance LL. If the peak value is large, GTO thyristor or freewheel
There is a risk of damaging the diode Dr. For this reason,
() An anode reactor LA was connected in series with the TO thyristor to suppress the recovery current to a required value. and,
When the GTO thyristor is turned off, the accumulated energy is consumed in a resistor in the circuit shown by the dotted line in FIG. 4 to prevent the overcharge voltage of the snubber capacitor Cs from becoming high.

In the circuit of FIG. 4 according to the invention, the snubber capacitor Cs
Since the overcharge voltage of is prevented from discharging by the thyristor T h n, the overcharge voltage can be increased to the point allowed by the voltage rating of the GTO thyristor, and the effect of supplying this overcharge voltage to the load is be.

That is, the anode reactor has the feature that it can supply the stored energy to the load without consuming it in resistance.

Further, in the circuit shown in FIG. 4, by using the anode reactor LA also as the reactor LR, there is an advantage that the reactor Ln can be omitted.

This is also inconceivable in the conventional circuit shown in FIG. 1, which has an overcharge voltage discharge circuit.

This is because if the reactor La is omitted in FIG. 1, the overcharge voltage will be discharged to the power supply only through the wiring inductance LL, resulting in a drawback that the discharge current will be extremely large.

FIGS. 5 and 6 further show other embodiments of the present invention, each of which is an example of a circuit applied to a single-phase inverter.

Fig. 5: When a beam axle LR (LRI to LR4) is provided, Fig. 6 is a circuit in which the beam axle LR is also used as an anode reactor L (LAI to LM4), and is explained in Figs. 3 to 4. It has the effect of In addition, in an inverter circuit, for example, L-+L A a
→GTO4→Dy2→L person 2→L outside L→LA4
→GT 04→DRI→T h RL-+D 8!
-hLAI→L A bypass circuit can be created, but the provision of the thyristor ThR1 as in the present invention has the effect of preventing this bypass circuit.

〔Effect of the invention〕

As described in detail above, according to the present invention, a lossless snubber circuit suitable for large-capacity chopper devices and inverter devices can be provided, and after the electromagnetic energy of the wiring inductance and anode reactor is stored in the capacitor, It has the effect of supplying power to the load.

[Brief explanation of the drawing]

Figure 1 is a conventional lossless snubber circuit, Figure 2 is an explanatory diagram of the operation of Figure 1, Figures 3 to 6 are lossless snubber circuits of the present invention, and Figures 3 to 4 are chopper circuits. Figures 5 and 6 are examples of circuits applied to inverter circuits. L...load, GTO...gate turn-off thyristor, Cs, Ca, Cnr-capacitor, DIl,
DR. Dy...diode, Lt...wiring inductance, LA', LR...reactor, ThR...thyristor. E 1st [21 2nd, l”. turn on Targio) 3rd curse 4n

Claims (1)

[Claims] 1. A series body of a diode and a first capacitor connected in parallel to a self-arc-extinguishing semiconductor element, circuit means for transferring the electric charge of the first capacitor to a second capacitor via a reactor when the semiconductor element is turned on; In a snubber circuit for a self-extinguishing semiconductor device, the circuit includes circuit means for supplying the charge of the second capacitor to the load when the semiconductor device is turned off, and the circuit transfers the charge of the first capacitor to the second capacitor. A snubber circuit of a self-extinguishing semiconductor element, characterized by having a switch element provided therein.