JPS6057720A - Snubber circuit device of electrostatic induction thyristor - Google Patents

Abstract

PURPOSE:To decrease the power loss of a snubber resistor by connecting one end of an impedance element to a connecting point of a series connection between a diode and a capacitor and connecting the other end of the impedance element to a DC power supply. CONSTITUTION:The series connection comprising the snubber diode 5' and the snubber capacitor 6' is connected in parallel with an electrostatic thyristor 8. One end of the snubber resistor 7' being the impedance element is connected to the connecting point between the snubber diode 5' and the snubber capacitor 6' and the other end of the snubber resistor 7' is connected to the DC power supply E. Through the constitution above, even if the capacitor capacitance is selected largely in order to lower the overcharge voltage of the snubber capacitor 6' when the electrostatic thyristor 8 is turned off, no hindrance is given to the power loss at turn-off.

Description

[Detailed Description of the Invention] The present invention is silent! This article relates to a DC switch circuit using an induction thyristor, and in particular to the improvement of a special snubber circuit device that is suitable and effective for electrostatic induction thyristors. ) is one type of self-extinguishing thyristor that has the same self-extinguishing function as the GTO thyristor, but it is attracting attention as having various advantages compared to the GTO thyristor ◎ Namely, (1) Fast switching speed .

(2) Hard to cause thermal damage during turn-off.

(3) Forward voltage rise rate immediately after turn-off (dV/dt
) has a large tolerance.

On the other hand, one typical snubber circuit device shown in FIG. 1 is known.

Figure 1 shows the main part configuration of an example of a DC switch circuit using a GTO thyristor and equipped with a known snubber circuit device, where l is a DC power supply, 2 is a GTO thyristor, 3 is a load, and 4 is a main circuit floating It is inductance. In addition, in the figure, 5 is a snubber diode, 6 is a snubber capacitor, and 7 is a snubber diode.
is the snubber resistance.

Furthermore, FIGS. 2 and 3 are explanatory diagrams showing the waveforms of each part when the DC switch circuit shown in FIG. 1 is turned off and turned on. The snubber circuit operates as follows.

First, the anode current IT (!near-node voltage VA
In Figure 2, which shows the time course of K, the current time TO
Assuming that an off-gate pulse is given to the GTO thyristor 2 at F, the fall time T after the accumulation time Ts has elapsed.

During this period, most of the anode current I attenuates and the remaining current disappears after the tail period TT.
Changes in the anode voltage TAX of the TO thyristor 2 are as shown in the example. ◇ The functions of the snubber capacitor 6 in such an operation are as follows. The first point is to reduce the power loss during the tail period TT immediately after turn-off. Anode voltage YAK
The second point is to limit the rate of increase in the anode voltage VXX to prevent false firing of the GTO thyristor 2 immediately after turn-off, and the third point is to suppress and reduce the inductance component of the main circuit. The purpose is to suppress the spike voltage ΔvO occurring in one anode voltage vAK by absorbing the stored energy.

Next, changes in the anode current IT and the voltage vO of the snubber capacitor 6 when the GTO thyristor 2 is turned on are as shown in FIG.

Here, s ITP indicates the peak value of the anode current IT. That is, time TOt! When turning on the snubber capacitor 6, the charge stored in the snubber capacitor 6 is discharged through the snubber resistor 7, and the energy is consumed as heat.At this time, the power wR applied to the snubber resistor 7I is If the capacity of 6 is aSV and the operating frequency is F, then WR = (1/2)・C5(E
s) ζF ・−=−=・−・0 This can be expressed by the relational expression (1), so the heat generation of the snubber resistor 7 increases significantly as the circuit voltage and operating frequency increase. In the DC switch circuit, now GTO
If an 8I thyristor is used instead of a thyristor, it is difficult to thermally break down during turn-off as described above and has a large (dV/dt) withstand capacity. It should be possible to reduce this. However, the circuit configuration shown in Figure 1 requires $
Simply replacing the GTO thyristor 2 with an 8I thyristor will greatly affect the overcharge voltage of the snubber capacitor caused by the energy stored in the main circuit stray inductance 4 when the thyristor is cut off. ΔVO is 1vo-T-τ=station■, assuming that the value of main circuit stray inductance 4 is L3.
). However, the anode current IT is the value at the time of shutoff. Therefore, the capacitance iC of the snubber capacitor 6
If 8 is made small, the spike voltage ΔvO becomes extremely large (and therefore exceeds the allowable forward voltage of the 3N thyristor, which causes a problem). The present invention will be explained below with reference to the drawings.
Figure 4 shows the main structure of an embodiment of the present invention, and Figure 5'
is a snubber diode, 6' is a snubber capacitor, 7' is a snubber resistor as an example of an impedance element, and 8 is an 8I thyristor. , 8I thyristor snubber circuit component Cζ is compared with FIG. 1, the snubber resistor 7'
is disposed between the positive electrode of the DC power source 1 and the connection point between the two series-connected bodies consisting of the snubber diode 51 and the snubber capacitor 6'. The time course of the waveforms of each part of this configuration is shown in Figures 2 and 9.
The details will be explained below with reference to FIGS. 5 and 6, which are similar to FIG. J3.

Here, Figure tJ5 shows the waveforms of the anode current 1' and anode voltage VAK' during the OFF operation in the circuit of Figure 4, and furthermore, Figure 6 shows the waveforms of the anode current IT during the ON operation.
' and the voltage vO' of the snubber capacitor 6' ◇ That is, when an off-gate pulse is applied to the 8I thyristor 8 at time TOF, most of the anode current T' is is attenuated and the remaining current disappears after the tail period TT. Therefore, although this change is similar to the anode current IT shown in FIG. 2, the anode voltage VAK e VAK' characteristics are significantly different. This is due to the snubber resistor 7' in which the snubber capacitor 6' is connected to the DC power supply 1 as shown in the figure, so that the snubber capacitor 6' always maintains the DC power supply 1 voltage E during the conduction period of the 8I thyristor 8.

Therefore, the anode voltage VAK' becomes equal to or higher than the power supply voltage value immediately after the fall period ends. Incidentally, the spike voltage Δvo' at this time is generated in the inductance component of the above-mentioned main circuit and is given by equation (2). Furthermore, when the SI thyristor 8 is turned on at time TON, the anode current IT' increases as shown, and the snubber resistor 7' has no connection to discharge the charge stored in the snubber capacitor 6'. No power loss occurs.

As described above, this embodiment allows the SI thyristor 8 to fully demonstrate its performance, does not generate power loss in the impedance element part of the snubber circuit, and allows selection of a high circuit voltage and operating frequency. This is a snubber circuit device that is ideal for the DC switch circuit used. Furthermore, to illustrate this point more physically,
The SI thyristor is thermally destroyed and "4 << (dV/dt
) Because of its large withstand capacity, it can withstand a sudden increase in anode voltage immediately after turn-off, and even if the capacitance of the snubber capacitor is chosen to be large in order to lower the overcharge voltage of the snubber capacitor when the 8I thyristor turns off, there will be no problem with power loss at turn-on. It can be assumed that there is no such thing.

FIG. 7 shows the main structure of another embodiment of the present invention.
5" is a snubber diode, 6" is a snubber capacitor, 7
' is a snubber resistor, and 8' is an 8I thyristor. That is, what is shown in FIG. 7 is the example of the DC switch circuit shown in FIG. On the other hand, this is an example in which the SI thyristor 8' is placed on the positive potential side of the load 3.

It is clear that the snubber circuit configuration consisting of the snubber diode 5', the snubber capacitor 6' and the snubber resistor 7' is also the same as that shown in FIG.
The device shown in the figure has the same performance as the device shown in FIG. 4. Figure 8 shows a modified example of the device shown in FIG.
The same reference numerals as those in the figures and FIG. 4 indicate the same components. That is, as shown in FIG. 8, therefore,
It is clear that this example also provides the same effect as the device shown in FIG. 4.

As explained above, according to the present invention, a useful and special equipment ε can be provided for a DC switch circuit employing an S thyristor◇

[Brief explanation of the drawing]

Figure 1, Figures 21 and 3 are circuit diagrams showing an example of a DC switch circuit employing a GTO thyristor equipped with a known snubber circuit device, and explanatory diagrams showing time transitions of the waveforms of each part, respectively. FIG. 6 is a circuit diagram showing one embodiment of the present invention and an explanatory diagram showing the time transition of waveforms of each part thereof, FIG. 7 is a circuit diagram showing another embodiment of the present invention, and FIG.
This figure is a circuit diagram showing a modified example of the apparatus shown in FIG. 3...Load, 4...Main circuit floating inductance, Snap 1 <5.5',5"...B71 ode, 6, 6', 6"
...Snubber capacitor? , 7', 7'...
・Snubber resistor, 81B1.8N...Static induction thyristor (SI Thyrisk) 0 Patent applicant Atsushi Doi, Representative of Toyo Denki Manufacturing Co., Ltd.

Claims (1)

[Claims] In a DC switch circuit comprising at least a DC power supply, a load, and an electrostatic induction thyristor, a series connection body in which a capacitor is connected in series with a diode is connected in parallel to the electrostatic induction thyristor, and a connection point between the diode and the capacitor is connected in parallel to the electrostatic induction thyristor. A snubber circuit for an electrostatic induction thyristor, characterized in that one end of an impedance element is connected to the capacitor, and the other end of the impedance element is connected to the DC power supply so as to charge the capacitor during the conduction period of the electrostatic induction thyristor. Device.