JPH0652985B2 - Gate circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] In a gate circuit of a self-extinguishing thyristor such as a gate turn-off thyristor or an electrostatic induction thyristor (hereinafter referred to as STY), the energy of a snubber capacitor is converted to a negative direction gate current. The present invention relates to an improvement of a regenerative DC power supply for supplying a power source, and is expected to be particularly effective in a high frequency application field requiring a large capacity DC power source.

[Conventional technology]

As an example of the technique for regenerating the energy of the snubber capacitor to the power source of the gate circuit, there is JP-A-60-49665, which was previously announced by the present inventor. This relates not only to the negative direction gate current power supply but also to the system used as the positive direction gate current power supply. However, in the present invention, since it is not directly related to the positive direction gate current power supply, the negative direction gate current power supply is used. Fig. 2 shows only the part related to the current power supply.

In FIG. 2, reference numeral 1 is a self-extinguishing thyristor, which is shown here as an example of SITY. 2 is a snubber capacitor,
3 is a diode, 4 is a DC power supply for supplying a negative direction gate current, 5 is a switching element, and 6 is a reactor.

When the SITY ₁ is extinguished, the switching element 5 is closed to supply the negative direction gate current from the DC power supply 4. When SITY ₁ is extinguished, the voltage between the anode and the cathode generally rises, the snubber capacitor 2 is charged through the diode 3, and the normal snubber operation is performed.

SIYT supplies positive gate current from a circuit not shown in the point at the arc of _1, between the anode-cathode when Sity ₁ ignites becomes conductive, small order 2~3V also the anode-cathode voltage It becomes a value. Then, the electric charge charged in the snubber capacitor 2 when extinguishing the cathode → DC power source 4 of the anode → Sity ₁ capacitor 2 → Sity ₁
→ Reactor 6 → Discharged along the path of the capacitor 2 to charge the DC power supply 4 and converted into electromagnetic energy of the reactor 6.

After the voltage of the capacitor 2 becomes almost zero volt, a current circulates in the path of the reactor 6, the diode 3, the DC power supply 4, and the reactor 6, and the electromagnetic energy of the reactor 6 is transferred to the DC power supply 4. After all, the electric charge stored in the snubber capacitor 2 is almost regenerated to the DC power supply 4. Therefore, a small capacity DC power supply 4 can be used, which is an effective gate circuit in terms of economy and space saving.

[Problems to be solved by the invention]

However, in the gate circuit shown in FIG. 2, the following inconvenience may occur. That is, the energy W _R regenerated by the DC power supply 4 is the snubber capacitor 2
Capacity C _S , anode-cathode voltage V of SITY ₁ when off
It is almost determined by the operating frequency of _A and SITY ₁ , and is approximately as follows.

On the other hand, the energy W _P of the DC power source 4 that is consumed by the negative gate current of Sity ₁ is off-gate charge of Sity ₁
When the voltage of Q _GQ and the DC power supply 4 is V _N , it is roughly expressed by W _P = Q _GQ V _N (W) ……… (2).

(1) of the anode-cathode voltage V _A, the operating frequency is Sadamari the requirements on the main circuit, the snubber capacitor 2 capacitor C _S
Is also selected according to the overvoltage and dv / dt tolerance of SITY ₁ , so the regenerative energy W _R is naturally determined.

On the other hand, the energy consumption W _P depends on the off-gate charge Q _GQ, which varies depending on the anode current value, the junction temperature, the gate drive method, etc. and is not constant.

For the DC power supply 4, it is desirable that the energy consumption W _P is always slightly larger than the regenerative energy W _R and only the shortage is supplied from the outside, but this condition is always satisfied because of fluctuations in the off-gate charge Q _GQ. Not always possible,
Occasionally, the regenerative energy W _R may exceed the consumed energy W _P.

In such a case, the capacitor inside the DC power supply 4 is charged with the regenerative energy to cause an overvoltage state, which impairs the gate reverse breakdown voltage of SITY _{1 and} the breakdown voltage of the switching element 5 [Means for solving the problem] In view of the above points, the invention is such that when the energy W _R regenerated by the DC power source exceeds the energy W _{P of the} DC power source consumed by the negative direction gate current and the voltage of the DC power source starts to rise, A regenerative current bypass circuit is provided to stop the regenerative operation.

That is, a series connection body of a first diode and a capacitor whose cathode is connected to the cathode of the self-extinguishing thyristor is connected between the anode and the cathode of the self-extinguishing thyristor, and the anode is the cathode of the self-extinguishing thyristor. A series connection body of a DC power source and a first switching element connected to is connected between the gate and the cathode of the self-extinguishing thyristor, and an anode of a second diode and a reactor connected to the cathode of the DC power source. If the series connection is connected between the cathode of the DC power supply and the anode of the first diode, and the second switching element is connected between the cathode of the self-extinguishing thyristor and the cathode of the second diode, the DC power supply voltage A detection circuit is provided so that the second switching element is closed when the DC power supply voltage exceeds a predetermined value.

〔Example〕

FIG. 1 is a connection diagram showing an embodiment of a gate circuit according to the present invention. The same reference numerals as those in FIG. 2 denote the same parts, 7 is a diode, 8 is a voltage detection circuit, and 9 is a switching element.

Next, the operation of the circuit shown in FIG. 1 will be described. When the voltage of the DC power supply 4 is within the normal range, the voltage detection circuit 8 gives an OFF command to the switching element 9 to open the circuit, and the diode 7 is inserted in series with the reactor 6 and the second
It operates in exactly the same way as the circuit shown.

When the voltage of the DC power supply 4 exceeds a predetermined value, the voltage detection circuit 8 detects this and closes the switching element 9.
Then, the electric charge of the snubber capacitor 2 is through discharge cathode → path of the switching device 9 → the reactor 6 → capacitor 2 in the anode → Sity ₁ capacitor 2 → Sity _1, after the voltage of the capacitor 2 becomes substantially zero Since a current flows through the path of reactor 6 → diode 3 → switching element 9 → reactor 6, regeneration to DC power supply 4 is stopped. The diode 7 is necessary to prevent the DC power supply 4 from being short-circuited when the switching element 9 is closed.

When the voltage of the DC power supply 4 falls below the normal range, the switching element 9 is opened again to restart the regenerative operation.
In order to perform a stable operation as described above, the voltage detection circuit 8 has a hysteresis characteristic.

[Action]

As described above, when the voltage of the DC power supply 4 is above the normal range, the voltage detection circuit 8 detects this and closes the switching element 9 to stop the regenerative operation, and the voltage of the DC power supply 4 falls below the normal range. Then, the switching element 9 is controlled to be opened to start the regenerative operation, and the voltage of the DC power supply 4 is maintained within the normal range.

Therefore, the voltage of the DC power supply 4 becomes an overvoltage state and the SITY ₁
It is possible to avoid a situation in which the withstand voltage of the switching element 5 is impaired, or the voltage of the DC power supply 4 is abnormally lowered to prevent normal arc extinguishing operation.

〔The invention's effect〕

As described in detail above, according to the present invention, in the gate circuit that regenerates the snubber energy to the gate circuit power supply, the regeneration amount is controlled by adding a simple circuit to prevent the gate circuit power supply from becoming abnormal. Therefore, it is possible to contribute to the realization of a gate circuit of a self-turn-off thyristor using a small capacity DC power supply.

[Brief description of drawings]

FIG. 1 is a connection diagram showing an embodiment of a gate circuit according to the present invention, and FIG. 2 is a connection diagram showing an example of a conventional gate circuit for performing snubber energy regeneration. 1 ... Electrostatic induction thyristor, 2 ... Capacitor, 3, 7
...... Diode, 4 ...... DC power supply, 5, 9 ...... Switching element, 6 ...... Reactor, 8 ...... Voltage detection circuit.

Claims (1)

[Claims] 1. A self-extinguishing thyristor having a first diode connected to a cathode of a self-extinguishing thyristor in series connection with a capacitor is connected between an anode and a cathode of the self-extinguishing thyristor, and an anode of the self-extinguishing thyristor. A series connection body of a DC power source connected to the cathode of the thyristor and the first switching element is connected between the gate and the cathode of the self-extinguishing thyristor, and an anode of the second diode connected to the cathode of the DC power source. The series connection with the reactor is connected between the cathode of the DC power supply and the anode of the first diode, and the second switching element is connected between the cathode of the self-extinguishing thyristor and the cathode of the second diode, and the DC Self-extinguishing, characterized in that a power supply voltage detection circuit is provided to close the second switching element when the DC power supply voltage exceeds a predetermined value. Gate circuit of the form thyristor.