JPS6292766A - Overvoltage emergency ignition circuit for gate turn-off thyristor - Google Patents

Abstract

PURPOSE:To exactly turn a gate turn-OFF thyristor (GTO) ON, by amplifying the anode current of a breakover diode with the detected overvoltage of the GTO, with a high speed thyristor, to be gate current. CONSTITUTION:The overvoltage emergency ignition circuit of a GTO5 is organized by connecting the series circuit of a resistance 2, a breakover diode 3, and a Zener diode 4, between the anode and gate, via a space between the gate and cathode of a high speed thyristor 6. The anode of the thyristor 6 is connected to an ignition power source via a resistance 7, and is fed via a condenser 8 through voltage dividers 9, 10 GTO5 is detected by the diode 3, and the anode current is amplified as the gate current of the high speed thyristor 6, and the current is used for the gate current of the GTO5, and the GTO5 is exactly turned ON.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an overvoltage emergency ignition circuit for a thyristor using a breakover diode.

[Conventional technology and its problems]

Conventionally, as this type of thyristor overvoltage emergency ignition circuit used in thyristor valves, etc., a series circuit of a resistor 2, a breakover diode 3, and a Zener diode 4 is connected between the gate and anode of a thyristor 1, as shown in FIG. It is known that an overvoltage of the thyristor 1 is detected by a breakover diode 3, and the current when the diode 3 is turned on is limited by a resistor 2 and a Zener diode 4 and used as the gate current of the thyristor 1.

However, when the thyristor is not a normal one and a gate turn-off thyristor (hereinafter referred to as a GTO thyristor) is used, the gate firing current required to turn on the GTO thyristor is higher than that of a normal thyristor of the same capacity. Since a device several to several tens of times larger than this is required, there is no breakover diode that can flow an anode current greater than this gate firing current, and there is a drawback that the GTO thyristor cannot be fired directly with a breakover diode. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide an overvoltage emergency ignition circuit which eliminates the disadvantages of the conventional example and can reliably ignite a GTO thyristor even when a breakover diode is used.

[Means for solving problems]

In order to achieve the above object, the present invention provides an overvoltage emergency ignition circuit in which a breakover diode is connected between the gate and anode of a gate turn-off thyristor to detect the overvoltage of the thyristor. and the cathode of the high-speed thyristor is connected to the gate of a gate turn-off thyristor, and the anode of the high-speed thyristor is connected to a voltage dividing resistor for making its withstand voltage smaller than the withstand voltage of the gate turn-off thyristor. It is.

[Operation] According to the present invention, the overvoltage of the GT○ thyristor is detected by the breakover diode, and the anode current of the breakover diode is used as the gate current of the high-speed thyristor, which has a sufficiently small capacity compared to the GTO thyristor, and the current is amplified. The anode current of this high-speed thyristor is used as the gate current of the GTO thyristor to reliably turn on the GTO thyristor, and the withstand voltage of this high-speed thyristor is made smaller than that of the CTO thyristor by using a voltage dividing resistor.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a circuit diagram showing a first embodiment of an overvoltage emergency ignition circuit for a gate turn-off thyristor according to the present invention.
It is a TO thyristor. A resistor 2 and a breakover diode 3 are connected between the anode and gate of the GTO thyristor 5.
A series circuit consisting of a Zener diode 4 and a Zener diode 4 is connected between the gate and cathode of a high-speed thyristor 6.

Further, the anode of the high-speed thyristor 6 is connected to an ignition power source via a resistor 7. This ignition power source is composed of a voltage divider consisting of a resistor 9.10 connected between the anode and cathode of the GTo thyristor 5 and a capacitor 8.

Next, to explain the operation, the anode current of the breakover diode 3 that detects the overvoltage of the GTO thyristor 5 is limited by the resistor 2 and the Zener diode 4, and the gate current of the high-speed thyristor 6, which has a low voltage and small capacity with respect to the GTO thyristor 5, is limited by the resistor 2 and the Zener diode 4. This gate current turns on the high-speed thyristor 6. When the high-speed thyristor 6 turns on, its current amplification action discharges the electric charge in the capacitor 8 that has been charged by the voltage division of the resistors 9 and 10 to the gate of the GTO thyristor 5 through the resistor 7, turning on the GTO thyristor 5. let

On the other hand, the breakdown voltage of the high-speed thyristor 6 is as follows: resistance 9 and resistance 1
By appropriately selecting the partial pressure ratio of 0, the voltage can be made sufficiently smaller than the withstand voltage of the GTo thyristor 5.

FIG. 2 is a circuit diagram showing a second embodiment of the present invention, in which a diode 11 is connected in series with a resistor 9 in addition to the circuit shown in FIG. As a result, the electric charge once charged in the capacitor 8 is
Even if the anode voltage of the GTO thyristor 5 falls below the charging voltage of the capacitor 8, it will not be discharged, resulting in more stable circuit operation.

〔Effect of the invention〕

As described above, the overvoltage emergency ignition circuit for a gate turn-off thyristor of the present invention converts the anode current of the breakover diode that detects the overvoltage of the gate turn-off thyristor into the gate current of a high-speed thyristor having a sufficiently small capacity for the gate turn-off thyristor. Since the current amplified anode current of this high-speed thyristor is used as the gate current of the gate turn-off thyristor, the gate turn-off thyristor can be turned on reliably, and the withstand voltage of this high-speed thyristor can be reduced by using a voltage dividing resistor. This can be made sufficiently smaller than the withstand voltage of the gate turn-off thyristor.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing a first embodiment of an overvoltage emergency ignition circuit for a gate turn-off thyristor according to the present invention, Fig. 2 is a circuit diagram showing a second embodiment of the same, and Fig. 3 is a circuit diagram showing a conventional example. It is. 1...Thyristor 2...Resistor 3...Breakover diode 4...Zener diode 5...GT○thyristor

Claims (1)

[Claims] In an overvoltage emergency ignition circuit that connects a breakover diode for detecting overvoltage of the thyristor between the gate and anode of a gate turn-off thyristor, this breakover diode is connected to the gate of a high-speed thyristor, and the cathode of the high-speed thyristor is turned off. An overvoltage emergency ignition circuit for a gate turn-off thyristor, characterized in that the anode of the high-speed thyristor is connected to a voltage dividing resistor for making its withstand voltage smaller than the withstand voltage of the gate turn-off thyristor.