JPS5913424A - Gate driving circuit of gate turn off thyristor - Google Patents

Abstract

PURPOSE:To turn on and off a gate turn off (GTO) thyristor only by one power supply with a simple constitution by using a switching circuit interlocked with the gate and cathode side of the GTO thyrustor respectively. CONSTITUTION:When the GTO thyristor Q1 is to be turned on, a switch SW1 is opened and a switch SW2 is closed. Since positive voltage applied to a terminal T1 is applied to the gate of the thyristor Q1 at the time, the GTO thyristor is turned on between the anode A and cathode K and current is made flow into a load RL by the voltage of a terminal T2. When the thyristor Q1 is to be turned off, the switch SW1 is closed and the switch SW2 is opened. Consequently, current flowing into the cathode K is interrupted and made flow out immediately from the gate G through a closed contact of the switch SW1 and the thyristor Q1 is rapidly turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides gate-turn off
-Off, GTO) There are various drive circuits for the gate turn-off thyristors, including gate drive circuits for switching thyristors, which are capable of turning the anode current ON and OFF by controlling the gate voltage. However, these devices require two power supplies, have a complicated circuit configuration, or cannot provide a switching current capacity, all of which pose practical limitations.

An object of the present invention is to provide a drive circuit that eliminates the various drawbacks mentioned above.

Hereinafter, the present invention will be explained by way of examples thereof with reference to the drawings.

In FIG. 1, Ql is a gate turn-off thyristor, and A, G and G are its anode, cathode and gate, respectively. RL is a load such as a resistor, R1 is a resistor, S
Wl and SW2 are switches whose contacts open and close in conjunction with each other, and the contacts of SWl and SW2 operate in an inverse relationship such that when one is open, the other is closed. T1 and T2 are power supply terminals to which a positive DC power supply voltage is applied, and a common voltage may be applied to these terminals.

Next, the operation will be explained. To turn on gate turn-off thyristor Q1, switch SW1 is open while switch SW2 is closed. At this time, the positive voltage applied to the power supply terminal T1 passes through the resistor R1 to the gate turn.
Since the voltage is applied to the gate of off-thyristor Q1, the
The turn-off thyristor is turned on between the anode A and the cathode, and current is supplied to the load RL by the voltage applied to the power supply terminal T2. Next, to turn off the gate turn-off thyristor Q1, switch S
W1 is closed and switch SW2 is opened. At this time, the current that has been flowing through the cathode K until now cannot flow because the switch SW2 is open, and immediately flows out from the gate G through the closed contact of the switch SW1, so the gate turns off. - Thyristor Q1 can be quickly turned off.

That is, in the embodiment described above, the contacts of the switches SW1 and SW2 are turned on and off in a mutually opposite manner, thereby disconnecting the cathode side of the gate turn-off thyristor Q1 at the time of turn-off, while disconnecting the cathode side of the gate turn-off thyristor Q1. Since the gate current is grounded in a state close to a short circuit, the gate current can be quickly discharged, and the structure is simple, and the gate has the advantage of requiring only a -power source (gate).

FIG. 2 shows a second embodiment. In the figure, Q2 is a pnp) run lister, and Q3 is an npn) run lister.

R2 is a resistor, T3 is a gate pulse input terminal, and the same reference numerals as in other parts of FIG. 1 represent the same names. This embodiment has the configuration shown in FIG. 1, but uses pnp and npn switching transistors in place of the switches SWl and SW2, respectively, and the voltage at the gate pulse input terminal T3 changes between 1 and 72. When a switching pulse is applied, first, a positive pulse of voltage v2 causes transistor Q2 to
is off, and transistor Q3 is on, so a positive voltage is applied to the gate of gate turn-off thyristor Q1, turning it on, and its cathode exhibits a reduced resistance between the collector and emitter of transistor Q3, and the load Current flows. Next, gate pulse input terminal T3
When the pulse voltage decreases to 1, the transistor Q2 is turned on and the transistor Q3 is turned off, turning off as in the embodiment shown in FIG. According to the above configuration, there is an advantage that the gate turn-off thyristor can be easily turned on and off by controlling the gate pulse input terminal with a pulse waveform.

In this case, the gate pulse voltage V1. Select V2 appropriately,
Alternatively, by selecting the value of resistor R2 and setting the on-current of transistor Q3 as large as possible and the off-current as large as possible without impairing the turn-off operation, a transiently large switching voltage will be applied to transistor Q3 at turn-off. It is possible to prevent this from being damaged due to the application of a voltage.

FIG. 3 shows a third embodiment, which differs from FIG. 2 only in that a resistor R3 is used instead of the resistor R2, and one end of the resistor R3 is connected to the emitter side of the transistor Q2. In the above configuration, when turning on the gate turn-off thyristor Q1, the emitter voltage of the off-state transistor Q2 is supplied to the pace of the transistor Q3 through the resistor R3, and the gate turn-off thyristor Q1 is turned on. Also, when the transistor Q2 is turned on, a drop in the emitter voltage of the transistor Q2 is detected and the transistor Q3 is turned off.

In the above embodiment, the case where a transistor is used as a switching element is explained, but these are FE.
It is also easy to implement using semiconductor elements such as T and MOS.

As explained above, according to the present invention, the gate turn
By using switching circuits that are inserted into the gate and cathode sides of the off thyristor and operate in conjunction with each other, the turn-on and turn-off operations of the gate turn-off thyristor are ensured with a single power supply and a simple configuration. Since the switching current capacity can be increased, it has great industrial value.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a gate drive circuit for a gate turn-off thyristor according to an embodiment of the present invention, and FIGS. FIG. 3 is a circuit diagram of a third embodiment. Ql...Gate turn off thyristor,
Q2...first transistor, Q3...river/second transistor, RL...load. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
51!

Claims (1)

[Claims] a gate turn-off thyristor having a gate to which a DC voltage is applied and connected in series with a load; a first transistor connected between the gate and ground and controlled on and off by a gate pulse; A second transistor connected between the start-turn-off thyristor and the ground, and whose on-off operation is controlled in an inverse relationship to that of the first transistor.