JPS62256528A - Gate circuit for gate turn-off thyristor - Google Patents

Abstract

PURPOSE:To protect a gate circuit by connecting a diode having a large current capacity in anti-parallel with a transistor (TR). CONSTITUTION:When a signal is inputted to a TR 3, an on-gate current is conducted through a resistor 5, a GTO 8 is turned on, and when a signal is inputted to a thyristor 7, an off-gate current is conducted through an inductance 6, the GTO 8 is turned off. In connecting the diode 4 in anti-parallel with the TR 3, even when the turn-off is failed, the destruction of the TR 3 due to overcurrent is prevented. A sufficiently large current capacity to bypass the overcurrent is selected for the diode 4. Thus, the gate circuit is protected and its reliability is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a gate circuit for a GTO (gate turn-off thyristor).

[Conventional technology]

A conventional GTO gate circuit configuration is shown in FIG.

When a signal is input to the transistor 3, an on-gate current flows through the gate terminal G, and the GTO 8 is turned on. On the other hand, when a signal is input to the thyristorph, an off-gate current flows to the gate terminal G, and the GTO8 turns off.
If the anode current i of the GTO when it is on is within the rated value, it will turn off normally as shown in FIG. In connection with this gate circuit, the Electrical Society, High Frequency Power Device Application Research Expert Committee (1985) ``GTO Driver Briefing Materials'' (Japan Inter) is known.

[Problem that the invention seeks to solve]

In the above conventional GTO gate circuit configuration, when the GTO is on,
If an excessive current exceeding the rated anode current i flows through, turn-off fails as shown in Figure 4, and i = O
A current with a rapid increase rate di/dt flows from the anode A in FIG. 2 through the gate G into the gate circuit before the current rises. rate of increase di/dt
An electromotive force proportional to is generated, which causes an excessive current to flow into the collector of the transistor 3 through the resistor 5, causing the transistor 3 to be destroyed.

An object of the present invention is to eliminate the above-mentioned problems in a GTO gate circuit and protect the gate circuit.

[Means for solving problems]

The above object is achieved by connecting a diode with a large current capacity in antiparallel to the transistor.

[Effect]

In order to solve the above-mentioned problem, a diode 4 is connected anti-parallel to the transistor 3 as shown in FIG.
This is because the electromotive force across the inductance 6 generated by the current flowing into the gate circuit through the gate G when O fails to turn off is large.

There is a risk that excessive current will flow through the transistor.

The diode serves to protect the transistor by bypassing this large current.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. Essentially, it is the same as in FIG. 2, only with the diode 4 connected. When a signal is input to the transistor 3, an on-gate current flows through the resistor 5, turning on the GTO 8. When a signal is input to the thyristor, an off-gate current flows through the inductance 6, and the GTO 8 turns on.
8 is the one that turns off. In addition, DC power supplies 1 and 2
are used to flow an on-gate current and an off-gate current, respectively.

With this circuit configuration in which the diode 4 is connected in antiparallel to the transistor 3, even if turn-off fails as shown in FIG. 3, it is possible to prevent the transistor 3 from being destroyed by overcurrent. The diode 4 is selected to have a sufficiently large current capacity so as to bypass overcurrent.

〔Effect of the invention〕

According to the present invention, by connecting a diode with a large current capacity in antiparallel to the GTO-on transistor, the gate circuit can be protected and its reliability can be improved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of an embodiment of the GTO gate circuit of the present invention,
Figure 2 is a circuit diagram of a conventional GT○ gate circuit, Figure 3 is a circuit diagram of a conventional GT○ gate circuit.
An explanatory diagram of the normal turn-off characteristics of TO, Figure 4 is GTO
FIG. 4 is an explanatory diagram of the characteristics when the turn-off fails. 3...Transistor, 4...Diode, 8...
G.T.O.

Claims (1)

[Claims] 1. In the gate circuit of the gate turn-off thyristor, this transistor is used to prevent excessive current from flowing in the gate circuit and destroying the on-transistor of the gate turn-off thyristor if the gate turn-off thyristor fails to turn off. A gate circuit for a gate turn-off thyristor characterized by having a diode connected in antiparallel to the gate turn-off thyristor.