JPS5851618A - Gate circuit for gate turn-off thyristor - Google Patents

Abstract

PURPOSE:To reduce gate losses remarkably and to make the circuit constitution small in size, by splitting a switching circuit controlling a gate current of a gate turn-off thyristor into that for off-period and for tail-period. CONSTITUTION:A switching SW circuit controlling a gate current of a gate turn-off thyristor GT01 is constiuted with an SW element 4 for off-period, an SW element 7 for tail period, and a resistor 8 in parallel. The element 4 is turned on with signal (b) from a control circuit 5, a signal (c) turns on the element 7, a collector current (d) of the element 4 flows and an off-gate current (f) is applied to a GT01 via a pulse transformer 3. When the GT01 turns off and the element 4 is turned off, a collector current (e) of the element 7 flows, the gate current (f) is limited at the resistor 8, and since the gate current for the compensation of a tail current Itail only flows, a gate loss (h) is remarkably reduced, the elements 4, 7 can be made small in size and the circuit constitution can be made small in size.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gate circuit that supplies an off-gate current to a gate turn-off thyristor.

FIG. 1 shows an example of this type of gate circuit conventionally used. In the figure, 1 is a gate turn-off thyristor (hereinafter abbreviated as GTO), 2 is an off power supply that supplies off-gate DC to the GTOI, 3 is a pulse transformer that reprints the DC from the power supply 2 and transmits it to the GTOI, 4
5 is a switching element made of a transistor for controlling the supply of off-gate direct current; 5 is a switching element for controlling opening and closing of the switching element 4; 6 control circuit, 6 is switching element 4
This shows a diode that circulates the energy generated in the pulse transformer 3 when the pulse transformer 3 is turned off.

Next, the operation of the gate circuit having the above-mentioned circuit 4 will be explained using the waveform diagram shown in FIG. In the same figure, (a) is G
TOI anode voltage, (b) Ha,,+-tocathode ilJ'J voltage, (C) gate current, (d) gate-cathode voltage, (e) gate loss, (f) output from control element 5. The control signals of the switching elements 4 are shown respectively.

In FIG. 2-, when the switching element 4 is turned on by the control signal shown in (f), an off-gate current flows from the power supply 2 to the GTOI via the pulse transformer 3, as shown in (C). When the turn-off period toff shown in (a) has passed, the GTOI is turned off, and the voltage between the anode and cathode increases as shown in (b).

At the beginning of this period, that is, the tail period t, the Tilmi flow Itan flows through the GTOI, and there is a risk of re-ignition. Therefore, in order to prevent this, this tail turtle style Ita+
1 must be absorbed by the gate circuit, and for this purpose, the switching element 4 has a tail period t as shown in (f).
You must turn it on, including tall. On the other hand, in order to make the rise of the off-gate current of GTol steep, the voltage on the secondary side of the pulse transformer 30 (gate side of GTol) is set higher than the avalanche voltage of GTOI.

Therefore, as shown in (d), as the GTOI is turned off and the junction between the gate and cathode is restored, an avalanche current flows. As a result, the gate loss becomes extremely large during the tail period jtill, as shown in (e). Furthermore, as the gate loss increases, the off-power supply 2 and the switching element 4 also need to have a large capacity. This results in a disadvantage that one circuit becomes large as a whole.

An object of the present invention is to provide a gate of a GTO that can absorb Tilmi current without increasing gate loss by dividing a switching circuit that controls the gate current into an off period and a tail period. The purpose is to provide circuits. 'In the present invention, a switching circuit is constituted by two types of switching elements, one for gate current control in the off period and the other for gate current control in the tail period, and a resistor is connected in series with the latter.

Hereinafter, the present invention will be explained in detail using Examples.

FIG. 3 is a circuit diagram showing one embodiment of the present invention.
The same parts as in the figures are given the same symbols, and detailed explanation thereof will be omitted. In FIG. 3, a series circuit of a switching element 7 and a resistor 8 is connected in parallel to the switching element 4. The opening and closing of this switching element 7 is controlled by a control circuit 5, similarly to the switching element 4.

, Next, the operation of the gate circuit having the above configuration will be explained.

This will be explained using the waveform diagram shown in FIG. In FIG. 4, (a) is the anode current of the GTOI, (b) is the degree control signal of the switching element 4, and (C) is the switching element 7.
control signal, (d) is the collector current of switching element '4, (e) is the collector current of switching element 7, (
f) is the current flowing through the gate, (g) is the gate-cathode voltage, (
h) shows the gate loss, respectively.

In FIG. 4, when the switching elements 4 and 7 are turned on by the control signals shown in L) and (C), the collector current of the switching elements flows as shown in (d), and the voltage (f ) is supplied to the GTOI. When the switching element 4 is turned off at the moment when the GTOI is turned off, (e
), the collector current of the switching element 7 flows, and the gate current flows through the switching element 7.

At this time, the resistor 8 is connected to the switching element 7.

The directivity of the flowing gate ia flow is limited as shown in (f). In this case, the resistor 8 is set so that the gate current flowing through the switching element 7 can compensate for the Tilmi current: lau.

The on period t2 of the switching element 70 is the on period 1.2 of the switching element 4. The tail period of GTOI from the end of '
This is assumed to be until the "tall" is completed.

In this way, until the GTOI is turned off, an off-gate current sufficient to turn off the GTOI'f is supplied through the switching element 4.

After the GTOI turns off, only enough gate current flows to compensate for the tail current Iaa++ due to the limit A in the resistor 8, so as shown in Φ), the gate loss during the till period ttall is greatly reduced. be able to.

FIG. 5 is a circuit diagram showing another embodiment of the present invention, and the same parts as in FIG. 3 are denoted by the same symbols, and the explanation of the IOA is omitted. That is, in this embodiment, the gate current of GTOI is
This is an example in which the gate at and the source 2 are directly supplied without passing through the pulse transformer 3 shown in FIG. The functions of the control circuit 5 are the same as those of the circuit shown in FIG. 3 described above.

As explained above, according to the present invention, the current flowing through the gate of the GTO during the tail period can be suppressed to the necessary minimum, so the gate loss of the GTO can be significantly reduced, and the circuit configuration can be made smaller. It has the worrying effect of being able to become

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of a conventional GTO gate circuit, and FIG. 2 is a waveform diagram illustrating its operation. FIG. 3 is a circuit diagram showing an embodiment of the present invention, and FIG. 4(a)
to h) are waveform diagrams illustrating the operation thereof, and FIG. 5 is a circuit diagram showing another embodiment of the present invention. 1...Gate turn-off thyristor, 2...Off game 1 figure inferior 2 figure

Claims (1)

[Scope of Claims] 1. In a gate circuit for a gate turn-off thyristor, which comprises a gate d source for off, which supplies a gate current to the gate turn-off thyristor, and a switching circuit, which controls the supply of this gate current. The switch-over circuit includes a first switching element for limiting the supply of off-gate current, and a second switching element connected in parallel with the first switching element for limiting the supply of off-gate current, and for supplying a Tilmi current during the tail period after the gate turn-off thyristor is turned off. 1. A gate circuit for a gate turn-off thyristor, comprising an element and a resistor connected in series with the element.