JPH0223112Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a switching circuit for a silicon-controlled rectifier, and its purpose is to prevent the occurrence of commutation surge when the silicon-controlled rectifier is turned off.

Conventional silicon-controlled rectifier (hereinafter simply referred to as thyristor for simplicity) switching circuits are
It consists of two thyristors connected in parallel and a capacitor inserted between the two thyristors, and a gate signal is applied alternately to the two thyristors to turn off one of the thyristors. This is achieved by the commutation surge generated by the on-operation of the other thyristor and the time constant of capacitor charging.

In this way, the conventional thyristor switching circuit utilizes commutation surge, so
A large current surge will occur when the other thyristor is turned on, and this will reduce the di/dt of the thyristor.
Sufficient care must be taken in design regarding ratings.

Furthermore, since the circuit has a time constant due to the load and the capacitor, the oscillation waveform lacks sharpness.

Furthermore, a large amount of electrical energy will be lost during the off-operation of the thyristor.

Furthermore, the quality of switching is determined by the quality of the thyristor's OFF operation, and the quality of the thyristor's OFF behavior is determined by the time constant of the load and capacitor through the transformer.
Design is becoming more difficult.

As described above, conventional thyristor switching circuits have various disadvantages.
The basic cause of these disadvantages is that the conventional thyristor turn-off utilizes an oscillation operation using a time constant.

The present invention was devised to eliminate the drawbacks and problems of the conventional example described above, and is constructed by utilizing the relationship between the reverse voltage due to the backturn of the transformer and the voltage drop between the collector and emitter of the transistor. It is.

An embodiment of the present invention will be described below with reference to the drawings.

In the present invention, a thyristor 1 is connected to a primary coil of a transformer 3 whose secondary coil 6 is connected to a load 7.
This is related to the switching circuit of transformer 3.
The primary coil 4 has a large number of turns.
and a tertiary coil 5, which is a second primary coil with a smaller number of turns, are connected in series in opposite directions, and a thyristor 1 is connected in series to this tertiary coil 5, and the tertiary coil 5 and thyristor 1 are The transistor 2 is connected in parallel with the series circuit.

The ratio of the number of turns between the first primary coil 4 and the tertiary coil 5 is not particularly limited, and the point is that the induced voltage in the tertiary coil 5 when the transistor 2 is conductive turns off the thyristor 1 reliably. The number of turns that can induce the desired voltage value is sufficient.

Next, the operation of the illustrated embodiment will be explained in order.

When a gate signal is applied to the gate of the thyristor 1 and the thyristor 1 is turned on, the voltage induced by the first primary coil 4 causes the first primary coil 4 to
The main current flows through the path shown by the dashed line, passing through the tertiary coil 5 and the thyristor 1, thereby driving the load 7.

From this state, a pulse signal for conduction is input to the base of the transistor 2, and when the transistor 2 operates in a pulse manner and becomes conductive, a current from the first primary coil 4 flows through the transistor 2.

As a result, the tertiary coil 5 has a very small number of turns with respect to the first primary coil 4 and the secondary coil 6, and is reversely wound. A voltage with (+) on the side of the first primary coil 4 and (-) on the side of the first primary coil 4 is induced, and a current path shown by the thin line from the tertiary coil 5 to the transistor 2, the thyristor 1, and the tertiary coil 5 is generated, This causes thyristor 1 to temporarily turn
Turn off.

That is, due to the conduction of the transistor 2, the main current that had been flowing through the path up to that point now flows through the path shown by the dotted line from the first primary coil 4 through the transistor 2. Due to this action, a voltage of (Vd/n) with respect to the power supply voltage Vd is induced in the tertiary coil 5 in a direction opposite to the direction of the path.

At this time, if the operation of transistor 2 is within the saturation region, the voltage V1 between the emitter and collector of transistor 2 will be approximately 1 to 2 (V), so the anode voltage Va of thyristor 1 will be Va≦0. As a result, the thyristor 1 is temporarily turned off as described above.

If this state continues for longer than the turn-off time of thyristor 1, thyristor 1 is completely turned off.

As described above, the switching circuit of the thyristor 1 according to the present invention uses the electromagnetic energy stored in the tertiary coil 5 to turn off the thyristor 1, so that commutation surge current is not generated and is Therefore, the reverse voltage rating required for the thyristor 1 can be significantly reduced.

Also, whether or not thyristor 1 can be switched is as follows.
Since it is determined only by the turn ratio between the first primary coil 4 and the tertiary coil 5, and substantially only by the turn number of the tertiary coil 5, the circuit design becomes easy.

Since the power consumed in turning off the thyristor 1 is also applied to the load 7 through the transformer 3, the power loss in the circuit can be extremely reduced.

Furthermore, since there is no time constant circuit in the circuit,
Switching operation of thyristor 1 by a sharp square wave is achieved, and thyristor 1
This means that turn-off can be achieved without any time delay.

Furthermore, most of the electrical energy when driving the load 7 is controlled by the thyristor 1 which has excellent resistance, and the electrical energy for turning off the thyristor 1 is controlled by the transistor 2 which has excellent high frequency characteristics. This greatly increases the safety of semiconductor elements used in circuits.

As is clear from the above explanation, the thyristor switching circuit according to the present invention not only can reduce the rating of the semiconductor elements used in the circuit, but also can significantly improve its safety. In addition, since it is only necessary to set the number of turns of the tertiary coil, the design can be easily and accurately achieved, and furthermore, it has many excellent effects such as extremely low loss of electrical energy in the circuit. .

[Brief explanation of drawings]

The drawing is an electrical circuit diagram showing an embodiment of the present invention. Explanation of symbols: 1; thyristor; 2; transistor; 3; transformer; 4; first primary coil; 5;
Tertiary coil, 6; Secondary coil, 7; Load,,
,;course.

Claims (1)

[Scope of utility model registration request] The primary coil of the transformer 3, which has a load 7 connected to the secondary coil 6, is divided into a first primary coil 4 with a large number of turns and a second primary coil 5 with a small number of turns.
are connected in series in opposite directions, a silicon-controlled rectifier 1 is connected in series to the tertiary coil 5, and a transistor 2 is connected in parallel to the series circuit of the tertiary coil 5 and silicon-controlled rectifier 1. A switching circuit made of silicon-controlled rectifier elements.