Control of power semiconductors through center-tapped transformer with self-demagnetizing circuitry

摘要

In order to control a power semiconductor which can be triggered into conduction by pulses of one polarity and quenched again by pulses of the opposite polarity, by transmitting such pulses via a transformer to the power semiconductor connected at the secondary side of the transformer, such a pulse is formed by turning on a first transistor connected between one pole of a voltage source and a tap which divides the primary winding of the transformer into two partial windings, and by selectively turning on either one of second and third transistors each connected to the ends of a respective partial winding, and such a pulse is terminated by switching off the first transistor, while maintaining on the selected second or third transistor in order to cause the demagnetization current of the transformer to flow through the selected transistor and through a Zener diode connected between the tap of the primary winding and the other pole of the voltage source, the anode side of the first Zener diode being connected to the tap of the primary winding.