THYRISTOR OVERVOLTAGE PROTECTIVE CIRCUIT

摘要

A high-power main thyristor is protected from forward voltage breakover by connecting in parallel relationship therewith an improved overvoltage responsive trigger scheme comprising at least one PNPN semiconductor element and a series L-C circuit. The PNPN element is connected between the anode and the gate of the main thyristor, and the L-C circuit is connected between the gate and the cathode. The element is selected to turn on in a voltage breakover mode when the forward bias voltage on the main thyristor attains a predetermined magnitude which is lower than the breakover level of the thyristor, whereupon the latter is triggered by a sharp gate punch.