A new family of GTO devices for medium frequency applications

A new family of GTO (gate-turn-off) thyristors suitable for use in medium-frequency resonant converters is presented. The devices were designed so as to minimize the energy losses in the GATT (gate assisted) mode of operation. To this end, some modification to the fabrication process that improve the GTO characteristics in this particular application area were introduced. The devices were evaluated in a flexible test circuit especially developed to emulate the operating conditions seen in a parallel-load resonant inverter. This allowed an experimental investigation of their behavior in the various phases of operation (turn-on, conduction, turn-off, direct voltage reapplication, and tail). Testing demonstrated their ability to operate at frequencies up to 50 kHz and at powers up to hundreds of kilowatts. The main electrical characteristics of the devices, as derived from test measurements, are illustrated. Indications for an optimal utilization in resonant inverters are given, and other possible applications, notably in soft switching converters, are discussed.