A high current, ultrasonic GTO thyristor cathode switch

The cascode switch, the series connection of a high voltage bipolar device and low voltage MOSFET, provides high power and high frequency in a small volume. The cascode switch has many advantages, reverse gate or base current is equal to the turn off collector or anode current level and can be established at a rate of greater than 1000 A/μs. The authors discuss a gate turn off thyristor (GTO) and bipolar transistor (BJT) cascode switch with similar power ratings of 180 kVA operating on a 500 V to 700 V DC rail and with load currents of up to 300 A. The circuit was developed for the BJT cascode or emitter switch operating at 150 kVA and 50 kHz and subsequently applied to the GTO cascode or cathode switch. The authors show the results achieved and compare the two types of switch