MOS-gated Thyristors (MCTs) For High Power Switching

Abstract

Although power semiconductor switches have been used extensively in many power electronics applications, their utilization in pulse power circuitry has remained low. The principle reason has probably been the perception that short pulse operation, particularly under fast turn-on stress, either was not possible at all, or when possible, led to early failure. However, it has recently been shown (1, 2, 3, 4, 5, 6) that high peak currents and fast risetimes can be simultaneously obtained for short pulses in discrete semiconductor thyristors, and that the use of single elements in pulse power circuits is feasible for repetitive peak currents up to 10 KA and di/dt values in excess of 20 W p s (6). The advantage of thyristors over other semiconductor types of semiconductor switches is their high blocking voltage and very high steady-state current carrying capacity. There are, however, several types of thyristors, and both the gate turn-off thyristor (GTO) and the MOS-gated thyristor (MCT) are possible competitors; MCTs have, in fact, been proposed as a superior alternative to conventionally gated SCRs for pulsed power. Although some comparisons between conventional thyristors and GTOs have been made (5), there have been none with MCTs. This work was done to determine the behavior of MCTs as closing switches (capacitor discharge) under high current, short pulse, and repetitive operation for comparison with other types of thyristors.