Study of the voltage drop process for the case of high-power thyristors switched in the impact-ionization mode

Abstract

The voltage drop process for the case of high-power thyristors switched to the conducting state by an impact-ionization wave excited by means of an overvoltage pulse with a nanosecond rise time is studied. In experiments, a voltage with a rise rate dU/dt in the range of 0.5 to 6 kV/ns is applied to a thyristor with an operating voltage of 2 kV. Numerical simulation shows that the calculated and experimentally observed voltage drop times are in quantitative agreement only when the structure active area through which the switching current flows depends on dU/dt. The active area increases with dU/dt and with increasing initial silicon resistivity. In this case, the active area steadily approaches the total structure area at dU/dt > 12 kV/ns.