关键词: MOS栅控晶闸管, 脉冲放电, 栅极损伤, 阴极电感, 栅极串联电阻

Abstract: MOS-controlled thyristor is widely used in pulse field due to its extremely low on-state voltage drop and simple gate driving circuit. However, during the pulse discharge process, failure of MCT can be easily observed due to the damage of gate oxide layer. In this work, study of MCT gate failure during the pulse discharge process with extremely high di/dt is carried out, and the impact of cathode inductance on the potential difference between gate and cathode electrode is analyzed via simulation and experiment. Corresponding researches show that cathode inductance not only affects the magnitude of peak current and di/dt in pulse discharge loop, but also causes the cathode potential shock, which generates an extremely high potential difference between gate and cathode electrode and causes the damage of gate oxide layer due to overvoltage. In this work, by analyzing the failure mechanism of MCT, mathematic model of gate-cathode potential difference is established. Based on this model, the reliability of MCT in pulse discharge application is improved by reducing the cathode inductance and appropriately increasing the gate resistance.

Key words: MOS-controlled thyristor, pulse discharge, gate damage, cathode inductance, gate resistance