A Study on the Voltage-Clamping caused by Dynamic Avalanche at Over-stress Turn-Off of GCTs

Dynamic avalanche is a key factor leading to the power device failure. By the device simulation, it is found that when the gate commutated thyristor (GCT) is turned off at a high supply voltage or high stray inductance, the anode-cathode voltage is clamped at certain value and a destructive stationary filament appears. Its mechanism is explained in detail. Additionally, the SOA limited by the voltage clamping is depicted, which implies the shrink of the SOA with the increase of the emitter efficiency of anode.