Failure dynamics of the IGBT during turn-off for unclamped inductive loading conditions

The internal failure dynamics of the insulated gate bipolar transistor (IGBT) for unclamped inductive switching (UIS) conditions are studied using simulations and measurements. The UIS measurements are made using a unique, automated nondestructive reverse bias safe operating area (RBSOA) test system. Simulations are performed with an advanced IGBT circuit simulator model for UIS conditions to predict the mechanisms and conditions for failure. It is shown that the conditions for UIS failure and the shape of the anode voltage avalanche sustaining waveforms during turn-off vary with the IGBT temperature, and turn-off current level. Evidence of single and multiple filament formation is presented and supported with both measurements and simulations.