The two basic failure modes in the GTO-modelling and experiment

The two basic failure modes of the GTO thyristor have been successfully modelled for the first time using 2D simulations. A special method is applied to model the 3D nature of the phenomena. The device is represented by two physically modelled cells with slightly different turn-off characteristics. The numerical analysis includes selfheating, impact ionisation and realistic representation of the external circuits. The simulations are done in both snubbered and unsnubbered mode. The internal device characteristics match those of experimental devices. The two basic failure modes are the thermal run-away mode due to the stress inflicted by the snubber leak inductance and the local dynamic avalanche mode due to the excessive tail current. The two, experimentally observed, failure modes have been modelled in this consistent way for the first time. The immediate cause of the failure in both cases is the local retriggering of the cathode junction occurring in one single cell of the device. A very good agreement with electrical device characteristics including the SOA data is obtained