A unified analytical model is derived from very basic principles. It allows the qualitative and-with certain restrictions-also quantitative description of all essential features characteristic of critical turn-off of devices based on the gate-turn-off-thyristor (GTO) principle and thus gives insight into the details of the destruction mechanism. In particular, it reflects that the turn-off capability is principally limited by the fundamental phenomenon of avalanche injection. Though idealized and simplified, the model correctly predicts or reproduces results from exact 2-D simulations and experiments-for example, the simultaneous pinning of voltage and current at high levels, the dynamic steepening and bending of the electric field profile, and the occurrence of traveling current filaments. The model is useful for estimating the safe operating area (SOA) of GTO-like devices.
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