Two-dimensional analysis of GTO switching under the influence of external circuit

The authors discuss the influence of an external circuit on the internal behaviour of GTO structure and on waveforms in the circuit. Two-dimensional simulations have been performed with realistic RLC loading; the obtained waveforms have been successfully compared with experimental measurements. Computed results show that the peak of power density (i.e., a possible hot spot) remains located in the same place inside the structure throughout the whole turn-off process. The most dangerous voltage and power spikes are caused mainly by parasitic inductances in the external circuit. These results show the importance of GTO structure design as a function of external load conditions and the possibility of hot spots occurring under the cathode contact. The presented numerical results were obtained with a 2D device simulation program, PASS, running on a personal computer