Optimised diodes for high voltage GTO snubbers

In this paper, discussion is focused on the optimum characteristics of the diode for an active GTO snubber circuit. A description of the high voltage GTO turn-off operation which put in evidence the critical voltage and power loss spikes is reported. In this description, attention is drawn on the importance assumed by the electrical parameters of the snubber diode for the GTO safe turn-off operation. A new snubber diode with improved characteristics is proposed and the advantages of this new design with respect to the traditional solutions are explained. In the last section, the performance of the new generation snubber diode and the standard high voltage soft switching fast recovery diode are experimentally compared.