Analysis of charge transfer in mixed turn-off thyristor (TOM)

In the mixed turn-off-thyristor, (TOM for `thyristor a ouverture mixte´), to remove the stored charge, the turn-off configuration of an asymmetrical GTO-thyristor is used with the assistance of an auxiliary `quasi-snubber´ circuit. Mechanism analysis of space-charge evolution and of charges evacuation for the gate as well as for the anode current, allows higher frequency operation and losses reduction. Several configurations for both the gate driver and the snubber circuit, associated with the same asymmetrical GTO-thyristor, are studied. The application structure is a direct-current chopper, supplying an inductive load. It is shown that losses at turn-off could be reduced significantly in the main device