Parallel Connection of Integrated Gate Commutated Thyristors (IGCTs) and Diodes

This paper describes the parallel connection of 4.5 kV integrated gate commutated thyristors (IGCTs) and diodes. The impact of varying device characteristics on the stationary current distribution of parallel connected semiconductors is investigated. Possible solutions to improve the current sharing at steady state are presented. A thermal stabilization effect of parallel connected IGCTs is discussed. Furthermore, the behavior of parallel connected devices during switching transients is investigated experimentally in a 1.5-kV, 5-kA buck converter. Especially, the impact of asymmetrical circuit layouts, magnetic couplings, different turn-on and turn-off delays, and junction temperatures are considered. It is shown that a substantial current derating is necessary to enable a reliable operation of parallel IGCTs and diodes.