Series connection of insulated gate bipolar transistors (IGBTs)

In power electronics applications, high voltage switches are realised by connecting existing devices in series. The main problem of unequal sharing of voltage across the series connected devices can be minimised by using active gate control techniques, snubber circuits and clamping circuits. The aim of this paper is to investigate the available voltage balancing techniques in series connection of insulated gate bipolar transistors (IGBTs) and to describe a hybrid voltage balancing method which is used to equalise the voltage sharing in series connected IGBTs during both switching transients and steady state. This technique consists of both active gate control circuit and small passive snubber. The active gate control circuit is very simple and passive snubber is optimised to have low power losses. Passive snubber was optimised for different operating voltages and currents. The proposed technique was simulated for two 1 kV/50 A IGBTs in series and the results show good voltage balancing