Investigating the effect of snubber capacitor on high power IGBT turn-off

A 20kW bidirectional dual active bridge DC-DC converter prototype is designed and built for aerospace energy storage applications. The converter employs high power IGBT modules on the high voltage and low voltage sides. This paper presents the theoretical analysis and experimental results of turn-off performance of those high power IGBTs with capacitive snubbers. The turn-off performance of the 1200V, 300A ultrafast IGBT and 600V, 760A trench IGBT has been analyzed with and without a snubber capacitor. The influence of variation in snubber capacitor and variation in gate resistance on the IGBT performance is discussed. This gives a better understanding of IGBT characteristics during the turn-off transient. Experimental results show that the snubber capacitor reduces the voltage stress and switching losses significantly during turn-off. The direct mount snubber outperforms the wire-ended snubber for the same value of capacitance; hence they are suggested for high frequency, high power applications.