Impact of snubber parameters on voltage sharing in series-connected insulated gate bipolar transistors

Abstract

This paper shows the relationship between the circuit parameters and the voltage sharing performance in series-connected insulated gated bipolar transistors (IGBTs). A simple analytic model is proposed to examine voltage balancing in series-connected IGBTs. By the proposed model, the reason for voltage imbalance is easily analyzed. In addition, the impact of the time constant of the snubber, which is affected by the snubber components, is detailed. From this analysis, it has been demonstrated that the snubber capacitance should be at least double the output capacitance of the switching device to stabilize voltage sharing. To verify the usefulness of the proposed technique, a multiple pulse tester has been implemented and tested. Experimental results reveal that the error between the proposed model and the practical system is only 1.7%. In addition, the accuracy of the proposed model is high enough to be utilized for the analysis of the series-connected IGBTs.