Non-Dissipative Dynamic Current-Sharing Snubber for Parallel-Connected IGBT's in High Power Boost Converters

This paper presents a new, non-dissipative dynamic current-sharing passive snubber for parallel-connected IGBTs used in high power boost converters. The proposed circuit overcomes the drawbacks of the negative temperature coefficient characteristic of IGBTs' on-state resistance. Without a current-sharing snubber, a small disparity in turn-on delay can cause a large current and thermal unbalance of two identical IGBTs with the same device characteristics even when they are mounted on the same heat sink. The poor current-sharing ability of IGBTs may cause them to fail prematurely and/or may require additional devices to provide sufficient current margin. The proposed circuit not only provides a dynamic current sharing means for the IGBTs, but also serves as an energy recovery turn-on and turn-off snubber which reduces the boost diode reverse-recovery peak current and the boost switch turn-on and turn-off losses. The proposed circuit is especially suited for high efficiency, high power PFC applications. In this paper, the operation of the circuit is explained and an analysis is given. A large-signal simulation based on a 10kW, 3-phase rectifier using the circuit is included. Test waveforms showing current-sharing capability as well as energy recovery turn-on/turn-off features obtained from two parallel-connected IGBT boost switches are also included.