Non-dissipative dynamic current-sharing snubber for parallel connected IGBTs in high power boost converters

This paper presents a new nondissipative dynamic current-sharing passive snubber circuit for parallel-connected IGBTs used in high-frequency, high-power boost converters. Without a current-sharing snubber, a small disparity in on-state resistance and/or in turn-on delay can result in large device current and thermal imbalances of two similar IGBTs, even with tight thermal coupling. The proposed circuit not only provides dynamic current-sharing means for the minority carrier switching devices, but also serves as an energy recovery turn-on and turn-off snubber which minimizes the boost diode reverse-recovery current as well the boost switch turn-on and turn-off losses. It is especially suited for high power PFC applications where multiple-switching devices in parallel are usually required. The proposed current sharing snubber is verified in a 12.8 kW, 3-phase, boost converter.