Comparative Study of Three Different Clamping Circuits for Series-Connected IGBTs

Connecting multiple low-voltage IGBTs in series is the most direct and simple way to improve the voltage rating of the devices. However, severe voltage imbalance lies in series-connected IGBTs during the switching process. Active Clamping Circuit (ACC) is commonly used to balance the voltage of series-connected IGBTs during the switching process, using Transient Voltage Suppressor (TVS) diodes to limit the collector-emitter voltage of the IGBT. This article compares three clamping circuits which are one-stage ACC, one-stage ACC with RC, two-stage ACC. The characteristics of each circuit are revealed, and the difference between the three circuits is summarized and discussed. Experiments have verified that two-stage ACC can both suppress the voltage imbalance caused by the tail current of IGBT and achieve the static voltage balance without additional snubber circuits and static voltage balance resistors at the power side. This paper contributes to understanding the characteristics of different clamping circuits and choosing a proper clamping circuit in practical applications.