Series connection of IGBTs with active voltage balancing

This paper describes a gate drive circuit for series-connected IGBTs in high voltage applications. The control criterion of the gate drive circuit is to actively limit the voltages during switching transients, while minimizing the switching transient and losses. In order to achieve the control criterion, a closed loop control scheme is adopted. The closed loop control injects current to an IGBT gate as required to limit the IGBT collector-emitter voltage to a predefined level. The performance of the gate drive circuit is examined experimentally by the series connection of three IGBTs with conventional snubber circuits. The experimental results show the voltage balancing by an active control with wide variations in loads and imbalance conditions