A Hybrid Active Gate Drive for Switching Loss Reduction and Voltage Balancing of Series-Connected IGBTs

Insulated gate bipolar transistors (IGBTs) are usually connected in series to form high-voltage switches in power electronics applications. However, the series operation of IGBTs is not easy due to the unbalanced voltage sharing between them, especially during the switching transients and the tail-current period. In this paper, a hybrid active gate drive is presented for both switching loss reduction and voltage balancing of the series-connected IGBTs. Compared with the conventional gate drive, the proposed method allows dynamical adjustment of the switching speed of IGBTs; thus the switching loss can be suppressed without increasing the current and voltage stresses of the power device. For series connection, the transient voltage sharing is achieved by using an adaptive control method, while the voltage balancing during the tail-current period is optimized by a low-loss snubber circuit. The performance of the proposed hybrid active gate drive and control method has been validated by experimental results.