Experimental Investigation on the Turn-Off Failure Mechanism of IGCT

The ambiguity in turn-<sc>off</sc> failure mechanism and subsequent limitation in turn-<sc>off</sc> capability has become the most critical issue preventing integrated gate commutated thyristor (IGCT) from further applications. In this article, to decipher the failure mechanism of IGCT, first, a well-designed experiment scheme eliminating all nonideal factors is proposed. Based on the scheme, a novel multilevel gate-driver is then designed and realized to decouple the commutation speed and the gate-cathode reverse bias voltage. With the proposed method, the electrical retriggering failure mechanism is observed and confirmed experimentally for the first time. The developing process for turn<sc>-off</sc> failure, stemming from the stored carrier nonuniformity, ending at the lateral voltage intensification raised by dynamic avalanche, is deciphered. Finally, the influencing factors and optimization methods to maximum turn-<sc>off</sc> current are discussed for future improvements.