Abnormal Turn-ON Phenomenon of Large-Size and High-Voltage Reverse Blocking IGCT

The large-size and high-voltage reverse blocking integrated gate-commutated thyristor (RB-IGCT) is available for the hybrid line-commutated converter topology to effectively reduce the commutation failure probability. However, an abnormal turn -on phenomenon is observed in the fabricated 8-kV RB-IGCT samples, which potentially hinders the normal current switching and has not been investigated yet. In this letter, we first reveal the mechanism of the abnormal turn -on through experiments and simulations at both the device level and cell level. It is concluded that the inhomogeneity between cells leads to the gate loop current and finally degrades the turn -on characteristics. Furthermore, we present a method to pinpoint the inhomogeneity based on the PNP and NPN current amplification factors, so that the root cause of the inhomogeneity is clarified. Finally, we propose an effective solution to optimize the homogeneity of the device, and the abnormal turn -on phenomenon of the RB-IGCT with high voltage and large size is eliminated.