Study on the clamp diodes of grid-emitter influencing the active voltage balancing of series connected IGBTs

This paper presents the clamp diodes in gate driving circuit significantly influenced the transient balancing of series-connected IGBTs. By the method of Monte Carlo and vary simulation analysis, slight differences of a plurality of IGBTs in the transient voltage balancing can be accumulated in a particular IGBT. More IGBTs, this case was more serious. The differences of voltage-clamp generally accounted for five percent, but the voltage differences emerged by 48 IGBTs in series were more than four times. Through the in-depth analysis, the diode clamp voltage difference would cause the gate turn-off delay differences. This is one of the key factors occurred the dynamic voltage imbalance.