A low cost gate driver with dynamic turn-off transient control for HEV/EV traction inverter application

Abstract

The IGBTs are dominantly used in traction inverters for automotive applications. Because the Si-based device technology is being pushed to its theoretical performance limit in such applications during recent years, the gate driver design is playing a more prominent role to further improve the traction inverter loss performance. The conventional gate driver design in traction inverter application needs to consider worst case scenarios which adversely limit the semiconductor devices' switching speed in its most frequent operation regions. Specifically, when selecting the gate resistors, the IGBT peak surge voltage induced by di/dt and stray inductance must be limited below the device rated voltage rating under any conditions. The worst cases considered include both highest dc bus voltage and maximum load current. However, the traction inverter operates mainly in low current regions and at bus voltage much lower than the worst case voltage. This paper proposed a gate driver circuit that can mitigate the compromise between low switching loss and high device stresses. Compared with conventional gate driver circuits, only a low voltage PNP BJT, two Zener diodes and a resistor are added in the proposed circuit. The implementation is easy and the potential cost increase is low. The proposed gate driver can separately control the different phases of turn-off transient to achieve short turn-off delay, fast dv/dt and low surge voltage across IGBT. Because the proposed method does not require any feedback circuits, logic and control circuits which could limit the circuit bandwidth, this method can be used for fast switching applications.