A Partial Active Gate Control for Improvement of a Trade-Off Relation Between Surge Voltage and Efficiency in a Three-Phase Inverter

This paper presents a control method of fully digital active gate drivers in a three-phase inverter to simultaneously realize surge voltage reduction and efficiency enhancement. Generally, the surge voltages of power devices occur at each switching, and they are determined depending on the operation mode including switching schemes and three-phase current directions. The active gate control technology can change the gate drive current and switching speed in detail in every gate control period which is usually quite shorter than the switching period, and it contributes to suppressing surge voltages. However, offline optimization of the active gate driving pattern considering operating conditions is usually complicated and takes a long time to find a better gate pattern. In this paper, a partial active gate control method without detailed pattern optimization is proposed. In the proposed method, the active gate driving patterns of fully six gate drivers are suitably changed according to the phase angle of the three-phase current to minimize the highest surge voltage and the switching loss in a fundamental period without any optimization. A prototype of the three-phase inverter using a 6-in-1 SiC power module and six digital active gate driver ICs was developed to verify the improvement effect of the proposed active gate control. Based on an analysis result of operation modes and surge voltages in the three-phase inverter, a suitable active gate control method was clarified considering each operating region in one ac cycle. It has been verified that the proposed partial active gate control contributes to reducing the highest surge voltage, fixing a high efficiency.