Variable-speed IGBT gate driver with loss/overshoot balancing for switching loss reduction

Abstract

This paper introduces a new method of IGBT switching loss reduction on the system level, while leaving the PWM scheme completely unchanged. The switching loss reduction is achieved by designing an IGBT gate driver that dynamically sets the IGBT gate current depending on feedback signals from IGBT current, IGBT voltage, phase load current, and DC link voltage if it is not constant in the application. Factors influencing switching losses will be demonstrated for two types of output driver stages: one with discrete switching speed setting and one with continuously variable switching speed. Comparing to other gate driver types with or without feedback aimed at keeping constant dv/dt, di/dt, and overshoots of IGBT voltage and current, the proposed gate driver not only ensures the operation of an IGBT in the safe operating area (SOA), but also improves the SOA utilization density by tracking the programmed voltage and current limits using peak-detection circuitry while minimizing the switching losses. Adaptive feedback control algorithms have been developed and verified by simulations. Keywords—gate driver; variable current output stage; IGBT switching loss; adaptive control algorithm I. INTRODUCTION Discrete IGBTs and IGBT modules are used in high- voltage applications mainly to perform DC to AC power conversion and vice-versa. The conversion losses dissipated by devices in form of heat consist of three sources: conduction losses, leakage current losses, and switching losses. The first two sources usually cannot be varied as long as appropriate extreme levels of gate-emitter voltage are applied to the IGBT. The switching losses, on the contrary, can be widely varied by using different modulation schemes, switching frequencies, and gate drivers. The topic of this paper is about development of a closed-loop gate driver with the task of minimizing switching losses while keeping the IGBT in the SOA.