Modeling of turn-OFF transient energy in IGBT controlled silicon PiN diodes

Abstract

Silicon PiN diodes are the most widely used rectifying technology in industry especially in voltage source converters. The PiN diodes are usually used as anti-parallel diodes across silicon IGBTs where they conduct current in the reverse direction as the current commutates between the phases of the converter. They tend to generate a considerable amount of energy losses during the turn-OFF transient due to the reverse recovery characteristics. The rate at which the diode is switched will determine the switching energy and will affect EMI, electrothermal stresses and reliability. Hence, it is vital to be able to predict the switching energy of the diode during its turn-OFF transient given the switching conditions so as to have a realistic approach towards predicting the operating temperature. The switching energy of PiN diodes is determined by the peak reverse recovery current, the peak diode voltage overshoot, the time displacement between them as well as the temperature dependency of these peaks. In this paper, a model is presented and validated over a temperature range of -75 °C to 175 °C and with switching speeds (dI/dt) modulated by the gate resistance on the low side IGBT ranging from 10 © to 1000 ©. Comparisons show consistency between model prediction and measurements result. The model is a novel method of accurately predicting the switching energy of PiN diodes at different switching rates and temperatures using the measurements of a single switching rate at different temperatures.