Switching performance of a SiC MOSFET body diode and SiC schottky diodes at different temperatures: 2017 IEEE Energy Conversion Congress and Exposition (ECCE)

This paper investigates the reverse recovery behaviour of a SiC MOSFET intrinsic/body diode and compares the diode's performance with similarly rated SiC Schottky diodes at different temperatures. A circuit level analytical modelling approach is proposed for rapid and accurate predictions of switching transients and losses. The analytical models were solved numerically using MATLAB and the results showed a very good match with the experiments and LTSpice simulations. The proposed models were more accurate than LTSpice models in predicting the switching losses and required one third of the computation time. It was found that using the SiC MOSFET's body diode could increase the MOSFET turn on losses by 35% to 79% as its junction temperature increases from 25°C to 125°C (600V 20A switching operation). This is due to the reverse recovery charge and higher junction capacitance of the body diode. This is in contrast with a Schottky diode which exhibits switching characteristics which have little variation with temperature. A detailed breakdown of MOSFET switching losses is also presented to quantify the losses due to reverse recovery and device and circuit parasitic capacitances, which shows that the reverse recovery of the body diode is responsible for 3% and 23% of the total switching losses at 25°C and 125°C, respectively. A SiC Schottky diode is connected across the body diode to suppress the reverse recovery effect and the experimental results showed the performance benefit of this configuration over a wide range of temperatures and load currents.