Modeling power converters using hard switched silicon carbide MOSFETs and Schottky barrier diodes

The emergence of silicon carbide MOSFETs and Schottky Barrier Diodes (SBD) at higher voltage and current ratings is opening up new possibilities in the design of energy dense power converters. One of the main advantages of these wide bandgap unipolar devices is the use of fast switching to enable the size reduction of passive components. However, packaging constraints like parasitic inductances limit how fast the MOSFETs and diodes can switch, because of high frequency electromagnetic oscillations or ringing. Ringing is a reliability concern as it stresses the devices and causes additional losses to the switching losses. In this paper, a framework of power converter design is introduced based on the analytical modelling of current commutation between the MOSFET and the diode. The analysis of the model is done in the frequency domain which lends it to easy use and computational efficiency. The impact of the parasitic inductances on the switching transients have been analyzed. The models are compared with experimental measurements and are shown to provide fast and accurate analysis of the switching transients. The results show the necessity of accounting for ringing when modelling power losses.