Analytical Modeling of Switching Energy of Silicon Carbide Schottky Diodes as Functions of dIDS/dt and Temperature

SiC Schottky Barrier diodes (SiC-SBD) are known to oscillate/ring in the output terminal when used as free-wheeling diodes in voltage source converters. This ringing is due to RLC resonance between the diode capacitance, parasitic resistance and circuit stray inductance. In this paper, a model has been developed for calculating the switching energy of SiC diodes as a function of the switching rate (dIDS/dt of the commutating SiC MOSFET) and temperature. It is shown that the damping of the oscillations increases with decreasing temperature and decreasing dIDS/dt. This in turn determines the switching energy of the diode which initially decreases with decreasing dIDS/dt and subsequently increases with decreasing dIDS/dt thereby indicating an optimal dIDS/dt for minimum switching energy. The total switching energy of the diode can be sub-divided into 3 phases namely the current switching phase, the voltage switching phase and the ringing phase. Although the switching energy in the current switching phase decreases with increasing switching rate, the switching energy of the voltage and ringing phase increases with the switching rate. The model developed characterizes the dependence of diode’s switching energy on temperature and dIDS/dt hence can be used to predict the behavior of the SiC SBD diode.