The Impact of Parasitic Inductance on the Performance of Silicon-Carbide Schottky Barrier Diodes

1200 V/300A silicon carbide Schottky barrier diode (SiC SBD) and Si pin diode modules have been tested as freewheeling diodes under conditions of clamped inductive switching over a temperature range between 40 degrees C and 125 degrees C. Over the temperature range, the turn-OFF switching energy increases by 100% for the Si pin diode, whereas that of the SiC diode is temperature invariant and is 50% less than that of the Si pin diode at 125 degrees C. However, the SiC SBD suffers from ringing/oscillations due to an underdamped response to an RLC circuit formed among the diode depletion capacitance, parasitic inductance, and diode resistance. These oscillations contribute to additional power losses that cause the SiC SBDs to be outperformed by the Si pin diodes at -40 degrees C and 0 degrees C. The higher depletion capacitance and lower series resistance of the SiC SBD contribute to a lower damping factor compared to the Si device. Furthermore, the positive temperature coefficient of the ON-state resistance in silicon contributes to better damping at high power levels, whereas the temperature invariance of the ON-state resistance in SiC means the oscillations persist at high temperatures. SPICE simulations and experimental measurements have been used to validate analytical expressions that have been developed for the circuit damping and oscillation frequency.