The dynamic performance of SiC Schottky barrier diodes with parasitic inductances over a wide temperature range

Abstract

Silicon carbide is poised to replace silicon as the power semiconductor of choice in automotive systems like electric vehicle power trains where inductive loads are driven. Silicon carbide Schottky Barrier diodes (SBDs) have become commercially available and appear to be likely candidates for free-wheeling diodes in inverter modules where they are placed anti-parallel with insulated gate bipolar transistors. The switching characteristics of SiC SBDs have been investigated in inductive switching circuits with Si IGBTs over a temperature range of -40°C to 125°C. It has been shown that the diode voltage transient in the turn-off characteristics exhibited significant oscillations extending over several microseconds. This ringing, which has been reported by other authors, was not observed in silicon pin diodes tested under identical conditions. In this paper, SPICE simulations are used to show that the ringing is due to resonance in a series RLC circuit with the diode resistance, depletion capacitance and parasitic inductance causing oscillation in the output voltage. The smaller series resistance and higher depletion capacitance of the SiC diodes means that there is less damping, hence more ringing.