High current SiC JBS diode characterization for hard- and soft-switching applications

A newly developed high-current silicon carbide (SiC) junction barrier Schottky (JBS) diode with a 1200 V, 15 A rating was characterized and evaluated for both hard- and soft-switching applications. Experimental results indicate that the conduction characteristics are comparable with, but the switching characteristic is far superior to, its silicon diode counterpart. The SiC JBS diode exhibits nearly zero reverse-recovery time and associated losses. When applied to hard-switching choppers, it reduces not only the reverse-recovery loss, but also the main switch turn-on loss. Using the MOSFET as the main switching device, the combination of switch turn-on loss and diode reverse-recovery loss shows more than a 70% reduction. When applied to soft-switching choppers, the SiC JBS diode is used as the auxiliary diode to avoid the voltage spike during auxiliary branch turn-off. With the conventional ultra-fast reverse-recovery Si diode, a voltage spike exceeds the switched-voltage transition by 100%, and the auxiliary circuit requires additional voltage clamping or snubbing to avoid overvoltage failure. With the SiC JBS diode, however, the voltage spike is reduced to less than 50% of the switched-voltage transition, and the additional voltage clamping circuit can be eliminated. Savings in soft-switching choppers using SiC JBS diodes can be realized in size and weight reduction, energy loss reduction, and reduced packaging complexity.