Hard- and soft-switching buck converter performance of high-voltage 4H-SiC and Si P-i-N diodes

This paper presents a detailed study of the performance of high-voltage Si and 4H-SiC diodes in a DC-DC buck converter. Device operation in hard- and zero-voltage switching conditions is presented with the help of measurements and 2-D finite element simulations. A combination of low excess carrier concentration and low carrier lifetime results in superior switching performance of the 4H-SiC diode over ultra-fast Si diodes. The use of soft switching is shown to minimize the loss and allow operation at higher switching frequencies using Si diodes. The use of soft-switching techniques results in a marginal reduction in power loss of the 4H-SiC diodes. However, the low overall power loss implies that SiC diodes can be used at very high switching frequencies even in hard-switching configurations.