A 1-MHz hard-switched silicon carbide DC-DC converter

Silicon Carbide (SiC) is a wide bandgap semiconductor material that offers performance improvements over Si for power semiconductors with accompanying benefits for power electronics applications that use these semiconductors. The wide bandgap of SiC results in higher junction forward voltage drops, so SiC is best suited for majority carrier devices such as field effect transistors (FETs) and Schottky diodes. The wide bandgap of SiC results in it having a high breakdown electric field, which in turn results in lower resistivity and narrower drift regions in power devices. This dramatically lowers the resistance of the drift region and means that SiC devices with substantially less area than their corresponding Si devices can be used. The lower device area reduces the capacitance of the devices enabling higher frequency operation. Here, the results from a 1-MHz hard-switched dc-dc converter employing SiC JFETs and Schottky diodes will be presented. This converter was designed to convert 270Vdc to 42Vdc such as may be needed in future electric cars. The results provide the performance obtained at 1MHz and demonstrate the feasibility of a hard-switched dc-dc converter operating at this frequency.