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

TLDR

Silicon carbide’s wide bandgap yields higher forward voltage, high breakdown field, lower resistivity, smaller device area, and reduced capacitance, enabling high‑frequency power electronics. This study presents the performance of a 1‑MHz hard‑switched DC‑DC converter that uses SiC JFETs and Schottky diodes. The converter was designed to step 270 Vdc down to 42 Vdc, a voltage conversion relevant for future electric‑car power systems. Measured results at 1 MHz confirm the converter’s feasibility and demonstrate acceptable performance at this high switching frequency.

Abstract

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 270 Vdc to 42 Vdc such as may be needed in future electric cars. The results provide the performance obtained at 1 MHz and demonstrate the feasibility of a hard-switched dc–dc converter operating at this frequency.