A scalable SiC device for DC/DC converters in future hybrid electric vehicles

The potential increased power density and high temperature capability of silicon carbide makes it an ideal candidate for use in future hybrid electric vehicle (HEV) technology. A secondary cooling system is required to maintain an 85degC base plate temperature for silicon based power electronics; but by creating a silicon carbide (SiC) based replacement this requirement could be relaxed. One anticipated benefit, among many, is that the secondary cooling loop could be eliminated and instead interfaced with the engine coolant system designed to maintain a maximum temperature of 105degC. The purpose of this paper is to present an all-SiC scaled prototype that is modeled after the DC-DC converter used in the Prius II to establish a high voltage DC bus interconnecting the motor and generator. The design uses a SiC JFET and SiC Schottky diode as the switching pair of a 1 kW scale model that investigates an inherently safe approach for use in future HEVs. The ability to parallel these unipolar devices results in a scalable device technology capable of achieving high-current, 600-V SiC switch technology in the near term that offers a potential 100degC increase in junction temperature above that rated for comparable silicon IGBTs