SiC devices for converter and motor drive applications at extreme temperatures

The normally off silicon carbide power vertical JFET (VJFET) can perform the role of switch, rectifier, or switch with anti-parallel rectifier. This innovative feature eliminates the need to qualify a separate diode that can withstand the rugged environment of, for example, the surface of Venus on-board a surface planetary probe, or that can be derated to exhibit high-reliability in merely harsh terrestrial environments in aerospace, automotive, or energy exploration. The VJFET reported here is a vertical trench JFET fabricated in 4H-SiC. It has demonstrated feasibility of at least a 500-h life at 500degC. This paper also demonstrates a simple half-bridge variable speed motor drive that is free of discrete pn-junction or Schottky barrier rectifiers and is simple to control with pulse width modulation because it does not need a high-temperature high-side gate driver. Extending the approach to a full-bridge or a six-pulse (three-phase) bridge is straightforward