Research On The Reverse Conduction Applications Of Silicon Carbide JFETS

New power semiconductor devices, based on new materials like silicon carbide (SiC) or gallium nitride (GaN), have shown great advantages and prospects in many power applications. Until now, commercial SiC SBDs have be widely used in power factor correction (PFC) circuits, giving rise to the possibility of higher switching frequency, higher efficiency and power density. As for switching devices, SiC MOSFETs and JFETs are also commercially available now, providing new solutions for power applications, especially under conditions like high voltage/high temperature.Among these new devices, SiC JFET is relatively cheaper and more reliable, compared with other devices like SiC MOSFET, for its simple structure and crafts. For this reason, SiC JFET is a promising candidate for next generation power switches. Currently there some different JFET types, including the new structure with internal parasitic diodes integrated. For the typical JFET structure, no internal reverse diodes exist. And for the new JFET type, the reverse recovery characteristic is still unfavorable especially under higher junction temperature. As a result, ideal antiparallel schottky diodes are always included in many application topologies to ensure safety or restrict reverse recovery.Given this background, this paper proposes the application rules of choosing external antiparallel diode with SiC JFET, based on the characterization of reverse conduction capability of SiC JFETs under different junction temperature. Additionally, this work discusses the possibility of eliminating the external antiparallel diodes, relying on the reverse conduction capability of JFET channels. To verify the influence on the circuits’performance, switching characteristics are also tested under the double-pulse experiment and actual phase-leg application circuit. A complete evaluation of applications without external diodes is concluded, including reverse recovery charge, requirement of driving conditions, losses calculation and efficiency comparison.At the same time, a brand new rectifier concept (pinched barrier rectifier-PBR) is invented and introduced according to this reverse conduction mechanism. Pinched barrier in JFET channel shaped by adjacent P region, instead of conventional direct P-N barrier or schottky barrier, is used for adjustable threshold voltage, balancing the forward conduction and reverse leakage.