A Comparative Study of Freewheeling Methods for eGaN HEMTs in a Phase-Leg Configuration

Enhancement gallium nitride high-electron-mobility transistors (eGaN HEMTs) have been developed with lower conduction losses and higher switching speed compared with MOSFETs. Self-commutated reverse conduction (SCRC) mechanism determines no reverse recovery phenomenon but a larger reverse conduction voltage drop of eGaN HEMTs than the body diodes in traditional Si MOSFETs or other freewheeling diodes. To reduce the large reverse conduction loss of eGaN HEMTs, the performance of different freewheeling methods for eGaN HEMTs in a phase-leg configuration is compared in this article. First, the reverse conduction mechanism and characteristics of eGaN HEMTs are analyzed. Then, four freewheeling ways for eGaN HEMTs are introduced, and the equivalent circuits are also given and analyzed. A double-pulse test platform is established to further explore the influence of the freewheeling ways on the conduction and switching characteristics. Finally, the total losses of a phase-leg configuration with different freewheeling ways based on a buck converter are analyzed and compared. This article aims to give guidance to properly select freewheeling ways for eGaN HEMTs under different operation conditions.