Critical transient processes of enhancement-mode GaN HEMTs in high-efficiency and high-reliability applications

Wide-bandgap devices, such as silicon-carbide metal-oxide-semiconductor field-effect transistors (MOSFETs) and gallium-nitride high electron mobility transistors (HEMTs), exhibit an excellent figure of merits compared to conventional silicon devices. Challenges of applying such fast switches include accurate extraction and optimization of parasitics especially when 6high-efficiency operation, all of which require the comprehensive understanding of such switch especially its interaction with peripheral circuits. Particularly for the enhancement-mode GaN HEMTs without the intrinsic body diode, when reverse conducting, its high voltage drop causes a high dead-time loss, which has rarely a concern in silicon devices. This paper focuses on 650V/30~60A enhancement-mode GaN HEMTs provided by GaN Systems, analytically models its switching behaviors, summarizes the impact of parasitics and dead time, and applies it in two DC/DC converters. Systematic design rules are generated not only for soft switching but also for hard switching applications.