Enhancing Conversion Efficiency in Megahertz Wireless Power Transfer Systems with Schottky Freewheeling Diodes

This paper presents a potential method to improve the efficiency of megahertz-range wireless power transfer systems. In these systems, GaN FETs are commonly used as power switches. Due to the inherent reverse conduction capability of GaN FETs, there are typically no freewheeling diodes parallelling across them. However, through analysis and experimental validation, it is found that at megahertz, paralleling low forward voltage drop Schottky freewheeling diodes can significantly reduce the temperature rise of GaN FETs, thereby effectively improving system efficiency. In this paper, we first analyze the operating principles of GaN FETs and construct a simplified equivalent model. Furthermore, through simulations and hardware experiments, we compare the efficiency of WPT systems with and without freewheeling diodes, and the effectiveness of the proposed method is validated. This study dispels the misconception that GaN FETs do not require parallel freewheeling diodes and provide a new insight for optimizing high-frequency wireless power transfer systems.