Planar transformer design in GaN based LLC resonant converter

Based on the third generation of semiconductor material, GaN device becomes obvious candidate for new generation POL converters. With the development of integration technology, planar transformer is applied for miniaturization and high power density. LLC resonant converter with EPC eGaN FETs and planar transformer is studies in this paper. First, the difference of LLC resonant converter with eGaN FETs from the one with silicon MOSFETs is analyzed. Second, winding structure of planar transformer is discussed, designed and simulated by Maxwell 2D and 3D finite element analysis (FEA). Finally, LTspice simulation of LLC resonant converter is developed, and a 500kHz/80W prototype is built to verify the analyses.