This paper presents circuit design techniques for reducing the effects of magnetic flux, occurred from the planar transformer, on gallium nitride high-electron-mobility transistors (GaN-HEMTs) in 5-MHz 100-W high power-density LLC resonant dc–dc converters. For investigating the effects of magnetic flux on a GaN-HEMT, power device model for finite element method (FEM) simulation is proposed. In order to confirm the validity of the model, the quantitative evaluation is conducted with FEM simulation, and experiment using evaluation boards. Moreover, the optimization of printed circuit board layout is considered using the verified model with FEM simulation, for reducing the effects of magnetic flux on GaN-HEMTs while reducing the area of converter. In the experiments, 5-MHz 48 V/12 V 100 W unregulated LLC resonant dc–dc converter with efficient power conversion GaN-HEMTs is built as the prototype to verify the optimized layout. The maximum power efficiency can be achieved 91.28%, and the power density can be achieved 32 W/cm3.
Financed by the National Centre for Research and Development under grant No. SP/I/1/77065/10 by the strategic scientific research and experimental development program:
SYNAT - “Interdisciplinary System for Interactive Scientific and Scientific-Technical Information”.