100 MHz isolated DC-DC resonant converter using spiral planar PCB transformer

This paper describes a very high frequency (VHF) isolated dc-dc resonant converter operating at 100 MHz switching frequency with a rated output power of 2 W. The power stage consists of two half-bridge GaN chips with integrated gate drivers, one operating as a dc-ac inverter on the primary side, the other operating as an ac-dc synchronous rectifier on the secondary side. Isolation is provided by a spiral planar printed circuit board (PCB) transformer designed and optimized using 3D finite element modeling (FEM) tools and radio-frequency (RF) circuit design software. Simulation and experimental results are presented for a prototype step-down converter operating from 20 V input voltage. Experimental results show a peak efficiency of 80.5% at 1.8 W output power.