Optimization of Self-Oscillating Power Converter Based on GaN HEMTs for Wireless Power Transfer

This work presents a novel approach for the optimization of a self-oscillating power converter (Royer converter) based on GaN HEMTs for inductively coupled wireless power transfer applications. By combining gallium nitride high electron mobility transistors (HEMT) as power transistors and depletion-mode (silicon) transistors as control transistors, not only the better intrinsic performance of GaN is used, but also all auxiliary supply voltages can be omitted in comparison to the standard silicon transistor-based Royer converter. This paper describes the functional principle with the aid of a simulation based on an inhouse extended power transistor model and optimized transistor parameters. Then it gives insight into the novel prototype and demonstrates the operation at a resonance frequency and an output power of up to 500 kHz and 90 W at 30 V input voltage with peak efficiencies above 94% for the whole wireless power transfer system. Finally, the limitations and further optimizations for such Royer converter systems will be discussed.