Digital phase control for resonant inverters

This letter presents an approach for direct digital phase control of resonant inverters that is based on inductor current or voltage sensing. Compared to frequency control, phase control provides the advantages of self-tuning to the tank resonant frequency, reduced sensitivity for improved control near resonance, and inherent protection against operation below resonance to avoid hard switching. The digital control algorithm suitable for implementation using standard CMOS logic is derived. The design details of an experimental test platform based on a Xilinx field programmable gate array (FPGA) and experimental results for a typical resonant inverter are provided.