A capacitive power transfer system with LCL primary compensation for very-low-power portable devices

This paper investigates and technically demonstrates a capacitive power transfer (CPT) system applicable to the charging of emerging very-low-power portable devices. The constant-current operation of the primary LCL compensation in CPT is implemented and analysed to simplify the system design process and minimize the configuration on the receiving side. Additionally, the system design considerations for the capacitive coupler and the diode rectifier are presented based on the battery charging specifications. All the design concepts and considerations are validated through experimentation with a 13.56 MHz CPT system, which achieves load-independent constant-current output from full-load to light-load (one-tenth of the full load) charging operations.