A Distance-Independent Wireless Charging System With Hybrid Topology and Control

This paper proposes a distance-independent wireless charging system that achieves constant current (CC) and constant voltage (CV) output through utilization of a reconfigurable topology, capable of seamlessly switching between a two-coil and a three-coil configuration. In order to enhance output adjustability and improve the efficiency of the charging process, this system combines the advantages of fractional-order and integer-order resonant circuits. In the two-coil configuration, the output of the inverter on the transmitter side is modulated as that of a fractional-order capacitor. By analyzing frequency characteristics of the fractional-order circuit, a control strategy of variable fractional order is introduced to achieve CC output against variations of transfer distance based on a mutual inductance recognition method. After transitioning to the three-coil configuration, the system inherently achieves a CV output by operating the inverter at a fixed frequency and forming an integer-order resonant circuit. In addition, in both mentioned configurations, the full-bridge (FB) mode and half-bridge (HB) mode of the inverter are utilized to minimize switching losses and broaden the range of soft-switching operation, catering to various load conditions. Finally, an experimental prototype is built to achieve CC and CV output within a wide charging range.