Unified Coil and Compensation Network Design for Improving Wireless Power Transfer Efficiency Over Wide Output Load Variation Ranges

It is shown that the compensation network and coil design collectively affect wireless power transfer (WPT) efficiency. Based on this fact, a novel design approach of WPT systems is proposed. Unlike the majority of existing designs that aim at enhancing power transfer efficiency (PTE) at one rated operating point, the proposed design enhances the overall system PTE. This feature is essential for variable output loads, such as batteries, where their internal impedance varies during the charging period. To achieve this goal, improving the time-weighted average efficiency of the WPT system is set as the design criterion. Experimental studies of a 1.2-kW WPT system supplying constant resistive loads and battery loads verify that the proposed design enhances PTE both at rated output load and under wide output load variations.