An Efficiency Optimization and Constant Voltage Output Technology Based on Three-Coil WPT System

Constant voltage (CV) charging and efficiency Optimization are the most basic and primary targets to be achieved in wireless power transfer (WPT) systems. This brief proposes a three-coil WPT system based on efficiency optimization and constant voltage output technique. Under heavy-load conditions, both the inverter and rectifier operate in full-bridge mode with satisfactory efficiency. Under light-load conditions, the rectifier is reconfigured into a voltage-doubler and half-bridge rectifier, which forces the equivalent resistance close to the optimal equivalent load resistance (OELR) to improve the transfer efficiency of the system. It can ensure system efficiency in the range of 90.4% to 92.4% when the load is from 20Ω to 200Ω. Meanwhile, the inverter is reconfigured into a half-bridge inverter to achieve CV charging. Different from existing methods such as multi-coil and switch arrays, optimal-frequency tracking, and maximum-efficiency tracking (MET), this technique avoids redundant compensation components, complex control techniques and additional converters. Finally, after the simulation validation, which proves the feasibility of the proposed technology.