Resonance Compensation for Wireless Charging System Using a Dynamic Tuning Circuit Based on the Principle of Controllable Magnetic Flux

The detuning of the resonant tank due to component tolerance and aging influences the working performance of the wireless charging system (WCS). This article proposes a dynamic tuning circuit (DTC) using the principle of controllable magnetic flux to reinstate the resonant state. It has a continuous capacitance regulation ability, high precision, low current/voltage stress, and excellent parametric active disturbance rejection ability. First, the DTC's circuit structure and working principle are analyzed in depth, especially its core part--controllable magnetic flux inductor (CMFI). Second, the DTC's parameter design method is analyzed. The DTC's parameter sensitivity analysis is also performed. Third, the DTC's closed-loop control strategy is illustrated along with the resonant state determination and dynamic tuning units' workflow and circuit. Then, simulation results verify the DTC's feasibility in tuning the resonant tank. Finally, a prototype for the series-series compensated WCS is built. When the load resistance varies, and the deviation of passive components in the primary-side resonant tank occurs, using the DTC to restore the desired resonant state, system output power increases significantly, along with the system efficiency decrease slightly, compared to the case without DTC. Furthermore, the measured average adjustment precision of the DTC is higher than 98.5%.