Phase-Locked Loop Combined with Chained Trigger Mode Used for Impedance Matching in Wireless High Power Transfer

In a wireless power transfer system (WPTS), the control technique of the active rectifier is vital for improving the transfer efficiency of the resonant network, expanding the operating range of the load, and increasing the power density. An indispensable component of such control technique is the accurate and reliable phase-locked method for the resonant current. However, the traditional phase-locked method based on the DSP controller tends to lose driver pulses, which might cause damage to the safe operation of the WPTS. This article illustrates the essential reason why the driver pulses lose and proposes a phase-locked loop combined with the chained trigger mode (PLL-CTM) that can lock the phase of the resonant current accurately and produce the driver pulses reliably. With the proposed PLL-CTM applied, the reliability of the WPTS can be enhanced tremendously. Furthermore, based on the PLL-CTM, this article also presents a double-side phase shift control (DPSC) strategy to achieve constant-current constant-voltage charging and minimize the power loss of the resonant network simultaneously. Finally, a 500-W WPT prototype is built to verify the feasibility of the DPSC with PLL-CTM. Benefiting from the DPSC with PLL-CTM, the WPTS not only obtains a high accuracy in steady state, but also achieves a good dynamic performance with the step change of RL and REref.