Resonant Tuning Rectifier for Parallel Compensated Receivers in Wireless Power Transfer

Themismatch between switching frequency and receiver (RX) resonance occurs in frequency-modulated spread-spectrum application. The conventional resonance tuningmethods for parallel-compensated RX are not effective because they require additional power components, which increase power loss and system volume. Other switched-capacitor or active rectifier-based reactance tunings cannot be applied to parallel-resonant RX due to the opposite waveform nature of series-resonant and parallel-resonant circuits. To solve these issues, we propose a parallel-resonant tuning rectifier (RTR) which can fix the resonance mismatch of parallel-compensated RX during spread-spectrum frequency modulation. The proposed design does not need extra power components such as capacitor or switch as well as complex control logic. Rather, the tuning is achieved simply by synchronizing the rectifier MOSFET's turn-OFF with the zero-crossing of primary current. Moreover, the proposed tuning MOSFETs achieve zero voltage switching (ZVS) turn-ON and low dv/dt turn-OFF, which avoids switching loss. A 2.2 kW prototype is fabricated and tested. The measurement results show that the proposed RTR can achieve constant output power and improve the overall efficiency by 3.5%–8.1% point when the operating frequency is detuned ranging 80–90 kHz.