Near-Unity Power Factor, Voltage Step-Up/Down Conversion Pulse-Width Modulated Switching Rectification for Wireless Power Transfer Receiver
The pulse-width modulated (PWM) switching rectification that can achieve a high power factor (PF) for increasing the energy transfer efficiency between a LC resonator and a rectifier and voltage step-up and -down conversion is proposed for a wireless power transfer (WPT) receiver. The proposed method can emulate the switching rectifier as a resistive load by using an inductor and integrated phase synchronizers. Additionally, similar to a switched-inductor converter that controls the duty cycle ratio (D), the proposed PWM rectifier can control the output voltage VOUT when the input is a rectified, wirelessly-coupled voltage instead of a constant voltage. Thus, unlike a conventional PWM switching rectifier for AC mains, an additional voltage conditioning circuit would not be needed after the proposed rectifier for WPT. The proposed PWM switching rectification is implemented in the AMS 0.18m 1.8V/5V CMOS process. The PF=1 is measured, indicating the most efficient energy transfer, compared to only 0.55 to 0.65 in a peak detection rectifier. Additionally, 88.2% of peak power conversion efficiency (PCE) of the switching rectifier is achieved, and the maximum output power is 80.3mW at 500kHz of the WPT frequency. Moreover, the measured voltage conversion ratios ranging between 0.73X and 2X are demonstrated in this work.