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.The Taiwan Cambridge Scholarship and the IET Postgraduate Scholarship

High power factor wireless power transfer front-end circuit for heterogeneous systems

This paper investigates a high power factor switch-based wireless power transfer front-end circuit for heterogeneous systems. This circuit uses an integrated switching rectifier, implemented in 0.18um 1.8V/5V CMOS process. An integrated pair of phase synchronizers is used to align the waveshape of a wirelessly-coupled sinusoidal voltage source in the receiving coil to the corresponding conducting current. Using this approach, the power factor can be increased above 0.9 without requiring any wireless or wired feedback to the transmitter. The integrated switching rectifier can also provide: ac-dc rectification; facilitate the deployment of multi-receiver to single-transmitter wireless power transfer; and have the capability for voltage up and down conversion of the peak amplitude of the sinusoidal voltage source by use of a pulse-width modulation controller. From measured results, the output voltage can be stepped down from 1.65V to 1.08V and stepped up from 1.5V to 1.68V. Also, the measured power factor is 0.9 when the conducting current is managed at continuous conduction mode