A 6.78-MHz Single-Stage Wireless Power Receiver Using a 3-Mode Reconfigurable Resonant Regulating Rectifier

A 6.78-MHz wireless power receiver using a 3-mode reconfigurable resonant regulating rectifier for resonant wireless power transfer is presented. The proposed receiver improves power conversion efficiency and reduces die area and off-chip components by achieving power conversion plus voltage regulation in one stage, using only four on-chip power transistors and one off-chip capacitor. Moreover, the proposed 3-mode operation reduces the output voltage ripples and accomplishes switching synchronization easily during mode switching. The proposed pulsewidth modulation controller using ramp-stacking technique and type-II compensation achieves tight voltage regulation in the full loading range with fast transient responses. An adaptive sizing method is also employed to further improve the light-load efficiency of the receiver. Fabricated in a standard 0.35-mu m CMOS process using 5-V devices, the receiver regulates the output voltage at 5 V and delivers a maximum power of 6 W. The measured peak efficiency reaches 92.2% when delivering an output power of 3.5 W. For a load step between 0.5 and 5 W, the overshoot and undershoot are less than 300 mV and the settling times are less than 16 mu s.