A Quad-Mode Structure-Reconfigurable Regulating Rectifier With Shared-Inductor DC-DC Energy Recycling in a Wireless Power Receiver

A quad-mode structure-reconfigurable regulating rectifier (SR-RR) is presented for a wireless power transfer system. The proposed SR-RR combines an ac-dc regulating rectifier and a dc-dc boost converter in a single stage. The regulating rectifier converts the received wireless power to an output load and stores the excess power in a storage element to improve the power conversion efficiency. By allowing the regulating rectifier and the boost converter to share a receiver (RX) coil with adjustments to the power stage structure, the SR-RR operates as a dc-dc boost converter to extend the output power without requiring additional inductors. Freewheeling operation skips power to realize single-stage voltage regulation. In addition, the SR-RR operation mode is automatically selected from among four: charging, storing, boost converting, and freewheeling. The chip, fabricated in a 0.18-mu m CMOS process, can regulate an output voltage of 5 V and a stored voltage of 3.7 V. The measurement results demonstrate a 1.7x output power extension. Peak RX efficiency reaches 91.8%, while system efficiency reaches 64.7%.