A ZVS resonant receiver with maximum efficiency tracking for device-to-device wireless charging

Abstract

A receiver for efficient wireless power delivery at 6.78MHz from smartphones to IoT devices has been designed in 0.18 μm CMOS. The receiver implements a technique to estimate the end-to-end efficiency and achieve maximum efficiency-point tracking (MEPT) across the charge cycle of a Li-ion battery without needing an explicit communication channel with the transmitter. The MEPT technique is tested using two rectifier topologies designed in the same process - the commonly used synchronous full-bridge and a resonant topology with ZVS for high efficiency. Adding MEPT to the full bridge receiver yields an estimated 7.9% savings in transmitter energy in fully charging a Li-ion battery on the receiver, while using the resonant rectifier with MEPT achieves 13.8% total savings in transmitter energy.