A resonant regulating rectifier (3R) operating at 6.78 MHz for a 6W wireless charger with 86% efficiency

Abstract

Wireless power transfer up to the 5W power level has become a recent trend for mobile phones, which can be classified into two types: inductive type and resonant type. Inductive type usually has higher efficiency but requires short distance and precise alignment between the transmitter and receiver. From the viewpoint of convenience, resonant type has much better freedom from distance and alignment under a handicap of somewhat less efficiency. Among the numerous resonant wireless power transfer (RWPT) mechanisms, the one using 6.78MHz or 13.56MHz band for fRS has been a the mainstream option [1-2]. Major sources of power loss related to efficiency degradation are the transmitter circuits, receiver circuits, and resonant tanks of both sides. The efficiency of the receiver circuit is more important since it is especially related to the thermal emission of hands-on mobile devices and has to meet a strict value because the recent mobile phones already spend most of their thermal margins on the application processor. In this paper, we suggest a new receiver circuit for RWPT with simple structure and high efficiency.