A Cost-Effective Adaptive Rectifier for Low Power Loosely Coupled Wireless Power Transfer Systems

This paper introduces an integrated receiver circuit based on a full-wave adaptive rectifier (AR). It achieves complex impedance matching and enables complexity and cost reduction in resonant wireless power transfer (WPT) systems. The conversion and system efficiency based on this AR receiver are theoretically compared with other receiver architectures by using a WPT system model including all conduction and switching losses. Fabricated in a 0.18-mu m BCD process, the AR receiver chip operates at 6.78 MHz, occupies 3-mm(2) active die area and includes control and supporting circuitry for independent control of the reactive and resistive parts of the load impedance. The chip was tested in a 2.5-W WPT system, purposely built with extremely low coupling coefficient to enable spatial freedom. Experimental data show that the proposed AR chip achieves up to 96% efficiency. In addition, when used in a WPT system, it delivers 2.15 W with 50.3% system efficiency and 1.96 W with 29% system efficiency for coupling coefficients k = 0.085 and k = 0.03, respectively.