Reduction of Reflected Power Loss in an AC-DC Converter for Wireless Power Transfer Systems

Abstract

This paper discusses a method to reduce reflected power in an AC-DC converter in high-frequency wireless power transfer systems. First, conventional capacitor input-type rectifiers with silicon carbide (SiC) and gallium nitride (GaN) diodes are experimentally tested. From an analysis of the results, it is confirmed that the reflected power occurs at the input stage of the rectifiers owing to impedance mismatching. The reflected power should be suppressed because it will decrease the transmission efficiency. In order to solve the above-mentioned problem, an AC-DC converter that implements input impedance matching is proposed in the last half of the paper. This paper presents the basic characteristics of the AC-DC converter and the experimental results, which show that the input impedance of the AC-DC converter enables a conversion from 13.56 MHz AC to DC with an input impedance of 29.6 + j0.51 Ω. Thus, the reflected power is suppressed by 37.8% compared with the conventional capacitor input-type diode bridge rectifier with a load resistance of 25 Ω. From the experimental results, it is confirmed that the AC-DC converter is a valid circuit configuration for wireless power transfer systems.