Resonant Capacitor Voltage Based 85-kHz 3-kW Synchronous Rectification on Wireless Power Transfer System

A wireless power transfer (WPT) system has been considered to be applied to various charging applications. Conversion efficiency is one of the important factors and is in need of improvement in various approaches. This paper proposes a WPT system consisted of a synchronous rectification without transfer side signals. The proposed rectifier is applied to a magnetic-field WPT system with a series-series topology. This system is characterized by the use of the voltage sensor at the secondary resonant capacitor to achieve the synchronous rectification. The theoretical analysis concludes by the secondary resonant capacitor voltage being 90 degrees forward from the rectifier input voltage. A synchronous rectifier is designed, constructed, and tested to verify the principles of operation. The conversion efficiency of the proposed synchronous system from dc to dc is 91.8% achieved at 85-kHz 3-kW output power and 1. 6pt higher than the diode rectifier method. The efficiency distribution results from the loss of the synchronous rectifier is 53.2 W lower than that of the diode rectifier.