Performance Comparisons of Synchronous and Uncontrolled Rectifiers for 27.12 MHz Wireless Power Transfer Using CMCD Converters

High-frequency (HF) and very-high-frequency (VHF) operation benefits wireless power transfer (WPT) in miniaturization and resilience. It is largely uninvestigated whether synchronous rectifiers or uncontrolled rectifiers have better performance, especially regarding efficiency, for HF-VHF WPT. We investigate 27.12 MHz wireless power transfer rectifiers using current-mode class D (CMCD) converters. A rectifier model and resonant condition in the receiver side are derived based on our previous model. We employed GaN FETs, diode-connected GaN FETs, and Si Schottky diodes in the CMCD rectifiers. Prototypes demonstrate a proof of principle and peak efficiency of 74.4% with output power of 14 W is achieved at the load side with the uncontrolled rectifier using diode-connected GaN FETs, which is the best performance among them.