Output Regulation With Integrated SR Switch Duty Cycle Control for Wireless Power Transfer Systems

Due to the physical separation between primary and secondary sides, achieving a good output regulation in a wireless power transfer (WPT) system is nontrivial. Typically, an additional dc–dc converter stage at the secondary side or a radio frequency (RF) communication link between the primary and secondary sides is used to regulate the output. However, these approaches are not always practical in many industrial applications where there is a size constraint, or the noise interference that tends to interrupts the RF link. In this article, an integrated secondary-side regulation scheme without extra devices or communication requirement is proposed. The duty cycle of the secondary-side synchronous rectification (SR) device is controlled to regulate the output independently of the primary. The SR duty modulation allows voltage regulation over a wide load range or current regulation over a wide input range while avoiding the additional dc–dc converter stage. Thus, the primary-side control can operate under the fixed-duty condition while maintaining zero-voltage switching (ZVS) for all switches in the entire power range. A 48-V/190-W GaN high-electron-mobility transistor (HEMT)-based prototype has been built and tested to verify the feasibility of the proposed control scheme.