A Soft-Switching Secondary-Side Control Method Without AC Current Detection for Wireless Power Transfer Systems

This article proposes a novel synchronous secondary-side control method for wireless power transfer (WPT) systems without AC current detection and real-time wireless communication. The proposed method includes a fast output-control loop for output control and a synchronization loop for phase synchronization and ensuring zero voltage switching of the secondary-side switches. The regulation strategy for the initial stage is designed to avoid the issue of monotonicity. The small-signal model of the WPT system with the proposed control method is derived based on the generalized state space averaging and extended describing function methods. Based on the established model, the control system is designed, and the stability of the proposed method is studied. Experimental results based on a 157 W prototype are presented to verify the effectiveness and dynamic performance of the proposed control method.