Efficiency Optimization of Circuitry-Free Wireless Power Transfer Systems via Full-Bridge Step Density Modulation and Maximum Efficiency Tracking

In recent years, Wireless Power Transfer (WPT) technology has experienced rapid development in fields such as electric vehicles, medical implant devices, and renewable energy scheduling. However, the efficiency of WPT systems is often limited by dynamic load variations and losses caused by hard switching. This paper proposes a collaborative optimization strategy integrating Full-Bridge Step Density Modulation (FB-SDM) with Maximum Efficiency Point Tracking (MEPT). Through theoretical derivation of maximum efficiency conditions and Simulink simulation verification, the FB-SDM modulation strategy dynamically adjusts the modulation ratio via voltage feedback without adding additional DC-DC converters, effectively reducing switching losses and achieving maximum efficiency point tracking. Experimental results indicate that, compared to traditional PWM modulation, FB-SDM reduces switching losses by approximately 50% at an output power of 64.5 W. Moreover, the system efficiency remains above 90% across all power outputs. The research presented in this paper provides a novel solution for the efficient and reliable operation of WPT systems, demonstrating significant engineering application value.