Low-Control-Complexity Peak-to-Peak Current Extremum-Based Synchronous Rectification for Wireless Power Transfer Systems

Wireless power transfer technology has been widely investigated and applied, benefiting from the galvanic isolation between the primary and secondary sides. However, the isolation makes synchronous rectification of the secondary-side rectifier challenging. To achieve synchronous rectification, a peak-to-peak current extremum-based synchronous rectification strategy is proposed. First, the relationship between the primary–secondary phase difference and the peak-to-peak rectifier output current is analyzed. The results reveal that the peak-to-peak current reaches its minimum at the synchronous condition. Second, a variable step-size hill-climbing algorithm is developed to search for the extremum of the peak-to-peak current, while a peak-to-peak current holding circuit reduces the requirements for high-speed sampling and real-time computation. Finally, a hardware prototype is developed to verify the proposed strategy. Experimental results demonstrate that synchronous rectification is successfully achieved under different coupling coefficients. The maximum power transfer efficiency is improved by 20.41 percentage points compared with diode-based uncontrolled rectification.