In this brief, a high-efficiency wireless power transfer (WPT) system for electric vehicle charging application is studied and implemented. Series-series resonant topology with RF feedback design is adopted as the WPT dc-dc stage due to the advantages of circuit simplicity, easy analysis, and control. A 500-W laboratory prototype is built and tested to verify the feasibility of the proposed design. According to the experimental results, high wall-to-battery efficiency and unity power factor can be achieved over an air gap of 15 cm and maximum sliding distance of 10 cm under various power conditions and universal input voltage from 90VAC to 264VAC.

A novel hybrid mode control technique for phase-shift full-bridge (PSFB) converter is proposed in this paper. The proposed method will improve power efficiency under both the light-load and heavy-load conditions. The basic concept of the proposed control technique is to decrease the turns ratio to reduce the circulating current; hence results in lower circulating losses. However, the output voltage under heavy load may not be stabilized using phase-shift control if smaller turns ratio is utilized. Therefore, the proposed technique employs asymmetrical pulse-width modulation to achieve higher output voltage. To further improve the efficiency, an adaptive dead-time control method which determines the dead-time value according to the load level is also proposed. To validate the correctness and effectiveness of the proposed method, a 480-W PSFB converter is constructed and experiments are carried out accordingly. Comparing with conventional PSFB converter, the efficiency of the proposed method can be improved up to 3.2 %, 1.3 % and 0.6 % under light-load, 30 % load and full-load conditions, respectively.