Analysis of Minimum Power Loss in Series-Series Compensated Wireless Power Transfer System under ZVS Conditions

Tight voltage/current regulation and high efficiency are fundamental objectives of wireless power transfer systems (WPTSs) as power supplies. Although the well-established impedance matching control attempts to achieve high efficiency, the associated extra dc-dc converters or hard switching in WPTSs reduce the overall system efficiency, particularly for high-power applications. Commonly, achieving ZVS of all switches is an effective way to improve the transfer efficiency in a WPTS. In this paper, under ZVS conditions of all switches, the distribution of the system power loss is investigated and the optimal operating point with the minimum power loss is derived through detailed power loss analysis. A 500-W experimental prototype has been built to verify the correctness of derivation. With a coupling coefficient k of 0.2 or 0.15, the maximum transfer efficiency of the whole system can reach 96.8% or 95.0% under the power rating of 288W (rated load) as well as 92.4% or 88.7% in the case of light load (9% of 288W).