A Switchable Dual-Frequency LCC-S-S Compensated Three-Coil WPT System for Mobile Desktop Charging with Constant Current and Constant Voltage Outputs

Wireless power transfer (WPT) system with three-coil has potential application prospect in mobile desktop charging, since it can effectively increase the transmission distance. In practical applications, the typical constant current (CC) and constant voltage (CV) two-stage charging mode for batteries is widely utilized. However, the batteries' equivalent resistance remarkably varies during the charging process, to realize both CC and CV outputs with different load conditions is a confronting problem for WPT system. To address the issue, a hybrid LCC-S-S compensation topology with an ac switch is proposed in this article. The CC/CV output characteristics can be fulfilled through the alternation of two fixed system operation frequencies and the switching of an ac switch at the receiver side. Besides, the zero phase angle (ZPA) conditions are also been met at the same time. A 50 W output experimental prototype is implemented to validate relevant theoretical analysis. The experimental results show that the CC/CV output characteristics are well maintained while the load resistance undergoes widely variation. Moreover, the ZPA operation can be achieved when receiver coil is misaligned. During the whole charging procedure, the peak power transfer efficiency can reach 91.9%.