Frequency Decrease Analysis of Resonant Wireless Power Transfer

Recent years have witnessed the booming development of resonant wireless power transfer (RWPT). Compared with conventional inductive power transfer, the frequency of RWPT is usually much higher. To reduce the resonant frequency while maintaining the transfer efficiency constant at the same transfer distances, two solutions are proposed and realized in this letter. Two fundamental structures for RWPT are analyzed and the expressions of the transfer efficiency are deduced. It is pointed out that the transfer quality factor and the load matching factor are two important factors of achieving high transfer efficiency. The larger the transfer quality factor, the higher the transfer efficiency. There is an optimal load matching factor to reach the highest transfer efficiency. The transfer efficiency can remain constant at the same distances if the transfer quality factor is kept at the same level and the load is matched. Theoretical calculations and experimental results provide a sound basis for decreasing frequency.