A Systematic Design Method for Wireless Power Transfer Systems Using the High-Order Filter Theory

One of the main factors that limit the practical applications of a wireless power transfer (WPT) system is its possible low-power transfer efficiency (PTE) against changes in distances and misalignments between the Rx and Tx coils, as well as changes in the loads. Although many methods have been proposed to address the issue, a systematic and optimal design method is still missing and much desirable. This article further extends our previous work that uses the first-order filter design approach to a high-order approach with a multicoil system. We first develop the correspondences between the high-order Chebyshev filter and a multicoil WPT system; we then develop a robust design approach to obtaining the circuit parameters of the WPT systems. Both the simulation and measurement results verify the effectiveness of the proposed design methods. They show that by using the second-order Chebyshev bandpass filter design method that involves a four-coil WPT system, we can achieve the PTE at about 75% within specific ranges of changes in distance, misalignments, and load variations, while by using the third-order Chebyshev bandpass filter design method that involves a six-coil WPT system, we can achieve the PTE at about 80% for within specific ranges of changes in distance, misalignments, and load variation.