Obtaining Maximum Efficiency of Inductive Power-Transfer System by Impedance Matching Based on Boost Converter

This article presents a maximum efficiency tracking method for an inductive power-transfer (IPT) system based on a Boost dc-dc converter. Impedance matching (IM) is achieved by maintaining the equivalent load impedance to be constant against load variations. The expression of the optimal equivalent load impedance corresponding to the maximum system-transfer efficiency is derived, and the impedance-transfer characteristics of the Boost converter in both continuous conduction mode (CCM) and discontinuous conduction mode (DCM) are analyzed. The duty cycle of the Boost converter is controlled to maintain the optimal equivalent load with extended range in DCM mode, and the switching frequency of the Boost converter is further adjusted to improve the accuracy of the IM. Both simulation and experimental results have demonstrated that the proposed IM method can help achieve the maximum power-transfer efficiency under a wide range of load variations.