Design of Wireless charging System with Inherent Current Regulation and High Misalignment Tolerance

Abstract

This paper proposes a simplified inductive power transfer (IPT) based electric vehicle (EV) battery charging architecture. This embeds battery charging control within the resonant compensation network, eliminating the need for conventional current-control loops and secondary DC–DC conversion stages. Unlike state-of-the-art IPT chargers, the proposed system exploits the inherent current-source characteristics of a well-tuned series–series (SS) compensation topology to achieve passive constant-current charging under battery state of charge (SoC) variation up to 70 %. Beyond 70 % SoC, the charging power is regulated through controlled inverter frequency detuning, enabling a smooth transition to constant-voltage charging without additional hardware. The design of the compensator is to meet the charging ampere hour (Ah) requirements of the chosen battery. The integrated control strategy embeds multi-stage battery charging functionality directly into the IPT power stage, reducing control complexity and component count while maintaining stable operation. The proposed design demonstrates strong tolerance to coil misalignment, delivering a reasonably good power under a lateral misalignment of 9 cm. The concept is validated experimentally using a 300 W, 48 V prototype, charging a 48 V, 35 Ah battery pack which achieves an overall efficiency of 82 % and maintains 92.56 % power transfer capability under maximum misalignment. Simulation results using LTspice shown in the results and discussion section closely match the experimental results.