Planar Double-Winding Foreign Object Detection for the EV Wireless Charging System Based on Time-Division Multiplexing

Metal object detection (MOD) and living object detection (LOD) are essential for ensuring the safe operation of the electric vehicle (EV) wireless charging system. Since most MOD or LOD single-type systems protect the EV wireless charging system incomprehensively, the existing MOD and LOD shared system has problems such as difficulty in acquiring detection signal, and low accuracy for small-sized living objects (LOs). Thus, this article proposes a planar double-winding foreign object detection (FOD) system based on the time-division multiplexing control strategy. First, the planar double-winding FOD system structure is given, and the time-division multiplexing FOD mode switching as well as FOD judgement principle are analyzed. Second, the phase variation of bandpass filter output voltage in the planar double-winding FOD system is analyzed. Third, the sensing coil structure and detecting circuit parameters are optimized. Finally, an experimental platform is built to verify the feasibility. The results show that when MOD and LOD phase thresholds are set to 3<inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> and 20<inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula>, respectively, the phase variation is −21.3<inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula>, −27.9<inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula>, −7<inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula>, and 48.3<inline-formula><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula> for a copper plate, aluminum plate, iron plate of 40 × 40 mm² and one hand. Therefore, the phase variation is larger than the phase threshold, which can effectively detect MO and LO.