A Blind-Spot-Free Metal Object Detection System with Reconfigurable Alternating DD Structures for Wireless Charging Systems

In wireless power transfer (WPT) systems, the entry of metal objects (MOs) can lead to the generation of eddy currents within the MOs due to the strong magnetic field, posing a fire risk. To address this challenge, this paper proposes a reconfigurable metal object detection (MOD) circuit design, which aims to achieve blind-spot-free MOD using as few coils as possible. The reconfigurable circuits allow adjacent coils to be reconfigured into a bipolar (DD) structure, which can achieve detection without blind spots and ensure that the detection coils are always decoupled from the WPT system. An experimental platform for MOD is constructed in this paper, and the results show that the MOD system has extremely weak coupling with the WPT system, enabling effective MOD blind spot detection even when the power transmission coil is displaced by 50 mm, and the proposed MOD system achieves a detection height of 7 mm.