Fast Online Foreign Object Detection Method using Auxiliary Coils in Wireless Charging Systems

In inductive wireless power transfer systems, foreign object detection (FOD) is a vital function due to safety consideration. However, for existing products in the market, the integrated foreign object detection methods are either based on offline solutions, or online solutions with limited detection accuracy and speed. In this paper, an online foreign object detection method with a single auxiliary coil is proposed to provide high-speed high-accuracy protection for wireless charging systems. This method achieves detection without interruption of power transfer. Also, the detection circuit does not need an extra power supply, which minimizes the added cost. Finally, an example circuit is built, and corresponding simulation and experiment results demonstrate the feasibility and superior performance of the method.