Based on the output signals of multi-coil sensors to determine is there any metal foreign object within wireless charging system. This developed foreign object detection (FOD) method can be used both before and during wireless charging, and will not affect the main system. The property of developed FOD is able to detect a foreign metal object as small as one dollar coin within 2 sec. Once detecting a metal object, the wireless power transmission will be interrupted immediately to ensure the system safety.

1.Detection time：2 seconds
2.Detection object：metal object lager than one dollar coin (diameter 2cm)
3.Applicable condition：before or under charging

Electric vehicle, wireless charging system

Wireless charging function is convenience and safe for electronics products and power devices doing charging. For an example of electric vehicle, just start wireless charging after parking without charging gun operation. However, there is a gap between the Tx and Rx coils of wireless charging system. The metallic foreign object invasion to a contactless charging device like such system might lead to heat or even fire. Therefore, the FOD is developed for improving the system safety and practicality.