What is Foreign Object Detection?

In wireless charging, metal objects that get close to a wireless power transfer system may couple a portion of an electromagnetic field and heat up. The detection of foreign objects around the system (metallic or magnetic objects) is of key importance due to their ability to absorb energy from the wireless power supply field in the form of heat (parasitic heating) and possibly become a hazard.

Simulations and experiments have shown that just 500 to 1000 mW of power dissipated in a metal object like a coin, a paper clip or gold ring, can raise the object’s temperature above 80°C.

Most wireless charging systems today have foreign object detection technology which is used to detect the presence of foreign metal objects around the wireless charging system and inhibit wireless power transfer when energy leakage exceeds a predetermined level.

Click here to read the white paper on Foreign Object Detection. This paper presents the development and experimental validation of the Power Loss Detection method (PLD) which is one way to detect the presence of a foreign object that is absorbing energy.