8.3.16 WPC v1.2 Compliance – Foreign Object Detection

The bq51003 is a WPC v1.2 compatible device. To enable a Power Transmitter to monitor the power loss across the interface as one of the possible methods to limit the temperature rise of Foreign Objects, the bq51003 reports its Received Power to the Power Transmitter. The Received Power equals the power that is available from the output of the Power Receiver plus any power that is lost in producing that output power (the power loss in the Secondary Coil and series resonant capacitor, the power loss in the Shielding of the Power Receiver, the power loss in the rectifier). In WPC v1.2 specification, foreign object detection (FOD) is enforced. This means the bq51003 will send received power information with known accuracy to the transmitter.

WPC v1.2 defines Received Power as “the average amount of power that the Power Receiver receives through its Interface Surface, in the time window indicated in the Configuration Packet”.

To receive certification as a WPC v1.2 receiver, the Device Under Test (DUT) is tested on a Reference Transmitter whose transmitted power is calibrated, the receiver must send a received power determined by Equation 5:

This 250-mW bias ensures that system will remain interoperable.

WPC v1.2 Transmitter will be tested to see if they can detect reference Foreign Objects with a Reference receiver.

WPC v1.2 Specification will allow much more accurate sensing of Foreign Objects.