Apparatus and method for performing foreign object detection in wireless power transfer system
Provided are an apparatus and method for performing foreign object detection in a wireless power transfer system. The present specification discloses a method comprising receiving a digital ping from the wireless power transmitter; transmitting an identification and configuration packets to the wireless power transmitter; transmitting a foreign object detection (FOD) state packet which indicates a reference Q factor of the wireless power receiver to the wireless power transmitter; and receiving wireless power through magnetic coupling from the wireless power transmitter based on the foreign object detection result of the wireless power transmitter using the reference Q factor. Irrespective of individual characteristics of a wireless power receiver, accuracy and reliability of detecting a foreign object may be improved.
1. A method for testing foreign object detection performance of a wireless power receiver in a wireless power transfer system, the method comprising:
measuring a Q factor with respect to a wireless power receiver at a predetermined test position on a reference wireless power transmitter;
comparing the measured Q factor with a reference Q factor provided by the wireless power receiver; and
if the reference Q factor is larger than or equal to the minimum reference Q factor (Q ref min ) required for an arbitrary wireless power receiver compatible with the reference wireless power transmitter, and the measured Q factor belongs to an error range of the reference Q factor, determining a foreign object detection performance test of the wireless power receiver as being successful.
2. The method of claim 1 , wherein if the first Q factor is denoted as a threshold Q factor (Q ref,OX ) by which the representative foreign object is detected where a first Q factor (Q RX ) of a reference wireless power transmitter with respect to the arbitrary wireless power receiver in the absence of a nearby foreign object is the same as a second Q factor (Q RX,RFO ) of the reference wireless power transmitter with respect to the arbitrary wireless power receiver in the presence of a nearby representative foreign object (RFO), the minimum Q factor value is defined based on the threshold Q factor.
3. The method of claim 2 , wherein the minimum reference Q factor is defined as a value compensating the threshold Q factor for a Q factor measurement error.
4. The method of claim 3 , wherein the threshold Q factor ranges from 22 to 23, the Q factor measurement error lies within 10% of the threshold Q factor, and the minimum reference Q factor ranges from 24 to 26.
5. The method of claim 4 , wherein the threshold Q factor is 22.2.
6. The method of claim 1 , wherein, when ΔQ factor=second Q factor−first Q factor, the minimum reference Q factor is defined based on the first Q factor which satisfies ΔQ factor=0; the first Q factor is a Q factor of a reference wireless power transmitter with respect to the arbitrary wireless power receiver in the absence of a nearby foreign object; and the second Q factor is a Q factor of the reference wireless power transmitter with respect to the arbitrary wireless power receiver in the presence of a nearby representative foreign object.