Robust foreign objects detection
An apparatus and method for performing foreign object detection for a wireless power transmitter. A matching network and transmit coil are energized, and a resonance is excited. The resonance is allowed to decay. A temporal characteristic of the decay is measured. The temporal characteristic is analyzed to determine whether a foreign object is coupled to an electromagnetic field generated by the transmit coil.
1. A foreign object detection method for a wireless power transmitter having a matching network and transmit coil, the method comprising:
measuring a quality factor of the transmit coil; and
analyzing the quality factor to determine whether a foreign object is coupled to an electromagnetic field generated by the transmit coil,
wherein the wireless power transmitter transfers sufficient energy to a wireless power receiver to charge a rectifier filter capacitor of the wireless power receiver and reverse bias rectifier diodes of the wireless power receiver.
2. The foreign object detection method of claim 1 , wherein the analyzing of the quality factor comprises comparing the quality factor to a threshold.
3. The foreign object detection method of claim 2 , wherein the threshold is at least in part derived from a quality factor value provided to the wireless power transmitter by the wireless power receiver.
4. The foreign object detection method of claim 1 , further comprising determining whether to allow or inhibit wireless power transfer based on the analyzing.
5. The foreign object detection method of claim 1 , wherein the measuring of the quality factor comprises energizing the matching network by transferring a first energy level in a first period of time and a second energy level in a second period of time following the first period of time, wherein the first energy level is higher than the second energy level.
6. The foreign object detection method of claim 5 , wherein the measuring the quality factor further comprises allowing a resonance of the matching network to decay and measuring a temporal characteristic of the decay.
7. A foreign object detection method for a wireless power transmitter having a matching network and transmit coil, the method comprising:
energizing the matching network and transmit coil and exciting resonance between the matching network and transmit coil;
measuring a quality factor of the transmit coil; and
comparing the quality factor to a threshold to determine whether a foreign object is coupled to an electromagnetic field generated by the transmit coil.
8. The foreign object detection method of claim 7 , wherein the threshold is at least in part derived from a quality factor value provided to the wireless power transmitter by a wireless power receiver.
9. The foreign object detection method of claim 7 , further comprising:
determining whether to allow or inhibit wireless power transfer based on the comparing of the quality factor to the threshold.
10. An apparatus for driving a wireless power transmitter and performing foreign object detection, the apparatus comprising:
a controller configured to measure a quality factor of a transmit coil of the wireless power transmitter and analyze the quality factor to determine whether a foreign object is coupled to an electromagnetic field generated by the transmit coil,
wherein the wireless power transmitter transfers sufficient energy to a wireless power receiver to charge a rectifier filter capacitor of the wireless power receiver and reverse bias rectifier diodes of the wireless power receiver.
11. The apparatus of claim 10 , wherein the controller is configured to analyze the quality factor by comparing the quality factor to a threshold.
12. The apparatus of claim 11 , wherein the threshold is at least in part derived from a quality factor value provided to the wireless power transmitter by the wireless power receiver.
13. The apparatus of claim 10 , wherein the controller is configured to determine whether to allow or inhibit wireless power transfer based on analyzing the quality factor.
14. The apparatus of claim 10 , wherein the controller is configured to measure the quality factor through energizing a matching network by transferring a first energy level in a first period of time and a second energy level in a second period of time following the first period of time, wherein the first energy level is higher than the second energy level.
15. The apparatus of claim 14 , wherein the controller is configured to allow a resonance of the matching network to decay and measure a temporal characteristic of the decay.
16. An apparatus for driving a wireless power transmitter and performing foreign object detection, the apparatus comprising:
a drive circuit configured to energize a matching network and transmit coil of the wireless power transmitter and excite resonance between the matching network and transmit coil; and
a controller configured to measure a quality factor of the transmit coil and analyze the quality factor by comparing the quality factor to a threshold to determine whether a foreign object is coupled to an electromagnetic field generated by the transmit coil.
17. The apparatus of claim 16 , wherein the threshold is at least in part derived from a quality factor value provided to the wireless power transmitter by a wireless power receiver.
18. The apparatus of claim 16 , wherein the controller is configured to determine whether to allow or inhibit wireless power transfer based on the comparing of the quality factor to the threshold.