Foreign object detection using heat sensitive material and inductive sensing
In certain aspects, an enclosure for a wireless power transfer pad is disclosed. The enclosure includes a cover shell configured to be positioned over a portion of the wireless power transfer pad configured to face a wireless power receiver when wirelessly transferring power, wherein at least a portion of the cover shell is made of a heat resistant material.
1. An apparatus comprising:
a sensing system having one or more sense coils configured to inductively sense a foreign object via a magnetic field;
a controller coupled to the sensing system, the controller configured to measure an electrical characteristic of the one or more sense coils and determine a presence of the foreign object based on a change of the measured electrical characteristic; and
an enclosure comprising a cover shell configured to be positioned over a portion of a wireless power transfer pad configured to face a wireless power receiver when wirelessly transferring power, wherein at least a portion of the cover shell is made of a heat resistant material configured to protect the sensing system against damage from the foreign object.
2. The apparatus of claim 1 , further comprising a back plate.
3. The apparatus of claim 1 , wherein the heat resistant material comprises a nylon resin.
4. The apparatus of claim 1 , wherein the heat resistant material comprises a perfluoroelastomer or a polymerized siloxane.
5. The apparatus of claim 1 , wherein the heat resistant material comprises glass reinforcement or a reinforced plastic.
6. The apparatus of claim 1 , wherein the heat resistant material comprises carbon-fibre reinforcement.
7. The apparatus of claim 1 , wherein the heat resistant material comprises a structural composite.
8. The apparatus of claim 1 , wherein the heat resistant material comprises a ceramic matrix composite.
9. The apparatus of claim 1 , wherein the heat resistant material comprises amorphous quartz glass.
10. The apparatus of claim 1 , wherein the heat resistant material is at least partially transparent to electromagnetic waves.
11. The apparatus of claim 1 , wherein the portion of the cover shell comprises a surface of the cover shell.
12. The apparatus of claim 1 , wherein the portion of the cover shell comprises the entire cover shell.
13. The apparatus of claim 1 , wherein the portion of the cover shell is embedded in the cover shell.
14. The apparatus of claim 1 , wherein the portion of the cover shell comprises one or more tiles.
15. The apparatus of claim 1 , wherein the cover shell further comprises a foreign object detection mechanism.
16. The apparatus of claim 1 , wherein the cover shell further comprises a thermal insulation layer.
17. The apparatus of claim 1 , wherein the heat resistant material has a melting point higher than 200° C. and is configured to withstand a temperature reached by the foreign object higher than 200° C.
18. The apparatus of claim 1 , wherein the electrical characteristic measured by the controller comprises one or more of an impedance, a resistance, an induced voltage, and an impulse response.
19. The apparatus of claim 1 , wherein the controller determines the presence of the foreign object by correlating the measured electrical characteristic with an output of another foreign object detection system.
20. The apparatus of claim 1 , wherein the controller determines the presence of the foreign object by correlating the measured electrical characteristic with a level of an alternating magnetic field generated by the wireless power transfer pad.