Energy transfer optimization by detecting and mitigating magnetic saturation in wireless charging with foreign object detection

1. A method for optimizing wireless charging of a mobile device by a wireless charger, the method comprising:

determining whether a first power loss for a first wireless transmission of power from the wireless charger to the mobile device exceeds a threshold;

determining whether magnetic saturation occurred in at least one of the mobile device and the wireless charger during the first wireless transmission of power from the wireless charger to the mobile device in response to a determination that the first power loss exceeds the threshold; and

when magnetic saturation is determined to have occurred, successively reducing transmit power in the wireless charger until reaching an operating wireless transmit power, wherein neither the mobile device nor the wireless charger is in magnetic saturation at the operating wireless transmit power.

2. The method of claim 1 , wherein the first power loss is a difference between the operating wireless transmit power and a power induced in the mobile device by the wireless charger at the operating wireless transmit power, the method further comprising when the first power loss exceeds the threshold:

determining that a foreign object is present on at least one of the wireless charger and the mobile device; and

disabling charging by the wireless charger.

3. The method of claim 1 , wherein determining whether magnetic saturation occurred comprises determining that magnetic saturation has occurred when a percentage difference between the first power loss and a second power loss is not equal to a fixed percentage within a defined margin of error, wherein the second power loss is determined for a second wireless transmission of power, and wherein a power measured in the wireless charger during the second wireless transmission of power is the fixed percentage less than a power measured in the wireless charger during the first wireless transmission of power.

4. The method of claim 3 , wherein the first power loss is a difference between the power measured in the wireless charger during the first wireless transmission of power and a power induced in the mobile device by the wireless charger during the first wireless transmission of power, and wherein the second power loss is a difference between the power measured in the wireless charger during the second wireless transmission of power and a power induced in the mobile device by the wireless charger during the second wireless transmission of power.

5. The method of claim 3 , further comprising when the percentage difference is equal to the fixed percentage within the defined margin of error, determining that a foreign object is present between the wireless charger and the mobile device.

6. The method of claim 1 , wherein the transmit power in the wireless charger is successively reduced until reaching the operating wireless transmit power by decreasing a current in a coil in the wireless charger.

7. The method of claim 1 , further comprising when the first power loss does not exceed the threshold:

determining that a foreign object is not present; and

maintaining the operating wireless transmit power.

8. A method for optimizing wireless charging of a mobile device by a wireless charger, the method comprising:

determining whether magnetic saturation occurred in at least one of the mobile device and the wireless charger during a first wireless transmission of power from the wireless charger to the mobile device based on a percentage difference between a first power loss and a second power loss, wherein the first power loss is determined for the first wireless transmission of power from the wireless charger to the mobile device, wherein the second power loss is determined for a second wireless transmission of power from the wireless charger to the mobile device; and

when magnetic saturation is determined to have occurred, successively reducing transmit power in the wireless charger until reaching an operating wireless transmit power, wherein neither the mobile device nor the wireless charger is in magnetic saturation at the operating wireless transmit power.

9. The method of claim 8 , wherein the power of the second wireless transmission is reduced by a fixed percentage relative to the power of the first wireless transmission, the method further comprising, when the percentage difference is equal to the fixed percentage within the defined margin of error, determining that a foreign object is present on at least one of the wireless charger and the mobile device.

10. The method of claim 8 , wherein the power of the second wireless transmission is reduced by the fixed percentage relative to the power of the first wireless transmission by decreasing a current in a coil in the wireless charger.

11. The method of claim 8 , further comprising, when magnetic saturation has occurred, determining a third power loss in a third wireless transmission of power to the mobile device, wherein the power of the third wireless transmission is reduced by a second fixed percentage relative to the power of the second wireless transmission.

12. The method of claim 11 , further comprising:

determining a second percentage difference between the second power loss and the third power loss; and

when the second percentage difference is equal to the second fixed percentage within the defined margin of error, determining that neither the mobile device nor the wireless charger is in magnetic saturation.

13. The method of claim 12 , further comprising, when neither the mobile device nor the wireless charger is in magnetic saturation:

comparing the third power loss to a threshold;

when the third power loss does not exceed the threshold, determining that no foreign object is present on at least one of the wireless charger and the mobile device; and

when the third power loss does not exceed the threshold, maintaining a current in a coil in the wireless charger at a level that was attained for the third wireless transmission.

14. The method of claim 12 , further comprising, when the second percentage difference is not equal, within the defined margin of error, to the second fixed percentage:

determining that at least one of the mobile device and the wireless charger is still in magnetic saturation; and

decreasing a current in a coil in the wireless charger by successive increments.

15. A wireless charger comprising:

a primary coil; and

a processor coupled to the primary coil and configured to:

determine whether magnetic saturation has occurred in at least one of the primary coil and a mobile device being charged by the wireless charger during a first wireless transmission of power from the wireless charger to the mobile device based on a percentage difference between a first power loss and a second power loss, wherein the first power loss is determined for the first wireless transmission of power from the wireless charger to the mobile device, wherein the second power loss is determined for a second wireless transmission of power from the wireless charger to the mobile device; and

successively reduce current in the primary coil until reaching an operating wireless transmit power when magnetic saturation has occurred in at least one of the primary coil and the mobile device, wherein neither the primary coil nor the mobile device is in magnetic saturation at the operating wireless transmit power.

16. The wireless charger of claim 15 , wherein the processor is further configured to, when the first power loss exceeds a threshold:

determine that a foreign object is present between the wireless charger and the mobile device; and

disable charging by the wireless charger.

17. The wireless charger of claim 15 , wherein a power measured in the wireless charger during the second wireless transmission of power is a fixed percentage less than a power measured in the wireless charger during the first wireless transmission of power, and wherein the processor is further configured to determine that magnetic saturation has occurred when the percentage difference is not equal to the fixed percentage within a defined margin of error.

18. The wireless charger of claim 15 , wherein the first power loss is a difference between the power measured in the wireless charger during the first wireless transmission of power and a power induced in the mobile device by the wireless charger during the first wireless transmission of power, and wherein the second power loss is a difference between the power measured in the wireless charger during the second wireless transmission of power and a power induced in the mobile device by the wireless charger during the second wireless transmission of power.

19. The wireless charger of claim 15 , wherein a power measured in the wireless charger during the second wireless transmission of power is a fixed percentage less than a power measured in the wireless charger during the first wireless transmission of power, and wherein the processor is further configured to, when the percentage difference is equal to the fixed percentage within the defined margin of error:

determine that a foreign object is present between the wireless charger and the mobile device; and

disable charging by the wireless charger.

20. The wireless charger of claim 15 , wherein a power measured in the wireless charger during the second wireless transmission of power is a fixed percentage less than a power measured in the wireless charger during the first wireless transmission of power, and wherein the processor is further configured to decrease a current in the primary coil to reduce the power measured in the wireless charger during the second wireless transmission of power by the fixed percentage relative to the power measured in the wireless charger during the wireless transmission of power.