Device movement detection in a multi-coil charging surface

1. A method for operating a charging surface in a wireless charging device, comprising: providing a charging current to at least one transmitting coil in a plurality of transmitting coils that is deployed across the charging surface, wherein the charging current causes a wireless transfer of power by the at least one transmitting coil to a chargeable device located on the charging surface, and wherein each of the plurality of transmitting coils is configured to wirelessly transmit power through the charging surface when activated by an alternating current;

measuring voltages across three or more transmitting coils in the charging surface; and determining that the chargeable device is in motion across the charging surface based on changes in the voltages measured across the three or more of the plurality of transmitting coils;

determining a rate of change of a signal representative of the voltage measured across a first transmitting coil in the three or more transmitting coils; and determining a direction of motion of the chargeable device across the charging surface based on a comparison of the rate of change of the signal with a threshold value.

2. The method of claim 1 , further comprising:

determining a direction of motion of the chargeable device across the charging surface based on the changes in the voltages measured across the three or more transmitting coils.

3. The method of claim 1 , further comprising:

determining that the chargeable device is moving away from a first active transmitting coil when the voltage measured across the first active transmitting coil is increasing; and

determining that the chargeable device is moving toward an adjacent transmitting coil when the voltage measured across the adjacent transmitting coil is decreasing.

4. The method of claim 1 , further comprising:

determining a direction of motion that indicates that the chargeable device is moving away from a first active transmitting coil and toward an adjacent transmitting coil when the voltage measured across the first active transmitting coil is increasing and the voltage measured across the adjacent transmitting coil is decreasing; and

redirecting the charging current from the first active transmitting coil to the adjacent transmitting coil based on the determined direction of motion.

5. The method of claim 1 , wherein the chargeable device is approaching the transmitting coil when the threshold value exceeds the rate of change, and wherein the chargeable device is receding from the transmitting coil when the rate of change exceeds the threshold value.

6. The method of claim 1 , wherein the chargeable device is approaching the transmitting coil when the threshold value exceeds the rate of change, and wherein the chargeable device is receding from the transmitting coil when the rate of change exceeds the threshold value.

7. The method of claim 1 , further comprising:

determining rate of change of a plurality of signals, each signal representative of the voltage measured across one of the three or more transmitting coils; and

determining direction of motion of the chargeable device in two-dimensional space device across the charging surface based on a comparison of a threshold value with rates of change of the plurality of signals.

8. The method of claim 7 , further comprising:

determining direction of motion of the chargeable device in three-dimensional space based on the comparison of the threshold value with rates of change of the plurality of signals.

9. The method of claim 7 , further comprising:

modifying a charging configuration based on the direction of motion of the chargeable device; and

providing the charging current to a different transmitting coil based on a modification to the charging configuration.

10. A wireless charging device, comprising:

a plurality of charging cells provided at a charging surface of the wireless charging device; and

a controller configured to:

provide a charging current to at least one transmitting coil in a plurality of transmitting coils that is deployed across the charging surface, wherein the charging current causes a wireless transfer of power by the at least one transmitting coil to a chargeable device located on the charging surface, and wherein each of the plurality of transmitting coils is configured to wirelessly transmit power through the charging surface when activated by an alternating current;

measure voltages across three or more transmitting coils in the charging surface; and determine that the chargeable device is in motion across the charging surface based on changes in the voltages measured across the three or more of the plurality of transmitting coils;

wherein the controller is further configured to: determine a rate of change of a signal representative of the voltage measured across a first transmitting coil in the three or more transmitting coils; and determine a direction of motion of the chargeable device across the charging surface based on a comparison of the rate of change of the signal with a threshold value.

11. The wireless charging device of claim 10 , wherein the controller is further configured to:

determine a direction of motion of the chargeable device across the charging surface based on the changes in the voltages measured across the three or more transmitting coils.

12. The wireless charging device of claim 10 , wherein the controller is further configured to:

determine that the chargeable device is moving away from a first active transmitting coil when the voltage measured across the first active transmitting coil is increasing; and

determine that the chargeable device is moving toward an adjacent transmitting coil when the voltage measured across the adjacent transmitting coil is decreasing.

13. The wireless charging device of claim 10 , wherein the controller is further configured to:

determine a direction of motion that indicates that the chargeable device is moving away from a first active transmitting coil and toward an adjacent transmitting coil when the voltage measured across the first active transmitting coil is increasing and the voltage measured across the adjacent transmitting coil is decreasing; and

redirect the charging current from the first active transmitting coil to the adjacent transmitting coil based on the determined direction of motion.

14. The wireless charging device of claim 10 , wherein the chargeable device is approaching the transmitting coil when the threshold value exceeds the rate of change, and wherein the chargeable device is receding from the transmitting coil when the rate of change exceeds the threshold value.

15. The wireless charging device of claim 10 , wherein the controller is further configured to: determine that the chargeable device is stationary with respect to the transmitting coil when rate of change is substantially equal to the threshold value.

16. The wireless charging device of claim 10 , wherein the controller is further configured to:

determine rate of change of a plurality of signals, each signal representative of the voltage measured across one of the three or more transmitting coils; and

determine direction of motion of the chargeable device in two-dimensional space across the charging surface based on a comparison of a threshold value with rates of change of the plurality of signals.

17. The wireless charging device of claim 16 , wherein the controller is further configured to:

determine direction of motion of the chargeable device in three-dimensional space based on the comparison of the threshold value with rates of change of the plurality of signals.

18. The wireless charging device of claim 16 , wherein the controller is further configured to:

modify a charging configuration based on the direction of motion of the chargeable device; and

provide the charging current to a different transmitting coil based on a modification to the charging configuration.