Detection of device removal from a surface of a multi-coil wireless charging device

Patent metadata

Field	Value
Publication number	US-11296550-B2
Application number	US-202016936361-A
Country	US
Kind code	B2
Filing date	Jul 22, 2020
Priority date	Jul 23, 2019
Publication date	Apr 5, 2022
Grant date	Apr 5, 2022

Abstract

Systems, methods and apparatus for wireless charging are disclosed. A charging device has a plurality of charging cells provided on a charging surface, a charging circuit and a controller. The controller may be configured to cause the charging circuit to provide a charging current to a resonant circuit when a receiving device is placed on the charging surface, provide a measurement slot by causing the charging circuit to decrease or terminate the charging current for a period of time and determine whether the receiving device has been removed from the charging surface based on measurement of a characteristic of the resonant circuit during the measurement slot. The characteristic of the resonant circuit may be representative of electromagnetic coupling between a transmitting coil in the resonant circuit and a receiving coil in the receiving device.

First claim

What is claimed is:

1. A method for operating a charging device, comprising:
transferring power to a receiving device in accordance with a charging configuration, including providing a charging current to a resonant circuit according to the charging configuration, the charging configuration being generated after determining that the receiving device has been placed at a first location on a charging surface of the charging device;
detecting a change or rate of change in voltage or current level associated with the resonant circuit while transferring power to the receiving device;
initiating a measurement slot by terminating the charging current for a period of time after detecting the change or rate of change in the voltage or current level;
determining whether the receiving device has been removed from the charging surface based on a change in Q-factor of the resonant circuit determined using measurements obtained during the measurement slot;
resuming power transfer to the receiving device in accordance with the charging configuration by resuming the charging current to the resonant circuit when the Q-factor of the resonant circuit indicates that the receiving device remains on the charging surface; and
discontinuing power transfer to the receiving device after determining that the receiving device has been moved from the first location.

2. The method of claim 1 , wherein the measurement slot is initiated when the rate of change in the voltage or current level associated with the resonant circuit exceeds a threshold rate of change.

3. The method of claim 1 , wherein the resonant circuit includes a transmitting coil.

4. The method of claim 3 , wherein the Q factor of the resonant circuit is indicative of coupling between the transmitting coil and a receiving coil in the receiving device.

5. The method of claim 1 , wherein the receiving device is determined to have been removed from the charging surface based on a comparison of the Q-factor of the resonant circuit with a reference Q-factor.

6. The method of claim 3 , further comprising:
measuring a rate of decay of energy stored in the resonant circuit; and
determining that the receiving device has been removed from the charging surface when a difference between the rate of decay of the energy stored in the resonant circuit and a rate of decay measured before the receiving device is placed on the charging surface exceeds a threshold difference.

7. The method of claim 1 , further comprising:
receiving measurements from one or more sensors in the charging surface; and
providing the measurement slot when one of the measurements indicates physical removal of the receiving device.

8. The method of claim 7 , wherein the one or more sensors include a strain measuring sensor.

9. The method of claim 7 , wherein the one or more sensors include an accelerometer.

10. The method of claim 7 , wherein the one or more sensors comprise an infrared or ultrasonic sensing element.

11. The method of claim 7 , wherein the one or more sensors comprise a hall-effect device.

12. A charging device, comprising:
a charging circuit;
a resonant circuit coupled to the charging circuit; and
a controller configured to:
cause the charging circuit to provide a charging current to the resonant circuit when a receiving device is placed at a first location on a charging surface of the charging device;
detect a change or rate of change in voltage or current level associated with the resonant circuit while transferring power to the receiving device;
initiate a measurement slot by causing the charging circuit to terminate the charging current for a period of time;
determine whether the receiving device has been removed from the charging surface based on a change in Q-factor of the resonant circuit determined using measurements obtained during the measurement slot;
cause the charging circuit to resume power transfer to the receiving device in accordance with the charging configuration by resuming the charging current to the resonant circuit when the Q-factor of the resonant circuit indicates that the receiving device remains on the charging surface; and
cause the charging circuit to discontinue power transfer to the receiving device after determining that the receiving device has been moved from the first location.

13. The charging device of claim 12 , wherein the controller is further configured to:
initiate the measurement slot after determining that the change or rate of change in the voltage or current level associated with the resonant circuit exceeds a threshold rate of change.

14. The charging device of claim 12 , wherein the resonant circuit includes a transmitting coil.

15. The charging device of claim 14 , wherein the Q-factor of the resonant circuit is indicative of coupling between the transmitting coil and a receiving coil in the receiving device.

16. The charging device of claim 12 , wherein the receiving device is determined to have been removed from the charging surface based on a comparison of the Q-factor of the resonant circuit with a reference Q-factor.

17. The charging device of claim 14 , wherein the controller is further configured to:
measure a rate of decay of energy stored in the resonant circuit; and
determine that the receiving device has been removed from the charging surface when a difference between the rate of decay of the energy stored in the resonant circuit and a rate of decay measured before the receiving device is placed on the charging surface exceeds a threshold difference.

18. The charging device of claim 12 , further comprising:
one or more sensors configured to measure a change in a physical characteristic affected by presence of the receiving device, wherein the controller is further configured to:
receive measurements from the one or more sensors; and
provide the measurement slot when one of the measurements indicates physical removal of the receiving device.

19. The charging device of claim 18 , wherein the one or more sensors include a strain measuring sensor.

20. The charging device of claim 18 , wherein the one or more sensors include an accelerometer.

21. The charging device of claim 18 , wherein the one or more sensors comprise an infrared or ultrasonic sensing element.

22. The charging device of claim 18 , wherein the one or more sensors comprise a hall-effect device.

Assignees

• Aira Inc

Inventors

• Goodchild Eric Heindel
• Winters John
• Scott James

Classifications

• H02J7/963

  in response to battery voltage gradient · CPC title

• H02J7/953

  in response to charge current gradient · CPC title

• H02J7/80

  including monitoring or indicating arrangements · CPC title

• H02J50/005 Primary

  Mechanical details of housing or structure aiming to accommodate the power transfer means, e.g. mechanical integration of coils, antennas or transducers into emitting or receiving devices · CPC title

• H02J50/90

  involving detection or optimisation of position, e.g. alignment · CPC title