Foreign object detection

• US 10,432,036 B2
• Filed: 10/10/2017
• Issued: 10/01/2019
• Est. Priority Date: 10/26/2016
• Status: Active Grant

• Current Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Original Assignee: NXP USA, Inc. (NXP Semiconductors NV)
• Inventors: Li, Gang, Chen, Fei, Liu, Yuanhui
• Primary Examiner(s): Diao, M Baye
• Application Number:
  US15/728,882
• Publication Number:
  US 20180115197A1
• Time in Patent Office: 721 Days
• Field of Search: 320108
• CPC Class Codes: G01S 13/04 Systems determining presence of a target based on relative movement of target G01S13/56
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/402 the two or more transmitting or the two or more receiving devices being integrated in the same unit, e.g. power mats with several coils or antennas with several sub-antennas
• CPC Class Codes: H02J 50/60 responsive to the presence of foreign objects, e.g. detection of living beings
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 7/00034 Charger exchanging data with an electronic device, i.e. telephone, whose internal battery is under charge

Abstract

A set of initialization parameters are generated for a wireless charging device. Parameters of an antenna circuit connected to an output of the control circuit are measured. The antenna circuit is modelled as first and second virtual antenna portions. The presence of a foreign object is detected by receiving, from a receiver device, characteristics for the antenna circuit and by measuring second parameters of the antenna circuit. The measured second parameters and the initialization parameters are used to determine characteristics for the first virtual antenna portion. A foreign object is detected based upon a comparison of the received characteristics for the antenna circuit and the determined characteristics for the first virtual antenna portion.

Claims

1. A method comprising:

generating a set of initialization parameters for a control circuit of a wireless charging device by;

measuring first parameters of an antenna circuit connected to an output of the control circuit; and

modeling the antenna circuit as a first virtual antenna portion and a second virtual antenna portion by assigning predetermined characteristics to the first virtual antenna portion and determining characteristics of the second virtual antenna portion based upon the first parameters; and

detecting the presence of a foreign object by;

receiving, from a receiver device, reference characteristics for the antenna circuit;

measuring second parameters of the antenna circuit;

determining, by fixing the characteristics of the second virtual antenna portion, the characteristics for the first virtual antenna portion indicated by the second parameters; and

detecting the foreign object based upon a comparison of the reference characteristics for the antenna circuit and the characteristics for the first virtual antenna portion indicated by the second parameters.

2. The method of claim 1,

wherein the first and second parameters of the antenna circuit include a center frequency and a quality factor of the antenna circuit.

3. The method of claim 1,

wherein the predetermined characteristics assigned to the first virtual antenna portion include a quality factor.

4. The method of claim 3,

wherein the reference characteristics include a reference quality factor.

5. The method of claim 1,

wherein the measuring first and second parameters of the antenna circuit includes applying an excitation signal to cause the antenna circuit to oscillate.

6. The method of claim 5,

wherein the antenna circuit forms an LC oscillator circuit and the measuring the first and second parameters further includes and measuring a voltage or current of the LC oscillator circuit to determine a quality factor of the antenna circuit.

7. The method of claim 1,

wherein the first virtual antenna portion includes a portion of a parasitic resistance of an antenna coil of the antenna circuit.

8. The method of claim 7,

wherein the second virtual antenna includes another portion of the parasitic resistance of the antenna coil.

9. The method of claim 7,

wherein the characteristics of the second virtual antenna portion include another portion of the parasitic resistance of the antenna coil and a parasitic resistance of a capacitor of the antenna circuit.

10. A device for wireless charging of a remote device, the device comprising:

a transmitter circuit configured to;

transmit power to the remote device;

measure first parameters of an antenna circuit connected to an output of the control circuit; and

model the antenna circuit as a first virtual antenna portion and a second virtual antenna portion by assigning predetermined characteristics to the first virtual antenna portion and determining characteristics of the second virtual antennal portion based upon the first parameters; and

detect the presence of a foreign object by;

receiving reference characteristics of the antenna circuit from a receiver device;

measuring second parameters of the antenna circuit;

determine characteristics for the first virtual antenna from the second parameters and by fixing the determined characteristics of the second virtual antenna portion; and

identifying a foreign object by comparing the determined characteristics for the first virtual antenna with the characteristics received from the receiver device.

11. The device of claim 10,

wherein the first and second parameters of the antenna circuit include a center frequency and a quality factor of the antenna circuit.

12. The device of claim 10,

wherein the predetermined characteristics assigned to the first virtual antenna portion include a quality factor.

13. The device of claim 12,

wherein reference characteristics include a reference quality factor.

14. The device of claim 10,

wherein the control circuit is further configured to measure first and second parameters of an antenna circuit by applying an excitation signal to cause the antenna circuit to oscillate.

15. The device of claim 14,

wherein the antenna circuit forms an LC oscillator circuit and

wherein the control circuit is further configured to measure the first and second parameters by measuring a voltage or current of the LC oscillator circuit and to determine a quality factor of the antenna circuit based upon the measured voltage.

16. The device of claim 10,

wherein the first virtual antenna portion includes a portion of a parasitic resistance of an antenna coil of the antenna circuit.

17. The device of claim 16,

wherein the second virtual antenna includes another portion of the parasitic resistance of the antenna coil.

18. The device of claim 16,

wherein the characteristics of the second virtual antenna portion include another portion of the parasitic resistance of the antenna coil and a parasitic resistance of a capacitor of the antenna circuit.

19. A method comprising:

initializing a wireless charging station by;

measuring a first center frequency of an LC oscillator circuit that includes an antenna coil and a capacitor;

determining a first quality (Q) factor of the LC oscillator circuit;

modeling the LC oscillator circuit as multiple virtual antenna portions by

setting a predetermined quality factor for a first virtual antenna portion of the multiple virtual antenna portions; and

determining a set of initialization values for a second virtual antenna portion of the multiple virtual antenna portions using the first center frequency, the first quality factor and the predetermined quality factor; and

detecting the presence of a foreign object by;

receiving a reference quality factor from a receiver device;

measuring a second center frequency of the LC oscillator;

determining a second quality factor of the LC oscillator;

determining, based upon the measured second center frequency, second quality factor, and set of initialization values, a quality factor of the first virtual antenna portion;

comparing the reference quality factor to the determined quality factor of the first virtual antenna portion; and

identifying a foreign object based upon the results of the comparing.