Method for detecting foreign object using sensor coil and electronic device

1. An electronic device capable of transmitting and receiving wireless power, the electronic device comprising:

a wireless power transfer (WPT) coil;

a sensor coil surrounding the WPT coil; and

a processor operatively coupled to the WPT coil and the sensor coil,

wherein the processor is configured to:

control to transmit and receive power by using the WPT coil,

perform a ping operation by using the sensor coil,

control to measure a waveform of a current or voltage of the sensor coil while or after performing the ping operation using the sensor coil,

control to check a Q factor of the sensor coil based on the measured waveform,

identify presence of a foreign object based on the checked Q factor, and

control the power transmission using the WPT coil based on a result of the identification of the presence of the foreign object.

2. The electronic device of claim 1 , wherein the processor is further configured to control to continue the power transmission using the WPT coil when the foreign object is not present.

3. The electronic device of claim 1 , wherein the processor is further configured to:

stop a current being input to the sensor coil; and

control to perform the ping operation by applying a resonant frequency current to the sensor coil.

4. The electronic device of claim 1 , wherein the processor is further configured to control to measure an attenuation curve of a resonant frequency current applied to the sensor coil or a voltage envelope of the sensor coil.

5. The electronic device of claim 1 , wherein the processor is further configured to identify the presence of the foreign object based on a threshold value of a Q factor of the sensor coil and the checked Q factor of the sensor coil.

6. The electronic device of claim 5 , wherein the processor is further configured to:

identify that the foreign object is present when a value of the checked Q factor of the sensor coil is smaller than the threshold value of the Q factor of the sensor coil; and

identify that the foreign object is not present when the value of the checked Q factor of the sensor coil is greater than the threshold value of the Q factor of the sensor coil.

7. The electronic device of claim 1 , wherein the processor is further configured to perform the ping operation using the sensor coil periodically or once.

8. The electronic device of claim 1 , wherein the processor is further configured to transmit a power transmission stop message by using the WPT coil or the sensor coil when the foreign object is present.

9. The electronic device of claim 1 , wherein the processor is further configured to control to measure the waveform of the current or voltage of the sensor coil in response to a power transmission operation of an external electronic device.

10. The electronic device of claim 1 , wherein the processor is further configured to transmit a power reception message or a power transmission message by using the WPT coil or the sensor coil.

11. A method of detecting, by an electronic device comprising a wireless power transfer (WPT) coil and a sensor coil surrounding the WPT coil and capable of transmitting and receiving wireless power, a foreign object by using a sensor coil, the method comprising:

controlling to transmit and receive power by using the WPT coil;

performing a ping operation by using the sensor coil;

controlling to measure a waveform of a current or voltage of the sensor coil while or after performing the ping operation using the sensor coil;

controlling to check a Q factor of the sensor coil based on the measured waveform;

identify presence of a foreign object based on the checked Q factor; and

controlling the power transmission using the WPT coil based on a result of the identification of the presence of the foreign object.

12. The method of claim 11 , further comprising controlling to continue the power transmission using the WPT coil when the foreign object is not present.

13. The method of claim 11 , wherein performing the ping operation comprises:

stopping a current being input to the sensor coil; and

controlling to perform the ping operation by applying a resonant frequency current to the sensor coil.

14. The method of claim 11 , wherein controlling to measure the waveform of the current or voltage of the sensor coil comprises controlling to measure an attenuation curve of a resonant frequency current applied to the sensor coil or a voltage envelope of the sensor coil.

15. The method of claim 11 , wherein identifying the presence of the foreign object comprises identifying the presence of the foreign object based on a threshold value of a Q factor of the sensor coil and the checked Q factor of the sensor coil.

16. The method of claim 15 , wherein identifying the presence of the foreign object further comprises:

identifying that the foreign object is present when a value of the checked Q factor of the sensor coil is smaller than the threshold value of the Q factor of the sensor coil; and

identifying that the foreign object is not present when the value of the checked Q factor of the sensor coil is greater than the threshold value of the Q factor of the sensor coil.

17. The method of claim 11 , wherein performing the ping operation comprises performing the ping operation using the sensor coil periodically or once.

18. The method of claim 11 , further comprising transmitting a power transmission stop message by using the WPT coil or the sensor coil when the foreign object is present.

19. The method of claim 11 , further comprising controlling to measure the waveform of the current or voltage of the sensor coil in response to a power transmission operation of an external electronic device.

20. The method of claim 11 , further comprising transmitting a power reception message or a power transmission message by using the WPT coil or the sensor coil.