Device and system for power transmission

1. A first device for power transmission comprising:

a power transmission section configured to transmit an electric power wirelessly; and

a detection section operatively connected to the power transmission section and configured to detect an object within a range from the power transmission section based on a change in load impedance of a power generation circuit,

wherein the detected object is determined as a second device to be power-supplied based on an increase in the load impedance of the power generation circuit at a determined frequency.

2. The first device of claim 1 , further comprising the power generation circuit operatively connected to the power transmission section and configured to generate the electric power.

3. The first device of claim 2 , wherein the detection section comprises:

a current-voltage detection unit configured to detect a current and a voltage in a vicinity of the power transmission section; and

a control section operatively connected to the current-voltage detection unit, and configured to detect the object based on the change in the load impedance calculated by the detected current and the detected voltage.

4. The first device of claim 3 , wherein the detected current is an alternating current and the detected voltage is an AC voltage.

5. The first device of claim 3 , wherein:

the detected current is a direct current and the detected voltage is a DC voltage; and

the change in the load impedance is a change in resistance calculated by the direct current and the DC voltage.

6. The first device of claim 1 , wherein the detection section is further configured to determine that the detected object is one of the second device to be power-supplied by the power transmission section or a foreign object based on an increase or decrease in the load impedance, respectively.

7. The first device of claim 6 , wherein the determination is made based on the increases in an absolute value of the load impedance.

8. The first device of claim 6 , wherein the determination is made based on the increase or decrease in a resistance value of the power generation circuit.

9. The first device of claim 6 , wherein the detected section is further configured to determine that the detected object is the foreign object based on the decrease in the load impedance.

10. The first device of claim 1 , wherein the detected section is further configured to detect the object intermittently at an interval.

11. The first device of claim 1 , wherein the detection section is further configured to detect the object by comparison of the change in the load impedance with a threshold value.

12. A system for power transmission comprising:

a transmitting device, comprising:

a power transmission section configured to transmit an electric power wirelessly; and

a detection section operatively connected to the power transmission section and configured to detect a receiving device within a range from the power transmission section based on an increase in load impedance of a power generation circuit at a determined frequency; and

the receiving device, comprising:

a power reception unit configured to receive the electric power wirelessly, and

a load operatively connected to the power reception unit and configured to operate based on the received electric power.

13. The system of claim 12 , wherein the transmitting device further comprises the power generation circuit operatively connected to the power transmission section, where the power generation circuit is configured to generate the electric power.

14. A method, comprising:

detecting a current and a voltage on a load side of a power generation circuit;

calculating a load impedance of a power generation circuit based on the detected current and the detected voltage; and

detecting an object within a range from a power transmitting device based on a change in the load impedance,

wherein the detected object is determined as a power receiving device to be power-supplied based on an increase in the load impedance of the power generation circuit at a determined frequency.

15. A method of claim 14 , further comprising determining that the detected object is one of the power receiving device to be power-supplied by the power transmitting device or a foreign object based on increase or decrease in the load impedance, respectively.

16. The method of claim 15 , wherein the detected object is the foreign object based on the decrease in the load impedance.

17. The method of claim 15 , further comprising, based on determining that the detected object is the power receiving device, transmitting an electric power wirelessly from the power transmitting device to the power receiving device.

18. The method of claim 14 , further comprising comparing the change in the load impedance with a threshold value.

19. The method of claim 14 , wherein the object is detected intermittently at an interval.