Power feeding device, power receiving device, and wireless power feed system

1. A wireless power feeding method comprising the steps of:

performing power feeding to a power receiving device by a power feeding device; and

obtaining a parameter corresponding to a distance between the power feeding device and the power receiving device by the power feeding device,

wherein the power feeding device comprises a first resonant coil and a first electromagnetic coupling coil,

wherein the power receiving device comprises a second resonant coil and a second electromagnetic coupling coil,

wherein during the power feeding, power feeding conducted by a resonant method or power feeding conducted by an electromagnetic coupling method are selected in accordance with the parameter,

wherein in the case where the power feeding conducted by the resonant method is selected, the first resonant coil electromagnetically resonates with the second resonant coil,

wherein in the case where the power feeding conducted by the electromagnetic coupling method is selected, the first resonant coil is short-circuited and the first electromagnetic coupling coil is electromagnetically coupled with the second resonant coil, and

wherein the first electromagnetic coupling coil is between the first resonant coil and the second resonant coil during the power feeding.

2. The wireless power feeding method according to claim 1 ,

wherein the power feeding device further comprises a switch which in turned on or off in accordance with the parameter, and

wherein the first resonant coil is short-circuited by turning the switch on.

3. The wireless power feeding method according to claim 1 ,

wherein the parameter represents an amplitude of a reflective wave detected by a directional coupler in the power feeding device, and

wherein the directional coupler is electrically connected between an AC power source and the first electromagnetic coupling coil.

4. The wireless power feeding method according to claim 3 ,

wherein the detection of the amplitude of the reflective wave is repeated every certain period during the power feeding.

5. The wireless power feeding method according to claim 3 ,

wherein the parameter is input to a control circuit from the directional coupler via an analog-digital converter,

wherein the control circuit memorizes the parameter and turns on or off a switch in accordance with the parameter, and

wherein in the case where the power feeding conducted by the electromagnetic coupling method is selected, the first resonant coil is short-circuited by turning the switch on.

6. The wireless power feeding method according to claim 5 ,

wherein the switch is turned on or off when the amplitude of the reflective wave becomes larger than the amplitude of the reflective wave before previous detection.

7. A wireless power feeding method comprising the steps of:

performing power feeding to a power receiving device by a power feeding device; and

obtaining a parameter corresponding to a distance between the power feeding device and the power receiving device by the power receiving device,

wherein the power feeding device comprises a first resonant coil and a first electromagnetic coupling coil,

wherein the power receiving device comprises a second resonant coil and a second electromagnetic coupling coil,

wherein during the power feeding, power feeding conducted by a resonant method or power feeding conducted by an electromagnetic coupling method are selected in accordance with the parameter,

wherein in the case where the power feeding conducted by the resonant method is selected, the first resonant coil electromagnetically resonates with the second resonant coil,

wherein in the case where the power feeding conducted by the electromagnetic coupling method is selected, the second resonant coil is short-circuited and the second electromagnetic coupling coil is electromagnetically coupled with the first resonant coil, and

wherein the second electromagnetic coupling coil is between the first resonant coil and the second resonant coil during the power feeding.

8. The wireless power feeding method according to claim 7 ,

wherein the power receiving device further comprises a switch turned on or off in accordance with the parameter, and

wherein the second resonant coil is short-circuited by turning the switch on.

9. The wireless power feeding method according to claim 7 ,

wherein the power receiving device further comprises a load, a rectifier which is electrically connected to the second electromagnetic coupling coil, and an analog-digital converter,

wherein a DC voltage is applied to opposite ends of the load by transfer of power rectified by the rectifier,

wherein the analog-digital converter detects the DC voltage and a direct current generated by the DC voltage applied to the load, and

wherein the parameter represents magnitudes of the DC voltage and the direct current detected by the analog-digital converter.

10. The wireless power feeding method according to claim 9 ,

wherein the detection of the magnitudes of the DC voltage and the direct current is repeated every certain period during the power feeding.

11. The wireless power feeding method according to claim 9 ,

wherein the parameter is input to a control circuit,

wherein the control circuit memorizes the parameter and turns on or off a switch in accordance with the parameter, and

wherein in the case where the power feeding conducted by the electromagnetic coupling method is selected, the second resonant coil is short-circuited by turning the switch on.