Tunable wireless power device

1. A device for providing wireless power, comprising:

a transmit antenna configured to wirelessly transmit power via a magnetic field at a level sufficient to power or charge a chargeable device;

a metallic structure spaced at a non-zero distance and physically isolated from the transmit antenna, and configured to:

induce eddy currents to detune the transmit antenna, the eddy currents creating a magnetic field that opposes a change in the magnetic field generated by the transmit antenna, and

shield the transmit antenna from another metallic structure to reduce eddy currents generated in the other metallic structure;

a magnetic material positioned between the transmit antenna and the metallic structure; and

a circuit configured to tune the transmit antenna in the presence of the metallic structure, the transmit antenna, the metallic structure, the magnetic material and the circuit integrated together.

2. The device of claim 1 , the metallic structure comprising a metal sheet.

3. The device of claim 1 , the metallic structure and the transmit antenna being separated by a distance within a range of substantially 20 to 33 millimeters.

4. The device of claim 1 , the magnetic material comprising a ferromagnetic structure.

5. The device of claim 1 , further comprising a separator positioned between the metallic structure and an external surface of the device.

6. The device of claim 5 , the separator having a height of substantially 1 millimeter.

7. The device of claim 1 , the metallic structure having one of a rectangular shape, a square shape, or a circular shape.

8. A method for providing wireless power, comprising:

inducing eddy currents in a metallic structure within a wireless power device to detune a transmit antenna, the eddy currents creating a magnetic field that opposes a change in the magnetic field generated by the transmit antenna, an area of the metallic structure substantially equal to or greater than an area of the transmit antenna, the transmit antenna spaced at a non-zero distance and physically isolated from the metallic structure;

shielding the transmit antenna via the metallic structure from another metallic structure to reduce eddy currents generated in the other metallic structure; and

tuning the transmit antenna in the presence of the magnetic field and in the presence of a magnetic material proximate the metallic structure.

9. The method of claim 8 , the tuning comprising tuning the transmit antenna in the presence of the metallic structure separated from the transmit antenna a distance within a range of substantially 20 to 33 millimeters.

10. The method of claim 8 , the tuning comprising tuning the transmit antenna with a matching circuit.

11. The method of claim 8 , the inducing eddy currents in the metallic structure comprises inducing eddy currents in a metallic sheet.

12. The method of claim 8 , the tuning the transmit antenna in the presence of the magnetic material comprising tuning the transmit antenna in the presence of a ferromagnetic structure.

13. The method of claim 8 , further comprising wirelessly transmitting power at a transfer efficiency of substantially 68% while the wireless power device is positioned proximate the other metallic structure.

14. The method of claim 8 , the tuning comprising tuning the transmit antenna in the presence of the metallic structure spaced from a surface of the wireless power device.

15. The method of claim 8 , the tuning comprising tuning the transmit antenna in the presence of the metallic structure having one of a rectangular shape, a square shape, and a circular shape.

16. A device for providing wireless power, comprising:

means for generating a first magnetic field at a level sufficient to power or charge a chargeable device;

means for inducing eddy currents, the eddy currents creating a second magnetic field that opposes a change of the first magnetic field;

means for detuning the generating means, the detuning means shielding the generating means from another means for detuning the generating means to reduce eddy currents generated in the other detuning means, the detuning means being spaced a non-zero distance and physically isolated from the generating means; and

means for tuning the generating means in the presence of a magnetic material proximate the detuning means.

17. The device of claim 16 , the means for tuning comprising means for tuning the generating means in the presence of the detuning means separated from the generating means by a distance within a range of substantially 20 to 33 millimeters.

18. The device of claim 1 , the metallic structure configured to detune the transmit antenna based at least in part on a distance between the transmit antenna and the metallic structure, the circuit configured to tune the transmit antenna based at least in part on detuning caused by the metallic structure.