Wireless power transfer system coil arrangements and method of operation

1. An apparatus for wirelessly transmitting power, the apparatus comprising:

a first conductive structure configured to generate a first magnetic field based on a first current received from a power source;

a second conductive structure configured to generate a second magnetic field based on a second current from the power source; and

a controller configured to:

supply power to each of the first conductive structure and the second conductive structure, in a sequence, and receive measurements of power contributions made in a third conductive structure configured to receive power via the first or the second magnetic field, and determine a respective coupling coefficient between each of the first and second conductive structures and the third conductive structure using the measurements; and

either balance magnitudes of the first and second currents or balance losses from the first conductive structure and the second conductive structure by controlling at least one of the first or second currents based at least in part on the coupling coefficients.

2. The apparatus of claim 1 , wherein the second conductive structure is positioned with respect to the first conductive structure to maintain a substantial absence of mutual coupling between the first and second conductive structures.

3. The apparatus of claim 1 , wherein the controller is configured to simultaneously control a phase and magnitude of the first and second currents applied to the first and second conductive structures.

4. The apparatus of claim 1 , wherein the controller is configured to control a phase difference between the first and second current applied to the first and second conductive structures.

5. The apparatus of claim 4 , wherein the controller is configured to adjust the phase difference between the first and second current applied to the first and second conductive structure to one of zero degrees or one-hundred-and-eighty degrees.

6. The apparatus of claim 5 , wherein the controller is configured to adjust the phase difference to either zero degrees or one-hundred-and-eighty degrees based on a position of a receiver conductive structure relative to the first and second conductive structures, the receiver conductive structure configured to wirelessly receive power via the first or second magnetic field.

7. The apparatus of claim 1 , wherein the controller is configured to control a magnitude of the first and second current applied to the first and second conductive structures.

8. The apparatus of claim 1 , wherein the controller is configured to adjust at least one of the first or second currents to maintain electromagnetic emissions below a threshold.

9. The apparatus of claim 1 , wherein the first conductive structure comprises a first loop and a second loop enclosing a first area and a second area, respectively, the first and second loops having lower surfaces that are substantially coplanar.

10. The apparatus of claim 9 , wherein the controller is configured to adjust the current to flow in a common direction in adjacent portions of the first and second loops.

11. The apparatus of claim 9 , wherein the second conductive structure encloses a third area, the second conductive structure positioned such that substantially a center of the third area is positioned substantially over a point between the first and second loops of the first conductive structure.

12. The apparatus of claim 9 , wherein the first conductive structure comprises one of:

a first coil wound to enclose the first area and the second area; or

a first and second coil each enclosing the first area and the second area, respectively,

and wherein the second conductive structure comprises a third coil wound to enclose a third area.

13. The apparatus of claim 12 , wherein a net sum of a magnetic field of the first conductive structure that intersects the second conductive structure is substantially zero.

14. The apparatus of claim 1 , wherein the controller is further configured to:

receive a communication from a wireless power receiver device comprising the third conductive structure comprising desired operating conditions; and

adjust the first or second current applied to the first and second conductive structures based in part on the desired operating conditions.

15. The apparatus of claim 1 , wherein the coupling coefficients define values corresponding to a fraction defined by an amount magnetic flux of the first and second conductive structures intersecting the third conductive structure.

16. The apparatus of claim 1 , wherein the controller is configured to balance magnitudes of the first and second currents.

17. The apparatus of claim 1 , wherein the controller is configured to balance losses from the first conductive structure and the second conductive structure.

18. A method for wirelessly transmitting power, the method comprising:

generating a first magnetic field via a first conductive structure based on a first current received from a power source;

generating a second magnetic field via a second conductive structure based on a second current from the power source;

receiving measurements of power contributions made in a third conductive structure configured to receive power via the first or the second magnetic field, and determining a respective coupling coefficient between each of the first and second conductive structures and the third conductive structure using the measurements; and

either balancing magnitudes of the first and second currents or balancing losses from the first conductive structure and the second conductive structure by controlling at least one of the first or second currents based at least in part on the coupling coefficients.

19. The method of claim 18 , wherein the second conductive structure is positioned with respect to the first conductive structure to maintain a substantial absence of mutual coupling between the first and second conductive structures.

20. The method of claim 18 , wherein adjusting at least one of the first or second currents comprises simultaneously controlling a phase and magnitude of the first and second currents applied to the first and second conductive structures.

21. The method of claim 18 , further comprising controlling a phase difference between the first and second current applied to the first and second conductive structures.

22. The method of claim 21 , wherein controlling the phase difference comprises adjusting the phase difference between the first and second current applied to the first and second conductive structure to one of zero degrees or one-hundred-and-eighty degrees.

23. The method of claim 22 , wherein adjusting the phase difference to either zero degrees or one-hundred-and-eighty degrees comprises adjusting the phase difference based on a position of a receiver conductive structure relative to the first and second conductive structures, the receiver conductive structure configured to wirelessly receive power via the first or second magnetic field.

24. The method of claim 18 , wherein adjusting at least one of the first or second currents comprises controlling a magnitude of the first and second current applied to the first and second conductive structures.

25. The method of claim 18 , wherein adjusting at least one of the first or second currents comprises adjusting the first or second current to maintain electromagnetic emissions below a threshold.

26. The method of claim 18 , wherein the first conductive structure comprises a first loop and a second loop enclosing a first area and a second area, respectively, the first and second loops having lower surfaces that are substantially coplanar.

27. The method of claim 26 , wherein the second conductive structure encloses a third area, the second conductive structure positioned such that substantially a center of the third area is positioned substantially over a point between the first and second loops of the first conductive structure.

28. The method of claim 18 , further comprising receiving a communication from a wireless power receiver device comprising the third conductive structure comprising desired operating conditions, wherein adjusting at least one of the first or second currents further comprises adjusting the current applied to the first and second conductive structures based in part on the desired operating conditions.

29. The method of claim 18 , wherein the coupling coefficients define values corresponding to a fraction defined by an amount magnetic flux of the first and second conductive structures intersecting the third conductive structure.

30. The method of claim 18 , wherein the method comprises balancing magnitudes of the first and second currents.

31. The method of claim 18 , wherein the method comprises balancing losses from the first conductive structure and the second conductive structure.

32. An apparatus for wirelessly transmitting power, the apparatus comprising:

a first means for generating a first magnetic field via based on a first current received from a power source;

a second means for generating a second magnetic field based on a second current from the power source;

means for supplying power to each of the first generating means and the second generating means, in a sequence, and for receiving measurements of power contributions made in a means for receiving power via the first or the second magnetic field, and determining a respective coupling coefficient between each of the first and second generating means and the means for receiving power using the measurements; and

means for either balancing magnitudes of the first and second currents or balancing losses from the first generating means and the second generating means by controlling at least one of the first or second currents based at least in part on the coupling coefficients.

33. The apparatus of claim 32 , wherein the second generating means is positioned with respect to the first generating means to maintain a substantial absence of mutual coupling between the first and second generating means.

34. The apparatus of claim 32 , wherein the means for improving wireless power transfer efficiency comprises means for simultaneously controlling a phase and magnitude of the first and second currents applied to the first and second generating means.

35. The apparatus of claim 32 , further comprising means for controlling a phase difference between the first and second current applied to the first and second generating means.

36. The apparatus of claim 32 , wherein adjusting at least one of the first or second currents comprises adjusting the first or second current to maintain electromagnetic emissions below a threshold.

37. The apparatus of claim 32 , wherein the first generating means comprises a first loop and a second loop enclosing a first area and a second area, respectively, the first and second loops having lower surfaces that are substantially coplanar.

38. The apparatus of claim 37 , wherein the second generating means encloses a third area, the second generating means positioned such that substantially a center of the third area is positioned substantially over a point between the first and second loops of the first generating means.

39. The apparatus of claim 32 , wherein the means for either balancing magnitudes or balancing losses balances magnitudes of the first and second currents.

40. The apparatus of claim 32 , wherein the means for either balancing magnitudes or balancing losses balances losses from the first generating means and the second generating means.