Wireless power transfer pad with multiple windings and magnetic pathway between windings

1. A wireless power transfer (“WPT”) pad comprising:

a ferrite structure;

a first winding adjacent to the ferrite structure, the first winding arranged in a spiral-type pattern; and

a second winding adjacent to the ferrite structure, the second winding arranged in a spiral-type pattern, the second winding wound interleaved to the first winding,

wherein the first and second windings are arranged to compensate for a difference in length between the first winding and the second winding for portions of the first and second windings wound adjacent to each other.

2. The WPT pad of claim 1 , wherein starting points of the first and second windings are at an exterior of the first and second windings, the starting point of the second winding is before the starting point of the first winding, and an ending point of the second winding is after an ending point of the first winding.

3. The WPT pad of claim 2 , wherein a length of the second winding is equal to a length of the first winding.

4. The WPT pad of claim 2 , wherein the starting point of the first winding is positioned so a conductor connected to the ending point of the second winding and traversing the first and second windings to the starting point of the first winding traverses perpendicular to the first and second windings to reach the starting point of the first winding, and wherein the starting point of the second winding is positioned so a conductor connected to the ending point of the second winding and traversing the first and second windings to the starting point of the second winding traverses perpendicular to the first and second windings to reach the starting point of the second winding.

5. The WPT pad of claim 1 , wherein the first winding comprises a first conductor and a fourth conductor and the second winding comprises a second conductor and a third conductor, wherein:

the first conductor is an outermost conductor and is adjacent to the second conductor;

the second conductor is adjacent to the third conductor;

the third conductor is adjacent to the fourth conductor; and

the fourth conductor is an innermost conductor.

6. The WPT pad of claim 5 , wherein ending points of the first, second, third and fourth conductors are at a center section of the first and second windings and a starting point of the first, second, third and fourth conductors are at an exterior of the first and second windings, and wherein the ending point of the first conductor is connected to the starting point of the fourth conductor and the ending point of the second conductor is connected to the starting point of the third conductor.

7. The WPT pad of claim 5 , wherein ending points of the first, second, third and fourth conductors are at a center section of the first and second windings and a starting point of the first, second, third and fourth conductors are at an exterior of the first and second windings; the ending point of the first conductor is connected to a first terminal of a first capacitor; a second terminal of the first capacitor is connected to the starting point of the fourth conductor; the ending point of the second conductor is connected to a first terminal of a second capacitor; and a second terminal of the second capacitor is connected to the starting point of the third conductor.

8. A wireless power transfer (“WPT”) pad comprising:

a ferrite structure comprising a planar surface;

a first winding comprising a first conductor wound in a planar arrangement in a spiral-type pattern about a center point, and

a second winding comprising a second conductor, wherein:

the first conductor is arranged to be adjacent to the planar surface of the ferrite structure,

each turn of the first winding is adjacent to the planar surface of the ferrite structure,

the first winding comprises a starting point, an ending point, and a fractional number of turns, wherein the starting point is at an angle from a radial line extending radially from the center point different than an angle of the ending point measured from the radial line; and

the first and second windings are arranged to compensate for a difference in length between the first winding and the second winding for portions of the first and second windings wound adjacent to each other.

9. The WPT pad of claim 8 , wherein a length of the first conductor relates to an amount of inductance of the first winding, and wherein the fractional number of turns is based on a target amount of inductance for the first winding.

10. The WPT pad of claim 9 , wherein the inductance of the first winding is further related to a diameter of the spiral-type pattern of the first winding, and wherein the fractional number of turns is based on the target amount of inductance of the first winding.

11. The WPT pad of claim 8 , wherein the second conductor is adjacent to the ferrite structure, the second winding is arranged in a spiral-type pattern, and the second winding is wound interleaved to the first winding.

12. A wireless power transfer (“WPT”) pad comprising:

a horizontal shield;

a ferrite structure mounted to the horizontal shield, the ferrite structure comprising a planar surface distal to a surface of the ferrite structure mounted to the horizontal shield;

a first winding comprising a first conductor in a planar arrangement in a spiral-type pattern about a center point, the first winding comprising a center section with the center point within the center section;

a capacitor located within the center section of the first winding;

a winding insulator located between conductors of the first winding and the ferrite structure, the winding insulator electrically insulating the conductors from the ferrites structure; and

a capacitor insulator located adjacent to the capacitor on a side of the capacitor facing the horizontal shield, wherein the capacitor insulator comprises a material that electrically insulates the capacitor from one or more of the ferrite structure and the horizontal shield, wherein the capacitor insulator transmits heat from the capacitor to one or more of the horizontal shield and the ferrite structure.

13. The WPT pad of claim 12 , further comprising a second winding comprising a second conductor adjacent to the ferrite structure,

wherein the second winding is arranged in a spiral-type pattern, the second winding wound interleaved to the first winding, and wherein the first and second windings are arranged to compensate for a difference in length between the first winding and the second winding for portions of the first and second windings wound adjacent to each other.

14. The WPT pad of claim 12 , wherein the capacitor insulator comprises a ceramic printed circuit board (“PCB”) material.

15. The WPT pad of claim 14 , wherein the capacitor insulator comprises a material that is an electrical insulator and a thermal conductor.

16. The WPT pad of claim 12 , wherein the winding insulator comprises a glass-reinforced epoxy laminate.

17. The WPT pad of claim 16 , wherein the winding insulator has a National Electrical Manufacturers Association (“NEMA”) flame retardant (“FR”) rating of 4 (“FR 4”).

18. The WPT pad of claim 12 , wherein the capacitor is secured to the horizontal shield with a fastener and the fastener is electrically insulated from the capacitor with a connector insulator.

19. The WPT pad of claim 12 , wherein the ferrite structure comprises a horizontal shield comprising the planar surface and a ferrite chimney, the ferrite chimney located in the center section and adjacent to the winding, the ferrite chimney extending in a direction away from the planar surface of the ferrite structure to at least a distance of one of a thickness of the conductors and twice a thickness of the horizontal shield, the thickness measured in a direction transverse to the planar surface, wherein the ferrite chimney is thermally and electrically coupled to the horizontal shield of the ferrite structure.