Wireless power transmission structures

1. A wireless power transfer apparatus, comprising:

a support structure having a top surface and a side surface, the support structure being configured to support a mobile device on the top surface and a wearable device at the side surface; and

a plurality of transmit coils within the support structure, the plurality of transmit coils being configured to wirelessly transmit power to the mobile device on the top surface and the wearable device at the side surface,

wherein the plurality of transmit coils comprises a first transmit coil that conducts current in a first direction and a second transmit coil that conducts current in a second direction opposite to the first direction to produce constructive interference at the side surface; and

wherein the first transmit coil comprises a spiral-shaped winding proximate the top surface of the support structure.

2. The wireless power transfer apparatus of claim 1 , wherein the plurality of transmit coils are connected in series.

3. The wireless power transfer apparatus of claim 1 , wherein the support structure has a central axis, and wherein the plurality of transmit coils are configured to wirelessly transmit power to the wearable device when the wearable device is placed on the side surface at any angular position about the central axis.

4. The wireless power transfer apparatus of claim 1 , wherein the support structure has a height of between 2 cm and 15 cm.

5. The wireless power transfer apparatus of claim 1 , wherein the support structure has a perimeter of between 8 cm and 20 cm.

6. The wireless power transfer apparatus of claim 1 , further comprising a base housing circuitry that drives the plurality of transmit coils, wherein the support structure extends above the base.

7. The wireless power transfer apparatus of claim 1 , further comprising a base having a ridge to position the wearable device at the side surface.

8. The wireless power transfer apparatus of claim 7 , wherein the base houses circuitry to drive the plurality of transmit coils and the wireless power transfer apparatus further comprises a magnetic shield between the plurality of transmit coils and the circuitry.

9. A wireless power transfer apparatus, comprising:

a support structure having a cavity configured to accommodate an electronic device; and

an upper transmit coil and a lower transmit coil within the support structure, the upper and lower transmit coils having current that flows in opposite directions to produce magnetic fields that constructively interfere in the cavity to wirelessly transmit power to the electronic device,

wherein the upper transmit coil and/or the lower transmit coil surrounds the cavity.

10. The wireless power transfer apparatus of claim 9 , wherein the upper and lower transmit coils are connected in series.

11. The wireless power transfer apparatus of claim 9 , wherein a compartment of a vehicle comprises the support structure.

12. The wireless power transfer apparatus of claim 11 , wherein the compartment comprises a cup holder.

13. The wireless power transfer apparatus of claim 9 , further comprising a magnetic shield around a side of the upper and lower transmit coils.

14. The wireless power transfer apparatus of claim 13 , wherein the magnetic shield surrounds the side of the upper and lower transmit coils and is also formed below the lower transmit coil.

15. The wireless power transfer apparatus of claim 9 , wherein the cavity has a shape defined by an interior surface the support structure and the support structure is configured to accommodate the electronic device within the cavity.

16. The wireless power transfer apparatus of claim 15 , wherein the shape is a cylindrical shape.