System and method for reducing emissions for polarized coil systems for wireless inductive power transfer
View Patent ↗This disclosure includes systems, methods and apparatus for reducing emissions for polarized coil systems for wireless inductive power transfer. In one aspect, a magnetic flux device is provided which includes at least a first electrically conductive coil and a second electrically conductive coil that is substantially coplanar with the first coil. The device includes a magnetically permeable material having a substantially planar surface. The first coil and the second coil are substantially parallel to the substantially planar surface. The area of the material extends beyond the area of the first coil and beyond the area of the second coil. The area of the coil can substantially surround the area of the first coil and the area of the second coil.
1. A magnetic flux device configured to transmit magnetic flux to or to receive magnetic flux from a space beyond the device, the device comprising:
at least a first electrically conductive coil and a second electrically conductive coil, the first coil substantially planar, having a first inner periphery bounding a first region, and having a first outer periphery bounding a first area, the first outer periphery having at least one substantially straight first portion, the second coil substantially planar, having a second inner periphery bounding a second region, and having a second outer periphery bounding a second area, the second outer periphery having at least one substantially straight second portion, the second coil substantially coplanar with the first coil, the first coil having a first main coil radius equal to an average of a first inner coil radius of the first coil in a polarization direction of the device and a first outer coil radius of the first coil in the polarization direction of the device, the second coil having a second main coil radius equal to an average of a second inner coil radius of the second coil in the polarization direction of the device and a second outer coil radius of the second coil in the polarization direction of the device, the polarization direction of the device extending from a first center of the first coil to a second center of the second coil; and
a ferromagnetic material having a substantially planar surface, a third outer periphery bounding a third area, and a device size between extreme portions of the third outer periphery, the first coil and the second coil substantially parallel to the substantially planar surface, the third area extending beyond the first area along the at least one substantially straight first portion by a first distance in a range between 5% of either the first main coil radius or the second main coil radius and 20% of the device size and beyond the second area along the at least one substantially straight second portion by a second distance in a range between 5% of either the first main coil radius or the second main coil radius and 20% of the device size, the ferromagnetic material substantially overlaying the first region and substantially overlaying the second region.
2. The magnetic flux device of claim 1 , wherein the first coil is a spiral wound coil and the second coil is a spiral wound coil.
3. The magnetic flux device of claim 1 , wherein the first outer periphery is adjacent to the second outer periphery, the first coil is adjacent to the ferromagnetic material, and the second coil is adjacent to the ferromagnetic material.
4. The magnetic flux device of claim 1 , wherein the ferromagnetic material comprises a ferrite plate.
5. The magnetic flux device of claim 1 , wherein the at least one substantially straight first portion extends along a first direction and the at least one substantially straight second portion extends along a second direction substantially parallel to the first direction.
6. The magnetic flux device of claim 1 , wherein the third area extends beyond the first area in at least two directions perpendicular to one another and the third area extends beyond the second area in the at least two directions.
7. The magnetic flux device of claim 1 , wherein the third area extends beyond the first area by a distance in a range between 4 millimeters and 50 millimeters or by a distance that is between 5% of the main coil radius of either the first coil or the second coil in the polarization direction of the device and 20% of the overall device size and the third area extends beyond the second area by a distance in a range between 4 millimeters and 50 millimeters or by a distance that is between 5% of the main coil radius of the first coil or the second coil in the polarization direction of the device and 20% of the overall device size.
8. The magnetic flux device of claim 1 , wherein the ferromagnetic material extends across the entire first region in two orthogonal directions and extends across the entire second region in the two orthogonal directions.
9. The magnetic flux device of claim 1 , wherein the third outer periphery is spaced from the first outer periphery and from the second outer periphery in at least two orthogonal directions substantially parallel to the first coil and the second coil by a distance in a range between 4 millimeters and 50 millimeters.
10. The magnetic flux device of claim 1 , wherein the sum of the first area and the second area is less than the third area.
11. The magnetic flux device of claim 1 , wherein the first coil is on a first half of the surface and the second coil is on a second half of the surface.
12. The magnetic flux device of claim 1 , wherein an outer horizontal dimension of the sum of the first coil and the second coil is less than an outer horizontal dimension of the ferromagnetic material.
13. The magnetic flux device of claim 1 , wherein the first coil and the second coil are in a polarized coil configuration.
14. The magnetic flux device of claim 1 , wherein the ferromagnetic material is configured to reduce a portion of magnetic flux emission from the magnetic flux device that does not contribute to energy transfer by the magnetic flux device.
15. A magnetic flux device configured to transmit magnetic flux to or to receive magnetic flux from a space beyond the device, the device comprising:
at least a first electrically conductive coil and a second electrically conductive coil, the first coil substantially planar and having a first outer periphery bounding a first area, the second coil substantially planar and having a second outer periphery bounding a second area, the second coil substantially coplanar with the first coil, the first coil having a first main coil radius equal to an average of a first inner coil radius of the first coil in a polarization direction of the device and a first outer coil radius of the first coil in the polarization direction of the device, the second coil having a second main coil radius equal to an average of a second inner coil radius of the second coil in the polarization direction of the device and a second outer coil radius of the second coil in the polarization direction of the device, the polarization direction of the device extending from a first center of the first coil to a second center of the second coil; and
a ferromagnetic material having a substantially planar surface, a third outer periphery bounding a third area, and a device size between extreme portions of the third outer periphery, the first coil and the second coil substantially parallel to the substantially planar surface, the third area extending beyond the first area by a first distance in a range between 5% of either the first main coil radius or the second main coil radius and 20% of the device size and extending beyond the second area by a second distance in a range between 5% of either the first main coil radius or the second main coil radius and 20% of the device is, the third area substantially surrounding the first area and the second area.
16. The magnetic flux device of claim 15 , wherein the third area extends beyond the first area and the second area by a distance in a range between 4 millimeters and 50 millimeters.
17. The magnetic flux device of claim 15 , wherein the third outer periphery is spaced from the first outer periphery and from the second outer periphery by a distance in a range between 4 millimeters and 50 millimeters.
18. The magnetic flux device of claim 15 , wherein the first coil and the second coil are in a polarized coil configuration.
19. The magnetic flux device of claim 15 , wherein the ferromagnetic material is configured to reduce a portion of magnetic flux emission from the magnetic flux device that does not contribute to energy transfer by the magnetic flux device.
20. A method for wirelessly transferring power, the method comprising:
using a magnetic flux device to transmit magnetic flux to or to receive magnetic flux from a space beyond the magnetic flux device, the magnetic flux device comprising at least a first electrically conductive coil, a second electrically conductive coil, and a ferromagnetic material, the first coil substantially planar, having a first inner periphery bounding a first region, and having a first outer periphery bounding a first area, the first outer periphery having at least one substantially straight first portion, the second coil substantially planar, having a second inner periphery bounding a second region, and having a second outer periphery bounding a second area, the second outer periphery having at least one substantially straight second portion, the second coil substantially coplanar with the first coil, the first coil having a first main coil radius equal to an average of a first inner coil radius of the first coil in a polarization direction of the device and a first outer coil radius of the first coil in the polarization direction of the device, the second coil having a second main coil radius equal to an average of a second inner coil radius of the second coil in the polarization direction of the device and a second outer coil radius of the second coil in the polarization direction of the device, the polarization direction of the device extending from a first center of the first coil to a second center of the second coil, the ferromagnetic material having a substantially planar surface, third outer periphery bounding a third area, and a device size between extreme portions of the third outer periphery, the first coil and the second coil substantially parallel to the substantially planar surface, the third area extending beyond the first area along the at least one substantially straight first portion by a first distance in a range between 5% of either the first main coil radius or the second main coil radius and 20% of the device size and beyond the second area along the at least one substantially straight second portion by a second distance in a range between 5% of either the first main coil radius or the second main coil radius and 20% of the device size, the ferromagnetic material substantially overlaying the first region and substantially overlaying the second region.
21. The method of claim 20 , wherein the third area substantially surrounds the first area and the second area.