Systems and methods for adjusting magnetic field distribution using ferromagnetic material

• US 9,812,875 B2
• Filed: 09/05/2014
• Issued: 11/07/2017
• Est. Priority Date: 09/05/2014
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Nejatali, Saeed, Carobolante, Francesco, Tseng, Ryan, Chi, Mei-Li, Jeong, Seong Heon
• Primary Examiner(s): Deberadinis, Robert
• Application Number:
  US14/478,461
• Publication Number:
  US 20160072296A1
• Time in Patent Office: 1,159 Days
• CPC Class Codes: H01F 27/36 Electric or magnetic shields or screens movable for varying inductance H01F21/10
• CPC Class Codes: H01F 27/366 made of ferromagnetic material
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/70 involving the reduction of electric, magnetic or electromagnetic leakage fields
• CPC Class Codes: H02J 7/0044 specially adapted for holding portable devices containing batteries H02J7/0045 takes precedence

Abstract

A uniform magnetic field may provide better performance in wireless power transmitters due to smaller impedance variations in an output of a power amplifier of a wireless power transmitter and also allow for wireless power transmitter pads to be thinner. One aspect of the disclosure provides a device for wireless power transfer. The device comprises a substantially planar transmit antenna that is configured to generate a magnetic field. The device also comprises a pad having a charging surface. At least a portion of the transmit antenna is disposed in the pad. The device also comprises a ferromagnetic material having a shape and a position relative to the transmit antenna. At least one of the shape or position of the ferromagnetic material, or a combination thereof, is selected to modify a distribution of the magnetic field at the charging surface.

Claims

1. A device for wireless power transfer, comprising:

a substantially planar transmit antenna configured to generate a magnetic field;

a pad having a charging surface, at least a portion of the transmit antenna being disposed in the pad; and

a ferromagnetic material having a shape and a position relative to the transmit antenna, at least one of the shape or position of the ferromagnetic material, or combination thereof, selected to modify a distribution of the magnetic field at the charging surface.

2. The device of claim 1, wherein a magnetic permeability of the ferromagnetic material is selected to modify the distribution of the magnetic field at the charging surface.

3. The device of claim 1, wherein the at least one of the shape or position of the ferromagnetic material, or combination thereof, is selected to increase a uniformity of the distribution of the magnetic field at the charging surface.

4. The device of claim 1, wherein at least one of the shape or position of the ferromagnetic material, or combination thereof, is selected to decrease a difference between maximum and minimum magnetic field strength values at the charging surface to modify the distribution of the magnetic field at the charging surface.

5. The device of claim 1, wherein at least a portion of the transmit antenna is positioned on a plane between the ferromagnetic material and the charging surface and wherein the ferromagnetic material is configured to reduce a strength of the magnetic field in a direction opposite the charging surface.

6. The device of claim 1, wherein at least a portion of the ferromagnetic material is positioned on a plane between the transmit antenna and the charging surface.

7. The device of claim 1, wherein the ferromagnetic material comprises a first ferromagnetic portion positioned on a first plane between the transmit antenna and the charging surface and a second ferromagnetic portion is positioned on a second plane below the transmit antenna and the charging surface, the transmit antenna being positioned on a third plane between the first ferromagnetic portion and the second ferromagnetic portion.

8. The device of claim 1, wherein the ferromagnetic material comprises a first ferromagnetic portion having a first magnetic permeability and a second ferromagnetic portion having a second magnetic permeability, the first magnetic permeability being different from the second magnetic permeability.

9. The device of claim 1, wherein the transmit antenna comprises a plurality of turns and wherein the ferromagnetic material is positioned between the plurality of turns.

10. The device of claim 1, wherein the ferromagnetic material comprises one or more apertures.

11. The device of claim 1, wherein a thickness of the ferromagnetic material is non-uniform.

12. The device of claim 1, wherein the shape of the ferromagnetic material has at least one curvature.

13. The device of claim 1, wherein the ferromagnetic material is spaced from the charging surface so as to provide a gap there between.

14. A method for wireless power transfer, comprising:

generating a magnetic field at a substantially planar transmit antenna, at least a portion of the transmit antenna disposed in a pad; and

modifying a distribution of the magnetic field at a charging surface of the pad using ferromagnetic material having a shape and positioned relative to the transmit antenna.

15. The method of claim 14, wherein modifying a distribution of the magnetic field at the charging surface comprises selecting a magnetic permeability of the ferromagnetic material.

16. The method of claim 14, wherein modifying the distribution of the magnetic field comprises increasing a uniformity of the distribution of the magnetic field at the charging surface.

17. The method of claim 14, wherein at least one of the shape or position of the ferromagnetic material, or combination thereof, is selected to decrease a difference between maximum and minimum magnetic field strength values at the charging surface to modify the distribution of the magnetic field at the charging surface.

18. The method of claim 14, wherein at least a portion of the transmit antenna is positioned between the ferromagnetic material and the charging surface.

19. The method of claim 14, wherein at least a portion of the ferromagnetic material is positioned between the transmit antenna and the charging surface.

20. The method of claim 14, wherein the ferromagnetic material comprises a first ferromagnetic portion having a first magnetic permeability and a second ferromagnetic portion having a second magnetic permeability, the first magnetic permeability being different from the second magnetic permeability.

21. The method of claim 14, wherein the transmit antenna comprises a plurality of turns and wherein the ferromagnetic material is positioned between the plurality of turns.

22. A device for wireless power transfer, comprising:

means for generating a magnetic field, at least a portion of the magnetic field generating means disposed in a pad; and

means for modifying a distribution of the magnetic field at a charging surface of the pad, the magnetic field distribution modifying means having a shape and positioned relative to the magnetic field generating means.

23. The device of claim 22, wherein the modifying means is configured to increase a uniformity of the distribution of the magnetic field at the charging surface.

24. The device of claim 22, wherein the generating means comprises a planar transmit antenna and the modifying means comprises ferromagnetic material.

25. An apparatus for wirelessly transferring charging power to one or more receiver devices, the apparatus comprising:

a coil configured to generate a magnetic field for wirelessly transferring the charging power to the one or more receiver devices, the coil having a shape defining a first plane;

a housing configured to house the coil, the housing having a surface configured to allow positioning the one or more receiver devices thereon, the surface defining a second plane substantially parallel to the first plane of the coil; and

a ferromagnetic material positioned between the coil and the surface.

26. The apparatus of claim 25, wherein the ferromagnetic material is configured to increase a uniformity of the magnetic field across the surface where the one or more receiver devices receive power via the magnetic field.

27. The apparatus of claim 25, wherein at least one of a shape or position of the ferromagnetic material, or combination thereof, is selected to decrease a difference between maximum and minimum magnetic field strength values at the surface.

28. The apparatus of claim 25, wherein the ferromagnetic material comprises a first ferromagnetic portion positioned between the coil and the surface and a second ferromagnetic portion positioned below the coil.

29. The apparatus of claim 25, wherein the ferromagnetic material comprises a first ferromagnetic portion having a first magnetic permeability and a second ferromagnetic portion having a second magnetic permeability, the first magnetic permeability being different from the second magnetic permeability.

30. The apparatus of claim 25, wherein the ferromagnetic material comprises a first ferromagnetic portion and a second ferromagnetic portion, the first ferromagnetic portion and the second ferromagnetic portions positioned at different heights relative to the coil and each other.