Magnetic shielding in inductive power transfer

• US 9,852,844 B2
• Filed: 03/24/2015
• Issued: 12/26/2017
• Est. Priority Date: 03/24/2014
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Golko, Albert J., Jol, Eric S., Graham, Christopher S., Yao, Stephen E., Brzezinski, Makiko K., Wagman, Daniel C., Thompson, Paul J., Kalyanasundaram, Nagarajan
• Primary Examiner(s): Poos, John
• Application Number:
  US14/666,793
• Publication Number:
  US 20150270058A1
• Time in Patent Office: 1,008 Days
• Field of Search: 307104
• CPC Class Codes: H01F 2027/348 Preventing eddy currents
• 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

Abstract

A first electronic device connects with an second electronic device. The first electronic device may include a first connection surface and an inductive power transfer receiving coil and a first magnetic element positioned adjacent to the first connection surface. The second electronic device may similarly include a second connection surface and an inductive power transfer transmitting coil and second magnetic element positioned adjacent to the second connection surface. In the aligned position, alignment between the electronic devices may be maintained by magnetic elements and the inductive power coils may be configured to exchange power. The magnetic elements and/or the inductive power coils may include a shield that is configured to minimize or reduce eddy currents caused in the magnetic elements by the inductive power coils.

Claims

1. A first electronic device, comprising:

a first connection surface;

an inductive power transfer receiving coil positioned adjacent to the first connection surface;

a first magnetic element positioned adjacent to the first connection surface; and

a shield at least partially positioned between the inductive power transfer receiving coil and the first magnetic element;

wherein;

a portion of the shield positioned between the first magnetic element and the inductive power transfer receiving coil defines a gap between the shield and the first magnetic element;

the shield is configured to reduce an eddy current caused in the first magnetic element by the inductive power transfer receiving coil;

the first magnetic element couples to a second magnetic element of a second electronic device to maintain an aligned position between the first and second electronic devices; and

the inductive power transfer receiving coil is configured to inductively receive power from an inductive power transfer transmitting coil of the second electronic device when the first electronic device and the second electronic device are in the aligned position.

2. The first electronic device of claim 1, further comprising a nonconductive and magnetically permeable coating on the first magnetic element.

3. The first electronic device of claim 2, wherein the nonconductive and magnetically permeable coating is formed of at least one of polymer, a combination of the polymer and conductive fibers, or a combination of the polymer and conductive particles.

4. The first electronic device of claim 1, wherein the shield is coupled to the first magnetic element.

5. The first electronic device of claim 4, wherein the shield is formed of at least one of an electrically nonconductive material, a soft magnetic material, a ferromagnetic material, a ceramic material, a crystalline material, or iron cobalt.

6. The first electronic device of claim 4, wherein the shield directs a magnetic field of the first magnetic element toward the first connection surface.

7. The first electronic device of claim 4, wherein at least a portion of the shield is coated with a nonconductive coating.

8. The first electronic device of claim 1, wherein a spacing between the first magnetic element and the inductive power transfer receiving coil is configured to reduce the eddy current.

9. A system for magnetic shielding for an inductive power transfer, the system comprising:

a first electronic device, comprising;

a first connection surface;

an inductive power transfer receiving coil positioned adjacent to the first connection surface; and

a first magnetic element positioned adjacent to the first connection surface; and

a second electronic device, comprising;

a second connection surface;

an inductive power transfer transmitting coil positioned adjacent to the second connection surface; and

a second magnetic element positioned adjacent to the second connection surface;

wherein;

the inductive power transmitting coil inductively transmits power to the inductive power transfer receiving coil; and

at least one of first magnetic element or the inductive power transfer receiving coil includes a shield that is configured to reduce an eddy current caused in the first magnetic element as a result of inductively transmitting power to the inductive power receiving coil, wherein the shield is at least partially positioned between the inductive power transfer receiving coil and the first magnetic element, and wherein a portion of the shield defines a gap between the shield and the first magnetic element.

10. The system of claim 9, wherein the shield is coupled to the inductive power transfer receiving coil and is configured to reduce the eddy current.

11. The system of claim 10, wherein the shield is a Faraday cage.

12. The system of claim 10, wherein the shield is formed of at least one of a crystalline material, a ceramic material, a soft magnetic material, a ferromagnetic material, or an iron silicon.

13. The system of claim 9, wherein the first connection surface is formed of a nonconductive material.

14. The system of claim 9, wherein at least one of:

at least one of the second magnetic element or the inductive power transfer receiving coil is configured to reduce eddy currents caused in the second magnetic element by the inductive power transfer receiving coil;

or

at least one of the first magnetic element or the inductive power transfer transmitting coil is configured to reduce eddy currents caused in the first magnetic element by the inductive power transfer transmitting coil.

15. An electronic device, comprising:

a housing;

an inductive coil located within the housing and operable to transmit or receive power in an inductive power transmission system;

a magnetic field directing material positioned either within or on the housing, wherein the magnetic field directing material blocks magnetic flux of the inductive power transmission system from the housing; and

a magnetic element disposed in the housing, wherein the magnetic field directing material is at least partially positioned between the inductive coil and the magnetic element, and wherein a portion of the magnetic field directing material defines a gap between the magnetic field directing material and the magnetic element.

16. The electronic device of claim 15, wherein the magnetic field directing material comprises at least one of a diamagnetic material or a superconductive material.

17. The electronic device of claim 16, wherein the diamagnetic material comprises at least one of graphite, bismuth, graphene, or pyrolytic carbon.

18. The electronic device of claim 15, wherein the magnetic field directing material is positioned between the inductive coil and the housing.

19. The electronic device of claim 15, wherein the magnetic field directing material is positioned on an interior surface of the housing.

20. The electronic device of claim 15, the housing including the magnetic field directing material.

21. The electronic device of claim 15, further comprising an additional magnetic field directing material positioned outside the housing.

22. The electronic device of claim 21, wherein the magnetic field directing material comprises a thermally conductive material.

23. The electronic device of claim 22, wherein the thermally conductive material is configured to operate as a heat spreader.

24. The electronic device of claim 15, wherein the housing comprises at least one of a paramagnetic material or a diamagnetic material.

25. The electronic device of claim 15, wherein the magnetic field directing material is positioned between multiple surfaces of the inductive coil and the housing.

26. The electronic device of claim 15, wherein the magnetic field directing material surrounds all surfaces of the inductive coil other than a surface of the inductive coil facing a magnetic path of the inductive power transmission system.

27. The electronic device of claim 15, wherein the magnetic field directing material is configured to shape a flow of the magnetic flux.

28. The electronic device of claim 15, wherein the magnetic field directing material is configured to prevent formation of eddy currents in the housing.

29. The electronic device of claim 15, wherein the magnetic field directing material is configured to reduce efficiency losses of the inductive power transmission system.