ELECTRONIC DEVICE HAVING AN INDUCTIVE RECEIVER COIL WITH ULTRA-THIN SHIELDING LAYER AND METHOD

• US 20120057322A1
• Filed: 05/05/2010
• Published: 03/08/2012
• Est. Priority Date: 05/20/2009
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Waffenschmidt, Eberhard
• Granted Patent: US 9,084,343 B2
• Time in Patent Office: Days
• US Class Current: 361/816
• 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
• CPC Class Codes: H02J 50/005 Mechanical details of housing or structure aiming to accommodate the power transfer means, e.g. mechanical integration of coils, antennas or transducers into emitting or receiving devices
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/70 involving the reduction of electric, magnetic or electromagnetic leakage fields
• CPC Class Codes: H02J 7/0042 characterised by the mechanical construction
• CPC Class Codes: H05K 9/0075 Magnetic shielding materials

Abstract

An electronic device (10,40) which is inductively powered or charged has a receiver coil (12) on which a metal object (24,42) can be placed without causing deterioration of the coil'"'"'s magnetic field and without generating heat in the metal object. An ultra-thin, flexible, high magnetic permeability metal foil (14) having a thickness of 50 μm or less is provided as a shielding layer between the coil and the object. Radial slits (22) are provided in the shielding layer, which suppress unwanted eddy currents in the layer to reduce power transfer losses and heat generation.

Claims

1. An electronic device (10,40) configured for being inductively powered or charged comprising:

an inductive receiver coil (12) configured for generating current in response to being exposed to an alternating magnetic field generated substantially on a first side of the receiver coil, and

a softmagnetic shielding layer (14) disposed on a second side of the receiver coil, opposite to the first side where the magnetic field is generated, configured (i) to shield the magnetic field from an overlying object (24,42) wherein the overlying object is (i)(a) subject to being undesirably influenced by the magnetic field, or (i)(b) subject to causing an undesirable influence on the magnetic field and (ii) to mitigate formation of eddy currents within the softmagnetic shielding layer and the overlying object.

2. The device of claim 1, wherein said softmagnetic shielding layer (14) includes an ultra-thin layer having a thickness less than or equal to one hundred micrometers (100 μ

m).

3. The device of claim 1, wherein the softmagnetic shielding layer (14) includes at least one eddy current mitigation feature (22) that comprises a number of slits formed within the softmagnetic shielding layer, wherein the slits are substantially parallel to magnetic flux lines and orthogonal to eddy current flow for imposing a large impedance to eddy current formation.

4. The device of claim 1, wherein a total thickness (34) of the inductive receiver coil (12) and the softmagnetic shielding layer (14) is on the order of less than 300 μ

m.

5. The device of claim 1, wherein the softmagnetic shielding layer (14) comprises a material selected from the group consisting of Mumetal, nanocristaline metal and amorphous metals.

6. The device of claim 5, wherein the softmagnetic shielding layer (14) has a thickness on the order of fifty micrometers or less.

7. The device of claim 1, wherein the softmagnetic shielding layer (14) comprises a shape of sufficient size to cover the receiver coil on a single side of the receiver coil.

8. The device of claim 1, wherein the inductive receiver coil (12) comprises a circular shaped coil and further wherein the softmagnetic shielding layer (14) includes eddy current mitigation features (22) that comprise slits that emanate in a radial direction from a location centred on the circular shaped receiver coil.

9. The device of claim 1, wherein the inductive receiver coil (12) comprises a flexible substrate (30,32) having a coil of conductive material (20) integrated within the flexible substrate, and wherein the softmagnetic shielding layer (14) comprises a flexible layer.

10. The device of claim 1, wherein the overlying object (24) comprises one selected from the group consisting of a rechargeable battery with a conductive housing and an electronic circuit.

11. The device of claim 1, wherein the overlying object (42) comprises a lamp with a metallic base plate, further wherein the metallic base plate of the lamp is configured for being disposed overlying the shielding layer, the lamp for being powered in response to the generated current.

12. The device of claim 3, wherein the slits (22) formed within the softmagnetic shielding layer (14) are created via laser cutting, wherein a layer of softmagnetic shielding material is attached to a transparent adhesive foil, laser energy is directed towards the softmagnetic shielding material layer at desired sites to evaporate corresponding softmagnetic shielding material to form the slits, wherein the transparent adhesive foil remains intact.

13. The device of claim 3, wherein a layer of softmagnetic shielding material (14) is laminated to one selected from the group consisting of the inductive receiver coil (12) and a printed circuit board, further wherein the layer of material is etched to form the softmagnetic shielding layer with slits (22).

14. An electronic device (10,40) configured for being inductively powered or charged, comprising:

an inductive receiver coil (12) configured for generating current in response to being exposed to an alternating magnetic field generated substantially on a first side of the inductive receiver coil; and

an ultra-thin softmagnetic shielding layer (14) disposed on a second side of the inductive receiver coil, opposite to the first side where the magnetic field is generated, configured (i) to shield the magnetic field from an overlying object (24,42) wherein the overlying object is (i)(a) subject to being undesirably influenced by the magnetic field, or (i)(b) subject to causing an undesirable influence on the magnetic field and (ii) to mitigate formation of eddy currents within the shielding layer and the overlying object, wherein the shielding layer comprises a thickness less than or equal to one hundred micrometers (100 μ

m), wherein said shielding layer includes at least one eddy current mitigation feature (22) that comprises a number of slits formed within the shielding layer, wherein the slits are substantially parallel to magnetic flux lines and orthogonal to eddy current flow for imposing a large impedance to eddy current formation, and wherein the shielding layer comprises a material selected from the group consisting of Mumetal, nanocristaline metal and amorphous metals.

15. The device of claim 14, wherein the overlying object (24,42) comprises one selected from the group consisting of (i) a rechargeable battery with a conductive housing, (ii) an electronic circuit and (iii) a lamp module with a metallic base plate, further wherein the metallic base plate of the lamp module is configured for being disposed overlying the shielding layer, the lamp for being powered in response to the generated current.

16. A method for configuring an electronic device (10,40) for being inductively powered or charged, comprising:

configuring an inductive receiver coil (12) for generating current in response to being exposed to an alternating magnetic field generated substantially on a first side of the inductive receiver coil; and

disposing an ultra-thin softmagnetic shielding layer (14) on a second side of the inductive receiver coil, opposite to the first side where the magnetic field is generated, configured (i) to shield the magnetic field from an overlying object (24,42) wherein the overlying object is (i)(a) subject to being undesirably influenced by the magnetic field, or (i)(b) subject to causing an undesirable influence on the magnetic field and (ii) to mitigate formation of eddy currents within the shielding layer and the overlying object, wherein the shielding layer comprises a thickness less than or equal to one hundred micrometers (100 μ

m).

17. The method of claim 16, wherein disposing said shielding layer (14) includes providing at least one eddy current mitigation feature (22) that comprises a number of slits formed within the shielding layer, wherein the slits are substantially parallel to magnetic flux lines and orthogonal to eddy current flow for imposing a large impedance to eddy current formation.

18. The method of claim 17, wherein the slits (22) formed within the softmagnetic shielding layer (14) are created via laser cutting, wherein a layer of softmagnetic shielding material is attached to a transparent adhesive foil, laser energy is directed towards the softmagnetic shielding material layer at desired sites to evaporate corresponding softmagnetic shielding material to form the slits, wherein the transparent adhesive foil remains intact.

19. The method of claim 16, wherein a total thickness (34) of the inductive receiver coil (12) and the ultra-thin softmagnetic shielding layer (14) is on the order of less than 300 μ

m, and wherein the ultra-thin softmagnetic shielding layer comprises a material selected from the group consisting of Mumetal, nanocristaline metal and amorphous metals.

20. The method of claim 16, wherein the overlying object (24,42) comprises one selected from the group consisting of (i) a rechargeable battery with a conductive housing, (ii) an electronic circuit and (iii) a lamp module with a metallic base plate, further wherein the metallic base plate of the lamp module is configured for being disposed overlying the shielding layer, the lamp for being powered in response to the generated current.