Wireless power transmitters and associated base stations for transmitting power at extended separation distances

1. A power transmitter for wireless power transfer comprising:

a coil configured to transmit a power signal to a power receiver, the coil comprising:

a first coil portion defining, at least, a top face, and

a second coil portion positioned radially outward from the first coil portion; and

a shielding comprising:

a ferrite core,

a first shield portion, the first shield portion defining a first cavity, the first cavity configured such that the ferrite core substantially surrounds all but the top face of the first coil portion, and

a second shield portion, the second shield portion including a magnetic backing and a magnetic ring, the magnetic backing and the magnetic ring, in combination, defining a second cavity, the magnetic ring defining a bottom portion, a top portion, and an inner sidewall between the bottom portion and the top portion, the inner sidewall defining an outward extending shape, the outward extending shape extending radially outward from the bottom portion to the top portion, the second coil portion positioned within the second cavity.

2. The power transmitter of claim 1 , wherein the coil further comprises a series connection between the first coil portion and the second coil portion.

3. The power transmitter of claim 1 , wherein the first coil portion and the second coil portion are in a parallel electrical connection with respect to electrical components of the power transmitter.

4. The power transmitter of claim 1 , wherein the coil is formed of wound Litz wire.

5. The power transmitter of claim 4 , wherein the Litz wire is a bifilar Litz wire.

6. The power transmitter of claim 1 , wherein the first coil portion comprises a first layer and a second layer, and wherein the first layer of the first coil portion includes a first number of turns in a range of about 4 turns to about 5 turns, and wherein the second layer of the first coil portion includes a second number of turns in a range of about 4 turns to about 5 turns.

7. The power transmitter of claim 6 , wherein the second coil portion comprises a first layer and a second layer, and wherein the first layer of the second coil portion includes a first number of turns in a range of about 2 to about 5 turns, and wherein the second layer of the second coil portion includes a second number of turns in a range of about 2 to about 5 turns.

8. The power transmitter of claim 1 , wherein the outward extending shape of the inner side wall defines one or more of a slope, a curve, or combinations thereof.

9. The power transmitter of claim 1 , further comprising an operating frequency selected from a range of about 87 kilohertz (kHz) to about 360 kHz.

10. A base station for a wireless power transfer system comprising:

an interface surface;

a coil configured to transmit a power signal to a power receiver, the coil comprising:

a first coil portion defining, at least, a first top face, and

a second coil portion positioned radially outward from the first coil portion; and

a shielding comprising a ferrite core and including:

a first shield portion, the first shield portion defining a first cavity, the first cavity configured such that the ferrite core substantially surrounds all but the first top face of the first coil portion, and

a second shield portion, the second shield portion including a magnetic backing and a magnetic ring, the magnetic backing and magnetic ring, in combination, defining a second cavity, the magnetic ring defining a bottom portion, a top portion, and an inner sidewall between the bottom portion and the top portion, the inner sidewall defining an outward extending shape, the outward extending shape extending radially outward from the bottom portion to the top portion, the second coil portion positioned within the second cavity.

11. The base station of claim 10 , wherein the interface surface extends across substantially all of the first top face of the first coil portion and a second top face of the second coil portion.

12. The base station of claim 10 , wherein the coil further comprises a series connection between the first coil portion and the second coil portion.

13. The base station of claim 10 , wherein the first coil portion and the second coil portion are in a parallel electrical connection with respect to electrical components of the base station.

14. The base station of claim 10 , further comprising at least one user feedback mechanism configured for aiding a user in aligning the power receiver with an active area for wireless power transmission via the coil, the power receiver configured to acquire near field inductive power from the coil.

15. The base station of claim 10 , further comprising an operating frequency selected from a range of about 87 kilohertz (kHz) to about 360 kHz.

16. The base station of claim 10 , wherein the outward extending shape of the inner side wall defines one or more of a slope, a curve, or combinations thereof.

17. A power transmitter for wireless power transfer comprising:

a coil configured to transmit a power signal to a power receiver, the coil comprising:

a first coil portion including a first layer and a second layer, each of the first layer of the first coil portion and the second layer of the first coil portion including a respective number of turns in a range of about 4 turns to about 5 turns, the first coil portion defining, at least a top face, and

a second coil portion positioned radially outward from the first coil portion, the second coil portion including a first layer and a second layer, each of the first layer of the second coil portion and the second layer of the second coil portion including a respective number of turns in a range of about 4 turns to about 5 turns, and

wherein a series connection is formed between the first coil portion and the second coil portion; and

a shielding comprising:

a ferrite core

a first shield portion, the first shield portion defining a first cavity, the first cavity configured such that the ferrite core substantially surrounds all but the top face of the first coil portion, and

a second shield portion, the second shield portion including a magnetic backing and a magnetic ring, the magnetic backing and the magnetic ring, in combination, defining a second cavity, the magnetic ring defining a bottom portion, a top portion, and an inner sidewall between the bottom portion and the top portion, the inner sidewall defining an outward extending shape, the outward extending shape extending radially outward from the bottom portion to the top portion, the second coil portion positioned within the second cavity.

18. The power transmitter of claim 17 , wherein the outward extending shape of the inner side wall defines one or more of a slope, a curve, or combinations thereof.

19. The power transmitter of claim 17 , further comprising an operating frequency selected from a range of about 87 kilohertz (kHz) to about 360 kHz.

20. The power transmitter of claim 17 , wherein the power transmitter is positioned within a base station comprising at least one user feedback mechanism configured for aiding a user in aligning the power receiver with an active area for wireless power transmission via the coil, the power receiver configured to acquire near field inductive power from the coil.