Combining power from multiple resonance magnetic receivers in resonance magnetic power system

• US 8,796,885 B2
• Filed: 04/20/2012
• Issued: 08/05/2014
• Est. Priority Date: 05/31/2011
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Tan, Li-Quan, Amm, David T.
• Primary Examiner(s): CAVALLARI, DANIEL J
• Application Number:
  US13/452,712
• Publication Number:
  US 20120306282A1
• Time in Patent Office: 837 Days
• Field of Search: 307/104
• US Class Current: 307/104
• 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 50/40 using two or more transmitting or receiving devices H02J50/50 takes precedence
• CPC Class Codes: H02J 7/0042 characterised by the mechanical construction
• CPC Class Codes: H04B 5/26 using coils
• CPC Class Codes: H04B 5/263 Multiple coils at either side
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

Various embodiments of a wirelessly powered local computing environment are described. A system and method for utilizing wireless near field magnetic resonance (NFMR) power transmission in a computing environment. A small form factor wireless power unit can be used to replace conventional batteries.

Claims

1. A wireless power unit arranged to provide at least a minimum amount of power to a device wirelessly received from a magnetic field provided by a near field magnetic resonance (NFMR) transmitter unit having a resonance frequency ω

_T, the minimum amount of power delivered to the device being independent of a spatial orientation of the portable power unit with respect to the magnetic field, comprising;

a first resonator structure, the first resonator structure having a resonant frequency ω

₁, and a characteristic size L₁;

a second resonator structure, the second resonator structure having a resonant frequency ω

₂, and a characteristic size L₂, wherein the first and second resonator structures are magnetically decoupled such that an effective magnetic coupling coefficient κ

eff between the first and second resonator structures is about zero; and

a power combining circuit coupled to the magnetically decoupled first and second resonator structures arranged to;

load match the first and second resonator structures and the device,

load balance power from the first and second resonator structures, and

maintain an effective magnetic coupling coefficient between the first and second resonator structures at about zero regardless of a spatial orientation of the wireless power unit with regards to the NFMR magnetic field such that the device wirelessly receives the at least the minimum amount of power from the wireless power unit regardless of an orientation of the at least two NFMR power receivers with respect to the NFMR magnetic field.

2. The wireless power unit as recited in claim 1, wherein the first resonator structure and the second resonator structure are fixed at positions relative to each other within the wireless power unit such that the effective magnetic coupling coefficient κ

eff between the first and second resonator structures is about zero regardless of the spatial orientation of the portable power unit with respect to the magnetic field provided by the wireless transmitter unit.

3. The wireless power unit as recited in claim 1, wherein a non-radiative power transfer between wireless transmitter unit and the first resonator structure and the second resonator structures is mediated through a magnetic resonant coupling between the first resonator structure and the second resonator structure when at least one of the first resonator structure and the second resonator structure is in a tuned state with respect to the NFMR transmitter unit.

4. The wireless power unit as recited in claim 3, wherein the first resonator structure is in the tuned state when the first resonant frequency ω

₁ and the wireless transmitter resonance frequency ω

_T are separated by a bandwidth of no more than 3 db.

5. The wireless power unit as recited in claim 4, wherein the second resonator structure is in the tuned state when the second resonant frequency ω

₂ and the wireless transmitter resonance frequency ω

_T are separated by a bandwidth of no more than 3 db.

6. The wireless power unit as recited in claim 5, wherein the first resonator structure comprises:

a first resonating coil, the first resonating coil comprising;

a first central core region, and

a first plurality of loops of continuous conductive material circumferentially wrapped around the cylindrical central core region.

7. The wireless power unit as recited in claim 6, wherein the second resonator structure comprises:

a second resonating coil, the second resonating coil comprising;

a second central core region; and

a second plurality of loops of continuous conductive material circumferentially wrapped around the cylindrical central core region, wherein a first EMF induced in the first resonating coil does not induce an overall EMF in the second resonating coil.

8. The wireless power unit as recited in claim 6, wherein a length of the first resonating coil is in accordance with the characteristic size L₁.

9. The wireless power unit as recited in claim 6, wherein a length of the second resonating coil is in accordance with the characteristic size L₂.

10. The wireless power unit as recited in claim 9, a longitudinal axis of the first resonating coil is perpendicular to a longitudinal axis of the second resonating coil.

11. The wireless power unit as recited in claim 10, wherein in a first arrangement, a first end of the first resonating coil is proximate to and co-planar with a mid-point of the longitudinal axis of the second resonating coil.

12. The wireless power unit as recited in claim 1, wherein the power combining unit comprises:

an impedance matching network connected to the first and second resonator structures arranged to match a receiver impedance with a load impedance;

a rectifying circuit arranged to receive an AC signal from the impedance matching network and covert the AC signal to a DC signal; and

an OR circuit arranged to provide a load balancing function between the first and second resonator structures and the device.

13. The wireless power unit as recited in claim 12, wherein the first and second resonator structures are each modeled as an inductor having an inductance value L₁ and a series resistor R_s.

14. The wireless power unit as recited in claim 13, wherein impedance matching circuit comprises:

a capacitive network comprising;

a first capacitor having a first capacitance value C1; and

a second capacitor having a second capacitance value C2 connected in parallel with the first capacitor, wherein when the first and second resonator structures are tuned with an NFMR transmitter, the receiver inductors resonate with the capacitive network to match the load resistance of the device and the load resistance of the receivers.

15. The wireless power unit as recited in claim 14, wherein the rectifying circuit comprises a full bridge rectifier circuit further comprising a plurality of diodes.

16. The wireless power unit as recited in claim 15, wherein the OR circuit comprises at least one diode.

17. The wireless power unit as recited in claim 16, wherein the first and the second of the first and second resonator structures are electrically connected to each other by way of the OR circuit.

18. The wireless power unit as recited in claim 17, wherein the OR circuit comprises:

a storage element; and

a load balancing switch circuit having a first node connected to the storage element and a second node connected to the device, wherein a first node of the storage element is connected to an output node of the rectifying circuit and the first node of the switch circuit and a second node of the storage element is connected to ground, wherein the load balancing switch circuit are used to assure proper load balancing between first and second resonator structures thereby providing consistent power to the device.

19. A peripheral device arranged to wirelessly receive power from a NFMR power transmitter independent of the orientation of the peripheral device with respect to the NFMR power transmitter, comprising:

a wireless power receiving unit comprising;

at least two magnetically de-coupled near field magnetic resonance (NFMR) power receivers each arranged to receive power from a NFMR magnetic field;

a power combining circuit coupled to the at least two magnetically decoupled NFMR power receivers arranged to;

load match the at least two NFMR power receivers and the device,

load balance power from the at least two NFMR power receivers, and

maintain an effective magnetic coupling coefficient between the at least two magnetically de-coupled NFMR power receivers at about zero regardless of a spatial orientation of the wireless power unit with regards to the NFMR magnetic field such that the device wirelessly receives the substantial constant power from the wireless power unit regardless of an orientation of the at least two NFMR power receivers with respect to the NFMR magnetic field.

20. The peripheral device as recited in claim 19, wherein the power combining unit comprises:

an impedance matching network connected to the at least two NFMR power receivers arranged to match a receiver impedance with a load impedance;

a rectifying circuit arranged to receive an AC signal from the impedance matching network and covert the AC signal to a DC signal; and

an OR circuit arranged to provide a load balancing function between the at least two magnetically de-coupled NFMR power receivers and the device.

21. The peripheral device as recited in claim 20, wherein the at least two NFMR power receivers are each modeled as an inductor having an inductance value L₁ and a series resistor R_s.

22. The peripheral device as recited in claim 21, wherein impedance matching circuit comprises:

a capacitive network comprising;

a first capacitor having a first capacitance value C1; and

a second capacitor having a second capacitance value C2 connected in parallel with the first capacitor, wherein when the at least two NFMR receivers are in resonance mode with an NFMR transmitter, the receiver inductors resonate with the capacitive network to match the load resistance of the device and the load resistance of the receivers.

23. The peripheral device as recited in claim 22, wherein the rectifying circuit comprises a full bridge rectifier circuit further comprising a plurality of diodes.

24. The peripheral device as recited in claim 23, wherein the OR circuit comprises at least one diode.

25. The peripheral device as recited in claim 24, wherein the peripheral device includes at least three NFMR power receivers that are arranged perpendicular to each other such that when the peripheral device is moved to within any position within a three dimensional spatial volume, there is no substantial loss in power wirelessly received from an NFMR power transmitter.