EFFICIENT ROBUST WIRELESS ENERGY TRANSFER

• US 20120319498A1
• Filed: 03/03/2011
• Published: 12/20/2012
• Est. Priority Date: 03/04/2010
• Status: Active Grant

• Current Assignee: Yeda Research and Development Co. Ltd. (Weizmann Institute of Science)
• Original Assignee: Yeda Research and Development Co. Ltd. (Weizmann Institute of Science)
• Inventors: Silberberg, Yaron, Suchowski, Haim, Vitanov, Nikolay V., Rangelov, Andon A.
• Granted Patent: US 9,368,974 B2
• Time in Patent Office: Days
• 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

Abstract

A method or apparatus for transferring energy between a source coil and a drain coil, comprises setting an initial resonant frequency of the source coil as a first condition; setting the source coil and said drain coil in positions relative to each other to define an initial coupling coefficient therebetween, so that the initial coupling coefficient comprises a second condition; and adiabatically changing one or both of the conditions while pumping energy into the source coil. The source coil energy is transferred to the drain coil over the course of the adiabatic change.

Claims

1. A method of transferring energy between a source coil and a drain coil, comprising:

setting an initial resonant frequency of said source coil as a first condition;

setting said source coil and said drain coil in positions relative to each other to define an initial coupling coefficient therebetween, said initial coupling coefficient comprising a second condition; and

adiabatically changing at least one member of the group consisting of said first condition and said second condition while pumping energy into said source coil, thereby to transfer said pumped energy to said drain coil.

2. The method of transferring energy of claim 1, wherein both of said first condition and said second condition are adiabatically changed.

3. The method of transferring energy of claim 1, wherein said first condition is adiabatically changed.

4. The method of transferring energy of claim 1, wherein said second condition is adiabatically changed.

5. The method of transferring energy of claim 1, wherein said source coil is part of a resonant circuit having variable components to allow said initial resonant frequency to be changed.

6. The method of transferring energy of claim 1, wherein said source and drain coils are mobile with respect to each other, thereby to allow changing of said initial coupling coefficient.

7. The method of transferring energy of claim 2, wherein at any given time of said adiabatic changing there is a detuning value, said detuning value being the difference between a current value of the resonant frequency of the source coil and the resonant frequency of the drain coil, said adiabatic changing providing a smooth time dependence of the coupling coefficient (κ

(t)) and the detuning value (Δ

(t).

8. The method of transferring energy of claim 7, wherein said adiabatic changing comprises fulfilling an adiabatic condition relating said coupling coefficient and said detuning value:

|{dot over (κ

)}(t)Δ

(t)−

κ

(t){dot over (Δ

)}(t)|<

<

[4κ

²(t)+Δ

²(t)]^3/2.

9. The method of transferring energy of claim 7, wherein the coupling coefficient κ

(t) is relatively larger than a loss rate (Γ

), and wherein an initial and a final detuning are both relatively larger than the coupling coefficient, (Γ

<

κ

<

Δ

).

10. The method of transferring energy of claim 1, comprising varying the resonant frequency of the source coil such that a detuning value (Δ

(t)), said detuning value being a difference between the resonant frequency of the source coil and the resonant frequency of the drain coil, sweeps slowly from a negative value, said negative value being larger than the coupling between said source coil and said drain coil, to a positive value being larger than said coupling between said source coil and said drain coil.

11. The method of transferring energy of claim 1, comprising modifying said changing to reduce an amount of time that energy is retained in said source coil.

12. The method of claim 1, comprising varying said resonant frequency of said source coil by an amount of up to ten percent over a period of between one and three milliseconds.

13. The method of claim 1, comprising varying said resonant frequency of said source coil by an amount of up to ten percent over a period exceeding two milliseconds.

14. The method of claim 13, further comprising varying said coupling coefficient over said period.

15. Apparatus for transferring energy comprising:

a source coil having resonance variation circuitry for varying a resonant frequency of said source coil;

a position unit for varying a position or orientation of said source coil so as to vary a coupling coefficient of said source coil with a respective drain coil to which said source coil is wirelessly coupled;

and a controller configured to adiabatically vary at least one of said resonant frequency and said coupling coefficient while pumping energy into said source coil, thereby to transfer said pumped energy to said drain coil.

16. The apparatus of claim 15, wherein both of said resonant frequency and said coupling coefficient are adiabatically changed.

17. The apparatus of transferring energy of claim 15, wherein said resonant frequency is adiabatically changed.

18. The apparatus of claim 15, wherein said coupling coefficient is adiabatically changed.

19. The apparatus of claim 15, wherein said locating unit is operative to rotate said source coil, thereby to allow said adiabatic changing of said initial coupling coefficient.

20. The apparatus of claim 16, wherein at any given time of said adiabatic changing there is a detuning value, said detuning value being the difference between a current value of the resonant frequency of the source coil and the resonant frequency of the drain coil, said adiabatic changing providing a smooth time dependence of the coupling coefficient (κ

(t)) and the detuning value (Δ

(t).

21. The apparatus of claim 20, wherein the coupling coefficient κ

(t) is relatively larger than a loss rate (Γ

), and wherein an initial and a final detuning are both relatively larger than the coupling coefficient, (Γ

<

κ

<

Δ

).

22. The apparatus of claim 15, wherein said controller is configured to vary the resonant frequency of the source coil such that a detuning value (Δ

(t)), said detuning value being a difference between the resonant frequency of the source coil and the resonant frequency of the drain coil, sweeps slowly from a negative value, said negative value being larger than the coupling between said source coil and said drain coil, to a positive value being larger than said coupling between said source coil and said drain coil.

23. The apparatus of claim 15, wherein said controller is operative to modifying said changing to reduce an amount of time that energy is retained in said source coil.

24. The apparatus of claim 15, wherein said controller is operative to vary said resonant frequency of said source coil by an amount of up to ten percent over a period of between one and three milliseconds.

25. The apparatus of claim 15, wherein said controller is operative to vary said resonant frequency of said source coil by an amount of up to ten percent over a period exceeding two milliseconds.

26. The apparatus of claim 25, wherein said controller is operative to vary said coupling coefficient over said period.