WIRELESS POWER TRANSFER SYSTEMS FOR SURFACES

• US 20150372495A1
• Filed: 06/19/2015
• Published: 12/24/2015
• Est. Priority Date: 06/20/2014
• Status: Active Grant

• Current Assignee: WiTricity Corporation
• Original Assignee: WiTricity Corporation
• Inventors: McCauley, Alexander P., Roy, Arunanshu M., Katz, Noam, Kurs, Andre B., Kesler, Morris P.
• Granted Patent: US 9,954,375 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• 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 50/402 the two or more transmitting or the two or more receiving devices being integrated in the same unit, e.g. power mats with several coils or antennas with several sub-antennas
• CPC Class Codes: H02J 50/70 involving the reduction of electric, magnetic or electromagnetic leakage fields
• CPC Class Codes: H02J 50/90 involving detection or optimisation of position, e.g. alignment
• 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
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

The disclosure features wireless energy transfer sources that include at least two source resonators and a power source, where: each of the at least two source resonators has a nominal impedance when a device resonator is not positioned on or near any of the at least two source resonators, the nominal impedances of each of the at least two source resonators varying by 10% or less from one another; and the at least two source resonators are configured so that during operation of the wireless energy transfer source, when a device resonator is positioned on or near a first one of the at least two source resonators: (a) the impedance of the first source resonator is reduced to a value smaller than the nominal impedances of each of the other resonators by a factor of 2 or more.

Claims

1. A wireless energy transfer source, comprising:

at least two source resonators electrically connected in parallel and configured so that during operation, the at least two source resonators can each transfer energy wirelessly via an oscillating magnetic field to a device resonator; and

a power source coupled to a first tunable element and to each of the at least two source resonators, and configured so that during operation, the power source provides a supply of electrical current,

wherein each of the at least two source resonators has a nominal impedance when a device resonator is not positioned on or near any of the at least two source resonators, the nominal impedances of each of the at least two source resonators varying by 10% or less from one another; and

wherein the at least two source resonators are configured so that during operation of the wireless energy transfer source, when a device resonator is positioned on or near a first one of the at least two source resonators;

the impedance of the first source resonator is reduced such that the reduced impedance of the first source resonator is smaller than the nominal impedances of each of the other resonators by a factor of 2 or more; and

the first source resonator draws electrical current from the power source.

2. The source of claim 1, wherein the tunable element comprises at least one of a tunable capacitor, a tunable inductor, and a tunable resistor.

3. The source of claim 1, further comprising power and control circuitry configured to control the tunable element.

4. The source of claim 1, wherein a second one of the at least two source resonators draws current from the power source when the device resonator is positioned on or near both the first and second resonators.

5. The source of claim 1, wherein the at least two source resonators each comprise an S-shaped coil, and wherein the at least two resonators are nested within one another.

6. The source of claim 5, wherein each of the S-shaped coils is printed on a first layer of a circuit board and returning traces of the S-shaped coils are printed on a second layer of the circuit board.

7. The source of claim 6, wherein the device resonator comprises an S-shaped coil.

8. The source of claim 1, wherein the device resonator is part of a phone or a laptop.

9. The source of claim 1, wherein the source resonator is integrated into a surface of a table or desk.

10. The source of claim 3, wherein each of the at least two source resonators comprises a tunable capacitor.

11. The source of claim 2, wherein the power and control circuitry is configured to tune the tunable capacitor in response to the presence of a lossy object.

12. The source of claim 11, wherein the tunable capacitor comprises a bank of capacitors and wherein a capacitance of the bank of capacitors is controlled by a switch.

13. The source of claim 1, wherein each of the at least two source resonators comprises a tunable inductor.

14. The source of claim 13, wherein an inductance of each tunable inductor can be changed to adjust the impedance of each corresponding one of the at least two source resonators.

15. The source of claim 1, wherein the at least two source resonators are overlapped such that coupling between them is reduced, relative to the coupling that would result if the source resonators were positioned adjacent one another.

16. The source of claim 1, wherein each of the at least two source resonators have a quality factor Q>

100.

17. A method for tuning a wireless power source, the method comprising:

driving at least two source resonators with a power source coupled to a first tunable element and to each of the at least two source resonators, wherein the power source is configured to provide an electrical current supply; and

in response to the positioning of a device resonator on or near a first one of the at least two source resonators, supplying electrical current to the first source resonator to wirelessly transfer power from the first resonator to the device resonator,

wherein the positioning of the device resonator on or near the first source resonator reduces an impedance of the first source resonator by a factor of at least two relative to impedances of each of the other source resonators.

18. A wireless energy transfer system comprising:

a source comprising;

at least two source resonators electrically connected in parallel; and

a driving circuit coupled to a first tunable element and to each of the at least two source resonators, the driving circuit configured to provide a current supply; and

a device comprising at least one device resonator coupled to a load,

wherein the source is configured to transfer wireless energy via an oscillating magnetic field to the at least one device resonator;

wherein a first one of the at least two source resonators draws current from the driving circuit when the device resonator is positioned on or near the first of the at least two source resonators; and

wherein other resonators of the at least two source resonators are detuned when the device resonator is positioned on or near the first source resonator.

19. The system of claim 18, wherein the device comprises at least two device resonators.

20. The system of claim 19, wherein energy captured by the at least two device resonators is electrically combined to deliver power to the load.