Wireless energy transfer system and method for feeding an electric load

• US 9,071,064 B2
• Filed: 12/29/2010
• Issued: 06/30/2015
• Est. Priority Date: 12/30/2009
• Status: Active Grant

• Current Assignee: Telecom Italia S.p.A.
• Original Assignee: Telecom Italia S.p.A.
• Inventors: Bella, Valter, Faraci, Felice Fulvio
• Primary Examiner(s): Kik, Phallaka
• Application Number:
  US13/519,841
• Publication Number:
  US 20120286728A1
• Time in Patent Office: 1,644 Days
• Field of Search: 320/108, 320/130, 320/133, 320/142, 320/145, 320/155, 307/27, 307/153
• US Class Current: 1/1
• CPC Class Codes: B60C 23/041 Means for supplying power to the signal- transmitting means on the wheel
• CPC Class Codes: B60C 23/0413 Wireless charging of active radio frequency circuits
• CPC Class Codes: B60C 23/0433 Radio signals
• CPC Class Codes: H02J 3/02 using a single network for simultaneous distribution of power at different frequencies; using a single network for simultaneous distribution of ac power and of dc power
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/00034 Charger exchanging data with an electronic device, i.e. telephone, whose internal battery is under charge
• CPC Class Codes: H04B 5/266 One coil at each side, e.g. with primary and secondary coils
• CPC Class Codes: H04B 5/79 for data transfer in combination with power transfer

Abstract

A wireless energy transfer system and an associated method for feeding an electric load are provided. The system includes a transmitter which includes a generator adapted to generate a radiofrequency signal at a first frequency and a first resonant circuit adapted to transmit the radiofrequency signal; and a receiver adapted to receive the radiofrequency signal and comprising a second resonant circuit. The second resonant circuit is adapted to be located in the non-radiative near field generated by the first resonant circuit, and the transmitter includes frequency sweeping functionality, which imposes on the radiofrequency signal generator a cyclic excursion of the first frequency in the neighborhood of a nominal frequency of the generator so that, when the first frequency matches the resonant frequency of the second resonant circuit, a non-radiative energy transfer occurs.

Claims

1. A wireless energy transfer system comprising:

a transmitter comprising a frequency sweeper, a radiofrequency signal generator adapted to generate a radiofrequency signal, and a first resonant circuit adapted to transmit a generated radiofrequency signal; and

a receiver adapted to receive the generated radiofrequency signal and comprising a second resonant circuit having a resonant frequency,

wherein the second resonant circuit is adapted to be located in a non-radiative near field generated by the first resonant circuit,

wherein, based on a signal outputted by the frequency sweeper, the radiofrequency signal generator—

is configured to generate a plurality of cycles of radiofrequency signals, wherein each radiofrequency signal in a cycle comprises a different frequency in a range of possible signal frequencies centered on a nominal frequency, wherein each cycle comprises at least one radiofrequency signal comprising a signal frequency that matches the resonant frequency and each cycle comprises at least one radiofrequency signal comprising a signal frequency that does not match the resonant frequency, and

wherein each radiofrequency signal in each cycle of radiofrequency signals is transmitted by the first resonant circuit having a first impedance.

2. A system according to claim 1, wherein the resonant frequency is time-varying.

3. A system according to claim 1, wherein the nominal frequency is periodically updated.

4. A system according to claim 1, wherein the signal outputted by the frequency sweeper drives a first varicap diode and a second varicap diode.

5. A system according to claim 1, wherein the transmitter further comprises, arranged between the first resonant circuit and the radiofrequency generator, an impedance matching circuit and a low-impedance interconnection cable.

6. A system according to claim 1, wherein the receiver further comprises, arranged between the second resonant circuit and a load, an impedance matching circuit, a low-impedance interconnection cable, and a diode rectifier and filtering circuit which converts received energy into direct current.

7. A system according to claim 1, wherein the first and second resonant circuits are loop resonators with a high Q factor.

8. A system according to claim 7, wherein at least one of the first resonant circuit and the second resonant circuit comprises a loop made of a conductive material strip.

9. A system according to claim 8, wherein the second resonant circuit comprises a capacitance, wherein a first end and a second end of the conductive material strip are misaligned and overlapped at a distance to create the capacitance.

10. A system according to claim 1, wherein the nominal frequency comprises a frequency between 1 MHz and 30 MHz.

11. A system according to claim 1, wherein the range corresponds to ±

1% of the nominal frequency.

12. A system according to claim 1, wherein the transmitter is adapted to:

scan a frequency range from a minimum frequency lower than the nominal frequency to a maximum frequency higher than the nominal frequency;

measure a current absorbed by the first resonant circuit for each scanned frequency in the frequency range;

determine a new frequency according to which a maximum current absorption by the first resonant circuit occurs; and

generate at least one radiofrequency signal comprising a frequency within a new range of possible radiofrequency signals, the new range centered on the new frequency.

13. A system according to claim 1, wherein said first resonant circuit is arranged on board a vehicle and the second resonant circuit is integrated into a tire of the vehicle.

14. A system according to claim 1, wherein the first resonant circuit is housed in an element of a bicycle stand, and the second resonant circuit is housed on board a bicycle, and wherein the second resonant circuit is configured to feed a rechargeable battery of the bicycle.

15. A vehicle comprising a system according to claim 1.

16. A method of wireless energy transfer, comprising the steps of:

transmitting a plurality of cycles of generated radiofrequency signals by a first resonant circuit, each generated radiofrequency signal comprising a frequency in a range of possible signal frequencies centered on a nominal frequency, wherein each cycle of radiofrequency signals comprises a plurality of radiofrequency signals, wherein each radiofrequency signal in the plurality of radiofrequency signals comprises a different frequency in a range of possible signal frequencies, wherein the range of possible signal frequencies comprises at least one signal frequency that matches a resonant frequency of a second resonant circuit and at least one signal frequency that does not match the resonant frequency of the second resonant circuit, and wherein each radiofrequency signal in each cycle of radiofrequency signals is transmitted by the first resonant circuit having a first impedance; and

receiving said plurality of radiofrequency signals by the second resonant circuit, wherein the second resonant circuit is located in a non-radiative near field generated by the first resonant circuit.

17. A method according to claim 16, comprising further steps of:

scanning a frequency range from a minimum frequency lower than the nominal frequency to a maximum frequency higher than the nominal frequency;

measuring a current absorbed by the first resonant circuit for each scanned frequency in the frequency range;

determining a new frequency according to which a maximum current absorption by the first resonant circuit occurs; and

generating at least one radiofrequency signal using the new frequency, wherein the generated at least one radiofrequency signal comprises a frequency within a new range of possible radiofrequency signals centered on the new frequency.

18. A method according to claim 17, wherein the further steps are executed at periodic time intervals.