WIRELESS ENERGY TRANSFER SYSTEM AND METHOD FOR FEEDING AN ELECTRIC LOAD

• US 20120286728A1
• Filed: 12/29/2010
• Published: 11/15/2012
• 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
• Granted Patent: US 9,071,064 B2
• Time in Patent Office: Days
• US Class Current: 320/108
• 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 generator adapted to generate a radiofrequency signal at a first frequency and a first resonant circuit adapted to transmit said radiofrequency signal;

a receiver adapted to receive said radiofrequency signal and comprising a second resonant circuit,

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

wherein said transmitter is configured to impose on said radiofrequency signal generator a cyclic excursion of said first frequency in a neighborhood of a nominal frequency of said generator so that, when said first frequency matches the resonant frequency of said second resonant circuit, a non-radiative energy transfer occurs.

2. A system according to claim 1, wherein said nominal frequency is time-varying.

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

4. A system according to claim 1, wherein said transmitter is configured to generate a variable signal that drives first and second varicap diodes so as to obtain said cyclic excursion.

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

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

7. A system according to claim 1, wherein said 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 said first and said second resonant circuits comprise a loop made of a conductive material strip.

9. A system according to claim 8, wherein the ends of said second resonant circuit are misaligned and overlapped at a suitable distance in order to create a capacitance.

10. A system according to claim 1, wherein said nominal frequency of said radiofrequency signal is comprised between 1 MHz and 30 MHz.

11. A system according to claim 1, wherein said neighborhood corresponds to ±

1% of said nominal frequency.

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

scan a frequency range in the neighborhood of the nominal frequency of said generator, from a minimum frequency to a maximum frequency;

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

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

generate the radiofrequency signal at said new frequency replacing said first frequency.

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

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

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

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

generating a radiofrequency signal at a first frequency by a generator;

transmitting said radiofrequency signal by a first resonant circuit;

receiving said radiofrequency signal by a second resonant circuit, adapted to be located in a non-radiative near field generated by said first resonant circuit,

imposing on said radiofrequency signal generator a cyclic excursion of said first frequency in a neighborhood of a nominal frequency of said generator so that, when said first frequency matches the resonant frequency of said second resonant circuit, a non-radiative energy transfer occurs.

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

scanning a frequency range in the neighborhood of the nominal frequency of said generator, from a minimum frequency to a maximum frequency;

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

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

generating the radiofrequency signal at said new frequency replacing said first frequency.

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