System and method for magnetic power transfer

• US 8,614,526 B2
• Filed: 09/18/2008
• Issued: 12/24/2013
• Est. Priority Date: 09/19/2007
• Status: Active Grant

• Current Assignee: WiTricity Corporation
• Original Assignee: Qualcomm, Inc.
• Inventors: Cook, Nigel P., Dominiak, Stephen, Widmer, Hanspeter
• Primary Examiner(s): Amrany, Adi
• Application Number:
  US12/233,441
• Publication Number:
  US 20090102292A1
• Time in Patent Office: 1,923 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: H01Q 1/2225 used in active tags, i.e. provided with its own power source or in passive tags, i.e. deriving power from RF signal
• CPC Class Codes: H01Q 1/248 provided with an AC/DC converting device, e.g. rectennas
• CPC Class Codes: H01Q 7/00 Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop

Abstract

System and method for wireless power transfer based on values set to comply with limits from multiple different agencies.

Claims

1. A method in a wireless power transfer system, comprising:

receiving power from a power source;

providing a substantially unmodulated signal to a transmitter antenna;

generating, with the transmitter antenna, a substantially non-radiative electromagnetic field;

determining a geographic location of the transmitter antenna;

adjusting the electromagnetic field to have a field strength that complies with a standard safety level of the determined geographic location; and

transferring power via the substantially unmodulated signal and the substantially non-radiative electromagnetic field to a rechargeable battery of a wireless power receiver the transferred power being at a level sufficient for charging the rechargeable battery, the electromagnetic field having a first field strength that is compliant with a first power standard when the determined geographic location of the transmitter antenna corresponds to a first geographic location and having a second field strength that is compliant with a second power standard when the determined geographic location of the transmitter antenna corresponds to a second geographic location that is different from the first geographic location, and the second field strength being greater than the first field strength and non-compliant with the first power standard.

2. A method as in claim 1, wherein said wireless power transfer is configured to be carried out at at least one of a frequency of 13.56 MHz +/−

7 kHz and a frequency below 135 kHz.

3. A method as in claim 1, wherein said wireless power transfer system generates electromagnetic fields that are higher than electromagnetic fields allowed by the first power standard in areas of the first geographic location where a person cannot be located.

4. A method as in claim 1, wherein said wireless power transfer system generates fields at levels that are based on both biological effects and interference effects with other electronic devices.

5. A method as in claim 1, wherein the first power standard is set to avoid a first biological effect, wherein the second power standard is set to avoid a second biological effect, the method further comprising generating an electromagnetic field during substantially non-radiative energy transmission of the wireless power transfer system at a third filed strength set to comply with a third power standard when the transmitter is located in the first geographic location, wherein the third power standard is different than the first power standard, and wherein the third field strength is greater than the first field strength.

6. A method as in claim 1,

wherein the electromagnetic field has a field strength below a standard safety level of the determined geographic location.

7. A method as in claim 1, wherein the field strength of the electromagnetic field is at a level that avoids a corresponding biological effect.

8. The method of claim 1, wherein the first field strength corresponds to an electromagnetic field generated at a first frequency, the method further comprising generating an electromagnetic field during substantially non-radiative energy transmission of the wireless power transfer system at a second frequency and at a third field strength set to comply with the first power standard, the third field strength being greater than the first field strength.

9. The method of claim 1, further comprising adjusting at least one of said first field strength and said second field strength based on an input entered into said transmitter for complying with a power standard, said power standard corresponding to said input.

10. The method of claim 9, wherein said input is at least one of a predefined country code and a code embedded in an electrical tip, said electrical tip being placed on said transmitter.

11. The method of claim 1, wherein transferring said power comprises transferring said power through a multidirectional antenna via said substantially non-radiative electromagnetic field.

12. The method of claim 1, wherein transferring said power comprises transferring said power through a capacitively loaded dipole, wherein said capacitively loaded dipole comprises a wire loop, said wire loop having at least one loop of a coil in series with a capacitor.

13. The method of claim 1, wherein generating the substantially non-radiative electromagnetic field comprises generating a frequency of the field that is tuned to the antenna and is configured for FCC compliance.

14. The method of claim 1, wherein the antenna is an inductively loaded electrical dipole that is at least one of an open capacitor or dielectric disk.

15. A wireless power transfer system, comprising:

a transmitter configured to receive power from a power source and generate a substantially unmodulated signal; and

an antenna coupled to the transmitter and configured to receive the substantially unmodulated signal and generate a substantially non-radiative electromagnetic field that transfers power to a rechargeable battery of a wireless power receiver, the transferred power being at a level sufficient for charging the rechargeable battery,

wherein the electromagnetic field is adjusted to have a field strength that complies with a standard safety level at a determined geographic location of the transmitter antenna, the electromagnetic field having a first field strength that is compliant with a first power standard when the determined geographic location of the transmitter antenna corresponds to a first geographic location and having a second field strength that is compliant with a second power standard when the determined geographic location of the transmitter antenna corresponds to a second geographic location that is different from the first geographic location, and the second field strength being greater than the first field strength and non-compliant with the first power standard.

16. A system as in claim 15, wherein said transmitter is also compliant with a third power standard set by a third standards standard-setting agency set forth for a third geographic location.

17. A system as in claim 15, wherein said wireless power transfer is configured to be carried out at at least one of a frequency of 13.56 MHz +/−

7 kHz and a frequency below 135 kHz.

18. A system as in claim 15, wherein said transmitter generates an electromagnetic field corresponding to a field strength that is higher than the first power standard in an area of the first geographic location where a user cannot be located.

19. A system as in claim 15, wherein said transmitter is configured to generate the electromagnetic field to comply with a standard correlated with interference effects of the electromagnetic field.

20. A system as in claim 15, wherein the first power standard is set to avoid a first biological effect, wherein the second power standard is set to avoid a second biological effect, and wherein the transmitter is further configured to generate an electromagnetic field during substantially non-radiative energy transmission of the wireless power transfer system to comply with a third power standard set to avoid a third biological effect when the transmitter is located in the first geographic location, and wherein the third power standard is greater than the first power standard.

21. A system as in claim 15, further comprising:

an attachable unit configured to adjust the electromagnetic field.

22. A system as in claim 15, wherein the electromagnetic field has a field strength below both the first power standard and second power standard to avoid a corresponding to a biological effect.

23. The system of claim 15, wherein the first field strength corresponds to an electromagnetic field generated at a first frequency, and wherein the transmitter is configured to, when in operation, generate an electromagnetic field during substantially non-radiative energy transmission of the wireless power transfer system at a second frequency and at a third field strength set to comply with the first power standard, the third field strength being greater than the first field strength.

24. The system of claim 15, wherein said transmitter further adjusts at least one of said first field strength and said second field strength, based on an input received by said transmitter, for complying with a third power standard, said power standard corresponding to said input.

25. The system of claim 24, wherein said input is at least one of a predefined country code entered into said transmitter and a code embedded in an electrical tip and sensed by said transmitter, said electrical tip being placed on said transmitter.

26. The system of claim 15, wherein said transmitter further comprises a multidirectional antenna and transfers said power through said multidirectional antenna.

27. The system of claim 15, wherein said transmitter further comprises a dipole and transfers said power through said dipole, wherein said dipole is formed of a wire loop, said wire loop having at least one loop of a coil.

28. The system of claim 27, wherein said dipole further comprises a capacitor.

29. The system of claim 15, wherein the transmitter further comprises a frequency generator, the frequency generator tuned to the antenna and configured for FCC compliance.

30. The system of claim 15, wherein the antenna is an inductively loaded electrical dipole that is at least one of an open capacitor or dielectric disk.

31. The system of claim 15, wherein the antenna further comprises an inductive loop and a high Q resonant antenna part, the inductive loop substantially inductively coupled to the high Q resonant antenna part.

32. The system of claim 15, wherein the wireless power receiver comprises a receiving antenna and a rectifier, the rectifier configured to rectify an output of the receiving antenna.

33. A wireless power transfer system, comprising:

means for receiving power from a power source and for generating a substantially unmodulated signal; and

means for receiving the substantially unmodulated signal and for generating a substantially non-radiative electromagnetic field that transfers power to a rechargeable battery of a wireless power receiver, the transferred power being at a level sufficient to charge the rechargeable battery via the substantially unmodulated signal and the substantially non-radiative electromagnetic field, wherein the electromagnetic field is adjusted to have a field strength that complies with a standard safety level at a determined geographic location of the generating means, the electromagnetic field having a first field strength that is compliant with a first power standard when the determined location of the generating means corresponds to a first geographic location and having a second field strength that is compliant with a second power standard when the determined location of the generating means corresponds to a second geographic location that is different from the first geographic location, and the second field strength being greater than the first field strength and non-compliant with the first power standard.

34. A system as in claim 33, wherein the means for generating an electromagnetic field comprises a transmit coil, and wherein the means for transferring power comprises a controller.