Inductively-powered power transfer system with one or more independently controllable loads

• US 7,633,235 B2
• Filed: 09/29/2004
• Issued: 12/15/2009
• Est. Priority Date: 09/29/2003
• Status: Active Grant

• Current Assignee: Auckland UniServices Limited (Auckland University)
• Original Assignee: Auckland UniServices Limited (Auckland University)
• Inventors: Boys, John Talbot
• Primary Examiner(s): Owens; Douglas W
• Assistant Examiner(s): Chen; Jianzi
• Application Number:
  US10/574,162
• Publication Number:
  US 20080129215A1
• Time in Patent Office: 1,903 Days
• Field of Search: 315/177, 315/185.R, 315/186, 315/200.R, 315/201, 315/200.A, 315/209.R, 315/210, 315/212, 315/219, 315/246, 315/276, 315/283, 315/287, 315/289, 315/291, 313/1.R, 313/3, 313/5, 313/18, 313/23, 313/25, 313/34, 313/35, 313/DIG.3, 307/104, 307/145, 307/147, 307/148
• US Class Current: 315/209.00R
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H03D 3/04 by counting or integrating cycles of oscillations arrangements for measuring frequencies G01R23/10

Abstract

The present invention provides a system for controlling one or more operating unites in an inductive power transfer (IPT) system. Each operating unit includes a pick-up coil that takes power from a primary conductor or track over an air gap. The operating unit is controlled by frequency modulating the primary conductor power supply to send a control instruction which is decoded by the operating unit. The instruction is decoded by generating a signal using a local oscillator in the operating unit and using the signal to detect changes in the frequency of the current in the primary conductor. Such a system can be used, for example, to control inductively powered road-studs that include a light source for controlling traffic on a roadway. A narrow band modulated data transmission system and method for controlling an operating unit are also provided.

Claims

1. A method of controlling an inductively-powered operating unit for use in association with an inductive power transfer (IPT) system, the method comprising the steps of:

frequency modulating a current in a primary conductor circuit of the IPT system; and

,

in the operating unit;

(a) detecting a frequency of current in the primary conductor circuit;

(b) generating a local oscillator signal;

(c) using the local oscillator signal to detect a change in the frequency of the primary circuit current; and

(d) using the detected change to control the operating unit.

2. A method as claimed in claim 1 further comprising the step of using the detected frequency to ascertain a frequency of the local oscillator signal.

3. A method as claimed in claim 1 wherein the step of generating the local oscillator further comprises the step of:

generating a local oscillator of a known frequency with respect to an unmodulated frequency of the primary circuit current.

4. A method as claimed in claim 1 wherein the step of detecting a change in the frequency of the primary circuit current further comprises the steps of:

subtracting the local oscillator signal from the detected frequency to provide an information signal; and

detecting a change in the frequency of the information signal.

5. A method as claimed in claim 4 wherein in the step of subtracting comprises the step of using a sample and hold circuit to sample the detected frequency signal to provide the information signal.

6. A method as claimed in claim 5 further comprising the step of sampling the detected frequency at the frequency of the local oscillator signal.

7. A method as claimed in claim 4 further comprising the step of detecting the frequency of the information signal by counting the number of cycles or part cycles of an oscillating signal of constant frequency in each cycle or part cycle of the information signal.

8. A method as claimed in claim 7 further comprising the step of counting the number of cycles or part cycles of the current in the primary conductor circuit in each cycle or part cycle of the information signal.

9. A method as claimed in claim 1 wherein the step of detecting a change in the frequency of the primary circuit current further comprises the steps of:

using the local oscillator signal to alias down the detected frequency to provide an information signal; and

detecting a change in the frequency of the information signal.

10. A method as claimed in claim 9, wherein the step of aliasing further comprising the step of using a sample and hold circuit to sample the detected frequency signal to provide the information signal.

11. A method as claimed in claim 1, further comprising the step of calibrating the frequency of the local oscillator signal with the frequency of the current in the primary conductor circuit.

12. A method as claimed in claim 11 wherein the step of calibrating further comprises the steps of:

detecting the frequency of the information signal;

analyzing the frequency over a pre-determined time period to obtain a frequency reference;

comparing the frequency reference with a datum; and

increasing or decreasing the local oscillator frequency to effect calibration.

13. A method as claimed in claim 1, further comprising the steps of:

establishing at least one pre-determined threshold associated with the frequency of the information signal; and

comparing the frequency of the information signal with the threshold to provide a digital output signal for control of the operating unit.

14. A method as claimed in claim 1, further comprising the steps of:

modulating the primary conductor current to provide an instruction to the operating unit;

detecting one or more frequency changes associated with the modulation at the operating unit to decode the instruction; and

controlling the operating unit in accordance with the instruction.

15. A controlled inductively powered unit for use in association with an inductive power transfer (IPT) system having a primary conductor circuit with a modulated current, the operating unit comprising:

a signal detection unit operable to detect a frequency of current in the primary conductor circuit;

a local oscillator unit operable to provide a local oscillator signal;

a signal processing unit operable to use the local oscillator signal to detect a change in the frequency of the primary conductor current; and

a control unit operable to control the operating unit dependent on the detected change.

16. A controlled inductively powered unit as claimed in claim 15 wherein the signal processing unit ascertains a frequency of the local oscillator using the detected frequency provided by the signal detection unit.

17. A controlled inductively powered unit as claimed in claim 15 wherein the local oscillator unit provides a local oscillator signal of a known frequency with respect to the unmodulated frequency of the primary circuit current.

18. A controlled inductively powered unit as claimed in claim 15 wherein the signal detection unit provides a detected frequency signal representative of the frequency of the primary conductor current and comprises a comparison unit to compare the frequency of the local oscillator signal with the frequency of the detected frequency signal to ascertain the frequency of the local oscillator signal.

19. A controlled inductively powered unit as claimed in claim 15 wherein the signal detection unit provides a detected frequency signal representative of the frequency of the primary conductor current and comprises a frequency subtraction unit operable to subtract the local oscillator signal from the detected frequency signal and provide an information signal for detecting the change in frequency of the primary conductor current.

20. A controlled inductively powered unit as claimed in claim 19 wherein the frequency subtraction unit samples the detected frequency signal at the frequency of the local oscillator.

21. A controlled inductively powered unit as claimed in claim 19 further comprising a counter to detect the frequency of the information signal by counting the number of cycles or part cycles of an oscillating signal of constant frequency in each cycle or part cycle of the information signal.

22. A controlled inductively powered unit as claimed in claim 21 wherein the counter counts the number of cycles or part cycles of the primary conductor current circuit in each cycle or part cycle of the information signal.

23. A controlled inductively powered unit as claimed in claim 19 further comprising a comparator having a pre-determined threshold at one input and a signal representative of the frequency of the information signal at another input to provide a digital output signal for control of the operating unit.

24. A controlled inductively powered unit as claimed in claim 15 wherein the signal detection unit provides a detected frequency signal representative of the frequency of the primary conductor current and comprises a sampling unit which samples the detected frequency signal and provides an information signal for detecting the change in frequency of the primary conductor current.

25. A controlled inductively powered unit as claimed in claim 24 wherein the sampling unit samples the detected frequency signal at the frequency of the local oscillator.

26. A controlled inductively powered unit as claimed in claim 15 further comprising a calibration unit operable to calibrate the local oscillator signal frequency with the frequency of the current in the primary conductor circuit.

27. An inductive power transfer (IPT) system including a primary conductor circuit and one or more controlled inductively powered units as claimed in claim 15 associated with the primary conductor circuit and adapted to receive power inductively from the primary conductor circuit, wherein the primary conductor circuit comprises a frequency modulation unit operable to modulate the frequency of current in the primary conductor circuit.

28. A roadway lighting system comprising a plurality of separately controllable road-studs, each road-stud comprising:

a light emitting element and being powered inductively via a primary conductor circuit buried under or in a roadway,

a frequency modulation unit adapted to modulate current in the primary conductor circuit, and

wherein each controllable road-stud comprises;

a signal detection unit operable to detect the frequency of current in the primary conductor circuit;

a local oscillator unit operable to provide a local oscillator signal;

a signal processing unit adapted to use the local oscillator signal to detect a change in the frequency of the primary conductor current; and

a control unit operable to control the operating unit dependent on the detected change.

29. A roadway lighting system as claimed in claim 28 wherein the roadway is an automobile roadway.

30. A roadway lighting system as claimed in claim 28 wherein the roadway is an aircraft runway or taxiway.

31. A roadway lighting system as claimed in claim 28 wherein the roadway is a sidewalk or footpath.

32. A narrow band modulated data transmission system for controlling one or more light emitting units, the system comprising:

a transmission unit operable to transmit a modulated signal, and each of the one or more light emitting units comprising;

a reception unit tuned to receive the modulated signal,

a detection unit operable to detect the data present in the received signal, and

wherein the total power to operate the light emitting unit is derived from the received signal.

33. A narrow band modulated data transmission system as claimed in claim 32 wherein the transmitted signal is a frequency modulated signal.

34. A method of controlling one or more light emitting units comprising the steps of:

transmitting a narrow band modulated signal;

receiving the modulated signal at a light emitting unit;

detecting a data present in the received signal;

controlling the light emitting unit dependent on the detected data; and

using the received signal to provide the total power to operate the light emitting unit.

35. A method as claimed in claim 34 further comprising the step of transmitting a narrow band frequency modulated signal.

36. A method of controlling traffic on a road, the method including the steps of:

incorporating a road way lighting system comprising a plurality of separately controllable road-studs into or onto the road, each road-stud comprising a light emitting element and being powered inductively via a primary conductor circuit buried under or in a roadway, a frequency modulation unit adapted to modulate current in the primary conductor circuit, and wherein each controllable road-stud comprises;

a signal detection unit operable to detect a frequency of current in the primary conductor circuit;

a local oscillator unit operable to provide providing a local oscillator signal;

a signal processing unit adapted to use the local oscillator signal to detect a change in the frequency of the primary conductor current; and

a control unit operable to control the operating unit dependent on the detected change, and

modulating the frequency of current in the primary conductor circuit to initiate a pattern of operation of each controllable road-stud such that the plurality of road-studs provide a message to users of the road.

37. A method as claimed in claim 36 further comprising the step of modulating the frequency such that the message includes sequential flashing of the controllable road-studs to indicate a direction.

38. A method as claimed in claim 37 wherein the step of sequential flashing involves activating all the light emitting elements and sequentially deactivating a minority of the light emitting elements.

39. A method as claimed in claim 36 further comprising the step of modulating the frequency such that the message includes sequential flashing of the controllable road-studs to indicate a speed limit.

40. A method as claimed in claim 39, wherein the step of sequential flashing involves activating all the light elements and sequentially deactivating a minority of the light emitting elements.

41. A controllable road-stud system comprising:

a power supply for generating a substantially sinewave current in a primary conductive path wherein a frequency of the current can be modulated,

a plurality of active nodes tuned to the power supply frequency located at specific points along the primary conductive path,

a road-stud tuned to the power supply frequency located in close proximity to each of the active nodes, each road-stud including;

a pick-up coil with a tuning capacitor,

a rectification unit operable to produce a DC source of power,

a control unit operable to control a power flow from the primary conductive path to the road-stud,

a light source in series with a controllable switch connected across the DC source of power and active to switch the light source on or off,

a signal detection unit operable to detect a frequency of the current in the primary conductive path or the current in the pick-up coil,

a unit operable to produce a local oscillator signal at a known frequency relative to the detected frequency,

a tracking unit operable to track the local oscillator signal frequency against variations in frequency or components unit operable to produce a signal representative of the difference frequency between the detected frequency and the frequency of the local oscillator signal,

a counting unit operable to count a number of cycles of the detected frequency in one cycle of the difference signal,

a comparator unit operable to determine whether the counted number of cycles is greater or less than a comparison fixed number to provide a decoded output, and

a processor unit operable to control the light source on the road-stud according to the decoded output.

42. A controllable road-stud for use in association with an inductive power transfer (IPT) system having a primary conductive path with a frequency modulated current, the road-stud comprising:

a signal producing device operable to produce a local oscillator signal in the road-stud of known accuracy with respect to an unmodulated frequency of the current in the track,

a unit operable to use the local oscillator signal to detect changes in the frequency of the current in the primary conductive path,

a conversion unit operable to convert the detected changes to digital form to produce binary output representative of the modulation of the frequency of the current in the primary conductive path,

a processing device for interpreting the binary output and

a driving switch for switching a light source powered by the road-stud on or off as appropriate.

43. A controllable road-stud as claimed in claim 42 wherein variations in the local oscillator frequency caused by component differences or changes in temperature or time are compensated for even though these changes may be significantly larger than the controlled frequency changes in the track current.

44. A controllable road-stud as claimed in claim 42 wherein the primary conductive path includes one or more active nodes.

45. A controllable road-stud as claimed in claim 44 further comprising:

a pick-up coil, and

wherein variations in the tuning of the active node or the pick-up coil have substantially no affect on the ability of the apparatus to produce and process the binary output.

46. A controllable road-stud as claimed in claim 42 wherein the modulation of the current in the primary conductive path is in a range of substantially 1-1.5% of the unmodulated frequency of the current in the primary conductive path.

47. A controllable road-stud as claimed in claim 42 wherein the light source is capable of displaying more than one colour or a plurality of light sources are provided, and the processor may selectively switch that colour or those colours on or off in a desired sequence or pattern.

48. A road-stud system including a controllable road-stud as claimed in claim 42, further comprising one or more uncontrolled road-studs, wherein all the road-studs being powered from the same primary conductive path and all the road-studs function without affecting each other.

49. A road-stud system as claimed in claim 48 wherein each controlled road-stud can operate one or more light sources of different colours in any desired sequence of patterns and colours.

50. A system for controlling one or more light emitting units, the system comprising:

a narrow band modulated data transmission system for controlling one or more light emitting units, the data transmission system comprising;

a transmission unit operable to transmit a modulated signal, and each of the one or more light emitting units comprising;

a reception unit tuned to receive the modulated signal, and

a detection unit operable to detect the data present in the received signal, and

an IPT system, the IPT system providing power to the light emitting unit.