Methods and apparatus for providing a sufficiently stable power to a load in an energy transfer system

• US 6,442,434 B1
• Filed: 08/09/2000
• Issued: 08/27/2002
• Est. Priority Date: 10/19/1999
• Status: Expired due to Term

• Current Assignee: Abiomed, Inc. (Johnson & Johnson)
• Original Assignee: Abiomed, Inc. (Johnson & Johnson)
• Inventors: Zarinetchi, Farhad, Keville, Stephen J.
• Primary Examiner(s): Jastrzab, Jeffrey R.
• Assistant Examiner(s): Oropeza, Frances P.
• Application Number:
  US09/635,050
• Time in Patent Office: 748 Days
• Field of Search: 607/2, 607/17, 607/32, 607/33, 607/61, 607/62
• US Class Current: 607/61
• CPC Class Codes: A61M 2205/8243 by induction
• CPC Class Codes: A61M 60/165 implantable in, on, or around the heart
• CPC Class Codes: A61M 60/178 drawing blood from a ventricle and returning the blood to the arterial system via a cannula external to the ventricle, e.g. left or right ventricular assist devices
• CPC Class Codes: A61M 60/196 replacing the entire heart, e.g. total artificial hearts [TAH]
• CPC Class Codes: A61M 60/216 including a rotating member acting on the blood, e.g. impeller
• CPC Class Codes: A61M 60/873 specially adapted for wireless or transcutaneous energy transfer [TET], e.g. inductive charging
• CPC Class Codes: A61N 1/00 Electrotherapy; Circuits therefor A61N2/00 takes precedence; irradiation apparatus A61N5/00
• CPC Class Codes: A61N 1/3787 from an external energy source
• CPC Class Codes: H02J 2310/23 The load being a medical device, a medical implant, or a life supporting device
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 50/90 involving detection or optimisation of position, e.g. alignment
• CPC Class Codes: Y10S 323/911 Medical electronics

Abstract

Methods and apparatus for providing a sufficiently stable power to a load in an energy transfer system that transfers energy from one side of a physical boundary to another side of the boundary. In one example, a power supply and a primary winding are located on a first side of a physical boundary (e.g., external to a body), and a secondary winding and the load are located on a second side of the physical boundary (e.g., internal to the body). A primary voltage across the primary winding is regulated so as to provide a sufficiently stable output power to the load notwithstanding changes in the load and/or changes in a relative position of the primary winding and the secondary winding. One aspect of the invention relates to energy transfer methods and apparatus for use in connection with the human body. In particular, one example of the invention includes a transcutaneous energy transfer (TET) system for transferring power from a power supply external to the body to a device implanted in the body.

Claims

1. An energy transfer system for transferring power from a power supply located on a first side of a physical boundary to a variable load located on a second side of the physical boundary, the energy transfer system comprising:

a variable load comprising an implantable medical device;

a primary winding electrically coupled to the power supply to generate a magnetic field based on input power provided by the power supply, the magnetic field permeating the physical boundary;

a secondary winding magnetically coupled to the primary winding via the magnetic field to form a power channel between the windings through which at least a portion of the magnetic field is received by the secondary winding, the secondary winding electrically coupled to the variable load to provide output power to the variable load based on the received magnetic field;

a first control circuit electrically coupled to the primary winding to regulate a primary voltage across the primary winding such that a sufficiently stable output power is provided to the variable load notwithstanding at least one of changes in the variable load and changes in a relative position of the primary winding and the secondary winding; and

a second control circuit electrically coupled to the secondary winding to provide a detectable indication on the power channel that indicates a characteristic of the variable load compared to a predetermined threshold for that characteristic;

wherein the first control circuit regulates the primary voltage based on the detectable indication provided on the power channel.

2. The system of claim 1, wherein the first control circuit regulates a load voltage across the variable load based on at least one of the changes in the variable load and the changes in the relative position of the primary winding and the secondary winding.

3. The system of claim 1, wherein the first control circuit regulates the primary voltage based on at least one of the changes in the load and the changes in the relative position of the primary winding and the secondary winding.

4. The system of claim 3, wherein:

the first control circuit obtains information related to at least one of the changes in the variable load and the changes in the relative position of the primary winding and the secondary winding via the power channel.

5. The system of claim 4, wherein the power channel has essentially a constant frequency.

6. The system of claim 1, wherein the first control circuit includes:

at least one capacitor coupled to the primary winding to form a primary resonant circuit with the primary winding;

an excitation circuit coupled to at least the power supply and the primary resonant circuit to provide an input power to the primary resonant circuit; and

an excitation control circuit coupled to the excitation circuit and the primary winding to control the excitation circuit so as to regulate the primary voltage.

7. The system of claim 6, wherein the excitation control circuit controls the excitation circuit based on a comparison of a reference voltage and a primary amplitude of the primary voltage.

8. The system of claim 7, wherein:

the excitation circuit outputs a plurality of pulses to the primary resonant circuit to provide the input power to the primary resonant circuit; and

the excitation control circuit controls a width of the pulses output by the excitation circuit such that the primary amplitude is approximately equal to a predetermined amplitude that is proportional to the reference voltage.

9. The system of claim 1, wherein the second control circuit provides a detectable indication on the power channel that indicates when a load voltage across the variable load exceeds a predetermine threshold load voltage.

10. The system of claim 9, wherein the first control circuit regulates the primary voltage such that the load voltage approximates the predetermined threshold load voltage notwithstanding at least one of the changes in the variable load and changes in the relative position of the primary winding and the secondary winding.

11. The system of claim 9, wherein the first control circuit includes a detector circuit coupled to the primary windily to detect the detectable indication on the power channel.

12. The system of claim 11, wherein the first control circuit increases a primary amplitude of the primary voltage if the detector circuit does not detect the detectable indication and decreases the primary amplitude if the detector circuit detects the detectable indication.

13. The system of claim 11, wherein:

the detectable indication includes at least one surge in the primary amplitude; and

the detector circuit includes a surge detector.

14. An energy transfer system for transferring power from a power supply located on a first side of a physical boundary to a variable load located on a second side of the physical boundary, the energy transfer system comprising:

a variable load comprising an implantable medical device;

a primary winding electrically coupled to the power supply to generate a magnetic field based on input power provided by the power supply, the magnetic field permeating the physical boundary;

a secondary winding magnetically coupled to the primary winding via the magnetic field to form a power channel between the windings through which at least a portion of the magnetic field is received by the secondary winding the secondary winding electrically coupled to the variable load to provide output power to the variable load based on the received magnetic field;

a first control circuit electrically coupled to the primary winding to regulate a primary voltage across the primary winding such that a sufficiently stable output power is provided to the variable load notwithstanding at least one of changes in the variable load and changes in a relative position of the primary winding and the secondary winding; and

a second control circuit electrically coupled to the secondary winding to provide a detectable indication on the power channel that indicates that a load voltage across the variable load exceeds a predetermined threshold load voltage the detectable indication including at least one surge in primary amplitude and the second control circuit including a comparator to make a comparison of the load voltage to the predetermined threshold load voltage and a surge generator coupled to the comparator to generate the at least one surge based on the comparison;

wherein the first control circuit includes a detector circuit coupled to the primary winding, to detect the detectable indication on the power channel, the detector circuit includes a surge detector, and the first control circuit regulates the primary voltage based on the detectable indication provided on the power channel.

15. The system of claim 14, wherein the surge generator includes a shunt circuit that diverts the output power provided by the secondary winding away from the variable load when an input signal to the shunt circuit reaches a shunt activation level, the comparator providing the input signal having the shunt activation level when the load voltage exceeds the predetermined threshold load voltage.

16. The system of claim 15, wherein the first control circuit regulates the primary voltage such that the input signal to the shunt circuit approximates and substantially remains below the shunt activation level.

17. The system of claim 15, wherein the first control circuit regulates the primary voltage such that the shunt circuit has a duty cycle of less than approximately 1%.

18. The system of claim 14, wherein the first control circuit regulates the primary voltage based on a varying reference voltage that is derived from the detectable indication.

19. The system of claim 18, wherein the first control circuit includes a reference control circuit to generate the varying reference voltage, the reference control circuit including:

the detector circuit to detect the detectable indication on the power channel and to provide a detected indication signal;

a timer circuit coupled to the detector circuit to receive the detected indication signal; and

an output circuit coupled to the timer circuit,

wherein the timer circuit controls the output circuit to output the varying reference voltage based on the detected indication signal.

20. The system of claim 19, wherein the timer circuit controls the output circuit such that the output circuit outputs the varying reference voltage as an essentially triangular waveform.

21. The system of claim 19, wherein the timer circuit controls the output circuit such that the output circuit outputs the varying reference voltage as an essentially saw-tooth waveform.

22. The system of claim 19, wherein the varying reference voltage has a frequency in a range of from approximately 5 Hz to approximately 40 Hz.

23. The system of claim 19, wherein the first control circuit further includes:

at least one capacitor coupled to the primary winding to form a primary resonant circuit with the primary winding;

an excitation circuit coupled to at least the power supply and the primary resonant circuit to provide an input power to the primary resonant circuit; and

an excitation control circuit, coupled to the excitation circuit, the primary winding, and the reference control circuit, to control the excitation circuit based on the primary voltage and the varying reference voltage.

24. The system of claim 23, wherein:

the excitation circuit outputs a plurality of pulses to the primary resonant circuit to provide the input power to the primary resonant circuit; and

the excitation control circuit controls a width of the pulses output by the excitation circuit such that a primary amplitude of the primary voltage is approximately equal to a predetermined amplitude that is proportional to the varying reference voltage.

25. The system of claim 24, wherein the detector circuit is coupled to the excitation circuit so as to control the input power provided by the excitation circuit to the primary resonant circuit based on at least the detectable indication.

26. The system of claim 25, wherein the detectable indication includes at least one surge in the primary amplitude.

27. The system of claim 14, wherein the surge generator includes a shunt circuit that diverts the output power provided by the secondary winding away from the variable load when an input signal to the shunt circuit reaches a shunt activation level, the comparator providing the input signal having the shunt activation level when the load voltage exceeds the predetermined threshold load voltage.

28. The system of claim 27, wherein the first control circuit regulates the primary voltage such that the input signal to the shunt circuit approximates and substantially remains below the shunt activation level.

29. The system of claim 27, wherein the first control circuit regulates the primary voltage such that the shunt circuit has a duty cycle of less than approximately 1%.

30. In an energy transfer system that includes a primary winding electrically coupled to a power supply located on a first side of a physical boundary, the energy transfer system further including a secondary winding electrically coupled to a variable load located on a second side of the physical boundary, wherein power is transferred from the power supply to the variable load via a power channel and a magnetic field that couples the primary and secondary windings forms a portion of the power channel, a method of transferring power from the power supply to the variable load comprising:

providing a variable load comprising an implantable medical device;

comparing a characteristic of the variable load to a predetermined threshold for that characteristic on the second side of the physical boundary;

generating a detectable indication based on the comparison for transmission across the physical boundary on the power channel by the secondary winding;

detecting the detectable indication on the first side of the physical boundary; and

regulating a primary voltage across the primary winding based on the detected indication so as to provide a sufficiently stable output power to the variable load not withstanding at least one of changes in the variable load and changes in a relative position of the primary winding and the secondary winding.

31. The method of claim 30, wherein the act of regulating a primary voltage includes an act of regulating the primary voltage based on at least one of the changes in the variable load and the changes in the relative position of the primary winding and the secondary winding.

32. The method of claim 31, wherein the act of regulating includes an act of:

obtaining information related to at least one of the changes in the variable load and the changes in the relative position of the primary winding and the secondary winding via the power channel.

33. The method of claim 32, wherein the power channel has essentially a constant frequency.

34. The method of claim 30, wherein the act of regulating includes an act of regulating the primary voltage based on a comparison of a reference voltage and the primary voltage.

35. The method of claim 34, wherein the energy system further includes at least one capacitor coupled to the primary winding to form a primary resonant circuit, and wherein the act of regulating includes an act of:

controlling a width of pulses input to the primary resonant circuit so as to regulate an input power to the primary resonant circuit.

36. The method of claim 35, wherein the act of controlling a width of pulses includes an act of controlling the width of the pulses such that a primary amplitude of the primary voltage is approximately equal to a predetermined amplitude that is proportional to the reference voltage.

37. The method of claim 30, wherein the method further includes an act of:

generating a detectable indication on the power channel that indicates when a load voltage across the variable load exceeds a predetermined threshold load voltage.

38. The method of claim 30, wherein the act of regulating includes an act of regulating the primary voltage such that a load voltage across the variable approximates the predetermined threshold load voltage notwithstanding at least one of the changes in the variable load and the changes in the relative position of the primary winding and the secondary winding.

39. The method of claim 30, wherein the act of regulating includes acts of:

increasing a primary amplitude of the primary voltage if a detector circuit does not detect the detectable indication; and

decreasing the primary amplitude if the detector circuit detects the detectable indication.

40. The method of claim 39, wherein:

the act of generating a detectable indication includes an act of generating at least one surge in the primary amplitude; and

the act of detecting the detectable indication includes an act of detecting the at least one surge in the primary amplitude.

41. In an energy transfer system that includes a primary winding electrically coupled to a power supply located on a first side of a physical boundary, the energy transfer system further including a secondary winding electrically coupled to a variable load located on a second side of the physical boundary, wherein power is transferred from the power supply to the variable load via a power channel and a magnetic field that couples the primary and secondary windings forms a portion of the power channel, a method of transferring power from the power supply to the variable load comprising:

providing a variable load comprising an implantable medical device;

making a comparison of a load voltage across the variable load to a predetermined threshold load voltage on the second side of the physical boundary;

generating a detectable indication based on the comparison for transmission across the physical boundary on the power channel by the secondary winding, generating a detectable indication including generating at least one surge in a primary amplitude of a primary voltage based on the comparison;

detecting the detectable indication on the first side of the physical boundary, detecting, the detectable indication including detecting the at least one surge in the primary amplitude; and

regulating the primary voltage across the primary winding based on the detected indication so as to provide a sufficiently stable output power to the variable load notwithstanding at least one of changes in the variable load and changes in a relative position of the primary winding and the secondary winding wherein the regulating includes increasing the primary amplitude of the primary voltage if a detector circuit does not detect the detectable indication and decreasing the primary amplitude if the detector circuit detects the detectable indication.

42. The method of claim 41, wherein the act of generating the at least one surge based on the comparison includes acts of:

diverting an output power provided by the secondary winding away from the variable load when an activation signal is generated; and

generating the activation signal when the load voltage exceeds the predetermined threshold load voltage.

43. The method of claim 42, wherein the act of regulating the primary voltage includes an act of regulating the primary voltage such that the load voltage approximates and substantially remains below the predetermined threshold load voltage.

44. The method of claim 42, wherein the act of regulating includes an act of regulating the primary voltage such that the activation signal has a duty cycle of less than approximately 1%.

45. The method of claim 41, wherein the act of regulating the primary voltage includes an acts of:

generating a varying reference voltage based on the detectable indication; and

regulating the primary voltage based on the varying reference voltage.

46. The method of claim 45, wherein the act of generating the varying reference voltage includes an act of generating the varying reference voltage as an essentially triangular waveform.

47. The method of claim 45, wherein the act of generating the varying reference voltage includes an act of generating the varying reference voltage as an essentially saw-tooth waveform.

48. The method of claim 45, wherein the act of generating the varying reference voltage includes an act of generating the varying reference voltage such that the varying reference voltage has a frequency in a range of from approximately 5 Hz to approximately 40 Hz.

49. The method of claim 45, wherein the energy system further includes at least one capacitor coupled to the primary winding to form a primary resonant circuit, and wherein the act of regulating includes an act of:

controlling a width of pulses input to the primary resonant circuit so as to control an input power to the primary resonant circuit based on at least the varying reference voltage.

50. The method of claim 49, wherein the act of controlling a width of pulses includes an act of controlling the width of the pulses such that a primary amplitude of the primary voltage is approximately equal to a predetermined amplitude that is proportional to the varying reference voltage.

51. The method of claim 50, wherein the act of controlling the input power includes an act of regulating the primary amplitude based on at least the detectable indication.

52. The method of claim 51, wherein:

the act of generating a detectable indication includes an act of generating at least one surge in the primary amplitude; and

the act of detecting the detectable indication includes an act of detecting the at least one surge in the primary amplitude.

53. The method of claim 52, wherein the act of generating at least one surge includes acts of:

making a comparison of the load voltage to the predetermined threshold load voltage; and

generating the at least one surge based on the comparison.

54. The method of claim 53, wherein the act of generating the at least one surge based on the comparison includes acts of:

diverting an output power provided by the secondary winding away from the variable load when an activation signal is generated; and

generating the activation signal when the load voltage exceeds the predetermined threshold load voltage.

55. The method of claim 54, wherein the act of regulating the primary amplitude includes an act of regulating the primary amplitude such that the load voltage approximates and substantially remains below the predetermined threshold load voltage.

56. The method of claim 54, wherein the act of regulating includes an act of regulating the primary amplitude such that the activation signal has a duty cycle of less than approximately 1%.