System and method for charging a power cell in an implantable medical device

• US 8,401,664 B2
• Filed: 04/29/2011
• Issued: 03/19/2013
• Est. Priority Date: 04/29/2011
• Status: Active Grant

• Current Assignee: LivaNova USA, Inc. (LivaNova Plc)
• Original Assignee: Cyberonics, Inc
• Inventors: Chow, Eric Y., Cowley, Anthony W., Thompson, David L., Shen, Jianxiang, Flesher, James L., Hussain, Saadat
• Primary Examiner(s): GETZOW, SCOTT M
• Application Number:
  US13/097,833
• Publication Number:
  US 20120277829A1
• Time in Patent Office: 690 Days
• Field of Search: 607 27- 33, 607/60, 607/61
• US Class Current: 607/61
• CPC Class Codes: A61N 1/3787 from an external energy source

Abstract

Apparatus and methods for charging a power cell in an implantable medical device (“IMD”) are disclosed herein. In one embodiment, a method includes providing an electrical pulse to an inductor external to the IMD. A frequency of an oscillation signal induced in the inductor by the current pulse is measured. The inductor is driven with an oscillating signal having a frequency based on the measured frequency of the oscillation signal. The power cell is charged using current induced in the IMD by the driving of the inductor.

Claims

1. A method for charging a power cell in an implantable medical device (IMD), comprising:

providing an electrical pulse to an inductor external to the IMD;

measuring a first frequency of an oscillation signal induced in the inductor by the electrical pulse; and

driving the inductor with a drive signal operative to induce a current in the IMD, the induced current operative to charge the power cell of the IMD, the drive signal having a second frequency based on the measured first frequency of the oscillation signal.

2. The method of claim 1, wherein the electrical pulse further comprises a rise time or a fall time operative to induce the oscillation signal.

3. The method of claim 1, wherein the measuring comprises determining the first frequency of the oscillation signal in a recharging device external to the IMD.

4. The method of claim 1, wherein the measuring comprises determining the first frequency of the oscillation signal based on Fourier analysis.

5. The method of claim 1, wherein the measuring comprises determining a time interval between any peak, valley, or zero crossing of the oscillation signal.

6. The method of claim 1, further comprising:

driving the inductor with a sweep signal of changing frequency, wherein the range of the changing frequency is based on the measured first frequency of the oscillation signal; and

determining a third frequency of the sweep signal at a time of maximum power transfer between the inductor and the IMD.

7. The method of claim 6, wherein the sweep signal comprises a signal swept about the measured first frequency of the oscillation signal.

8. The method of claim 6, wherein the determining comprises:

measuring power transfer between the inductor and the IMD using a measurement circuit in the IMD; and

communicating an indication of the third frequency to a recharging device external to the IMD.

9. The method of claim 1, wherein the electrical pulse is periodic.

10. The method of claim 1, further comprising:

detecting an indication that a resonant frequency of a charging system has changed; and

adjusting the drive signal based on the detected indication.

11. The method of claim 10, wherein detecting the indication further comprises detecting motion of the inductor external to the IMD.

12. The method of claim 1, wherein the oscillating signal has a frequency between 8 and 13 kilohertz.

13. A system for charging a rechargeable power cell in an implantable medical device (IMD), comprising:

a recharging device external to the IMD, the recharging device comprising;

a primary coil configured to generate a magnetic field operative to induce flow of recharging current in the IMD;

a pulse generator configured to drive a pulse into the primary coil operative to induce an oscillation signal in the primary coil;

a signal generator configured to drive a drive signal across the primary coil at a first frequency based on a second frequency of the oscillation signal; and

a frequency measurement system configured to measure the second frequency of the oscillation signal.

14. The system of claim 13, wherein the frequency measurement system applies Fourier analysis to determine the second frequency of the oscillation signal.

15. The system of claim 13, wherein the frequency measurement system determines a time interval between any peak, valley, or zero crossing of the oscillation signal.

16. The system of claim 13, wherein the signal generator is configured to drive the primary coil with a sweep signal, and a start frequency and an end frequency of the sweep signal are based on the measured second frequency of the oscillation signal.

17. The system of claim 16, further comprising a power meter within one of the recharging device and the IMD, the power meter configured to measure power transferred from the primary coil to the IMD, and to determine a third frequency of the sweep signal at which maximum power transfer occurs.

18. The system of claim 17, wherein the IMD comprises:

a secondary coil, wherein the power meter is configured to measure power transferred through the secondary coil, and

a communication unit configured to communicate, to the recharging device, information indicative of the third frequency.

19. The system of claim 13, wherein the recharging device comprises a motion detector, and the pulse generator is configured to drive a pulse into the primary coil based on the motion detector detecting movement of the recharging device.

20. A charger for transcutaneously recharging an implanted power cell, comprising:

a primary coil configured to generate a magnetic field that induces flow of recharging current in a secondary coil of an implanted medical device (IMD);

a signal generator configured to;

drive a pulse into the primary coil operative to induce an oscillation signal in the primary coil;

drive a drive signal into the primary coil, a first frequency of the drive signal based on a second frequency of the oscillation signal; and

to

drive a sweep signal across the primary coil, a start frequency and an end frequency of the sweep signal based on the second frequency of the oscillation signal.

21. The charger of claim 20, wherein the signal generator is configured to intermittently drive the pulse.

22. The charger of claim 20, further comprising a frequency determination circuit configured to determine the second frequency of the oscillation signal.

23. The charger of claim 20, further comprising a communication unit configured to wirelessly communicate with the IMD, and to receive from the IMD information indicative of a third frequency of the sweep signal at which maximum power is transferred through the secondary coil.

24. The charger of claim 23, wherein the signal generator is configured to drive the drive signal at approximately the third frequency.

25. The charger of claim 20, further comprising a motion detection circuit configured to detect one of motion of the charger relative to the IMD and motion of the charger, and wherein the signal generator is configured to drive a pulse based on the detected motion of the charger.