Efficient External Charger for an Implantable Medical Device Optimized for Fast Charging and Constrained by an Implant Power Dissipation Limit

• US 20110087307A1
• Filed: 10/08/2009
• Published: 04/14/2011
• Est. Priority Date: 10/08/2009
• Status: Active Grant

• Current Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Original Assignee: Boston Scientific Neuromodulation Corporation (Boston Scientific Corporation)
• Inventors: Carbunaru, Rafael, Chen, Joey, Parramon, Jordi, Rahman, Md. Mizanur, Shi, Jess, Ozawa, Robert
• Granted Patent: US 8,744,592 B2
• Time in Patent Office: Days
• US Class Current: 607/61
• CPC Class Codes: A61N 1/3605 Implantable neurostimulators for stimulating central or peripheral nerve system
• CPC Class Codes: A61N 1/37205 Microstimulators, e.g. implantable through a cannula
• CPC Class Codes: A61N 1/37217 characterised by the communication link, e.g. acoustic or tactile
• CPC Class Codes: A61N 1/3787 from an external energy source

Abstract

An improved external charger for a battery in an implantable medical device (implant), and technique for charging the battery using such improved external charger, is disclosed. In one example, simulation data is used to model the power dissipation of the charging circuitry in the implant at varying levels of implant power. A power dissipation limit is chosen to constrain the charging circuitry from producing an inordinate amount of heat to the tissue surrounding the implant, and duty cycles are determined for the various levels of input intensities to ensure that the power limit is not exceeded. A maximum simulated average battery current determines the optimal (i.e., quickest) battery charging current, and at least an optimal value for a parameter indicative of that current, for example, the voltage across the battery charging circuitry, is determined and stored in the external charger. During charging, the actual value for that parameter is reported from the implant to the external charger, which in turn adjusts the intensity and/or duty cycle of the magnetic charging field consistent with the simulation to ensure that charging is as fast as possible, while still not exceeding the power dissipation limit.

Claims

1. A method for charging a battery in an implantable medical device, comprising:

generating a magnetic charging field using an external charger, the magnetic charging field for producing a battery charging current in the implantable medical device during a charging session;

periodically measuring during the charging session a parameter in the implantable medical device;

periodically telemetering during the charging session the parameter to the external charger; and

periodically adjusting during the charging session the magnetic charging field in accordance with the parameter to maximize the produced battery charging current while not exceeding a maximum power dissipation limit for the implantable medical device.

2. The method of claim 1, wherein the parameter is indicative of the produced battery charging current.

3. The method of claim 1, wherein adjusting the magnetic charging field comprises adjusting its intensity or duty cycle.

4. The method of claim 1, wherein the parameter comprises a voltage across circuitry in line with the battery charging current.

5. The method of claim 4, wherein the circuitry comprises charging circuitry serially coupled to the battery in the implantable medical device.

6. A method for charging a battery in an implantable medical device, comprising:

generating a magnetic charging field using an external charger, the magnetic charging field for producing a battery charging current in the implantable medical device;

measuring a parameter in the implantable medical device indicative of the produced battery charging current;

telemetering the parameter to the external charger;

comparing a value of the telemetered parameter to an optimal value at the external charger, wherein the optimal value indicates a maximum average battery current; and

adjusting the magnetic charging field in accordance with the comparison in a manner not to exceed a power dissipation limit for the implantable medical device.

7. The method of claim 6, wherein adjusting the magnetic charging field comprises adjusting its duty cycle, its intensity, or both.

8. The method of claim 6, wherein adjusting the magnetic charging field comprises adjusting an intensity of the magnetic charging field to bring the value of the telemetered parameter toward the optimal value.

9. The method of claim 6, wherein the optimal value comprises a range of values for the parameter.

10. The method of claim 6, further comprising telemetering a voltage of the battery to the external charger, and wherein adjusting the magnetic charging field additionally occurs in accordance with the telemetered battery voltage.

11. A method for charging a battery in an implantable medical device, comprising:

generating a magnetic charging field using an external charger, the magnetic charging field for producing a battery charging current in the implantable medical device;

measuring a parameter in the implantable medical device indicative of the produced battery charging current;

telemetering the parameter to the external charger;

consulting data stored in the external charger which relates values of the parameter to a duty cycle for the external charger;

determining a duty cycle from the data for a value of the telemetered parameter; and

duty cycling the magnetic charging field in accordance with the determined duty cycle.

12. The method of claim 11, wherein the duty cycle is determined to ensure that the implantable medical device does not exceed a power dissipation limit.

13. The method of claim 11, wherein the parameter comprise a voltage across charging circuitry in line with the battery.

14. The method of claim 11, wherein an intensity of the magnetic charging field is also varied in accordance with the telemetered parameter.

15. The method of claim 11, wherein the parameter is telemetered to the external charger by Load Shift Keying in the implantable medical device.

16. A method for charging a battery in an implantable medical device, comprising:

generating a magnetic charging field using an external charger, the magnetic charging field for producing a battery charging current in the implantable medical device;

measuring a parameter in the implantable medical device;

telemetering the parameter to the external charger; and

adjusting an intensity and duty cycle of the magnetic charging field in response to the telemetered parameter,

wherein the adjustment ensures a power dissipation limit for the implantable medical device is not exceeded.

17. The method of claim 16, wherein the parameter is telemetered to the external charger during an off cycle in the duty cycle of the magnetic charging field.

18. The method of claim 16, wherein the method repeats itself to iteratively adjust the intensity and duty cycle of the magnetic charging field.

19. The method of claim 16, wherein the parameter is indicative of heating in the implantable medical device during charging.

21. The method of claim 2016, wherein the adjustment additionally ensures that the produced battery charging current is maximized for the power dissipation limit.

20. (canceled)

22. An external charger designed to ensure compliance with a power dissipation limit for an implantable medical device during charging of a battery in the implantable medical device, comprising:

a memory in which is stored;

a first relationship between values for (i) a parameter measureable in the implant, and (ii) a duty cycle for the external charger, wherein the duty cycles ensure that the power dissipation limit is not exceeded; and

a first optimal value for the parameter in the external charger, wherein the first optimal value is indicative of a maximum battery charging current.

23. The external charger of claim 22, further comprising a transmitter for broadcasting a magnetic charging field to the implantable medical device, and a receiver for receiving the parameter from the implantable medical device.

24. The external charger of claim 23, further comprising a microcontroller in communication with the memory, the transmitter, and the receiver.

25. The external charger of claim 22, wherein the transmitter implements controls of a duty cycle and intensity of the magnetic charging field.

26. The external charger of claim 22, further comprising another data structure for a second battery voltage different from the first battery voltage.

27. The external charger of claim 22, wherein the memory further stores:

a second relationship between values for (i) the parameter measureable in the implant, and (ii) a duty cycle for the external charger, wherein the duty cycles ensure that the power dissipation limit is not exceeded; and

a second optimal value for the parameter in the external charger, wherein the second optimal value is indicative of a maximum battery charging current.

28. The external charger of claim 27, wherein the first relationship and first optimal value correspond to a first battery voltage, and wherein the second relationship and second optimal value correspond to a second battery voltage.

29. A method for programming an external charger to ensure compliance with a power dissipation limit for an implantable medical device during charging, comprising:

determining an external charger duty cycle and an average battery charging current for a plurality of external charger intensities, wherein the duty cycles are determined such that the implantable medical device does not exceed the power dissipation limit;

determining a parameter measureable in the implantable medical device which is indicative of the average battery charging current;

determining a maximum average battery current and a corresponding optimal value for the parameter;

storing a relationship between the parameter and the duty cycles in the external charger; and

storing the optimal value for the parameter in the external charger.

30. The method of claim 29, wherein the determined values are determined by a computer simulation.

31. The method of claim 29, wherein the parameter is indicative of the battery charging current.

32. The method of claim 29, wherein the parameter is indicative of heat generation in the implantable medical device.