Efficient external charger for an implantable medical device optimized for fast charging and constrained by an implant power dissipation limit

• US 8,744,592 B2
• Filed: 10/08/2009
• Issued: 06/03/2014
• 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, Parramon, Jordi, Ozawa, Robert, Shi, Jess, Chen, Joey, Rahman, Md. Mizanur
• Primary Examiner(s): Koharski, Christopher
• Assistant Examiner(s): VOORHEES, CATHERINE M
• Application Number:
  US12/575,733
• Publication Number:
  US 20110087307A1
• Time in Patent Office: 1,699 Days
• Field of Search: 607 32- 33, 607 60- 61, 320/108
• 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 in accordance with the parameter;

(1) an intensity of the magnetic charging field to maximize an average battery charging current, and (2) a duty cycle of the magnetic charging field in accordance with 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 the parameter comprises a voltage across charging circuitry serially coupled to the battery in the implantable medical device, wherein the battery charging current passes through the charging circuitry.

4. The method of claim 1, wherein adjusting the intensity comprises comparing the parameter to an optimal value in the external charger.

5. The method of claim 4, wherein the intensity is adjusted to bring the parameter to the optimal value.

6. The method of claim 1, wherein the external charger comprises a memory, wherein the memory comprises possible values for the parameter and a duty cycle associated with each value, wherein each duty cycle in the memory is determined in accordance with the maximum power dissipation limit for the implantable medical device.

7. The method of claim 6, wherein adjusting the duty cycle comprises retrieving a duty cycle from the memory using the parameter.

8. The method of claim 7, wherein the memory further comprises an optimal value for the parameter.

9. The method of claim 8, wherein the intensity is adjusted to bring the parameter to the optimal value.

10. The method of claim 1, wherein the parameter is telemetered to the external charger during off periods of the duty cycle.

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;

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 adjusting the intensity comprises comparing the telemetered parameter to an optimal parameter stored in the external charger, and wherein adjusting the duty cycle comprises selecting a duty cycle stored in the external charger using the telemetered parameter.

12. The method of claim 11, wherein the parameter is telemetered to the external charger during an off cycle in the duty cycle of the magnetic charging field.

13. The method of claim 11, wherein the method repeats itself to iteratively adjust the intensity and duty cycle of the magnetic charging field.

14. The method of claim 11, wherein the parameter is indicative of heating in the implantable medical device during charging.

15. The method of claim 11, wherein adjusting the intensity and duty cycle additionally ensures that an average battery charging current is maximized without exceeding a power dissipation limit for the implantable medical device.

16. The method of claim 11, wherein the intensity is adjusted to bring the parameter to the optimal value.