Method for monitoring end of life for battery

• US 7,580,749 B2
• Filed: 07/18/2007
• Issued: 08/25/2009
• Est. Priority Date: 09/15/1997
• Status: Expired due to Fees

• Current Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Original Assignee: Cardiac Pacemakers Incorporated (Boston Scientific Corporation)
• Inventors: Lyden, Michael J.
• Primary Examiner(s): Sykes; Angela D
• Assistant Examiner(s): Stoklosa; Joseph
• Application Number:
  US11/779,779
• Publication Number:
  US 20070265672A1
• Time in Patent Office: 769 Days
• Field of Search: 607/9, 607/27, 607/29
• US Class Current: 607/29
• CPC Class Codes: A61N 1/3708 for power depletion
• CPC Class Codes: A61N 1/378 Electrical supply
• CPC Class Codes: G01R 31/3647 for determining the ability of a battery to perform a critical function, e.g. cranking
• CPC Class Codes: G01R 31/367 Software therefor, e.g. for battery testing using modelling or look-up tables
• CPC Class Codes: H02J 2310/23 The load being a medical device, a medical implant, or a life supporting device
• CPC Class Codes: H02J 7/0048 Detection of remaining charge capacity or state of charge [SOC]
• CPC Class Codes: H02J 7/005 Detection of state of health [SOH]

Abstract

A system is described. The system includes a lithium battery, a charge storage capacitor electrically connected to the lithium battery, a first device, and at least one second device. The first device is electrically connected to the lithium battery and is powered by the lithium battery. The at least one second device is attached to the charge storage capacitor and adapted to read a rate of charge storage in the charge storage capacitor or to calculate the rate of charge storage by measuring both a time of charging and a charge stored or added to the charge storage capacitor during the time of charging.

Claims

1. A system, including:

a battery power terminal for a battery;

sensing and pacing control circuitry electrically connected to the battery power terminal;

a pacing supply storage (PSS) capacitor electrically connected to the battery power terminal and to a discharge switch;

comparison circuitry, including;

a first comparator electrically connected to the battery power terminal and adapted for comparing a battery terminal voltage (Vbatt) to a brownout voltage (Vstop), the first comparator having a first comparator output;

a second comparator electrically connected to the PSS capacitor and adapted for comparing a pacing supply storage voltage (Vcs) to at least one reference voltage (Vx), the second comparator having a second comparator output, wherein the first comparator output and the second comparator output are adapted to control current flow from the battery power terminal to the PSS capacitor; and

charge time measurement (CTM) control circuitry electrically connected to the sensing and pacing control circuitry, the comparator circuitry and the discharge switch, the charge time measurement control circuitry being adapted to;

access a predetermined set of charge time measurement set-up parameters and a predetermined elective replacement time (ERT) charge time limit determined from a battery resistance ERT target that corresponds to a charge depletion target;

determine a rate of charge storage in the PSS capacitor using the predetermined set of charge time measurement set-up parameters;

compare the determined rate of charge storage in the PSS capacitor to the predetermined ERT charge time limit for the predetermined set of charge time measurement set-up parameters; and

declare an ERT based on a number of comparisons between the determined rate of charge storage in the charge storage capacitor and the ERT charge time limit.

2. The system of claim 1, further comprising a switched capacitor power supply operably connected to the battery power terminal and the PSS capacitor for charging the PSS capacitor, wherein an output of the comparison circuit is electrically connected to the switched capacitor power supply to control current flow from the battery power terminal to the pacing supply storage capacitor.

3. The system of claim 2, wherein the predetermined set of charge time measurement set-up parameters include:

a physician-programmed final voltage (VF) to end a time measurement for determining the rate of charge storage in the PSS capacitor; and

an initial reference voltage (VI) to begin the time measurement for determining the rate of charge storage in the PSS capacitor.

4. The system of claim 3, wherein a pacing supply storage voltage (Vcs) increases approximately linearly from VI to VF during the time measurement for determining the rate of charge storage in the PSS capacitor.

5. The system of claim 3, wherein:

the CTM control circuitry includes a multiplexer for selecting one of VF and VI to be compared to a PSS capacitor voltage level (Vsc) within the control circuitry for controlling current flow from the battery power terminal to the PSS capacitor; and

the CTM control circuitry selects VI to be compared to Vsc to begin a time charge measurement count and VF to be compared to Vsc to end the time charge measurement count.

6. The system of claim 3, wherein the CTM control circuitry includes a time charge counter for measuring a time in which a relatively constant current charges the PSS capacitor from VI to VF.

7. The system of claim 3, wherein the sensing and pacing control circuitry includes a sensing and pacing control block adapted for selecting a voltage level (Vd) to which the PSS capacitor is discharged prior to beginning the time measurement for determining the rate of charge storage in the PSS capacitor, wherein Vd is less than VI.

8. The system of claim 7, wherein the CTM control circuitry includes a multiplexer for selecting one of the VF, VI and Vd to be compared to a PSS capacitor voltage level (Vsc) within the control circuitry for controlling current flow from the battery power terminal to the PSS capacitor.

9. The system of claim 8, wherein the CTM control circuitry selects:

VF to be compared to Vsc to synchronize the beginning of the time measurement to the completion of a cardiac depolarization;

Vd to be compared to Vsc to limit the discharge of the PSS capacitor and open a PSS capacitor discharge switch;

VI to be compared to Vsc to begin a time charge measurement count after a bypass capacitor (Cb) is discharged and a battery terminal voltage (Vbatt) is driven to a brownout voltage (Vstop) limit; and

VF to be compared to Vsc to end the time charge measurement count.

24. The system of claim 1, wherein the system includes a pacemaker, and the pacemaker includes the sensing and pacing control circuitry, the PSS capacitor, the first comparator, the second comparator, and the CTM control circuitry.

10. A system, comprising:

a pacing storage capacitor;

a battery power terminal for a battery, the terminal being electrically connected to the pacing storage capacitor to charge the pacing storage capacitor;

a discharge switch electrically connected to the pacing storage capacitor; and

control circuitry electrically connected to the discharge switch to selectively discharge the storage capacitor and electrically connected to the pacing storage capacitor to detect a voltage across the pacing storage capacitor, the control circuitry to perform a time measurement for determining a rate of charge storage in the pacing storage capacitor, wherein the control circuitry is adapted to;

discharge the pacing storage capacitor to a predetermined voltage level (Vd) prior to beginning the time measurement;

detect when the voltage across the pacing storage capacitor reaches a predetermined initial voltage level (VI) to begin the time measurement, wherein VI is larger than Vd; and

detect when the voltage across the pacing storage capacitor reaches a predetermined final voltage (VF) to end the time measurement.

11. The system of claim 10, wherein the system is incorporated in a pacemaker.

12. The system of claim 10, wherein the control circuitry is further adapted to access a predetermined elective replacement time (ERT) charge time limit, and to declare an ERT based on a number of comparisons between the rate of charge storage in the pacing storage capacitor and the ERT charge time limit.

13. The system of claim 10, further comprising circuitry to control current flow from the battery power terminal to charge the pacing storage capacitor.

14. The system of claim 13, wherein the circuitry to control current flow includes a switched capacitor power supply and comparison circuitry, the comparison circuitry includes:

a first comparator electrically connected to the battery power terminal and adapted for comparing a battery terminal voltage (Vbatt) to a brownout voltage (Vstop), the first comparator having a first comparator output; and

a second comparator electrically connected to the pacing storage capacitor and adapted for comparing a pacing supply storage voltage (Vcs) to at least one reference voltage (Vx), the second comparator having a second comparator output,

wherein the first comparator output and the second comparator output are used to control to control the switched capacitor power supply to control current flow from the battery power terminal to the pacing storage capacitor.

15. The system of claim 10, further comprising a number of registers to hold a Vd value, a VI value, and a VF value, and a multiplexer for selecting one of VF, VI and Vd to be compared to the voltage across the pacing storage capacitor.

16. The system of claim 10, wherein the rate of charge storage is determined when the voltage across the pacing storage capacitor increases linearly from VI to VF.

17. A system, including:

a battery power terminal for a battery;

a pacing supply storage (PSS) capacitor electrically connected to the battery power terminal; and

control circuitry adapted to;

deliver pacing pulses using charged stored on the PSS capacitor;

measure a rate of charge of the PSS capacitor from a first predetermined voltage to a second predetermined voltage at times synchronized to occur between delivered pacing pulses; and

compare the measured rate of charge of the PSS capacitor to a predetermined elective replacement time (ERT) charge time limit determined from a battery resistance ERT target; and

declare an elective replacement time (ERT) for the battery based on the comparison between the measured rate of charge of the PSS capacitor and the predetermined ERT charge time limit.

18. The system of claim 17, wherein:

the first predetermined voltage is an initial reference voltage (VI) to begin the time measurement for determining the rate of charge storage in the PSS capacitor;

the second predetermined voltage is a physician-programmed final voltage (VF) to end a time measurement for determining the rate of charge storage in the PSS capacitor; and

the control circuitry includes a time charge counter for measuring a time in which a relatively constant current charges the PSS capacitor from VI to VF.

19. The system of claim 18, wherein the control circuitry is adapted to discharge the PSS capacitor after a delivered pacing pulse to a discharge voltage (Vd) that is less than VI, and then charge the PSS capacitor to VI, and then charge the PSS capacitor to VF.

20. The system of claim 17, wherein the control circuitry is adapted to measure a rate of voltage change as a function of time to measure the rate of charge of the PSS capacitor.

21. The system of claim 17, wherein:

the system includes an implanted device and a programmer, and the implanted device includes the PSS capacitor and the control circuitry;

the implanted device and the programmer are adapted to communicate to each other; and

the programmer is adapted to receive the measured rate of charge of the PSS capacitor from the implanted device, estimate an ERT value for the battery, and display the ERT value.

22. The system of claim 21, wherein the ERT value includes a value indicative of a charge remaining for the battery.

23. The system of claim 21, wherein the ERT value includes a value indicative of an operation time remaining for the battery.

25. The system of claim 17, wherein the system includes a pacemaker, and the pacemaker includes the PSS capacitor and the control circuitry.