System and method for monitoring a power source of an implantable medical device

• US 8,823,382 B2
• Filed: 04/30/2008
• Issued: 09/02/2014
• Est. Priority Date: 04/30/2008
• Status: Active Grant

• Current Assignee: Medtronic Incorporated (Medtronic Plc)
• Original Assignee: Medtronic Incorporated (Medtronic Plc)
• Inventors: Rondoni, John C., Jain, Mukul
• Primary Examiner(s): Tso, Edward H
• Assistant Examiner(s): PIGGUSH, AARON C
• Application Number:
  US12/112,144
• Publication Number:
  US 20090273349A1
• Time in Patent Office: 2,316 Days
• Field of Search: 324/426, 324/430, 320/134, 320/136, 320/157, 320/159, 320/162, 320/164
• US Class Current: 324/430
• CPC Class Codes: A61N 1/3708 for power depletion
• CPC Class Codes: G01R 31/3835 involving only voltage measurements
• CPC Class Codes: G01R 31/389 Measuring internal impedance, internal conductance or related variables

Abstract

Techniques for monitoring a battery of an implantable medical device are disclosed. First and second current sources are provided to draw currents having amplitudes of I₁ and I₂, respectively, from the battery. First and second voltage measurements, V₁ and V₂, are obtained when first and second combinations, respectively, of the first and second current sources are selectively activated. Battery impedance is determined using the current amplitudes I₁ and I₂ and the voltage measurements V₁ and V₂. The impedance measurement may be used to obtain an open-circuit voltage of the battery without the need to disconnect the battery from circuitry to which it provides power. Battery impedance and/or open-circuit battery voltage may then be used to determine an estimated time until an action is required involving the battery, which may include activation of an ERI or EOL indicator, or initiation of a recharge session.

Claims

1. A system for monitoring a battery of an implantable medical device, comprising:

a first current source associated with a current having a first predetermined amplitude;

a second current source associated with a current having a second predetermined amplitude;

a circuit adapted to be coupled to receive power from the battery, the circuit comprising at least one of a therapy module adapted to deliver therapy to a patient and sensing circuitry adapted to sense a signal from the patient; and

a control circuit adapted to activate the first current source and obtain a first voltage measurement across the battery while the first current source is activated, to activate the second current source and obtain a second voltage measurement across the battery while the second current source is activated, and to determine impedance of the battery from the first and the second predetermined amplitudes and the first and the second voltage measurements,

wherein the control circuit is adapted to obtain the first and second voltage measurements across the battery while the circuit that is adapted to be coupled to receive power is coupled to the battery.

2. The system of claim 1, wherein the control circuit is adapted to determine an open-circuit voltage of the battery from the battery impedance.

3. The system of claim 2, further including a storage device adapted to store data indicative of a characteristic of the battery, and wherein the control circuit is adapted to utilize at least one of the battery impedance and the open-circuit battery voltage to reference the data indicative of a characteristic of the battery to thereby determine a time until an action involving the battery is required.

4. The system of claim 1, further including a measurement circuit adapted to measure at least one of a quiescent current being supplied by the battery and a voltage across the battery while the quiescent current is being supplied by the battery, and wherein the control circuit is adapted to determine an open-circuit battery voltage from the battery impedance, the quiescent current, and the voltage across the battery while the quiescent current is being supplied by the battery.

5. The system of claim 1, further including a storage device adapted to store data indicative of characteristics of the battery, and wherein the control circuit is adapted to utilize the battery impedance and the data indicative of characteristics of the battery to determine capacity of the battery.

6. The system of claim 5, wherein the control circuit is adapted to utilized the capacity of the battery to determine at least one of an action that is to be taken regarding the battery and a time remaining until the action is to be taken.

7. The system of claim 6, wherein the action is selected from a group consisting of activating an ERI indicator, activating an EOL indicator, and scheduling a recharge session to recharge the battery.

8. The system of claim 1, further comprising a second control circuit communicatively coupled to the implantable medical device adapted to receive at least one of the first and the second predetermined amplitudes and the first and the second voltage measurements.

9. The system of claim 8, wherein at least one of the control circuit and the second control circuit is adapted to determine at least one of the battery impedance and an open-circuit voltage of the battery.

10. The system of claim 9, wherein the second control circuit is adapted to determine at least one of an action that is to be taken involving the battery and a time until the action is to be taken based on at least one of the battery impedance and the open-circuit voltage of the battery.

11. The system of claim 8, wherein a programmer comprises the second control circuit.

12. The system of claim 8, wherein a recharge unit comprises the second control circuit.

13. The system of claim 1, wherein the control circuit is adapted to determine the impedance of the battery as

(the first voltage measurement−

the second voltage measurement) / (the second predetermined amplitude−

the first predetermined amplitude).

14. The system of claim 1, wherein the control circuit is adapted to activate the first current source when the circuit that is adapted to be coupled to receive power from the battery is in a passive state.

15. The system of claim 14, wherein the control circuit is adapted to activate the second current source when the circuit that is adapted to be coupled to receive power from the battery is in a passive state.

16. A method of monitoring a battery supplying power to an implantable medical device, comprising:

supplying power, via the battery, to a circuit of the implantable medical device, the circuit comprising at least one of a therapy module adapted to deliver therapy to a patient and sensing circuitry adapted to sense a signal from the patient;

activating, via at least one control circuit, a first current source that sources or sinks a current of a first predetermined amplitude while power is supplied, via the battery, to the circuit;

obtaining, via the at least one control circuit, a first voltage measurement across the battery while the first current source is activated and while power is supplied, via the battery, to the circuit;

activating, via the at least one control circuit, a second current source that sources or sinks a current of a second predetermined amplitude while power is supplied, via the battery, to the circuit;

obtaining, via the at least one control circuit, a second voltage measurement across the battery while the second current source is activated and while power is supplied, via the battery, to the circuit; and

determining, via the at least one control circuit, impedance of the battery from the first predetermined amplitude, the second predetermined amplitude, the first voltage measurement, and the second voltage measurement.

17. The method of claim 16, wherein determining impedance of the battery is performed by the at least one control circuit in the implantable medical device.

18. The method of claim 16, wherein determining impedance of the battery is performed by the at least one control circuit in a device external to the implantable medical device.

19. The method of claim 16, wherein the impedance of the battery is determined as

(the first voltage measurement−

the second voltage measurement) / (the second predetermined amplitude−

the first predetermined amplitude).

20. The method of claim 16, further including utilizing data describing characteristics of the battery to determine, based on the battery impedance, at least one of an action to be taken regarding the battery and a time until the action is to be taken.

21. The method of claim 16, and further including providing status to a user via a user interface device, the status being determined, at least in part, based on the battery impedance, the status being indicative of at least one of an action to be taken regarding the battery, a time until the action is to be taken, a capacity associated with the battery, an open-circuit voltage of the battery, or the battery impedance.

22. The method of claim 16, further including determining an open-circuit voltage of the battery from the impedance of the battery.

23. The method of claim 22, further including utilizing data describing characteristics of the battery to determine, based on at least one of the battery impedance and the open-circuit voltage, at least one of an action to be taken regarding the battery, a time until the action is to be taken and a capacity associated with the battery.

24. The method of claim 16, further including:

measuring a quiescent current being provided by the battery while the implantable medical device is in the quiescent state;

measuring a voltage across the battery while the battery is providing the quiescent current; and

determining, an open-circuit voltage of the battery based on the quiescent current, the battery impedance, and the voltage across the battery while the battery is providing the quiescent current.

25. The method of claim 24, further including placing the implantable medical device in the quiescent state.

26. The method of claim 16, wherein activating, via at least one control circuit, a first current source that sources or sinks a current of a first predetermined amplitude comprises activating, via the at least one control circuit, the first current source at a time when the circuit comprising at least one of a therapy module adapted to deliver therapy to a patient and sensing circuitry adapted to sense a signal from the patient is in a passive state.

27. A system for monitoring a battery of an implantable medical device, comprising:

a circuit adapted to be coupled to receive power from the battery, the circuit comprising at least one of a therapy module adapted to deliver therapy to a patient and sensing circuitry adapted to sense a signal from the patient;

a first current source adapted to cause a current of a first predetermined amplitude to be drawn from the battery while the circuit is coupled to receive power from the battery;

a second current source adapted to cause a current of a second predetermined amplitude to be drawn from the battery while the circuit is coupled to receive power from the battery; and

a measurement circuit adapted to measure a first voltage across the battery when a first combination of the first and second current sources is activated while the circuit is coupled to receive power from the battery and to measure a second voltage across the battery when a different combination of the first and the second current sources is activated while the circuit is coupled to receive power from the battery, whereby impedance of the battery is determined from the first predetermined amplitude, the second predetermined amplitude, the first voltage, and the second voltage.

28. The system of claim 27, further comprising a control circuit adapted to determine the battery impedance from the first predetermined amplitude, the second predetermined amplitude, the first voltage, and the second voltage.

29. The system of claim 28, further including an external device adapted to be electromagnetically coupled to the implantable medical device, and wherein the external device comprises the control circuit.

30. The system of claim 28, further comprising an implantable medical device that comprises the control circuit.

31. The system of claim 27, further comprising a storage device adapted to store executable instructions to cause selective activation of at least one of the first current source, the second current source, and the measurement circuit.

32. The system of claim 27, wherein the measurement circuit is adapted to measure a quiescent current that is drawn from the battery when the therapy module is not delivering therapy and both the first current source and the second current source are deactivated.

33. The system of claim 28, wherein the measurement circuit is adapted to measure a quiescent current that is drawn from the battery when the therapy module is not delivering therapy and when both the first current source and the second current source are deactivated, and wherein the control circuit is adapted to determine an open-circuit voltage of the battery from the quiescent current and the battery impedance.

34. The system of claim 28, wherein the control circuit is adapted to determine the battery impedance as

(the first voltage measurement−

the second voltage measurement) / (the second predetermined amplitude−

the first predetermined amplitude).

35. The system of claim 27, further comprising a control circuit adapted to determine, based on the battery impedance, at least one of battery capacity, an action to be performed in association with the battery, and a time until the action is to be performed.

36. The system of claim 27, wherein the measurement circuit is adapted to measure the first voltage across the battery while the circuit is in a passive state and to measure the second voltage across the battery while the circuit is in a passive state.

37. A system for monitoring a battery of an implantable medical device, comprising:

means for receiving power from the battery comprising at least one of therapy means for delivering therapy to a patient and sensing means for sensing a signal from the patient;

first current source means for causing a battery to provide a current of a first predetermined amplitude while the means for receiving receives power from the battery;

second current source means for causing a battery to provide a current of a second predetermined amplitude while the means for receiving receives power from the battery;

measurement means for obtaining a first voltage measurement across the battery when a first combination comprising at least one of the first current source means and the second current source means are selectively activated while the means for receiving receives power from the battery, and for obtaining a second voltage measurement across the battery when a second combination comprising at least one of the first current source means and the second current source means that is different from the first combination is selectively activated while the means for receiving receives power from the battery; and

control means for determining impedance of the battery based on the first predetermined amplitude, the second predetermined amplitude, the first voltage measurement, and the second voltage measurement.

39. The system of claim 37, wherein the measurement means comprises means for obtaining the first voltage measurement across the battery while the means for receiving is in a passive state.

38. A method of monitoring a battery supplying power to an implantable medical device, comprising:

coupling a battery to a circuit of the implantable medical device, the circuit comprising at least one of a therapy module adapted to deliver therapy to a patient and sensing circuitry adapted to sense a signal from the patient;

generating a first current having a first predetermined amplitude while the battery is coupled to the circuit;

obtaining a first voltage measurement across the battery while the first current is being generated and while the battery is coupled to the circuit;

generating a second current having a second predetermined amplitude while the battery is coupled to the circuit;

obtaining a second voltage measurement across the battery while the second current source is activated and while the battery is coupled to the circuit; and

determining, via a control circuit, impedance of the battery from the first predetermined amplitude, the second predetermined amplitude, the first voltage measurement, and the second voltage measurement.

40. The method of claim 38, wherein generating a first current comprises generating a first current while the circuit comprising at least one of a therapy module and sensing circuitry is in a passive state and wherein generating a second current comprises generating a second current while the circuit comprising at least one of a therapy module and sensing circuitry is in a passive state.