Battery monitoring circuit in a cardiac pacemaker

• US 4,290,429 A
• Filed: 03/31/1980
• Issued: 09/22/1981
• Est. Priority Date: 03/31/1979
• Status: Expired due to Term

• Current Assignee: Biotronik Mess-Und Therapiegeraete GmbH & Company Ingenieurbuero Berlin (Biotronik SE & Company KG)
• Original Assignee: Biotronik Mess-Und Therapiegeraete GmbH & Company Ingenieurbuero Berlin (Biotronik SE & Company KG)
• Inventors: Blaser, Reinhard
• Primary Examiner(s): Kamm, William E.
• Application Number:
  US06/136,094
• Time in Patent Office: 540 Days
• Field of Search: 128/419 PG, 128/419 PS, 128/419 PT
• 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 19/16542 for batteries charge condition monitoring in G01R31/36
• CPC Class Codes: G01R 31/3648 comprising digital calculation means, e.g. for performing an algorithm

Abstract

In a monitoring circuit for monitoring the state of the battery of a card pacemaker, which pacemaker includes an energy storage element normally connected to be charged by the battery and to constitute an energy source for the pacemaker components, the circuit including a voltage detector connected to emit a signal when a parameter representative of the battery state passes a threshold value, the circuit further includes: first switching member for disconnecting the battery from the energy storage element during periodically recurring time periods of given duration; a fixed load having an impedance which is large compared to the internal resistance of the battery and connected to apply to the voltage detector a voltage representative of the current flowing through the fixed load; an element for connecting the load across the battery during each time period for causing the load to be supplied with a current having a value at least indirectly defining the parameter representative of the battery state; and a storage member connected to provide an indication of the emission of such signal by the voltage detector.

Claims

1. In a monitoring circuit for monitoring the state of the battery of a cardiac pacemaker, which pacemaker includes an energy storage element normally connected to be charged by the battery and to constitute an energy source for the pacemaker components, the circuit including a voltage detector connected to emit a signal when a parameter representative of the battery state passes a threshold value, the improvement comprising:

first switching means for disconnecting the battery from the energy storage element during periodically recurring time periods of given duration;

means defining a fixed load having an impedance which is large compared to the internal resistance of the battery and connected to apply to said voltage detector a voltage representative of the current flowing through said fixed load;

means for connecting said load across the battery during each said time period for causing said load to be supplied with a current having a value at least indirectly defining the parameter representative of the battery state; and

storage means connected to provide an indication of the emission of such signal by said voltage detector.

2. An arrangement as defined in claim 1 wherein the impedance of said fixed load has a value selected for causing the value of the current therethrough during each said time period to be less than that corresponding to the parameter threshold value when the battery reaches a state at which at least one of the following conditions exists:

its open-circuit voltage is less than a minimum acceptable value for an internal resistance value equal to that of a fresh battery; and

its internal resistance is greater than a maximum acceptable value for an open-circuit voltage value equal to that of a fresh battery.

3. An arrangement as defined in claim 1 wherein said fixed load comprises a capacitor and said means for connecting said load comprise second switch means connected for causing said capacitor to be charged by the current through said fixed load during a fixed time interval within each said time period and to apply a voltage proportional to its charge to said voltage detector.

4. An arrangement as defined in claim 3 wherein said storage means comprise a flipflop connected to be set at the beginning of each said time period and to be reset when said voltage detector emits a signal during said time period.

5. An arrangement as defined in claim 3 or 4 wherein each said fixed time interval coincides with a respective said time period.

6. An arrangement as defined in claim 1 wherein each said time period is controlled by a respective stimulation pulse produced by the pacemaker.

7. An arrangement as defined in claim 6 wherein the pacemaker includes a clock pulse generator for actuating stimulation pulses and said circuit is connected to have said time periods initiated by clock pulses from the clock pulse generator.