Battery Management Circuitry for Implantable Medical Devices

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Solution Overview

Problem

Implantable medical devices, such as spinal cord stimulators, face challenges in effectively managing battery life and preventing overcharging or undervoltage conditions, which can lead to battery damage or premature depletion.

Innovation Solution

The implementation of improved battery management circuitry that includes charging circuitry, load isolation circuitry, and overvoltage/undervoltage protection mechanisms, along with a current/voltage source and firmware control, to regulate charging and power distribution, ensuring safe operation and extending battery life.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the battery is continuously charged to maintain device operation, then the device can function reliably, but the battery may become overcharged and damaged

Engineering Contradiction:

Improvedevice operation reliabilityVSAvoidovercharging damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The charging circuitry is configured to automatically stop charging the battery when it reaches a predetermined voltage threshold (e.g., 4.2V per cell), preventing overcharging before it can cause damage. This preliminary protective action ensures the battery is protected in advance rather than reacting after damage occurs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors battery voltage through the battery management circuitry and provides feedback control to the charging process. When the voltage reaches the threshold, the feedback mechanism automatically terminates charging, creating a closed-loop system that prevents overcharging while maintaining reliable operation.

Inventive Principle:

Principle #23Feedback

2Duration of action of moving object

If the battery is allowed to discharge completely to maximize usage, then device runtime is extended, but the battery may suffer from undervoltage conditions and premature depletion

Engineering Contradiction:

Improvedevice runtimeVSAvoidundervoltage damage

Core Design Contradiction:

Duration of action of moving objectVSObject-affected harmful factors

Solution Approach 1:

The battery management circuitry is configured to terminate discharge at a predetermined voltage threshold (e.g., 3.0V per cell) before the battery reaches complete depletion. This preliminary protective action prevents undervoltage conditions that could cause permanent battery damage, extending the battery's overall lifespan.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors battery voltage and provides feedback control to prevent discharge below the safe threshold. This closed-loop monitoring ensures the battery is protected from undervoltage damage while maximizing usable runtime through optimal discharge management.

Inventive Principle:

Principle #23Feedback

3Object-affected harmful factors

If complex battery management circuitry is added to prevent overcharging and undervoltage conditions, then battery safety is improved, but the device complexity increases

Engineering Contradiction:

Improvebattery safetyVSAvoidcircuitry complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The battery management functionality (overcharge protection, undervoltage protection, charging control) is integrated into a single unified circuit module that works together with the existing charging circuitry. This merging approach provides comprehensive safety features without proportionally increasing overall device complexity, as the protection functions share common components and control pathways.

Inventive Principle:

Principle #5Merging (Combining)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution effectively prevents overcharging and undervoltage conditions, ensuring the battery's longevity and maintaining reliable device operation by dynamically managing charging and power distribution, thereby enhancing the overall performance and safety of implantable medical devices.

Implementation Method 1

charging circuitry for generating a controlled current for charging the battery

Methodology Applied

Scientific EffectElectrical charge transfer: Battery (electricity)

Implementation Method 2

load isolation circuitry which can controllably connect or disconnect the battery from the load

Methodology Applied

Scientific EffectElectrical connection control: Electrical Resistance

Data Source

PatentEP3081259B1Battery management for an implantable medical device

Publication Date: 2019.02.06 BOSTON SCI NEUROMODULATION CORP

Figure 1A~1B
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Figure 3

AI summary

Battery management circuitry for an implantable medical device such as an implantable neurostimulator is described. The circuitry has a T-shape with respect to the battery terminal, with charging circuitry coupled between rectifier circuitry and the battery terminal on one side of the T, and load isolation circuitry coupled between the load and the battery terminal on the other side. The load isolation circuitry can comprise two switches wired in parallel. An undervoltage fault condition opens both switches to isolate the battery terminal from the load to prevent further dissipation of the battery. Other fault conditions will open only one the switches leaving the other closed to allow for reduced power to the load to continue implant operations albeit at safer low-power levels. The battery management circuitry can be fixed in a particular location on an integrated circuit which also includes for example the stimulation circuitry for the electrodes.