Capacitor Health Detection in Implantable Stimulators

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Solution Overview

Problem

Medical devices with capacitors used for stimulation, such as cochlear implants and cardiac stimulators, face challenges in detecting faulty capacitors before they fail to block DC flow, which can lead to tissue damage and is difficult to identify during normal operation.

Innovation Solution

A method and apparatus for testing the health of capacitors by selecting active and return electrodes, charging them, disconnecting from other nodes, and measuring discharge characteristics to determine if capacitors are functioning properly, with remediation actions such as disabling faulty electrodes and alerting clinicians.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If capacitors are continuously monitored during normal operation, then reliability is improved, but device complexity increases

Engineering Contradiction:

Improvecapacitor health detectionVSAvoidmonitoring system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent performs capacitor health assessment during manufacturing before implantation, establishing baseline characteristics. This preliminary action allows the system to detect deviations from normal behavior during operation without requiring complex real-time monitoring hardware, thereby improving reliability while minimizing added complexity

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The capacitor's own charging and discharging cycles are utilized for self-diagnosis. By measuring voltage decay during natural discharge phases and comparing it to expected characteristics, the system enables capacitors to effectively monitor their own health without requiring separate dedicated monitoring components

Inventive Principle:

Principle #25Self-service

2Reliability

If capacitor testing is performed during normal operation, then reliability is improved, but loss of time occurs due to interruptions

Engineering Contradiction:

Improvefaulty capacitor detectionVSAvoidoperation interruption time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Capacitor health testing is performed periodically during scheduled maintenance intervals or at predetermined time points rather than continuously. This periodic approach allows the device to maintain normal operation between tests while still detecting capacitor degradation trends over time, minimizing operational interruptions

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The testing methodology is designed to work during the capacitor's natural discharge phases in the stimulation cycle. By utilizing existing operational phases for measurement, the system maintains continuous useful stimulation action while incorporating health assessment without requiring separate dedicated test periods

Inventive Principle:

Principle #20Continuity of useful action

3Object-affected harmful factors

If early detection of faulty capacitors is implemented, then harmful factors are reduced, but device complexity increases

Engineering Contradiction:

Improvetissue damage from DC flowVSAvoidtesting apparatus complexity

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The patent extracts the health assessment function from complex real-time monitoring and performs it during specific disconnected test phases. By separating the diagnostic function from continuous operation and concentrating it in dedicated test windows, the system reduces tissue exposure risks while keeping the overall device architecture relatively simple

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

A microcontroller or processing unit serves as an intermediary that coordinates the disconnect-test-reconnect sequence and analyzes measurement data. This intermediary manages the complexity of early detection logic without requiring complex hardware modifications to the capacitor or electrode structures themselves

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Enables early detection and remediation of faulty capacitors, preventing potential tissue damage and ensuring continued proper operation of implantable medical devices.

Implementation Method 1

Each respective electrode subcircuit includes a capacitor an electrode connected in series to the capacitor and being configured to deliver stimulation to tissue using the stimulation source

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS20220355108A1Capacitor testing for implantable stimulators

Publication Date: 2022.11.10 COCHLEAR LIMITED

AI summary

Examples disclosed herein are relevant to testing capacitors to identify potentially faulty DC blocking capacitors in implantable stimulators. In an example, the test includes selecting an active electrode, a return electrode, and a reference electrode. Short duration monophasic stimulation is used to charge up the DC blocking capacitors of the active and return electrodes. The electrodes are subsequently disconnected from all other nodes except a discharge circuit (e.g., a star circuit) and the tissue. The reference electrode is used to measure the voltage of the DC blocking capacitor of the active electrode during the charging phase and the discharging phase (via the discharge circuit). The characteristics of one or more of the capacitors charging or discharging can be sensed and then analyzed to determine whether the one or more capacitors are functioning properly. Faulty capacitors can be identified by comparing actual and expected characteristics.