Single Capacitor Tissue Stimulation Circuit with Charge Balancing

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Solution Overview

Problem

Conventional implantable medical device (IMD) pace delivery circuits are physically large due to large capacitors and suffer from charge imbalance issues during tissue stimulation, leading to ineffective tissue stimulation and potential damage from DC currents.

Innovation Solution

A tissue stimulation circuit with reduced capacitance, incorporating a single capacitor and a switching circuit that balances charge by recharging before and after stimulation pulses, and utilizing a current smoothing circuit to minimize voltage spikes and ensure net charge balance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional pace delivery circuits use large capacitors to prevent DC current and store charge, then charge balance is maintained, but the device size increases significantly

Engineering Contradiction:

Improvecharge balanceVSAvoidIMD size

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The patent combines the functions of multiple capacitors into a single capacitor with reduced size. The switching circuit integrates charge storage, DC prevention, and charge balancing functions that were previously handled by separate capacitor components, thereby reducing overall device volume while maintaining charge balance reliability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent changes the operational parameters by using a switching circuit to dynamically control charge delivery and rebalancing. Instead of relying on large fixed capacitors, the system uses controlled switching to achieve charge balance with smaller capacitance values, effectively reducing device size while maintaining functional reliability.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the capacitor is recharged to a different voltage to prepare for different pace pulse amplitudes, then adaptability is improved, but charge imbalance occurs causing ineffective tissue stimulation

Engineering Contradiction:

Improvepace pulse amplitude adjustmentVSAvoidtissue stimulation effectiveness

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent implements a feedback mechanism through the switching circuit that monitors capacitor voltage and tissue stimulation requirements. When the capacitor voltage needs adjustment for different pace pulse amplitudes, the switching circuit controls recharge operations to maintain net charge balance, ensuring that adaptability in pulse amplitude adjustment does not compromise stimulation effectiveness.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system dynamically adjusts capacitor recharge timing and voltage levels based on required pace pulse amplitudes. The switching circuit enables real-time adaptation of charge parameters while maintaining charge balance through controlled recharge operations, allowing versatile amplitude adjustment without sacrificing stimulation reliability.

Inventive Principle:

Principle #15Dynamics

3Reliability

If multiple capacitors are used in the pace delivery circuit, then charge balance and DC prevention are achieved, but device complexity and manufacturing cost increase

Engineering Contradiction:

Improvecharge balanceVSAvoidcircuit component count

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the functions of multiple capacitors into a single capacitor system controlled by a switching circuit. This consolidation reduces the number of discrete components, simplifying the circuit architecture and reducing manufacturing complexity while maintaining charge balance functionality through intelligent switching control.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The single capacitor in the patent serves multiple functions simultaneously: charge storage, DC current prevention, and charge balancing. The switching circuit enables this multi-functionality by dynamically controlling charge delivery and recharge operations, eliminating the need for separate dedicated capacitors for each function and thereby reducing overall device complexity.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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

The solution results in a smaller, more cost-effective IMD with improved tissue stimulation efficiency, reduced charge imbalance, and minimized DC current flow through the tissue interface, maintaining effective therapeutic stimulation while preventing tissue damage.

Implementation Method 1

One capacitor, connected to a battery, stores a charge that is applied to the heart muscle

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

A tissue stimulation circuit with reduced capacitance, incorporating a single capacitor and a switching circuit that balances charge by recharging before and after stimulation pulses

Methodology Applied

Scientific EffectCharge balancing:

Implementation Method 3

utilizing a current smoothing circuit to minimize voltage spikes and ensure net charge balance

Methodology Applied

Scientific EffectCurrent smoothing:

Data Source

PatentUS7715911B2Apparatus for tissue stimulation

Publication Date: 2010.05.11 MEDTRONIC INC

AI summary

Delivering electrical stimulation to a body tissue by a circuit. The circuit includes a first and second terminal electrically coupled to body tissue. A sole capacitor has a first electrode and a second electrode. The first electrode is coupled to the first terminal. The second electrode is coupled to a power source through a switch.