Closed-Loop Neural Stimulator for Constant Current Under Changing Load
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Solution Overview
Problem
Traditional constant current sources used in neural stimulation can cause irreversible electrochemical reactions due to charge accumulation at the tissue-electrode interface, as they have high output impedance and require instantaneous adjustments with changing tissue resistance.
Innovation Solution
A closed loop control system with a stimulator that includes a voltage source, adjustable gain amplifier, and feedback component to sample current over time, ensuring a constant current delivery with low output impedance, reducing the need for instantaneous adjustments and minimizing harmful reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a constant current source with high output impedance is used to deliver current to neural tissue, then the current remains constant despite changing tissue resistance, but charge accumulates at the tissue-electrode interface causing irreversible electrochemical reactions that can damage the tissue or electrode
Solution Approach 1:
The patent implements a feedback control system that continuously monitors the actual current delivered to the neural tissue and adjusts the output voltage dynamically to maintain the desired current level. This feedback mechanism allows the system to achieve constant current delivery without requiring high output impedance, thereby preventing charge accumulation and harmful electrochemical reactions at the tissue-electrode interface
Solution Approach 2:
The system transitions from a static high-impedance constant current source to a dynamic voltage-source-based control system that actively adapts its output characteristics in real-time based on tissue resistance changes and current feedback, enabling constant current delivery with low output impedance
2Object-affected harmful factors
If a voltage source with low output impedance is used, then harmful electrochemical reactions are minimized, but the current varies with changing tissue resistance
Solution Approach 1:
By incorporating a feedback loop that senses the actual current and compares it to the reference current, the system can detect deviations caused by tissue resistance changes and automatically adjust the output voltage to restore the desired current level, thereby maintaining current constancy while preserving the low output impedance benefit
Solution Approach 2:
The system dynamically changes the output voltage parameter in response to feedback signals, allowing it to maintain constant current delivery despite variations in tissue resistance, while the low output impedance characteristic remains preserved throughout the operation
Data Source
AI summary
A closed loop control system automatically ensures that an output of a device is constant. The system can receive an input to set a fixed value for a variable (e.g., a current, a heart rate, a tissue perfusion, an ion level, etc.), and this variable can be delivered to a feedback component. The system can also include the device to deliver the variable to a load. The feedback component can be coupled to the delivery device to sample the output of the delivery device at different times. Based on the sampling, the feedback component can vary a property of the delivery device related to the delivery of the variable to the load to ensure that the variable remains constant at the fixed value. In some instances, the system can be implemented as a stimulator that delivers the constant current of a current source and has a low output impedance of a voltage source.