Bidirectional Pulse Current Circuit for Retinal Charge Balance
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Solution Overview
Problem
Existing artificial retinas and neural stimulation devices face limitations in stimulating bipolar cells deep within the retina, leading to suboptimal stimulation resolution and potential nerve tissue damage due to uneven charge distribution during neural stimulation.
Innovation Solution
A pulse current generation circuit and charge compensation circuit that generate bidirectional pulse currents with adjustable precision and amplitude, ensuring safe charge balance without the need for large capacitors, by using a current generator and compensation circuit to manage charge amounts and prevent net charge accumulation on nerve tissue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the capacitance of the capacitor in the RC circuit is increased to balance more charges, then charge balance performance is improved, but the occupied area increases and cannot be integrated
Solution Approach 1:
The patent replaces the passive RC circuit (mechanical/electrical system with large capacitor) with an active charge compensation circuit that uses operational amplifiers and transistors to actively balance charges. This substitution allows achieving the same charge balance function without requiring large capacitance values, thus reducing the occupied area while maintaining reliability.
Solution Approach 2:
The patent changes the approach from passive charge balancing using large capacitance values to active charge balancing using controlled current sources and feedback mechanisms. By changing the balancing method from capacitive storage to active compensation, the system achieves charge balance with much smaller circuit components, resolving the area constraint.
2Measurement precision
If the stimulation pulse width is increased to stimulate bipolar cells, then stimulation resolution is improved, but the pulse current amplitude must be reduced to maintain safe charge levels
Solution Approach 1:
The patent implements dynamic control of pulse parameters through a programmable pulse generator that can adjust pulse width and amplitude based on real-time feedback from charge detection circuits. This dynamic adjustment allows the system to maintain optimal stimulation resolution while ensuring charge balance safety constraints are met, resolving the trade-off between resolution and power.
Solution Approach 2:
The patent incorporates feedback mechanisms where charge detection circuits monitor the charge delivered to neural tissue and provide feedback to the pulse generator. This feedback loop enables real-time adjustment of pulse parameters, allowing the system to maintain high stimulation resolution while automatically ensuring that charge levels remain within safe limits, thus resolving the contradiction between pulse width and amplitude.
Data Source
AI summary
A pulse current generation circuit (100) for neural stimulation includes an analogue signal receiving device (101) for receiving an analogue signal; an analogue-to-digital converter (102) for converting the analogue signal into a digital control signal; a current signal controller (103) for producing, according to the digital control signal, pulse current parameters for generating bidirectional pulse current signals; and a current generator (104) for generating, according to the pulse current parameters, bidirectional pulse current signals for neural stimulation, and the current generator can generate pulse currents of different precisions according to the pulse current parameters. In addition, the present invention further relates to a charge compensation circuit, a charge compensation method, and an implantable electrical retina stimulator using the pulse current generation circuit or the charge compensation circuit.