Neural Stimulation Charge Compensation Circuit for Safe Biphasic Pulses
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Solution Overview
Problem
Existing artificial retinas and neural stimulation devices face challenges in effectively stimulating bipolar cells deep within the retina, leading to suboptimal stimulation resolution and potential nerve tissue damage due to uneven charge distribution during 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 levels and stimulate both ganglion and bipolar cells effectively.
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 the charge balance performance is improved, but the occupied area increases which cannot be integrated in limited circuit design space
Solution Approach 1:
The patent changes the fundamental parameter of charge balancing from passive RC circuit discharge to active current compensation. By using a compensation current generator that produces an equal and opposite current to cancel residual charges, the system achieves effective charge balancing without requiring large capacitance values, thus resolving the contradiction between charge balance performance and occupied area.
Solution Approach 2:
The patent replaces the passive mechanical RC discharge mechanism with an active electronic compensation mechanism. Instead of relying on capacitor discharge through resistors, the system uses controlled current sources to actively neutralize residual charges, achieving the same charge balancing effect with significantly reduced area requirements.
2Reliability
If the stimulation pulse width is increased to stimulate bipolar cells deeper in the retina, then the stimulation effectiveness is improved, but the charge amount increases which may exceed safe charge limits
Solution Approach 1:
The patent implements a feedback mechanism where the compensation current generator monitors and responds to residual charges on the electrode. By detecting the charge imbalance and generating a compensating current proportional to the residual charge, the system can safely extend pulse widths for deeper bipolar cell stimulation while automatically preventing charge accumulation that would exceed safety limits.
Solution Approach 2:
The patent applies preliminary anti-action by proactively generating compensation currents that counteract residual charges before they can accumulate to harmful levels. This preventive approach allows the use of wider stimulation pulses for effective bipolar cell activation while ensuring charge safety through advance compensation.
3Measurement precision
If the amplitude of the pulse current is increased to improve stimulation precision, then the stimulation resolution is improved, but the charge amount increases which may damage nerve tissue
Solution Approach 1:
The feedback mechanism in the compensation current generator allows the system to use higher amplitude pulse currents for improved stimulation resolution while automatically compensating for the resulting residual charges. The compensation current is dynamically adjusted based on the actual charge remaining on the electrode, enabling safe high-precision stimulation.
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.