EEG Input Converter Using Switched-Capacitor Voltage Boosting
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Solution Overview
Problem
EEG monitoring systems for continuous wear face challenges in minimizing noise figure and current consumption, particularly in delta-sigma A/D converters, which require high clock rates and significant power usage due to amplification needs, limiting battery life and system unobtrusiveness.
Innovation Solution
The implementation of voltage transformers upstream of the input stage in delta-sigma A/D converters to increase the input voltage, reducing the relative noise contribution and allowing for lower amplification gain, thereby decreasing current consumption and noise sensitivity, while maintaining signal quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If amplification gain is increased to improve signal quality, then signal-to-noise ratio improves, but current consumption increases
Solution Approach 1:
The voltage transformer is placed upstream of the input stage to perform voltage transformation before the signal enters the amplification stage. This preliminary action increases the input voltage level, reducing the required amplification gain and thereby decreasing current consumption while maintaining signal quality
Solution Approach 2:
A voltage transformer is introduced as an intermediary component between the input signal source and the amplification stage. This mediator transforms the input voltage to a higher level, reducing the burden on the amplifier and lowering its current consumption while preserving signal integrity
2Measurement precision
If amplification gain is increased to reduce noise sensitivity, then noise figure decreases, but power consumption increases
Solution Approach 1:
The voltage transformer performs voltage transformation before the signal reaches the amplification stage, preliminarily increasing the voltage level. This reduces the required amplification gain, thereby decreasing power consumption while maintaining low noise figure
Solution Approach 2:
The voltage transformer acts as an intermediary that increases input voltage before amplification, reducing the amplification gain needed and consequently lowering power consumption while maintaining noise performance
3Measurement precision
If clock rate is increased to improve conversion speed, then conversion accuracy improves, but current consumption increases
Solution Approach 1:
The voltage transformer preliminarily increases the input voltage level before the signal enters the A/D converter. This reduces the required amplification gain, allowing the system to use lower clock rates while maintaining conversion accuracy, thereby decreasing current consumption
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
This approach effectively reduces the noise figure and current consumption of the A/D converter, enhancing the signal-to-noise ratio and extending battery life in wearable EEG monitoring systems without increasing power consumption, enabling continuous operation for several days.
Implementation Method 1
The input converter comprises a voltage transformer placed in the input converter upstream of the input stage and having a transformation ratio such that it provides an output voltage larger than the input voltage
Data Source
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AI summary
In order to minimize noise and current consumption in an EEG monitoring system (40) which can be continuously carried by a person being monitored, an input converter (44) for an EEG monitoring system is devised. The analog-to-digital converter of the input converter has an input stage, an output stage, and a feedback loop, and the input stage comprises an amplifier (QA) and an integrator (RLF). A voltage transformer (IT) is placed in the input converter upstream of input stage. The transformation ratio of the voltage transformer (IT) has a transformation ratio such that it provides an output voltage larger than the input voltage, thereby multiplying the signal voltage for the input stage by a fixed factor. The voltage transformer (IT) is a switched-capacitor voltage transformer having at least two capacitors (Cx, Cy, Cz) The invention further provides a method of converting an analog signal, and an EEG monitoring system comprising the input converter (44).