SOI Analog Front Circuit for Hearing Aid Noise Reduction

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Solution Overview

Problem

Current medical hearing aid devices face challenges with high noise, low control accuracy, and high power consumption due to limitations in analog feedback circuits, particularly in implementing automatic gain control loops and Sigma_delta analog-to-digital converters.

Innovation Solution

An SOI analog front circuit is designed with an automatic gain control loop and a 2-order-3-bit-quantization Sigma-Delta analog-to-digital converter, incorporating a variable-gain amplifier, fixed-gain amplifier, buffers, comparators, and a peak statistics determination logic and gain control logic module, which reduces noise and power consumption while enhancing accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional bulk-silicon CMOS technology is used for the analog front circuit, then the circuit can be implemented with standard processes, but the device suffers from high power consumption, high noise, and low integration capability

Engineering Contradiction:

ImprovemanufacturabilityVSAvoidpower consumption

Core Design Contradiction:

Ease of manufactureVSUse of energy by moving object

Solution Approach 1:

The patent transitions from bulk-silicon CMOS to SOI CMOS technology, changing the fundamental substrate parameter to achieve lower power consumption while maintaining manufacturability through established SOI fabrication processes

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the conventional bulk-silicon mechanical structure with SOI technology that uses dielectric isolation layers to eliminate parasitic effects, thereby reducing power consumption and improving circuit performance

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Ease of manufacture

Engineering Contradiction:

ImprovemanufacturabilityVSAvoidcontrol accuracy

Core Design Contradiction:

Ease of manufactureVSMeasurement precision

Solution Approach 1:

The patent changes the substrate technology from bulk-silicon to SOI, which fundamentally alters the electrical characteristics by eliminating parasitic pnpn structures and reducing leakage currents, thereby improving control accuracy and reducing noise

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent extracts and removes the parasitic pnpn structures inherent in bulk-silicon technology by using SOI technology with full dielectric isolation, thereby eliminating the source of noise and improving measurement precision

Inventive Principle:

Principle #2Taking out (Extraction)

3Ease of manufacture

If conventional bulk-silicon CMOS technology is used for the analog front circuit, then the circuit can be implemented with standard processes, but the device achieves low integration due to necessary well structures and isolation regions

Engineering Contradiction:

ImprovemanufacturabilityVSAvoidintegration capability

Core Design Contradiction:

Ease of manufactureVSDevice complexity

Solution Approach 1:

The patent merges the isolation function into the substrate structure itself by using SOI technology, where the buried oxide layer provides automatic isolation between devices, eliminating the need for separate well structures and isolation regions, thereby enabling higher integration

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent changes the substrate structure from bulk-silicon requiring separate isolation regions to SOI where the dielectric layer inherently provides isolation, simplifying the device structure and improving integration capability

Inventive Principle:

Principle #35Parameter changes

4Ease of operation

If analog feedback circuits are used for automatic gain control, then the circuit modules are independent and easy to vary, but the implementation is difficult with high noise and high power consumption

Engineering Contradiction:

Improvecircuit modularityVSAvoidpower consumption

Core Design Contradiction:

Ease of operationVSUse of energy by moving object

Solution Approach 1:

The patent substitutes conventional analog feedback circuits with Sigma-Delta modulation architecture, replacing traditional analog filtering and integration methods with oversampling and digital filtering techniques, thereby reducing power consumption while maintaining modularity

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

5Measurement precision

If high-order integrators are used for Sigma_delta analog-to-digital converter, then high accuracy can be achieved, but the power consumption becomes high

Engineering Contradiction:

Improveconversion accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent employs periodic oversampling in the Sigma-Delta converter, distributing the conversion process over many cycles with a high-order modulator, thereby achieving high accuracy through averaging while keeping the power consumption of individual stages low

Inventive Principle:

Principle #19Periodic action

Data Source

PatentUS8767988B2Analogic front circuit for medical device

Publication Date: 2014.07.01 INST OF MICROELECTRONICS CHINESE ACAD OF SCI LTD

AI summary

An analog front circuit for a medical device includes an automatic gain control loop and a 2-order-3-bit-quantization Sigma-Delta analog-to-digital converter. The automatic gain control loop is configured to implement automatic control of loop gain and output an analog signal to the 2-order-3-bit-quantization Sigma-Delta analog-to-digital converter. The 2-order-3-bit-quantization Sigma-Delta analog-to-digital converter is configured to convert the analog signal output from the automatic gain control loop into a digital code and output the digital code to a DSP for processing.