Microphone ADC Feedback Path to Prevent Amplifier Saturation

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Solution Overview

Problem

Conventional analog-to-digital converters (ADCs) in microphones using MEMS devices face signal distortion due to saturation at maximum voltage, leading to increased harmonic components and degraded signal quality when the signal magnitude exceeds the power supply range.

Innovation Solution

The proposed ADC includes a first and second operator with a detector and selectors to manage signal magnitude, allowing the amplifier to operate on the output of the operators rather than the MEMS device, thereby preventing saturation and reducing noise, and utilizes a sigma-delta modulator with a digital-to-analog converter (DAC) for accurate signal conversion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If the amplifier amplifies the output of the MEMS device directly, then the signal gain is improved, but the amplifier output saturates at maximum voltage causing signal distortion

Engineering Contradiction:

Improvesignal gainVSAvoidsignal distortion

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The signal processing path is segmented into multiple stages: the MEMS device output is divided into a signal component and a feedback component. The feedback component is processed separately through the first operator to generate an analog value, which is then subtracted from the original signal. This segmentation prevents the amplifier from directly amplifying the full-range MEMS output that causes saturation, while still achieving the required signal gain through the amplified difference signal.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The first operator acts as an intermediary element between the MEMS device output and the amplifier input. It generates an analog value that represents a processed version of the MEMS output, which is then used to create a difference signal. This intermediary processing allows the amplifier to work with a reduced-range signal that avoids saturation, while the overall system still achieves the desired signal amplification.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If the amplifier output is increased to handle larger signal magnitudes, then the dynamic range is improved, but harmonic components increase degrading signal quality

Engineering Contradiction:

Improvedynamic rangeVSAvoidsignal quality

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The system performs preliminary processing through the first operator to generate the analog value before the amplifier stage. This preliminary action creates a scaled or processed version of the input signal that, when subtracted from the original, produces a difference signal with reduced magnitude. The amplifier then amplifies this pre-processed difference signal, achieving the required output level without the amplifier operating in its saturation region, thus maintaining signal quality across a wide dynamic range.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS10938398B2Analog-to-digital converter and microphone including the same

Publication Date: 2021.03.02 SEOUL NATIONAL UNIVERSITY R&DB FOUNDATION

AI summary

An analog-to-digital converter (ADC) includes a first operator configured to subtract an analog value from an analog signal; an amplifier configured to amplify an output of the first selector; a filter configured to filter an output of the amplifier; a quantizer configured to generate a digital bit stream from an output of the filter; and a digital-to-analog converter (DAC) configured to output the analog value according to the digital bit stream.