Comparison Control Circuit With Schmitt Trigger Noise Immunity

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Solution Overview

Problem

Comparators in circuits such as analog-to-digital converters and low-dropout regulators often output unclean comparison signals due to noise from input signals and power sources, leading to misjudgments and incorrect outputs.

Innovation Solution

A comparison control circuit comprising a comparator, a Schmitt trigger, a capacitor set, and a logic circuit, which adjusts the second input signal based on a trigger signal to stabilize the comparison signal, thereby reducing noise immunity and ensuring accurate outputs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a comparator is used to compare input signals, then the comparison function is achieved, but the output signal becomes unclean due to noise from input signals and power sources

Engineering Contradiction:

Improvesignal cleanlinessVSAvoidnoise susceptibility

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A Schmitt trigger is introduced as an intermediary component between the comparator and the output. The Schmitt trigger receives the comparator's output signal and regenerates a clean digital signal through its hysteresis mechanism, effectively isolating the comparator from noise effects and producing a clean output signal.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The Schmitt trigger implements positive feedback through its hysteresis mechanism, where the output signal is fed back to influence the threshold levels. This feedback mechanism creates noise immunity by establishing upper and lower threshold voltages that prevent noise-induced switching, ensuring reliable signal regeneration even in noisy environments.

Inventive Principle:

Principle #23Feedback

2Speed

If the comparator operates with larger bandwidth to respond to input signals, then the response speed is improved, but the circuit becomes more susceptible to noise

Engineering Contradiction:

Improveresponse speedVSAvoidnoise susceptibility

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The Schmitt trigger acts as a signal conditioning intermediary that accepts the comparator's fast but noisy output and regenerates a clean signal. This allows the comparator to maintain its high bandwidth and fast response characteristics while the Schmitt trigger eliminates the noise susceptibility issue by providing noise-immune signal regeneration.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If noise filtering is applied to clean the input signal, then the signal quality is improved, but the response time increases

Engineering Contradiction:

Improvesignal qualityVSAvoidresponse time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

Instead of filtering the input signal before comparison (which would slow down the response), the patent applies noise filtering in reverse by cleaning the comparator's output signal after comparison. The Schmitt trigger regenerates a clean digital signal from the comparator's output, achieving noise filtering without introducing additional response delay to the input signal processing.

Inventive Principle:

Principle #13The other way round (Inversion)

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

The proposed solution effectively filters noise from input signals, ensuring that circuits produce clean and correct signals, enhancing the reliability of analog-to-digital converters and low-dropout regulators.

Implementation Method 1

The capacitor set is configured to adjust the second input signal when being controlled

Methodology Applied

Scientific EffectCapacitance: Capacitance

Data Source

PatentUS11791812B2Analog-to-digital converter, low-dropout regulator and comparison control circuit thereof

Publication Date: 2023.10.17 REALTEK SEMICON CORP

AI summary

A comparison control circuit is adapted to analog-to-digital converters and low-dropout regulators. The comparison control circuit includes a comparator, a Schmitt trigger, a capacitor set and a logic circuit. The comparator is configured to output a comparison signal according to a first input signal and a second input signal, wherein the comparison signal is a first high voltage potential or a first low voltage potential. The Schmitt trigger is configured to output a trigger signal according to the comparison signal and a voltage potential range, wherein the voltage potential range is in a range from the first low voltage potential to the first high voltage potential. The capacitor set is configured to adjust the second input signal when being controlled. The logic circuit is configured to control the capacitor set according to the trigger signal to correspondingly adjust the second input signal.