Isolated Differential Sampling Circuit for Wide Common-Mode Voltage

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Solution Overview

Problem

Conventional sampling circuits are limited by power supply voltage rails, leading to noise, reduced linearity, and increased power consumption when sampling signals that exceed these rails, and they fail to effectively handle common-mode voltage variations.

Innovation Solution

The implementation of a differential sampling circuit with AC-coupled switch control and charge pumps allows for sampling of signals below, at, and above the power supply rails, using charge pumps to generate internal common mode voltages and maintain circuit reliability without additional noise or power consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional sampling circuits are used to sample signals exceeding power supply rails, then the circuit can operate within standard voltage limits, but noise increases, linearity deteriorates, and power consumption increases

Engineering Contradiction:

Improvecircuit reliabilityVSAvoidnoise

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent introduces an intermediary voltage translation mechanism that mediates between the high-voltage input signal and the low-voltage sampling circuit. The circuit translates the common-mode voltage level of incoming signals to match the internal voltage rails, allowing signals exceeding supply rails to be sampled without direct exposure to voltage limitations. This intermediary translation layer eliminates noise and linearity issues that would otherwise occur when sampling signals beyond the circuit's voltage range.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Manufacturing precision

If conventional sampling circuits are used to sample signals exceeding power supply rails, then the circuit can operate within standard voltage limits, but linearity deteriorates

Engineering Contradiction:

Improvesampling linearityVSAvoidsignal distortion

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent dynamically changes the voltage reference parameters internally to match the input signal's common-mode level. By adjusting the internal voltage translation references based on the incoming signal characteristics, the circuit maintains optimal linearity across varying input voltage ranges. This parameter adaptation allows accurate sampling of signals that exceed the fixed power supply rails without introducing distortion.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If conventional sampling circuits are used to sample signals exceeding power supply rails, then the circuit can operate within standard voltage limits, but power consumption increases

Engineering Contradiction:

Improvecircuit reliabilityVSAvoidpower consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The voltage translation mechanism acts as an energy-efficient intermediary that enables high-voltage signal sampling without requiring the entire circuit to operate at high voltage. Only the translation stage consumes additional power to handle the voltage level mismatch, while the core sampling circuit operates efficiently at standard voltage levels. This localized energy expenditure maintains overall power efficiency while enabling extended voltage range operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Adaptability or versatility

If conventional sampling circuits are used, then the circuit structure remains simple, but the circuit cannot sample signals outside supply voltage rails

Engineering Contradiction:

Improveinput voltage rangeVSAvoidcircuit structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent employs voltage translation circuits as intermediary components that extend the input voltage range without fundamentally redesigning the entire sampling architecture. The translation stage interfaces between the external high-voltage signals and the internal low-voltage sampling circuit, maintaining compatibility with standard ADC interfaces while enabling sampling of signals that exceed supply rails. This modular approach adds minimal complexity while maximizing adaptability.

Inventive Principle:

Principle #24Intermediary (Mediator)

5Reliability

If conventional sampling circuits are used, then the circuit operates within supply voltage limits, but common-mode voltage variations cause charge variations on sampling capacitors

Engineering Contradiction:

Improvecommon-mode rejectionVSAvoidsignal accuracy

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The voltage translation mechanism serves as an intermediary that isolates the sampling circuit from common-mode voltage variations. By translating the common-mode level before sampling, the circuit prevents these variations from being directly coupled to the sampling capacitors. This intermediary translation stage effectively rejects common-mode disturbances while preserving the differential signal integrity, eliminating charge variations that would otherwise degrade measurement accuracy.

Inventive Principle:

Principle #24Intermediary (Mediator)

Data Source

PatentUS8907703B1Isolated high voltage sampling network

Publication Date: 2014.12.09 ANALOG DEVICES INT UNLTD CO

AI summary

Methods and systems for sampling a differential signal. The sampling circuit includes a differential input and a differential output. A logic control block, which is powered by VDD and VSS sources, controls the state of switches used to sample and store differential signals. The logic control block is AC coupled to the switches. The sampling circuit is configured to sample a common mode voltage at the differential input of a level that exceeds that of the VDD and VSS sources.