Signal Interface Circuit with Sigma-Delta Modulator
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional signal interfaces for industrial instrumentation face challenges such as interference, limited voltage range, high costs, and complex galvanic isolation in handling both analog and digital signals, particularly in motor drives and frequency converters, due to the use of Successive Approximation Register (SAR) converters and optoisolators.
Innovation Solution
A signal interface unit with integrated sigma-delta modulator circuits and galvanic isolation, allowing for flexible conversion of both analog and digital signals, and eliminating the need for separate units by using a single interface structure that can handle multiple input channels with adjustable measurement ranges and integrated galvanic isolation, reducing manufacturing and installation costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If SAR type A/D converters are used for analog signal digitization, then conversion speed is improved, but measurement precision deteriorates due to interference peaks at sampling moments
Solution Approach 1:
The patent introduces an analog multiplexer as an intermediary component that sequentially connects different analog input channels to a single A/D converter. This allows the use of slower, more precise A/D converters while maintaining high measurement speed through time-division multiplexing, thereby resolving the contradiction between conversion speed and measurement precision.
Solution Approach 2:
The patent employs periodic sampling and conversion cycles where each input channel is sequentially activated in a time-division manner. The analog multiplexer switches between channels in a periodic sequence, allowing the A/D converter to process each channel at optimal precision while achieving overall high-speed conversion across multiple channels.
2Measurement precision
If hardware filters are added to prevent interference, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The analog multiplexer acts as an intermediary that isolates each input channel from others during conversion, preventing cross-channel interference. This sequential switching mechanism inherently reduces interference without requiring complex hardware filters, thus improving measurement precision while keeping device complexity low.
3Measurement precision
If analog and digital signals are separated into different units, then signal processing precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the processing of both analog and digital input signals into a single unified interface unit. The analog multiplexer and A/D converter handle analog signals, while digital input channels are processed through the same control logic, eliminating the need for separate processing units and reducing overall device complexity while maintaining signal processing precision.
Solution Approach 2:
The interface unit is designed with universal functionality to handle both analog and digital input signals through a common architecture. The analog multiplexer can be configured to process different signal types, and the control unit manages both analog-to-digital conversion and digital input processing, making the system multi-functional without requiring separate dedicated units.
4Reliability
If optoisolators are used for galvanic isolation, then reliability is improved, but power loss increases due to high current requirements
Solution Approach 1:
The patent uses a digital isolator that copies and transfers digital signals between isolated grounds through magnetic coupling or other isolation mechanisms. This approach provides reliable galvanic isolation while consuming minimal power compared to optoisolators, as it does not require driving LEDs with high currents and can directly transfer digital logic levels across the isolation barrier.
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 solution provides accurate, cost-effective, and interference-resistant signal processing with 16-bit resolution, eliminating ground currents and reducing structural complexities in motor drive systems by positioning the interface unit on a separate circuit board, thus improving reliability and maintenance.
Implementation Method 1
The A/D converter comprises an integrated sigma-delta modulator circuit which generates a digitized 1-bit signal representing the input signal voltage level
Implementation Method 2
The input signals of these two or more input channels are connected alternately by an analog multiplexer to an analog-to-digital (A/D) converter
Implementation Method 3
The A/D converter comprises an integrated sigma-delta modulator circuit which generates a digitized 1-bit signal representing the input signal voltage level to be interpreted by a control unit irrespective of whether the input channel signal is a digital or analog signal
Data Source
AI summary
Interface unit for voltage input signals comprising two or more input channels. The input signals of these two or more input channels are connected alternately by an analog multiplexer to an analog-to-digital converter. The A/D converter comprises an integrated sigma-delta modulator circuit which generates a digitized 1-bit signal representing the input signal voltage level for a control unit irrespective of whether the input channel signal is digital or analog. By means of the invention all input voltage channels are made similar such that the input channels of the interface unit can receive an analog or digital signal irrespective of each other.