Discrete Input Circuit With Decoupled Logic Thresholds
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Solution Overview
Problem
Conventional ground open input circuits are limited in their operating range when power supply voltage varies widely, and they struggle to meet the varying input voltage thresholds required by logic devices to register logic high or low states effectively.
Innovation Solution
The solution involves an input device with a voltage divider node connected to a load, using two switching components (transistors) and resistors to decouple the voltage supplied to the load from the logic device, allowing for discrete logic high and low inputs regardless of the power supply voltage, with additional components like diodes and capacitors for protection and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional ground open input topology is used, then the circuit can provide ground and open indications to logic components, but the operating range is restricted when power supply voltage varies widely
Solution Approach 1:
The input circuit is segmented into two independent voltage supply systems: one for the load (first voltage source) and one for the logic device input (second voltage source). This segmentation allows each part to operate with its own optimized voltage level, enabling the circuit to maintain reliable logic level registration across a wide range of power supply voltages.
Solution Approach 2:
A decoupling network including resistors and switching components is introduced as an intermediary between the load circuit and the logic device input. This intermediary isolates the logic device from voltage variations in the load supply, allowing accurate logic level detection regardless of the first voltage source's fluctuations.
2Measurement precision
If conventional input topology is used, then the circuit structure is simple, but it cannot provide accurate logic high and low inputs when voltage supply varies over wide range
Solution Approach 1:
The circuit employs dynamic switching components (transistors) that automatically adjust the coupling between the load and logic device based on voltage conditions. This dynamic behavior enables accurate logic level registration across varying voltages without requiring complex manual adjustment mechanisms.
Solution Approach 2:
The circuit changes the electrical parameters (voltage levels, current paths) dynamically based on the state of the first voltage source. By using switching components controlled by voltage dividers, the circuit adapts its parameter configuration to maintain accurate logic level detection despite supply voltage variations.
Data Source
AI summary
An input device includes an input line connected to a voltage divider node for connecting a load to the voltage divider node. A first switching component connects to the voltage divider node. A first resistor connects to the voltage divider node for connecting a first voltage source to the input line. A second resistor connects between the input line and the voltage divider node for limiting current to the load, wherein the first voltage source is also connected to the first switching component. A second switching component is operatively connected to the first switching component, wherein the second switching component is configured to connect an second voltage source to a logic device for discrete input to the logic device that is decoupled from voltage supplied to the input line by the first voltage source for providing logic high and low input regardless of voltage supplied by the first voltage source.