Loop Current Control Circuit for Stable Two-Wire Field Devices
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Solution Overview
Problem
Existing loop-powered field devices face challenges in handling rapid changes in loop current, leading to inefficient energy use and potential signaling issues, particularly when power requirements fluctuate.
Innovation Solution
A field device configuration with an asymmetrically conducting device, energy storage device, and controllable shunt regulator, which allows for stable loop current control and efficient energy management by maintaining a constant voltage across the loop current control device, even with varying loop currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an energy storage device is used to store energy from the two-wire current loop, then the field device can operate during power fluctuations, but the circuit becomes more complex and requires additional components
Solution Approach 1:
The patent combines multiple functions into a single integrated circuit architecture where the energy storage device, asymmetrically conducting device, and shunt regulator work together as a unified power management system. This merging approach reduces the need for separate control circuits and minimizes overall system complexity while maintaining reliable operation during power fluctuations.
Solution Approach 2:
The asymmetrically conducting device acts as an intermediary element that automatically controls the charging and discharging of the energy storage device based on voltage conditions. This intermediary component simplifies the circuit by eliminating the need for complex active control circuitry, as the asymmetric conduction property inherently regulates power flow during different operational states.
2Reliability
If the field device handles rapid changes in loop current, then communication stability is improved, but current transients and voltage fluctuations increase
Solution Approach 1:
The energy storage device is positioned in the circuit to provide beforehand cushioning against rapid current changes. When loop current fluctuates, the energy storage device absorbs or supplies energy to maintain stable voltage across critical components, thereby cushioning the impact of current transients before they can disrupt communication or damage sensitive circuitry.
Solution Approach 2:
The asymmetrically conducting device converts the harmful effect of current transients into a beneficial control mechanism. By allowing current to pass in one direction while blocking it in the opposite direction, the device transforms rapid current fluctuations into a controlled charging/discharging cycle of the energy storage device, thereby stabilizing voltage and protecting the circuit while utilizing the transient energy constructively.
3Use of energy by moving object
If a controllable shunt regulator is added to maintain stable voltage, then energy efficiency is improved, but the device complexity and cost increase
Solution Approach 1:
The shunt regulator is configured to automatically regulate voltage across the energy storage device without requiring external control signals. The regulator monitors the voltage condition and self-adjusts its conduction state to maintain optimal charging voltage, thereby improving energy efficiency by preventing overcharging and reducing power losses while eliminating the need for additional control circuitry.
Solution Approach 2:
The shunt regulator dynamically changes its electrical parameters (conduction state) based on the voltage across the energy storage device. By adjusting its resistance or conduction level in response to voltage changes, the regulator optimizes energy transfer efficiency during different operational phases, ensuring maximum energy utilization from the two-wire current loop while maintaining simple circuit architecture.
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
Enhances energy efficiency, improves signaling performance, and reduces circuit complexity and costs by stabilizing loop current control, especially during rapid power fluctuations.
Implementation Method 1
an asymmetrically conducting device provided in the electric circuit between the first node of the electric circuit and a second node of the electric circuit, the asymmetrically conducting device being configured to allow current to flow through the asymmetrically conducting device from the first node towards the second node, and to substantially prevent current to flow through the asymmetrically conducting device from the second node towards the first node
Implementation Method 2
an energy storage device for storing energy received via the two-wire current loop
Implementation Method 3
a controllable shunt regulator provided in the electric circuit between the first node of the electric circuit and the second loop terminal, in parallel with the energy storage device
Data Source
AI summary
A field device comprising a first loop terminal and a second loop terminal; a measurement unit; a loop current control device for controlling the loop current to encode a process variable determined by the measurement unit, the loop current control device being provided in the electric circuit between the first loop terminal and an a first node of the electric circuit; an asymmetrically conducting device provided in the electric circuit between the first node of the electric circuit and a second node of the electric circuit; an energy storage device in the electric circuit between the second node of the electric circuit and the second loop terminal; and a controllable shunt regulator provided in the electric circuit between the first node of the electric circuit and the second loop terminal, wherein the measurement unit is in the electric circuit between the second node and the second loop terminal.