Analog Current Output Module Overload Detection Circuit

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Solution Overview

Problem

Analog current output modules in PLC systems are prone to damage due to current output overloads caused by malfunctions or interconnection errors in external load devices, leading to increased installation costs and potential malfunctions of additional overload cut-off devices.

Innovation Solution

Incorporating a microprocessor unit (MPU), digital-to-analog (D/A) converter, analog current output circuit, and an overload detecting unit with a comparator and reference value setting unit to detect overloads by measuring control currents and cutting off output or generating an error current value, preventing damage to both the external load system and the analog current output module.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If an additional overload cut-off device is installed between the external load system and the analog current output module, then the PLC module and external load system are protected from damage, but the installation cost increases and the device complexity increases

Engineering Contradiction:

Improveprotection from overload damageVSAvoidinstallation of additional devices

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The overload detection function is merged with the analog current output module by integrating a comparator and reference value setting unit into the existing module structure. This eliminates the need for separate external overload cut-off devices while maintaining protection functionality, thereby reducing device complexity and installation costs.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The analog current output module performs self-protection by incorporating internal overload detection circuitry that automatically monitors output current and triggers protective action when overload conditions are detected, eliminating the need for external protection devices and reducing system complexity.

Inventive Principle:

Principle #25Self-service

2Reliability

If an additional overload cut-off device is installed for each output channel, then overload protection is provided, but the installation cost increases

Engineering Contradiction:

Improveoverload protectionVSAvoidinstallation cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The overload detection functionality is combined within the analog current output module itself, allowing a single integrated solution to protect multiple output channels without requiring separate external cut-off devices for each channel, thereby reducing overall installation costs.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If the external load impedance is higher than the standard value due to malfunctions or interconnection errors, then the analog voltage is excessively increased, but this causes damage to the external load system and the analog current output module

Engineering Contradiction:

Improvestability of current outputVSAvoidoverload damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The comparator continuously monitors the control current and compares it against a reference value before excessive voltage can cause damage. When an overload condition is detected (control current exceeds reference value), the system triggers protective action in advance to prevent damage to the external load system and analog current output module.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The overload detection mechanism uses feedback through the comparator to monitor the control current output and automatically trigger protective measures when abnormal conditions are detected, maintaining system stability and preventing damage from excessive voltage caused by high load impedance.

Inventive Principle:

Principle #23Feedback

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

Effectively detects and prevents overload damage by cutting off current output or generating an error output, enhancing stability and reducing installation costs by integrating overload detection within the analog current output module.

Implementation Method 1

an overload detecting unit detecting whether an overload occurs by measuring the control current and comparing a value of the control current and a preset reference value

Methodology Applied

Scientific EffectElectrical Resistance: Electrical Resistance

Data Source

PatentUS9594416B2Analog current output module

Publication Date: 2017.03.14 LSIS CO LTD

AI summary

An analog current output module includes an MPU generating and outputting a digital signal, a D/A converter converting the digital signal into an analog signal and outputting the analog signal, an analog current output circuit outputting a control current corresponding to the analog signal output from the D/A converter, and an overload detecting unit detecting whether an overload occurs by measuring the control current and comparing a value of the control current and a preset reference value, wherein the overload detecting unit sets the reference value on the basis of a reference value generating signal delivered from the MPU, and the overload detecting unit comprises a comparator comparing the control current value and the reference value and detecting whether the overload occurs, and a reference value setting unit generating the reference value according to the reference value generating signal and providing the reference value to the comparator.