Fail-Safe DC Output Readback for Broken Wire Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fault detection methods for broken wires in industrial control systems, particularly in programmable logic controllers (PLCs), are either too expensive or require additional space, and existing integrated output drivers lack the ability to parameterize open-circuit or overload detection, leading to undesired heat generation and power loss.
Innovation Solution
A fail-safe input-output (I/O) module circuit with resistor dividers and diagnostic circuits that provide readback measurement signals to detect broken wires by examining voltage levels at outputs with and without a load, using resistor dividers to reduce voltages to manageable levels for lower voltage circuits, and employing diodes to bias outputs when switches are off.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional switches with series sense resistors are placed in parallel to detect broken wires, then broken wire detection capability is improved, but device complexity and cost increase
Solution Approach 1:
The existing high-side switch and sense resistor serve dual purposes: normal current switching and broken wire detection. By measuring the voltage across the sense resistor during normal operation and comparing it to threshold values, the system detects wire breaks without requiring additional detection circuitry. The sense resistor 'services' both its original function and the new detection function.
Solution Approach 2:
The existing components (high-side switch, sense resistor, microcontroller ADC) are made multi-functional. The sense resistor provides both current sensing for normal operation and open-circuit detection. The ADC channel is used for both routine current measurement and diagnostic wire break detection, eliminating the need for dedicated detection hardware.
2Reliability
If integrated output drivers are used with on-chip wire break detection, then detection capability is improved, but parameterization flexibility and current consumption tracking are lost
Solution Approach 1:
The system dynamically adjusts detection thresholds and operates in different modes based on real-time conditions. The microcontroller can modify threshold values, change detection sensitivity, and adapt the detection algorithm based on load characteristics and operating conditions, providing flexibility that fixed integrated circuits cannot match.
Solution Approach 2:
The system allows dynamic changing of detection parameters such as threshold voltages, sampling rates, and detection algorithms through software configuration. This enables the same hardware to be adapted to different application requirements, load types, and wire configurations without physical reconfiguration.
3Reliability
If measuring resistors are placed in the current path for protection, then protection capability is improved, but heat generation and power loss increase
Solution Approach 1:
The system uses the existing sense resistor (designed for minimal voltage drop during normal operation) for dual purposes. Instead of adding dedicated protection resistors that would cause continuous power loss, the system performs protection functions by analyzing voltage measurements during normal low-power operation, thereby avoiding excessive energy consumption.
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
Enables effective broken wire detection without additional circuitry, reducing costs and space requirements, and providing a competitive advantage by integrating user-visible fault detection without extra components.
Implementation Method 1
a first switch coupled to a first resistor divider and a first output that supplies a DC supply voltage to reduce a first voltage of the first output down to a first readback diagnostic output, a second switch coupled to a second resistor divider and a second output that supplies the DC supply voltage to reduce a second voltage of the second output down to a second readback diagnostic output
Implementation Method 2
A resistor and a diode may bias the M-output when a M-switch is OFF
Data Source
Figure 1
Figure 2
Figure 3~6
AI summary
An apparatus is provided for detecting fault conditions in the energy supply of a load. The apparatus comprises a fail-safe input-output (I/O) module circuit and a diagnostic circuit coupled to the fail-safe input-output (I/O) module circuit. The fail-safe inputoutput (I/O) module circuit includes a first switch coupled to a first resistor divider and a first output that supplies a DC supply voltage to the load via a first wiring to reduce a first voltage of the first output down to a first readback diagnostic output and a second switch coupled to a second resistor divider and a second output that supplies the DC supply voltage to the load via a second wiring to reduce a second voltage of the second output down to a second readback diagnostic output. The diagnostic circuit is to provide a first readback measurement signal from the first readback diagnostic output and provide a second readback measurement signal from the second readback diagnostic output. The apparatus is configured to provide the first readback measurement signal and the second readback measurement signal for the first output and the second output with and without the load such that when the first and second switches are open or OFF the first voltage at the first output with the load and the second voltage at the second output with the load indicate a NOT broken wire condition with respect to the first and second wirings while the first voltage at the first output without the load and the second voltage at the second output without the load indicate a broken wire condition with respect to the first and second wirings.