Fail-Safe DC Output Circuit for Broken Wire Detection
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Solution Overview
Problem
Existing fault detection systems in industrial control systems, such as programmable logic controllers (PLCs), face challenges in detecting broken wires or missing loads due to the inability to parameterize open-circuit or overload detection and the undesired heat generation caused by measuring resistors in the current path, leading to inefficiencies and increased costs.
Innovation Solution
A fail-safe input-output module circuit with a diagnostic circuit that uses resistor dividers to reduce voltages to readable levels, allowing for the detection of fault conditions by examining voltage levels with and without the load, eliminating the need for additional switches and resistors, thereby determining broken wire conditions without additional circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If measuring resistors are placed in the current path for fault detection, then broken wire detection capability is improved, but heat generation and power loss increase
Solution Approach 1:
The patent extracts the measuring resistor from the main current path and places it only in the diagnostic branch that is activated during fault detection mode. This allows the resistor to be used for measurement purposes without continuously affecting the power consumption during normal operation, thus resolving the contradiction between detection capability and energy loss.
Solution Approach 2:
The patent implements a dynamic switching mechanism that activates the diagnostic circuit with measuring resistor only when fault detection is required. The switch dynamically connects or disconnects the measuring resistor from the circuit based on operational needs, enabling the system to adapt between normal power-efficient operation and diagnostic measurement modes.
2Measurement precision
If additional switches and sense resistors are added for wire break detection, then detection accuracy is improved, but device complexity and cost increase
Solution Approach 1:
The patent designs the output driver circuit to serve multiple functions: it acts as both the main power switching element and the diagnostic measurement element. The same output driver transistors are used for both load control and fault detection, eliminating the need for separate dedicated detection components and reducing overall circuit complexity.
Solution Approach 2:
The patent merges the diagnostic measurement function with the existing output driver circuitry. By combining the load switching function and the fault detection function into a single integrated circuit block, the patent reduces component count and simplifies the overall device architecture while maintaining detection accuracy.
3Device complexity
If integrated output drivers with on-chip detection are used, then device integration is improved, but parameterization capability deteriorates
Solution Approach 1:
The patent incorporates preliminary diagnostic capabilities directly into the output driver circuit design, enabling fault detection functionality to be pre-integrated at the chip level. This preliminary integration maintains high device integration while the configurable nature of the circuit allows for flexible parameterization through software or hardware settings.
Solution Approach 2:
The patent implements configurable threshold values and detection parameters that can be adjusted through software or hardware configuration. This allows the same integrated circuit to adapt to different application requirements by changing operational parameters such as detection thresholds, timing characteristics, and measurement ranges, thereby maintaining both integration and parameterization capability.
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 effectively detects broken wires or missing loads without additional switches or resistors, reducing costs and space requirements while maintaining functional safety, providing a competitive advantage by enabling reliable fault detection without the need for extra components.
Implementation Method 1
Resistors form a first resistor divider to reduce a voltage of a P-output down to a P-Readback. Resistors form a second resistor divider to reduce a voltage of a M-output down to a M-Readback.
Implementation Method 2
A resistor and a diode may bias the M-output when a M-switch is OFF.
Data Source
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 input-output (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.