Isolated I/O Output Circuit With Per-Terminal Current Limiting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Industrial output modules lack electrical isolation between terminals, leading to potential damage from high current spikes, which can cause unintended shut-downs and unsafe operating conditions due to conductive paths established when multiple terminals are driven in tandem.
Innovation Solution
The output module incorporates a transformer for electrical isolation between each terminal and a current limiting circuit to prevent voltage drops that could disable the control circuit, ensuring the control circuit remains active during high current draws and monitors current flow to detect short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple output terminals are driven in tandem without electrical isolation, then the output module can control multiple devices simultaneously, but high current spikes at one terminal can damage other terminals through conductive paths
Solution Approach 1:
The patent divides the output module into electrically isolated segments by placing an isolation transformer between the power supply and each output terminal. This segmentation ensures that a high current spike at one terminal remains confined to that terminal's segment and cannot propagate to other terminals through conductive paths, thus maintaining reliability while allowing multiple terminals to operate simultaneously.
Solution Approach 2:
The isolation transformer acts as an intermediary component between the power supply and each output terminal. It provides galvanic isolation, blocking the direct conductive path that would allow current spikes to propagate between terminals, while still enabling power transfer and control signal transmission to each terminal independently.
2Reliability
If isolation transformers are added between power supply and each output terminal, then electrical isolation and protection against current spikes are achieved, but the device complexity and cost increase
Solution Approach 1:
While segmentation into isolated terminals is necessary for reliability, the patent manages the complexity by providing control circuitry that can monitor and manage each isolated terminal. The modular nature of the segmentation allows for standardized designs that can reduce overall system complexity through repetition of proven units.
Solution Approach 2:
The control circuitry monitors the status of each isolated terminal and provides feedback to manage the isolated segments efficiently. This feedback mechanism allows the system to adapt to the presence of multiple isolation transformers, optimizing their operation and reducing the practical complexity of managing multiple isolated channels.
3Reliability
If current limiting circuitry is added to each isolated terminal, then control circuit stability is maintained during high current draws, but the device complexity increases
Solution Approach 1:
The current limiting circuitry is configured to activate automatically when high current conditions are detected at any terminal. This preliminary protective action prevents voltage drops that would otherwise destabilize the control circuit, maintaining stability without requiring continuous active management or complex control logic.
Solution Approach 2:
Each isolated terminal's current limiting circuitry operates autonomously to protect the control circuit. The distributed nature of the current limiting functionality allows each terminal to self-regulate its current draw, reducing the need for complex centralized control and simplifying the overall system 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
This solution prevents damage to other devices by isolating current spikes, maintaining power supply integrity, and reducing the risk of high-frequency oscillations, while enabling safe operation and fault reporting to the industrial controller.
Implementation Method 1
An output circuit for an output module used in an industrial controller includes, for each of a plurality of output terminals, an isolation circuit having an input and an output. The isolation circuit is configured to receive power from a power source at the input and to provide electrically isolated power from an output of the isolation circuit to the corresponding output terminal.
Implementation Method 2
A current limit circuit is provided between the isolated side of the transformer and the output terminal to prevent the voltage level output from the transformer from dropping enough to disable the control circuit.
Data Source
AI summary
An output module for an industrial controller provides electrical isolation between each of the output terminals in the module. The output module receives control signals from the industrial controller indicating a desired output state for each of the output terminals and selectively connects power from the output of the electrical isolation to the output terminal. During normal operation, a switching device connects the power to the output terminal responsive to the control signal. A current sensor monitors the current conducted at the output terminal. If the current exceeds a predefined threshold, a current limit circuit clamps the current being output at the terminal. A control circuit may allow the output terminal to ride through a temporary spike in current or disable the output terminal if a fault condition is detected.