Fault-Tolerant Digital Output Module Overload Protection
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Solution Overview
Problem
Safety control systems, particularly those with digital output modules, face challenges in efficiently detecting and managing overloads to prevent damage from external short circuits and long-term overheating, which can disrupt operations and compromise fault tolerance.
Innovation Solution
A switch for a fault-tolerant digital output module is designed with an output transistor pair for enabling and disabling alternating current, a current limiter, a voltage monitor, and a current monitor, along with an average current monitor, to detect overload conditions through sampling intervals and thresholds, providing multiple layers of protection against overvoltage, excessive current, and persistent heat dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a current limiter is added to clamp output current, then overload protection is improved, but device complexity increases
Solution Approach 1:
The current limiter circuit is nested within the output stage of the digital module, with current sense transistors integrated into the existing output transistor pair structure. This allows overload protection functionality to be embedded without adding separate external protection circuits, thereby limiting the increase in device complexity while maintaining reliability improvement.
2Measurement precision
If voltage and current monitoring is implemented with sampling, then overload detection precision is improved, but use of energy increases
Solution Approach 1:
The voltage monitor and current monitor implement periodic sampling rather than continuous monitoring. The voltage monitor samples at predetermined voltage sampling intervals, and the current monitor samples at predetermined current sampling intervals. This periodic action maintains measurement precision for overload detection while significantly reducing energy consumption compared to continuous monitoring.
3Reliability
If multiple monitoring layers are added for comprehensive protection, then fault tolerance is improved, but device complexity increases
Solution Approach 1:
The voltage monitor, current monitor, and current limiter are merged into an integrated protection system with shared control logic. The monitors use common sampling infrastructure and the protection responses are coordinated through unified control, allowing multiple layers of fault tolerance to be achieved while minimizing the increase in device complexity through functional integration.
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
The solution effectively prevents overload damage by instantaneously limiting current, monitoring voltage and current at high sample rates, and averaging load current to ensure continuous operation and minimize disruption, thereby enhancing fault tolerance and safety in safety control systems.
Implementation Method 1
a current limiter for clamping the output current to a predetermined maximum value
Implementation Method 2
a voltage monitor for monitoring the voltage across the output transistor
Implementation Method 3
a current monitor for monitoring the current through the output transistor
Data Source
AI summary
This invention relates to fault detection in electrical circuits. The invention provides a switch for a fault tolerant digital output module comprising: an output transistor pair for enabling and disabling an alternating output current; and a current limiter for clamping the output current to a predetermined maximum value.