Analog Output Module Cutoff Switching for Accurate Fault Shutdown
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Solution Overview
Problem
Industrial control apparatuses, such as programmable logic controllers, face challenges in accurately controlling analog outputs due to malfunctions like power source and ground short-circuits, which can result in incomplete shutdown of loads and inaccurate voltage monitoring due to the on-resistance of cutoff switches interfering with feedback control.
Innovation Solution
The output module incorporates a controller with malfunction detection units and cutoff switches that isolate the load from power or ground when short-circuits are detected, ensuring accurate monitoring and safe states without the cutoff switches affecting the voltage monitoring path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cutoff switch is used to shut off the load during short-circuit malfunctions, then the load can be disconnected from power or ground, but the on-resistance of the cutoff switch interferes with voltage monitoring and feedback control
Solution Approach 1:
The patent divides the shutdown function into two separate cutoff switches: a first cutoff switch connected between the load and power source, and a second cutoff switch connected between the load and ground. This segmentation allows independent control of power disconnection and ground disconnection, enabling the system to achieve safe shutdown while maintaining voltage monitoring accuracy by selecting the appropriate switch based on the malfunction type.
Solution Approach 2:
The controller acts as an intermediary that detects the type of short-circuit malfunction (power short-circuit or ground short-circuit) and selectively activates the appropriate cutoff switch. This intermediary function ensures that voltage monitoring is not interfered with by the on-resistance of the inactive switch, while still achieving reliable load shutdown.
2Reliability
If the first cutoff switch is placed between the second connection terminal and ground, then ground short-circuit malfunctions can be addressed, but the switch's on-resistance affects voltage monitoring feedback
Solution Approach 1:
The patent segments the protection function into two distinct cutoff switches with different configurations: the first cutoff switch for power short-circuit protection and the second cutoff switch for ground short-circuit protection. This segmentation allows each switch to be optimized for its specific function while the controller manages their coordinated operation to avoid monitoring interference.
Solution Approach 2:
The controller dynamically selects which cutoff switch to activate based on the detected malfunction type. This dynamic control ensures that only the necessary switch is engaged during operation, minimizing the impact of on-resistance on voltage monitoring while maintaining comprehensive protection against both power and ground short-circuits.
3Reliability
If malfunction detection is implemented to identify short-circuit types, then appropriate cutoff switches can be activated, but the system complexity increases
Solution Approach 1:
The controller implements feedback monitoring of the output voltage to detect short-circuit malfunctions. By monitoring voltage levels and patterns, the controller can identify whether a power short-circuit or ground short-circuit has occurred and selectively activate the appropriate cutoff switch. This feedback-based detection method achieves reliable malfunction identification without requiring complex additional detection circuits.
Data Source
AI summary
An output module includes a first connection terminal, a second connection terminal, a power supply terminal, a controller, an output device, and a first cutoff switch. The first connection terminal is connected to a high potential side terminal of an external load. The second connection terminal is connected to a low potential side terminal of the external load. The power supply terminal is provided with an external power supply from an external power source. The output device is configured to operate by receiving a power supply generated by or based on the external power supply and to output an analog voltage or an analog current of a value instructed by the controller toward the first connection terminal. The first cutoff switch is configured to be controlled by the controller to open and close a first path between the second connection terminal and a ground.