PLC Restart Control With Capacitor Charge Check for Safe Shutdown
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Solution Overview
Problem
Existing PLC systems face issues with executing a proper backup operation during a restart process when power is shut down again due to insufficient charge in the capacitor, leading to incomplete data storage and potential device damage.
Innovation Solution
A control device and method that includes a power shutdown detection part, a power supply holding part, and a power detection part to ensure the restart process is executed only when the power supply holding part has a power amount equal to or greater than a reference amount, set based on the necessary power for the termination process, and after a backup process has been completed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the restart process is executed immediately after power supply returns during backup operation, then the system can quickly resume normal operation, but the capacitor may not have sufficient charge to complete the termination process if power shuts down again
Solution Approach 1:
The system checks the charge state of the capacitor before executing the restart process. If the charge is insufficient, the restart is delayed until the capacitor is fully charged. This preliminary check ensures that when restart occurs, sufficient power is available to complete the termination process even if power shuts down again.
Solution Approach 2:
The system continuously monitors the charge state of the capacitor and uses this feedback information to control the timing of the restart process. The restart is conditioned on the capacitor reaching a sufficient charge level, creating a closed-loop control that adapts to the actual power availability.
2Device complexity
If the capacitor charge level is not monitored before restart, then the control system is simpler, but the termination process cannot be guaranteed to complete if power fails during restart
Solution Approach 1:
A charge detection circuit continuously monitors the capacitor's charge state and provides feedback to the control unit. This feedback mechanism enables the system to make informed decisions about restart timing without significantly increasing overall system complexity.
Solution Approach 2:
The charge detection circuit acts as an intermediary between the capacitor and the control unit, providing processed information about charge state. This intermediary component simplifies the control logic by presenting ready-to-use charge status information rather than requiring the control unit to directly calculate or infer charge levels.
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
Ensures the termination process is executed correctly even if power is shut down again during the restart, preventing data loss and device damage by ensuring sufficient power is available for the termination process.
Implementation Method 1
a capacitor is provided between the second power supply line and the ground as a power supply for the backup operation
Implementation Method 2
The DC/DC converter steps down an input voltage (20-V to 28-V) to 3.3-V, which is the operating voltage of the main circuit
Data Source
AI summary
The disclosure provides a control device and a control method capable of properly executing a termination process even in a case where a power shutdown occurs again during the execution of a restart process. A programmable logic controller includes a central processing unit module, a power shutdown detection part, a power supply holding circuit, and a power detection part. The central processing unit module executes the termination process with the power supplied from the power supply holding circuit in a case where the power shutdown detection part has detected the power shutdown, and the central processing unit module executes a reboot process on condition that the power supply holding circuit holds a power amount equal to or greater than a reference amount based on the power detection part in a case where the power shutdown detection part has detected a return of the power supply from the power shutdown.