Output stabilization device in case of power supply transient and CPU abnormal operation of safety class PLC

摘要

PURPOSE: A method and a device for stabilizing the output of a PLC(Programmable Logic Controller) in the power transition and malfunction of PLC are provided to secure stabilization and soundness of a nuclear safe system by supplying a fail safe function of a digital/analog output by operating a PLC according to the definition after defining the status of the PLC. CONSTITUTION: A hot swap device(200) increases the power output of a PLC according to the power increase of the PLC if a circuit board is mounted on a safe class PLC. A hardware reset unit(210) generates a hardware reset if the power output of the hot swap device is increased according to the power increase of the PLC. A CPU initializing unit(220) initializes a CPU and resets software. A power fail sensor senses the off of the safe class PLC. A power fail processor(240) inactivates the digital/analog output of the safe class PLC and stores final data operated by the CPU of the safe class PLC in a preset memory. The power fail processor turns off the hardware of the PLC after stopping the operation of the PLC.