The DC OK signal indicates whether the power supply’s output meets the manufacturer’s defined operating conditions, with exact thresholds and timing determined by the product documentation.
When the DC OK LED is illuminated, the output voltage is within acceptable limits. If the LED turns off, it may indicate an output voltage drop, overload, short circuit, or power supply fault. Some power supplies also provide a DC OK relay or signal output that can be used to notify a PLC or control system of a power supply fault.