PURPOSE: To obtain a power interruption detection/output circuit in which power interruption of a DC power supply for a unit, e.g. a controller, is detected and a data stored in a memory of the unit can be subjected to standby processing.

CONSTITUTION: The interruption detection/output circuit for DC power supply comprises a voltage monitoring circuit 2 connected in parallel with a DC power supply 1 in order to detect power supply voltage drop below a predetermined level and to deliver a signal to the outside, a series circuit of a diode 3 and a capacitor 4, and a DC/DC converter 5 for receiving the terminal voltage of the capacitor 4 and outputting a predetermined voltage.