To provide a circuit around a power source which makes a controller recognize abnormality in case that an abnormality detecting circuit other than a voltage abnormality detecting circuit detects the abnormality before starting or after stopping the power circuit.

A DC power unit includes a circuit (14) around a pwer source, which includes the voltage abnormality detecting circuit (12) that detects whether the voltage output from a DC power circuit (11) is in a prescribed voltage range or not and an abnormality detecting circuit (13) that detects abnormality other than the voltage, and which is structurized to output a signal, where a logical sum of the output of the voltage abnormality detecting circuit and the output of the abnormality detecting circuit is taken, to the controller. In the DC power unit, the circuit around the power source includes a terminal (15), into which a simulated voltage for substituting for the output voltage from the power circuit is input, and it is structurized so that the simulated voltage input into the terminal may be applied to the input terminal of the voltage abnormality detecting circuit via a rectifying device or a switching element.