A control circuit is provided for a separately excited DC/DC converter which directly monitors output voltage to detect a short-circuit state, and performs overcurrent protection. A switching controller of the control circuit controls a switching operation of a switching transistor of the separately excited DC/DC converter. A voltage comparator compares the output voltage and a threshold voltage, to detect the short-circuit state. After a predetermined start-up time has elapsed after beginning start-up of the separately excited DC/DC converter, when the voltage comparator detects the short-circuit state, the switching controller halts the switching operation of the switching transistor, and makes detection of the short-circuit state by the voltage comparator non-operative before elapse of the start-up time. After detecting the short-circuit state and halting the switching operation of the switching transistor for a predetermined halt time, the switching controller begins start-up of the separately excited DC/DC converter once again.