DC/DC converter and control method thereof

The present invention provides a DC/DC converter and a control method thereof whereby losses at a light load are reduced. The present invention is characterized by improvements made to a DC/DC converter wherein a main switching device intermittently turns on power from a power supply to the primary winding of a voltage-converting transformer, and an active clamp circuit wherein a capacitor and a sub-switching device are at least series-connected is parallel-connected to the primary winding. The DC/DC converter of the present invention comprises a first controller for turning on and off the main switching device according to the difference between the output voltage of the DC/DC converter and a desired output voltage, and a second controller for turning on the sub-switching device for a desired length of time after the turning off of the main switching device.