Provided is a DC/DC converter which has a full bridge configured in a switching unit and uses a half bridge, which is subordinate to the full bridge in view of circuit configuration, to automatically select such one of the multi-topologies. More particularly, the DC/DC converter uses multi-topologies, which receives, in real time, feedback of an output voltage charged to a battery, operates using the half bridge when the output voltage charged to the battery is lower than a reference voltage, and operates using the full bridge when the output voltage charged to the battery is equal to or higher than the reference voltage, so as to output a wider range of voltage.