DC-DC converter and control method thereof

A control method of a DC-DC converter including a clamp capacitor having one terminal connected with a ground terminal of a voltage source, a switching circuit including first and second switches connected with each other in series between a positive terminal and the ground terminal of the voltage source and third and fourth switches connected with each other in series between both terminals of the clamp capacitor, and a forward-flyback transformer including a plurality of primary coils connected between a first connection node between the first and second switches and a second connection node between the third and fourth switches, the method comprising;

• turning on, by a controller, the first switch and the fourth switch;
• detecting, by controller, a current flowing into a leak inductance of the forward-flyback transformer;
• turning off, by the controller, the first switch and the fourth switch if the first switch and the fourth switch are turned on and a predetermined time lapses;
• turning on, by the controller, the second switch and the third switch;
• turning off, by the controller, the second switch if the second switch and the third switch are turned on and the predetermined time lapses;
• and
• turning off, by the controller, the third switch if the second switch is turned off and the predetermined time lapses,
• wherein the turning off of the second switch includes turning off the second switch if the current flowing into the leak inductance is 0.