DC conversion apparatus

A DC conversion apparatus comprising:

• a first switch configured to carry out ON/OFF operations via a primary winding of a transformer to convert a DC voltage provided by a DC power source into a high-frequency voltage;
• a series circuit of a second switch and a clamp capacitor, the series circuit being connected to both ends of the primary winding of the transformer or to both ends of the first switch;
• a synchronous rectifying circuit configured to carry out synchronous rectification of a high-frequency voltage generated at a secondary winding of the transformer;
• a smoothing circuit having a smoothing reactor and a smoothing capacitor configured to smooth a rectified output of the synchronous rectifying circuit and outputs a DC voltage;
• a capacitor configured to storage energy being stored in the smoothing reactor and transferred thereto via a diode due to a current backflow of the synchronous rectifying circuit under light load condition;
• a third switch configured to turn ON in synchronization with the second switch and to return the energy stored in the capacitor to the clamp capacitor on the primary side via the transformer;
• and
• a control circuit turning the first switch and the second switch ON/OFF states alternately.