| 摘要 |
The present invention includes: a series circuit connected to a junction of a first switch element and a second switch element connected in series across ends of a DC power supply, and to one end of the DC power supply, and formed of a primary winding of a transformer and a capacitor; a rectifier/smoothing circuit configured to rectify and smooth a voltage generated in a secondary winding of the transformer thereby to extract a DC voltage; a control circuit configured to alternately turn on and off the first switch element and the second switch element; a voltage detector configured to detect a voltage of the DC power supply; and a duty controller configured to, under a light-load condition, set a duty ratio between the first switch element and the second switch element closer to 50% as a value of the voltage detected by the voltage detector becomes larger. |
