| 摘要 |
PROBLEM TO BE SOLVED: To improve efficiency when the load of a DC power supply is light and an output current is less. SOLUTION: In a DC power supply made up of a rectifier circuit 2, which rectifies the fullwave of an AC power supply 1, and a DC/DC converter 3, which converts the rectified output into a given DC voltage to output it, switching elements Q1, Q2 are provided in parallel as a switching element, connected in series to the primary windings L1 of the transformer T1 of the DC/DC converter, which breaks the primary current. Also, the secondary current of the transformer 1 is detected by an current detecting circuit 8. The detected current value is compared with a reference value by a comparing circuit 9, and when it is less than the reference value, an on/off circuit 10 keeps the switching element Q2 as turned off to make it in nonoperating state and thereby, when a load is light and output current value is less, a power loss by switching is reduced to improve efficiency. |
