| 摘要 |
PROBLEM TO BE SOLVED: To enhance efficiency at light load time by reducing an oscillating frequency, when an output power of a secondary side is light load. SOLUTION: Change in the fly-back voltage of a drive winding 2 of a transformer of a non-control system due to changes in the output power of a winding 5 of the transformer of a control system of the ringing choke converter is detected by a Zener diode 16. A transistor 18 is turned off when the load is light to lengthen the on time of a transistor 6, the off time of a switching element 3 is lengthened to reduce the oscillation frequency so as to reduce the ratio of occupying one cycle of the switching loss of the element 3, and enhance efficiency when the load is light.
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