| 摘要 |
PROBLEM TO BE SOLVED: To provide a switching power supply circuit that has a power factor improving function, enhances power conversion efficiency, and reduces the number of circuit components. SOLUTION: The switching power supply circuit comprises a power factor improvement circuit 13 that improves the power factor by feeding back a resonance pulse voltage generated in the tertiary winding N3 of a resonance converter to a primary-side smoothing capacitor Ci. A power factor improvement inductor Lo and a capacitor CNL of the power factor improvement circuit 13 are arranged at the input side of a primary-side rectifying element Di. The capacitor CNL of the power factor improvement circuit functions as an across capacitor, too, of a common mode filter, so that good power factor improvement effect can be generated and the improvement of power supply efficiency and the reduction of normal mode noise and common mode noise can be achieved by reducing the number of components. COPYRIGHT: (C)2008,JPO&INPIT
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