| 摘要 |
PROBLEM TO BE SOLVED: To meet demands for noise reduction in a switching power supply unit wherein the improvement of power factor is feasible. SOLUTION: A rectifying circuit 4 is connected with a smoothing capacitor Cdc through an inductor L1, a diode D5 for reverse current prevention, and the first part N1a of the primary winding N1 of a transformer 5. A series circuit of the primary winding N1 of the transformer 5 and a switch Q1 is connected in parallel with the capacitor Cdc. The secondary winding N2 of the transformer 5 is connected with a rectifying and smoothing circuit 6. A capacitor C1 for bypassing is connected between the output terminals 4c and 4 of the rectifying circuit 4. A capacitor C2 for high-frequency component removal is connected in parallel with a series circuit of the diode D5 for reverse current prevention, the second part N1b of the primary winding N1, and the switch Q1.
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