| 摘要 |
PROBLEM TO BE SOLVED: To restrain heat in a plurality of output circuits provided on a secondary of a transformer and reduce the power loss. SOLUTION: A multiple output switching power supply comprises: a constant current circuit (D1, R3, TR4) for extracting a constant current from a pulse voltage excited in a secondary winding M22 of the transformer TRS1 while a transistor TR1 on a primary of the transformer TRS1 is turned on; a capacitor C3 for storing the constant current; a comparator 3 for comparing a saw- tooth voltage V1 generated across the capacitor with an output voltage V2 from an output circuit 20; a pulse width processing circuit (TR2, TR3, R1, R2) to reduce the pulse width excited in the secondary winding M22 based on the result of comparison and make the reduced pulse contribute to the generation of the output voltage; and a discharging circuit (R4, D4) for discharging the charge in the capacitor while the transistor on the primary of the transformer is turned off.
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