| 摘要 |
PROBLEM TO BE SOLVED: To make output voltage Vout constant regardless of the difference in input voltage Vin. SOLUTION: In a switching power unit 1 of such a type that it performs the control of output voltage Vout by the switching action of a main switch element Q, a control circuit 18 performs the switching control of a main switch element Q so as to stabilize the output voltage Vout, based on the detected voltage of the output voltage detected indirectly by an output voltage detecting circuit 10. Though there must cause difference in the detected voltage of the output voltage detecting circuit 10 by the difference of input voltage Vin in spite of the same output voltage Vout, resulting from the difference of properties between the rectifying elements 5 and 6 of a secondary output circuit 3 and the rectifying elements 11 and 12 of the output voltage detecting circuit 10, this power unit adjusts the ratio of the current flowing to a diode 11 on the side of rectification during ON period of the main switch element Q to the current flowing to a diode 12 on the side of commutation during OFF period of the main switch element Q, making use of a resistor R1, etc. so as to prevent it. COPYRIGHT: (C)2004,JPO
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