| 摘要 |
<P>PROBLEM TO BE SOLVED: To obtain a smooth rising characteristic of an output voltage at soft starting, and to prevent an abrupt rise of the voltage, related to a switching power supply device which feeds a stabilized DC voltage to a load. Ž<P>SOLUTION: The switching power supply device includes: a current mode control circuit which finds an error voltage V2 by entering an output detection voltage V3 and a reference voltage Vr to an error amplifier 23, detects a current I2 flowing via a choke coil L1 and converts the error voltage into a current detection voltage V1, inputs the current detection voltage V1 and the error voltage V2 into a comparator 24 and compares them, and controls an on-period of a switching element Q1 according to a difference between the error voltage V2 and the current detection voltage V1; and a soft start circuit which gradually raises the reference voltage Vr input into the error amplifier 23 at starting. A series circuit composed of a resistor R4 and a capacitor C3 is connected between a terminal of the comparator 24 for entering the current detection voltage V1 and a terminal of the error amplifier 23 for entering the output detection voltage V3. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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