| 摘要 |
PROBLEM TO BE SOLVED: To provide a small-sized and lightweight semiconductor integrated circuit device for a switching power supply at a low cost. SOLUTION: This device is constituted of an external resistor R, an external capacitor C, a first constant current circuit 6, a second constant current circuit 7, a PWM comparator 3, and a buffer circuit 4. As a new circuitry, the second constant current circuit 7 is added to a conventional semiconductor integrated circuit device. From the first constant current circuit 6, the smallest current matching a light load is outputted to the external capacitor C. As to an output current from the second constant current circuit 7, an output voltage from a photocoupler 15 which is controlled by a feedback voltage is inputted in the PWM comparator 3 through a feedback terminal FB, and an output of the PWM comparator 3 is inputted in a gate of a MOSFET 11 through a buffer circuit 4, thereby controlling the amplitude of a current of the MOSFET 11.
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