| 摘要 |
PROBLEM TO BE SOLVED: To improve a power factor without the use of a multiplier for a reduction in price. SOLUTION: A trigger signal having a constant period is outputted from a control circuit 42 to an OR gate 43, and thus the switching period of a transistor Q1 is fixed. A differential amplified signal is outputted from an operational amplifier OP1, and is inputted to the negative terminal of a comparator COMP1. The drain current ID of the transistor Q1 is detected by a resistor R1. A signal V6 obtained by adding a slope compensation signal (V5) to a drain current detection signal (V4) is inputted to the positive terminal of the comparator COMP1, and the duty of the transistor Q1 is determined with a timing with which a signal V7 outputted from the comparator COMP1 is brought to high.
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