| 摘要 |
PROBLEM TO BE SOLVED: To prevent switching operation from being stopped due to abnormal oscillations caused under light load or no load. SOLUTION: A sensor MOS transistor 42, for detecting currents passed through the drain electrode and the source electrode of a power MOS transistor 41, is connected therewith; voltages based on currents passed through the sensor MOS transistor 42 and feedback currents from an auxiliary winding 6 are detected at a detection resistor 47. A control transistor 48 is controlled, by detection voltage produced in the detection resistor 47, and the control transistor 48 controls the power MOS transistor 41; and a resistor for preventing abnormal oscillation is connected between the sensor MOS transistor 42 and the detection resistor 47.
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