| 摘要 |
PROBLEM TO BE SOLVED: To reduce turn-on loss of switching elements in light load application, while preventing excessive application of voltage to the elements and incorrect operation of a circuit, in a power source device that reduces output voltage in the light load application.SOLUTION: A feedback winding includes: a CPU 418 that has a winding Nb1, and a winding Nb2 having the number of winding larger than the number of winding of the winding Nb1, and detects a voltage output from a transformer 406; and a transistor 101, a diode 102, and a photo coupler 103 that switch to connect the winding Nb1 to a gate terminal of an FET 404 when the voltage detected by the CPU 418 is a predetermined voltage, and connect the winding Nb2 to the gate terminal when the voltage detected by the CPU 418 is lower than the predetermined voltage. |
