| 摘要 |
PROBLEM TO BE SOLVED: To provide a flyback-type switching power-supply device that allows easily reducing load fluctuation without using a photocoupler for controlling an output voltage.SOLUTION: An output voltage detection circuit 38 includes: an auxiliary rectifier switch 40 rectifying a voltage generated in an auxiliary winding 12c in an off period of a main switching element 14; an auxiliary capacitor 26b generating an auxiliary voltage Vo1 by smoothing a rectified voltage outputted from the auxiliary rectifier switch 40; and an auxiliary-rectifier-switch drive circuit turning on and off the auxiliary rectifier switch 40. The auxiliary-rectifier-switch drive circuit turns on the auxiliary rectifier switch 40 until an output rectifier element 18 is turned off after attenuating a surge voltage in the auxiliary winding 12c generated by turning off the main switching element 14. A switching control circuit 32 controls on and off of the main switching element 14 so that the auxiliary voltage Vo1 approaches a target voltage. |
