SWITCHING POWER SUPPLY CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a switching power supply circuit having a small overshoot voltage at constant voltage output use, capable of properly functioning for light-emitting diode driving use.SOLUTION: A switching power supply circuit includes: a switching element MP1; an error amplifier AMP1; a first soft start circuit 3A for outputting a voltage V2 which gradually increases at start-up; a comparator COMP2 for comparing either the output voltage V2 of the first soft start circuit 3A or an error voltage V1 whichever lower and a triangular wave voltage; a driver circuit 1 for controlling conduction/shut off of the switching element MP1 according to a comparison result of the first comparator COMP2; and a second soft start circuit 3B for gradually increasing a reference voltage VREF from VREFS to a second voltage value as its target when the output voltage V2 of the first soft start circuit 3A reaches at VTH.