To provide a switching power supply apparatus which never oscillates even if an input voltage is high and load is low.
In the switching power supply apparatus, a switching element (14) switches an input voltage (VIN) to convert the voltage into an AC voltage, a transformer (13) steps up or down the voltage, and then, the voltage is rectified and converted into an output voltage (VOUT). In the apparatus, an error amplifier (25) generates an error signal (B) from the output voltage, a sawtooth wave generator (28B) generates a sawtooth wave (D), a voltage comparator (27) compares the error signal with the sawtooth wave to output a pulse-modulated control signal (C), and the switching element is turned on/off by the control signal. The sawtooth generator (28B) generates a sawtooth wave (D) in which the smaller the pulse width of the pulse width-modulated control signal (C) is, the lower the control sensitivity is.
SATO AKIRA
NAGAI TOMIYUKI
