In a switching power source apparatus which outputs a DC output voltage converted
from a DC power source voltage, the DC output, voltage is compared with a reference
voltage to generate a feedback signal which decreases as the DC output voltage
increases. A current detecting signal which decreases as the output current increase
is also generated. The smaller of the feedback signal and the current detecting
signal, as a comparison signal, is compared with a triangular signal in a PWM comparator
to produce a PWM signal. A semiconductor switch is on-off controlled by the PWM
signal. Therefore, the apparatus can perform a constant voltage control with a
current limit function.
