CONTROL CIRCUIT FOR SWITCHING POWER SUPPLY DEVICE AND SWITCHING POWER SUPPLY

摘要

Provided are a control circuit for a switching power supply device and a switching power supply which enable fluctuations due to an input voltage of a switching element at a peak current to be prevented, even if an oscillator with a function for modulating a frequency in a modulation period (idle period) to an oscillation waveform is used. A control integrated circuit (IC) (8): is connected to a switching element in which an output voltage is supplied from an AC input, and a current sensing resistor that converts a current value to a voltage; and switches the switching element on and off. The control IC (8) is composed of: an OCP comparator (45) that detects an overcurrent with respect to a load by means of the current sensing resistor; an overcurrent level setting circuit (50) that compensates for fluctuations produced by peak currents in the switching element according to the output voltage from the AC input; an oscillator (34) with a frequency modulation function, which is capable of modulating a switching frequency for the switching element; and a slope compensation circuit (35) that generates a slope compensation signal that makes monotonic increases in proportion to the time from the start in each cycle of an oscillation signal of the oscillator (34).