PWM CONTROL CIRCUIT AND SWITCHING POWER SUPPLY DEVICE

摘要

Provided is a PWM control circuit in which a square wave signal having a discretionary frequency and duty ratio is input from a terminal (11), a modulation signal is input from a terminal (12), and two modified signals having different timing (phase) are output from terminals (21, 22). A first ramp wave generation circuit (31) generates a first ramp wave that is synchronized with the rising edge of the square wave signal. A second ramp wave generation circuit (32) generates a second ramp wave that is synchronized with the falling edge of the square wave signal. A first comparison circuit (32) generates a first modulated signal by inverting the level in accordance with the result of comparing the first ramp wave and the modulation signal. A second comparison circuit (42) generates a second modulated signal by inverting the level in accordance with the result of comparing the second ramp wave and the modulation signal. As a result, two PWM signals having a phase difference other than 180° are generated, and a quasi-square wave signal having a duty ratio other than 50% is obtained.