Patent attributes
Control circuit and method for controlling a switching power supply, which regulates its output voltage using pulse-width modulation (PWM) that switches on and off a main switch with a PWM signal (VCONT) at an adjusted ON-period ratio of the main switch. The control circuit includes an error signal amplifier circuit that compares the output voltage with a reference voltage and outputs an error signal VE based on the comparison. The control circuit also includes an ON-period adjusting circuit that starts generating a PWM signal (VCONT) in every cycle based on a pulse VPULSE, the period thereof being fixed, and adjusts the HIGH-period of the PWM signal (VCONT) based on the output voltage of the error signal VE. As a result, the control circuit widens the HIGH-period ratio range or the LOW-period ratio range of the PWM signal greatly.
