PWM SWITCHING REGULATOR CONTROL CIRCUIT REDUCING RIPPLE VOLTAGE WHILE MAINTAINING OUTPUT VOLTAGE DURING SOFT START

摘要

PURPOSE: A PWM(Pulse Width Modulation) switching regulator control circuit is provided to reduce a ripple voltage without lowering an output voltage due to a load during a soft start. CONSTITUTION: A PWM switching regulator control circuit having a soft start function includes a reference voltage source(104) generating a reference voltage, a first voltage dividing circuit(101) dividing an output voltage to output a feedback voltage, an error amplifier(108) outputting a difference between the reference voltage and the feedback voltage, a chopping wave oscillating circuit(109) outputting a chopping wave, a PWM comparator(110) comparing the output of the error amplifier and the chopping wave to output a pulse signal, a start-up circuit(111) outputting the pulse signal, a switching circuit(112), a second voltage dividing circuit(102), and a capacitor(103). The switching circuit switches between the pulse signal of the PWM comparator and the pulse signal of the start-up circuit to output the switched pulse signal. The second voltage dividing circuit includes voltage dividing resistors connected in series and a switching element connected in series to the voltage dividing resistors. The capacitor is connected to a connecting point of the voltage dividing resistors of the second voltage dividing circuit.