Patent ID: 6100675
Filing Date: 2000-08-08
Classification: H02M

Abstract:
A switching regulator comprising:a first reference voltage circuit for producing a first reference voltage;an error amplifier for receiving the first reference voltage and a divided portion of an output voltage of the switching regulator and for amplifying a difference in voltage levels therebetween;an oscillator circuit for outputting a first oscillator signal having a first oscillation frequency and a second oscillator signal having a second oscillation frequency higher than the first oscillation frequency, the first and second oscillator signals each comprising a periodic signal having a first portion for turning on a switching element of the switching regulator and a second portion for turning off the switching element;a PWM comparator for comparing an output voltage of the error amplifier with the oscillator signal output by the oscillator circuit;a second reference voltage circuit for producing a second reference voltage having a level set between an absolute value of a maximum amplitude and a minimum amplitude of the oscillator signal;a second comparator for comparing the second reference voltage with a voltage output by the error amplifier; andan oscillation frequency control circuit for controlling the oscillator circuit in response to an output of the second comparator so that when the output voltage of the error amplifier is lower than the second reference voltage, the first oscillator signal having the first oscillation frequency is output by the oscillator circuit, whereas when the output voltage of the error amplifier is higher than the second reference voltage, the second oscillator signal having the second oscillation frequency is output by the oscillator circuit, such that the first and second portions of the periodic signal output by the oscillator circuit are varied to vary the efficiency of the switching regulator based upon load conditions.