Patent ID: 8629665

Claim:
A voltage regulating apparatus comprising: a linear regulation unit comprising a first output stage providing the voltage regulating apparatus with a first output voltage and producing a first partial voltage which is a fraction of the first output voltage; and a first error amplifier coupled to the first output stage and comparing the first partial voltage with a first reference voltage to produce a first error signal; a switching regulation unit comprising a second output stage providing the voltage regulating apparatus with a second output voltage and producing a second partial voltage which is a fraction of the second output voltage; and a PWM unit coupled to the second output stage and producing first and second PWM signals according to the second partial voltage and a second reference voltage; a selection unit coupled to the linear and switching regulation units, receiving the first error signal and the second PWM signal, and outputting a regulating signal which is selected from one of the first error signal and the second PWM signal; a first power transistor coupled to the switching regulation unit and receiving the first PWM signal; and a second power transistor coupled to both the selection unit and the first power transistor, and receiving the regulating signal; wherein a connection point of the first and second power transistors is coupled to the second output stage; and wherein the voltage regulating apparatus can be put either in a linear mode of operation if the first error signal is selected as the regulating signal, or in a switching mode of operation if the second PWM signal is selected as the regulating signal.