Patent ID: 7635969
Filing Date: 2009-12-22
Classification: G05F,H02J,Y02B,Y04S

Abstract:
1. A power supply unit comprising: a first output circuit having capacity of supplying output current of a first level and capable of outputting a predetermined output voltage obtained by regulating a given power supply voltage, a second output circuit having capability of supplying output current of a second level less than said first level and of outputting said predetermined output voltage obtained by regulating said power supply voltage; a reference voltage generation circuit arranged to generate a single reference voltage of a predetermined level; a first error amplification circuit adapted to be controllably enabled or disabled based on a mode control signal and compare a feedback voltage associated with said output voltage with said reference voltage to thereby control said first output circuit such that said feedback voltage is brought to said reference voltage; a second error amplification circuit adapted to be controllably enabled or disabled in the opposite manner with respect to said first error amplification circuit based on said mode control signal and compare said feedback voltage with said reference voltage to thereby control said second output circuit such that said feedback voltage is brought to said reference voltage, said second error amplification circuit operable with less consumption current than said first error amplification circuit; a current detection circuit arranged to detect a detection signal associated with the output current outputted from said first and second output circuits; and a mode control signal generation circuit arranged to generate a current level comparison signal in accord with the predetermined level of said detection signal and, on the basis of said current level comparison signal, generating said mode control signal adapted to switch between the operational mode of said first error amplification circuit and the operational mode of said second error amplification circuit, all of said circuits formed in an IC chip, said current detection circuit including: said mode control signal generation circuit adapted to generate, on the basis of said detection signal, said current level comparison signal having a hysteresis over a region of said output current.