Power-saving circuit for an AC/DC adaptor for a portable computer

摘要

A power saving circuit of an AC/DC adaptor for a portable computer including an input until converting an AC voltage into a DC voltage; a power transistor; a transformer inputting the DC voltage and inducing an AC voltage based on the state of the power transistor; an output unit converting the AC voltage into a DC voltage; a feedback unit producing a feedback voltage based on an output voltage of the output unit; a driver outputting a PWM control signal to the power transistor based on the feedback voltage; an output load sensor outputting a sensing signal if a sensed load of the output unit is below a predetermined level; an output voltage dropping unit dropping an output voltage of the output unit based on the sensed signal; and a switching frequency reducer reducing a switching frequency of the PWM control signal based on the sensing signal.