Abstract: The present invention relates to an apparatus and a method for saving electric power in a display system in which, when the display system is turned to an off mode, a total electric power consumption is reduced to a range for the display system to be operated through a reduction of an on-duty time period of a PWM pulse by using a charging/discharging device of a large capacitance. The present invention provides an ultra electric power-saving mode for a display system when the display system is turned into an off mode with no input of the horizontal and vertical synchronization signals from a video card of the computer main body to the display system. It accomplishes this by reducing the total electric power consumption by approximately half compared to the existing off mode performance through a remarkable reduction of the on-duty time of a PWM pulse to a range of supplying an operational voltage of the microcomputer with the use of a charging/discharging device of large capacitance.