A method of power down control (PDC) for a display device is to be implemented by a processor in a power down controller of the display device. The power down controller includes a main system, a main system power source, and a PDC power source. The method includes the steps of: (A) receiving power from the PDC power source, determining if the main system is to be activated, and proceeding to step (B) if affirmative; (B) turning on the main system power source, and activating the main system; (C) determining if operation in a power down mode is intended, and proceeding to step (D) if affirmative; and (D) turning off the main system power source to operate in the power down mode.