A control device is disclosed, the control device configured to control a display module and comprising a judgment module and a storage module, wherein the judgment module is configured to receive a reference voltage and to receive a supply voltage of the display module, and is configured to judge whether the display module is supplied with power or not according to the reference voltage and the supply voltage; and the storage module is connected with the judgment module and is connected with a display screen of the display module, the storage module is configured to store a preset image, and where the display module is supplied with power, the storage module transmits the preset image to the display screen so that the display screen displays the preset image. A control method and a display device are also disclosed.