A display device includes a source unit; and a sink unit connected with the source unit via an embedded display port interface for signal transmission between the source and sink units and to enable a panel self refresh (PSR) mode for reducing power consumption; a still image detector that is included in the source unit, and analyzes an input image to detect a still image; a compressor that is included in the source unit and losslessly compresses data of the still image by using a previously stored compression algorithm; and a PSR controller that is included in the source unit, compares a size of the losslessly compressed data with a size of a frame buffer of the sink unit in order to determine whether the data of the still image can be stored in the frame buffer in a losslessly compressed format without loss.