Display device and method for controlling panel self refresh operation thereof

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, wherein, for an input still image, the source unit applies power to a frame buffer of the sink unit and transmits the still image to the sink unit, wherein the sink unit determines whether the still image can be losslessly compressed and stored in the frame buffer, outputs a first control signal if the still image can be losslessly compressed and stored in the frame buffer, and outputs a second control signal if the still image cannot be losslessly compressed and stored, and wherein the source unit activates the PSR mode for the first control signal, and deactivates the PSR mode for the second control signal.