In a display device having a light source and a storage for storing at least one reference frame of image data, a driving method includes receiving a current frame of image data; comparing grey levels between pixels of the current frame of image data and the corresponding pixels of the reference frame of image data; determining a pixel quantity of pixels having different grey levels in the current frame of image data and the reference frame of image data; and based on the determined pixel quantity, calculating and outputting a signal controlling a light emitting duty ratio and an amplitude of the light source while displaying the current frame. The display device further has a comparing unit and light source control unit for performing the driving method.