A light source device includes a light source module having a light-emitting block, an image analysis part, a duty ratio calculation part, a duty ratio determination part and a signal generation part. The image analysis part extracts representative luminance data of the light-emitting block based on pixel data. The duty ratio calculation part calculates duty ratio data of the light-emitting block based on the representative luminance data. The duty ratio determination part generates determined duty ratio data of the light-emitting block based on the duty ratio data from a first period, and the signal generation part generates a driving signal having a duty ratio corresponding to the determined duty ratio data to drive the light-emitting block.