A method of controlling a dimming operation is disclosed. In one aspect, the method includes determining the brightness of an input image frame based on input image data, determining an input dimming value based on the brightness of the input image frame, selectively performing the dimming operation is based on a comparison of an absolute value of a difference between the input dimming value and a current output dimming value against a predetermined threshold value, where a value generated by adjusting the current output dimming value by a predetermined adjustment value is output as a next output dimming value when performing the dimming operation, and the input dimming value is output as the next output dimming value when not performing the dimming operation.