PURPOSE: To protect a luminant screen by preventing the luminant screen from being burnt when a still picture is continued for a longe time in the luminant screen of a display device such as a cathod-ray or a PDP(plasma display panel).

CONSTITUTION: A video circuit provided with a movement adaptive circuit 1 outputting detection signals on whether video signals are of a moving picture or a still picture, is provided with a counter 2 counting the continuation time of the detection signal when the detection signal is the still picture and outputting a prescribed signal when the continuation time exceeds a prescribed reference time, and a control part 4 controlling a power source on-off relay 6 so as to be made 'OFF' via a transistor 5 when the counter 2 outputs a prescribed signal.