PURPOSE: To eliminate the waste of power in a projector device driven by a DC power source.

CONSTITUTION: A disconnection detection circuit 12 which detects whether a lamp for back light 4 is disconnected, and a signal detection circuit 13 which detects whether or not a video signal or an audio signal is inputted are provided, and the detected result is transmitted to a power source supply control part 11. Only when the lamp 4 is not disconnected and the video signal or the audio signal is inputted, a power source supply part 11 closes contacts 8, 9 and 10 to permit the supply of power source voltage to the lamp 4, a video circuit 5, and an audio circuit 6 from a battery 3, and when the lamp is disconnected or the signal is not inputted, the contacts 8, 9 and 10 are opened to stop the supply of the power source voltage to the lamp 4, the video circuit 5 and the audio circuit 6 from the battery 3. Thus, the waste of the power consumption, which occurs because the lamp or the circuit part individually continues to act, is eliminated.