To provide a power unit for a light emissive display, achieving a reduction in temperature of a contact current drive circuit for drivingly controlling the light emissive display, while avoiding the improvement of a heat radiation system and decreases in light emissive functions.

A constant current drive circuit 2 arranged in proximity to a light emissive display 1 drives the light emissive display 1 at a constant current to inhibit the fluctuation of the brightness thereof. A power circuit 3 adjusts, according to the drop of voltage of the light emissive display 1, a source voltage applied to the constant current drive circuit 2. Therefore, heating of the constant current drive circuit 2 for driving the light emissive display 1 at the constant current can be reduced, particularly when the drop of voltage of the light emissive display 1 is small, without further improvements of a heat radiation system around the light emissive display 1 which are not easy because of space and structural limitations and without limitations on the light emissive functions of the light emissive display 1.