| 摘要 |
PURPOSE:To prevent a change of color temperature and going out of luminescent color from being generated even when a signal of dimming is changed by suppressing a quick change of tube voltage by a quick change of the dimming signal. CONSTITUTION:In a lighting power feed circuit 2, accelerating voltage is applied between a filament 1b and an accelerating electrode 1c so as to accelerate electrons emitted from the filament 1b. In a filament heating circuit 3, tube voltage between the filament 1b and the accelerating electrode 1c is detected to adjust supply power to the filament 1b in accordance with a high/low level of the tube voltage. The tube voltage of a light radiation electron tube 1 is almost fixedly held by adjusting the supply power to the filament 1b. Relating to the lighting power feed circuit 2, a signal of dimming for adjusting supply power to the light radiation electron tube 1 by a change of voltage is input through a delay circuit 4. The delay circuit 4 limits a change rate of the dimming signal to a fixed value or less. |
