| 摘要 |
PURPOSE:To make the voltage across both ends of a discharge lamp constant and keep the brightness constant when the discharge lamp is lighted regardless of the characteristics of components used by providing an oscillating circuit, and operating and controlling a chopper circuit with it. CONSTITUTION:When the voltage of a comparator 30 becomes the prescribed voltage or above, an oscillating circuit 10 is operated, and its output is applied to bases of transistors Tr1, Tr2 of a chopper circuit 20 to operate the chopper circuit 20. High-frequency high voltage is applied across both ends of a discharge lamp 5 from the secondary winding J2 of a step-up transformer 1, and preheating heaters 51, 52 are preheated by preheating windings J51, J52. The feedback voltage from the feedback winding J6 wound on the step-up transformer 1 is fed back to the power source of the oscillating circuit 10 via an automatic voltage adjusting circuit 40 so that the output voltage of the oscillating circuit 10 becomes constant. When the discharge lamp 5 is lighted, the output voltage of the oscillating circuit 10 is invariably made constant, and the brightness of the discharge lamp 5 can be kept constant in time series. |
