| 摘要 |
PROBLEM TO BE SOLVED: To turn on a cold cathode fluorescent lamp at high efficiency using simple circuit constitution by stepping up a voltage to a first high ac voltage at the start of lighting of the cold cathode fluorescent lamp, and stepping up it to a second high ac voltage at the time of steady-state lighting. SOLUTION: When a cold cathode flluorescent lamp is started to turn on, a switching circuit 26 is connected to a contact 26B to change the step-up ratio of a high voltage transformer T24 to that corresponding to the start of lighting, and a dc constant voltage from a constant voltage power supply 21 is produced into an ac voltage by first and second coils TL1A, TL1B on the primary side of the primary coil TL11 of the high voltage transformer T24 through the action of a switching circuit part 25 and is stepped up by a secondary coil TL3 to the required minimum high ac voltage for starting lighting, which is then supplied to the cold cathode fluorescent lamp 23. For steady-state lighting, the switching circuit 26 is connected to a contact 26A to change the step-up ratio of the high voltage transformer T24 to that corresponding to steady-state lighting, and the minimum high ac voltage required for steady-state lighting and being lower than that for the start of lighting is supplied. |
