| 摘要 |
PURPOSE:To enable sure start-up lighting of every discharge lamps by providing a balast circuit for start-up lighting, a circuit for detecting voltage at both ends of individual discharge lamp, an OR circuit for selecting the maximum value in the voltages, a circuit for controlling high frequency power supply to level the output voltages of the OR circuit. CONSTITUTION:A high voltage is generated at both ends of individual discharge lamp 3a-3c due to LC oscillation of respective balast circuits 4a-4c before start-up, however, there is sometimes no start-up lighting when the voltage is below the level of start-up. The voltages at both ends of the lamps 3a-3c are respectively detected, at this time, by means of voltage detection circuits 5a-5c, and the maximum value in the levels is selected by means of an OR circuit 6. The lamp, e.g., 3a, is started up and lighted by means of controlling operation of a high frequency power supply 1 by the use of a control circuit 7, and thereby the voltages at both ends are decreased. Similar operation is repeated for the other lamps 3b, 3c not lighted, and then sufficient secondary voltages are respectively supplied thereto. It is thus possible to perform start-up lighting. |
