| 摘要 |
PURPOSE:To aim at the promotion of low cost and miniaturization by detecting abnormal voltage to be generated at time of abnormal lighting of a discharge lamp, from both ends of a switching device, and installing a lamp abnormal time protection network which controls the lamp to come into a state of being turned off. CONSTITUTION:There are provided with a fluorescent lamp 2 to be energized from an AC power source 1, a switching device 3 controlling on-off of the lamp and a lamp abnormal time protection network 4 controlling the lamp to its turn-off state at time of abnormal voltage detection. And, abnormal voltage to be generated at time of abnormal lighting in the discharge lamp 2 is detected from both ends of the switching device 3 parallelly installed with the discharge lamp 2 whereby lamp 2 is controlled to the turn-off state. Consequently, the discharge lamp 2 can be made into the turn-off state at time of the abnormal lighting while reducing the number of parts items of the lamp abnormal time protection network 4. With this constitution, the promotion of low cost and miniaturization in the lamp abnormal time protection network is made attainable. |
