| 摘要 |
PURPOSE:To prevent an overcurrent between a main electrode and auxiliary electrode at starting by connecting current-limiting impedance to a main electrode of one side of a luminescent tube and shorting it by a heat-responce moving part at stabilized condition. CONSTITUTION:A luminescent tube 31 which builds in main electrodes 32, 33 and an auxiliary electrode 42 is installed inside a outer tube 53, and a current-limiting resistance 40 connected to the main electrode 32, and a bimetal switch A which acts as a heat-responce element connected to the auxiliary electrode 42 are provided, and connected to a power supply 63 through a stabilizer 62. At starting, by opening the contacts 59, 60 of the switch A, main discharge is conducted, and at that time, the current is limited with the resistance 40. At stabilized condition, the contacts 55-58 of the switch A are closed to short the resistance 40. Therefore, unnecessary increase of the temperature of the electrode 32 caused by an overcurrent at starting can be prevented and reliability can be improved. |
