| 摘要 |
PROBLEM TO BE SOLVED: To stop the operation of a lighting circuit for a fluorescent light emitting tube at an early stage when the tube has come into its final period of lifetime. SOLUTION: In a base member 11b, a base board 15a is installed in such a way as covering approx. the whole end face on electrode side of a fluorescent light emitting tube 14, and switch elements SN and SP for a lighting circuit 15 are installed in positions to cause their destruction by a temp. rise of the electrode of the tube 14 in its final period of lifetime through generation of high frequency waves to operate the tube 14. When half-wave discharge etc., has occurred in the final period of tube lifetime, the lighting voltage impressed on the tube 14 is increased to cause a rise of the electrode temp., which heats the switch elements SN and SP and destroy them, and thereby the operation of the lighting circuit 15 is stopped to preclude any thermal disorder in the final period of the lifetime. |
