| 摘要 |
PROBLEM TO BE SOLVED: To suppress a tube wall temperature from rising when either of plurality of discharge lamp connected in parallel comes to the end of its life, in the case of turning the lamps on. SOLUTION: A high frequency power supply part 1a supplies high frequency power at a time to a plurality of discharge lamps 21 , 22 ,... connected in parallel with one another. If either of the discharge lamps 21 , 22 ,... comes to the end of its life, a lamp end detecting part 3, via an on/off signal generating part 4, causes a control part 5 to perform action corresponding to the end of the life. Then the voltages at both ends of each of the discharge lamps 21 , 22 ,... go into a state in which a first, relatively low voltage and a second, relatively high voltage alternate in a cycle. The first voltage is set to turn off either of the discharge lamps 21 , 22 ,... which is at the end of its life, and the second voltage is set so that it does not turn on again either of the discharge lamps 21 , 22 ,... that is at the end of its life but turn on again the other normal discharge lamps 21 , 22 ,.... |
