| 摘要 |
PROBLEM TO BE SOLVED: To modulate light in a wide modulating range even though an electrode having a structure equipped with a large electrode and a small electrode is used. SOLUTION: This low-pressure discharge lamp La is equipped with a series circuit of a large electrode 1 and a small electrode having different heat capacities. An inverter circuit INV can adjust a power supplied to the low voltage discharge lamp La, and is connected to the large electrode 1 side. A lamp current of the low voltage discharge lamp La is detected as a terminal voltage of a resistance R, and a detecting circuit SN controls switch elements S1, S2 connected in parallel with the large electrode 1 and the small electrode respectively. When the lamp current is small, the switch element S1 is turned on, and when it is big, the switch element S2 is turned on. |
