| 摘要 |
PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device performing protective operation by detecting disconnection of filaments and a loose contact state as well as the last stage of lifetime of a discharge lamp. SOLUTION: An output transformer T<SB>1</SB>is provided between an inverter circuit 2 and the discharge lamp La, and a lamp lifetime detecting circuit 4 detects the last stage of lifetime of the discharge lamp La by the output of a detecting coil n<SB>3</SB>of the output transformer T<SB>1</SB>. A DC current is allowed to flow to the filaments of the discharge lamp La, and a first filament detecting circuit 5 detects the presence of disconnection of the filaments by the presence of a DC power source. Further, a second filament detecting circuit 6 detects loose contact based on the balance/unbalance of the current flowing to the filaments when the discharge lamp La is lighted. When one of the lamp lifetime detecting circuit 4, first filament detecting circuit 5 and second filament detecting circuit 6 detects abnormality, the inverter circuit 2 is operated at switching frequency in a preheating time. COPYRIGHT: (C)2008,JPO&INPIT |
