| 摘要 |
PROBLEM TO BE SOLVED: To provide a discharge lamp lighting device which has a simply structured circuit, a small size, and no cost increase, and stably lights a discharge lamp even if it is used in a dark condition or in the last stage of its life. SOLUTION: This discharge lamp lighting device is equipped with: a constant voltage circuit 12 having first and second resistances R14, R15 connected in series between output terminals to divide an output voltage; a third resistance R12 one end of which is connected to the connection point of the first and second resistances; a first switching element Q11 connected to the other end of the third resistance; a step-up transformer 14 in which the output voltage is supplied to a primary coil and a discharge lamp is connected to a secondary coil; a fourth resistance R13 to detect a current passing through the discharge lamp; a second switching element Q12 turned on by a current passing through the fourth resistance R13; and a push-pull circuit 13 to impress mutually opposite phase pulses to both ends of the primary coil of the step-up transformer. When a lighting switch is switched on, the first switching element Q11 is turned on, and when the second transistor Q12 is turned on, the first switching element Q11 is turned off. COPYRIGHT: (C)2005,JPO&NCIPI |
