| 摘要 |
PROBLEM TO BE SOLVED: To achieve the lighting of a discharge lamp capable of suppressing influence of output power by fluctuation of ambient temperature. SOLUTION: In order to improve decrease or increase of power for lighting the discharge lamp 15, a thermosensor R6 is used for power regulating resistance to reduce power variation by temperature. The thermosensor R6 has resistance having a positive characteristic, and a resistor R5 and the the thermosensor R6 are connected to the input side of a control circuit 19 for controlling power and to the ground side used for resistively dividing the thermosensor R6, respectively. When temperature rises, the resistance value of the thermosensor R6 is increased and the voltage supplied to the control circuit 19 is increased. When the voltage is increased, the output of the control circuit 19 acts in a direction for extending a period for turning on a transistor Q1 and increasing the output thereof. When the temperature lowers, the resistance value of the thermosensor R6 is decreased and the voltage supplied to the control circuit 19 is dropped. When the voltage is dropped, the output of the control circuit 19 reduces the on-time of the transistor Q1 to drop the output thereof, and controls the value of a D.C. voltage Vd2 output from a first DC/DC conversion circuit 12 to equalize the brightness of the discharge lamp 15. COPYRIGHT: (C)2007,JPO&INPIT |
