| 摘要 |
PROBLEM TO BE SOLVED: To obtain a discharge lamp lighting device capable of properly controlling light quantity of an external electrode type discharge lamp. SOLUTION: In this discharge lamp lighting device, a positive-polarity lamp current flowing through a discharge lamp 5 charges a capacitor C3, while the positive-polarity lamp current is not detected. A negative-polarity lamp current having the same polarity as a negative pulse direction flowing from a secondary winding Tr1b is inputted to an 11th terminal of an IC chip 12 through a diode D1, a resistor R6 and a diode D2. Only the negative-polarity lamp current is controlled but the positive-polarity lamp current is not controlled. Because the positive-polarity lamp current is not effective in a change in light quantity of the discharge lamp 5, the positive-polarity lamp current is not detected. Only the negative-polarity lamp current is detected and controlled, so that only the negative-polarity lamp current is changed to properly control the light quantity of the discharge lamp 5. |
