| 摘要 |
PROBLEM TO BE SOLVED: To provide a dimmer control method that has good response of light amount of a discharge lamp for a variation and allows invertor of the discharge lamp having lighting current variation due to difference of secondary side inductance, by changing at least one of set input voltage and frequency for only initial constant period during the ON period of a dimmer element. SOLUTION: According to the value of a PWMDUTY resistor 14, for only initial constant period during the ON period of a secondary side transistor Q2, input voltage to an invertor transformer T1 is increased by an input voltage setting means 20. Thereby, the value of peak to peak of current rises, and therefore effective current value increases at an equivalent duty. Even when it is used in a region with low on-duty for initial time of the life, variation of lamp current (light amount of a discharge lamp 4) of the discharge lamp 4 for variation of the on-duty becomes linear. As a result, response of light amount for the variation becomes good, and image quality is improved in a copy machine or the like. |
