| 摘要 |
<p>PROBLEM TO BE SOLVED: To prevent a change in image density. SOLUTION: When a voltage of a source line is detected at the side of a light emitting element driving part 4206 by a voltage detecting part 3, a reference voltage of a reference voltage generating part 107 of a power source part 1 is controlled by the reference voltage controlling part 107 in accordance with a difference of the detected voltage value and a predetermined voltage value. That is, when the voltage detected by the voltage-detecting part 3 is higher than the predetermined voltage, an output of the reference voltage generating part 107 is lowered in accordance with the difference. When the voltage detected by the voltage detecting part 3 is lower than the predetermined voltage, the output of the reference voltage generating part 107 is raised according to the difference. An error amplifier 8 amplifies a differential voltage between the output voltage of the reference voltage generating part 107 and a divided voltage of an emitter voltage by resistors 402 and 403, and controls the output voltage of the power source part 1 according to the obtained differential voltage.</p> |
