| 摘要 |
PURPOSE:To eliminate the change in an amount of light emitted from a cold- cathode fluorescent tube by turning one of transistors always first so that the rising phases of a voltage, which is first applied to the cold-cathode fluorescent tube, are all the same when an oscillation circuit is driven. CONSTITUTION:During a period of time that the output pulse voltage of an oscillator OS1 is positive, the NPN transistor (TR) Q3 is turned on. In response to this, an NPNTRQ2, whose direct current amplification factor and voltage between the emitters are both greater than those of an NPNTRNQ1, is first turned on. The rising phases of the voltage applied to the cold cathode tube FL are all unified positive phase; in spite of the high-speed control of the cold cathode tube FL, the change in an amount of light emitted from the cold cathode tube FL is eliminated. Therefore, when the cold cathode tube FL is used as a light source for a color image scanner, the occurrences of irregular variable densities in a transmitted picture and a color copy can be prevented. |
