| 摘要 |
PURPOSE: To constitute the driving circuit for an LED printing head in such a manner that the quantity of light from LED changes at a specified ratio to a control signal which controls the quantity of light from LED, and thereby achieve the smooth adjustment of the quality of light, when adjusting the quantity of light from LFD. CONSTITUTION: A 9-bit digital signal is converted to an analog control signal by a D/A converter 16. This control signal is compressed as specified using a compression circuit 14, into a compression control signal, which is, in turn, supplied to a subtraction circuit 10. In addition, the compression control signal is subtracted from a reference voltage in the subtraction circuit 10, and the obtained result is output as a gate voltage VG. On the other hand, a detection means 22, monitoring the magnitude of the gate voltage VG, detects the magnitude, based on which a switching means 18 changes the compression ratio of the compression circuit 14. Thus it is possible to make the variation rate of the gate voltage VG constant to the change of the control signal. |
