| 摘要 |
PROBLEM TO BE SOLVED: To make the control of electric current possible with a relatively simple structure for each of light emitting diodes in a time division drive circuit for light sources for an optical printer or the like having a plurality of light emitting diodes as its light sources by a method wherein a single comparison circuit is used and each of the light emitting diodes is controlled with comparison with reference value for each of lighted color. SOLUTION: A multiple LED time division drive circuit is provided at a line scan-type optical printer that forms color images with lights from each of LEDs for RGB made line-shaped and with a photosensitive paper exposed to the light at specified timing. The circuit is constructed in a structure wherein LED drive circuits for colors in red, green and blue are connected in parallel with one another to a position between a terminal Vcc at one side of a single common electric source and an earth. The LED drive circuits are constructed, being equipped respectively with transistors TR1-TR3, digital switches DS-1-DS-3 and the like. Respective cathodes of the LEDs (LED-R, LED-G and LED-B) are connected to a comparator COM, and TR's are driven in accordance with comparison with reference voltage REF for respective colors and thereby lighting is controlled for each of the LED's. |
