| 摘要 |
PURPOSE:To take the luminance balance of first and second light emitting parts, by mounting a rheostatic signal generating means, a means for supplying a pulse to first and second light emitting parts and changing the duty ratio of the pulse when a rheostatic signal is inputted to perform extinction driving and a means for converting the driving voltage of the first light emitting part to low voltage. CONSTITUTION:When a night switch 1 is closed, an oscillation circuit 2 receives a rheostatic signal to oscillate an extinction signal and a fluorescent display tube driving IC4 modulates the voltage of the bluish green segment 5a of a fluorescent display tube 5 to a constant extinction ratio to reduce a lighting time T1. An element Tr1 is turned ON in a circuit 6 and a Zener element ZD prescribes driving voltage to V3<V2 to apply the same to a color segment 5b and the change in the extinction ratio due to the delay of elements Tr3, Tr4 is corrected by the element ZD and the luminance of a bluish green light emitting part 5a can be allowed to be well-balanced with that of the other color light emitting part 5b. The relation between V2 and V3 is set from the relation of the delay of the elements Tr3, Tr4, the luminances of the pieces 5a, 5b and driving voltage.
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