| 摘要 |
PROBLEM TO BE SOLVED: To adjust luminance of display and, also, to perform enhance display by making luminance higher than that of normal display with simple circuit constitution. SOLUTION: A Zener diode ZD1 for applying a cutoff bias to the cathode 66 of a fluorescent display tube is connected between the secondary side winding 67b of a driving transformer 67 to which the cathode is connected and the ground and, moreover, a transistor Tr1 is connected in parallel with the transistor Tr1 between the secondary side winding 67b and the ground. When the transistor Tr1 is turned OFF, a cutoff bias by the set voltage E1 of the Zener diode ZD1 is applied to the cathode 66. When the transistor is turned ON, the interval between the winding 67b and the und is short-circuited and a cutoff bias Ek to be applied to the cathode 66 becomes roughly 0 volt.
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