| 摘要 |
PURPOSE:To control so as to hardly show interference fringes on a liquid crystal picture in the case of light-controlling a discharge lamp by frequency control by synchronizing an oscillation signal with the signal of the display circuit of the liquid crystal display device of an equipment loading the discharge lamp. CONSTITUTION:As the oscillation signal supplied to a program counter 8, the signal is used which is the signal of N times as high as a horizontal synchronizing signal supplied from the display circuit 1 and generated by a PLL (phase locked loop) circuit 2, a VCO (voltage control oscillator) 3 and an 1/N frequency divider 4. Where, when the frequency of the horizontal synchronizing frequency is regarded as f, the frequency division ratio of the program counter is M, since the frequency outputted from the program counter becomes (N/M)Xf, by correcting the frequency division ratio M outputted from an A/D converter 6 by a data correction circuit 7 so that N/M does not become an integer, the interference fringes are prevented from stilling on the picture, and hardly are shown. |
