JPS56153884A - Vertical reference pulse generation circuit - Google Patents

Abstract

PURPOSE:To obtain a vertical reference pulse synchronized with a regular vertical synchronizing pulse when transmission distortion is generated in the TV signal due to noise, ghost, etc., by using a color burst signal to obtain the vertical reference pulse. CONSTITUTION:The video signal from input terminal 11 is applied to burst sampling pulse generating circuit 12, and the sampling pulse is applied to phase detector 13, and color burst signal Sb sampled from the signal is output to the output of detector 13. This signal Sb is applied to not only VCO15 of the PLL circuit constitution but also demodulating circuit 14 through phase shifter 18. The output of the PLL cicuits is applied to l frequency divider 17 to generate a clock which is synchronized with the horizontal synchronizing pulse and has a frequency twise as high as the horizontal scanning frequency, and this clock is applied to AND circuit 21 which gates the output of RSFF20, and the output of circuit 21 is applied to 525 frequency divider 32. The logical operation circuit to which the output of RSFF25 is input is controlled by the 512 frequency division output and the 513 frequency division output of frequency divider 22, thereby outputting a vertical reference pulse synchronized with the vertical pulse without using the vertical synchronizing pulse.