| 摘要 |
PURPOSE:To reproduce an original picture excellent by a small-sized device by setting the oscillation frequency of a voltage-controlled oscillator M times that of sampling clock pulses, and by generating the sampling clock pulses by dividing the frequency of its output by M. CONSTITUTION:A voltage-controlled oscillator 3 oscillates at a higher frequency than a video signal frequency, and the frequency of the output signal of the oscillator 3 is divided by a counter 4; and the output signal of the counter 4 and a horizontal synchronizing signal included in a TV signal are compared mutually by a phase detector 1 to obtain an output signal which corresponds to the phase. The output signal of the detector 1 is supplied via an LPF2 to the oscillator 3 to constitute a phase-locked loop PLL. Further, a counter 7 reset to a constant value with the horizontal synchronizing signal is provided, and this counter 7 divides the frequency of the output signal of the oscillator 3 in the PLL circuit to generate sampling clock pulses 6 of a frequency equal to that of a video signal. |
