| 摘要 |
PURPOSE:To eliminate the need for a frequency multiplying circuit in a circuit by shaping the output waveform of an oscillator or the waveform of an external input signal, and counting it by a counter and generating horizontal synchronizing signal blanking pulses. CONSTITUTION:A video signal inputted to a video signal input terminal 1 is inputted to a synchronizing signal separator circuit 2, whose output is further inputted to a horizontal synchronous separator circuit 3, where only the horizontal synchronizing signal(HD) is separated and extracted. Then, this signal is inputted to a reset pulse generating circuit 13. A high frequency signal outputted by the oscillator 14 is inputted to a waveform shaping circuit 15 for waveform shaping and then inputted to the counter 10, which generates a horizontal synchronizing blanking pulse on counting up to the best number for the horizontal synchronizing blocking pulse. Here, the reset pulse generated by a reset pulse generating circuit 13 is inputted to the reset terminal 11 of the counter 10 to determine the timing of the start of the counting operation.
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