| 摘要 |
PURPOSE:To avoid scrolling even at a fault by providing a pseudo vertical synchronizing signal generating circuit in which a video signal is inputted to generate a pseudo vertical synchronizing signal, it is superimposed on the said video signal and the result is inputted to a synchronizing signal clamp circuit. CONSTITUTION:A negative peak envelope signal is obtained at an output point of a detection circuit 31 from a video signal inputted to an envelope detection circuit 31 from a an output point of an amplifier circuit 1 and the an inverse amplifier circuit 32 inverts the envelope signal to generate a pseudo vertical synchronizing signal. The pseudo vertical synchronizing signal is inputted to an input point D of a clamp circuit 22 while being superimposed on the video signal from a tuning circuit 21, and a signal being the sum of both the signals above is inputted to the input point D of the clamp circuit 22. A serial signal comprising the pseudo vertical synchronizing signal and a horizontal synchronizing signal is obtained at an output point E of the clamp circuit 22. The clamp circuit 22 clamps the pseudo vertical synchronizing signal obtained from a pseudo vertical synchronizing signal generating circuit 3 to attain vertical synchronizing control and then the vertical synchronization of a TV set is kept stable.
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