| 摘要 |
PURPOSE:To activate without fail even at the time of generating drop-out by controlling the output signal of a synchronizing signal separating circuit with the output signal of a level comparator. CONSTITUTION:Since a drop-out detecting circuit 15 has a threshold voltage, a level detector 17 outputs a drop-out pulse which is shown in Fig.(e). The influence of a drop-out to a synchronizing signal separating level in Fig.(b) is obtained as a control signal, so as not to be outputted only in the interval of the Fig.(e), and by inputting a signal (e) into a synchronizing signal separating circuit 13, a synchronizing signal as a Fig.(f) is separated and outputted to a output edge 14. Here, at the time of an electric power rising, the drop-out detecting circuit 15 considers it as the long drop-out. At this time, since a differentiating circuit 16, a reference voltage source 18 and a level comparator 17 control the long drop-out pulse with a prescribed length, a clamp pulse is surely generated and a clamp action comes to be secure.
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