| 摘要 |
PURPOSE:To attain the effective operation even to a missing or disturbed reference signal during a specific period by replacing a voltage subject to sample and hold into an output voltage of a phase comaparator circuit for a specific period. CONSTITUTION:When the open/close state of switches SW1-SW4 is as shown in figure, the operating state is that a horizontal synchronizing signal exists normally. The output voltage of a filter 11 is a normal voltage in such a state and the output voltage of the filter 11 is outputted to an output terminal 13 via the switch SW 2 and subjected to sample and hold to the sample and holding circuit 12 via the switch SW 3. In a period v of the vertical synchronizing signal, since each switch is thrown oppositely to the position to that shown in figure, the phase comparison function in the phase comaparator circuit is stopped. On the other hand, when the switch SW 4 is closed, the voltage stored in the sample and holding circuit 12 is outputted to an output terminal 13, a continuous output voltage shown in figure (e) is outputted to the output terminal 13. |
