| 摘要 |
<p>The sync detection circuit includes a V-sync separator (22) for separating V-sync signals, a counter (42) for counting a predetermined repetition period in relation to each of the V-sync signals and for producing a count-up signal upon counting the predetermined repetition period, and a phase comparator (44) for comparing the phase of the count-up signal with the phase of a V-sync signal and for producing a first level signal, representing the receipt of a standard signal, when the compared signals have the same phase, and a second level signal, representing the receipt of a non-standard signal, when the compared signals have the different phase. The counter also counts a predetermined time period, which is greater than the predetermined repetition period, in relation to the V-sync signal and for producing a time-up signal upon counting the predetermined time period, and a condition detector (38-41) for detecting the signal absent condition when no V-sync signal appears before the time-up signal is produced.</p> |
