Line synchronization detection circuit
US4945413A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 17, 1989 |
| Grant date | Jul 31, 1990 |
| Priority date | — |
| Expiry date | Feb 17, 2009 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/126
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A detection circuit of a line synchronization signal in a video signal wherein the synchronization signal is sent to a phase locked loop (PLL) comprises a voltage controlled oscillator (8), for supplying a line scanning signal to a display. The following steps are provided: inhibiting the operation of the loop and setting the VCO to its free frequency, in the absence of the line synchronization signal; supplying a detection window in relation with the oscillations of the VCO; and detecting the presence of the synchronization signal in this window for supplying either an enabling signal after the detection of a determined number of synchronization tops, this enabling signal connecting again the VCO in the loop, or an inhibiting signal if the detection is interrupted during the determined number of synchronization tops.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.