PLL-based method and apparatus for generating video drive signals from various sync formats
US5502502A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 6, 1995 |
| Grant date | Mar 26, 1996 |
| Priority date | — |
| Expiry date | Mar 6, 2015 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/46
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
Various video signals provide horizontal sync pulses for generating a horizontal drive signal only during a horizontal sync portion and part of the vertical sync portion of a video signal. The invention generates a horizontal drive signal in the absence of horizontal sync pulses through the use of a phase locked loop (PLL) connected in feedback to horizontal counter logic. The counter logic receives pulses from the phase locked loop and at a predetermined count generates a horizontal drive signal. During the horizontal sync portion of the video drive signal, the frequency of the phase locked loop is determined by a time difference between a second signal derived directly from a horizontal sync pulse and a first signal generated by a predetermined count. The horizontal drive signal is thus synchronized to the horizontal sync pulses. During the vertical sync portion of the video signal, when horizontal Sync pulses may be absent, a vertical counter logic generates a vertical gating pulse that selects between the horizontal sync pulse and a delayed version of the first signal as the second signal to the PLL. The time difference between the first and second signals is approximately the …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.