Line synchronizing circuit in a picture display device
US4872055A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jan 20, 1988 |
| Grant date | Oct 3, 1989 |
| Priority date | — |
| Expiry date | Jan 20, 2008 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N5/126
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A line sychronizing circuit in a picture display device, has a phase control loop including an oscillator and a phase comparison stage. In order to enlarge the capture range of the control loop, the phase comparison stage is in the form of a phase-frequency detector having a trigger action on edges of pulses applied, the circuit being provided with means for inhibiting the supply of the control signal form the phase-frequency detector during a predetermined period after establishing that the phase difference measured by the phase-frequency detector between the local line-frequency signal and the incoming line synchronizing signal is larger than a predetermined value. In the perdetermined period, the oscillator signal has substantially the same frequency as before establishing that the phase difference measured by the phase frequency detector is larger than the predetermined value. The supply of the control signal is restored during a second predetermined period after the supply of the control signal has been inhibited, and this irrespective of the phase difference between the local line signal and the incoming line synchronizing signal.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.