North-south pincushion corrected deflection circuit
US4668897A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 2, 1985 |
| Grant date | May 26, 1987 |
| Priority date | — |
| Expiry date | Apr 2, 2005 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04N3/233
- WIPO fieldAudio-visual technology
- WIPO sectorElectrical engineering
Abstract
A field deflection amplifier generates a field deflection current in a field deflection winding. An LC resonant circuit is coupled to the deflection winding and to an output switching amplifier. A control circuit switches conductive states of the amplifier at a line rate, with a 50% duty cycle, to excite the LC resonant circuit into providing a line rate correction current for the field deflection winding. The control circuit varies the modulation envelope of the field deflection current at a field rate in a generally sawtooth manner to provide north-south pincushion correction. When used in conjunction with raster scanning in a square-planar picture tube, the modulation envelope is nonlinearly waveshaped to take into account the aspherical nature of the picture tube faceplate.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.