Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Reexamination Certificate
2000-03-29
2001-07-31
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
C315S395000
Reexamination Certificate
active
06268706
ABSTRACT:
BACKGROUND
This invention relates generally to the field of raster correction circuits, and, in particular, to correction of orthogonality and parallelogram errors in a raster of a cathode-ray tube of a video display apparatus.
A deflection system utilized in a video display apparatus, such as a television receiver or a video display monitor, typically includes circuitry that allows for the adjustment of a raster on the viewing screen of the apparatus's cathode-ray tube. Such circuitry is required because of, among other things, the nature of the scanning process and the geometry of the cathode-ray tube.
For example, such circuitry may include a raster correction circuit for eliminating orthogonality and parallelogram errors in the scanned raster. The nature of the orthogonality and parallelogram errors and an approach to eliminating both of them is described in a U.S. patent application entitled “VERTICAL DEFLECTION CIRCUIT WITH RASTER CORRECTION”, which was filed on May 17, 1996, in the name of Walter Truskalo et al., and was assigned Ser. No. 08/649,409. That application discloses an arrangement for modulating a vertical deflection current at a horizontal rate for substantially offsetting a downhill scan effect caused by vertical deflection of the electron beam, thereby correcting orthogonality and parallelogram errors in the raster. A raster subject to orthogonality and parallelogram errors is illustrated in FIG.
1
.
Such circuitry may also include a centering circuit for, illustratively, horizontally centering the raster on the viewing screen of the tube. Centering the raster is necessary to ensure the most efficient use of the tube, which occurs when the size of the scanned raster is substantially the same size as the tube's viewing screen. The need for horizontal centering is most pronounced when the amount of horizontal overscan is reduced or, in other words, when the size of the scanned raster is reduced to the size of the tube's viewing screen. Centering the raster is typically accomplished by causing a direct current of selected polarity and amplitude to flow through the appropriate deflection coils, either horizontal or vertical.
In the manufacture of a video display apparatus, it is desirable to consolidate circuitry to the greatest possible extent. Such consolidation provides several advantages, among them: decreased parts count, decreased cost, increased reliability, and an increase in the amount of space available within the apparatus's chassis. Accordingly, it is desirable to consolidate the circuits that perform the raster correction and centering functions.
SUMMARY
The present invention is directed to a deflection system that satisfies the need to consolidate circuitry in a video display apparatus to the greatest possible extent.
A deflection system according to the inventive arrangements taught herein comprises a vertical deflection coil for deflecting the scanning electron beam between upper and lower edges of the raster; a raster centering circuit, which has a centering inductor, for centering the raster on the screen; and a raster correction transformer. The raster correction transformer uses the centering inductor for a primary winding and has a secondary winding coupled to the vertical deflection coil. The centering inductor and the secondary winding are advantageously wound around the same core.
The vertical deflection coil may comprise first and second vertical deflection windings coupled in either a series or a shunt arrangement.
It is advantageous to use the centering inductor as the primary winding of the raster correction transformer because then the vertical deflection circuit and the raster centering circuit can both be mounted with the deflection yoke assembly on a neck portion of the cathode-ray tube of the video display apparatus. This simplifies assembly of the video display apparatus because it obviates the need to run wires from the chassis of the video display apparatus to the vertical deflection circuit and the raster centering circuit.
The above, and other features, aspects, and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.
REFERENCES:
patent: 2478744 (1949-08-01), Clark
patent: 2637832 (1953-05-01), Rogers
patent: 2795734 (1957-06-01), Dietch
patent: 3683231 (1972-08-01), Jagatic
patent: 3814981 (1974-06-01), Rusk
patent: 4037137 (1977-07-01), Dietz
patent: 4572993 (1986-02-01), Haferl
patent: 4703233 (1987-10-01), Rodriguez-Cavazos
patent: 5162705 (1992-11-01), Golik
patent: 5691609 (1997-11-01), Park
patent: 6081078 (2000-06-01), Trusklo et al.
patent: 072595 (1983-02-01), None
patent: 797350 (1997-09-01), None
patent: 808058 (1997-11-01), None
Fernsler Ronald Eugene
Truskalo Walter
Fried Harvey D.
Henig Sammy S.
Lee Wilson
Thomson Licensing S.A.
Tripoli Joseph S.
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