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Low Dissipation E-W Raster Correction

IP.com Disclosure Number: IPCOM000100778D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 2 page(s) / 67K

Publishing Venue

IBM

Related People

Luck, G: AUTHOR [+2]

Abstract

A circuit is disclosed for use in color monitors to correct East-West (E-W) CRT distortion and eliminate a transistor stage in the correction circuit by employing an IC. Reduced power dissipation and component count with raised reliability result from powering an E-W correction IC from the line output stage that it drives.

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This is the abbreviated version, containing approximately 55% of the total text.

Low Dissipation E-W Raster Correction

       A circuit is disclosed for use in color monitors to
correct East-West (E-W) CRT distortion and eliminate a transistor
stage in the correction circuit by employing an IC.  Reduced power
dissipation and component count with raised reliability result from
powering an E-W correction IC from the line output stage that it
drives.

      E-W correction is required in color monitors because of the
need to compensate for distortion of the raster.  This distortion
arises from two main causes:  the design of the deflection system,
and the arrangement of the electron guns (delta or in-line) in the
picture tube.  Deflection coils are designed for optimum quality over
the entire raster area, but this design requirement inevitably leads
to distortion of the raster.  Distortion produced by the gun
arrangement occurs because it is not possible to mount the three guns
on the same axis.  Some of the E-W distortion is corrected by field
shapers embedded in the deflection coil; but the residual distortion
has to be eliminated by the use of a diode modulator circuit.

      Diode Modulator Circuit In order to change the effective width
of the raster from the top to the bottom of the scan, an impedance
which varies at field rate is introduced in series with the
horizontal yoke shown in Fig. 1.  It requires careful design to
prevent the horizontal retrace time varying with apparent width
change.  The circuitry typically employs some...