FOCUS VOLTAGE CONTROL ARRANGEMENT WITH ULTOR VOLTAGE TRACKING

Title:

FOCUS VOLTAGE CONTROL ARRANGEMENT WITH ULTOR VOLTAGE TRACKING

Document Type and Number:

WIPO Patent Application WO2003090449

Kind Code:

A3

Abstract:

A video display apparatus (10) includes a cathode ray tube (12) having an ultor terminal for developing an ultor voltage at the ultor terminal to produce a beam current. The ultor voltage has voltage fluctuations in a presence of changes in the beam. A resistive voltage divider (28) is coupled to a source of a first high voltage and to a focus terminal (220) of the cathode ray tube for producing at the focus terminal (220) a second high voltage including voltage fluctuations. The voltage fluctuations are indicative of the voltage fluctuations of the ultor voltage to provide for focus voltage tracking. An amplifier (22) responsive to a periodic correction signal is capacitively coupled via a capacitor (302) having a value of 33 picofarad to the focus terminal. A dynamic focus voltage that varies, in accordance with a variation of a beam landing location, is produced at the focus terminal (220).

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Inventors:

GEORGE JOHN BARRETT (US)

Application Number:

PCT/US2003/012177

Publication Date:

May 06, 2004

Filing Date:

April 21, 2003

Export Citation:

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Assignee:

THOMSON LICENSING SA (FR)
GEORGE JOHN BARRETT (US)

International Classes:

G05F1/00; G05F1/14; G09G1/00; G09G1/04; H04N3/26; (IPC1-7): H01J29/52; H01J29/72

Foreign References:

US5177413A	1993-01-05
US4243918A	1981-01-06
US3825793A	1974-07-23

Other References: