Electric lamp and discharge devices: systems – Cathode ray tube circuits – Power supply from deflection circuit source
Reexamination Certificate
1999-04-29
2001-10-02
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Power supply from deflection circuit source
C315S408000
Reexamination Certificate
active
06297602
ABSTRACT:
BACKGROUND
Field Of The Invention
This invention relates generally to the field of high voltage regulation in an information display apparatus, and, in particular, to regulating the anode voltage in an information display apparatus that utilizes a cathode ray tube.
Background Information
In today's multimedia environment, it becomes increasingly desirable to use a single information display apparatus for several different applications.
For example, in addition to displaying video information, a television receiver can currently be used to display teletext information. Most recently, manufacturers of computers and consumer electronics have begun to offer products wherein the television receiver is also used to display information provided by a computer, such as text pages, high resolution graphics, and the like.
These different applications demand increased performance from the deflection and high voltage circuits of the information display apparatus. For instance, in the display of video information, the information display apparatus is required to provide a dark screen and must be capable of a high beam current and a high anode voltage. The use of the same information display apparatus to display high resolution graphics of the type typically associated with a color display monitor additionally requires that the information display apparatus provide a stable raster size, good focus, and a small spot size. These additional requirements, in turn, depend upon the presence of a well-regulated anode voltage for the cathode ray tube.
One approach is provided by U.S. Pat. No. 5,357,175, which discloses regulating the anode voltage by varying the B+ voltage responsive to variations in the anode voltage. This document also discloses providing an error signal generated from the anode voltage to a horizontal amplitude correction circuit
54
for regulating a pincushion correction voltage. Another approach to regulating the anode voltage for the cathode ray tube is provided by European Patent Application 0 128 223 A1, which discloses a flyback period control circuit
1
that switches a resonating capacitor Ct' into and out of a horizontal deflection circuit only during the flyback period TR. In this way, the flyback period control circuit
1
controls the flyback period TR to control the high voltage HV.
SUMMARY
The present invention is directed to a high voltage regulation circuit that provides a well-regulated anode voltage for the cathode ray tube of the information display device.
A circuit for regulating an anode voltage in an information display apparatus comprises: a horizontal deflection circuit having trace and retrace modes of operation; the horizontal deflection circuit further having a fixed retrace capacitance and a series combination of a switched retrace capacitance and a switch element, the series combination coupled in parallel with the fixed retrace capacitance, wherein the switch element is in a closed position as the horizontal deflection circuit enters the retrace mode of operation; a voltage divider network for providing a sample voltage indicative of a magnitude of the anode voltage; and a control circuit responsive to the sample voltage for controlling the switch element, such that the control circuit effects regulation of the anode voltage by selecting a time during the retrace period at which to place the switch element in an open position.
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.
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*Patent Abstracts of Japan, vol. 009, No. 027, Feb. 6, 1985 & JP 59-171366.
** Patent Abstracts of Japan, vol. 008, No. 135, Jun. 22, 1984 & JP 59-044177.
Davenport Francis A.
Dinh Trinh Vo
Fried Harvey D.
Thomson Licensing S.A.
Tripoli Joseph S.
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