Dynamic focusing circuit of a monitor system

Details Dynamic focusing circuit of a monitor system Dynamic focusing circuit of a monitor system

1999-08-16

2001-12-04

Wong, Don (Department: 2821)

Electric lamp and discharge devices: systems

Cathode ray tube circuits

Cathode-ray deflections circuits

C315S403000

Reexamination Certificate

active

06326744

ABSTRACT:

CLAIM OF PRIORITY
This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C §119 from an application entitled Dynamic Focusing Circuit Of A Monitor earlier filed in the Korean Industrial Property Office on Aug. 25, 1998, and there duly assigned Ser. No. 98-34445 by that Office.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a monitor system, and more particularly, to a dynamic focusing circuit of a monitor system for effectively compensating a defocusing of a screen which often occurs in the monitor system which adopts a cathode-ray tube (hereinafter, refer red to as “CRT”).
2. Description of the Prior Art
In general, the CRT of the monitor system has an electron gun for emitting an electron beam, an anode for accelerating the electron beam emitted from the electron gun to be moved to the front of the CRT, a deflecting yoke (hereinafter, referred to as “DY”) for deflecting the accelerated electron beam to determine a moving direction of the electron beam, a negative electrode for emitting hot electrons in response to a red-green-blue video signal (hereinafter, referred to as “RGB video signal”) input to the CRT and grids for supplying the hot electrons emitted from the negative electrode to a fluorescent screen as the electron beam. At this time, luminescent materials corresponding to the each of the red, green and blue colors are regularly arranged on the fluorescent screen. The video displayed on the CRT is formed by light generated by means of colliding the electron beam passed the grids with the luminescent materials arranged on the fluorescent screen.
However, the more a deflecting angle, according to the DY, enlarges, the more a diameter of the electron beam of the CRT enlarges in general. That is, the more the electron beam becomes distant from the center of the fluorescent screen, the more the diameter of the electron beam which collides with the luminescent materials enlarges. Accordingly, the focusing depth of the video displayed on the screen decreases. To prevent the focusing depth from decreasing, a method which adopts a dynamic focusing circuit for stably supplying a voltage applied to the grid corresponding to a focusing electrode among the grids has been disclosed.
However, such dynamic focusing circuit can not correctly compensate the defocusing due to delay and distortion of the signal caused by a stray capacitance of a transfomer. Also, in a case where a user changes vertical or horizontal size of the screen of the monitor system, it is not able to compensate the defocusing because waveforms of vertical and horizontal parabolic signals applied to the dynamic focusing circuit are changed.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to provide a dynamic focusing circuit of a monitor system for effectively compensating a defocusing of a screen which often occurs in the monitor system which adopts a CRT.
In order to achieve the above object, the present invention provides a dynamic focusing circuit of a monitor system, which comprises: oscillation signal generating means for generating horizontal and vertical parabolic signals in response to a reference oscillation signal applied from an outside; first amplifying means for amplifying the horizontal parabolic signal from the oscillation signal generating means and outputting a first amplification signal; second amplifying means for amplifying the vertical parabolic signal from the oscillation signal generating means and outputting a second amplification signal; and signal mixing means for mixing the first and second amplification signals and outputting a dynamic focusing signal.
In the dynamic focusing system of the monitor system according to the present invention, the vertical and horizontal parabolic signals are amplified by the amplifying sections of the dynamic focusing circuit section, respectively. The vertical and horizontal parabolic signals amplified by the amplifying sections are mixed by the transformer and are applied to the grid. Accordingly, delay and distortion of the signal caused by the stray-capacitance of the transformer does not occur. Also, the waveform of the dynamic focusing signal is stably maintained even though the user changes a vertical or a horizontal size of the screen of the monitor system. As a result, it is able to easily and correctly compensate for any defocusing of the video displayed on the CRT.


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