Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Reexamination Certificate
2002-05-06
2003-12-16
Ho, Tan (Department: 2821)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
C348S805000
Reexamination Certificate
active
06664747
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 for DYNAMIC FOCUS REGULATION CIRCUIT FOR DISPLAY DEVICE earlier filed in the Korean Industrial Property Office on Aug. 31, 2001 and there duly assigned Serial No. 2001-53306.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a display apparatus, and more particularly, to a dynamic focus regulation circuit for supplying a uniform parabolic waveform voltage regardless of variation of a horizontal frequency in a display mode.
2. Description of the Related Art
In a CRT (cathode ray tube) of a display apparatus, an electron beam is emitted from an electron gun unit to a panel coated with red/green/blue fluorescent material so as to form pixels, and thus a 2-dimensional picture is displayed on the panel by supplying a saw tooth waveform electric current to vertical and horizontal deflection coils.
In the conventional CRT, the panel is curved outwardly, and the distance between the electron gun unit and the panel is not uniform, and thus the sharpness of the picture becomes different according to the positions of pixels. That is, the sharpness on the edge of the panel is inferior to that on the center thereof. In the case of a high-resolution monitor, the above phenomenon is regulated by applying a regulation waveform voltage to the CRT focus voltage component by a focus regulation circuit. The regulation waveform is induced by an H-DY (Horizontal Deflection Yoke) generally outputting a horizontal deflection signal, and is synchronized with a deflection signal having a parabolic waveform.
FIG. 5
illustrates a conventional dynamic focus regulation circuit detecting a dynamic focus output waveform. As shown therein, the dynamic focus regulation circuit comprises a horizontal deflection circuit
110
oscillating a horizontal deflection signal, an S-regulation circuit
120
regulating an electric current outputted from the horizontal deflection circuit
110
, a dynamic focus output circuit
130
outputting a dynamic focus waveform voltage by amplifying the parabolic waveform voltage from the S-regulation circuit
120
, and a diode modulation circuit
140
horizontally modulating a raster.
The horizontal deflection circuit
110
includes a horizontal driving transistor
112
, a damper diode
114
, a resonance capacitor
116
, and an H-DY
118
.
The horizontal driving transistor
112
is switched on/off according to a horizontal driving signal generated by a video IC (not shown) or a horizontal oscillating IC (not shown). When the horizontal driving transistor
112
is switched on, B+ electric power from an FBT (Fly Back Transformer) is supplied to the H-DY
118
.
If the horizontal driving transistor
112
is rapidly switched on according to the horizontal driving signal, an electric current is induced to the H-DY
118
. On the other hand, if the horizontal driving transistor
112
is switched off, the electricity stored in the H-DY
118
is charged in the resonance capacitor
116
. Herein, when the resonance capacitor
116
is perfectly charged with the electricity, the resonance capacitor
116
discharges its electricity to the H-DY
118
, thereby re-storing the H-DY
118
with the electricity. Thereafter, according as the H-DY
118
is stored with electric energy, when the voltage of the H-DY
118
is so high that a forward bias can be applied to the damper diode
114
, the damper diode
114
is shorted and the electricity of the H-DY
118
vanishes.
Thus, when the electricity of the H-DY
118
vanishes into zero, the horizontal driving transistor
112
is switched on again by the horizontal driving signal, to thereby repeat the above described process. Thus, an electric current having a saw tooth waveform is generated for deflecting an electron beam horizontally.
The S-regulation circuit
120
regulates the saw tooth waveform electric current applied to the H-DY
118
so as to maintain the linearity of a screen. The S-regulation circuit
120
includes a basic S-regulation capacitor
119
connected with the H-DY
118
and the resonance capacitor
116
in parallel, an S-regulation capacitor
122
, and a switching transistor
124
switching on/off the S-regulation capacitor
122
. Herein, the switching transistor
124
is controlled by a microcomputer
150
.
With this configuration, if electric power is supplied to the S-regulation capacitor
122
by switching on/off the switching transistor
124
according to control of the microcomputer
150
, the voltage applied to the H-DY
118
is regulated by means of combination of the capacitance of the S-regulation capacitor
122
and the capacitance of the basic S-regulation capacitor
119
, thereby regulating the chopping waveform electric current.
Further, the dynamic focus output circuit
130
inverting-amplifies the convex parabolic waveform voltage across opposite ends of the basic S-regulation capacitor
119
, to thereby output the dynamic focus waveform voltage.
The dynamic focus output circuit
130
is connected with two ends of the basic S-regulation capacitor
119
, and includes a capacitor
134
applying only the AC signal of the convex parabolic waveform voltage through DC-coupling, a transformer (T)
132
inverting-boosts the convex parabolic waveform voltage outputted from the capacitor
134
, and a capacitor
136
outputting the parabolic waveform voltage induced in a secondary side of the transformer (T)
132
through noise-removal and DC-coupling.
That is, the convex parabolic waveform voltage outputted from two ends of the basic S-regulation capacitor
119
is inverting-amplified through the capacitor
134
and the transformer (T)
132
, and therefore changed into a convex parabolic waveform voltage to be outputted as the dynamic focus waveform voltage.
On the other hand, a monitor has various display modes. For example, a VGA mode has 640×480 resolution and a 31.5 KHz horizontal frequency, a SVGA mode has 1024*768 resolution and 35~37 KHz horizontal frequencies, and a high-resolution mode has 1024×768 through 1280×1024 resolution and 64~75 KHz horizontal frequencies.
To oscillate a horizontal deflection signal corresponding to the horizontal frequency, the capacitance of the S-regulation circuit
120
should be altered, i.e., the higher the resolution is, the higher the frequency of horizontal deflection signal should be. However, the higher the frequency of horizontal deflection is, the lower the parabolic waveform voltage generated from the S-regulation capacitor
122
is.
As described above, a frequency inputted to a display apparatus is altered according to setting up a display mode of the display apparatus, and therefore a parabolic waveform voltage corresponding to the horizontal frequency is altered. Thus, it is impossible to generate a precise focus voltage.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been made keeping in mind the above-described shortcomings and user's need, and an object of the present invention is to provide a dynamic focus regulation circuit for supplying a uniform parabolic waveform voltage regardless of variation of a horizontal frequency in a display mode.
This and other objects of the present invention may be accomplished by the provision of a horizontal dynamic focus regulation circuit, which induces a horizontal dynamic focus waveform voltage by a horizontal deflection circuit generating a different frequency according to a display mode of a display apparatus, comprising a microcomputer outputting a plurality of control signals; a plurality of switching parts corresponding to the plurality of control signals outputted from the microcomputer, respectively; a plurality of S-regulation capacitors connecting with the plurality of switching parts in series, respectively; an auxiliary capacitor provided on a line diverged from a line connecting each switching part with each S-regulation capacitor, and being respectively connected with the S-regul
A Minh D
Ho Tan
Samsung Electronics Co,. Ltd.
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