Deflection yoke for compensating mis-convergence

Details Deflection yoke for compensating mis-convergence Deflection yoke for compensating mis-convergence

2003-04-08

2004-09-21

Barrera, Ramon M. (Department: 2832)

Electricity: magnetically operated switches, magnets, and electr

Magnets and electromagnets

Electron or ion beam deflecting type

C335S210000, C313S440000

Reexamination Certificate

active

06794969

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a deflection yoke for compensating mis-convergence, and more particularly to a deflection yoke for compensating mis-convergence which can compensate an error generated due to upper and lower side control unbalance during the YH compensation circuit operation by equalizing length of wires connected between upper and lower side coma free coils positioned at a rear cover unit of the deflection yoke and connection terminals of a printed circuit board.
2. Description of the Related Art
In general, images which users watch on TV screen are not fixed images but consecutive still images displayed about 30 times per second. Colors displayed on the screen are combinations of electron beams radiated through red, blue and green phosphors coated on the screen surface of a cathode ray tube.
That is, one frame containing whole image information is formed by interlaced-scanning 525 scanning lines from the top left end of the screen to the bottom left end for {fraction (1/30)} second, and intensity of electron beams is controlled and brightness of the screen is varied by using the fact that the electron beams become bright when severely colliding with the phosphor, thereby visualizing image signals. If the electron beams are not scanned in the aforementioned manner, one bright dot is generated at the center of the screen, and images are not normally transmitted.
A cathode ray tube and a deflection yoke are important means for reproducing video image signals transmitted through a camera on a display as images recognizable by users.
In spite of development of new display devices such as a liquid crystal display and plasma display panel, the cathode ray tube has been most widely used because of high display quality and cost to performance rate.
In general, the cathode ray tube includes the deflection yoke which precisely irradiates three color electron beams from electron guns to a phosphor film coated on the screen surface of the cathode ray tube by deflection.
The deflection yoke which is the most important means of the magnetic devices of the cathode ray tube serves to reproduce electric signals transmitted in time series as images on the screen of the cathode ray tube.
That is, the electron beams from the electron guns go straight toward the screen due to high voltage, and thus radiate only the center phosphor of the screen. Here, the deflection yoke externally deflects the electron beams to reach the screen in the scanning order. The deflection yoke precisely deflects the electron beams to the phosphor film coated on the screen of the cathode ray tube by forming a magnetic field, and using the fact that the direction of the electron beams is changed because the electron beams pass through the magnetic field and receive an electromagnetic force.
FIG. 1
is a side diagram illustrating a general cathode ray tube. Referring to
FIG. 1
, a deflection yoke
104
is positioned in an RGB electron gun unit
103
of a cathode ray tube
100
, for deflecting electron beams from electron guns
103
a
to a phosphor film coated on a screen surface
102
.
The phosphor of the phosphor film transforms electron energy to light due to collision of the electron beams. Selection and coating of phosphor are important to obtain appropriate colors, durability and long life span.
The deflection yoke
104
includes a pair of coil separators
110
which are upper and lower side symmetrical and combined into one. The coil separator
110
insulates a horizontal deflection coil
115
and a vertical deflection coil
116
as well as appropriately fixes their positions. The coil separator
110
includes a screen unit
111
a
coupled with the screen surface
102
, a rear cover unit
111
b
, and a neck unit
112
extended from the center of the rear cover unit
111
b
and coupled with the electron gun unit
103
of the cathode ray tube
100
.
The horizontal deflection coil
115
and the vertical deflection coil
116
for forming a horizontal deflection magnetic field and a vertical deflection magnetic field with external power are installed on the inner and outer circumferences of the coil separator
110
.
A pair of ferrite cores
114
composed of a magnetic material for enhancing the magnetic field generated from the vertical deflection coil
116
are mounted to surround the vertical deflection coil
116
.
A printed circuit board p is installed at one side of the rear cover unit
111
b
of the coil separator
110
, for controlling electric signals for the deflection yoke through a few circuit elements, by for example, supplying power to the horizontal and vertical deflection coils
115
and
116
.
When different frequency saw tooth waves are applied to the horizontal and vertical deflection coils
115
and
116
, under the Fleming's left-hand law, the horizontal deflection coil
115
generates a magnetic force line in the vertical direction so that the electron beams receive force in the horizontal direction, and the vertical deflection coil
116
generates a magnetic force line in the horizontal direction so that the electron beams receive force in the vertical direction. Accordingly, red, green and blue electron beams R, G and B from the electron guns
113
a
are deflected at a predetermined angle to determine scanning positions on the screen.
On the other hand, the deflection yoke of
FIG. 1
is classified into a saddle—saddle type of
FIGS. 2 and 3
and a saddle-toroidal type (not shown) according to winding structure of coils.
In the saddle—saddle type deflection yoke as shown in
FIGS. 2 and 3
, a saddle type horizontal deflection coil
115
is installed at the upper and lower sides of the inner circumference of a screen unit
111
a
of a conical coil separator
110
, and a saddle type vertical deflection coil
116
is installed at the right and left sides of the outer circumference thereof. In addition, a cylindrical ferrite core
114
is installed on the outer circumference of the screen unit
111
a
of the coil separator
110
to enhance a magnetic field of the vertical deflection coil
116
.
Coma free coils (not shown) for compensating coma generated by the vertical deflection coil
116
are positioned around the outer circumference of a neck unit
112
of the coil separator
110
.
In the saddle-toroidal type deflection yoke, a saddle type horizontal deflection coil
115
is installed at the upper and lower sides of the inner circumference of a screen unit of a conical coil separator
110
, a cylindrical ferrite core
114
is disposed on the outer circumference thereof, and a toroidal type vertical deflection coil
116
is wound along the upper and lower sides of the ferrite core
114
.
Coma free coils (not shown) for compensating coma generated by the vertical deflection coil
116
are positioned around the outer circumference of a neck unit
112
of the coil separator
110
.
A printed circuit board p is installed at one side of a rear cover unit
111
b
of the coil separator
110
, for controlling electric signals for the deflection yoke through a few circuit elements, by for example, supplying power to the horizontal and vertical deflection coils
115
and
116
.
On the other hand, in the saddle—saddle type or saddle-toroidal type deflection yoke, different magnetic fields are generated at both sides of the vertical and horizontal deflection coils installed to face each other due to distribution properties and relative current amount variations of the deflection coils.
In this case, three color electron beams initially emitted from the neck unit of the coil separator, namely the neck unit extended from the rear cover unit and coupled with the electron gun unit of the cathode ray tube show different vector trajectories due to positions of the red, green and blue electron guns and magnetic field difference generated from the deflection coils, which generates mis-convergence on the screen.
In order to precisely form images on a color monitor or cathode ray tube, the electron beams from the red, green and blue electron guns o

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