Horizontal deflection coil for deflection yoke

Details Horizontal deflection coil for deflection yoke Horizontal deflection coil for deflection yoke

2003-09-10

2004-12-28

Vu, David (Department: 2828)

Electric lamp and discharge devices: systems

Cathode ray tube circuits

Cathode-ray deflections circuits

C315S371000

Reexamination Certificate

active

06836084

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a horizontal deflection coil for a deflection yoke used in a cathode ray tube, and more particularly to a horizontal deflection coil for a deflection yoke, which is provided with a section for correcting inner pincushion distortion, thereby removing the need for another circuit for correcting the inner pincushion distortion.
2. Description of the Prior Art
Recently, the market trend for display apparatuses pursues flatness, large size, high-resolution, low power consumption, and slimness that enables installation space to be reduced and the efficiency of use of space to be increased.
A computer monitor that is one of such display apparatus has been developed in pursuit of flatness, large size, high-resolution, low power consumption and slimness. Particularly, high quality display apparatuses, in which power consumption is reduced and effective screens are large-sized, are required to follow stringent environmental regulations.
The monitor market has been developing at 10% annually, and is divided into a Cathode Ray Tube (CRT) monitor market and a Liquid Crystal Display (LCD) monitor market.
However, with rapid progress of relevant technologies, the LCD monitor market has been developing at 50% annually, compared to the CRT monitor market. Accordingly, in this situation, CRT monitors are required to improve their quality and have competitive power in order to compete with LCD monitors.
The maximum share of the CRT monitor market is occupied by 17″~19″ flat screen monitors to meet the market trend toward large sizes and flatness.
FIG. 1
shows an example of a conventional CRT, which shows a conventional curved screen CRT.
The conventional curved screen CRT includes a convex screen panel
1
that is curved outward at its front surface, a funnel
2
that is attached to the back end of the screen panel
1
using frit glass and maintains the inside of the CRT in a vacuum state, an electron gun
5
that is mounted in a neck
7
positioned at the rear of the funnel
2
and irradiates electron beams
4
a
,
4
b
and
4
c
, and a deflection yoke
6
that deflects the electron beams
4
a
,
4
b
and
4
c
irradiated from the electron gun
5
in left, right, up and down directions.
The deflection yoke
6
is used to apply horizontal and vertical deflection magnetic fields to the neck
7
of the CRT. The deflection yoke
6
includes a vertical deflection coil (not shown) that vertically deflects the electron beams
4
a
,
4
b
and
4
c
by applying the vertical deflection magnetic field to the electron beams
4
a
,
4
b
and
4
c
irradiated from the electron gun
5
of the CRT, a horizontal deflection coil (not shown) that horizontally deflects the electron beams
4
a
,
4
b
and
4
c
by applying the horizontal deflection magnetic field to the electron beams
4
a
,
4
b
and
4
c
irradiated from the electron gun
5
of the CRT, a separator (not shown) that precisely separates the horizontal deflection coil from the vertical deflection coil and electrically insulates the horizontal deflection coil from the vertical deflection coil, and a ferrite core (not shown) that enhances magnetic fields applied by the horizontal and vertical deflection coils.
The horizontal deflection coil and the vertical deflection coil are arranged to be perpendicular to each other in order to apply horizontal and vertical deflection magnetic fields to the electron beams
4
a
,
4
b
and
4
c
irradiated from the electron gun
5
.
In such a curved screen CRT monitor, the screen panel
1
is curved to be protruded outward, deflection distances between the deflection yoke
6
and the fluorescent surface of a screen do not greatly differ from each other in the upper, middle and lower portions of the screen, so that distortion is limitedly generated.
That is, as shown in
FIG. 1
, in the conventional curved screen panel
1
, a deflection distance A of the electron beam
4
a
irradiated onto the upper portion of the screen, a deflection distance B of the electron beam
4
b
irradiated onto the middle portion of the screen and a deflection distance C of the electron beam
4
c
irradiated onto the lower portion of the screen do not greatly differ from each other, so that distortion is limitedly generated.
However, the recent display market trend pursues flatness of a screen, whose panel is constructed to be flat, as described above, so that a screen panel
11
is formed to be flat, as shown in FIG.
2
.
A CRT provided with the flat screen panel
11
has various merits compared to the conventional curved screen monitor, while the CRT has a defect of increased distortion characteristics.
That is, since the screen panel
11
is flat, as shown in
FIG. 2
, a deflection distance A′ of the electron beam
14
a
irradiated onto the upper portion of the screen, a deflection distance B′ of the electron beam
14
b
irradiated onto the middle portion of the screen and a deflection distance C′ of the electron beam
14
c
irradiated onto the lower portion of the screen differ from each other, so that distortion is generated.
As the deflection distances A′, B′ and C′ differ from each other, an inner pincushion phenomenon resulting from distortion is generated in the front surface of the screen as shown in FIG.
3
.
In general, a picture is formed by a deflection yoke that forms a pincushion-shaped magnetic field using a horizontal deflection coil and a barrel-shaped magnetic field using a vertical deflection coil. The inner pincushion phenomenon almost does not appear due to the curvature of the CRT in a general curved screen panel, or is invisible to the naked eye when it appears in the curved screen panel.
However, it is found that the inner pincushion phenomenon appears in a flat CRT because vertical pincushion distortion is incompletely corrected in a central portion of an area between the central portion and each side end of the screen.
The inner pincushion phenomenon is pincushion distortion in which a picture displayed on the CRT becomes curved inward in a central portion of an area between the central portion and each side end of the screen as indicated by solid lines shown in FIG.
3
.
That is, the vertical lines of the screen should appear as straight lines to connect the upper, middle and lower portions of the screen as indicated by dotted lines shown in FIG.
3
. However, if the inner pincushion phenomenon described above is generated, a picture seems to be curved inward, so that the quality of the screen is decreased and high quality of the CRT may not be offered.
Accordingly, an additional circuit is used in the deflection yoke to improve the inner pincushion phenomenon, and the circuit is referred to as an inner pincushion correction module.
The inner pincushion correction module is an additional circuit that may remove pincushion distortion in order to correct the vertical pincushion distortion, which is caused by horizontal deflection coils that forms a pincushion-shaped magnetic field.
The inner pincushion correction module is operated by an induced electromotive force caused by a mutual inductance between vertical and horizontal deflection coils.
An example of the conventional inner pincushion correction module is shown in
FIG. 4
, and is described with reference to FIG.
4
.
Two horizontal correction coils L
3
and L
4
are wound to generate reverse magnetic fields, and permanent magnets
19
and
20
for apply a fixed deflection magnetic field to the horizontal correction coils L
3
and L
4
and a vertical correction coil L
7
are disposed.
The horizontal correction coils L
3
and L
4
receive the fixed deflection magnetic field applied by the permanent magnets
19
and
20
. The size of the central portion of the screen becomes small and the sizes of the corners of the screen become identical by the action of the vertical correction coil L
7
, so that left and right pincushion distortions are corrected.
If current flows into the horizontal correction coils L
3
and L
4

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