Electric lamp and discharge devices: systems – Cathode ray tube circuits – Cathode-ray deflections circuits
Reexamination Certificate
1998-12-15
2001-04-10
Ham, Seungsook (Department: 2878)
Electric lamp and discharge devices: systems
Cathode ray tube circuits
Cathode-ray deflections circuits
C315S370000
Reexamination Certificate
active
06215257
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a deflection yoke, and more particularly to an apparatus for correcting a misconvergence and geometric distortion of the deflection yoke.
2. Description of the Prior Art
FIG. 1
shows the construction of a conventional cathode ray tube (referred to hereinafter as CRT). In this drawing, the reference numeral
100
denotes the CRT and
10
denotes a deflection yoke which is mounted on a neck
110
of the CRT
100
. This deflection yoke
10
is generally classified into a saddle-saddle type as shown in
FIGS. 2
a
and
2
b
and a saddle-toroidal type as shown in
FIGS. 3
a
and
3
b
according to the wound forms of coils. The deflection yoke
10
acts to deflect electron beams emitted from a BGR electron gun
120
, installed in the neck
110
of the CRT
100
, left, right, upward and downward, in order to impact them on their accurate positions of a phosphor screen of the CRT
100
.
FIGS. 2
a
and
2
b
show the construction of a conventional deflection yoke of the saddle-saddle type. As shown in these drawings, horizontal deflection coils
12
of the saddle type are disposed respectively on the upper and lower portions of the inner surface of a screen part of a generally conical coil separator
11
, and vertical deflection coils
13
of the saddle type are disposed respectively on the left and right portions of the outer surface of the screen part. A generally cylindrical ferrite core
14
is provided on the outer surface of the screen part of the coil separator
11
to reinforce magnetic fields of the vertical deflection coils
13
. Coma precoils
15
are externally mounted on a neck part of the coil separator
11
to correct comae generated by the vertical deflection coils
13
.
FIGS. 3
a
and
3
b
show the construction of a conventional deflection yoke of the saddle-toroidal type. As shown in these drawings, horizontal deflection coils
12
of the saddle type are disposed respectively on the upper and lower portions of the inner surface of a screen part of a generally conical coil separator
11
, and a generally cylindrical ferrite core
14
is provided on the outer surface of the screen part. Vertical deflection coils
16
of the toroidal type are provided respectively on the upper and lower portions of the ferrite core
14
. Coma precoils
15
are externally mounted on a neck part of the coil separator
11
to correct comae generated by the vertical deflection coils
16
. The vertical deflection coils
16
are mechanically wound on the upper and lower portions of the ferrite core
14
and are electrically connected in series to one another in order of the left upper portion (
16
a
-
1
), left lower portion (
16
a
-
2
), right upper portion (
16
b
-
1
) and right lower portion (
16
b
-
2
) as shown in
FIG. 3
c.
In the deflection yoke of the saddle-saddle type as shown in
FIGS. 2
a
and
2
b
, there is a difference between the left and right magnetic fields due to relative disseminations and/or relative current amounts of the left and right vertical deflection coils
13
a
and
13
b
. This magnetic field difference results in the occurrence of a misconvergence and geometric distortion (G/D) on the screen.
Similarly, in the deflection yoke of the saddle-toroidal type as shown in
FIGS. 3
a
and
3
b
, there is a difference between the left and right magnetic fields due to relative disseminations and/or relative current amounts of the vertical deflection coils
16
a
wound on the left upper and left lower portions of X-Y coordinates and the vertical deflection coils
16
b
wound on the right upper and right lower portions of the X-Y coordinates. Similarly, this magnetic field difference results in the occurrence of a misconvergence and geometric distortion (G/D) on the screen.
The misconvergence is generally classified into a YV misconvergence and a YHC misconvergence. The YV misconvergence represents a vertical misconvergence where horizontal lines of red color R diverge from horizontal lines of blue color B on the upper and lower portions of the Y axis of the screen, as shown in
FIGS. 4
a
and
4
c
. The YHC misconvergence represents a horizontal misconvergence where a vertical line R and a vertical line B cross each other as shown in FIG.
5
. The G/D represents a distorted state on the screen as shown in
FIGS. 6
a
and
6
c
. Especially,
FIGS. 6
a
and
6
c
show trapezoid distortions.
FIG. 7
is a circuit diagram of a conventional circuit for correcting a YV misconvergence of the deflection yoke of the saddle-saddle type shown in
FIGS. 2
a
and
2
b
. As shown in this drawing, the left and right vertical deflection coils
13
a
and
13
b
are electrically connected in series to each other. A differential shunt circuit is connected in parallel to the left and right vertical deflection coils
13
a
and
13
b
. This differential shunt circuit is provided with two fixed resistors
21
a
and
21
b
and a variable resistor
22
.
In the conventional YV misconvergence correction circuit shown in
FIG. 7
, the relative amounts of current flowing respectively through the left and right vertical deflection coils
13
a
and
13
b
are controlled by adjusting a resistance of the variable resistor
22
. As a result, the left and right relative magnetic fields are adjusted to adjust the YV misconvergence as shown in
FIGS. 4
a
or
4
c
in such a manner that the R and B lines can be converged as shown in
FIG. 4
b.
FIG. 8
is a circuit diagram of a conventional circuit for correcting a YV misconvergence of the deflection yoke of the saddle-toroidal type shown in
FIGS. 3
a
and
3
b.
As shown in this drawing, the left upper vertical deflection coil (
16
a
-
1
), left lower vertical deflection coil (
16
a
-
2
), right upper vertical deflection coil (
16
b
-
1
) and right lower vertical deflection coil (
16
b
-
2
) are sequentially connected in series. A differential shunt circuit is connected in parallel to the left upper and left lower vertical deflection coils
16
a
and the right upper and right lower vertical deflection coils
16
b
. This differential shunt circuit is provided with two fixed resistors
21
a
and
21
b
and a variable resistor
22
.
In the conventional YV misconvergence correction circuit shown in
FIG. 8
, in a similar manner to that shown in
FIG. 7
, the relative amounts of current flowing respectively through the left upper and left lower vertical deflection coils
16
a
and the right upper and right lower vertical deflection coils
16
b
are controlled by adjusting a resistance of the variable resistor
22
. As a result, the left and right relative magnetic fields are adjusted to adjust the YV misconvergence as shown in
FIGS. 4
a
or
4
c
in such a manner that the R and B lines can be converged as shown in
FIG. 4
b.
However, when the YV misconvergence is corrected in the deflection yoke of the saddle-saddle type and/or saddle-toroidal type, a G/D pattern as well as a convergence pattern is varied simultaneously with the convergence pattern according to a variation in the left and right magnetic fields resulting from a variation in the relative amounts of current flowing respectively through the left vertical deflection coil
13
a
or
16
a
and the right vertical deflection coil
13
b
or
16
b
. For this reason, a new G/D occurs although the YV misconvergence has been corrected. Further, even when the variable resistor
22
is not varied, the G/D generally occurs due to a difference between disseminations of the left and right vertical deflection coils which occurs upon winding them. Namely, because of a dissemination difference resulting from a winding unbalance of the coils and mechanical assembling thereof, it is substantially very difficult that the coils wound at the first to fourth upper limits of the X-Y coordinates generate completely symmetrical magnetic fields. For this reason, due to a dissemination unbalance, the G/D may occur as shown in
FIGS. 6
a
or
6
c
although the misconvergence has completely been corrected as shown in
FIG. 4
b
.
Ham Seungsook
Ladas & Parry
Lee Shun
Samsung Electro-Mechanics Co. Ltd.
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