Vertical deflection apparatus

Details Vertical deflection apparatus Vertical deflection apparatus

2002-11-14

2004-12-14

Wong, Don (Department: 2821)

Electric lamp and discharge devices: systems

Cathode ray tube circuits

Cathode-ray deflections circuits

C315S370000, C348S806000

Reexamination Certificate

active

06831427

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATION
This application is a Section 371 of International Application No. PCT/JP02/02159, filed Mar. 7, 2002, the disclosure of which is incorporated herein by reference.
TECHNICAL FIELD
The present invention relates to a vertical deflection apparatus comprising a correction circuit that corrects a north-south pincushion distortion on a CRT (Cathode-Ray Tube).
BACKGROUND ART
In a CRT, the distance from its deflecting center point to its screen (fluorescent screen) increases toward its periphery, so that the swing of an electron beam is the largest at four corners of the screen. Consequently, a north-south (upper-lower) pincushion distortion and an east-west (right-left) pincushion distortion are generated in an image displayed on the screen of the CRT. Particularly, the north-south pincushion distortion is referred to as an NS pincushion distortion, and the east-west horizontal pincushion distortion is referred to as an EW pincushion distortion. The larger the deflection angle of the electron beam is, the larger the pincushion distortions become.
FIG.
16
(
a
) is a diagram showing an example of an NS pincushion distortion on a screen of a CRT, and FIG.
16
(
b
) is a waveform diagram showing an NS pincushion distortion correction current superimposed on a vertical deflection current. In
FIG. 16
, H indicates a horizontal scanning period, and V indicates a vertical scanning period.
As shown in FIG.
16
(
a
), the NS pincushion distortion on the screen of the CRT is in a shape which is constricted at its center, as compared with both its right and left ends. The NS pincushion distortion can be corrected by respectively moving the centers of horizontal scanning lines upward and downward, as indicated by arrows. Therefore, an NS pincushion distortion correction current (hereinafter abbreviated as a correction current) am which changes in a parabolic shape in the horizontal scanning period is superimposed on a sawtooth vertical deflection current VI which changes in the vertical scanning period, as shown in FIG.
16
(
b
). The correction current am has a positive polarity in the first half of a vertical scanning interval (the upper half of the screen), and has a negative polarity in the latter half of the vertical scanning interval (the lower half of the screen). The amplitude of the correction current am increases toward upper and lower ends of the screen from the center thereof.
In order to superimpose a correction current on a vertical deflection current, a system using a supersaturated reactor and a transformer system in which a transformer is inserted in series with a vertical deflection coil and is driven by a parabolic current having a horizontal scanning period (hereinafter referred to as a horizontal parabolic current) have been conventionally employed.
FIG. 17
is a schematic view showing the correction of an NS pincushion distortion by the conventional supersaturated reactor system, where FIG.
17
(
a
) is a diagram showing a supersaturated reactor, and FIG.
17
(
b
) is a diagram showing the relationship between a magnetic flux density B and a magnetic field H in the supersaturated reactor.
In FIG.
17
(
a
), a core
50
in the supersaturated reactor has three legs. Further, a core
51
is arranged on the core
50
, and a permanent magnet
52
is arranged on the core
51
. A horizontal deflection current HI is caused to flow through windings L
H1
and L
H2
of the legs on both sides of the core
50
. Consequently, a magnetic flux &PHgr;
H
is generated. A vertical deflection current VI is caused to flow through a winding L
V
of the leg at the center of the core
50
. Consequently, a magnetic flux &PHgr;
V
is generated. Further, a magnetic flux &PHgr;
B
is generated by the permanent magnet
52
. In the supersaturated reactor, when the magnetic field H is strengthened, the magnetic flux density B is saturated, as shown in FIG.
17
(
b
).
By the configuration shown in FIG.
17
(
a
), the correction current am is superimposed on the vertical deflection current VI supplied to the vertical deflection coil, as shown in FIG.
16
(
b
). Also in the transformer system, the same control is carried out. In such a way, the NS pincushion distortion is corrected.
A horizontal deflection coil and a vertical deflection coil are arranged so as to be orthogonal inside a deflection yoke. From a problem in the fabrication of the deflection yoke, orthogonality between the horizontal deflection coil and the vertical deflection coil is not necessarily ensured. Accordingly, a current component caused by a horizontal deflection current is induced by electromagnetic coupling from the horizontal deflection coil to the vertical deflection coil inside the deflection yoke.
Furthermore, a horizontal flyback pulse generated in the horizontal deflection coil in a horizontal blanking interval reaches a voltage of a thousand and several hundred Vp-p (volt peak-to-peak), and a harmonic component of the horizontal flyback pulse has a frequency which is several ten times the horizontal scanning frequency. Accordingly, the horizontal deflection coil and the vertical deflection coil are coupled to each other through a stray capacitance between the horizontal deflection coil and the vertical deflection coil. Consequently, a current component caused by the horizontal deflection current is induced by electrostatic coupling from the horizontal deflection coil to the vertical deflection coil.
Induction of a current component from a horizontal deflection coil to a vertical deflection coil is referred to as HV crosstalk, and a current component induced from the horizontal deflection coil to the vertical deflection coil is referred to as an HV crosstalk component. When the HV crosstalk component is superimposed on a vertical deflection current supplied to the vertical deflection coil, scanning lines are distorted, so that an image to be displayed is distorted.
A current component caused by the vertical deflection current is induced from the vertical deflection coil to the horizontal deflection coil. However, the horizontal deflection current is as large as several ten Ap-p (ampere peak-to-peak), while the vertical deflection current is as small as 1 to 2 Ap-p. Further, a voltage of a pulse generated in the vertical deflection coil in a vertical blanking interval is less than 100 volts, and the frequency thereof is from several ten hertz to a maximum of several hundred hertz. Therefore, the current components respectively induced by electromagnetic coupling and electrostatic coupling from the vertical deflection coil to the horizontal deflection coil are so small that they are hardly worth consideration.
In the correction of the NS pincushion distortion using the conventional supersaturated reactor system and transformer system, the HV crosstalk generated inside the deflection yoke is not considered.
FIG. 18
is a diagram for explaining the HV crosstalk.
FIG.
18
(
a
) illustrates a vertical deflection current VI on which a correction current is superimposed, FIG.
18
(
b
) illustrates a correction current am, FIG.
18
(
c
) illustrates an HV crosstalk component CR, and FIG.
18
(
d
) illustrates a synthesized waveform of the correction current am and the HV crosstalk component CR. In FIG.
18
(
a
), the correction current am superimposed on the vertical deflection current VI is roughly illustrated. In
FIG. 18
, V indicates a vertical scanning period.
As shown in FIG.
18
(
a
), a correction current, which changes in a parabolic shape in a horizontal scanning period, is superimposed on the sawtooth vertical deflection current VI, which changes in the vertical scanning period, in order to correct an NS pincushion distortion. The polarity of the correction current am is reversed in the upper half and the lower half of a screen of a CRT, as described above. Consequently, the correction current am superimposed on the vertical deflection current VI differs in polarity in the upper half and the lower half of the vertical deflection current VI, as shown in FIG.
18
(
b
).
As shown in FI

Affiliated with

Also associated with

Rating

Vertical deflection apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Vertical deflection apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Vertical deflection apparatus will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3336559