JPH07212778A - Deflection yoke and color cathode ray tube - Google Patents

Abstract

PURPOSE:To reduce a local barrel distortion at an upper part of a screen at the start of scanning of an electron beam with a simple means by connecting an impedance element in series with an antiparallel diode pair of a vertical deflection circuit. CONSTITUTION:In the vertical deflection circuit for the deflection yoke, an inductor L being an impedance element is connected in series with anti-parallel diode pairs D1, D2 connected in parallel with a series circuit comprising a modulator M and a 2nd frame correction coil L2. The impedance of the inductor L is preferably equal to that of the parallel circuit comprising the modulator M and the frame correction coil L2. A vertical deflection current hardly flows to the diode pairs D1, D2 because the impedance of the inductor L is high at the start of scanning of an electronic beam by connecting the inductor L in series with the parallel diode pairs D1, D2 and the vertical deflection current much flows to the modulator M. Thus, local barrel distortion at an upper pat of the screen is decreased to the utmost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deflection yoke for a color cathode ray tube, and more particularly to a deflection yoke for a color cathode ray tube which vertically and horizontally deflects an electron beam from an in-line type electron gun incorporated in the color cathode ray tube.

[0002]

2. Description of the Related Art A color cathode ray tube 2 having a built-in in-line type electron gun 1 transmits an electron beam emitted from the in-line type electron gun 1 as shown in FIG. A deflection yoke 3 for deflecting in the orthogonal direction, that is, in the vertical direction and the horizontal direction is provided.

The deflection yoke 3 is formed by winding a vertical deflection coil for vertically deflecting an electron beam [RGB beam] from the in-line type electron gun 1 and a horizontal deflection coil for horizontally deflecting the electron beam. The structure is general. Here, regarding the vertical deflection by the deflection yoke 3,
Among the electron beams emitted from the in-line type electron gun 1, there is coma aberration in which the G beam is displaced from the normal position, and the deflection yoke 3 is used to correct the coma aberration.
5 includes coma correction coils L ₁ and L ₂ which are vertically positioned with respect to the in-line type electron gun 1 as shown in FIG. 5 (see FIG. 4). The illustrated coma correction coils L ₁ and L ₂ are referred to as a two-stage four-pole coma coil system,
The frame correction coil L ₁ and the second frame correction coil L ₂ are double-wound.

As described above, the vertical deflection circuit of the deflection yoke 3 which is involved in the vertical deflection of the electron beam and which has the coma correction coils L ₁ and L ₂ has a vertical deflection coil L _{V as} shown in FIG.
, A first coma correction coil L ₁ , a modulator M and a second coma correction coil L ₂ which will be described later are connected in series, and an anti-parallel diode is connected to a series circuit of the modulator M and the second coma correction coil L _2. It is constructed by connecting the pairs D ₁ and D ₂ in parallel [JP-A-1-175150].

Here, the modulator M has the following functions. That is, in the color cathode ray tube 2 comprises a frame correction coils L _1, L _2, the frame correction coils L _1, L ₂ of the characteristics, the inclination of the RB beam with respect to the horizontal direction of the screen m as shown in FIG screen A phenomenon called cross-misconvergence occurs that changes linearly from the upper end to the lower end of m. Therefore, there is a modulator M as a means for correcting this cross-miss convergence.
Although not shown, the correction of the cross miss convergence by the modulator M magnetically couples the modulator M with the horizontal deflection circuit, and the RB beam is moved from the upper end to the lower end of the screen m based on the vertical deflection current flowing in the modulator M. This is done by changing the strength of the magnetic field generated by the horizontal deflection coil as it goes.

As described above, the inclination of the RB beam, which changes linearly from the upper end to the lower end of the screen m, that is, the cross-miss convergence, is corrected by the modulator M, and the modulator M also shows the solid line in FIG. As described above, the raster distortion generated on the screen m due to the deflection of the electron beam is corrected to a small value, and finally the correct raster [shown by the broken line in the drawing] is formed by the correction circuit of the display device incorporating the color cathode ray tube 2. ing.

[0007]

In the vertical deflection circuit described above, when the electron beam scans the upper ¼ portion and the lower ¼ portion of the screen m, the anti-parallel diode pair D
_{When 1} and D ₂ are turned on, the modulator M is in a short-circuited state, and when scanning the remaining central portion, the antiparallel diode pair D ₁ and D ₂ are turned off to cause the modulator M to function and perform raster correction. Therefore, in the raster of the screen m formed by the raster correction shown in FIG. 7, only the central portion of the screen m is actually raster-corrected by the modulator M as shown in FIG. The raster distortion is not linear at the boundary between the / 4 portion and the central portion.

On the other hand, in the case where the inclination of the RB beam at the cross miss convergence is opposite to the state shown in FIG. 7 (see FIG. 10), the raster correction by the modulator M is
As shown in FIG. 11, since the raster distortion is increased in the central portion of the screen m, the raster distortion is not linear at the boundary between the upper and lower quarter portions of the screen m and the central portion. Therefore, the raster distortion becomes even larger.

When the raster correction is finally attempted to be corrected by the correction circuit of the display device, there are the following problems. In particular, when the electron beam is deflected by the deflection yoke 3 to start scanning from the upper end of the screen m as shown in FIG. 12, the impedance of the modulator M and the second coma correction coil L ₂ is high in the vertical deflection circuit. The vertical deflection current is less likely to flow in the modulator M and the second coma correction coil L ₂ . As described above, if it is difficult for the vertical deflection current to flow through the modulator M at the beginning of scanning, a local barrel distortion a occurs remarkably at the upper end of the screen m.

Therefore, the present invention has been proposed in view of the above problems, and an object thereof is to reduce local barrel distortion at the upper end of the screen by a simple means at the beginning of scanning with an electron beam. Another object of the present invention is to provide a deflection yoke for a color cathode ray tube, which is equipped with a vertical deflection circuit that can be used.

[0011]

As a technical means for achieving the above object, the present invention relates to a vertical deflection coil for vertically deflecting an electron beam from an in-line type electron gun built in a color cathode ray tube, The vertical deflection coil, the first coma correction coil, the modulator, and the second coma correction are equipped with a modulator that corrects the vertically deflected electron beam in the horizontal direction and a coma correction coil that corrects the coma aberration of the electron beam. In a vertical deflection circuit of a deflection yoke in which a coil is connected in series and an anti-parallel diode pair is connected in parallel to a series circuit of the modulator and the second coma correction coil, between the modulator and the second coma correction coil. It is characterized in that an impedance element is inserted and connected in series with an anti-parallel diode pair connected in parallel.

It is desirable that the impedance element is an inductor, and further, it is preferable that the impedance element has substantially the same impedance as a series circuit of the modulator and the second coma correction coil.

[0013]

In the deflection yoke for a color cathode ray tube according to the present invention, since the impedance element is inserted and connected in series with the antiparallel diode pair, a vertical deflection current flows through the antiparallel diode pair by the impedance element at the start of scanning the electron beam. This makes it easier for vertical deflection current to flow in the modulators connected in parallel. This causes raster distortion from the top edge to the bottom edge of the screen, especially the upper quarter of the screen.
The raster distortion from the portion to the central portion can be changed linearly, and the local barrel distortion at the upper end of the screen can be reduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a deflection yoke for a color cathode ray tube according to the present invention will be described with reference to FIGS. The same parts as those in FIGS. 4 to 12 are designated by the same reference numerals, and a duplicate description will be omitted.

The feature of the present invention is that, in the vertical deflection circuit of the deflection yoke 3 as shown in FIG.
The inductor L, which is an impedance element, is inserted and connected in series to the anti-parallel diode pair D ₁ and D ₂ which are connected in parallel to the series circuit with the coma correction coil L ₂ . In addition, it is desirable that the inductor L has an impedance that is substantially the same as that of a series circuit of the modulator M and the second coma correction coil L ₂ .

In the vertical deflection circuit of the present invention, the inductor L is inserted and connected in series to the anti-parallel diode pair D ₁ and D ₂ , so that the impedance of the inductor L is high at the start of scanning of the electron beam, so that the anti-parallel diode is connected. Since it becomes difficult for the vertical deflection current to flow in D ₁ and D ₂ ,
The vertical deflection current can flow through the modulator M more easily than in the conventional case.

As a result, as shown in FIG. 2, the raster distortion from the upper end to the lower end of the screen m, particularly the upper 1/1 of the screen m.
Raster distortion from the four parts to the central part can be changed linearly as compared with the conventional product [shown by the broken line]. As a result, when a raster is finally formed by the correction circuit of the display device incorporating the color cathode ray tube 2, as described above, the raster distortion is from the upper end to the lower end of the screen m, particularly the upper end of the screen m. Since it changes linearly from the center to the center [see FIG. 2], the local barrel distortion a [see FIG. 12] at the upper end of the screen m as shown in FIG. 3 should be minimized. And a proper raster can be obtained.

[0018]

According to the deflection yoke for a color cathode ray tube according to the present invention, the impedance element is connected in series to the anti-parallel diode pair of the vertical deflection circuit, so that at the beginning of the scanning of the electron beam, the local area at the upper end of the screen is locally generated. Barrel distortion can be made as small as possible, cross misconvergence can be improved, and a proper raster can be formed, which is of great practical value.

[Brief description of drawings]

FIG. 1 is a vertical deflection circuit diagram showing an embodiment of a deflection yoke for a color cathode ray tube according to the present invention.

FIG. 2 is a front view of a screen showing a raster correction state by the vertical deflection circuit of the present invention.

FIG. 3 is a front view of a screen showing a state where the raster of FIG. 2 is corrected by a correction circuit of a display device.

FIG. 4 is a side view showing a deflection yoke mounted on a color cathode ray tube.

FIG. 5 is a front view showing a coma correction coil included in a deflection yoke.

FIG. 6 is a vertical deflection circuit diagram showing a conventional deflection yoke for a color cathode ray tube.

FIG. 7 is a front view of a screen showing cross miss convergence.

FIG. 8 is a front view of a screen schematically showing a state of raster correction by a modulator of a vertical deflection circuit.

FIG. 9 is a front view of a screen specifically showing a state of raster correction by a modulator.

FIG. 10 is a front view of a screen showing a cross miss convergence opposite to that of FIG. 7;

11 is a front view of a screen showing a state of raster correction by a modulator based on the inverse cross-misconvergence of FIG.

FIG. 12 is a front view of a screen showing a state in which the raster distortion of FIG. 11 is corrected by a correction circuit of a display device and a local barrel distortion is generated.

[Explanation of symbols]

1 in-line type electron gun 2 color cathode ray tube 3 deflection yoke M modulator L impedance element [inductor] L _V vertical deflection coil L ₁ first coma correction coil L ₂ second coma correction coil D ₁ , D ₂ anti-parallel diode pair

Claims (3)

[Claims] 1. A vertical deflection coil for vertically deflecting an electron beam from an in-line type electron gun built into a color cathode ray tube, a modulator for horizontally correcting the vertically deflected electron beam, and a coma of the electron beam. A coma correction coil for correcting aberrations is provided, and the vertical deflection coil, the first coma correction coil, the modulator and the second coma correction coil are connected in series, and the modulator and the second coma are also connected.
In a vertical deflection circuit of a deflection yoke in which an antiparallel diode pair is connected in parallel to a serial circuit with the coma correction coil, an impedance element is connected in series to the antiparallel diode pair connected in parallel between the modulator and the second coma correction coil. A deflection yoke for a color cathode ray tube, characterized in that the deflection yoke is inserted into and connected to the. 2. A deflection yoke for a color cathode ray tube, wherein the impedance element according to claim 1 is an inductor. 3. A deflection yoke for a color cathode ray tube, wherein the inductor according to claim 2 has an impedance substantially equal to that of a series circuit of a modulator and a second coma correction coil.