JPH0794093A - Deflector for color cathode-ray tube - Google Patents

Abstract

PURPOSE:To minimize the landing error by a leaked magnetic field of a deflection yoke and prevent the deterioration of color purity by changing the inductance of each impedance coil in accordance with the absolute value of a vertical deflecting current. CONSTITUTION:When a deflecting current IV in a direction 45 is carried to a vertical deflection coil 29 when an electron beam is deflected to the upper part of a screen, a full rectified vertical deflecting current is carried to a magnetic coil 40 through a variable resistor 39 and a rectifier circuit 23. Consequently, a magnetic flux V in a direction 46 is generated in a pair of saturable cores 37a, 37b, and a magnetic flux L in directions 47a, 47b is generated in a pair of impedance coils 38a, 38b connected to a horizontal defection coil 27. The intensity of a composed pin cushion-like magnetic field obtained by two sets of sub-coils 21, 22 can be dynamically changed synchronously with the scanning period in the screen vertical direction. Namely, the inductance of each coil 38a, 38b can be changed in accordance with the absolute value of the vertical deflecting current.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a deflecting device for a color cathode ray tube, and more particularly to a deflecting device for a color cathode ray tube which is effective for high definition and high color purity of a color display tube.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 6, a color cathode ray tube has an envelope composed of a panel 1 and a funnel-shaped funnel 2 integrally joined to the panel 1, and an inner surface of the panel 1 has an envelope. A phosphor screen 3 including a dot-shaped or stripe-shaped three-color phosphor layer that emits blue, green, and red is formed, and a shadow mask 4 is arranged inside and facing the phosphor screen 3. . On the other hand, in the neck 5 of the funnel 2, the three electron beams 6B, 6G,
The electron gun 7 that emits 6R is sealed. An internal magnetic shield 9 attached to the mask frame 8 of the shadow mask 4 is arranged inside the large-diameter portion of the funnel 2. Then, the three electron beams 6B, 6G, 6R emitted from the electron gun 7 are deflected by the magnetic field generated by the deflection yoke 10 mounted outside the funnel 2, and the phosphor screen 3 is horizontally and vertically scanned. By doing
It has a structure for displaying a color image.

The internal magnetic shield 9 is an electron beam 6B.
, 6G, 6R to prevent the influence of the external magnetic field, and the earth magnetism can be shielded almost sufficiently to prevent the influence. However, the shielding ability of the internal magnetic shield 9 can shield a relatively weak magnetic field such as the earth's magnetism, but the magnetic field leaking from the deflection yoke 10, particularly the tube axis (Z axis) direction component thereof, It is difficult to shield it sufficiently.

Generally, the influence of the leakage magnetic field from the deflection yoke is greater in the horizontal deflection coil extending to the front end portion of the deflection yoke than in the vertical deflection coil. Moreover, a magnetic field mainly composed of the tube axis direction component leaks from the front portion of the horizontal deflection coil. The tube axis direction component of this leakage magnetic field has almost no effect on the undeflected electron beam,
It acts on the electron beam deflected to the peripheral parts such as the upper and lower ends of the screen, the left and right ends, and the diagonal ends, and as shown in FIG. 7 for the dot-shaped phosphor layer, it does not affect the phosphor layer 13 in the peripheral part of the screen 12. On the other hand, the electron beam 6 (6B, 6G, 6R) is displaced to the outside in the horizontal direction, and a landing error occurs.

A phosphor screen of a color cathode ray tube is usually formed by a photographic printing method, and a pattern of electron beam passage holes of a shadow mask is printed on a screen forming member layer such as a phosphor slurry layer applied and formed on the inner surface of the panel. At the time of (exposure), a correction lens that approximates the trajectory of light to the trajectory of an electron beam is used. However, in reality, even if such a correction lens is used, accurate beam landing cannot be obtained due to the design margin of the lens curved surface, manufacturing error, and the like. Therefore, in forming a phosphor screen of a color cathode ray tube, a landing margin of about 20 μm is provided between the phosphor layer and the beam spot so that the electron beam can still land on the predetermined phosphor layer even if the beam landing is deviated. Is provided.

However, it is difficult to correct the landing error that displaces the electron beam outward in the horizontal direction with respect to the phosphor layer in the peripheral portion of the screen described above by the lens curved surface of the correction lens. In order to properly land on the body layer, this kind of beam landing deviation needs to be corrected by another method.

On the other hand, with the recent enlargement of color cathode ray tubes, the deflection yoke also becomes larger, and the magnetic field leaking from the front end of the deflection yoke tends to have a greater effect on the electron beam. Also, in recent high-definition color cathode-ray tubes, the arrangement pitch of the phosphor layers is about 0.26 mm, which is smaller than that of ordinary color cathode-ray tubes, and as a result, the landing margin must be reduced and the color purity is degraded. There is a problem that it easily occurs.

[0008]

As described above, in the conventional color cathode ray tube, an internal magnetic shield is provided inside the large-diameter portion of the funnel in order to prevent the influence of the external magnetic field such as the earth magnetism on the electron beam. Has been. However, it is difficult to sufficiently shield the magnetic field leaking from the deflection yoke by this internal magnetic shield, and in particular, due to the tube axis direction component of the magnetic field leaking from the front end of the horizontal deflection coil, the fluorescent layer in the peripheral portion of the screen is On the other hand, the electron beam is displaced outward in the horizontal direction, and landing error occurs. Moreover, the landing error due to the leakage magnetic field of the deflection yoke becomes larger as the deflection yoke tube becomes larger, and the magnetic field leaking from the front end portion of the deflection yoke tends to have a large influence on the electron beam. Further, in recent high-definition color cathode-ray tubes, the arrangement pitch of the phosphor layers is smaller than that of a normal color cathode-ray tube, and accordingly, the landing allowance must be reduced, and there is a problem that the color purity is likely to deteriorate. .

The present invention has been made in view of the above problems, and it is an object of the present invention to reduce the landing error due to the leakage magnetic field of the deflection yoke and prevent the deterioration of the color purity.

[0010]

In a deflection device for a color cathode ray tube, a bipolar magnetic field having different polarities is supplied to a rear end portion of a deflection yoke having horizontal and vertical deflection coils by supplying a horizontal deflection current flowing through the horizontal deflection coil. A saturable core that is magnetically biased until just before saturation, a pair of impedance coils wound around the saturable core as a magnetic core, a pair of impedance coils and two sets of sub-coils are respectively provided. It has an impedance coil parallel circuit in which a pair of series circuits connected in series are connected in parallel to a horizontal deflection coil, and a magnetic coil wound around a saturable core and connected to a vertical deflection coil through a rectifying circuit. , The vertical deflection current of the vertical deflection coil that is rectified by the rectification circuit and supplied to the magnetic coil Magnetic flux of opposite phase is generated between the winding part of the impedance coil and the winding part of the other impedance coil, and the current flowing through the two sets of sub-coils is differentially generated by the magnetic flux of the opposite phase in synchronization with the vertical deflection current. A saturable reactor that changes to

[0011]

With the above-described structure, the inductance of each impedance coil can be changed in synchronization with the absolute value of the vertical deflection current, and the change in the inductance of each impedance coil causes a change in the current flowing through one subcoil. The current flowing through the other sub coil can be changed differentially. As a result, a dipole magnetic field in the same direction as the horizontal deflection magnetic field generated by the horizontal deflection coil is generated in one subcoil, and a dipole magnetic field in the opposite direction is generated in the other subcoil. Then, the intensity of the bipolar magnetic field generated by these two sets of sub-coils changes with the increase of the absolute value of the vertical deflection current, and a horizontal force is applied to the electron beam from the center of the screen toward the peripheral portion in the vertical direction. Exert. As a result, the horizontal displacement of the electron beam due to the leakage magnetic field of the deflection yoke can be corrected.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the drawings.

FIG. 2 shows a deflecting device for an in-line type color cathode ray tube which is one embodiment of the present invention, and FIG. 1 shows its configuration in a circuit diagram. This deflecting device includes a deflecting yoke 20 mounted on the outside of the funnel of a color cathode ray tube, two sets of subcoils 21 and 22, a rectifying circuit 23, and a saturable reactor 24.

The deflection yoke 20 has a saddle type horizontal deflection coil 27 vertically symmetrically arranged inside a mold 26.
And a toroidal vertical deflection coil 29 wound around the core 28 and vertically symmetrically arranged on the outside of the mold 26 to generate a pincushion type horizontal deflection magnetic field and a barrel type vertical deflection magnetic field, respectively. ing.

With respect to the deflection yoke 20, the two sets of sub-coils 21 and 22 are each provided with a vertical axis (Y
A pair of rod-shaped cores 31a vertically symmetrically arranged on the axis
, 31b and coils 32a, 32b and 33a wound in series around the pair of cores 31a, 31b, respectively.
, 33b, which are vertically symmetrical. The sub-coils 21 and 22 are connected to a horizontal deflection coil 27 via impedance coils of a saturable reactor 24, which will be described later, respectively, and by supplying a horizontal deflection current flowing through the horizontal deflection coil 27, one of the sub-coils 21 is
The horizontal deflection magnetic field generated by the horizontal deflection coil 27 generates a two-pole magnetic field in the same direction, and the other sub-coil 22 generates a two-pole magnetic field in the opposite direction to the rear end side of the deflection yoke 20. .

The rectifying circuit 23 connects the four rectifying elements 35 in a bridge shape and full-wave rectifies the sawtooth-shaped vertical deflection current flowing through the vertical deflection coil 29.

The saturable reactor 24 comprises a pair of saturable cores 37a and 37b arranged in parallel and one saturable core 3
7a is wound as a magnetic core, and the one sub coil 21 is wound.
And a pair of impedance coils 38a, which are wound in series with the other saturable core 37b as a magnetic core and are connected in series to the other sub-coil 22 described above.
, 38b and this pair of impedance coils 38a
, 38b connected in parallel to each other, the impedance coil parallel circuit connected to the horizontal deflection coil 27 and the pair of saturable cores 37a, 37b wound around the rectifier circuit 23 and the variable resistor 39 connected in parallel. And a magnetic coil 40 connected to the vertical deflection coil 29 via the.

The pair of saturable cores 37a, 37b of the saturable reactor 24 have magnets 41 arranged at both ends so as to operate in a non-linear region, and the magnets 41 are magnetically biased until just before saturation. Has become. Also, a pair of impedance coils 38a, 3
8b is a current I flowing through the subcoils 21 and 22, respectively.
In order to reduce the change in inductance due to the influence of 21, I22, two coils 42a connected in series with opposite polarities,
42b, 42c and 42d.

Next, the operation of this deflecting device will be described.

Now, assuming that the electron beam is deflected upward in the screen, and a vertical deflection current IV in the direction of arrow 45 flows in the vertical deflection coil 29, the magnetic coil 40 is adjusted by the variable resistor 39, and the rectifier circuit 23 is adjusted. A full-wave rectified vertical deflection current flows. As a result, a magnetic flux φV in the direction of arrow 46 is generated in the pair of saturable cores 37a and 37b. Simultaneously with the pair of impedance coils 38a, 38b connected to the horizontal deflection coil 27, arrows 47a, 47
A magnetic flux φL in the b direction is generated. Due to these φL, the magnetic flux in the saturable core 37a becomes φV + φL, and the magnetic flux in the saturable core 37b becomes φV−φL, and the inductance of the impedance coil 38a is relatively small and the inductance of the impedance coil 38b is relatively large.

Also when the electron beam is deflected to the lower part of the screen, a vertical deflection current adjusted by the variable resistor 39 and full-wave rectified by the rectifying circuit 23 flows through the magnetic coil 40, and a pair of impedance coils 38a, The inductance of 38b changes in the same manner as when the screen is deflected upward, and similar magnetic fluxes .phi.V + .phi.L and .phi.V-.phi.L are generated in the pair of saturable cores 37a, 37b.

Therefore, according to this deflecting device, two sets of the sub-coil 21, are synchronized with the scanning cycle in the vertical direction of the screen.
The currents I21 and I22 flowing through 22 change as shown by curves 49 and 50 in FIGS. 3 (a) and 3 (b). Therefore, as shown in FIG.
When the electron beams 51B, 51G, 51R are deflected to the left side of the screen, a dipole magnetic field 52 is generated in one subcoil 21, and a dipole magnetic field 53 is generated in one subcoil 22 as shown in FIG. Further, when the light is deflected to the right side of the screen, a bipolar magnetic field in the opposite direction to that when the light is deflected to the left side of the screen is generated. The strength Bab of the combined pincushion type magnetic field obtained by these two sets of subcoils 21 and 22 is strong at the upper and lower ends of the screen, becomes zero at the center of the screen, and the horizontal deflection coil 27 is generated, as shown by the curve 54 in FIG. In the same direction as the pin-cushion type horizontal deflection magnetic field.

Therefore, when the electron beam is deflected to the diagonal portion of the screen, the intensity Bab of the pincushion type magnetic field obtained by the two sets of subcoils 21 and 22 is larger than that when the electron beam is deflected to the horizontal axis end of the screen. When the position of the deflection yoke is adjusted to optimize the landing at the screen horizontal axis end, the landing at the diagonal part of the screen that shifts outward in the horizontal direction with respect to the phosphor layer can be achieved. The gills can be eliminated.

That is, in the deflecting device of this example, two sets of subcoils 21 and 2 are synchronized with the scanning cycle in the vertical direction of the screen.
The strength of the synthetic pincushion type magnetic field Bab obtained by 2.
Can be dynamically changed, and
When adjusting the position of the deflection yoke so that the landing at the screen horizontal axis end is optimal, it is possible to correct the landing error that shifts outward in the horizontal direction with respect to the phosphor layer that occurs at the diagonal part of the screen, and is saturable. By adjusting the operating point of the reactor 24 with the variable resistor 39 connected in parallel to the magnetic coil 40, the landing error can be corrected very easily.

[0025]

EFFECTS OF THE INVENTION By supplying a horizontal deflection current flowing through the horizontal deflection coil to the rear end of a deflection yoke having horizontal and vertical deflection coils, two-pole magnetic fields having different polarities are generated.
A set of sub-coils is provided, and a saturable core that is magnetically biased until just before saturation, a pair of impedance coils wound around the saturable core as a magnetic core, and the pair of impedance coils and two sets of sub-coils are connected in series. A rectification circuit having an impedance coil parallel circuit in which a pair of series circuits are connected in parallel and connected to a horizontal deflection coil, and a magnetic coil wound around a saturable core and connected to a vertical deflection coil through a rectification circuit. By the vertical deflection current of the vertical deflection coil that is rectified by and supplied to the magnetic coil, magnetic flux of opposite phase is generated in the winding portion of one impedance coil of the saturable core and the winding portion of the other impedance coil. A saturable reactor that differentially changes the current flowing in two sets of subcoils by magnetic flux of opposite phase in synchronization with the vertical deflection current If it is provided, the inductance of each impedance coil can be changed in synchronization with the absolute value of the vertical deflection current, and the change in the inductance of each impedance coil can change the current flowing in one subcoil and the current flowing in the other subcoil. It can be changed differentially. As a result, a dipole magnetic field in the same direction as the horizontal deflection magnetic field generated by the horizontal deflection coil is generated in one sub coil, and a dipole magnetic field in the opposite direction is generated in the other sub coil. The intensity of the magnetic field generated by the two sets of subcoils changes as the absolute value of the vertical deflection current increases, and exerts a horizontal force on the electron beam from the center of the screen toward the peripheral portion in the vertical direction. As a result, the horizontal displacement of the electron beam from the leakage magnetic field of the deflection yoke can be corrected, and the landing characteristic of the color CRT can be improved.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing the configuration of a color cathode ray tube deflecting device according to an embodiment of the present invention.

FIG. 2 is a diagram showing an arrangement of the deflection yoke and two sets of subcoils.

FIG. 3A and FIG. 3B are diagrams showing the relationship of currents flowing in two sets of subcoils.

FIG. 4 (a) and FIG. 4 (b) are diagrams showing directions of a bipolar magnetic field generated by two sets of subcoils.

FIG. 5 is a diagram showing the strength of a magnetic field obtained by synthesizing dipole magnetic fields generated by two sets of subcoils.

FIG. 6 is a diagram showing a configuration of a color CRT.

FIG. 7 is a diagram showing horizontal displacement of electron beams in the horizontal direction with respect to the three-color phosphor layer.

[Explanation of symbols]

 20 ... Deflection yoke 21 ... Sub-coil 22 ... Sub-coil 23 ... Rectifier circuit 24 ... Saturable reactor 27 ... Horizontal deflection coil 28 ... Core 29 ... Vertical deflection coil 31a, 31b ... Core 32a, 32b ... Coil 33a, 33b ... Coil 37a, 37b ... saturable cores 38a, 38b ... impedance coil 39 ... variable resistor 41 ... magnets 51B, 51G, 51R ... 3 electron beam 52 ... dipole magnetic field 53 ... dipole magnetic field

Claims (1)

[Claims] 1. A deflection yoke having horizontal and vertical deflection coils, and a deflection yoke which is arranged at a rear end portion of the deflection yoke and generates a bipolar magnetic field having polarities different from each other by supplying a horizontal deflection current flowing through the horizontal deflection coil. A pair of sub-coils, a rectifier circuit connected to the vertical deflection coil, a saturable core that is magnetically biased until just before saturation, a pair of impedance coils wound around the saturable core as a magnetic core, and a pair of impedance coils. And an impedance coil parallel circuit in which a pair of series circuits in which the two sets of sub-coils are respectively connected in series are connected in parallel and connected to the horizontal deflection coil, and through the rectifier circuit wound around the saturable core. A magnetic coil connected to the vertical deflection coil, rectified by the rectifying circuit, and supplied to the magnetic coil; By the vertical deflection current of the vertical deflection coil, a magnetic flux of opposite phase is generated between the winding portion of one impedance coil and the winding portion of the other impedance coil of the saturable core. And a saturable reactor that differentially changes the current flowing through the sub-coil in synchronization with the vertical deflection current.