KR960000348B1 - Picture display device - Google Patents

Abstract

Picture display device having a display tube (3) and a deflection unit (9) comprising a field deflection coil and a line deflection coil (11). To comply with a predetermined interference radiation standard, the picture display device comprises a first set of (horizontal) interference suppression coils 18, 19 arranged symmetrically relative to the plane of symmetry of the line deflection coil and a further set of (vertical) interference suppression coils 18a, 19a arranged at right angles to the plane of symmetry of the line deflection coil, which coils are oriented in such manner and in operation are energizable in such manner that, measured at a predetermined distance from the picture display device, at least the strength of the local magnetic dipole field is below a desired standard. Each coil of the further set preferably comprises at least two sub-coils arranged parallel to each other at a given distance in order to reduce the energy content of the coil system.

Description

Image display apparatus having means for compensating for the line stray field

1A is a front perspective view of an image display device having a display tube.

1B is a schematic diagram illustrating an electromagnetic deflection unit having a line deflection coil.

2 is a rear perspective view of a display tube on which two sets of compensation coils are mounted.

3 is a schematic diagram showing a combination of two compensation coil sets and a coil representation in cross section.

4 is a rear perspective view of a display tube having a single compensation coil set and a double compensation coil set.

5 is a schematic plan view showing a half compensation coil with three windows.

* Explanation of symbols for main parts of the drawings

1: neck 7: electron gun system

9 electromagnetic deflection unit 11 line deflection coil

18a, 19a: vertically arranged interference coil 18,19: horizontally arranged interference coil

22,23: compensation coil 26: deflection coil

The present invention relates to an image display device having a display tube having a rear end and a front end, and an image display fluorescent screen, wherein the rear end of the display tube is composed of a cylindrical neck for receiving a device for generating an electron beam, and the front end is a front portion. The widest funnel-shaped display device also includes an electron beam with an electromagnetic deflection unit, the deflection unit having a line deflection coil which generates a magnetic field having at least one dipole component when powered. Field deflection coils.

Recently, more stringent standards have been introduced for some forms of image display devices, in particular monitors, in relation to the magnetic interference fields generated by them. Until now, protective shields such as metal envelopes for combination of display tubes and deflection units have been used in image display devices, but such protective shields influence the external field on the display device rather than slow down the magnetic interference field generated by the image display device. The purpose was to stop. An important source of magnetic interference fields is line deflection coils. This is because line deflection coils operate at radio frequency currents (frequency in the range of 10 to 100 Hz) as opposed to field deflection coils. It is not possible to design a deflection coil that works well without generating a stray field. If the stray field is removed by a protective shield, such a shield will only be effective if the combination of the display tube and the deflection unit is also shielded on the display screen side.

It is an object of the present invention to obtain the required emission standard without the use of shielding means. According to the invention, in the image display apparatus of the type described in the opening paragraph, the object is realized by the provision of the device compensation coil system, which compensates at least a local magnetic dipole field when measured at a distance from the image display apparatus. The strength is oriented in such a way that the intensity is below the desired reference value and in operation in this way, the compensation coil system is arranged symmetrically with respect to the plane of symmetry of the line deflection coil on the outside of the deflection unit and the major part of the length This set of axially extending first compensation coils and two other compensation coils arranged symmetrically with respect to the plane of symmetry of the line deflection coil on the outside of the deflection unit and extending at least substantially parallel to the display screen.

It is based on the recognition that it is sufficient to compensate only the dipole component for suppressing the interference of the magnetic field at a long distance (e.g., more than 3 m) from the interference source of the present invention. The deflection unit also generates larger orders of magnitude (e.g. 6 poles and 10 poles) of the magnetic deflection field component, but its strength decreases much faster than the strength of the dipole component with increasing distance, so the effect is approximately 50 cm. Ignore it already on the street. The magnetic dipole moment of the interference source (line deflection coil) can be compensated for by adding the opposite dipole moment. This dipole moment can be obtained by powering two current loops located outside of the line deflection coil and extending at least two major portions of length at least substantially parallel to the display axis on the opposite side. The current loop has the required number of turns, the required surface area and the required orientation. The power supply can be effective by arranging the compensation coil configured by the current loop in series or in parallel with the line deflection coil.

The compensation coil preferably covers as wide a surface area as possible. The larger the surface area, the smaller the energy required to generate the desired magnetic dipole moment. For example, a surface area of 1 to 10 dm 2 is known to be suitable for implementation.

The number of turns of the compensation coil can be small (less than 10). In many cases, two to six players will suffice. In order to reduce the interference field at a distance of approximately 50 cm, the compensation coil system according to the invention is provided with two additional compensations arranged on the outer surface of the deflection unit symmetrically about the plane of symmetry of the line deflection coil and extending parallel to the display screen. It includes a coil. During operation these coils supply power in the same way as the first compensation coil.

As mentioned above, the compensation coil must be large to reduce the energy capacity.

However, various types of display devices (particularly monitors) have a problem in that they lack a space for accommodating a large coil system at a correct position. Radial compensation consumes a lot of (line deflection) energy since eventually a relatively small (very small) compensation coil has to be used. The space required for the coils arranged parallel to the display screen is mostly very small.

In a preferred embodiment of the image display device according to the present invention, the problem is reduced as each of the two additional compensation coils includes at least two sub coils arranged in parallel at a predetermined distance. The effect is described later.

The first compensation coil may be formed by a current loop with windings in about the same plane parallel to the plane of symmetry of the line deflection coil. However, the embodiment is formed of a saddle coil mounted outside of the electromagnetic deflection unit. In particular, if the saddle coil is a so-called yoke winding type, ie wound on a support, the two main portions of its length can be formed in an axially extending manner on opposite sides of the display tube axis. The two main parts together with the connecting parts at their ends define at least two coil windows of different sizes. By adjusting the surface area of the window (and thus the entire “effective” coil surface), it is possible to adapt the compensation dipole field to the stray field of each line deflection coil in combination with the first compensation coil.

The invention will be explained in more detail with reference to the accompanying drawings.

FIG. 1A is a perspective view of a combination of a deflection unit and a display tube disposed in the cabinet 2, which may be provided with means for compensating for the interference field according to the present invention. All details that are not important to the understanding of the present invention have been omitted for clarity.

The display tube has a cylindrical net 1 and a funnel portion 3, the widest portion of the funnel portion being in front of the display tube and including a display screen (not shown).

The display screen includes a phosphor that is bombarded by electron luminescence of a predetermined color. The rear of the neck 1 houses an electron gun system 7 (shown schematically). In the electrical region between the neck 1 and the rake 3, an electromagnetic deflection unit 9, schematically illustrated, is arranged on the display tube, in which the line deflects the electron beam, in particular in the horizontal direction X. Deflection coil 11 (FIG. 1B). As schematically shown in FIG. 1B, the line deflection coil 11 may consist of, for example, two saddle coils that are equally divided. In operation, a sawtooth current flows through these coils with a frequency between 10 and 100 Hz, for example approximately 6 Hz. In general, the line deflection coil 11 is surrounded by an annular core element 10 of a soft magnetic material, ie a so-called yoke ring, which is shown in broken lines in FIG. 1b.

When the radiation field of a deflection coil with a yoke ring initially reverses the direction of the radiation field of a coil without a yoke ring but is the same size, the line deflection coil can be assumed to be a current loop with a predetermined moment over a large distance. .

The field Bo at the center of the line deflection coil without the yoke ring can be calculated to be approximately 30 gauss. The field of the actual deflection coil with the yoke ring is approximately twice that value.

The line deflection coil field at 1m distance is 1m Gaussian.

This radiating field may be compensated for by a secondary loop current with a low radius and a large radius where the magnetic moment is equal to the magnetic moment of the coil itself. Such auxiliary loop current can be generated by a compensation loop having a radius Rc = 20 cm and a winding number Nc = 4. In this way, attenuation of 40 dB can be realized, for example, at a distance of 3 m and more from the radiation source. The compensation loop should be oriented such that the magnetic dipole moment generated on the current path passing through the coil at a certain distance (eg 3 m) compensates for the magnetic dipole moment of the interference component. To achieve this goal, the dipole moment of the compensation loop must be parallel and vice versa with the dipole moment of the interference component. The interference component is primarily a line deflection coil. However, a line output transformer can also be considered an interference component because it can generate an interference field. However, a line output transformer can also be considered an interference component because it can generate an interference field. In that case the following applies:

Parallel dipole moments generated from one or more components can be compensated with one current loop. The antiparallel dipole moment can be compensated by one loop when the frequency and phase of the dipole moment being compensated for are the same.

Therefore, the magnetic strain of a device comprising a large number of direct interferers (line output stages, deflection coils) and a large number of interfering interferers (reflectors, base plates) with the help of a limited number of windings and compensation loops having a predetermined diameter. The field can be compensated.

By lowering the number of turns and selecting a large surface area, the following conditions can always be met.

The magnetic dipole moment vector is equal to the sum of the dipole moments of all direct interfering sources in the above device.

2. There is very little concern about the load and components of the power supply, especially in the deflection coils themselves.

2 shows a deflection unit having two sets of interference coils, ie horizontally arranged sets 18, 19 and vertically arranged sets 18a, 19a. By selecting the number of turns of the vertically arranged set differently from the number of turns of the horizontally arranged set and correctly selecting the size and current direction of the set of horizontally arranged sets, considerable field attenuation can be realized at a distance of approximately 50 cm. Can be. As long as the current direction is correctly selected, this means that when power is supplied to the interference suppression coil system, the current in the horizontally arranged portion flows in the same direction as the current in the corresponding (axis) portion of the line deflection coil, It is particularly meant that the current in the part flows in a direction opposite to the direction of the corresponding (lateral) part of the line deflection coil.

The operation of the coil arrangement of FIG. 2 will be described with reference to FIG. The interference field of the deflection coil 26 can be assumed to be roughly the dipole or coil 21 in the display tube 27. Compensation is performed by coils 22 and 23 arranged symmetrically with respect to the plane of symmetry of the line deflection coil of the deflection unit 26. However, due to the distance ΔY1 between the coils 22 and 23, a six-pole component is generated, and a four-pole component is generated because of the distance ΔX. If the coils 22 and 23 are moved in the forward direction (the direction in which ΔX decreases to decrease 4 poles), ΔY1 increases to increase 6 poles as well. For this reason, DELTA Y1 is kept small, and the six poles can be slightly reduced by enlarging the diameters of the coils 22 and 23, and as a result, DELTA X increases because it cannot be inserted into the display tube of the coils. Four poles proportional to the size of the coil, the current through the coils and the distance ΔT2 are mainly generated by the two vertical coils 24 and 25. The four and six poles can be neutralized by the correct combination of coil size and current strength. All coils with respect to 8 poles The coils should not be large because 8 poles and more poles begin to act when the 8 pole coils tangential to the source.

As noted earlier, it is important to have a large size interference suppression coil in relation to the energy consumption of the coils. If this is not possible, the present invention provides a solution for constructing a coil of a system arranged perpendicularly to the plane of symmetry of the line deflection coil from at least two sub coils (28a and 28b, 29a and 29b, respectively shown in FIG. 4). to provide. By arranging each pair of sub coils at a predetermined distance ΔZ, mutual inductance can be minimized. In the case of two sub-coils, each sub-coil stack may have half the number of turns required for a single coil. This means that the inductance of a system with two pairs of sub coils can be half the inductance of a single coil set. As a result, the energy capacity is reduced.

The saddle coils 18, 19 may be of the so-called yoke winding type. This means that the saddle coil is wound directly on the support. Such a support may comprise, for example, a flange with two grooves which are secured to the front and rear of the deflection unit. The position of the winding portion extending in the axial direction can be fixed by the groove. For use in several deflection units, for example, a common flange (having a uniformly distributed groove around it) can be used to wind compensating coils having two or more coil windows of different sizes. In this way, a 'valid' compensation coil surface area can be applied to each line deflection coil to which the compensation coil is coupled. 5 is a schematic plan view of a half 30 of a compensating saddle coil with three coil windows 31, 32 and 33 of different sizes.

Claims (5)

The rear end is composed of a cylindrical net 1 for receiving a device for generating an electron beam, and the front end 3 is a funnel-shaped display tube with the widest front, an image display fluorescent screen, and a line deflection coil 11. And an electromagnetic deflection unit mounted around the display tube for deflecting the electron beam across the display screen, the coil comprising an electromagnetic deflection unit that generates at least one dipole component when powered. An image display device comprising: a compensation in which the image display device is oriented in such a manner that the strength of the local magnetic dipole field measured at a point away from the device is less than or equal to a predetermined reference value, and power is supplied during operation in such a manner. Further comprising a coil system, wherein the compensation coil system is external to the deflection unit; A set of first compensation coils 18, 19 symmetrically arranged with respect to the plane of symmetry of the axially extending main portion of the length, and symmetrical with respect to the plane of symmetry of the line deflection coil on the outer surface of the deflection unit. And two different compensation coils (18a, 19a) arranged in parallel to and extending parallel to the display screen. An image display apparatus according to claim 1, wherein each of the two different compensation coils comprises at least two sub coils (28a, 28b, 29a, 29b) arranged in parallel at a predetermined distance ΔZ. An image display apparatus according to claim 1 or 2, wherein each of said first compensation coils comprises a saddle-shaped coil mounted inside an electromagnetic deflection unit. 4. The method of claim 3, wherein each saddle coil is defined by at least two coil windows of different sizes and is bounded by two main portions parallel to the display tube axis and two connecting portions connecting the two main portions. An image display device, characterized in that. The image display device according to claim 4, wherein the saddle coil is a yoke winding type.

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