JPH01207789A - In-line type deflection york for color picture tube - Google Patents

Abstract

PURPOSE:To switch the correction of coma aberration (VCR) and to resolve a correction lack on a vertical axis end by forming a 1st current control system constituted of a pair of subcoils out of two pairs and a pair of diodes connected in parallel with reverse polarity and connecting a 2nd current control system consisting of a serial circuit constituted of a resistor and a choke coil in parallel with the 1st current control system. CONSTITUTION:The subcoils 1a, 1b of upper and lower U-shaped cores generate a pin cushion magnetic field in the same direction as a vertical deflection coil magnetic field and the subcoils 2a, 2b of right and left rod-shaped cores generate a barrel magnetic field in the reverse direction against the vertical deflection coil magnetic field. In both the upper and lower and right and left subcoils, their magnetic fields are applied to a center beam stronger than side beams to correct VCR. Consequently, vertical deflection current flowing into the right and left subcoils 2a, 2b is suddenly increased from a part corresponding to the leading edge part of a diode pair 3 and VRT correction lack which may be generated by adding VCR correction based upon the right and left subcoils 2a, 2b to VCR correction based upon the upper and lower subcoils 1a, 1b can be resolved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a deflection yoke for an in-line color picture tube suitable for use as a deflection yoke for, for example, a high-resolution color display tube.

(Prior Art) In general, a color picture tube with an in-line electron gun is characterized by making the magnetic field of the deflection yoke non-uniform.
It has a so-called self-convergence function in which the three electron beams are made substantially coincident over the entire screen by only the combination of the color picture tube and the deflection yoke without using any external circuit correction means.

In such an in-line color picture tube, the sixth
As shown in the figure, the horizontal deflection magnetic field is
7. By using the parallel magnetic field 18 as the vertical deflection magnetic field, there is an advantage that convergence between both side beams (R, B) can be achieved without an external correction circuit.

However, because a non-uniform magnetic field is used as mentioned above, there is a so-called coma aberration in which the deflection sensitivity to the center beam (G) is worse than the deflection sensitivity to both side beams, and the image on the screen is shown in Figure 7. It appears as a pattern.

That is, HCR is the coma aberration on the horizontal axis (x), and HCR is the coma aberration on the horizontal axis (x), and
If the coma aberration of is VCR, then a normal 14 inch 90°
Even in tubes, HCR is about 0.5 mm, VCR is about 1.
It is about 0 to 2.0 mm.

This comatic aberration can be corrected by attaching a magnetic piece called a field controller (hereinafter abbreviated as F/C) to the screen-side tip of the electron gun of the picture tube inside the film.

However, in recent display tubes, horizontal deflection frequencies are often used at high frequencies of 64 KHz or higher, and in this case, since the F/C is a magnetic material, asymmetrical convergence errors occur due to AC loss. .

For this reason, color picture tubes used at a horizontal deflection frequency of about 64 KHz generally have a system in which the F/C is removed and coma aberration is corrected using the magnetic field of the deflection yoke itself. Of the coma aberrations, HCR is about 0.5 mm as described above, and can be corrected by a horizontal deflection coil.

However, since the amount of correction required for a VCR is large, a subcoil is connected in series with the vertical deflection coil to correct the VCR.

FIG. 8 shows a conventional example of a semi-toroidal deflection yoke equipped with subcoils.

This semi-toroidal deflection yoke includes a saddle-type horizontal deflection coil inside a mold 19, a toroidal-type vertical deflection coil 21 wound around an outer core 20, and a horizontal axis above and below (in the X direction) the rear end portion 22 of the deflection yoke. U-shaped subcoils 23a, 23b arranged symmetrically with respect to (x), left and right (
It is composed of rod-shaped subcoils 24a and 24b arranged symmetrically with respect to the vertical axis (y) in the X direction).

As shown in FIG. 9, the U-shaped subcoil 23a
, 23b and the rod-shaped subcoil 24a124b generate a binkction magnetic field and a barrel magnetic field, respectively, and both act in a direction to reduce vertical axis coma aberration (VCR).

(Problems to be Solved by the Invention) However, the subcoil having the above configuration has a drawback that when the VCR is optimally corrected at the upper and lower ends of the screen, it is overcorrected at the middle of the screen.

That is, FIG. 10 shows a typical convergence pattern when the VCR is corrected by the subcoil. In the figure, the VCR is corrected to zero at the y-axis end, but since the magnetic field strength of the subcoil tends to be saturated in the X direction, overcorrection occurs in the middle part in the X direction.

At the diagonal edge of the screen, there is a phenomenon called green dow loop (G-D) where the center beam droops at the periphery relative to the side beams, so the VCR at the y-axis edge is usually 0.1
~0.2mm, but at this time, the intermediate VCR is set to 0.
．． It will be about 2 to 0.4 mm. This phenomenon is a very serious problem, especially in display tubes with high snoring of 1 g and 1 degree, which require a maximum misconvergence of about 0.3 to 0.4 mm.

On the other hand, recent color display devices tend to have an extremely short retrace time for vertical scanning, and the frequency during this period corresponds to 10 KHz or more.

In a deflection yoke with a sub-coil, if a normal vertical deflection current of about 50 to 100 Hz flows in this sub-coil section, there will be no particular problem, but if the vertical deflection frequency exceeds 10 KHz, such as during the blanking period, When a high-frequency current flows, problems such as a delay in the phase of the correction current occur due to the influence of the coils and resistances included in the subcoil section. This is also problematic because it locally degrades on-screen convergence.

It is an object of the present invention to provide a deflection yoke for an in-line color picture tube that solves the above-mentioned conventional problems and has excellent convergence characteristics.

[Structure of the Invention] (Means for Solving the Problems) This invention provides the following steps to correct coma aberration (VCR):
At least two sets of subcoils are connected in series to the vertical deflection coil, and at least one of the subcoils has a reverse polarity to form a first current control system together with a pair of diodes connected in parallel. A second current control system consisting of a series circuit of a resistor and a choke coil is connected in parallel to the current control system.

(Function) According to the present invention, the correction of coma aberration is switched at a certain point in the vertical axis direction of the screen, eliminating insufficient correction at the end of the vertical axis, and also eliminating the problem caused by the phase delay of the correction current occurring in the subcoil section. This also solves the problem of local convergence that occurs.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

The deflection yoke of the present invention is constructed as shown in FIGS. 1 and 2, and the vertical deflection coil (not shown) has at least two sets of upper and lower coils for correcting comatic aberration related to vertical deflection in the direction of reducing both. U-shaped subcoil 1aslb
are connected in series. Left and right rod-shaped subcoils 2a s 2b are connected in series to this U-shaped subcoil 1b.

Further, a pair of diodes 3 connected in parallel with opposite polarity are connected in series to the rod-shaped subcoil 2b, and the left and right rod-shaped subcoils 2a.

2b and this diode pair 3 constitute a first current control system 4. In parallel to this first current control system 4,
A second current control system 7 consisting of a series circuit of a resistor 5 and a choke coil 6 is connected.

During operation, the subcoils la and lb of the upper and lower U-shaped cores
generates a binction magnetic field in the same direction as the vertical deflection coil magnetic field, and subcoils 2 a 12 of the left and right rod-shaped cores
b generates a barrel magnetic field in the opposite direction to the vertical deflection coil coil magnetic field, but in both the upper and lower, left and right subcoils, the magnetic field acts more strongly on the center beam than on the side beams, correcting the VCR.

Regarding the diode pair 3, diodes generally have a V-1 characteristic in which the current rapidly rises from a certain applied voltage value with respect to the applied voltage in the forward direction.

Therefore, the vertical deflection current flowing through the left and right subcoils 2as2b increases more rapidly at the rising edge of the diode pair 3 than at the target portion, and the VCR correction by the left and right subcoils 2a and 2b is added to the correction by the upper and lower subcoils la and lb. This solves the problem of insufficient VCR correction.

VCR correction up to the middle part in the vertical direction of the screen using only the upper and lower subcoils la and 1b, and the left and right subcoils 2a and 2b
If you combine it with the VCR correction to the outermost part, which also includes
It is possible to optimally correct the VCR at the outermost part of the vertical axis without over-correcting the VCR in the middle.

What is important here is the second current control system 7.

That is, this 27th! The S current control system 7 is composed of a resistor 5 and a choke coil 6, and the resistor 5 is connected to a diode pair so that the diode pair 3 in the second current control system 7 rises from a certain point in the vertical direction of the screen. This is for determining the applied voltage of No. 3, that is, the voltage across the first current control system 4 and the second current control system 7.

On the other hand, as mentioned above, recent color display devices tend to have extremely short retrace time for vertical scanning, and the deflection frequency during this period is 10 KHz or more. As for this vertical deflection current, when a fairly high-frequency deflection current during the retrace period flows through the deflection yoke circuit, the current that should flow through the coil at each point in the section where the resistor and coil in the deflection yoke circuit are in parallel is It changes due to the phase delay caused by the inductance of the coil.

This is because the vertical deflection current waveform is a sawtooth wave, so the deflection frequency during the blanking period is substantially higher than the scanning period on the screen, and the difference in frequency components is The increase in the impedance component of the coil upsets the balance between the resistance of the parallel circuit and the deflection current to the coil.

This problem has a current control system using a diode pair,
This problem is particularly serious in a deflection yoke such as the one of the present invention, which uses the rise of a diode to control the amount of correction.

This is because, in a single coil circuit for VCR correction as shown in FIG. Since it is used to vary the correction value, the ratio of current on the coil side to the resistance side is about 9:1, and most of the current flows to the coil side, so the circuit on the resistance side is This is because countermeasures can be taken by eliminating the resistance or increasing the resistance value.

On the other hand, in the deflection yoke circuit of the present invention, when a phase lag occurs between the first current control system 4 and the second current control system 7, it is difficult to take countermeasures because the resistor 5 is a diode pair. Since the purpose is to determine the timing of the start of the rise of 3, it is impossible to change the resistance value. Furthermore, since the first current control system 4 and the second current control system 7 are originally intended for shunting, the first current control system 4 has a deflection current of 20 to 30%.
Since only about % flows, it is not possible to eliminate the section on the resistance side as in a general correction circuit.

Therefore, in the present invention, the choke coil 6 is connected within the section of the second current control system 7 as described above.

Local misconvergence that occurs on the screen when there is no choke coil 6, and the deflection current waveform 1 at this time.
1 and the current waveform 12 of the first current control system 4, respectively.
Shown in Figures (a) and (b).

This is because the impedance of the sub-coils 2a and 2b of the first current control system 4 increases due to the high-frequency deflection current during the retrace period, and the correction waveform is no longer an ideal sawtooth wave, and the correction amount is reduced at the start of scanning. It is in a state of shortage. For this reason,
Center beam misconvergence occurs at the top edge of the screen.

In order to take measures against this phenomenon, it is necessary to improve the current balance between the first current control system 4 and the second current control system 7 during the period when the return high-frequency deflection current is flowing.

That is, the choke coil 6 acts only during the period when the return high-frequency deflection current is flowing. In other words, the impedance of the second current control system 7 is increased during the period when the high-frequency deflection current is flowing, and the current balance with the first current control system 4 is maintained as in the normal scanning period. The current waveform has been improved.

Now, to describe specific numerical values in the embodiment of this invention, the vertical deflection frequency of the color display device is 100H.
z, and 20 KHz during the retrace period. The impedance and resistance value of each element of the vertical deflection coil is 17.0 mH for the vertical deflection coil and 2 mH for the vertical subcoils la and lb.
2.0 mH for each, 0.6 mH for two left and right subcoils 2a% 2b, 2.7Ω for the resistor 5 of the second current control system 7, and 0.6 mH for the choke coil 6.

Among these, considering the impedance of the first fjs flow control system 4 and the second current control system 7, in a normal deflection section, the left and right subcoils 2a s 2b are 2π×100X
Since it is 0.6 x 10 -3 mL, the resistance is 0.4 Ω, and the resistance of the second current control system 7 is 2.7 Ω + 0.4 Ω, which is 3.1 Ω. If the resistance of diode pair 3 is ignored, first current control system 4:
The resistance ratio of the second current control system 7 is 0.4Ω:3.1Ω, and the current ratio is 7.8:1.

Next, in the retrace section, the left and right subcoils 2 a
% 2 b is 2πX20X103X0.5x10'm
Since it is L, it is 75.4Ω, and the second current control system 7 has a resistance of 2.7Ω.
Ω+75.4Ω = 78.1Ω. As in the normal deflection section, if the resistance of the diode pair 3 is ignored, the resistance ratio of the first current control system 4:second current control system 7 is 75.4Ω near 8
．． At 1Ω, the current ratio is 1.04:1.

If the second current control system 7 does not have the choke coil 6, the impedance of the second current control system 7 is independent of the frequency (2.7Ω).In this case, the first current control in the normal deflection section System 4: The resistance ratio of the second current control system 7 is 064Ω
:2.7Ω and the current ratio is 6.8:1. In the retrace section, only the impedance of the left and right subcoils 2a and 2b increases significantly, and the first current control system 4:second current control system 7
The resistance ratio is 75.4Ω:2.7Ω and the current ratio is 0.04:
It is 1.

In this way, when the second current control system 7 does not include the choke coil 6, almost no current flows in the first current control system 4 during the flyback period (0.04:1).

On the other hand, in this example, 50% of the current flows through the first current control system 4 (1.04:1), which is a significant improvement, so there is no local misconvergence even at the top of the screen. I was not able to admit. Although the current reduction was not completely zero, no misconvergence was observed because the actual display period began after a short back porch period.

Conversely, the reduction in current can be achieved by improving the misconvergence to the extent that it can be absorbed during the back porch period. However, in a color display device with a high retrace frequency, the purpose is to use the display area effectively, so the back porch period is also very short, and it is necessary to improve it to at least the level of the embodiment of this invention. .

It should be noted that the current ratios in the embodiments shown above are simply expressed, ignoring the resistance of the diode pair 3, and are somewhat different from the actual values.

Also, in this embodiment, in order to further improve it, it is only necessary to increase the inductance of the choke coil 6 of the second current control system 7, which is easy.

(Modification) FIG. 3 shows a modification of the present invention, which provides the same effects as the above embodiment.

That is, in this modification, the upper and lower U-shaped cores 13a, 13
Two sets of sub-coils are wound in the same direction in each of b, and one set of the coils is connected in series with a pair of diodes 14 bonded in parallel with reverse polarity, and together form a first current control system. A second current control system consisting of a resistor 15 and a choke coil 16 is provided in parallel with this first current control system.

Furthermore, the same method can be applied to sub-coils with an E-shaped core arranged on the left and right sides to generate a six-pole magnetic field.In addition, in this invention, the vertical deflection coil was of a toroidal type, but it can be of a saddle type. It doesn't matter.

[Effects of the Invention] According to the present invention, it is possible to eliminate the under-correction of the VCR at the vertical end without over-correcting the VCR near the middle part of the vertical axis.
Furthermore, it is possible to eliminate the problem of misconvergence of the center beam at the upper edge of the screen, which is caused by high-frequency deflection current during the vertical retrace period.

[Brief explanation of the drawing]

FIG. 1 is a wiring diagram showing the vicinity of the vertical deflection coil in a deflection yoke for an in-line color picture tube according to an embodiment of the present invention, FIG. 2 is a circuit configuration diagram showing the main part of FIG. 1, and FIG. A wiring diagram showing the vicinity of the vertical deflection coil in a deflection yoke for an in-line color picture tube according to a modification of the invention, FIG. 4 is a circuit configuration diagram of a general subcoil system, and FIGS. 5(a) and (b) are local diagrams. Figure 6 is a front view showing the main magnetic field of the deflection yoke for an in-line color picture tube. Figure 7 is a front view showing coma aberration on the screen. The figure is a perspective view showing the basic structure of a semi-toroidal deflection yoke equipped with subcoils, Figure 9 is a wiring diagram showing the magnetic field due to the subcoils, and Figure 10 is a front view showing the convergence error remaining when typical coma aberration is corrected. It is a diagram. la, lb... U-shaped vertical subcoil, 2a12b.
... Rod-shaped subcoil, 3... Diode pair, 4...
1st current control system, 5...Resistor, 6...Choke coil, 7...2nd current control system. Applicant's agent Patent attorney Takehiko Suzue The purity of Figure 3 drawing! F (no change in content) Figure 4 (a) (b) 8i ¥5
Figure 6 Figure i Figure 7 Figure 8 ■ Figure 9 Figure 1 O Procedural correction written type) % formula % 1. Indication of the incident Japanese Patent Application No. 63-33427 2. Name of the invention Deflection for in-line color picture tubes York 3, relationship with the amended person case Patent applicant (307) Toshiba Corporation 4, agent UBE Building 7, 3-7-2 Kasumigaseki, Chiyoda-ku, Tokyo;
Contents of the amendment (1) In Figure 5 of the drawing, the drawing number r(
a) Join J and r(b) J. (There is no change in the content of Figure 4)

Claims (1)

[Claims] (1) In a deflection yoke for an in-line color picture tube, which is equipped with a pair of horizontal deflection coils that perform deflection in the direction in which the in-line electron guns are arranged, and a pair of vertical deflection coils that perform deflection in a direction perpendicular to the direction in which the in-line electron guns are arranged, At least two sets of subcoils are connected in series to the vertical deflection coil for correcting coma aberration related to vertical deflection in a direction that reduces both the subcoils, and at least one set of the subcoils among the two sets has reverse polarity. A first current control system is formed with a pair of diodes connected in parallel, and a second current control system consisting of a series circuit of a resistor and a choke coil is connected in parallel to the first current control system. Deflection yoke for in-line color picture tubes.