JP2708167B2 - Deflection yoke for in-line type color picture tube - Google Patents

Description

The present invention relates to a deflection yoke for an in-line type color picture tube suitable for use as a deflection yoke for a high resolution color display tube, for example.

(Prior Art) Generally, a color picture tube having an in-line type electron gun is characterized in that the magnetic field of the deflection yoke is made non-uniform, so that the color picture tube and the deflection yoke can be combined with each other without using external circuit correction means. It has a so-called self-convergence function of making the three electron beams substantially coincide with each other in all parts of the screen by the combination.

In such an in-line type color picture tube, as shown in FIG.
17. By using the barrel magnetic field 18 as the vertical deflection magnetic field, there is an advantage that convergence between both side beams (R, B) can be obtained without an external correction circuit.

However, since a non-uniform magnetic field is used as described above, there is a so-called coma aberration in which the deflection sensitivity with respect to the center beam (G) becomes worse than the deflection sensitivity with respect to both side beams. It appears as such a pattern.

That is, the coma of the horizontal axis (x) is HCR and the vertical axis (y) is
Assuming that the coma is VCR, the HCR is about 0.5 mm and the VCR is about 1.0 to 2.0 mm even in a normal 14-inch 90 ° tube.

This coma aberration is generally 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.

However, in recent display tubes, the horizontal deflection frequency is often used at a high frequency of 64 KHz or more. In this case, since the F / C is a magnetic material, an asymmetric convergence error occurs due to AC loss. .

For this reason, a color picture tube used with a horizontal deflection frequency of about 64 KHz generally uses a method in which F / C is removed and coma is corrected by the magnetic field of the deflection yoke itself.
As for the HCR of coma aberration,
It is about 0.5 mm and can be corrected by a horizontal deflection coil.

However, the amount of correction for the VCR is large, and the VCR is corrected by connecting a sub coil in series with the vertical deflection coil.

FIG. 8 shows a conventional example of a semi-toroidal deflection yoke having a sub coil.

The 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 deflection yoke rear end 22.
U-shaped subcoils 23a and 23b arranged symmetrically with respect to the horizontal axis (x) in the vertical direction (y direction), and rod-shaped subcoils arranged symmetrically with respect to the vertical axis (y) in the left and right direction (x direction) twenty four
a and 24b.

Then, as shown in FIG.
The a and 23b and the bar-shaped sub-coils 24a and 24b generate a pincushion magnetic field and a barrel magnetic field, respectively, and are both used in the direction of reducing the vertical axis coma (VCR).

(Problems to be Solved by the Invention) However, the sub-coil configured as described above has a disadvantage that when the VCR is optimally corrected at the upper and lower ends of the screen, the VCR is excessively corrected at the middle part of the screen.

That is, FIG. 10 shows a typical convergence pattern when the VCR is corrected by the sub coil. The figure shows the case where the VCR is corrected to zero at the y-axis end. However, since the magnetic field strength of the sub-coil tends to saturate in the y-direction, it is overcorrected in the middle part in the y-direction.

At the screen diagonal edge, there is a phenomenon called a green droop (GD) in which the center beam hangs around the side beam with respect to the side beam, so the VCR is usually 0.1 to 0.2 m at the y-axis end.
In this case, the middle part VCR is about 0.2 to 0.4 mm. This phenomenon is especially noticeable with a maximum misconvergence of 0.3
This is a very serious problem in a high-resolution display tube requiring about 0.4 mm.

On the other hand, recent color display devices tend to make the retrace time of vertical scanning extremely short, and the frequency during this period is equivalent to 10 KHz or more.

In a deflection yoke having a subcoil, when a normal vertical deflection current of about 50 to 100 Hz flows in this subcoil section, there is no particular problem, but as a vertical deflection frequency exceeding 10 KHz as in the retrace period, the When a high-frequency current flows, there arises a problem that the phase of the correction current is delayed due to the influence of the coil and the resistance included in the sub-coil section. This is also a problem because it locally deteriorates the convergence on the screen.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional problems and to provide a deflection yoke for an in-line type color picture tube having excellent convergence.

According to the present invention, at least two sets of sub-coils are connected in series to a vertical deflection coil to correct coma aberration (VCR), and at least one set of the sub-coils is connected. Sub-coils constitute a first current control system with a diode pair connected in parallel with the polarity reversed, and a second current control system comprising a series circuit of a resistor and a choke coil in parallel with the first current control system. Are connected.

(Function) According to the present invention, at a certain point in the screen vertical axis direction,
By switching the correction of the coma aberration, the insufficient correction of the vertical axis end is eliminated, and the problem of the local convergence caused by the phase delay of the correction current generated in the subcoil section is also eliminated.

Hereinafter, an embodiment 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. At least two pairs of upper and lower vertical deflection coils for correcting coma aberration relating to vertical deflection are provided in a vertical deflection coil (not shown). The U-shaped sub-coils 1a and 1b are connected in series. In this U-shaped sub coil 1b,
Left and right rod-shaped subcoils 2a, 2b are connected in series.

Further, a diode pair 3 connected in parallel with inverted electrode characteristics is connected in series with the rod-shaped sub-coil 2b, and the left and right rod-shaped sub-coils 2a and 2b and the diode pair 3 are connected.
These form the first current control system 4. This first
A resistor 5 and a choke coil 6 are connected in parallel with the current control system 4.
Is connected.

During operation, the upper and lower U-shaped core sub-coils 1a, 1b
Generates a pincushion magnetic field in the same direction as the vertical deflection coil magnetic field, and the sub-coils 2a and 2b of the operating rod-shaped core generate a barrel magnetic field in the opposite direction to the vertical deflection coil magnetic field. The magnetic field acts more strongly on the center beam than on the side beams, correcting the VCR.

The diode pair 3 generally has a VI characteristic in which a current rapidly rises from a certain applied voltage value with respect to a forward applied voltage.

Therefore, the vertical deflection current flowing through the left and right subcoils 2a and 2b increases more rapidly than the portion corresponding to the rising portion of the diode pair 3, and the VCR correction by the left and right subcoils 2a and 2b is added to the correction by the upper and lower subcoils 1a and 1b. Insufficient VCR correction is resolved.

By combining the VCR correction up to the middle part in the screen vertical direction using only the upper and lower sub-coils 1a and 1b and the VCR correction up to the outermost part including the left and right sub-coils 2a and 2b, the vertical axis External VCR correction can be optimally performed.

What is important here is the second current control system 7. That is,
The second current control system 7 includes a resistor 5 and a choke coil 6. The resistor 5 is arranged so that the diode pair 3 in the second current control system 7 rises from a certain point in the screen vertical direction. This is for determining the applied voltage of the diode pair 3, that is, the voltage across the first current control system 4 and the second current control system 7.

On the other hand, as described above, recent color display devices tend to make the retrace time of vertical scanning extremely short,
The deflection frequency during this period is 10 KHz or more. As the vertical deflection current, when the deflection current during the retrace period of a considerably high frequency flows through the deflection yoke circuit, the current to flow through the coil at each point of the section having the resistance and the coil in parallel in the deflection yoke circuit is It changes due to a phase delay caused by the inductance of the coil.

This is because the vertical deflection current waveform is a sawtooth wave, and the deflection frequency during the flyback period is substantially significantly higher than the scanning period on the screen. The increase in the impedance component of the coil has disturbed the resistance of the parallel circuit and the shunt balance of the deflection current to the coil.

This problem is particularly serious in a deflection yoke according to the present invention which has a current control system using a diode pair and controls the correction amount using the rise of the diode.

This is because, in a general VCR correction sub-coil circuit as shown in FIG. 4, the resistor 9 and the variable resistor 10 connected in parallel to the sub-coil 8 delicately control the maximum value of the correction value, Since it is used to change the correction value, the ratio of the current on the coil side and the resistance side is about 9: 1,
Since most of the current flows to the coil side, by eliminating the circuit on the resistance side or increasing the resistance value,
This is because measures can be taken.

On the other hand, in the deflection yoke circuit according to the present invention,
If a phase lag occurs between the first current control system 4 and the second current control system 7, the reason why the countermeasure is difficult is that the resistor 5 first determines the time when the diode pair 3 starts to rise. Therefore, the resistance value cannot be changed. Also, the first
The current control system 4 and the second current control system 7 are originally intended for shunting, and the first current control system 4 has 20 to 30% of the deflection current.
Since it flows only to the extent, it is not possible to eliminate the section on the resistance side unlike a general correction circuit.

Therefore, in the present invention, as described above, the second current control system 7
Is connected to the choke coil 6.

Without the choke coil 6, local misconvergence on the screen and the deflection current waveform at this time
FIGS. 5 (a) and 5 (b) show the current waveform 11 and the current waveform 12 of the first current control system 4, respectively.

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, the correction waveform does not become an ideal saw-tooth wave, and the correction amount is reduced at the start of scanning. It is in shortage. For this reason, misconvergence of the center beam occurs at the upper end of the screen.

In order to prevent this phenomenon, it is necessary to improve the balance between the currents of the first current control system 4 and the second current control system 7 during the period in which the high-frequency deflection current of the retrace is flowing.

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

Now, when describing specific numerical values in the embodiment of the present invention, the vertical deflection frequency of the color display device is 100H.
z, 20KHz during the retrace period. The impedance and resistance of each element of the vertical deflection coil are 17.0 mH for the vertical deflection coil, 2.0 mH for two vertical subcoils 1 a and 1 b, 0.6 mH for two left and right subcoils 2 a and 2 b, and the second current control system. 7, the resistance 5 is 2.7Ω, and the choke coil 6 is 0.6 mH.

Considering the impedance of the first current control system 4 and the second current control system 7, the left and right sub ^- coils 2a and 2b are 2π × 100 × 0.6 × 10 ⁻³ wL in the normal deflection section.
0.4Ω, and the second current control system 7 has a resistance of 2.7Ω + 0.4Ω and 3.1Ω. 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 0.4Ω: 3.1Ω and the current ratio is 7.8: 1.

Next, in the retrace interval, the left and right sub-coils 2a,
Since 2b is 2π × 20 × 10 ³ × 0.6 × 10 ^-3 wL, 75.4Ω, 2nd
The current control system 7 has a resistance of 2.7Ω + 75.4Ω and 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 75.4.
Ω: 78.1Ω and the current ratio is 1.04: 1.

If the choke coil 6 is not provided in the second current control system 7, the impedance of the second current control system 7 is 2.7Ω regardless of the frequency. In this case, the first of the normal deflection section
Current control system 4: Resistance ratio of second current control system 7 is 0.4Ω: 2.7Ω
And the current ratio is 6.8: 1. In the retrace interval, only the impedance of the left and right sub-coils 2a and 2b significantly increases, and the resistance ratio of the first current control system 4: the second current control system 7 is 75.4Ω: 2.7
In Ω, the current ratio is 0.04: 1.

When the choke coil 6 is not provided in the second current control system 7 as described above, the current of the first current control system 4 during the retrace period hardly flows (0.04: 1).

On the other hand, in this embodiment, 50% of the current flows through the first current control system 4 (1.04: 1), and since the current is greatly improved, local misconvergence is recognized even at the upper end of the screen. Did not. Misconvergence was not observed, even though the decrease in current was not completely zero, because the actual display interval started after a slight back porch period.

Conversely, the reduction of the current only needs to be improved to the extent that misconvergence can be absorbed in the back porch period. However, in a color display device having a high retrace frequency, the back porch period is very short because the purpose is to use the display area more effectively, and it is necessary to improve the back porch at least to the embodiment of the present invention.

Note that the current ratio in the above-described embodiment is simply expressed ignoring the resistance of the diode pair 3, and is slightly different from the actual value.

Also in this embodiment, further improvement can be achieved easily by increasing the inductance of the choke coil 6 of the second current control system 7.

(Modification) FIG. 3 shows a modification of the present invention, and the same effects as in the above embodiment can be obtained.

That is, in this modification, two pairs of sub-coils are wound around the upper and lower U-shaped cores 13a and 13b in the same direction, and one pair of the coils is connected in parallel with the polarity reversed. 14 are connected in series with each other to form a first current control system, and a resistor 15 is connected in parallel to the first current control system.
And a second current control system including a choke coil 16.

Further, the same method can be applied to E-shaped core sub-coils that generate a six-pole magnetic field disposed on the left and right.

Although the vertical deflection coil is of a toroidal type in the present invention, it may be of a saddle type.

[Effects of the Invention] According to the present invention, it is possible to eliminate insufficient VCR correction at the vertical end without overcorrecting the VCR near the middle part of the vertical axis, and furthermore, the screen caused by the high-frequency deflection current during the vertical flyback period At the upper end can eliminate the center beam misconvergence problem.

[Brief description of the drawings]

FIG. 1 is a connection diagram showing the vicinity of a vertical deflection coil in a deflection yoke for an in-line type color picture tube according to an embodiment of the present invention, FIG. 2 is a circuit configuration diagram showing a main part of FIG. 1, and FIG. FIG. 4 is a connection diagram showing the vicinity of a vertical deflection coil in a deflection yoke for an in-line type color picture tube according to a modification of the invention, FIG. 4 is a circuit configuration diagram of a general sub-coil system, and FIGS. FIG. 6 is a front view showing a main magnetic field of a deflection yoke for an in-line type color picture tube, FIG. 7 is a front view showing coma aberration on a screen, FIG. FIG. 9 is a perspective view showing the basic structure of a semi-toroidal deflection yoke provided with a subcoil, FIG. 9 is a connection diagram showing a magnetic field generated by the subcoil, and FIG. It is a front view showing a Suera. 1a, 1b: U-shaped vertical subcoil, 2a, 2b: rod-shaped subcoil, 3: diode pair, 4: first current control system,
5: resistance, 6: choke coil, 7: second current control system.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification number Agency reference number FI Technical indication location H04N 9/28 H04N 9/28 C

Claims (1)

(57) [Claims] 1. A deflection yoke for an in-line type color picture tube comprising a pair of horizontal deflection coils for deflecting in the arrangement direction of an in-line type electron gun and a pair of vertical deflection coils for deflecting in a direction perpendicular to the arrangement direction. And at least two subcoils connected in series to the vertical deflection coil for correcting coma aberration relating to vertical deflection together, wherein at least one of the two subcoils has a polarity. Conversely, a first current control system configured with a diode pair connected in parallel is provided, and a second current control system including a series circuit of a resistor and a choke coil is provided for the first current control system.
A deflection yoke for an in-line type color picture tube, wherein a current control system is connected in parallel.