JP2643573B2 - Dynamic focus correction circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic focus correction circuit for correcting a dynamic focus CRT of a color television receiver.

2. Description of the Related Art In recent years, color television receivers have been progressing in the direction of large screen and high image quality. It is essential to improve the focus performance of CRT.

In general, an inline self-convergence CRT has the advantage that beam spots of three colors, red, green and blue, can be automatically converged over the entire screen by a deflecting magnetic field. There is a disadvantage that the beam spot is easily distorted. Further, in the case of a large-sized CRT, the degree of distortion due to the deflecting magnetic field is further increased because the angle is set to 110 ° wide-angle deflection in order to shorten the depth of the color television receiver. An effective means of reducing this deflection aberration is to improve the CRT electron gun that dynamically corrects the focus. This has two independent focus electrodes on the CRT, one to which a DC voltage is applied, and the other to which a parabolic voltage waveform of about 1 KVp-p is superimposed on the DC voltage, that is, a dynamic correction voltage waveform is applied. This technology dynamically improves the focus of the entire screen.

The dynamic correction voltage waveform applied to the focus electrode requires two types of dynamic correction voltages, a horizontal scanning period and a vertical scanning period. In the present invention, however, the dynamic correction voltage waveform relates to the horizontal scanning period. Omit.

Hereinafter, an example of the above-described conventional dynamic focus correction circuit will be described with reference to the drawings.

3 and 4 show the configuration of a conventional dynamic focus correction circuit and the generated dynamic focus correction voltage waveform. In FIG. 3, 1 is a dynamic focus CRT, 2 is a focus electrode, 10 is a high voltage generation circuit, 11 is a flyback transformer (hereinafter abbreviated as FBT), 12 is a focus volume, 13 is a focus volume, 14 is a condenser, and 20 is a condenser. A horizontal deflection circuit, 21 is a pulse transformer, 22 is an LC integration circuit, and 23 is a deflection yoke.

The operation of the conventional dynamic focus correction circuit will be described below. Dynamic focus
The CRT 1 has two focus electrodes 2. High voltage generation circuit
High voltage 15 generated at 10 and focus volumes 12 and 13
More focus voltage for each dynamic focus
Apply to CRT1. The deflection yoke 23 of the deflection circuit 20 performs horizontal deflection of the dynamic focus CRT1. Pulse transformer
Negative flyback pulse generated in the secondary winding of 21 LC
The parabolic voltage waveform is obtained by integration by the integration circuit 22. This parabolic voltage waveform is added as a dynamic focus correction voltage waveform to the center point of the focus volume 13 via the capacitor 14 so as to be superimposed on the DC voltage.
FIG. 4 shows a midpoint dynamic focus correction voltage waveform of the focus volume 13. (For example, NATIONAL T
ECHNICAL REPORT VOL.34 No.5 OCT.1988 4〜14,31〜37
page).

Problems to be Solved by the Invention However, in recent years, high-definition television (hi-vision)
With the development of the broadcasting system, the aspect ratio of the conventional 4 to 3
A 16: 9 CRT, which is wider than that of the CRT, has been developed. Since the HDTV broadcast system has several times the amount of information as compared to the conventional current broadcast system, it is necessary to further improve the focus of the CRT, and the CRT electron gun is also large in diameter. Along with this, when the dynamic focus correction voltage waveform required by the dynamic focus CRT is a conventional parabolic waveform, both sides of the CRT are insufficiently corrected and cannot be corrected. Further, the peak value is required to be several KVp-p higher than about 1 KVp-p.

Dynamic focus CR with landscape aspect ratio of 16: 9
FIG. 4 shows a dynamic focus correction voltage waveform required by T and a dynamic focus correction voltage waveform generated by the above-described conventional dynamic focus correction circuit. In FIG. 4, C indicates the required correction voltage waveform, and A and B are conventional correction voltage waveforms, each of which is adjusted to the peak values at points B and C based on point A of the required correction voltage waveform. It is a thing. As is clear from the figure, a difference between V ₁ and V ₂ occurs at point B and point C. That is, there is a problem that focus cannot be performed on the left and right portions of the CRT.

In view of the above problems, the present invention has a landscape aspect ratio of 16: 9.
A dynamic focus correction circuit capable of stably generating a dynamic focus correction voltage waveform required by the dynamic focus CRT.

Means for Solving the Problems In order to solve the above problems, a dynamic focus correction circuit of the present invention comprises a flyback type horizontal deflection circuit for horizontally deflecting a CRT, and a flyback pulse generated by the horizontal deflection circuit as an input. A first transformer to perform
An integrating circuit for integrating a first flyback pulse generated in the secondary winding of the transformer and a pulse generating circuit for generating a flyback pulse wider than the first flyback pulse are provided by this pulse generating circuit. A second transformer that receives the generated flyback pulse as an input, and modulates an output integrated by the integration circuit with a second flyback pulse generated in a secondary winding of the second transformer. And applying the output to the CRT focus electrode via a capacitor.

Function The present invention has the above-described configuration, and has a landscape aspect ratio of 16
A dynamic focus correction voltage waveform required for a dynamic focus CRT having a nine-screen is obtained. The necessary waveform is a waveform in which a change near both sides of a parabolic waveform (y = x ² ) obtained by a conventional integration circuit is sharp. Further, even waveforms obtained at y = x ₃ and y = x ₄ cannot be approximated. The present invention sharpens the change near both sides of the parabolic waveform obtained by the conventional integration circuit,
The parabolic waveform is modulated by a flyback pulse having a wide pulse width newly generated by the flyback method. As a result, an approximate waveform of the required dynamic focus correction voltage waveform can be obtained.

Embodiment Hereinafter, a dynamic focus correction circuit according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a dynamic focus correction circuit according to an embodiment of the present invention. In FIG. 1, 30
Is a pulse generation circuit, 31 is a switching transistor, 32
Is a damper diode, 33 is a resonance capacitor, 34 is a pulse transformer, 25 is a switching transistor, 26 is a damper diode, and 27 is a resonance capacitor. One end of a secondary winding 35 of the pulse transistor 34 is grounded, and the other end is connected to the secondary winding 24 of the pulse transformer 21 and the LC integration circuit 22. Drive signals having the same frequency and the same phase are applied to the bases of the transistors 25 and 31. Note that the components having the same numbers as those in FIG. 3 have the same functions as those described in the conventional example, and the description is omitted.

The operation will be described below with reference to FIGS. First Figure 2, there is shown an operation voltage waveform diagram, two pulse width t ₁ in flyback pulse voltage waveform generated in the secondary winding 24 of the pulse transformer 21 and the capacitance of the resonance capacitor 27 deflection yoke It is determined by the L value of 23. E is a parabolic voltage waveform generated at both ends of the capacitor of the LC integration circuit 22,
F is a flyback pulse generated in the secondary winding 35 of the pulse transformer 34 which receives the flyback pulse generated by the pulse generation circuit 30 as an input. The pulse width t ₂ is the resonance capacitor 33 and the primary winding of the pulse transformer 34. determined by the L value of the line, it will now be set wider than the pulse width t ₁ described above. The dynamic focus correction superimposed on the center point of the focus volume 13 obtained by modulating the parabolic voltage waveform of the LC integration circuit 22 by the flyback pulse (to FIG. 2) generated in the secondary winding 35 of the pulse transformer 34 It is a voltage waveform.

As described above, in the present configuration, the pulse generating circuit 30 for generating a wider flyback pulse of the flyback pulse generated by the horizontal deflection circuit 20 is provided, and the transformer 21 having the generated flyback pulse as an input is provided. Next winding
By modulating the output of the LC integrator circuit 22 with the flyback pulse generated at 24, the horizontal aspect ratio 16
A dynamic focus correction voltage waveform required by the dynamic focus CRT of 9 can be obtained.

As described above, the present invention provides a flyback-type horizontal deflection circuit that horizontally deflects a CRT, a first transformer that receives a flyback pulse generated by the horizontal deflection circuit as an input,
An integration circuit for integrating a first flyback pulse generated in a secondary winding of the first transformer, a pulse generation circuit for generating a flyback pulse having a pulse width wider than that of the first flyback transformer, The output of the integration circuit is modulated by the second flyback pulse generated in the secondary winding of the transformer which receives the flyback pulse generated by the pulse generation circuit as an input. Thus, a dynamic focus correction voltage waveform required for the dynamic focus CRT can be obtained. Further, by using the flyback method, a corrected waveform having a pulse width and a high peak value can be stably obtained.

[Brief description of the drawings]

1 is a circuit diagram of a dynamic focus correction circuit according to one embodiment of the present invention, FIG. 2 is an operating voltage waveform diagram for explaining the operation of FIG. 1, and FIG. 3 is a dynamic focus correction circuit according to a conventional embodiment. FIG. 4 is a circuit diagram of FIG.
It is a waveform diagram of the dynamic focus voltage of the figure. 1 ... Dynamic focus CRT, 20 ... Horizontal deflection circuit, 21 ... Pulse transformer, 22 ... LC integration circuit, 30 ...
Pulse generation circuit, 34 ... Pulse transformer.

Claims (1)

(57) [Claims] 1. A flyback type horizontal deflection circuit for horizontally deflecting a CRT, a first transformer to which a flyback pulse generated by the horizontal deflection circuit is input, and a secondary winding of the first transformer. An integration circuit that integrates the generated first flyback pulse, a pulse generation circuit that generates a flyback pulse having a pulse width wider than the first flyback pulse, and a flyback pulse generated by the pulse generation circuit. A second transformer that modulates the output integrated by the integration circuit with a second flyback pulse generated in the secondary winding of the second transformer, and modulates the modulated output via a capacitor. A dynamic focus correction circuit characterized in that a voltage is applied to a CRT focus electrode.