JPH0758976A - Dynamic focus circuit - Google Patents

Abstract

PURPOSE:To highly precisely correct a dynamic focus with a simple circuit. CONSTITUTION:In a dynamic focus circuit provided with a dynamic focus transformer 20 supplying the pulse of a horizontal period to a primary-side so as to obtain a signal boosted to a secondary side and a capacitor 3 which is connected to the secondary side of a dynamic focus transformer 30 and converts the signal into the parabolic wave of the horizontal period, an orthogonal saturable reactance transformer 20 is connected to the primary-side of the dynamic focus transformer 30 in series, a control signal based on the parabolic wave of a vertical period is supplied to the control coil of the orthogonal saturable reactance transformer 20, and the parabolic wave of the horizontal period is modulated by the peak value of the parabolic wave of the vertical period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic focus signal generation circuit necessary for improving the focus characteristics of a cathode ray tube used for a monitor receiver or the like on the entire screen.

[0002]

2. Description of the Related Art In a cathode ray tube used for a monitor receiver or the like, the arrival distance of the electron beam is different between the central portion and the peripheral portion of the screen, so that even if the center of the screen is adjusted to the best focus, As it is, the focus becomes weak in the peripheral area. Therefore, the dynamic focus circuit boosts the flyback pulse of the horizontal period to several hundreds of V, and then integrates the boosted signal to generate a parabolic wave signal of the horizontal scanning period (parabolic wave of a quadratic curve). This parabolic wave signal is applied to the focus control electrode of the cathode ray tube as a dynamic focus signal. By doing so, the dynamic focus correction is performed so that the focus is best over the entire screen.

[0003]

However, if the dynamic focus correction is performed only by the parabolic wave signal that is simply integrated in the horizontal period as in the conventional case,
It was difficult to perform complete dynamic focus correction. That is, with a parabolic wave signal such as a quadratic curve obtained by integrating the horizontal synchronization signal, although focus correction can be performed to some extent, complete focus correction is not performed.
The focus characteristics were slightly deteriorated in the peripheral part of the screen (especially each corner part). Here, in the case of a normal television receiver for watching television broadcasts, the deterioration of the focus characteristic of the peripheral portion to this extent is usually within an allowable range, but as in the case of a computer display, it is fine. In the case of a monitor receiver that needs to display characters and the like, it is necessary to perform more accurate dynamic focus correction even in the peripheral portion of the screen.

In order to solve this problem, the vertical focus parabolic wave is superimposed on the horizontal focus parabolic wave dynamic focus signal so that the overall level of the dynamic focus signal corresponds to the peripheral portion of the screen. Although there are some corrections that increase the height at the points where it does, this level of correction was not sufficient.

In view of the above points, an object of the present invention is to make it possible to easily perform highly accurate dynamic focus correction on the entire screen.

[0006]

As shown in FIG. 1, the present invention provides a dynamic focus transformer 20 for supplying a pulse of a horizontal period to a primary side to obtain a boosted signal on a secondary side, and a dynamic focus transformer 20. Focus transformer 30
In a dynamic focus circuit having a capacitor 3 that is connected to the secondary side of the dynamic focus transformer 30 and converts into a parabolic wave of a horizontal period, a quadrature saturable actance transformer 20 is connected in series with the primary side of the dynamic focus transformer 30. A control signal based on a parabolic wave having a vertical cycle is supplied to the control winding of the saturation actance transformer 20 so that the parabolic wave having a horizontal cycle is modulated with the peak value of the parabolic wave having a vertical cycle.

Further, in this case, a parabolic wave having a vertical period is superimposed on the secondary side of the dynamic focus transformer 30.

[0008]

According to the present invention, the parabolic wave having a horizontal period is modulated by the parabolic wave having a vertical period by the quadrature saturable actance transformer, and the peak-to-peak value of the dynamic focus signal at the beginning and the end of one vertical period. Is increased, and the focus characteristic of the peripheral portion of the screen is improved.

Further, in this case, by superimposing the parabolic wave of the vertical period on the secondary side of the dynamic focus transformer, the focus characteristic of the peripheral portion of the screen becomes better.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the dynamic focus circuit of the present invention will be described below with reference to FIGS. The circuit of this example is applied to a dynamic focus circuit of a monitor receiver that needs to display an image with high resolution.

FIG. 1 is a diagram showing the structure of the dynamic focus circuit of this embodiment. In the figure, reference numeral 10 denotes a horizontal drive transformer. In the horizontal drive transformer 10, a horizontal synchronizing signal of a video signal to be received by a cathode ray tube is primary winding. The flyback pulse having a horizontal period is supplied from the secondary winding 12 to the line 11. Then, this flyback pulse is supplied to the primary winding 21 of the vertical modulation transformer 20. The vertical modulation transformer 20 is composed of a quadrature coupling type saturable reactor transformer, and the inductance of the primary winding 21 side is changed by the current of the signal supplied to the control winding 22. The signal supplied to the control winding 22 will be described later.

The primary winding 31 of the dynamic focus transformer 30 is connected in series with the primary winding 21 of the vertical modulation transformer 20. The dynamic focus transformer 30 is a transformer that boosts voltage to obtain a voltage required as a dynamic focus signal. One end of a secondary winding 32 of the dynamic focus transformer 30 is grounded via a capacitor 1 and a vertical cycle parabola is used. Connect to wave input terminal 2. Then, the secondary winding 32
The other end of is connected to one end of the integrating capacitor 3 and the dynamic focus signal output terminal 4. Then, the signal obtained at the dynamic focus signal output terminal 4 is supplied to the focus control electrode (or focus coil) of the cathode ray tube.

Since the secondary winding 32 of the dynamic focus transformer 30 to the output terminal 4 are configured as described above, the boosting signal of the horizontal period obtained at the secondary winding 32 is integrated by the capacitor 3. As a result, a horizontal period parabolic wave is obtained as a dynamic focus signal at the output terminal 4. In this case, since the parabolic wave of the vertical period is supplied from the vertical period parabolic wave input terminal 2 to one end side of the secondary winding 32, the parabolic wave of the vertical period is superimposed on the dynamic focus signal.

In this example, the signal obtained at the other end of the secondary winding 32 of the dynamic focus transformer 30 is supplied to the peak detection circuit 5. The peak detection circuit 5 detects the peak value of the dynamic focus signal supplied to the output terminal 4 side, and supplies the detected peak value data to the comparator 6. Further, the parabolic wave signal of the vertical period obtained at the vertical period parabolic wave input terminal 7 is supplied to the comparator 6. Then, when the level of the parabolic wave signal of the vertical cycle exceeds the peak level of the dynamic focus signal in the comparator 6,
Output the corresponding control signal. Then, this control signal is supplied to the control winding 22 of the vertical modulation transformer 20.

Next, the operation of the dynamic focus circuit configured as described above will be described. First, the signal state in each horizontal period will be described. From the secondary winding 12 of the horizontal drive transformer 10, a flyback pulse of the voltage shown in A of FIG. 2 is output every horizontal scanning period (1H). . At this time, the current of the flyback pulse becomes a sawtooth wave as shown in B of FIG. Therefore, a similar sawtooth wave current can be obtained on the side of the secondary winding 32 of the dynamic focus transformer 30. Then, by supplying the sawtooth wave to the capacitor 3, the voltage of the dynamic focus signal obtained at the output terminal 4 becomes a parabolic wave having a horizontal period shown in C of FIG.

In the present embodiment, the control signal supplied to the control winding 22 of the vertical modulation transformer 20 is created with the above-mentioned configuration, so that the peak value changes in the vertical cycle. That is, as shown in A of FIG.
A parabolic wave whose potential changes in the vertical cycle (1 V) is supplied to the input terminal 7, and a control signal based on this parabolic wave is supplied to the control winding 22. At this time, the modulation according to the level of the parabolic wave is performed by the vertical modulation transformer 20, and the dynamic focus signal obtained at the output terminal 4 has a peak value (peak value here) as shown in B of FIG. Is the peak-to-peak value). Specifically, as shown in FIG. 3B, the peak value P ₁ at substantially the center of each vertical period becomes the lowest level, and the peak values P _{2 at the start} and end of each vertical period become Be at the highest level.

The lowest level V _{L of the} waveform shown in FIG. 3B rises in a parabolic shape because the parabolic wave of the vertical period obtained at the input terminal 2 is superimposed on the dynamic focus signal. Is.

By supplying the dynamic focus signal having such a waveform to the focus control terminal of the cathode ray tube, excellent dynamic focus correction is performed.
That is, at the beginning and end of each vertical period, the peak level of the dynamic focus signal (peak value P of B in FIG. 3).
_{Since the} modulation is performed such that ₂ ) becomes high, the focus characteristic becomes good in the peripheral portion of the screen (particularly in the vicinity of each corner of the screen) corresponding to the start and end of each vertical period. In this case, the circuit configuration is a vertical modulation transformer 2 composed of a quadrature saturable actance transformer.
It is only necessary to supply a control signal based on a parabolic wave having a vertical period to 0, so that it can be realized with a simple configuration.

Further, in this example, since the parabolic wave of the vertical period obtained at the input terminal 2 is superimposed on the dynamic focus signal and the minimum level is raised in a parabolic shape, the focus characteristic of the peripheral portion becomes better. Become.

[0020]

According to the present invention, the parabolic wave of the horizontal period is modulated by the parabolic wave of the vertical period by the orthogonal saturable actance transformer, and the peak-to-peak of the dynamic focus signal at the beginning and the end of one vertical period is The peak value becomes large, the focus characteristic of the peripheral portion of the screen becomes good, and good dynamic focus correction can be performed on the entire screen with a simple configuration.

Further, in this case, by superimposing the parabolic wave of the vertical period on the secondary side of the dynamic focus transformer, the focus characteristic in the peripheral portion of the screen becomes better.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram showing a signal waveform of a horizontal cycle according to an embodiment.

FIG. 3 is a waveform diagram showing a signal waveform of a vertical cycle according to an embodiment.

[Explanation of symbols]

 2 Vertical cycle parabolic wave input terminal 3 Capacitor 4 Dynamic focus signal output terminal 5 Peak detection circuit 6 Comparator 7 Vertical cycle parabolic wave input terminal 10 Horizontal drive transformer 20 Vertical modulation transformer 30 Dynamic focus transformer

Claims (2)

[Claims] 1. A dynamic focus transformer for supplying a pulse of a horizontal cycle to a primary side to obtain a boosted signal on a secondary side, and a parabolic wave of a horizontal cycle connected to the secondary side of the dynamic focus transformer. In a dynamic focus circuit having a capacitor, a quadrature saturable actance transformer is connected in series with the primary side of the dynamic focus transformer, and a control winding of the quadrature saturable actance transformer is connected to a control coil based on a vertical period parabolic wave. A dynamic focus circuit configured to modulate the horizontal period parabolic wave with the peak value of the vertical period parabolic wave by supplying a control signal. 2. The dynamic focus circuit according to claim 1, wherein a parabola wave having a vertical period is superimposed on the secondary side of the dynamic focus transformer.