JP2001320728A - Vertical deflection circuit and video display device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To position emission lines for references used for an auto cut-off circuit considerably outside an effective picture, and to vary the position of the emission lines for references in correspondence with to the number of effective scanning lines. SOLUTION: The vertical deflection circuit capable of inserting a reference pulse in a video signal, projecting the emission lines for references by the reference pulse, and then performing the adjustment of a black level automatically is provided with a means 11 for place the emission lines for references for positioning the emission lines for references outside the effective picture, and a means 7 for adjusting the position of the emission lines for references for adjusting the position outside the effective picture of the emission lines for references.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical deflection circuit having a function of automatically correcting a black level change of an image due to aging of a cathode ray tube, and for a reference for positioning a reference bright line outside an effective screen. A bright line arrangement means for adjusting the position of the reference bright line outside the effective screen; and a reference bright line position adjusting means for adjusting the position of the reference bright line outside the effective screen. The present invention relates to a vertical deflection circuit capable of changing the position of a reference bright line corresponding to the above and a video display device having the same.

[0002]

2. Description of the Related Art Conventionally, a cathode ray tube (hereinafter referred to as CRT).
As a method of correcting a change in black level of an image due to aging of a CRT, a reference pulse is added to a vertical blanking period of a video signal, and a reference bright line is projected by the added reference pulse. A so-called auto cut-off circuit is used, which detects the cathode current and processes it so as to be kept at a constant value, and keeps the black level of the displayed image constant.

FIG. 4 shows a general vertical deflection circuit. The deflection control IC (integrated circuit) 22 includes a vertical counter 23, a vertical oscillator 24, and a gain control circuit 26. The vertical counter 23 is supplied with a vertical synchronizing signal Vs and a horizontal synchronizing signal 2fH having a frequency twice the horizontal oscillation frequency. In the vertical counter 23, the horizontal synchronization signal 2fH is counted, and the counter is reset by the vertical synchronization signal Vs. This reset pulse is supplied to the vertical oscillator 24 to generate sawtooth waves VD ⁺ and VD ⁻ for vertical deflection as shown in FIG. When the vertical synchronizing signal Vs is not externally applied, the vertical oscillator 24 continues to oscillate at a preset cycle.

Controlling the peak value, the time variation (linearity) and the like in the gain control circuit 26 ^- [0004] Sawtooth VD ⁺ vertical period obtained in this manner, VD. The output from the gain control circuit 26 is input to a power operational amplifier 27. The vertical deflection coil 29 is driven by the power operational amplifier 27. Resistor for detecting vertical current 3
0, the input voltage V
D ^+, VD ^- difference is current amplified as a vertical deflection current.

[0005] However, since it is not possible to instantaneously return (retrace) due to the inductance of the coil, the current flowing through the coil, that is, the deflection current is di / dt = V
/ L (V is the voltage between both ends of the coil, and L is the inductance of the coil), and increases with the slope determined by VD shown in FIG.
^+, VD ^- actually will be scanning (trace) starts from the corresponding point B in the scanning period. This point B
6 becomes the peak of the deflection current. By superimposing a reference pulse on the video signal at this timing,
The distance from the effective screen is maximized as shown in FIG. The retrace period in FIGS. 5 and 6 indicates a retrace period.

[0006]

However, since the reference bright line generated by the reference pulse shines even when the screen is dark, it becomes very unsightly when it appears on the effective screen. Therefore, as shown in FIG. 6, the reference bright line is positioned outside the effective screen at the top of the screen so as to be invisible.

However, since the retrace time of the raster is determined by the constant of the vertical deflection circuit including the vertical deflection coil, if the retrace time is long, there is a possibility that the reference bright line will appear on the effective screen. Also,
A standard having a large effective rate of the signal in the vertical direction, for example, a digital television signal standard 1080I (effective rate 1080/112)
In the case of 5), when the retrace time is shortened in order to secure the display area of the reference bright line, if the reference pulse is positioned at the peak of the current when the vertical deflection current is in a sawtooth waveform as in the related art, the effective screen is displayed. When the raster is lowered due to an adjustment error, the influence of geomagnetism, or the like, the distance of the reference line may become visible.

Therefore, the present invention provides a vertical deflection system in which the reference bright line used in the automatic cut-off circuit can be positioned considerably outside the effective screen, and the position of the reference bright line can be varied according to the number of effective scanning lines. It is an object to provide a circuit and a video display device having the circuit.

[0009]

A vertical deflection circuit according to the present invention is capable of automatically adjusting a black level by inserting a reference pulse into a video signal and projecting a reference bright line by the reference pulse. The circuit includes a reference bright line arrangement unit for positioning the reference bright line outside the effective screen, and a reference bright line position adjusting unit for adjusting the position of the reference bright line outside the effective screen. It is characterized by the following.

A video display apparatus having a vertical deflection circuit according to the present invention is capable of automatically adjusting a black level by inserting a reference pulse into a video signal, projecting a reference bright line with the reference pulse, and automatically adjusting a black level. In the video display device having, reference bright line arrangement means for positioning the reference bright line outside the effective screen, and reference bright line position adjusting means for adjusting the position of the reference bright line outside the effective screen. And a vertical deflection circuit having the following.

In the vertical deflection circuit and the image display apparatus having the same according to the present invention, the reference bright line arranging means positions the reference bright line outside the effective screen, and the reference bright line position adjusting means places the reference bright line outside the effective screen. Can be adjusted. Thus, the reference bright line can be positioned considerably outside the effective screen, and the position of the reference bright line can be changed in accordance with the number of effective scanning lines.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a vertical deflection circuit according to the present invention will be described below with reference to the drawings. The present invention relates to a vertical deflection circuit which inserts a reference pulse into a video signal in order to suppress a change in black level due to aging, projects a reference bright line with the reference pulse, and can automatically adjust the black level. And a reference bright line arrangement means for positioning the reference bright line outside the effective screen, and a reference bright line position adjusting means for adjusting the position of the reference bright line outside the effective screen. With this arrangement, the reference bright line can be positioned considerably outside the effective screen, and the position of the reference bright line can be changed according to the number of effective scanning lines.

FIG. 1 is a circuit diagram showing an example of an image display device including a vertical deflection circuit according to the present invention. Deflection control IC
The (Integrated Circuit) 2 includes a vertical counter 3, a vertical oscillator 5, a pulse generator 6, and a gain / linearity control circuit 7. Vertical counter 3
, A vertical synchronizing signal Vs and a horizontal synchronizing signal 2fH having a frequency twice the horizontal oscillation frequency are supplied. The vertical counter 3 counts the horizontal synchronizing signal 2fH.
At s, the counter is reset. This reset pulse is supplied to the vertical oscillator 5.

When the vertical synchronizing signal Vs is not externally supplied, the vertical oscillator 5 keeps oscillating at a preset cycle. The gain / linearity control circuit 7 controls the pp value (peak value), time change (linearity), etc. of the vertical period sawtooth waves VD ⁺ and VD ⁻ obtained in this manner. The output from the gain / linearity control circuit 7 is input to the power operational amplifier 9. C
The vertical deflection coil 13 of the RT 12 is driven by the power operational amplifier 9.

The gain / linearity control circuit 7, which is a reference bright line position adjusting means, includes a peak hold circuit 7a. The pulse generator 6 generates a V pulse as a control pulse based on the reset pulse of the vertical counter 3. The width (time) of the V pulse is controlled by data and a clock from the microcomputer 10. The V pulse is input to the peak hold circuit 7a,
As shown in FIGS. 2B and 2C, the amplitude of the clamp point (retrace [feedback] start point) A of VD ⁺ and VD ⁻ is increased during the “H” period of the pulse, and the voltage is maintained. This clamp point A can also be changed by data and a clock from the microcomputer 10. The microcomputer 10 has a nonvolatile memory 15 as a storage unit for storing various data.
Is connected.

Further, the V pulse is input to a signal processing IC 11 as a reference bright line arranging means, and the V pulse is input to the signal processing IC 11 as shown in FIG.
As shown in (f), the signal processing IC 11 superimposes reference pulses (R, G, B) on the output video signal in synchronization with the fall of the V pulse from the “H” section.
Further, the signal processing IC 11 blanks the output video signal so that the CRT is cut off and blanked out in the "H" section of the V pulse, that is, the blanking section of the vertical deflection.

[0017] VD ^+, VD ^- the deflection current in the clamped portion by V pulses becomes larger than the conventional raster can also be increased by a portion thereof. The shape of this deflection current is such that a pulse is superimposed on the retrace (return) of the sawtooth wave, as shown in FIG. Since the deflection current has such a shape, the arrival point of the reference palace is located as shown by the dotted line in FIG. 3, and the distance of the reference bright line from the effective screen can be increased. In addition, since the section from the actual rear end of the video portion of the video signal to the reference pulse is set as a blanking section, a bright line in the retrace state cannot be seen, and a good screen state can be obtained. For this reason, blanking always occurs before the reference pulse, so that it is not necessary to adjust the blanking width depending on the position of the reference pulse. In FIG. 3, the dashed line indicates the position of the reference bright line by the conventional vertical deflection circuit.

Therefore, since the distance of the reference bright line from the effective screen can be increased, the reference bright line does not appear on the effective screen even if the retrace time is long. Also, a standard having a large effective rate of a signal in the vertical direction, for example, a digital television signal standard 1080I
In the case of (effective rate 1080/1125), the reference bright line is not seen even when the retrace time is shortened.

Further, since it is not necessary to add a circuit for shortening the retrace time more than before, it is possible to reduce the cost and improve the reliability.

Since the width and height of the portion clamped by the V pulse can be arbitrarily set by data and a clock from the microcomputer 10, various deflection yokes, CRTs
Can be supported.

Further, even in the case of the same CRT, data corresponding to the type of the signal to be displayed (the number of effective scanning lines, the aspect ratio) can be stored in the non-volatile memory 15. The type can be identified and the corresponding data can be read from the non-volatile memory 15, and the reference bright line can be extremely easily and reliably positioned at the optimum point. For example, in the case where data corresponding to the digital television signal standard 1080I is stored in the nonvolatile memory 15 in advance, if the signal standard to be displayed is identified as 1080I, the nonvolatile memory 15 corresponds to the 1080I. The data is read, and the reference bright line is positioned at an optimum point based on the data. If this function does not need to be used, it is possible to select a mode in which V pulse is not superimposed on the vertical sawtooth signal depending on data.

In the above-mentioned embodiment, the standard having a large effective rate of the signal in the vertical direction is, for example, the signal standard 1080I of a digital television. However, the present invention is not limited to this, and the signal standard of another television may be used. Of course.

[0023]

As described above, according to the present invention,
The reference bright line arrangement means for positioning the reference bright line outside the effective screen and the reference bright line position adjusting means for adjusting the position of the reference bright line outside the effective screen make the reference bright line considerably larger than the effective screen. Because it can be located outside, even if the retrace time is long, the reference bright line will not appear on the effective screen, and even if the signal has a high effective rate of the vertical signal, the reference bright line will not be visible. Not
A good screen state can be obtained.

Also, since data corresponding to the type of the signal to be displayed (the number of effective scanning lines, the aspect ratio, etc.) can be stored in the storage means, the type of the signal to be displayed is identified, and The data can be read out from the storage means, so that the reference bright line can be positioned extremely easily and reliably at the optimum point.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an example of a video display device including a vertical deflection circuit according to the present invention.

FIG. 2 is an output waveform diagram of each unit.

FIG. 3 is a diagram showing a relationship between a vertical deflection current, a reference pulse, and a reference bright line.

FIG. 4 is an example of a conventional vertical deflection circuit.

FIG. 5 is an output waveform diagram of each section of the related art.

FIG. 6 is a diagram showing a conventional relationship between a vertical deflection current, a reference pulse, and a reference bright line.

[Explanation of symbols]

2 ... deflection control IC, 3 ... vertical counter, 5 ...
..Vertical oscillator, 6 ... pulse generator, 7 ... gain linearity control circuit (reference bright line position adjusting means), 7a ... peak hold circuit, 9
... power operational amplifiers, 10 ... microcomputers, 11.
..Signal processing ICs, 12 ... CRTs (cathode ray tubes), 1
3: Vertical deflection coil, 15: Non-volatile memory (storage means)

Claims (5)

[Claims] 1. A vertical deflection circuit which inserts a reference pulse into a video signal, projects a reference bright line using the reference pulse, and can automatically adjust a black level. And a reference bright line position adjusting means for adjusting a position of the reference bright line outside the effective screen. 2. The vertical deflection circuit according to claim 1, wherein the reference bright line arranging unit superimposes a control pulse on a vertical sawtooth wave signal to position the reference bright line outside an effective screen. . 3. The reference bright line position adjusting means is capable of changing the position of the reference bright line according to the number of effective scanning lines on the screen, and includes a storage means for storing data thereof. Item 4. The vertical deflection circuit according to Item 1. 4. The vertical deflection circuit according to claim 1, wherein a section between an actual rear end of the video section of the video signal and the reference pulse is a blanking section. 5. A video display device having a vertical deflection circuit capable of inserting a reference pulse into a video signal, projecting a reference bright line using the reference pulse, and automatically adjusting a black level, wherein: Reference bright line arrangement means for positioning outside the effective screen, and a vertical deflection circuit comprising reference bright line position adjustment means for adjusting the position of the reference bright line outside the effective screen, Video display device.