JPH1175082A - Video display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the excessive scanning or scanning shortage of a video signal on a raster, to prevent the loss of picture information, and to sufficiently use a display screen by selecting horizontal or vertical deflection amplitude according to the characteristics of a video signal. SOLUTION: A decoder 41 connects the signal of a terminal 43 with a terminal 46, and connects the terminal 46 through a resistance 50 with a feedback input terminal 48 of a vertical deflection circuit 11 by the high level signals of terminal A and B. Terminals 44, 45, and 47 are also connected through resistance with different resistance values. Raster height is decided according to the value of the resistance between the movable arm of a manual raster height adjusting resistance 42 and the feedback terminal 48 in a feedback path, and the decoder 41 controls a vertical raster size according to a size signal applied through the terminals A and B. Then, for example, all the change of deflection currents caused by the fluctuation of a power supply voltage is compensated by the feedback circuit of the vertical deflection circuit 11. Therefore, even at the time of selecting any height for the raster height, stability can be maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video display device, and more particularly to a video display device having a function of realizing a plurality of different raster dimensions.

[0002]

BACKGROUND OF THE INVENTION Video display devices, such as television receivers and computer monitors, typically generate one or more electron beams and deflect or scan these beams across a fluorescent display screen. It has a cathode ray tube that draws a raster. This raster determines the size and shape of the observable area on the screen when a video signal is present.

If the video display is to be used as a computer monitor, it is desirable that the monitor can be used with products of other computer manufacturers, or in combination with different types of computer devices made by the same manufacturer. Different types of computers may have different amounts of video information per horizontal scan line, or may generate different video signals that include different numbers of scan lines per field. For example, erasure (blanking)
The ratio of valid video information to time period is different between video signals having different resolution characteristics.

[0004]

If the amplitudes of the horizontal and vertical deflections are not selected in accordance with the characteristics of the video signal, overscanning or underscanning of the video signal on the raster will occur, and in the event of underscanning, the display screen will be overshot. If the state is not fully utilized, or if overscanning occurs, image information will be lost.

[0005]

According to one aspect of the invention, means for adjusting the raster width of an image by controlling the horizontal deflection amplitude, a deflection stage for generating a horizontal deflection current, and a) deflection amplitude. B) decoding the digitally encoded signal and responding to information embodied in the digitally encoded signal to one of the plurality of signals. A decoding means responsive to a DC bias level and controlling a horizontal deflection current in response to a vertical velocity parabola signal to correct horizontal deflection distortion; A switchable current branch that determines a bias level of the generating means changes the DC bias level in response to one of the plurality of signals to determine a selected raster width. Means for further displaying the video display device.

According to another feature of the present invention, a means for adjusting the raster height of an image by controlling the vertical deflection amplitude, a deflection stage for generating a vertical deflection current, and a value of the vertical deflection current Responding and providing a feedback signal that is fed back to the deflection stage;
Means for sampling the vertical deflection current; a) receiving a digitally encoded signal related to the deflection amplitude; and b) decoding the digitally encoded signal and embodied in the digitally encoded signal. Decoding means for generating one of a plurality of signals in response to the received information, and the feedback in response to one of the plurality of signals to generate a selectable change in the raster height. Means for altering the signal.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A horizontal deflection circuit 10, a vertical deflection circuit 11 and a cathode ray tube 12 according to an embodiment of the present invention are shown in FIG.
Of the video display device including the above. The cathode ray tube 12
For example, a drive signal D from a video processing circuit (not shown)
Is applied to the electron gun assembly 18. The electron gun assembly 18 generates one or a plurality of electron beams that cause the fluorescent display screen 19 to emit light upon impact. The horizontal deflection circuit 10 includes, for example, a TDA 2595 type integrated circuit, and applies a switching signal to the base of the drive transistor 13. When the drive transistor 13 is switched (switched), the horizontal output transistor 14 is switched via the drive transformer 15. The collector of the horizontal output transistor 14 is connected to the primary winding 16 of the output transformer 17.
To a + 97V class B + voltage source. Transformer 17 is shown as having a secondary winding 20 that produces a high voltage, which is applied to a high voltage or anode terminal 21 of cathode ray tube 12. The horizontal deflection circuit further includes a damper diode 22 and a retrace circuit.
It has capacitors 23, which work in a conventional manner, producing a retrace pulse across the terminals of primary winding 16 when transistor 14 is switched off. Further, by the switching of the horizontal output transistor 14, a horizontal deflection current flows through the terminal HH 'to the horizontal deflection winding 24 disposed at the neck of the cathode ray tube 12. The horizontal deflection winding 24 forms a part of a deflection yoke that deflects the electron beam from the electron gun assembly 18 to form a raster on the display screen 19.

The horizontal deflection circuit also includes a linearity coil 25, an S-shaped capacitor 29, and a diode modulator circuit for correcting east-west, ie, left and right pincushion raster distortion. This diode modulator comprises an inductor 27,
It has a damper diode 30, a modulator retrace capacitor 31, a modulator trace capacitor 26, and control transistors 32 and 33. The diode modulator performs a normal operation and modulates the horizontal deflection current in a parabolic manner at the vertical deflection frequency to correct left and right pincushion distortions.

The vertical deflection circuit 11 is, for example, a TDA 2
A type having a 653A type integrated circuit may be used, but a vertical deflection current flows through the vertical deflection winding 34 through the terminals V and V '. The deflection winding 34 is also provided on the neck of the cathode ray tube 12, and forms a part of the deflection yoke together with the horizontal deflection winding 24. The vertical deflection current sawtooth signal is supplied to the resistor 35.
And a capacitor 36 to form a vertical frequency parabolic signal, which is applied to the base of the control transistor 32 of the diode modulator circuit described above.

In accordance with one aspect of the present invention, the illustrated video display includes a raster size selection circuit 40 having a decoder 41. The decoder 41 is exemplified as a CD4052B type separation (demultiplex) circuit manufactured by RC Corporation. The decoder 41 has input terminals A and B
And accepts a binary signal. This signal determines one of four possible combinations of horizontal and vertical raster dimensions based on the binary input value. The desired horizontal and vertical dimensions are determined as follows.

The sample signal generated across the resistor 39 and extracted from the vertical deflection current is applied to a terminal 43 of a decoder 41 via a manual raster height adjustment resistor 42.
The decoder 41 acts essentially as a switch and the terminal 43
Is applied to terminals 44 and 4 via a low resistance path of about 400 ohms in response to signals received at terminals A and B.
5, 46, or 47. For example,
In accordance with the decoding or demultiplexing logic of decoder 41, decoder 41 couples the signal at terminal 43 to terminal 46 with a high level signal representing a digital "1" at both terminals A and B. The terminal 46 is, for example, TDA 2
Vertical deflection circuit 11 which is pin 4 of the 653A type integrated circuit
Are connected via a resistor 50 to a feedback input terminal 48 of Terminals 44, 45 and 47 are also connected to the feedback input terminal 4 of the vertical deflection circuit 11 through respective resistors having different resistance values.
8. The value of the resistor contained in the return path between the movable arm of the manual raster height adjustment resistor 42 and the feedback terminal 48 determines the raster height, so that the decoder 41 is selected through terminals A and B and is selected. It serves to control the vertical raster size in response to the size signal. Since this decoder 41 for determining the selected raster height is included in the linearity and height feedback loop, any change in deflection current due to, for example, fluctuations in the power supply voltage will be all vertical deflection circuit 11
Is compensated by this feedback circuit. Therefore, the raster height is stably maintained when any height is selected.

In accordance with yet another aspect of the present invention, to control the raster width, decoder 41 switches terminal 51 to terminals 52 and 5 in response to the levels of signals applied to terminals A and B.
One of 3, 54 and 55 is coupled through a low resistance path. The decoder 41, according to its operation logic, has a terminal 4
4, 45, 46 and 47 and terminals 52, 5
3, 54 and 55 are simultaneously selected and connected to the terminals 43 and 51, respectively.
Selectable combinations of terminals. Therefore, the selection of one of the terminals 52, 53, 54 and 55 is used to determine the horizontal raster width. As shown, terminals 53, 5
4 and 55 are coupled to each other in the same manner as terminals 45 and 47. In this way, a particular combination of raster height versus raster width is controlled. The raster width is determined as follows. Transistor 56 is connected to terminal 5 through voltage divider 60.
It has a base connected to two. Transistor 57
Are connected to terminals 53, 54 and 5 through a voltage divider 61.
5. The collectors of transistors 56 and 57 are coupled to each other through resistors 62 and 63, respectively, and to the base of diode modulator control transistor 32 through resistor 64. Since the terminal 51 is grounded, the terminal 52 or the terminals 53, 54 or 55
Are coupled to the terminal 51 in response to the signals at the terminals A and B, the bases of the transistors 56 and 57 are pulled down to a low potential, and the corresponding transistors are turned on. Resistance 6
2 and 63 have different resistance values, the DC bias of the control transistor 32 is
7 depending on which one is conducting, ie,
It is determined by the terminal selected by the raster size selection signal applied to terminals A and B. The DC bias of the control transistor 32 determines the continuity of the transistors 32 and 33 in response to the parabolic waveform from the vertical deflection circuit 11, and substantially determines the amount of deflection current modulation and thus the raster width.

In the particular embodiment shown, for each of the four possible logical combinations of signals applied to terminals A and B, which of terminals 44, 45, 46 and 47 is connected to terminal 43. Or terminals 52, 53, 54
Which of 55 and 55 is connected to terminal 51 is as shown in the following table.

[0014]

[Table 1]

As is apparent from FIG. 1, the above-mentioned raster size selection circuit has four different raster heights and different raster widths.
It can be used to select a combination of species. Regardless of the raster size selected, a stable raster pattern can be obtained.

[Brief description of the drawings]

FIG. 1 is a partial block circuit diagram showing a main configuration of an example video display device embodying the present invention.

[Explanation of symbols]

A, B display signal receiving means (input terminal) 10 horizontal deflection circuit 11 vertical deflection current generation means (vertical deflection circuit) 12 cathode ray tube 14 horizontal deflection current generation means 32, 33 horizontal deflection current control means (both control transistors) 39 sampling Means (resistance) 40 Raster size selection circuit 41 Horizontal deflection current control means or deflection means (decoder) of feedback means (48) 48 Feedback means

Claims (2)

[Claims] A means for adjusting the raster width of the image by controlling the horizontal deflection amplitude; a deflection stage for generating a horizontal deflection current; a) receiving a digitally encoded signal related to the deflection amplitude; A) decoding means for decoding the digitally encoded signal to generate one of a plurality of signals in response to information embodied in the digitally encoded signal; And means for controlling the horizontal deflection current in response to a vertical velocity parabola signal to correct horizontal deflection distortion, and a switchable current branch, the selection of which determines a bias level of the horizontal deflection current generation means. Means for changing the DC bias level in response to one of the plurality of signals to determine a selected raster width. 2. A means for adjusting a raster height of an image by controlling a vertical deflection amplitude; a deflection stage for generating a vertical deflection current; and a feedback to the deflection stage in response to a value of the vertical deflection current. Means for sampling a vertical deflection current to provide a feedback signal; a) receiving a digitally encoded signal related to deflection amplitude; and b) decoding the digitally encoded signal to provide the digitally encoded signal. Decoding means for generating one of a plurality of signals in response to information embodied in the signal obtained, and decoding the plurality of signals to generate a selectable change in the raster height. Means for changing the feedback signal in response to one of the two.