JPH0666930B2 - Driving method of flat cathode ray tube - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a flat cathode ray tube used for a color television receiver, a terminal display of a computer and the like.

2. Description of the Related Art There is a flat cathode ray tube as a prior art having a structure shown in FIG. In reality, each electrode is built in a vacuum envelope (glass container), but the vacuum envelope is omitted in the figure to clarify the internal electrodes.
In addition, in order to clarify the horizontal and vertical directions of the screen for displaying images, characters, etc., a horizontal direction H
The vertical direction V is shown.

Reference numeral 10 denotes a long linear cathode in the V direction, in which an oxide cathode material is applied to the surface of a tungsten wire, and a plurality of linear cathodes are independently arranged at equal intervals in the horizontal direction. On the side opposite to the face plate portion 28 across the linear cathode 10, the linear cathode 10 is adjacent to the linear cathode 10 and is vertically divided at an equal pitch on the insulating support 11 and is electrically divided to be elongated in the horizontal direction. A vertical scanning electrode 12 is arranged. These vertical scanning electrodes 12 are formed as 1/2 independent electrodes of the number of horizontal scanning lines (about 480 in the NTSC system) in the vertical direction when displaying a normal television image. Next, between the linear cathode 10 and the face plate portion 28, a planar electrode having an opening at a portion corresponding to the linear cathode 10 and the vertical scanning electrode 12 is adjacently arranged in order from the linear cathode 10 side. First grid electrodes (hereinafter referred to as G1) 13 and G1 electrodes which are divided between the linear cathodes 10 and apply a video signal to the respective electrodes to perform beam modulation.
The second grid electrode (hereinafter G2) 14 and the third grid (hereinafter G3) 1 which have the same openings as those of 13 and are not horizontally divided.
Place 5 The G2 electrode 14 is for generating an electron beam from the linear cathode 10, and the G3 electrode 15 is for shielding between the electric field generated by the electrodes in the subsequent stage and the beam generating electric field. Next, a fourth grid electrode (hereinafter referred to as G4) 16 is arranged, and its opening is larger in the horizontal direction than in the vertical direction. FIG. 4A shows a horizontal cross section of FIG. 3, and FIG. 4B shows a vertical cross section. In the latter stage of the G4 electrode 16, two electrodes 17 and 18 each having an opening that is sufficiently wider in the horizontal direction than in the vertical direction are arranged as in the opening of the G4 electrode 16.
As shown in FIG. 4B, a vertical deflection electrode is formed by shifting the center axes of the apertures of the two electrodes in the vertical direction. In the subsequent stage of the vertical deflection electrodes 17 and 18, a plurality of vertically long electrodes are provided between the linear cathodes 10 toward the face plate portion 28 side. FIG. 3 shows a case of three stages as an example. Each electrode is a first horizontal deflection electrode (hereinafter referred to as DH-
1) 19, a second horizontal deflection electrode (hereinafter DH-2) 20, and a third horizontal deflection electrode (hereinafter DH-3) 21. Each horizontal deflection electrode 19-21
Are connected to the common buses 22, 23, 24 every other horizontal line.

The same voltage as the DC voltage applied to the metal back electrode 26 of the face plate portion 28 is applied to the DH-3 electrode 21,
A voltage for horizontally focusing the beam is applied to the -1 electrode 19 and the DH-2 electrode 20. A light emitting layer including a phosphor screen 27 and a metal back electrode 26 is formed on the inner surface of the face plate portion 28. In the color display, phosphor stripes of red R, green G, and blue B are sequentially formed in the horizontal direction through a black guard band during color display.

Next, the operation of the color cathode ray tube will be described. This is heated by passing an electric current through the linear cathode 10,
The same potential as that of the cathode 10 is applied to the electrode 13 and the vertical scanning electrode 12. At this time, a voltage higher than the potential of the cathode 10 (for example, 100 to 300 V) is applied to the G2 electrode so that the beam advances from the cathode 10 toward the G1 and G2 electrodes (13, 14) and the beam passes through each electrode opening. Apply to 14. Where the beam is G
To control the amount of light passing through each aperture of the G1 electrode, the G1 electrode 13
By changing the voltage of. The beam that passed through the aperture of G2 electrode 14 is G3 electrode 15 → G4 electrode 16 → vertical deflection electrode 1
7, 18 → horizontal deflection electrodes 19, 20, 21 are advanced, and a predetermined voltage is applied to these electrodes so that the electron beam becomes a small spot on the fluorescent screen 26. Here, the vertical beam focus is performed by the electrostatic lens formed between the G3 electrode 15, the G4 electrode 16, and the vertical deflection electrodes 17 and 18, and the horizontal beam focus is DH-1, DH-2, It is performed by the electrostatic lens formed between each of DH-3. The above two electrostatic lenses are formed only in the vertical direction and the horizontal direction, respectively.
Therefore, the vertical and horizontal spot sizes of the beam can be individually adjusted.

The bus lines 22, 23, and 24 to which DH-1 (19), DH-2 (20), and DH-3 (21) are connected have sawtooth waves, triangular waves, or staircase waves of the same voltage with a horizontal scanning period. Is applied to deflect the electron beam in the horizontal direction with a predetermined width,
An emission image is obtained by scanning 26 with an electron beam.

Next, vertical scanning will be described with reference to FIG.

As described above, by controlling the voltage of the vertical scanning electrode 12 so that the potential of the space surrounding the linear cathode 10 becomes a positive or negative potential than the potential of the linear cathode 10,
Generation of electrons from the linear cathode 10 is controlled. At this time, if the distance between the linear cathode 10 and the vertical scanning electrode 12 is small, a beam is generated (hereinafter ON) and cut off (OF) from the cathode.
The voltage controlling F) may be small. In the case of the current television system that adopts the interlace system, a predetermined deflection voltage is applied to the vertical deflection electrodes 18 and 19 for one field in the first first field, and the vertical scanning electrode 12 is
The beam ON voltage is applied to 12A only for one horizontal scanning period (hereinafter 1H), and the beam OFF voltage is applied to the other vertical scanning electrodes (12B to 12Z). After 1H, vertical scan electrode 12B
Only for 1H, the beam ON voltage is sequentially applied to the vertical scanning electrodes.
The voltage that turns on the beam is applied only for 1H,
When 12Z ends, the vertical scanning of the first field is completed. In the next second feed, the polarities of the deflection voltages applied to the vertical deflection electrodes 17 and 18 are reversed, and this is applied for one field. The signal voltage applied to the vertical scanning electrode 12 is the same as in the first field. At this time, the vertical deflection electrode is arranged so that the horizontal scanning line of the second field is located between the horizontal scanning lines of the beam by the vertical scanning of the first field.
The amplitude of the deflection voltage applied to 17, 18 is adjusted. As described above, the same vertical scanning signal voltage is applied to the vertical scanning electrode 12 in the first and second fields, and the deflection voltage applied to the vertical deflection electrodes 17 and 18 is changed between the first field and the second field. This completes vertical scanning of one frame.

Next, regarding a signal processing system until a video signal is applied to a beam modulation electrode of a cathode ray tube having a plurality of beam generating sources in the horizontal direction like the flat plate cathode ray tube, a generally well-known method is described below. This will be described with reference to FIG.

Based on the television sync signal 42, a timing pulse generator 44 generates a timing pulse for driving a circuit block described later. First, the R, G, B three primary color signals (E _R , E _G , E _B ) 41 demodulated by one timing pulse among them are A / D.
It is converted into a digital signal by the converter 43, and the 1H signal is input to the first line memory circuit 45. When all the signals for 1H are input, the signals are simultaneously transferred to the second line memory circuit 46, and the next 1H signal is also input to the first line memory circuit 45. The signal transferred to the second line memory circuit 46 is stored and held for 1H and is also a D / A converter (or pulse width converter).
The signal is sent to 47, where it is converted to the original analog signal (or pulse width modulation signal), amplified and applied to the modulation electrode G1 of the cathode ray tube. Such a line memory circuit is used for time axis conversion. It is what is done.

Problems to be Solved by the Invention Like the above-mentioned conventional example, having a large number of electron beam generation sources,
It is very difficult to keep the amount of beam obtained from all electron beam generation sources uniform over time in a flat-plate cathode ray tube that deflects the electron beams obtained from them horizontally and vertically to form the entire screen. .

The present invention has been made in view of the above points, and an object thereof is to provide a driving method for performing negative feedback control so as to keep the beam amount obtained from all electron beam sources uniform over time with a simple configuration. There is.

Means for solving the problem The amount of beam current emitted from each beam source is detected by the means for detecting the amount of beam current, and compared with a predetermined reference value,
The operation of increasing / decreasing the beam current amount by a predetermined unit by the means for controlling the beam current amount depending on the magnitude is periodically repeated.

Action If the beam current amount of the electron beam emitted from each beam source is larger than the predetermined reference value, the operation is repeated by decreasing the predetermined unit amount, and if the beam current amount is smaller, increasing the predetermined unit amount. Will converge to a predetermined reference value. That is, negative feedback control is performed on the beam current amount and the beam current amount is kept uniform over time.

Embodiment FIG. 1 is a partial perspective view of a flat panel cathode ray tube and a block diagram of a circuit system for performing negative feedback control of a beam current. G1
The electrode 13, the G2 electrode 14 ', and the G3 electrode 15' are divided in the horizontal direction corresponding to the cathode 10, but the other parts have the same configuration as the conventional example, and therefore the basic structure for displaying an image. The same operation is the same. A driving method for controlling the uniformization of the beam current will be described with reference to FIGS. 1 and 2.

Reference numeral 48 denotes a G1 electrode drive circuit, which creates a G1 electrode drive signal 58 by inserting a pulse 58 ′ having a predetermined time width and a predetermined voltage value in the horizontal blanking period into the video signal for beam modulation, and forms the G1 electrode 13 Apply to. 49 is a G4 electrode drive circuit,
A beam cutoff signal 60 is generated to cut off the beam emitted to the anode at the G4 electrode 16 during the horizontal blanking period.
It is for applying to the G4 electrode. Reference numeral 50 is a current detecting section for detecting the beam current flowing into the G3 electrode 15 '. Reference numeral 51 is a comparator, which makes a judgment as to whether the detected beam current value is large or small with respect to a predetermined level. 52
Is an adder / subtractor for adding 1 to or subtracting 1 from a certain value. Reference numeral 53 denotes a memory, which has the same number of addresses as the number of vertical scanning electrodes, and each address stores the voltage value applied to the G2 electrode 14 'at the corresponding address on the screen (that is, the position of the vertical scanning electrode). . Reference numeral 54 is a latch circuit that stores data read from the memory 53.
Latch for 1H period. A D / A converter 55 converts the data latched in the latch circuit 54 into an analog quantity. 56 is a G2 electrode drive circuit, and a D / A converter 55
The G2 electrode drive signal 59, which is obtained by amplifying the output of the
It is applied to the electrode 14 '. Next, the overall operation of each of the above parts will be described.

As shown in FIG. 2, vertical scan electrode drive signals 57a, 57b, ... Which turn on the beam every 1H period are sequentially applied to the vertical scan electrodes 12. The G1 electrode drive signal 58 is applied to the G1 electrode 13. At the same time, the data of the address corresponding to the on-screen address of the beam in the ON state is read from the memory 53, latched in the latch circuit 54 for 1H period, and D
The A / A converter 55 and the G2 electrode drive circuit 56 convert it into a G2 electrode drive signal 59 and apply it to the G2 electrode. Therefore, the beam current generated from the cathode 10 toward the anode is determined by the level of the G1 electrode drive signal 58 and the level of the G2 electrode drive signal 59, and the period of the pulse 58 ′ portion of the G1 electrode drive signal has a constant value. is there. Next, the beam is cut off by the beam cutoff signal 60 applied to the beam G4 electrode 16, and the beam is flown into the G3 electrode during the horizontal blanking period, which is detected by the current detector 50. This is compared with a predetermined level by the comparator 51, and if the result is large, 1 is subtracted from the data latched in the latch circuit 54 by the adder / subtractor 52, and if it is small, data is added to create 1 Then, the data after addition and subtraction is written in the address of the memory 53 corresponding to the address on the screen of the beam.

By performing the above-mentioned operation for all electron beams on the screen and repeating the operation at a certain cycle (for example, one field cycle), negative feedback control is performed so that the beam current has a constant value.

EFFECTS OF THE INVENTION As described above, the present invention simplifies negative feedback control in order to keep the electron beams obtained from all electron beam sources of a flat-plate cathode ray tube having a large number of electron beam sources uniform over time. It can be done in a configuration and is very effective in practice.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram including a partial perspective view showing a main part of a flat panel cathode ray tube circuit system in an embodiment of the present invention, and FIG. 2 is a signal shape and timing of each part in FIG. Waveform diagram showing
FIG. 3 is a perspective view of a conventional flat panel cathode ray tube, FIGS. 4A and 4B are horizontal and vertical cross-sectional views of the conventional flat panel cathode ray tube, and FIGS. 5A and 5B are the same flat panel cathode ray tube. 6 is an explanatory view of the vertical scanning of FIG. 6, and FIG. 6 is a signal system diagram for driving a flat-plate cathode ray tube. 48 …… G1 electrode drive circuit, 49 …… G4 electrode drive circuit, 50 ……
Current detector, 51 ... Comparator, 52 ... Adder / subtractor, 53 ... Memory, 54 ... Latch circuit, 55 ... D / A converter, 56
...... G2 electrode drive circuit.

Claims (3)

[Claims] 1. A flat cathode ray tube having at least a plurality of beam sources, a means for modulating the beam, a means for controlling the beam current amount, a means for detecting the beam current amount, and a screen which emits light when the beam strikes. In the driving method of
The beam current amount emitted from each beam source is detected by means for detecting the beam current amount and compared with a reference value,
A method of driving a flat cathode ray tube, characterized in that the operation of increasing or decreasing the beam current amount by a unit for controlling the beam current amount is periodically repeated according to the magnitude. 2. A beam is generated under a predetermined operating condition during a horizontal blanking period, and the beam current amount thereof is detected,
A patent characterized by repeating, for each field, subtracting or adding 1 to digitized voltage value data of the beam control electrode as means for controlling the beam current amount by comparing with a predetermined reference value Claim 1st
A method for driving a flat panel cathode ray tube according to the item. 3. A beam current control data corresponding to each beam source is written in a memory having an address corresponding to an address on a screen of each beam of a flat cathode ray tube which sequentially emits beams from a plurality of beam sources. Every other time, the beam current control data of the beam source in the beam emitting state is read from the memory in synchronization with the switching of the beam emission from each beam source, the beam current is controlled, and the beam current amount is compared with a predetermined reference value. Then, 1 is added to or subtracted from the beam current control data according to the result, and the operation of returning to the memory is periodically repeated.
Item 3. A method of driving a flat-plate cathode ray tube according to item 2 or 3.