JP2000163017A - Filament cathode driving method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize stable display operations and also to improve the utilization efficiency of a power source current. SOLUTION: Relating to the display tube of a dynamic driving that thermoelectrons radiated from filament cathodes are irradiated on desired phosphor pixels among plurally provided phosphor pixels by successively impressing a voltage on respective plural grid electrodes, the filament cathodes are heated by impressing a pulse voltage on the filament cathode which is confronted with the grid electrodes on which the voltage is not impressed when the voltage is impressed on either of the grid electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for driving a filament cathode, and more particularly to a method for driving a filament cathode used in a picture tube or a fluorescent display tube.

[0002]

2. Description of the Related Art Conventionally, an image tube used for outdoor large-screen display or the like has a plurality of phosphor pixels arranged in a matrix on a display surface, and is caused by the collision of thermoelectrons irradiated from a filament cathode. It emits light and displays an image. In some of such image tubes, a plurality of phosphor pixels having different emission colors are integrated on a display surface to enable color display. At present, one pixel is divided into a plurality of regions in order to perform higher-gradation display, and a phosphor having a different emission color is applied to each of the divided regions.

FIG. 2 is an exploded perspective view showing the above-mentioned conventional picture tube. As shown in FIG. 1, an insulating substrate 2 is placed on a glass substrate 1, and a Y grid 4 serving as a control electrode is provided on the insulating substrate 2 in a 12 × 4 matrix.
These Y grids 4 are used to select phosphor pixels to be turned on, and the details thereof will be described later.

On each of the Y grids 4, a filament cathode 5 is stretched in the Y direction. Here, a total of 3.times.4 filament cathodes 5 are arranged in four control electrodes 4 arranged in the Y direction. It is arranged so as to straddle the top. Further, a plurality of lead pins 3 are drawn out from the edge of the glass substrate 1, and these lead pins 3 are connected to the Y grid 4, the filament cathode 5 and the like under the insulating substrate 2. Therefore, the supply of the driving voltage and the control signal of the picture tube is performed through these lead pins 3.

Next, on each filament cathode 4, four X grids GX1 to GX having electron passing holes are provided.
A shield electrode 6 made of a material 4 is disposed orthogonal to the filament cathode 4. And these X grid G
On the X1 to GX4, an anode electrode 7 integrally formed in a lattice shape is disposed. Therefore, after the irradiation direction of the thermoelectrons emitted from the filament cathode 5 is controlled by the Y grid and the X grid, the thermoelectrons are drawn out by the anode electrode 7 and the windshield 9
A desired phosphor pixel 10 disposed above is irradiated.

The respective phosphor pixels 10 emit phosphor colors different from blue, green and red, respectively.
The front glass 9 has a frame-like spacer glass 8 adhered along its edge with frit glass or the like.

As described above, in the picture tube shown in FIG. 2, various parts are arranged on the glass substrate 1, and these parts are coated with the frame-shaped spacer glass 8 and the phosphor to form a display surface. It is made by being covered with a glass container constituted by the windshield 9 and being hermetically sealed and exhausted.

Next, in describing the operation of such a picture tube, the correspondence between the X grid and the filament cathode will be described.

FIG. 3 shows phosphor pixels 10 and X grids GX1 to GX4 when the display surface of the picture tube is viewed from above.
FIG. 5 is an explanatory diagram showing a positional relationship between the filament cathode 5 and the filament cathode 5. As shown in the figure, the phosphor pixels 10 are arranged in a 4 × 4 matrix on the inner surface of the windshield 9 in FIG. 2, and below the four phosphor pixels 10 arranged in the X direction. And X grids GX1 to GX4 are arranged as a set. Under the X grids GX1 to GX4, a total of 12 filament cathodes 5 are provided orthogonally to the X grids GX1 to GX4 over a plurality of pixels in the Y direction.

At this time, each filament cathode 5 is arranged corresponding to each of the phosphor pixels 10B, 10G, 10R. And each filament cathode 5
Has terminals F1 and F2 at both ends thereof, and has a center tap terminal N at a central portion when considered electrically. Accordingly, the filament voltage is applied to a region from the center tap terminal N to the terminal F1 (hereinafter, referred to as a filament cathode group FL1) and a region from the center tap terminal N to the terminal F2 (hereinafter, referred to as a filament cathode group FL2). It is supposed to be.

As described above, each phosphor pixel 10B, 10
Since G and 10R each have a filament cathode at a position facing each other, and have an X grid and a Y grid shown in FIG. 2, desired phosphor pixels (10B, 10G, 10R) can be selected by selecting the X and Y grids. Can be turned on independently.

[0012] Therefore, by emitting a desired one of the three phosphor pixels 10B, 10G, and 10R in one phosphor pixel 10, various emission colors can be obtained. For example, 10B, 10
The light emission color becomes white by lighting all of G and 10R, and becomes yellow by lighting only B and G. Also,
By appropriately adjusting the voltage value applied to the X grids GX1 to GX4, the luminance can be easily adjusted.

Next, FIG. 4 for explaining a conventional operation method of such a picture tube is a time chart showing a relationship between a grid voltage and a filament voltage. As shown in the figure, in a dynamically driven picture tube, a grid voltage is applied while sequentially scanning X grids GX1 to GX4. Then, the filament cathode group F
L1 and FL2 are heated by applying a voltage irrespective of the grid voltage, and the emission of thermoelectrons is promoted. At that time, conventionally, an AC voltage was applied to the filament cathode 5, or a pulse voltage having a constant period as shown in FIG. 4 was applied.

Therefore, the lighting of the phosphor pixels is performed as follows. That is, the filament cathode 5 is heated by applying an AC voltage or a pulse voltage to the filament cathode 5, and a thermal potential is generated between the anode electrode 7 and the filament cathode 5 in this state, so that thermoelectrons are emitted from the filament cathode 5. . Then, the emitted thermoelectrons are selected by the X grids GX1 to GX4 and the Y grid 4, and are applied to desired phosphor pixels. As a result, the phosphor pixels irradiated with the thermoelectrons are turned on.

[0015]

However, if an AC voltage is used to drive the filament cathode, the waveform is a sinusoidal waveform, so that the display reference potential at the filament cathode fluctuates under the influence of the sinusoidal waveform. The brightness fluctuates. Therefore, such a method has a problem that it is not suitable for a case where a fine gradation display is desired and a display tube which requires fine luminance setting.

When a voltage pulse applied irrespective of the grid voltage is used to drive the filament cathode, the display reference potential fluctuates in the same manner as when an AC voltage is used, and the display luminance fluctuates. There is.
In particular, since the pulse has a rectangular waveform, the display reference potential changes instantaneously and abruptly.

Further, as is apparent from FIG. 4, in the prior art, an AC voltage or a voltage pulse was simultaneously applied to the entire area of the filament cathode, that is, to both of the filament cathode groups FL1 and FL2. There is a problem that the current is concentrated in a short time and the utilization efficiency of the power supply current is reduced.

The present invention has been made to solve such a problem, and provides a filament cathode driving method capable of realizing a stable display operation and improving the utilization efficiency of a power supply current. The purpose is to:

[0019]

In order to achieve the above object, a filament cathode driving method according to the present invention according to the first aspect of the present invention provides a filament cathode driving method in which a voltage is sequentially applied to each of a plurality of grid electrodes. When a voltage is applied to any of the grid electrodes in a dynamically driven display tube that irradiates a desired one of a plurality of phosphor pixels provided with thermoelectrons radiated from the The filament cathode is heated by applying a pulse voltage to the filament cathode opposite to the grid electrode to which is not applied.

According to a second aspect of the present invention, there is provided a filament cathode driving method according to the first aspect, wherein the phosphor pixels are formed as a set of a plurality of phosphor pixels having different emission colors. .

According to a third aspect of the present invention, there is provided a filament cathode driving method according to the first or second aspect, wherein the phosphor pixels are arranged in a matrix.

According to a fourth aspect of the present invention, there is provided a filament cathode driving method according to any one of the first to third aspects, wherein the display tube is a fluorescent display tube or a picture tube. .

With such a configuration, the present invention provides
When the phosphor pixel is turned on, the display reference potential of the filament cathode located at a position facing the phosphor pixel can be kept constant, so that a stable display operation can be realized. Further, since no voltage is applied to the entire area of the filament cathode at the same time, the efficiency of using the power supply current can be improved.

[0024]

Next, one embodiment of the present invention will be described with reference to the drawings. First, the picture tube used in the present embodiment is the same as that shown in FIG. 4, and has the following differences in driving the filament cathode.

FIG. 1 is a time chart showing one embodiment of the present invention. As shown in the figure, in order to perform dynamic driving, voltage pulses are applied to each of the X grids GX1 to GX4 while being shifted by a predetermined pulse width. Here, the pulse width of the grid pulse is t _pg , and the blanking time is t _b .

At this time, the filament voltage is applied as follows. For example, when a voltage is applied to the X grid GX1, a voltage pulse is applied only to the filament cathode group FL2, and when a voltage is applied to the X grid GX2, no voltage pulse is applied to any filament cathode group. Similarly, when a voltage is applied to the X grid GX3, a voltage pulse is applied only to the filament cathode group FL1, and when a voltage is applied to the X grid GX4, no voltage pulse is applied to any filament cathode group. .

As a result, for example, when the phosphor pixels 10 on the X grid GX1 or GX2 are turned on, the filament cathode group FL arranged corresponding to these is turned on.
Since no voltage pulse is applied to No. 1, the display reference potential in the filament cathode group FL1 is kept flat. Similarly, when the fluorescent pixels 10 on the X grids GX3 or GX4 are turned on, no voltage pulse is applied to the filament cathode group FL2 arranged corresponding to them, so that the display reference in the filament cathode group FL2 The potential is kept flat.

Therefore, when the phosphor pixel is lit, the potential of the filament cathode below it does not fluctuate, so that a constant brightness can be always maintained. Further, since a voltage is alternately applied to the filament cathode groups FL1 and FL2 at a constant period, the output of the power source may have an output enough to drive one of the filament cathode groups. Further, since the voltage pulse is applied at a constant period, there is an effect that the efficiency of using the power supply current is improved.

Since the number of pulses applied per unit time is reduced as compared with the conventional example, the pulse width t _pf
In addition, it is necessary to appropriately adjust the voltage value so as to obtain the same effective value as the conventional example. Of course, it is necessary to consider the pulse width t _{pg of the} voltage applied to the X grid and the blanking time t _b, and in the case of FIG.
_pf <(t _pg + t _b ) × 2

Further, in this embodiment, the filament cathodes are divided into two groups with the center tap terminal N as a boundary, but the invention is not limited to this. Therefore,
Two or more groupings may be performed. For example, FIG.
If the filament cathodes 5 are provided for each phosphor pixel instead of the filament cathodes extending over four pixels as in the above, a maximum of four groups can be formed. In that case,
When the phosphor pixels on the X grid GX1 are turned on, a voltage pulse may be applied to the filament cathodes below the other X grids GX2 to GX4. Furthermore, although an example of a picture tube has been described above, it is apparent that the present invention is not limited to this but can be applied to a fluorescent display tube.

[0031]

As described above, according to the present invention, when a voltage is applied to any of the grid electrodes, the pulse voltage is applied to the filament cathode located at a position opposite to the grid electrode to which this voltage is applied. Is applied to heat the filament cathode. Therefore, when the phosphor pixel is turned on, the display reference potential of the filament cathode located at a position facing the phosphor pixel can be made constant, so that a stable display operation can be realized. Also, since no voltage is applied to the entire area of the filament cathode at the same time,
The utilization efficiency of the power supply current can be improved.

[Brief description of the drawings]

FIG. 1 is a time chart showing one embodiment of the present invention.

FIG. 2 is an exploded perspective view showing a conventional picture tube.

FIG. 3 is an explanatory diagram showing a correspondence between a grid electrode and a filament cathode.

FIG. 4 is a time chart showing an operation of the picture tube according to FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Glass substrate, 2 ... Insulating substrate, 3 ... Lead pin, 4 ...
Y grid, 5: filament cathode, 6: shield electrode, 7: anode electrode, 8: spacer glass, 9: front glass, 10, 10B, 10G, 10R: phosphor pixel, FL1, FL2: filament cathode group, GX
1 to GX4... X grid.

Claims (4)

[Claims] 1. A dynamic system in which a voltage is sequentially applied to each of a plurality of grid electrodes to irradiate a desired one of a plurality of phosphor pixels with thermoelectrons emitted from a filament cathode. In the driving display tube, when a voltage is applied to any of the grid electrodes, the filament cathode is heated by applying a pulse voltage to a filament cathode facing the grid electrode to which no voltage is applied. And a filament cathode driving method. 2. The filament cathode driving method according to claim 1, wherein the phosphor pixels are configured as a set of a plurality of phosphor pixels having different emission colors. 3. The filament cathode driving method according to claim 1, wherein the phosphor pixels are arranged in a matrix. 4. The filament cathode driving method according to claim 1, wherein the display tube is a fluorescent display tube or an image tube.