JPH01232397A - Fluorescent display device - Google Patents

Abstract

PURPOSE:To easily warn and display the life of the above device by independently providing one of plural filaments of a fluorescent display tube and supplying the voltage which is larger in the effective value than the filament for warning the life disposed opposite to said independent filament to said filament. CONSTITUTION:A dummy electrode 12a for displaying the warning is disposed in addition to an anode 12. The independent filament F2 11a opposite to the dummy anode 12a is provided in parallel with the filament F1 11. The filament voltages Ef1 and Ef2 are supplied to the F1 11 and F2 11a and the effective values are so set as to attain Ef1<Ef2, by which the temp. of the filament F1 11 for ordinary display is set at the rated value and the temp. of the filament F2 11a is set higher than the rated value. The dummy electrode 12a is thus forced to arrive at the life point in the period earlier than the other anode 12 so that the anode 12a for displaying the warning hardly emits light at about the time when the other anode 12 arrives at the life point.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a fluorescent display device using a fluorescent display tube as a display element, and particularly to a fluorescent display device having a warning display.

[Conventional technology]

FIG. 3 is a block diagram showing an example of the basic configuration of a conventional fluorescent display device.

As shown in FIG. 3, the conventional fluorescent display device includes a fluorescent display tube 51, a drive circuit section 2 that supplies display drive voltage to the grid and anode of the fluorescent display tube 51, and a drive circuit section 2. It consists of a control circuit section 3 for controlling and obtaining a predetermined display, and a power supply circuit section 4 for supplying predetermined power to the fluorescent display tube 51, drive circuit section 2, and control circuit section 3. The power supply circuit section 4 normally includes a power supply A 41 . B and C supplying the anode and grid drive voltages
It is composed of three parts: a power supply 42 and a logic power supply 43 of the control section 3.

[Problem to be solved by the invention]

The lifetime of a fluorescent display device is determined by the lifetime of the fluorescent display tube, especially the filament.

This filament is a tungsten core wire with a diameter of 7 to 20 μm coated with a cathode material (usually an oxide of Ba or Sr), and when a current is passed through the filament, it is heated and excited electrons are emitted. During this electron emission, the oxide of the cathode material is gradually evaporated by heat, and as the evaporation evaporates, the emission decreases, and the evaporated oxide stains the surface of the phosphor and reduces the brightness.

For convenience, the lifespan of a fluorescent display tube is defined as the point in time when the luminance becomes 1/2 of its initial value. When the filament is used within its rating (filament temperature approximately 650°C), the average lifespan is 30,000 to 80,000 hours, and deterioration in brightness means a decline in display quality, so the lifespan is significantly exceeded. Its use should be avoided. Therefore, it is necessary to perform preventive maintenance before reaching the end of its service life to maintain display quality.

Possible means of preventive maintenance are periodic maintenance (-simultaneous replacement) and maintenance over time (individual advance replacement). In reality, since each device has a different usage time, maintenance is often performed over time. At this time, the actual operating time of each device is not necessarily clear, and the lifespan of the fluorescent display tube itself also varies, making it difficult to visually determine the lifespan point. As described above, the conventional fluorescent display device has a drawback in that it is not possible to accurately determine the timing of maintenance over time.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fluorescent display device that has a life warning display that allows the end of life to be visually determined, and that makes it easy to determine when to perform maintenance over time.

[Means to solve the problem]

The present invention provides a fluorescent display tube including a plurality of filaments and an anode, a drive circuit section for driving and displaying the fluorescent display tube, a control circuit section for controlling the drive circuit section, and a fluorescent display tube. and a power supply circuit section that supplies power to each of the drive circuit section and the control circuit section, wherein one of the filaments of the fluorescent display tube has an independent filament terminal. and a dummy anode is provided opposite to the filament stretched between the filament terminals, and further, an effective voltage value supplied from the power supply circuit section to the filament terminal is supplied to the other filaments. It is higher than the effective voltage value.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the present invention;
Figures (a) and (b) are a block diagram showing the main parts of Figure 1 and a block diagram of a power supply circuit.

In the first embodiment, as shown in FIG. 1, compared to FIG. 3, the fluorescent display tube 1 is provided with an independent filament F2 in addition to the conventional filament F1, and F! And filament voltage Er+, Er from the A power supply 41 of the power supply circuit section to F2
This differs from the conventional example in that z is supplied individually.

FIG. 2(a) is a block diagram for explaining the main part of FIG.
An independent filament F211a facing 2a,
It is suspended parallel to the conventional filament F111.

Filament voltages Efl and Ef2 are independently supplied to Flll and F211a, respectively.

Now, as mentioned above, the luminance deterioration of the fluorescent display tube 1 is mainly due to the fact that the oxide, which is the cathode material of the filament F111, evaporates due to the heat generated during electron emission, gradually reducing the emission ability. In the ordinary fluorescent display tube 1, the rated voltage is determined so that the temperature of the filament F111 is about 650°C. The higher the temperature, the faster the rate of deterioration. Since the temperature of the filament F111 is approximately directly proportional to the voltage of the filament Fll, E t
By setting the effective value of the filament voltage so that 1<E F2, the normal display filament F
The temperature of the ILL can be set to the rated value of 650° C., and the temperature of the independent filament F211a can be set higher than the rated value. As a result, the dummy anode 12a is connected to the other anode 12.
It reaches the end of its life earlier than the previous year. By utilizing this characteristic, the warning display anode 1 can
2a can be made to emit almost no light. For example, if Er2 is set so that the temperature of the filament F211a is 980°C, which is approximately 1.5 times the rated temperature, by the time the other anodes 12 reach the cold point, the brightness of the warning anode 12a will be reduced to the initial 10°C.
% to about 20%.

FIG. 2(b) shows an embodiment of a power supply circuit, which is a C-DC converter, which is the most common power supply circuit for a fluorescent display device, and relies on a blocking oscillation circuit. Terminals 101 to 104 are terminals for supplying filament voltage, and normally the output of a pulse transformer is used as an alternating current. This AC voltage is used in a range of about 10 to 100 KHz, and the number of turns on the secondary side of the transformer is adjusted so that the effective values of Efl and Er2 satisfy the above-mentioned relationship. The terminal 105 is a voltage supply terminal for driving the anode and the grid, and the anode and the grid are often used at the same potential in this way. The power supply for the control circuit is the input for the fluorescent display device. In the first embodiment described above, the case where the filament is driven with alternating current is explained, but here, as a second embodiment, the case where the filament is driven with direct current will be explained ( (not shown). Era and Er of the first embodiment
If the effective value of 2 is replaced with the DC voltage value, exactly the same effect can be obtained, and a warning display regarding the end of life can be made possible. In recent years, applications for in-vehicle displays have increased, and examples of filament drive using direct current are increasing. Even in such a case, the warning display according to this embodiment is possible as described above.

〔Effect of the invention〕

As explained above, the present invention provides a fluorescent display device comprising a fluorescent display tube, a drive circuit section, a control circuit section, and a power supply circuit section, in which one of the plurality of filaments of the fluorescent display tube is By making the filament independent and facing it and supplying a voltage with a larger effective value than the life warning filament from the power supply circuit, it is possible to display the life warning, and maintenance over time, which was difficult in the past, is possible. This has the effect of making it easier to determine the implementation timing.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention;
Figures (a) and (b) are block diagrams showing the main parts of Figure 1 and a block diagram of a power supply circuit, and Figure 3 is a block diagram of an example of a conventional fluorescent display device. DESCRIPTION OF SYMBOLS 1... Fluorescent display tube, 2... Drive circuit section, 3... Control circuit section, 4... Power supply circuit, 11. lla...Filament, 12.12a...Anode, 21...Anode driver, 22...Grid driver, 41...A power supply, 42...B and C power supply, 43...For logic Power supply, 51... Fluorescent display tube. 101-104...Filament terminal, 105...Anode and grid terminal.

Claims (1)

[Claims] A fluorescent display tube including a plurality of filaments and an anode, a drive circuit section for driving and displaying the fluorescent display tube, a control circuit section for controlling the drive circuit section, the fluorescent display tube and the drive circuit. and a power supply circuit section for supplying power to each of the control circuit sections, wherein one of the filaments of the fluorescent display tube has an independent filament terminal, and , a dummy anode is provided opposite the filament stretched between the filament terminals, and further,
A fluorescent display device characterized in that an effective voltage value supplied to the filament terminal from the power supply circuit section is higher than an effective voltage value supplied to the other filaments.