JPH0511640B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a drive device for a display discharge tube that uses gas discharge to display characters, figures, and the like.

Conventional technology As shown in FIG.
a, 2b, . A large number of strip cathodes 7a, 7b, .
...... is attached, and the front glass plate 1 and the back glass plate 6 are attached.
and are hermetically sealed with a low melting point glass layer 9 provided on the periphery of both as shown in FIG.
A display discharge tube filled with a mixed gas of argon and a small amount of mercury is known from Japanese Patent Laid-Open Publication No. 151326/1983.

Such display discharge tubes emit various characters and figures by selectively combining a large number of intersection areas where cathodes and anodes intersect with each other to maintain a pilot discharge state or a display discharge state. The operating principle is as follows.

FIG. 5 representatively shows one strip-shaped anode 2a, five strip-shaped cathodes 7a, 7b, ... 7e, and the circuit members connected to each. Switches 10a, 10b...10
This is achieved by sequentially and instantaneously switching the on state of e. When the anode switch 11a is turned on during this Y-direction scanning period, a display discharge is instantaneously generated in the intersection area between the anode 2a and the cathode. The time-series on/off state of the anode switch 11a is shown in FIG. The result will be as shown in a.

Further, the anode potential Va and the discharge current Ia are as shown in b and c in FIG. 6, respectively, and the potentials of the cathodes 7a, 7b, . . .
...The results are as shown in h.

Here, the reason why the blanking period _t0 is provided on both sides of the cathode on-potential period _t1 in which the cathode potential becomes 0V is that the cathode switches 10a, 10b...10e
This is to prevent erroneous display from occurring even if there is a time delay in the switching operation of the switching transistor that plays the role of switching, and to generate the pilot discharge described below. That is, the potential Va of the anode 2a changes during the blanking period as shown in b in FIG.
During t ₀ , the voltage approaches the voltage Vs of the DC power source 13, and decreases to the discharge sustaining voltage Vm when the anode switch 11a is in the on state during the next cathode on-potential period t ₁ . The discharge current Ia passing through the resistor 14 having a resistance value Ra has a magnitude expressed by Ia=(Vs-Vm)/Ra.

When the anode switch 11a remains off during the cathode on-potential period _t1 , the charge accumulated in the anode stray capacitance 12 and the capacitor 4a causes a pilot discharge in the intersection area of the cathode and the anode. , and both Q of the charges are Q=(Cs+Ca)
It is expressed as ×(Vs−Vd). However, Vd indicates the anode potential at the time of stopping discharge.

Although this pilot discharge disappears in a short time, if a pilot discharge occurs in an intersection area that does not cause a display discharge, charged particles and excited atoms may be diffused into the adjacent intersection area that is then scanned, resulting in an erroneous discharge. The display operation can be performed stably without causing any discharge delay or the like.

By the way, a practical operating circuit is as illustrated in FIG. That is, a large number of transistors 15 that operate as the cathode switches described above
A, 15b...15e are connected to a scanning circuit 16, and a scanning signal generating circuit 17 connected to this scanning circuit 16 receives a horizontal synchronizing signal having a pulse width of t ₀ + t ₁ and a refresh period of the display screen. A vertical synchronization signal is provided to determine the Then, a scanning signal that can generate a blanking period t ₀ and a cathode on-potential period t ₁ is sent from the scanning signal generation circuit 17 to the scanning circuit 16 .

On the other hand, control (display data processing) for the anodes 2a, 2b, . . . is performed by an anode switch circuit 18 for supplying discharge voltage, and a latch circuit 19 that controls on/off the switch circuit 18 depending on display discharge or pilot discharge. , a shift register 20 that transfers the display data on the cathode to be scanned next, a data capture signal generation circuit 21 that captures the display data of this shift register 20 into the latch circuit ₁₉ , Charging signal generation circuit 2 that turns on the anode switch circuit 18
2. This is performed using the anode-connected resistor 14, the capacitor 4a, etc. The capacitor 4a has a capacitance Ca of about 20 pF, and generates a pilot discharge current together with the anode stray capacitance 12.

FIG. 8 mainly shows the specific circuit configuration of the anode switch circuit 18, and FIG. 9 shows the operation timing of each part. That is, during the period _t1 during which the cathode 7c is being scanned, the cathode 7d to be scanned next
A display data signal for is sent to the shift register 20 by a shift clock pulse, and this display data signal is sent to the data capture signal generation circuit 2.
The signal is transferred to the latch circuit 19 at the rising edge of the strobe signal from 1. And the blanking period t ₀
When the charge signal from the charge signal generation circuit 22 becomes "H" level during the operation, the output of the OR gate 23 in the anode switch circuit 18 is forced to "H" level, and all the anode switches are turned on. becomes.

On the other hand, during this period, a charging current flows into the capacitor 4a and the anode stray capacitance 12 from the +200V power supply through the output transistor of the anode switch circuit 18, and is charged to +200V.

When the charge signal goes to the "L" level, the transistor 24 of the anode switch circuit 18 turns on and off in accordance with the output level of the latch circuit 19, and the cathode 7c is scanned, and all the cathodes are scanned in the same way. By doing so, various light emission patterns are drawn by a large number of light spots.

However, according to such a drive device, when a high-definition display discharge tube with narrow strip anode spacing is used, the dielectric partition walls 8a, 8b . . . along the anodes are used.
The interval between the two becomes narrower, and charged particles and excited atoms generated by the pilot discharge from a capacitor connected to the anode become more likely to recombine and disappear at the dielectric partition wall, increasing the diffusion resistance to the adjacent intersection area. There was a problem in that the pilot flame discharge operation became unstable and flickering was likely to occur. In addition, in high-definition display discharge tubes, the capacitive coupling between the anodes is large, so the pilot flame sometimes does not light up. To explain this with reference to FIG. 7, for example, a display discharge occurs at the intersection area 2b, 7d between the anode 2b and the cathode 7d, and then the anode 2
When pilot discharge is performed in the intersection areas 2c and 7d between the cathode 7d and the cathode 7d, charged particles and excited atoms that diffuse to the intersection areas 2b, 7d, 2c, and 7e to be scanned next are transferred to the intersection area 2b. , 7e are overwhelmingly more numerous than the intersection areas 2c, 7e. Moreover, since the anode-to-anode capacitance Csa is very large, the pilot discharge that should occur in the intersection areas 2c and 7e is caused by the anode-to-anode capacitance.
There are cases where the pilot flames in the intersection areas 2c and 7e are not lit because they are drawn to the intersection areas 2b and 7e through Csa.

Problems to be Solved by the Invention In order to solve the above-mentioned problems of flickering and non-lighting of the pilot flame, it is necessary to increase the capacity of the capacitor connected to the anode and increase the amount of charge of the pilot flame discharge. good. However, increasing the capacitance of the capacitor formed in the discharge tube as described above requires a considerable area, which not only reduces the occupancy of the effective display area but also increases costs.
Also, high-definition display discharge tubes, such as cathode 400
640 anodes, dot pitch 0.3mm
For a discharge tube, the cathode on-potential period t ₁ is about 34 μS,
Blanking period t ₀ is approximately 6 μs, anode connection resistance is approximately
Since the voltage is 180KΩ, if the capacitance of the capacitor is increased, it becomes impossible to charge up to +200V within the blanking period. Also, the blanking period
Lengthening _t0 shortens the cathode on-potential period _t1 ,
This causes a decrease in the luminance of display discharge. Therefore, it may be possible to form a capacitor between the output terminal of the anode switch circuit and the anode connection resistor, but in this case, although the charging time is shortened, the configuration of the drive circuit becomes significantly complicated and costs increase. I will invite you.

Therefore, it is an object of the present invention to provide a display discharge tube drive device that can provide a stable pilot discharge without flickering, and can eliminate the problem of the pilot not lighting up due to capacitive coupling between the anodes. .

Means for Solving the Problems According to the drive device of the present invention, during the blanking period of the scanning signals that sequentially drive the cathodes, the anode is not only brought to an on-potential by the charge signal, but also by the support signal. Then, the anode potential is forcibly brought to the on-potential for a minute period within the cathode-on-potential period.

Effect With this configuration, immediately after the pilot discharge due to the anode stray capacitance (or due to the anode stray capacitance and the capacitance of the capacitor connected to the anode), an auxiliary pilot discharge with a minute width due to the support signal occurs,
More charged particles and excited atoms can be diffused into the discharge space that is then scanned, and the above-mentioned conventional problems can be solved.

Embodiment The circuit configuration according to the present invention shown in FIG. 1 differs from the conventional circuit configuration shown in FIG. The support signal taken out from the fire discharge circuit 25 and the charge signal taken out from the charge signal generation circuit 22 are given to the OR gate circuit 26, and the output signal of the OR gate circuit 26 is sent to the OR gate circuit in the anode switch circuit 18. 23 as one input signal, and the other configurations are the same as before. Note that the auxiliary pilot flame discharge circuit 25 can be composed of a delay circuit and a one-shot multivibrator.

The support signal has the relationship shown in a and b in FIG. 2 with respect to the charge signal, and periods t ₂ and t ₃ are set during the cathode on-potential period.
A signal as shown in c in FIG. 2 is taken out from the OR gate circuit 26. The transistor 24 of the anode switch circuit 18 is turned on by the charge signal during the period t0, as shown in d of FIG. ₂ , and the output of the latch circuit 19 is "L" during the period _t1 .
If it is at the level, it will be in the on state only during the period _t3 .

Therefore, now any anode has an initial period t ₁
Considering the case where a pilot discharge is performed _at A discharge takes place. Next, during period _t3 , the transistor 24 is forcibly turned on by the support signal, and as a result, a steady discharge current (f in Figure 2) flows through the anode-connected resistor 14 for a short period of time, and immediately after period _t3 , this The discharge stops.

In this way, immediately after the pilot discharge caused by the conventional anode stray capacitance and capacitor capacitance, an auxiliary pilot discharge occurs for a short time due to the support signal, and as a result, many charged particles and excited atoms are diffused into the discharge space that is scanned next. This can prevent the pilot flame from flickering or not lighting up.

By the way, the auxiliary pilot discharge in this minute time occurs on the same cathode immediately after the pilot discharge due to the anode stray capacitance and capacitor capacitance, so there is no discharge delay; After securing the period _t2 during which the pilot discharge is completed, the intensity of the auxiliary pilot discharge can be adjusted according to the "H" level period _t3 of the support signal. However, if this period _t3 is made too long, the luminous intensity ratio (contrast) between the pilot discharge and the display discharge will decrease. Furthermore, by adding a temperature correction circuit to the auxiliary pilot discharge circuit and controlling the "H" level period _t3 of the support signal to become longer as the temperature of the display discharge tube increases, the temperature of the display discharge tube will increase. It is also possible to prevent the pilot flame from flickering or not lighting up.

Effects of the Invention Since the display discharge tube drive device of the present invention is configured as described above, stable pilot discharge can always be obtained, and the fear of the pilot not lighting due to capacitive coupling between the anodes is also eliminated. be able to.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram of the main parts of a display discharge tube drive device embodying the present invention, FIG. 2 is a signal waveform diagram of each part of the device, FIG. 3 is an exploded perspective view of a display discharge tube, and FIG. Figure 4 is a cross-sectional view of a portion of the discharge tube, Figure 5 is a drive circuit diagram for explaining the operating principle of the discharge tube, Figure 6 is a signal waveform diagram at each part of the circuit,
FIG. 7 is a drive circuit diagram of the discharge tube, FIG. 8 is a diagram mainly showing the anode switch circuit of the device, and FIG. 9 is a diagram showing the operation timing of each part of the circuit. 2a, 2b... Anode, 7a, 7b... Cathode, 1
8... Anode switch circuit, 19... Latch circuit,
20...Shift register, 21...Data import signal generation circuit, 23, 26...OR gate circuit, 25...Auxiliary pilot discharge circuit.

Claims (1)

[Claims] 1. A display discharge tube comprising a band-shaped cathode group and a band-shaped anode group arranged in a protruding manner, a cathode switch circuit that sequentially brings the cathode group to an on-potential in synchronization with a horizontal synchronization signal, and the anode group. a latch circuit that sends a display data signal to the anode switch circuit in synchronization with the horizontal synchronization signal; and a latch circuit that sends a display data signal to the anode switch circuit in synchronization with the horizontal synchronization signal; a charge signal generating circuit that applies a charge signal synchronized to the anode switch circuit to charge the stray capacitance of the anode or a capacitor connected to the stray capacitance and the anode to bring the anode to an on-potential; and a cathode on-potential period. and an auxiliary pilot discharge generation circuit which applies a support signal synchronized with the horizontal synchronization signal to the anode switch circuit and forcibly brings the anode to an on-potential for a minute time. Tube drive device.