JPH05323900A - Fluorescent display device - Google Patents

Abstract

PURPOSE:To eliminate the irregularity, flicker, and fluctuations of a display on the fluorescent display device. CONSTITUTION:This fluorescent display device consists of a fluorescent display tube 1, an anode driver 2 and a grid driver 3 which supply display voltages to this fluorescent display tube 1, a control circuit 4 which supplies control signals to the anode driver 2 and grid driver 3, an interface circuit 5 which sends and receives signals to and from the outside, a DC-DC converter 8 which boosts a low voltage to a desired voltage, a filament voltage supply circuit 7 which supplies a voltage to a filament, and a synchronizing circuit 6 which synchronizes the voltage supplied to the filament with a period for displaying one screen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent display device,
In particular, the present invention relates to a dynamic drive XY dot matrix fluorescent display device that drives an XY dot matrix fluorescent display tube in a time division manner.

[0002]

2. Description of the Related Art In a conventional fluorescent display device, as shown in FIG. 6, a DC-DC / AC converter 21 of a self-excited type is used, and a low input voltage 15 of about +5 to +12 V is applied to the input voltage 15 of 50 to 50.
The voltage is converted into an AC voltage of about 100 KHz and supplied to the filaments 1F to 1F of the fluorescent display tube 1. Therefore, as shown in FIG. 7, the supply voltage to the filament becomes like a solid line at a certain time AT, and becomes like a dotted line at a certain time BT, and the supply voltage cycle to the filament is the display cycle of one screen and in each grid. It is not synchronized with the scan signal at all. Also, as shown in FIG.
The amplitude of the filament supply voltage from G and (n + 1) G is large, and when focusing on 2G, the filament supply voltage is high as shown by the solid line at a certain time AT, and the filament supply voltage is low as shown by the dotted line at a certain time BT. There is.

[0003]

In this conventional fluorescent display device, a self-exciting DC-DC / AC converter is used to
Since the C voltage is supplied to the filament, the voltage supplied to the filament is not synchronized at all with the period for displaying one screen and the period for displaying one digit. Therefore, focusing on a certain digit, the voltage supplied to the filament is high when the screen is one screen and low when the screen is one screen. However, there was a problem that the difference in luminance between digits was about 20 to 30%, and unevenness and flickering occurred in the display.

This occurs as the display time of one digit is shorter, and the display voltage fluctuates because the cycle of the voltage supplied to the filament is asynchronous with the display cycle of one screen and the luminance difference between the digits is 20 to 30%. There was a problem.

[0005]

SUMMARY OF THE INVENTION A fluorescent display device of the present invention includes an envelope whose inside is maintained in a high vacuum atmosphere, and a plurality of filaments provided inside the envelope for emitting thermoelectrons. A plurality of linear grid electrodes which are provided in the envelope for controlling the deflection and acceleration of the thermoelectrons from the filament and which adjoin two adjacent grids in a time-sharing selective control; XY dot matrix fluorescent light having a phosphor layer that emits light by collision of thermoelectrons from a filament provided on the inner surface of the envelope, and composed of a plurality of anode electrodes provided in a direction intersecting the linear grid electrode. Display tube,
An anode driver and a grid driver for supplying a display voltage to the fluorescent display tube, a control circuit for supplying a control signal to the anode driver and the grid driver and an interface circuit for exchanging signals with the outside, and a low voltage A DC-DC converter that boosts the voltage to a desired voltage and supplies it to the anode driver and the grid driver, a filament voltage supply circuit that supplies voltage to the filament, and a cycle of the voltage supplied to the filament and a cycle of displaying one screen are synchronized. And a synchronization circuit for controlling the synchronization.

[0006]

The present invention will be described below with reference to the drawings. 1 is a block diagram of an n.times.m dot matrix fluorescent display device according to a first embodiment of the present invention, and FIG. 2 shows a specific example of the filament voltage supply circuit 7 of FIG. The fluorescent display tube 1 includes anode electrodes 1A to mA, grid electrodes 1G to (n + 1) G, and filaments 1F to 1F.
F is enclosed in an envelope to create a vacuum inside.

The input signal 9 is supplied to the control circuit 4 through the interface circuit 5. In the control circuit 4, the input control signal 10 is a scan data signal necessary for display, a scan clock, a grid control signal 12 of a blanking signal and a display data signal, a data shift clock, a data latch signal, and a blanking signal. And the like are converted into anode control signals 11 and supplied to the grid driver 3 and the anode driver 2, respectively, and the display voltage is supplied from the grid driver 3 and the anode driver 2 to the fluorescent display tube 1.

Further, an input voltage 15 of about +5 to + 12V
Is supplied to the filament voltage supply circuit 7 and the DC-DC converter 8 and converted into an AC voltage and a high voltage of about +50 to + 150V. At this time, the synchronization signal 14 is also supplied from the control circuit 4 through the synchronization circuit 6 to the filament voltage supply circuit 7.

The DC-DC converter 8 supplies a voltage to the grid driver 3 and the anode driver 2, and the filament voltage supply circuit 7 supplies an AC voltage to the filament of the fluorescent display tube. Further, as shown in FIG. 2, the input voltage 15 of about +5 to +12 V supplied to the transformer 18 of the filament voltage supply circuit 7 is the synchronization signal 14
Is switched by the switching transistor 19 and is cut by the kV cutoff Zener diode 20.
With the center tap 17 having a kV voltage increased from V as a reference, the filament tap voltage 16 is converted to an AC voltage of jVp-p.

At this time, as shown in the timing chart of FIG. 3, the 1/2 cycle of the synchronizing signal is equal to the display cycle of one screen, and is usually about 10 mS and sequentially from 1 G during the display cycle of this one screen ( Scan up to n + 1) G. The sync signal is sequentially repeated at "H" at nT and at "L" at the next (n + 1) T. The filament potential on each grid at nT changes linearly from (k + j / 2) V in 1G to (k-j / 2) V in (n + 1) G as shown in FIG. 4 because the filament is a resistor. ,
At the time of (n + 1) T, on the contrary, 1G linearly changes from (k−j / 2) V to (k + j / 2) V of (n + 1) G,
Repeat this one after another.

Therefore, since the display cycle of one screen and the cycle of the filament supply voltage are synchronized with each other, the filament supply voltage is never low or high depending on the digit.
It is possible to obtain a good display without any problems such as display flickering, unevenness, and inter-digit luminance difference, which are caused by fluctuations in the display caused by the filament supply voltage and the display period of one screen being asynchronous. Further, even if the one-digit display period becomes short, a good display can be obtained without being affected by the display.

FIG. 5 shows a filament voltage supply circuit for explaining the second embodiment of the present invention. Filament 1F in the middle arranged switching elements S ₁ to S ₄ in H-type
~ 1F are connected, an input voltage 22 of (k + j / 2) V is connected to the switching elements of S ₁ and S ₃ , and (k-j /
2) The V Zener diode 23 is connected to the switching elements of S ₂ and S ₄ . The resistance R is (k-j / 2) V
This is for allowing an idle current to flow through the Zener diode 23. Further, the synchronization signal 14 is the switching element S ₁
~ Control S ₄ .

According to this filament voltage supply circuit,
The sync signal 14 causes S ₁ and S _{4 at} nT as shown by the solid line.
Turns on, S ₃ and S ₂ turn off, and a filament current flows from LF to RF. At (n + 1) T, S ₃ and S ₂ turn on and S ₁ and S ₄ turn off, as indicated by the dotted line. , RF causes a filament current to flow in LF, and a waveform similar to that in FIG. 4 is obtained.

Therefore, there are no problems such as display flicker, unevenness, and fluctuations, good display can be obtained, and since no transformer is used, the number of parts can be reduced and the circuit configuration can be simplified, resulting in cost reduction. There is an advantage that it becomes advantageous.

[0015]

As described above, according to the present invention, since the period for supplying the supply voltage to the filament and the display period for one screen are synchronized, the display unevenness with the inter-digit luminance difference of 20 to 30% is eliminated. This has the effect of providing a good display without flickering or fluctuation of the display due to asynchronization.

[Brief description of drawings]

FIG. 1 is a block diagram of an n × m dot matrix fluorescent display device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a filament voltage supply circuit of the n × m dot matrix fluorescent display device shown in FIG.

FIG. 3 is a timing chart diagram for explaining the present embodiment.

FIG. 4 is a diagram showing a filament potential of each grid according to the present embodiment.

FIG. 5 is a diagram showing a filament voltage supply circuit according to a second embodiment of the present invention.

FIG. 6 is a block diagram of a conventional n × m dot matrix fluorescent display device.

FIG. 7 is a timing chart of a conventional n × m dot matrix fluorescent display device.

FIG. 8 is a diagram showing a filament potential of each grid of a conventional fluorescent display device.

[Explanation of symbols]

 1 Fluorescent Display Tube 2 Anode Driver 3 Grid Driver 4 Control Circuit 5 Interface Circuit 6 Synchronous Circuit 7 Filament Voltage Supply Circuit 8 DC-DC Converter 17 Center Tap 18 Transformer 19 Switching Transistor 20, 23 Zener Diode 21 Self-excited DC-DC / AC Converter 1A to mA Anode electrode 1G to (n + 1) G Grid electrode 1F to IF Filament

Claims (1)

[Claims] 1. An X-Y dot matrix fluorescent display tube,
An anode driver and a grid driver for supplying a display voltage to the fluorescent display tube, and a control circuit for supplying a control signal to the anode driver and the grid driver,
Interface circuit for exchanging signals with the outside, and DC-DC for boosting a low voltage to a desired voltage and supplying the boosted voltage to the anode driver and the grid driver
A converter, a filament voltage supply circuit for supplying a voltage to the filament of the fluorescent display tube, and a synchronizing circuit for synchronizing the cycle of the filament supply voltage and the display cycle of one screen. Fluorescent display device.