JPS6048092A - Lighting driving circuit for fluorescent display tube - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a lighting drive circuit for a fluorescent display tube used for displaying numbers, symbols, etc. in a digital needle puller or a divider. In particular, it is the 1ζth one in which the filament is shared and the tl and 7ζ multi-digit fluorescent display tubes are time-divisionally driven for each display digit in a cyclic manner.

[Background technology and its problems]

The multi-digit fluorescent display tube currently in common use has a structure as shown in Figure 1, for example, with several filaments F (directly heated cathodes) stretched in front of P1, followed by a gold plate. Control grid Gly with reticular space charge grid effect
G 2 p Gs y G< is provided: t'. The anode is made by vapor depositing metal on a substrate such as ceramics in the shape of all combinations of numbers and symbols, and coating the top with phosphor.
It consists of segments s+, S2, 53pS4.

When the filament F becomes red hot, the emitted electrons are universally accelerated in the grids G, , G2, G3, and G4. Each segment of the anode has one blade of positive voltage SIs S2 y.
It collides with S3 s S4 and emits green light, for example. Segment s of the valley display digit
, , s2 , s3 , and s are connected to the combination selection circuit 1 to display numbers, etc., and to supply a positive voltage Vs to each part of the necessary segments S1, 529SneS4. It has become. And the above is also grid G.

G2, Gs, G, and s are connected to the time division circuit 2, and each display digit is time-divided and the above-mentioned digits are cyclically connected.
A positive voltage VG is applied to G1 v G2 p 03 y G4 to perform nine display.

In the above-mentioned fluorescent display tube, conventionally, the filament (FK) is arranged so that alternating current pressure is applied to it, and in this case,
Noise is generated from the wiring, causing so-called hum in the case of commercial frequencies, and interference with AM radios etc. in the case of high frequencies.

Therefore, as shown in Fig. 1, when a DC voltage VF is applied to the filament F to turn it on, the above-mentioned interference becomes severe, but a potential gradient is generated on the filament F, and the valley of the fluorescent display tube is The display digit segment S]ls2 pss tS4 has the disadvantage that there is a difference in visual depth.

To explain this in more detail, as shown in FIG.
When a DC voltage Vr' is applied to both ends of the filament F, a potential gradient is generated and the positions 1'ttx1, X2 y on the filament F corresponding to the valley segments S1, S2, S3, and S4, respectively.
Potentials VFI, VF2, Vy at X3 +X4
3yVF4 gradually increases. These 7 pieces,
As is clear from the graph showing the relationship between the voltage between Glindorff and the luminance of the segments in Figure 3, there is a difference in visual depth between the segments Sr, S2, Ss, and S4 of each display digit. It's going to happen nine times.

[Purpose of the invention]

Therefore, the present invention has been made in view of the above-mentioned conventional problems.
ζ Mono, multi-digit fluorescent display - The above-mentioned quill 2 occurs when a DC voltage is applied to the common filament of the tube to light it up.
According to the potential gradient above, the a7rj value of the lighting time per unit time of the segment of the valley display digit is changed, and the segment of the valley display digit is changed to 'iJ+! The purpose is to manage the party and keep it cheerful.

[Summary of inventions]

In order to achieve the above-mentioned object, the lighting drive circuit for a fluorescent display tube according to the present invention has a common filament and drives a 1ζ multi-digit fluorescent display tube cyclically in a time-division manner for each valley display digit. In a lighting drive circuit for a fluorescent display tube, the time-division lighting drive is performed for each display digit according to the potential gradient on the filament that occurs in the DC voltage applied to cause a DC current to flow through the common filament. The fluorescent display tube used in the present invention is characterized by changing the total lighting time (fi) of the unit time plot and keeping the brightness of each display digit constant. Not only those that display
Of course, it also includes those displaying characters, symbols, etc.

〔Example〕

Hereinafter, one embodiment of the lighting drive circuit for a fluorescent display tube according to the present invention will be described in detail with reference to the drawings.

For example, as shown in FIG. 4, a fluorescent display tube lighting drive circuit 10 according to the present invention includes a DC power supply 11, a combination selection circuit 12, and a time division/lighting time control circuit 13. . A DC power supply 11 is connected to the filament F and applies a voltage, and also supplies voltage to the combination selection circuit 12 and the time division/lighting time control circuit 73, respectively. The silk matching selection circuit 12 selects segments of each display digit) S, ,
S2.

S8. , S4 is connected to each segment S according to the mathematics, letters, etc. that indicate the voltage supplied from the DC power supply 11 above.
1 t 82 y 85 y s4.

Ma/ko, time division/stippling time flr! The disease 1 circuit 13 is connected to each grid G, . . . , G 2 , G , . The grid consists of a pulse width modulator for controlling the pulse width, a multiplexer for selectively supplying the pulses to each grid, and the like.

The relationship between the 1-pulse width and the amount of light per unit time of a segment is determined by J when the voltage between the grid filaments is constant.
In this case, as shown in FIG.
The relationship between the voltage between the filaments and the brightness of the segment is still approximately proportional in the straight line part (segment lighting drive area) in Figure 3.In other words, in order to keep each segment visually the same ψJ K should be set so that the relationship between the voltage between the grinding filaments and the pulse width is approximately inversely proportional.Therefore, as shown in Figure 6, for each grinding filament,
CD'5FfEId, Va = Vp1>VC-VF
2> V G-V p 3> V c -V F 4
Therefore, in accordance with this, the time division/lighting time control circuit i1 13 sets the respective pulse widths τ, ~
``For τ4, τ1〈τ2 τ,〈signalize the magnitude relationship of τ4 [], 5-divided pulses are applied to each grid G, , G2 ,
If supplied to G3 and G4, the segment of each display digit) Sz
, S2 , S, ++ S4' (T-can maintain the same brightness visually.

That is, as the voltage between the grid and the filament decreases, the total pulse width of the time-division pulse increases, and the product of the voltage between the grid and the filament and the pulse width becomes approximately the same. It's okay if you do it like that.

The time chart in Figure 7 is "2. Each segment S+
, S2 , S'3 -8. + corresponding to the lighting drive timing of each grid G1. G2, Gs, G,
The relationship between the pulse width of the time-division pulse added to + and the pulse width of the time-division pulse
Each time t1, t2 for each segment]
, t3 and t4, respectively, each segment S
1, S2, Ss, and S4 start lighting, and are driven for a period of time τ1, τ2, τ3, and τ4, respectively, and each segment is cyclically driven at a repetition period Tn (-4Ts). The lighting is driven II. therefore,
Each cell was kept at the same visual brightness.

In addition, the change in the pulse width that changes depending on the voltage between the two grids and filaments can be programmed in the time division/lighting time control circuit 13 in advance.

Note that in the above embodiment, each grid G, , G2.

The pulse width of the divided pulses applied to G, , G, , was varied, but the pulse width of the time-divided pulses was constant as shown in Figures 8 and 9, and the pulse per unit time was It is also possible to vary the number.

In case J of Fig. 8, each segment S1'yS2, ss
Corresponding to tS4, the number of pulses in each time division switching period Ts is increased by 1, for example, 1, 2, 3, and 4, and each segment is repeated at a period TR (= 4T s
), it is possible to keep each of the above segments at the same visual brightness by driving them to turn on in a cyclical manner. In this case, the number of pulses generated in the time division switching period Ts4JJ: increases sequentially from 1 to 4, and this repeats with the period T'R (= 4 Ts). This can be realized by a multiplexer or the like that selectively supplies the pulses to each grid GI p G2, G3, G, respectively.

9. In other words, the above time division switching period Ts
A pulse generator that can generate one pulse per pulse is used. In this case, the pulses generated by the pulse generator are applied to each grid G 1v G 2 , G , + t G, corresponding to the valley segment.
+ is selectively supplied using a multiplexer, etc., and the repetition period T is set for grid G1.
The remaining 3 pulses excluding the first one per 4TR, which is 4 times R, are thinned out, and the remaining 3 pulses are thinned out in the same way as grid G.
It is a good idea to thin out all the crucibles (the last two times for grid G3, and the last one for grid G3).

That is, each grid Gt, G2 between the above 4 T R
The number of pulses supplied to , G3, and G4 is 1, respectively.
This means that the number of segments increases by 1, 2, 3, and 4, and the hole allows each segment to be visually maintained at the same brightness.

In the embodiments shown in FIGS. 8 and 9, each segment (7) Sl-32FS3FS4 is used to simplify the explanation.
An example in which the number of pulses supplied to Of course, it is sufficient to set the relationship so that the relationship is inversely proportional.

In the above embodiment, a time-division pulse is supplied to each grid to keep each segment visually the same brightness, but the same effect can be obtained by supplying the above-mentioned time-division pulse to each segment. Get nine.

〔Effect of the invention〕

As is clear from the description of the embodiments described above, according to the present invention, a DC voltage is applied to a common filament of a multi-digit fluorescent display tube, and each grid voltage is adjusted according to the potential gradient on the filament that occurs in this case. The pulse width 11 of the 9 time-division pulses applied to the 7 valley segments is equal to the number of pulses (i.e.
By changing the sum of the lighting times of the unit time of each segment, the valley segments can be kept visually at the same brightness, and the intended purpose can be fully achieved.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the structure of a currently commonly used multi-digit fluorescent display tube and the configuration for driving the same, and FIG. 2 is a schematic diagram showing the structure of the multi-digit fluorescent display tube. FIG. 3 is a graph showing the relationship between the voltage between the two points and the brightness of the segment. FIG. 4 is a gross diagram showing the configuration of one embodiment of the lighting and driving circuit for a fluorescent display tube according to the present invention, and FIG. 5 shows the voltage applied to each grid when the voltage between the grid and the filament is constant. Figure 6 is a graph showing the relationship between the pulse width of the time-division pulse and the light amount per unit time of the segment. Figure 7 shows the lighting drive timing of each segnon I and the pulse width β of the time-division pulse added to the valley grid corresponding to segnon I. Figures 8 and 9 show eight different embodiments of the present invention.The pulse width of the time-division pulse is constant, and the unit time is This is a time chart when the number of pulses is changed. 0 10... Lighting of fluorescent display tube, drive circuit 11... DC power supply 12... Combination selection circuit 13... Time division/lighting Time control circuit 4”J Applicant: Sony Corporation Representative Patent attorney: Mitsumi Koike 1) Sakae Mura - Figure 1, 1K Figure 2 F Filament Kono I Eki □ Figure 3 Kussodo Ramen L @ 2 loaves

Claims (1)

[Claims] In the lighting 1 drive circuit for a fluorescent display tube, in which the filament is made common fL7, the multi-digit fluorescent display tube is time-divided and cyclically driven to light up for each display digit, in order to flow a direct current through the common filament. Depending on the potential gradient on the filament caused by the applied DC voltage, the total value of the lighting time per unit time of each display digit driven by the time-division lighting drive is changed, and the brightness of each display digit is changed. It is characterized by keeping the temperature constant. Lighting drive circuit for fluorescent display tube.