JPS60184294A - Filament driving circuit for fluorescent indicator 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] [Technical Field of the Invention] The present invention provides a filament drive circuit 1 in which i≦optical display
4. S, plural A is light display ゜4
This makes it suitable for driving.

[Prior Art] As shown in FIG. 1, the conventional filament drive circuit for a fluorescent display tube uses an AC power supply, and connects a Zener diode ZD and a capacitor C between the midpoint M of the AC power supply and the bias reference potential. They are connected by a cage circuit.

A fluorescent display tube (4) consists of a filament (1), in which electrons emitted from the filament (1) are accelerated by a grid (2), collide with an anode (3), and the IX light material is coated on the surface of this anode (3). is excited and emits light. However, this
≦The brightness of the light display tube (4) is the same as that of the filament (1)
(3) between 17) Ttjt IE Ebc ni depend (
a53 fig.jj1. +), so especially in the case of multi-digit 7 and (5) as shown in Figure 2, the potential gradient between the filament (1) and the anode (3) caused by the voltage drop across the filament (1) and the anode (3) is displayed as a brightness gradient. Use a power supply on AC 1 to prevent it from appearing. In addition, in order to prevent the anode (3) that does not need to be lit to emit light, the anode potential when not lit, that is, the bias reference potential, must be biased to be lower than the filament voltage 4Q. pressure,
That is, the cutoff voltage Ek is set by the voltage Vz generated by the Zener diode ZD and the capacitor C (see FIG. 3).

However, since the grid current ic and anode current ib of the fluorescent display tube all pass through the Zener diode ZD, as shown in FIG. 4, when using multiple fluorescent display tubes simultaneously in the conventional circuit, , the large size of the Zener diode ZD is 1iz= iJ +ib2 +・=
+ ibn + ice + ic2 +-+ icn
There are disadvantages such as 'JA' and the need for a large capacity and expensive Zener diode.

[Summary of the Invention] The present invention has been made to eliminate the drawbacks of the conventional art.1. +
：H', Our goal is to realize a filament drive circuit that can withstand a large capacity current without using a high-value Zener diode and can set a stable switch-off voltage. There is.

[Embodiment of the Invention] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 5 shows an embodiment of the present invention using an NPN transistor.
NPN) The collector and emitter of the transistor Tr are connected to the midpoint M of the filament AC power supply and the bias reference potential, and a Hezener diode ZD is connected between the collector and base, and the transistor Tr
A capacitor C is connected between the collector and emitter of the fluorescent display tube (1) connected in parallel with the filament (1).
4) constitutes the filament drive circuit.

If the filament drive circuit is implemented as shown, the cutoff voltage Ek of the fluorescent display tube (4) will be Ek='V2+
V be. Here, v'2 is the Zener voltage, Vbe is the voltage between the base and emitter of the transistor, and is 0.6
It is about ~0.7■. On the other hand, the entire anode electrolyte of the fluorescent display tube (4) and the grid electrode 11t i -1bl +ib2
+...+ibn +icl +ic2 +-+1an flows through the transistor Tr, and the current flowing through the Zener diodes Z and D can be ignored.

Therefore, by using such a combination of Zener diode ZD and transistor Tr, a circuit equivalent to an expensive large capacity Zener diode can be realized using an inexpensive small capacity diode and a power transistor.

Note that in the embodiment 1, NP is used as the transistor Tr.
Although N transistors are used, PNP transistors can be used as well.

[Effects of the Invention] As described in 1- below, according to the present invention, the cutoff voltage of a fluorescent display tube can be set stably at low cost by combining a Zener diode, a transistor, and a capacitor.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing the filament drive circuit of a conventional fluorescent display tube, Figure 2 is an example diagram of a multi-digit fluorescent display, and Figure 3 explains the relationship between the drive voltage and filament level of an extinction display tube. FIG. 4 is a waveform chart, FIG. 4 is a fluorescent table, ]<A conventional filament drive circuit diagram when several bonds are used, and FIG. 5 is a circuit diagram showing a filament drive circuit according to the present invention. (1)...Filament, (2)...Grid, (
3)... Anode, (4)... Fluorescent display tube, ZD...
・Zener diode, C... capacitor, Tr...
・Transistor, M...Middle point of filament. Agent Masu Oiwa h1 Figure 1 Figure 2 Figure 3 Figure 4

Claims (2)

[Claims] (1) The midpoint of the filament tunryu of the 7i9 light table 71\f6・ and the bias no+('(!i ?li, j:l:
In between, a capacitor connected in parallel between the transistor and the collector, emitter, and collector of this transistor is provided, and a Zener diode is provided between the collector and the collector of the transistor. Oru.'i
Filament I/11 moving circuit of optical display tube. (2) JU number c′1≦・Cutoff 1 for light display accommodation;
1lili enclosure Qi 1 /+ description of the patent claim characterized in that it has a 4111 configuration for setting the pressure, and the optical analysis display?
Old filament driven J+ijJ road.