JP2002215079A - Digital display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive digital display device which can perform lighting at a stroke with constitution in which a general purpose IC for fluorescent display tube is used. SOLUTION: This display device is a digital display device which is provided with a fluorescent display tube 6 and in which the fluorescent tube 6 is driven by an IC which is provided with an accessory terminal to be connected to an accessory switch interrupting a current flowing through the filament electrode 6a of the tube 6 and blanking terminals controlling output signals of the grid electrodes and the anode electrodes of the tube 6 and, moreover, a delay circuit for delaying a time when currents are inputted to the blanking terminals than a time when a current is inputted to the accessory terminal is provided in the display device. Then, when a current is made to flow through the filament electrode and the electrode reaches a prescribed temperature, currents are made to flow through the grid electrodes and the anode electrodes of the tube 6 and the tube 6 is lighted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fluorescent display (Va).
cum Fluorescent Display:
VFD), an IC having an accessory terminal connected to an accessory switch for interrupting the current flowing through the filament electrode of the fluorescent display tube, and a blanking input terminal for controlling output signals of the grid electrode and the anode electrode.
And a digital display device in which a fluorescent display tube is driven.

[0002]

2. Description of the Related Art An in-vehicle digital display clock which is a specific example of a conventional digital display device will be described with reference to a circuit diagram of FIG.

A power supply terminal BAT and a first diode D
1. The first resistor R1 is connected in series, and the output side of the first resistor R1 is branched into three. The first branch is grounded to ground G via a first zener diode Z1 for stabilizing a constant voltage and a current, and the second branch is a first capacitor C1 for stabilizing a constant voltage and a current. Through the ground G. The third branch is connected to the power input terminal VCC of the clock IC 2.

The first resistor R1 is for controlling current, and the first Zener diode Z1 is for maintaining a constant voltage. The first capacitor C1 is for stabilizing the current, and constitutes a constant voltage circuit of the power supply BAT.

A known crystal oscillator 4 and a fluorescent display tube (VFD) 6 are connected to the timepiece IC 2.

The watch IC 2 includes a second capacitor C2 for removing noise from external radio waves, and a watch IC.
A third capacitor C3 for resetting the internal counter 2 is provided, and a switch M, a switch H, and a switch S for operating time are provided.

Further, a blanking input terminal BLANK of the watch IC 2 is connected to an accessory terminal AC via a second diode D2 and a second resistor R2 connected in series.
It is connected to C. The accessory terminal ACC is linked to an accessory switch of the automobile, and the output side of the second diode D2 branches into two.

One output side of the second diode D2 is connected to a clock IC 2 via a constant voltage circuit to a blanking input terminal BLANK, which will be described later, and the other is connected to a clock IC2.
It is connected to the fourth resistor R4.

The output side of the second resistor R2 is branched into two, one is connected to the blanking input terminal BLANK of the clock IC 2, and the other is grounded via the second Zener diode Z2. G is grounded. Second
Zener diode Z2 and second resistor R2 constitute a constant voltage circuit to the blanking input terminal.

The other output side of the second diode D2 is connected to a fourth resistor R4, a fifth resistor R5 and a sixth resistor R5.
Sixth, a seventh resistor R7 is connected in series, and the output side of the seventh resistor R7 is branched into two.

On the other hand, one output side of the seventh resistor R7 is grounded to the ground G via a third diode D3, and the other is connected to the filament electrode 6a of the fluorescent display tube 6. The filament electrode 6a is grounded to the ground G.

The fourth resistor R4 and the fifth resistor R
5, a sixth resistor R6 and a seventh resistor R7 constitute a current controlling resistor of the filament electrode, and a third diode D
Reference numeral 3 denotes a constant voltage diode for the filament electrode.

The write input terminal 20 of the clock IC 2
And a light terminal ILL connected to a light switch for turning on the light of the vehicle, between the third resistor R
3 are connected in series, and the third resistor R3 and the third Zener diode Z3 grounded to the ground G constitute a constant voltage circuit to the write input terminal of the watch IC 2.

In the above-mentioned conventional digital display timepiece for a vehicle, when the accessory switch is turned on, the fluorescent display tube 6 is turned on.
A current flows through the filament electrode 6a, and the grid electrode 6b and the anode electrode 6c of the fluorescent display tube 6 are turned on.

However, in the conventional digital display timepiece for a vehicle, the grid electrode 6b and the anode electrode 6c of the fluorescent display tube 2 are turned on before the entire filament electrode 6a is warmed up. The anode electrode was turned on gradually from the heated part.

[0016]

Therefore, as a means for avoiding this, an in-vehicle digital display clock using a microcomputer (hereinafter referred to as "microcomputer") has been devised. That is, the filament electrode 6 of the fluorescent display tube 6
a, and after a certain time, the fluorescent display tube 6
A program instruction such as turning on the grid electrode 6b and the anode electrode 6c is issued, so that a digital display clock for a vehicle in which the fluorescent display tube 6 is turned on at once, not gradually, has been proposed.

However, when a microcomputer is used, a driver IC for a fluorescent display tube or the like is required, so that an in-vehicle digital display clock becomes expensive.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an inexpensive digital display device in which a fluorescent display tube can be turned on at a stroke by using a clock IC for a general-purpose fluorescent display tube. Things.

[0019]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and the invention described in the first aspect of the present invention includes a fluorescent display tube, and the fluorescent display tube has a filament electrode. An IC having an accessory terminal connected to an accessory switch for interrupting a flowing current; and a blanking input terminal for controlling output signals of a grid electrode and an anode electrode of the fluorescent display tube. In a digital display device in which a tube is driven, a delay circuit for delaying a time for inputting a current from the accessory terminal to the blanking input terminal is provided, and a current flows through the filament electrode, and when a predetermined temperature is reached, the fluorescent light is emitted. A current flows through the grid electrode and the anode electrode of the display tube, and the digital display device in which the fluorescent display tube is turned on. That.

With this configuration, the fluorescent display tube can be turned on at once.

According to a second aspect of the present invention, in the delay circuit, the accessory terminal has a first transistor connected to an emitter and a second transistor connected to a collector at a base of the first transistor. And a base of the second transistor, a first resistor connected to the input side, a second resistor connected in series to the input side of the first resistor, and a second resistor connected in series to the input side of the first resistor. On the input side of the resistor, a Zener diode is connected in series, and the filament electrode is connected in series with the Zener diode. The collector of the first transistor is connected to the blanking input terminal. Digital display device.

More specifically, it is preferable to configure as in the second aspect of the present invention.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION The gist of the present invention is a digital display device that turns on the grid electrode and the anode electrode of a fluorescent display tube after the electrons emitted from the filament electrode are stabilized, that is, the electrons are stabilized. The main point is to provide a digital display device that is turned on at a stretch by detecting a voltage value of the emitted filament electrode and then inputting a signal to a blanking input terminal of the IC.

An embodiment of the present invention will be described below with reference to the drawings. The same members as those of the conventional example are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 1 is a circuit diagram showing a circuit configuration of an on-vehicle digital display timepiece according to an embodiment of the present invention.
In the drawings, abbreviations such as a filament for a filament electrode, a grid for a grid electrode, and an anode for an anode electrode are used.

The timepiece IC 2 of the digital display timepiece according to the present invention also has a first resistor R1 and a first zener diode Z for stabilizing a constant voltage and current, as in the prior art.
1. A power supply BA composed of a first capacitor C1
A constant voltage circuit of T is provided.

The clock IC 2 of the on-vehicle digital display timepiece according to the present invention also has a crystal oscillator 4 and a fluorescent display tube 6.
And are connected.

Further, the clock IC 2 of the digital display device according to the present invention has a second IC for removing radio noise.
, A capacitor C3 for resetting an internal counter of the clock IC 2, and a switch M, a switch H, and a switch S for operating time.

The write input terminal 20 of the clock IC 2
And a light terminal ILL connected to a light switch for turning on a light of the automobile, a third resistor R3 is connected in series. The third resistor R3
And the third Zener diode Z3 grounded to the ground G constitute a constant voltage circuit to the IC input.

An accessory terminal ACC connected to a blanking input terminal BLANK of the watch IC 2 via a delay circuit is connected to an accessory switch of the automobile.

A second diode D2 is connected in series to the accessory terminal ACC.
The two output sides are branched into two. One is a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, and a seventh resistor R7.
Are connected in series, and the other is connected through a constant voltage circuit to a blanking input terminal BLANK described later,
2 blanking input terminal BLANK.

Note that the fourth resistor R4 and the fifth resistor R
Fifth, sixth resistor R6 and seventh resistor R7 constitute a filament electrode current control resistor.

The output side of the seventh resistor R7 is branched into three, and the first branch is via a Zener diode Z4, an eighth resistor R8, and a ninth resistor R9 connected in series.
It is grounded to the ground G. The second branch is grounded to the ground G via the third diode D3,
Are grounded to the ground G via the filament electrode 6a.

The third diode D3 is a constant voltage diode for the filament electrode voltage.

The base of the first transistor TR1 is connected between the output side of the eighth resistor R8 and the input side of the ninth resistor R9, and the emitter of the first transistor TR1 is connected to the ground G. Grounded.

The collector of the first transistor TR1 is connected to the base of the second transistor TR2 via a resistor R10, and the collector of the second transistor TR2 is branched into two. One branch is grounded to the ground G via an eleventh resistor R11, and the other branch is a blanking input terminal BLANK of the clock IC2.
It is connected to the.

A twelfth resistor R12 is connected between the emitter and the base of the second transistor TR2,
The emitter of the second transistor TR2 is connected to the accessory terminal ACC via a constant voltage circuit to the blanking input terminal BLANK.

The constant voltage circuit to the blanking input terminal BLANK is the same as in the conventional example.

Next, the clock IC 2 will be described.

The clock IC 2 is a general-purpose fluorescent display tube IC.
And is rectangular.

A VCC input terminal and a VD
A D input terminal, a VSS input terminal, an A / C input terminal, and a blanking input terminal BLANK are provided in this order.
Grid electrode 6b and anode electrode 6 of fluorescent display tube 6
c is provided.

A quartz oscillator 4 is provided on the short side on the VCC terminal side. By changing the fifth capacitor CA, the fifth capacitor CB, and the sixth capacitor CX, the reference frequency of the crystal oscillator 4 is changed. It is configured to adjust.

Next, the fluorescent display tube (VFD) 6 will be described.

The fluorescent display tube 6 is constituted by a vacuum container, and a filament electrode 6 is provided in the container as a basic electrode.
a, a grid electrode 6b, and an anode electrode 6c.

On the grid electrode 6b side of the fluorescent display tube 6,
A filament electrode 6a is provided, where electrons are generated. Then, the electrons jumping out of the filament electrode 6a are controlled by the grid electrode 6b, and emit light by hitting the phosphor provided on the anode electrode 6c.

Next, the operation of the above embodiment will be described.

When the accessory terminal ACC is turned on, as the current flows through the filament of the fluorescent display tube and the filament electrode 6a is heated, the resistance of the filament electrode 6a gradually increases. Then, the voltage at the point “a” becomes
It changes as shown in FIG.

That is, when the voltage value at the point "a" becomes constant, it indicates that the filament electrode 6a has been completely heated.

When this constant voltage is detected by the fourth zener diode Z4, a zener current IZ flows, the base voltage "b" of the first transistor Tr1 increases, and the first transistor Tr1 turns on. . Then
When the voltage of the “C” portion becomes lower than the base voltage of the second transistor Tr2, the second transistor T2
r2 is turned on, and a voltage is generated at the “d” portion.

If 0 volt is [L] and a voltage exceeding 0 volt is [H], "H" is input to the blanking input terminal BLANK of the watch IC 2 and the watch IC 2
2, a voltage is output from the grid electrode 6b and the anode electrode 6c. As a result, the fluorescent display tube 6 is turned on at once rather than gradually from below the anode electrode 6c.

The blanking input terminal BLANK is a terminal for controlling output signals of the anode electrode 6c and the grid electrode 6b output from the clock IC.

Next, voltages at respective points (points a, b, c, and d) in the circuit diagram of the digital display clock for vehicle use will be described.

FIG. 2 shows the voltage at the accessory terminal (ACC), the voltage at point a (a), the voltage at point b (b), the voltage at point c (Tr1c), the voltage at point d (Tr2d), Ranking input terminal BLANK
5 is a time chart showing time-series changes of the current (IC / BLANK), the voltage (anode) at the anode electrode 6c of the fluorescent display tube, the voltage (grid) at the grid electrode 6b of the fluorescent display tube, and the like. The horizontal direction indicates time, and increases to the right. The vertical direction indicates a change in voltage and current, and increases in the upward direction.

The present invention utilizes the characteristics of the filament electrode (FIG. 2A), and the digital display device of this embodiment has a fluorescent display in about 0.7 seconds after a voltage is applied to the accessory terminal ACC. The tube 6 lights up at once. However, this time can be arbitrarily set according to the characteristics of the filament electrode.

As described above, according to the present invention, when a voltage is applied to the accessory switch by the ignition key of the automobile, the fluorescent display tube is turned on at a moment, and at the same time as the fluorescent display tube is turned on. You can know the time.

To achieve the same effect as the present invention, a configuration using a delay timer using a reference signal is conceivable. However, this delay timer must use a clock, and a digital display using the present invention is used. It is clear that the device is cost-effective.

Although the present embodiment has been described with reference to a vehicle-mounted digital display clock as a specific example, the present invention is not limited to this. Thus, when the power is turned on, the fluorescent display tube is turned on at once for a moment, and the time and other information can be known.

[0058]

As described above, according to the present invention, since a delay circuit for delaying a time for inputting a current is provided from the accessory terminal to the blanking input terminal, the present invention is applicable to a general-purpose fluorescent display tube. With a configuration using an IC, an inexpensive digital display device that can be turned on at a stretch and can be provided.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a circuit configuration of an in-vehicle digital display timepiece according to a specific example of the present invention.

FIG. 2 is a time chart of a voltage according to a specific example of the present invention.

FIG. 3 is a circuit diagram showing a circuit configuration of a conventional in-vehicle digital display timepiece according to a specific example of the present invention.

[Explanation of symbols]

 2 Clock IC 6 Fluorescent display tube 6a Filament electrode 6b Grid electrode 6c Anode electrode TR1 First transistor TR2 Second transistor R1 to R12 First to twelfth resistor Z1 to Z4 First to fourth Zener diode BLANK Ranking input terminal ACC accessory-terminal

Claims (2)

[Claims] An accessory terminal connected to an accessory switch for interrupting a current flowing through a filament electrode of the fluorescent display tube; and a block for controlling output signals of a grid electrode and an anode electrode of the fluorescent display tube. A digital display device having an IC having a ranking input terminal, wherein the IC drives the fluorescent display tube. In the digital display device, a delay circuit for delaying a time when a current is input from the accessory terminal to the blanking input terminal. Is provided, a current flows through the filament electrode,
When a predetermined temperature is reached, a current flows through the grid electrode and the anode electrode of the fluorescent display tube, and the fluorescent display tube is turned on. 2. The delay circuit, wherein the accessory terminal has a first transistor connected to an emitter, and
Of the second transistor connected to the collector
And the base of the second transistor is
A first resistor connected to the input side, a second resistor connected in series to the input side of the first resistor, and a Zener diode connected in series to the input side of the second resistor 2. The digital display according to claim 1, wherein the first electrode is connected to the blanking input terminal, and the filament electrode is connected in series with the Zener diode. apparatus.