JPH07261694A - Fluorescent display tube driving circuit - Google Patents

Abstract

PURPOSE:To provide a fluorescent display tube driving circuit with simple circuit constitution and preventing a chip size from becoming large even when the circuit is made into an IC. CONSTITUTION:This fluorescent display tube driving circuit is constituted of a display data supply circuit serial-transfer supplying the display data, a first shift register 5 inputting the serial transferred display data, a latch register 6 latching the output of the first shift register 5 and imparting it to the segment of the fluorescent display tube, a latch pulse generation circuit 7 generating the latching pulse for the latch register 6 and a second shift register 8 receiving the output pulse of the latch pulse generation circuit 7 and successively shifting and outputting a voltage applied to the grid of the fluorescent display tube.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorescent display tube driving circuit.

[0002]

2. Description of the Related Art For example, in a VTR, a fluorescent display tube (FL tube) is used as a means for displaying information such as its operating state. On the other hand, as a driving method of the fluorescent display tube, a method of dynamically driving a plurality of display portions (display characters) is used. FIG. 5 shows such a conventional example.
In the figure, reference numeral 50 is a serial interface for receiving display data from a microcomputer, and its output is temporarily stored in a display memory 51 composed of a RAM.

Then, the latch circuit 5 is read based on the timing signal from the timing generator 54.
2 where it is latched and its latched output is provided to the anode of a segment of the display. On the other hand, a grid voltage is applied to the grid of each display unit from the shift register 55 in a shift manner. Then, only the characters on the display unit to which the grid voltage is applied are displayed as light emission. This light emission display sequentially circulates through a plurality of display units as the output of the shift register 55 shifts, but the driven display units appear to emit light simultaneously due to the afterimage effect of human eyes.

[0004]

However, in the above-mentioned conventional example, a display memory (RA for storing display data at one time) is used.
M) 51 is required, and a timing generator 54 for reading data from the display memory 51 and an oscillator 53 for supplying a clock to the timing generator 54 are required. Therefore, when integrated into an IC, the chip size becomes large. There was a drawback that it would end up.

In view of the above points, an object of the present invention is to provide a fluorescent display tube drive circuit which has a simple circuit configuration and which does not increase the chip size even when integrated into an IC.

[0006]

In order to achieve the above object, according to the present invention, the anodes of the corresponding segments of a plurality of display sections are commonly connected to receive a segment display signal. A dynamic drive type fluorescent display tube drive circuit in which operating voltages are sequentially applied to a grid of a display unit in a shift manner. 1 shift register, a latch register for latching the output of the first shift register and applying it to a segment of the fluorescent display tube, a latch pulse generating circuit for generating a pulse for latching the latch register, and an output pulse of the latch pulse generating circuit In response to this, a second system for sequentially shifting and outputting the voltage applied to the grid of the fluorescent display tube is output. It is provided and Torejisuta.

[0007]

With this structure, the display data transferred serially can be converted into serial / parallel by the first shift register and the latch register, and the display signal for driving the segment can be output. Further, the latch pulse formed by the latch pulse generation circuit is used not only as a latch pulse for the latch register but also as a shift pulse for the second shift register, which is useful for generating the grid voltage.

[0008]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 4, display data is serially transferred from the microcomputer 40 to the fluorescent tube driver 41. The fluorescent display tube driver 41 forms a signal for driving the fluorescent display tube 42 based on this data and supplies it to the fluorescent display tube 42. The fluorescent display tube 42 has, for example, four display parts (A) to (D) as shown in FIG. In this example, the four display parts are 4-digit numbers, but needless to say, they may be characters or marks, and only four display parts are provided. However, the number is not limited to the above and is provided according to the application.

In FIG. 3, the segments a to g of the display unit (A) are connected to the corresponding segments of the other display units (B) to (D). For example, in the segment a, all the segments a of the four display units are connected and the display data of the segment a is commonly received from one input terminal. The same applies to the other segments b to g. Each display (A)
~ (D) grid (not shown) is independent,
Only the display unit to which voltage is applied to the grid emits light. In such a dynamic drive system, the voltage applied to the grid is applied so as to shift the display units (A) to (D).

In FIG. 1 showing the fluorescent display tube driver 41, terminals 1 to 4 are connected to the microcomputer 40, and display data is serially input to the terminal 1 among them. Further, a clock is given from the microcomputer 40 so that data can be taken in in synchronization with the transfer operation of the microcomputer 40. The clock is inputted through the terminal 2 and the shift register 5
Given to.

Reference numeral 6 is a latch register for latching the output of the shift register 5, and its output is given to the anodes of the segments a to g of the display sections (A) to (D). A latch pulse for latching the latch register 6 is generated by the latch pulse generation circuit 7. The latch pulse generation circuit 7 generates a latch pulse in synchronization with a chip select signal supplied from the microcomputer 40 via the terminal 3.

Reference numeral 8 is a shift register for generating a grid voltage, and its Q output is fed back to the preset terminal PR. Further, the reset pulse is received at the reset terminal R from the microcomputer 40 via the terminal 4. The shift register 8 is connected so as to perform a shift operation by a latch pulse given from the latch pulse generation circuit 7.

Now, as shown in FIG. 2, display data DA, DB, DC, DD ... Are sent from the microcomputer 40 by serial transfer. In this case, the display data DA to DD for each of the display units (A) to (D)
Will be sent. This display data is successively input to the shift register 5 in synchronization with the clock from the terminal 2. Then, when the latch pulse P1 is generated from the latch pulse generation circuit 7, the display data DA for the display unit (A) is first latched as shown in synchronization with the rise of the pulse.
Similarly, the display data DB, DC, and DD for the display units (B), (C), and (D) are sequentially latched by the pulses P2, P3, and P4. The display data input from the terminal 1 is serial / parallel converted by the shift register 5 and the latch register 6.

The latch pulses P1 to P4 are also given to the shift register 8. As a result, a high level voltage is generated from the shift register 8 as indicated by. Are applied to the grid of the display unit (A), and similarly, the voltages of to are sequentially applied to the grids of the display units (B), (C) and (D). As a result, the display section (A)
(D) sequentially emits light.

The fluorescent display tube drive circuit of this embodiment is, for example, V
Used in TR. In this case, the microcomputer 40 shown in FIG. 4 is also used as a microcomputer for VTR servo system and system control.

[0016]

As described above, according to the present invention, the display memory, the timing generator, the oscillator, etc., which have been conventionally required, are not required, and the entire structure can be made compact.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a fluorescent display tube drive circuit embodying the present invention.

FIG. 2 is a signal waveform diagram for explaining the operation.

FIG. 3 is a diagram showing a display portion of a fluorescent display tube and its segments.

FIG. 4 is an overall schematic diagram of a fluorescent display tube drive circuit embodying the present invention.

FIG. 5 is a block circuit diagram of a conventional fluorescent display tube drive circuit.

[Explanation of symbols]

 5 1st shift register 6 latch register 7 latch pulse generation circuit 8 2nd shift register ag segment 40 Microcomputer

Claims (2)

[Claims] 1. A dynamic system in which anodes of corresponding segments of a plurality of display units are commonly connected to receive a segment display signal, and operating voltages are sequentially applied in a shift manner to grids of the plurality of display units. In a drive type fluorescent display tube drive circuit, a display data supply circuit for serially transferring display data, a first shift register for inputting the serially transferred display data, and an output of the first shift register are latched. A latch register applied to a segment of a fluorescent display tube, a latch pulse generation circuit for generating a latching pulse for the latch register, an output pulse of the latch pulse generation circuit, and a voltage applied to a grid of the fluorescent display tube are sequentially shifted. And a second shift register for outputting as a fluorescent display tube drive circuit. 2. The fluorescent display tube drive circuit according to claim 1, wherein the display data supply circuit is a microcomputer that controls each unit of the VTR, and the plurality of display units are display units of the VTR. .