JPH1026958A - Drive circuit for fluorescent display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to inspect a driven circuit (semiconductor chip) even when it is not completed and to suppress the futile use of parts caused by fault occurrence by connecting respective outputs of respective driven parts (respective transistors) with an AND circuit. SOLUTION: The outputs from respective transistors 32 are connected with the AND circuit 1. When either one of a shift register circuit 41, a latch circuit 33 or the transistor 32 is abnormal, an anode voltage is not supplied to a phosphor 23 connected to it. Then, the anode voltage isn't supplied to the AND circuit 1 connected to the output of the transistor 32 supplying the anode voltage. Thus, even when 'H' is inputted from this side AND circuit 1 connected to this AND circuit 1, 'L' is outputted from such a AND circuit 1. Then, the output TO from a connected AND circuits group becomes zero, and it is judged that this semiconductor chip is a fault. That is, the presence of a dot fault is detected by the state of the semiconductor chip.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit of a fluorescent display device for displaying characters and symbols using a phosphor, and more particularly, to a phosphor pixel integrally formed on a semiconductor integrated substrate in a dot matrix. The present invention relates to a driving circuit for a fluorescent display device.

[0002]

2. Description of the Related Art In a fluorescent display device, as a device for displaying various characters or performing graphic display, there is a device in which phosphor pixels are formed in a dot matrix. Generally, in this type of fluorescent display device (a fluorescent display tube with a built-in shift memory), a phosphor layer is formed on a part of a semiconductor chip having a semiconductor integrated circuit for drive control, and a large number of phosphor pixels are formed in a dot matrix. Various characters, symbols, and the like are displayed by providing them in a shape and driving them.

FIG. 2 is an explanatory view showing a cross section of the above-mentioned general fluorescent display tube. As shown in FIG. 2, a semiconductor chip 22 is formed on a glass substrate 21. On the semiconductor chip 22, although not shown, dot-shaped anodes are formed in a matrix, and a phosphor 23 is formed thereon to form a phosphor pixel. A filament (cathode) 24 for emitting electrons is provided above the semiconductor chip 22, and an electron diffusion grid 25 is provided between the filament 24 and the semiconductor chip 22.

A bonding wire 27 drawn from a terminal 26 on the semiconductor chip 22 is connected to a wiring pattern 28 on the glass substrate 21. On the other hand, a windshield 21 a is arranged on the glass substrate 21 via a spacer glass 29. These are sealed by a sealing frit glass 29a, and the glass substrate 2
1, front glass 21a and spacer glass 2
The space enclosed by 9 is evacuated. One end of a lead pin 30 is connected to the wiring pattern 28, and the lead pin 30 is connected to the glass substrate 21 and the spacer glass 2.
9 through the inside of the sealing frit glass 29a.

FIG. 3 is a schematic circuit diagram of a display section of the above-described fluorescent display tube. As shown in FIG.
The light emitting element 31 includes an anode 23a and a phosphor 23.
(Phosphor pixel) and a transistor 32 for driving the same. The transistor 32 is connected to the latch circuit 33
Is turned on / off based on the display data stored in the memory 23, and the phosphor 23 is switched to the anode voltage (positive voltage) in accordance with the on / off operation.
Becomes Then, the thermoelectrons emitted from the filament 24 driven by the driving power supply 36 collide with the phosphor 23 via the electron diffusion grid 25. Then, the phosphor 23 hit by the electrons emits fluorescent light.

FIG. 4 is a circuit diagram showing a configuration of a driver (drive circuit) in the above-mentioned display unit. In particular, the case where the light emitting elements 31 form a 16 × 16 dot matrix is shown. As shown in FIG. 4, the shift register circuit 41 includes the light emitting elements 31 (# 1 to # 25).
6), the display data corresponding to each light emitting element 31 is provided by a clock signal CLK.
Are sequentially shifted in the direction indicated by the shift direction selection signal L / R. Then, the output from the shift register circuit 41 is held in the latch circuit 33 based on the latch signal LAT, and is output to the transistor 32 (FIG. 3).

Next, the operation will be described with reference to FIG. When the shift direction selection signal L / R for selecting the shift direction of the display data in the shift register circuit 41 is at "H" level, the display data of each of the light emitting elements # 1, # 2,. The data is sequentially input from the serial input SI. These display data are based on light-emitting elements # 1, # 2,.
-Each shift register circuit 41 corresponding to # 256 sequentially shifts.

After each display data is shifted to the corresponding shift register circuit 41, the latch signal LA
T is input, and the display data output from each shift register circuit 41 at that time is stored in each latch circuit 3.
3 is output. As a result, the display data held and output by the latch circuit 33 is input to each light emitting element 31, and the transistor 32 (see FIG. 3) in the light emitting element 31 is driven in response to this, and the phosphor 23
The supply of the anode voltage to the (anode 23a) is controlled, and a display corresponding to each display data is output.

In the above description, for each light emitting element 31,
Shift register circuit 41 for sequentially shifting display data
And a latch circuit 33 for holding and outputting the output from the shift register circuit 41 to the light emitting elements 31 so as to input the display data to each light emitting element 31 as serial data. With this configuration, the number of signal lines on the semiconductor chip and the number of signal lines to be supplied to the semiconductor chip are reduced as compared with the case where a plurality of XY addresses are input to the semiconductor chip. Is simplified. Then, the number of wire bonding is reduced, the yield is improved, and the price can be reduced.

The shift direction selection signal L / R is "L".
In the case of the level, contrary to the above, each light emitting element #
The display data of # 1,..., # 256 is input from the serial output S0 in order from the light emitting element # 1. These display data are sequentially shifted by the shift register circuit 41 of the light emitting elements # 256, # 255,... # 1, based on the clock signal CLK.

After each display data is shifted to the corresponding shift register circuit 41, the latch signal LAT is input, and the display data output from each shift register circuit 41 at that time is stored in the corresponding latch circuit 33. Is held and output. As a result, the display data held and output by the latch circuit 33 is input to each light emitting element 31, and the light emitting element 3
1, the transistor 32 (see FIG. 3) is driven to control the supply of the anode voltage to the phosphor 23 (the anode 23a),
A display corresponding to each display data is output.

[0012]

The above-mentioned inspection for checking whether or not the phosphor pixels of the fluorescent display tube and the surrounding circuits are normal is generally carried out in a state in which the fluorescent display tube is completed and all of the fluorescent materials are checked. This is performed by causing the pixels to emit light. In a state where all the phosphor pixels are controlled to emit light, if there is a phosphor pixel that does not emit light, it is determined that this is a defect (dot defect). Here, if the cause of the dot defect is an abnormality of the above-described transistor, latch circuit, or shift register circuit, manufacturing processes other than the semiconductor chip (drive circuit), such as formation of an electron diffusion grid, are wasted. Would.

That is, after a large number of semiconductor chips are formed on a silicon wafer, they are individually cut out, arranged in a matrix, and connected by wiring to obtain a wider display area. After that, an electron diffusion grid, a filament, and the like are arranged thereon, sealed with a windshield and a spacer glass, and the inside thereof is evacuated to manufacture a fluorescent display tube. Therefore, if a defect exists in the semiconductor chip, the entire fluorescent display tube becomes defective even if there is no problem in other parts, and all parts other than the semiconductor chip are wasted. In addition, the cost of manufacturing is wasted.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to reduce the waste of components due to the occurrence of defects in the manufacture of a fluorescent display device.

[0015]

A driving circuit for a fluorescent display device according to the present invention has a large number of phosphor pixels each including an anode formed on a semiconductor chip and a phosphor layer formed thereon. A drive unit provided for each phosphor pixel and applying an anode voltage to its anode, and a shift register provided for each phosphor pixel and sequentially shifting display data corresponding to each phosphor pixel based on a predetermined clock signal Circuit, and a latch circuit provided for each phosphor pixel and holding an output from a corresponding shift register circuit as individual display data based on a predetermined latch signal and outputting the display data to a driving unit. Are connected by an AND circuit. For this reason, the final output of the connected AND circuit becomes “1” only when the anode voltages are output from all the driving units.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a configuration of a driver (drive circuit) in a display unit of a fluorescent display tube (fluorescent display device) according to an embodiment of the present invention. As shown in FIG. 1, in this embodiment, outputs from respective transistors (drive units) 32 are connected by an AND circuit 1. The other reference numerals are the same as those in FIGS. Then, when "H" is input to all the register circuits, the output TO from the connected AND circuit group becomes "L".
Is determined, the semiconductor chip is determined to be defective.

The operation for determining a defect will be described below. For example, the shift direction selection signal L / R for selecting the shift direction of the display data of the semiconductor chip to be inspected in the shift register circuit 41 is set to “H” level. Then, display data (“H”) for causing all the phosphor pixels to emit light is input from the serial input SI in order from the last phosphor pixel. These display data are sequentially shifted by the corresponding shift register circuits 41 sequentially from the first phosphor pixel based on the clock signal CLK.

After each display data is shifted to the corresponding shift register circuit 41, the latch signal LA
T is input. Then, the display data output from each shift register circuit 41 at that time is held and output by each latch circuit 33. As a result, the display data held and output by the latch circuit 33 is input to each light emitting element 31, and the transistor 32 in the light emitting element 31 is driven in response to this, so that the anode voltage is supplied to the phosphor 23. Controlled.

At this time, since the data (“H”) for displaying all the phosphor pixels has been input, the output TO from the connected AND circuit group should be “H”. However, if any of the shift register circuit 41, the latch circuit 33, and the transistor 32 are abnormal, the anode voltage is not supplied to the phosphor 23 (anode 23a) connected thereto. As a result, in the AND circuit 1 to which the output of the transistor 32 that supplies the anode voltage is connected, the anode voltage is not supplied. Therefore, even if this AND circuit 1
Even if "H" is input from the AND circuit before connecting to the terminal, "L" is output from the AND circuit. Then, the output TO from the connected AND circuit group becomes “0”, and this semiconductor chip is determined to be defective.

As described above, according to this embodiment, a dot defect in which the anode voltage is not partially output to the phosphor 23 (anode 23a: FIG. 3) is observed in the state of the fluorescent display. Can be detected without the need. That is, according to this embodiment, even if the fluorescent display tube is not completed,
The presence or absence of a dot defect can be detected in the state of the semiconductor chip.
For this reason, there is no need to inspect the device after completing it as a fluorescent display tube through processes such as arranging an electron diffusion grid or filament, sealing with a windshield and a spacer glass, and evacuating the inside without any defect. Only the semiconductor chip (drive circuit) can be used as a component of the fluorescent display tube.

[0021]

As described above, according to the present invention, a large number of phosphor pixels each including an anode formed on a semiconductor chip and a phosphor layer formed thereon are provided. A driving unit provided for applying an anode voltage to the anode; a shift register circuit provided for each phosphor pixel and sequentially shifting display data corresponding to each phosphor pixel based on a predetermined clock signal; A latch circuit provided for each body pixel, for holding output from a corresponding shift register circuit as individual display data based on a predetermined latch signal and outputting the data to a drive unit, and outputting an output of each drive unit to an AND circuit Was connected.

By doing so, the final output of the connected AND circuit becomes "H" only when the anode voltages are output from all the driving units, so that all the phosphor pixels are driven to display. When the circuit is controlled, if the final output of the connected AND circuit is “L”, it can be determined that the drive circuit is defective. As a result, according to the present invention, it is possible to inspect the drive circuit without making it a completed state,
This has the effect of reducing waste of components due to the occurrence of defects.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a driver (drive circuit) in a display unit of a fluorescent display device according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a cross section of a general fluorescent display tube.

FIG. 3 is a schematic circuit diagram of a display unit of the fluorescent display tube.

FIG. 4 is a circuit diagram showing a configuration of a driver (drive circuit) in a display unit of the fluorescent display tube.

[Explanation of symbols]

1 ... AND circuit, 22 ... Semiconductor chip, 23 ... Phosphor,
23a: anode, 24: filament (cathode), 25: electron diffusion grid, 32: transistor, 33: latch circuit, 41: shift register circuit.

Claims (2)

[Claims] An image display apparatus comprising: a plurality of phosphor pixels each including an anode formed on a semiconductor chip and a phosphor layer formed thereon; and outputting individual display data to these phosphor pixels. A driving circuit provided for each phosphor pixel and applying an anode voltage to the anode; and a driving circuit provided for each phosphor pixel and provided for each phosphor pixel. A shift register circuit for sequentially shifting display data corresponding to a body pixel based on a predetermined clock signal, and an output from the corresponding shift register circuit provided for each phosphor pixel and corresponding to the predetermined latch signal, based on a predetermined latch signal. A latch circuit for holding as display data and outputting the data to the driving unit, wherein outputs of the driving units are connected by an AND circuit. The drive circuit. 2. The drive circuit for a fluorescent display device according to claim 1, wherein the shift register circuit comprises a bidirectional shift register circuit for switching a display data shift direction based on a predetermined shift direction selection signal. Driving circuit for a fluorescent display device.