JPH08115056A - Display device - Google Patents

Abstract

PURPOSE: To provide a display device easy for adjusting luminance and capable of miniaturizing by connecting a metallic terminal with a metallic fine wire of a prescribed combination, selecting a prescribed current and making the current when all input terminals are connected by the metallic fine wires the same as the current when all input terminals are opened. CONSTITUTION: The current is selected by connecting the input terminals of one combination to the metallic fine wires 30-32 in a current selection means 18, and a drive current is supplied to a light emitting diode 14 according to the current. Then, the luminance is measured, and when the luminance is low, the input terminal of other combination is connected to the metallic fine wires 30-32 so as to select the current of the current selection means 18 for increasing the drive current. In such a manner, by combining the input terminals to the prescribed metallic fine wires 30-32, the required current is selected, and the required luminance is obtained easily. Further, the current connecting and selecting all input terminals to the metallic fine wires 30-32 is made the same as the current opening and selecting the input terminal. Thus, two ways of luminance adjustment are performed, and convenience is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device having a light emitting diode.

[0002]

2. Description of the Related Art Conventionally, a display device having a light emitting diode is disclosed in, for example, Japanese Utility Model Laid-Open No. 62-83640, which will be described with reference to the block diagram of FIG. In FIG. 5, data is supplied to the shift register 61, and the data is sent to the driving means 63 via the latch circuit 62. The output current is supplied from the current supply means 64 to the drive means 63, and the drive current is supplied from the drive means 63 to the light emitting diode array 65.
And the light emitting diode 66 is selectively turned on. The variable resistor 6 is provided in the current supply means 64.
7 is provided, the output current is increased or decreased by adjusting it, and the brightness of the light emitting diode array 65 is adjusted.

[0003]

However, in the above-described display device, first, the variable resistors 67 are set to arbitrary values, all the light emitting diodes 66 are turned on, and the luminance is measured. When the brightness does not reach the desired value, the variable resistor 67 is readjusted and the same operation is repeated. As described above, since the variable resistor 67 is adjusted by trial and error to adjust the brightness, there is a drawback that the resistance adjustment needs to be performed at least 3 to 4 times. Further, the variable resistor 67 requires a comparatively large space and has a drawback that the display device cannot be downsized. Therefore, the present invention takes such a conventional defect into consideration,
It is an object of the present invention to provide a display device in which the brightness can be easily adjusted and the size can be reduced.

[0004]

In order to solve the above-mentioned problems, the present invention comprises a current selecting means and a driving means for supplying a driving current to a light emitting diode according to the current selected by the current selecting means. , The current selection means selects a predetermined current by connecting a predetermined combination of input terminals to a metal thin wire, and a current when all input terminals are connected by a metal thin wire,
The current is the same when all the input terminals are opened.

[0005]

As described above, the present invention selects a current by connecting one combination of input terminals to a thin metal wire in the current selecting means, and supplies a drive current to the light emitting diode according to the current. Then, the luminance is measured, and if the luminance is low, the input terminal of another combination is connected to the metal thin wire so that the current of the current selecting means is selected to increase the drive current. In this way, by combining the input terminal with a predetermined thin metal wire, a desired current can be selected and a desired brightness can be easily obtained.

Further, all the input terminals are connected to the thin metal wires and the selected current is made equal to the selected current by opening the input terminal. Therefore, the convenience can be improved by two methods, one is to connect all the input terminals to the thin metal wires and cut the thin metal wires to adjust the brightness, and the other is to open the input terminal and connect the thin metal wires to adjust the brightness. To do.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference examples based on which the present invention is based are shown in FIG. 1 and FIG.
Follow the explanation below. FIG. 1 is a sectional view of a display device according to the present reference example, and FIG. 2 is a sectional view taken along the line AA of FIG. In these figures, the radiator 1 is made of a material having a high thermal conductivity, such as an extruded aluminum material, and is long. The substrate 2 is provided on the radiator 1 and is made of, for example, ceramic mixed resin or the like, and the conductive patterns 3, 4, 5, 6 are formed on the surface thereof.
The size is, for example, about 227 mm in length and about 13 m in width.
m, and the length is about 1 mm.

The light emitting diode array 7 is formed by forming an epitaxial layer made of gallium arsenide phosphide on a semiconductor substrate made of gallium arsenide, for example. The light-emitting diode array 7 has light-emitting regions (light-emitting diodes) arranged on the front surface in one row or in two or three rows in a zigzag pattern, individual electrodes ohmic-contacted with the light-emitting areas, and a common electrode (neither shown) on the back surface. Has been formed. On the surface of one light emitting diode array 7, for example, at a pitch of about 125 μm, 6
The four light emitting regions are aligned, and the size thereof is about 8 mm in length, about 2 mm in width, and about 0.35 mm in thickness.
A plurality of light emitting diode arrays 7 are fixed on the conductive pattern 3 of the substrate 2 via a conductive adhesive so that the light emitting diode arrays 7 are closely arranged and aligned in the longitudinal direction of the substrate 2.

The integrated circuit element 8 is a conductive pattern 4 on the substrate 2.
One is wired to the light emitting diode array 7 by a thin metal wire, and the other is wired to the conductive patterns 5 and 6, which are fixed to each other via an insulating adhesive.

The support 9 is arranged on the substrate 2, is made of, for example, polybutylene terephthalate resin, and has a through hole on the upper surface and projections 10 formed at appropriate positions on the side surfaces. The lens array 11 is arranged in the through hole of the support 9 and fixed by an adhesive,
It is composed of a short focus rod lens array. The fixture 12 is for integrally fixing the radiator 1, the substrate 2, and the support body 9 by inserting the holes on the side faces into the convex portions 10.
For example, it is made of a stainless plate. The display 13 of this reference example is configured by these members.

Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 3 is a block diagram of the display device according to the present embodiment, and FIG. 4 is a detailed view of essential parts of FIG. In these figures, the light emitting diode array 7 is composed of, for example, 64 light emitting diodes 14 as described above, and each integrated circuit element 8 is wired to each light emitting diode array 7.

The shift register 15 in the integrated circuit element 8 outputs data supplied in series, that is, binary numbers instructing lighting or non-lighting in parallel. The latch circuit 16 is connected to the shift register 15 and stores data. The AND gate 17 receives the data and the strobe signal from the latch circuit 16 and outputs a lighting signal.

The current selection means 18 is provided with, for example, three input terminals 19, 20 and 21, and the respective input terminals 19 and 2 are provided.
Terminals 22, 23, 24 are provided close to 0, 21,
Both are grounded. Voltage setting circuits 25, 26, 27 are connected to the respective input terminals 19, 20, 21. A logic circuit 28 is connected to each of the input terminals 19, 20, 21 and
Output lines are connected. Each output line is connected to the resistors R1 to R7 via the transistor 29.
The resistance values of the resistors R1 to R7 are, for example, standard values ±
0%, -10%, -30%, -20%, + 10%, +3
It is set to a value that the manufacturer can know in advance so that it becomes 0% or + 20%.

In the above-mentioned current selecting means 18, the input terminals 19, 20, 21 and the terminals 22, 23, 24 are connected by thin metal wires 30, 31, 32 in a predetermined combination. In FIG. 3, in the first integrated circuit element 8, all the metal wires 30, 31, 32 are connected, and in the third integrated circuit element 8, all the input terminals 19, 20, 21 are open. When the input terminals 19, 20 and 21 are open in FIG. 4, a Hi level voltage is applied to the input terminals 19, 20 and 21 (indicated as 1 in the figure). Inverters 33, 3 connected to input terminals 19, 20, 21
The Lo level voltage is applied to the output lines passing through 4 and 35 (displayed as 0 in the figure). These three output lines are properly combined to form an AND gate 36 with an inverter in order from the right side in the order of 000, 100, 010, 110, 00.
Voltages of 1, 101, 011 and 111 are applied.
These outputs are OR gate 37 and six inverters 38.
The voltage of 1, 0, 0, 0, 0, 0, 0 is applied to the seven transistors 29, and only the rightmost transistor 29 is energized. As a result, when the input terminals 19, 20, 21 of the current selecting means 18 are opened, that is, when the thin metal wire is not connected, the resistor R1 is selected and the current i
₁ = 1.8 / R1 is selected.

Also, the input terminals 19, 20, 21 and the terminal 2
2, 23, 24 and thin metal wires 30, 31, 32, respectively.
Is connected, only the transistor 29 on the rightmost side is energized, the resistor R1 is selected, and the current i ₁ = 1.8 / R1 is selected, as is understood from the above description.

Thus, the following table shows selected resistances and selected currents for various combinations in which the input terminals 19, 20, 21 are combined with thin metal wires.

[0017]

[Table 1]

In this table, ADJ1, ADJ2 and AD
J3 indicates between the input terminal 19 and the terminal 22, between the input terminal 20 and the terminal 23, and between the input terminal 21 and the terminal 21, respectively. 0 and 1 indicate that they are connected with a metal thin wire and that they are opened. As can be seen from this table, input terminals 19 and 2
A desired resistance can be selected and a desired current can be selected by a combination of connections of 0 and 21 and a thin metal wire.

The current supply means 39 comprises a voltage dividing circuit 40, an operational amplifier 41, and transistors 42 and 43. The negative terminal of the operational amplifier 41 is connected to the voltage dividing circuit 40, and the positive terminal is connected to the common line 44 of the resistors R1 to R7. The output terminal of the operational amplifier 41 is commonly connected to the transistor 42 and the output line 45. When a predetermined voltage V ₁ is applied to the terminal 46, the voltage dividing circuit 40 applies, for example, 1.8 V to the negative terminal of the operational amplifier 41. If the resistance selected from the resistances R1 to R7 is R, the current selected by the current selection means 18, that is, the current i ₁ flowing through the common line 44 is i ₁ = 1.8 / R.

The driving means 47 comprises, for example, an inverter 48 and four transistors 49, 50, 51 and 52,
The source of the transistor 52 is connected to the terminal D1, and the terminal D1 is connected to the light emitting diode 14. And
The source of the transistor 49 is connected to the output line 45, and the gate of the transistor 49 is connected to the output line of the AND gate 17. The drain of the transistor 50 is terminal 4
6 and the drain of the transistor 52 is connected to the output line from the terminal 53. Similarly, a total of 64 driving means 47 are provided for each AND gate 17.
Of the output line and the output line 45 are commonly connected to the terminal D1.
To D64.

A clock signal is commonly applied to, for example, 27 shift registers 15 by a common line connected to the terminal 54. Then, a latch signal is commonly applied to the 27 latch circuits 16 by the common line connected to the terminal 55. A line connected to the terminal 56 supplies serial data to the 27 shift registers 15. Then, by the common line connected to the terminal 57, 64 × 27 = 172
A strobe signal is commonly applied to the eight AND gates 17.

Next, the operation of the display device of this embodiment will be described again with reference to FIGS. First, as described above, the input terminals 19, 20, and 21 are selectively wired with a thin metal wire in a predetermined combination. For example, do not wire as shown in FIG.
The input terminals 19, 20, 21 are opened. At this time, as described above, the logic circuit 28 of the selecting means 18 and each element 36, 3
As shown in the table, the resistance R1
(Reference resistance) is selected. That is, the current supply means 39
The output line 44 of is connected to the ground via the resistor R1.

Then, 1728-bit data (s) is sent to the clock signal (CLOC) from the terminal 54 via the terminal 56.
It is sequentially supplied to 27 shift registers 15 in synchronization with K). Next, the latch signal (LAT
CH) enters each latch circuit 16, 64-bit data is read from the shift register 15, and the AND gate 1
7 is output. A strobe signal (STROBE) indicating a lighting time is input to the AND gate 17 via a terminal 57, ANDed with the above-described data, and a lighting signal (a signal indicating whether to light or not to light) is driven. Output to the means 47.

In the current supply means 39, the operational amplifier 41
Is formed in the negative feedback loop, the voltage at the position 58 is maintained at 1.8V even if the voltage V2 fluctuates.
As a result, a constant current i ₁ = 1.8 / R flows through the output line 44.

Next, in the drive means 47, the current supply means 3
An output current is supplied from the output line 45 of No. 9 and a lighting signal is supplied from the AND gate 17. Then, when the lighting signal becomes Hi level, the transistor 49 is turned on, and the voltage at the position 59 is transmitted to the gate of the transistor 52. At this time, a circuit including the transistor 43 and the like and a circuit including the transistor 52 and the like form a current mirror circuit, and the mirror ratio is set to 1: 2, for example. as a result,
The driving current i ₂ (current flowing through the light emitting diode 14 via the terminal D1) is i ₂ = 2 × i ₁ = 3.6 / R.

Further, the drive current i ₂ is the operational amplifier 4 described above.
1 makes it substantially constant with respect to the fluctuation of the voltage V2. That is, in one light emitting diode array 7, even if the number of light emitting diodes 14 that are turned on changes, the current flowing through each light emitting diode 14 becomes substantially constant. With the above operation, the light emitting diode 14 can be selectively turned on.

Also, in manufacturing, all data (s) is H
A light source of i level is supplied to turn on all the light emitting diodes 14. Then, the luminance is measured for each light emitting diode array 7. As a result, if the measured luminance is within the allowable range of the desired value, the connection of the output terminals 19, 20, and 21 of the selection means 18 may be left as it is.

However, for example, the measured luminance is -30 of the desired value.
%, It is necessary to adjust the current brightness to + 30%. If the brightness is within ± 30%, the brightness and the drive current change linearly, so the drive current is + 30%.
You can adjust it to. Further, as described above, the drive current i ₂ =
Since it is 3.6 / R, the resistance R should be set to -30%.

That is, from the above table, the current selection means 18
If R3 is selected as the resistor R so that the current of ₁ is obtained as the desired value i ₁ , ADJ1 = 1, ADJ2 = 1,
It is understood that the combination of ADJ3 = 0 should be used. That is,
Only the output terminal 21 and the terminal 24 may be connected by the thin metal wire 21.

Next, all the light emitting diodes 14 are turned on by this combination of the output terminals 19, 20, and 21, and the luminance is measured. As a result, the measured luminance falls within the allowable range of the desired value according to the theory described above. By thus configuring the present invention, the brightness can be adjusted at most once and the desired brightness can be obtained for the display device.

Further, as the initial setting of the resistance R, as described above,
In order to open the input terminals 19, 20, 21 and adjust the brightness, thin metal wires are selectively connected to the input terminals 19, 20, 21. This is called the first means. As the initial setting of the resistance R, as shown in the first integrated circuit element 8 of FIG. 3, the input terminals 19, 20, and 21 are all metal thin wires 30,
Connected with 31 and 32, thin metal wire 3 to adjust brightness
0, 31, 32 are selectively cut. This is called the second means.

As described above, in the second means, since the fine metal wires 30, 31, 32 are simply cut to adjust the brightness, the work is easier than the wiring. However, thin metal wire 3
After cutting 0, 31, 32, the chips may be left on the circuit and short-circuited. Further, in this display device, the resistors R1 to R7 can be formed by printing, and the thin metal wires 30, 31 and 32 can be formed in a small space, and thus can be incorporated in one integrated circuit element 8. Therefore, unlike the conventional case, a variable resistor which requires a large space does not have to be externally attached to the integrated circuit element, and the size can be reduced.

In the above-mentioned display device 13, an optical print head having a plurality of light emitting diode arrays 7 and a plurality of integrated circuit elements 8 is illustrated. However, the present invention is not limited to this example, but can be applied to a display device having, for example, one light emitting diode array 7 and one integrated circuit element 8.

[0034]

As described above, the present invention selects a current by connecting one combination of input terminals to a thin metal wire in the current selecting means, and supplies a drive current to the light emitting diode according to the current. To do. Then, the luminance is measured, and if the luminance is low, the input terminal of another combination is connected to the metal thin wire so that the current of the current selecting means is selected to increase the drive current.
In this way, by combining the input terminal with a predetermined thin metal wire, a desired current can be selected and a desired brightness can be easily obtained.

Further, all the input terminals are connected to the thin metal wires and the selected current is made equal to the selected current by opening the input terminal. Therefore, the convenience can be improved by two methods, one is to connect all the input terminals to the thin metal wires and cut the thin metal wires to adjust the brightness, and the other is to open the input terminal and connect the thin metal wires to adjust the brightness. To do.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a display device according to a reference example on which the present invention is based.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a block diagram of a display device according to an exemplary embodiment of the present invention.

FIG. 4 is a detailed view of a main part of FIG.

FIG. 5 is a block diagram of a conventional display device.

[Explanation of symbols]

 14 Light Emitting Diode 18 Current Selection Means 19, 20, 21 Input Terminals R1, R2, R3, R4, R5, R6, R7 Resistor 39 Current Supply Means 47 Driving Means

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Fukushi Higuchi 2-5-5 Keihan Hondori, Moriguchi City, Osaka Prefecture Sanyo Electric Co., Ltd. (72) Inventor Akiyoshi Sudo 2-5 Keihan Hondori, Moriguchi City, Osaka Prefecture No. 5 Sanyo Electric Co., Ltd.

Claims (1)

[Claims] 1. A current selecting means and a driving means for supplying a driving current to a light emitting diode according to a current selected by the current selecting means, wherein the current selecting means has a predetermined combination of input terminals as a metal thin wire. A display device, characterized in that a predetermined current is selected by connecting to, and a current when all the input terminals are connected with a thin metal wire and a current when all the input terminals are opened are provided in the same manner.