JP2000089717A - Dot matrix display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dot matrix display device in which a problem caused by rise in temperature can be previously prevented by reducing a lighting rate in accordance of rise in temperature for each module even when many dot matrix modules using LEDs are arranged and a large display device is constituted. SOLUTION: Plural dot matrix modules are arranged and a large display device is constituted, in each dot matrix module, LED 12 is arranged on the surface side of a substrate 11 in a matrix state to form a display panel 1, and a control circuit and a driving circuit of a light emitting element 12 are formed on the back side. Further, the device is provided with a temperature sensor 6 and a power reducing circuit 7 shortening a lighting time of a light emitting element by a signal of the temperature sensor, when temperature rises, drive power is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dot matrix display device in which a plurality of dot matrix modules in which light emitting elements are arranged in a matrix form a large display device. More specifically, the present invention relates to a dot matrix display device capable of adjusting the lighting rate by lowering the lighting rate for each module when a large display device is configured by arranging a plurality of dot matrix modules and generating a large heat.

[0002]

2. Description of the Related Art In a conventional dot matrix display device, for example, a chip type light emitting element (hereinafter referred to as an LED) is provided on the front side of a display panel substrate 51 as shown in FIG. 52) is 16 ×
A control circuit (not shown) and a control circuit (not shown) are arranged on the rear surface of the display panel substrate 51 in a matrix of 16 or 24 × 24.
A drive circuit for the ED 52 and the like are provided, and a desired character or graphic is displayed by selectively turning on and off the LEDs 52 arranged in a matrix. A number of these units are arranged vertically and horizontally and used as a large display device for display of destinations at stations, public notice boards, and the like. In this case, each module is used to display one character, and each module is controlled and driven.

On the other hand, in this type of display device, when the lighting ratio of the LED of one module increases, the drive current increases and heat is generated, causing problems such as luminance degradation and no lighting. Therefore, a designer who designs a large display device has devised a display state so that the lighting rate of each module does not become too high, or a method that does not increase the temperature too much.

For example, as shown in FIG. 4, a temperature sensor is mounted on a housing (not shown) on which a dot matrix module 31 is mounted, and a pulse generation circuit for reducing power is provided in a signal supply circuit to each unit. 32, and each module 31 is mounted according to a rise in temperature in the housing.
The power supply to the power supply is reduced.

Further, as shown in FIG. 5, a cooling fan 34 is attached to a part of a housing 33 to which the dot matrix module 31 is attached, thereby improving the ventilation of the heat generating portion on the back side of the module 31. Cooling.

[0006] Further, as shown in FIG.
There is also adopted a method of reversing the light emitting portion B and the non-light emitting portion B to reduce the lighting rate.

[0007]

As described above, when the temperature sensor is provided somewhere in the housing and the power reduction circuit is operated according to the detected temperature, the display may be different in each module or the display may be different. When the lighting rate of a module becomes extremely high, the temperature rise of the module cannot be detected and detected sufficiently, or the power supply to all modules is reduced due to some temperature rise. In addition, there is a problem that even a module whose lighting rate is not high becomes dark and the display becomes difficult to see.

In addition, the method of providing a cooling fan requires a space for mounting the cooling fan, and has a problem that the temperature cannot be sufficiently lowered when the lighting rate is extremely high.

Further, even in the method of inverting light emission and non-light emission when the lighting rate is high, if the lighting rate differs between units, the unit having a low lighting rate reverses the lighting rate to increase the lighting rate. Thus, there is a problem that the lighting rate cannot be optimized in all units. There is also a problem that the range of the display pattern is limited, and the amount of information displayed is reduced.

The present invention has been made to solve such a problem. Even when a large number of dot matrix modules using LEDs are arranged to form a large display device, the present invention is applied to each module. It is an object of the present invention to provide a dot matrix display device that can reduce a lighting rate in accordance with a rise in temperature and can prevent a problem caused by the rise in temperature.

[0011]

According to the present invention, there is provided a dot matrix display device in which light emitting elements are arranged in a matrix on a front surface of a substrate, and a control circuit and a driving circuit for driving the light emitting elements are formed on a back surface. What is claimed is: 1. A dot matrix display device comprising: a plurality of modules arranged to form a large display device, wherein the dot matrix module includes a temperature sensor and a power reduction circuit for shortening a lighting time of the light emitting element by a signal of the temperature sensor. Each is provided on the back side of the substrate of the module.

According to this structure, a temperature sensor and a power reduction circuit for reducing the power supplied to the light emitting element in accordance with the temperature rise are provided for each dot matrix module. An abnormality can be detected and the power supplied to the module can be reduced. As a result, it is possible to reduce the lighting rate of only the module with a high lighting rate, further reduce the lighting rate of a module with a low lighting rate, or lower the lighting rate on average even if there is a module with a high lighting rate. There is no need to lower it, and control can be performed reliably.

[0013]

Next, a dot matrix display device of the present invention will be described with reference to the drawings.

In the dot matrix display device of the present invention, a large-sized display device is constituted by arranging a plurality of dot matrix modules, and each dot matrix module has a substrate 11 as shown in the block diagram of FIG.
The display panel 1 is formed by arranging LEDs (light emitting elements) 12 in a matrix on the front side of the display panel, and a control circuit (control gate) is provided on the back side (in the drawing, a block diagram is provided in parallel with the display panel 1). An array (IC) 2, a common driver (IC) 3) and a drive circuit for the LED 12 (red and green segment drivers 4, 5) are formed. Further, a temperature sensor 6 and a power reduction circuit 7 for shortening the lighting time of the LED according to the temperature rise by a signal from the temperature sensor are provided for each dot matrix module in this example by a control gate array (I
C) 2.

The display panel 1 has a wiring pattern (not shown) formed on the surface of a substrate 11 made of, for example, an aluminum core substrate or glass epoxy, and chip-type LEDs 12, for example, 16 × 16 on the surface thereof. A display portion is formed by being arranged. Although shown in the figure alongside the display panel 1, actually, a control gate array 2 for controlling a drive signal is provided on the back side of the display panel 1, for example, a common signal is sequentially applied from the first column to the sixteenth column. A common driver 3 for scanning, and segment drivers 4 and 5 including resistors for driving the LEDs (in the figure, the LED 12 includes two types of red and green LED chips, and can be driven separately. Is provided). Then, only the pixels selected by the common signal of the common driver 3 and the segment signals of the segment drivers 4 and 5 are turned on. This configuration is the same as the configuration of a conventional dot matrix module using LEDs.

The LED is covered with a dome-shaped package in addition to the above-mentioned chip type light-emitting element in which a light-emitting diode chip is bonded to a flat substrate surface and the periphery thereof is covered so as to make the surface flat. Light-emitting elements using LED chips, such as lamp-type light-emitting elements, are advantageously used.

The temperature sensor 6 is, in the example shown in FIG.
A thermistor whose resistance value changes with temperature is used. A time constant circuit is formed by the resistance R of the thermistor 6 and the capacitance C of the capacitor 8, and the resistance R of the thermistor changes with temperature and the time constant changes. It has become. Then, the power reducing circuit 7 for shortening the lighting time of the LED according to the temperature rise of the temperature sensor 6 includes:
For example, a monostable multivibrator (monomulti circuit) is used, and a trigger pulse (scan clock) T
Input, a pulse with a pulse width corresponding to the time constant described above is output.
Is turned on, and when the temperature rises and the resistance of the thermistor decreases, the charge of C increases and the pulse width decreases.

For example, when the temperature of the module rises, a pulse having a narrow pulse width is generated by the above-described power reducing circuit 7, and as shown in FIG. A common signal of a pulse having a narrow width is applied. As a result, the time that is applied to the pixel that is turned on by the segment signal applied to each segment line from the segment driver is shorter than the common signal, so that the pixel is turned on only for a short time. That is, the lighting time is reduced, and the lighting rate can be reduced with respect to the entire time.

The above-mentioned temperature sensor 6 is most sensitively provided, for example, near a resistor for driving the LED.
This is preferable because it is easy to detect a rise in temperature due to lighting, that is, an increase in the lighting rate. In addition, as shown in FIG. 1, the power reduction circuit 7 such as the above-mentioned monostable multivibrator can be monolithically integrated in the conventional control gate array (IC) 2 so as to save space. Each module can be provided. Therefore, only by externally connecting the thermistor or the thermistor and the capacitor alone, it is possible to monitor the temperature rise due to the lighting rate of each module and always optimize the lighting rate of each module.

According to the present invention, since a temperature sensor and a power reduction circuit are provided for each module, when a large display device is constructed by arranging a plurality of dot matrix modules, the lighting rate is increased for each module. The temperature rise is detected, and if the temperature is rising, the lighting rate can be automatically adjusted. Therefore, control can be performed with much higher accuracy than when a sensor is attached to the housing side and the whole module is controlled collectively,
The lighting rate of a module with a low lighting rate can be reduced without further lowering the lighting rate of a module having a low lighting rate, and even if only one module with a high lighting rate is affected, without affecting the display of other modules. .

[0021]

As described above, according to the present invention, the lighting rate of each module can be automatically controlled by the power reduction circuit, so that a large display device can be manufactured using the module. This eliminates the need for the user to develop display software while paying attention to the lighting rate at the time of design, and to consider a circuit for reducing the display software, making it possible to design a large display device very easily. As a result, the number of design steps can be reduced.

Further, there is no need to provide a cooling fan, and the space for mounting the fan and the number of components (fans) can be reduced, which contributes to cost reduction.

Further, since the LED can be operated at a stable temperature, it is possible to protect the life of the LED, circuit components for driving the LED, and electronic components in the vicinity thereof,
The reliability can be greatly improved.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a configuration example of one module of an embodiment of a dot matrix display device of the present invention.

FIG. 2 is a diagram illustrating an example of a common signal as an example of driving for lowering a lighting rate by the power reduction circuit of FIG. 1;

FIG. 3 is a perspective explanatory view of an example of a conventional dot matrix display device.

FIG. 4 is an explanatory diagram of an example in which the lighting rate of a conventional dot matrix display device is reduced.

FIG. 5 is an explanatory diagram of another example of reducing the lighting rate of the conventional dot matrix display device.

FIG. 6 is an explanatory diagram of another example of reducing the lighting rate of the conventional dot matrix display device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 display panel 2 control gate array 6 temperature sensor (thermistor) 7 power reduction circuit

Claims (1)

[Claims] 1. A large-sized display device is formed by arranging light-emitting elements in a matrix on a front surface of a substrate, and arranging a plurality of dot matrix modules on which a control circuit and a drive circuit for the light-emitting elements are formed on a rear surface. A dot matrix display device, wherein a temperature sensor and a power reduction circuit for shortening the lighting time of the light emitting element by a signal of the temperature sensor are provided on the back side of the substrate of the dot matrix module for each dot matrix module. Dot matrix display device.