JPS63284598A - information display device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an information display device using a light emitting diode as a display element.

[Conventional technology]

In recent years, information display devices using light emitting diodes have been used in various places because they are easy to maintain.

In order to vary the display in this display device, light emitting diodes emitting light of different colors are grouped together to form one display dot, and a plurality of display dots are arranged to form a display surface. In order to display information on this display device, a display dot at a position corresponding to the display content is selected, and a luminescent color within the display dot is selected.

FIG. 3 shows an example of display dots. In the figure, the display dot D is composed of a red light emitting diode D1 and a yellow light emitting diode D2. In an information display device, such display dots are arranged vertically and horizontally in a matrix. Here, when current flows simultaneously through the red light emitting diode D1 and the yellow light emitting diode D2 of the display dot D, red and yellow light are emitted at the same time, and when viewed from a distance, the red and yellow are mixed and appear orange.

The majority of failures in light-emitting diodes are due to the wire bonding wire inside the light-emitting diode breaking due to the stress of expansion and contraction due to self-heating of the light-emitting diode, direct sunlight, cooling at night in winter, etc. . If the red light emitting diode DI is disconnected, the display dots change from orange to yellow due to only the yellow light emitting diode D2 being lit, which poses a serious problem in terms of visibility.

[Problem that the invention seeks to solve]

Therefore, it is possible to detect the disconnection of this light emitting diode, but this would require a current detection circuit to detect whether current flows through each of the red light emitting diode D1 and the yellow light emitting diode D2, making the device complicated and expensive. There was a problem.

Furthermore, if a disconnection of a light emitting diode is detected for each display dot and each luminescent color, the amount of data will be the product of the number of display dots and the number of luminescent colors, resulting in a large amount of data.
There is a problem in that the number of output lines of the current detection circuit increases, and the device for storing the data and notifying the operator becomes complicated and expensive.

Furthermore, there were problems as described below. For information display devices installed outdoors to display traffic information, etc.,
When the surroundings become dark at night, light bulb type information boards reduce the luminous intensity and dim to prevent halation, and in light bulb types, the voltage supplied to the light bulb is lowered to 172 volts during the day to dim. The method is common. In the case of light emitting diodes, the forward voltage of the light emitting diode is 2.2V per element.
Due to the high level of light, when the supply voltage is lowered to half of the daytime voltage, it becomes less than the forward voltage and does not turn on.As a result, it is difficult for the human eye to distinguish between light-emitting diodes when they are on and off due to the afterimage phenomenon. By repeating turning on and off at a high frequency (approximately 100 Hz or higher), shortening the lighting time and lengthening the off time, the lamp appears dark to the human eye. When this dimming is performed, the time of the current flowing through the light emitting diode is determined to be 1/20 of the period IQms of 100H2, based on the results of a visual experiment showing that a lighting rate of 1/20 is appropriate at night when continuous lighting is performed during the day. 20 500μ
It becomes s. It is difficult to collect current detection data for each luminescent color of all display dots in this short period of 500 μs.
When a device such as a microcomputer that performs processing in chronological order is used to collect data, a large display device cannot collect data for all displayed dots.

Note that a photocoupler is available as a means for detecting the current flowing through the light emitting diode, but this photocoupler is expensive and is not suitable for miniaturization such as IC.

[Means for solving problems]

In order to solve these problems, the present invention provides a detection circuit that detects the current flowing through the light emitting diode, a memory circuit that performs a memory operation to store the output signal of the detection circuit when current flows through the light emitting diode, and a memory circuit that stores the output signal of the detection circuit when current flows through the light emitting diode. A current flowing through a light-emitting diode includes an AND circuit in which the output of the memory circuit is connected to one input terminal of the AND circuit, and a decoder whose output is connected to the other input terminal of the AND circuit to control the output signal of the memory circuit. Detection data is collected for each display dot.

Further, the detection circuit is configured to detect the total value of the current flowing through the light emitting diodes for each display dot, and a control circuit is added to the above configuration to control power on/off for each light emitting diode with a different emission color. The current flowing through the light emitting diode is detected for each luminescent color of each display dot.

[Function] In the information display device according to the present invention, the number of output lines of the current detection circuit is reduced, and collection of current detection data of the light emitting diodes for each display dot and each luminescent color becomes easier in terms of time. The number of detection circuits that detect the current flowing through the circuit is reduced.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of an information display device according to the present invention, and FIG. 2 is a time chart showing the logical state of each part of the circuit shown in FIG.

In Figure 1, 1 is a control circuit, 2 is a solid device, 3 is a memory circuit, 4 is a decoder, 5.6 is an OR circuit, 7 is an AND circuit, El is a power supply, Q1 to Q4 are transistors, and D is a display. dot, DI is a red light emitting diode, D2 is a yellow light emitting diode, R1, R2 are resistors, TA-TI is a terminal, W
1 is an input line to the OR circuit 6, W2 is an output line from the decoder 4, and W3 is a telephone line.

In FIG. 2, (a) to (C) show the signals on terminals TA-TC, (d) and (e) show the signals on red light-emitting diode DI and yellow light-emitting diode D2, Tf
l~(jl indicates signals on terminals TH, TD, TE, TF, and TG.

In FIG. 1, the positive (+) side of the power source E1 is connected to the emitter of a transistor Q3, which turns on and off the power supplied to the red light emitting diode D1, and the emitter of a transistor Q4, which turns on and off the power supplied to the yellow light emitting diode D2. It is connected to the. A signal is input to the base of transistor Q3. When Q4 turns on, transistor Q
3. Power is supplied from the collector of Q4 to the anodes of the red light emitting diode DI and yellow light emitting diode D2 that constitute the display dot D through the limiting resistors R1 and R2. The cathodes of the red light emitting diode DI and the yellow light emitting diode D2 are connected to the base of a transistor Q2 of a common current detection circuit, and the emitter of the transistor Q2 is connected to the display dot D.
The emitter of the transistor Q1 is connected to the negative (-) side of the power source El. Therefore, the current flowing through the light emitting diodes Di and D2 also serves as the base current of the transistor Q2, and when the current flows, the transistor Q2 is turned on, and the transistor Q2 outputs a signal from its collector.

The control circuit 1 is composed of a microcomputer, etc., and outputs control signals to terminals TA, TB, TC, and a decoder 4. Terminal TA is connected to the base of transistor Q1 and controls whether or not display dot D is lit. The terminal TB is connected to the base of the transistor Q3, and controls the power on/off of the red light emitting diode DI, and the terminal TC is connected to the base of the transistor Q4, and controls the power on/off of the yellow light emitting diode D2. Also, terminal TB
, TC are both connected to the input side of the OR circuit 5, and the OR circuit 5
The output side of is connected to the terminal TD of the memory circuit 3. The output signal of the OR circuit 5 causes the input signal of the terminal TH of the storage circuit 5 to perform a storage operation.

The terminal TH of the memory circuit 3 is the transistor Q of the current detection circuit.
Since the memory circuit 3 is connected to the collector of the red light emitting diode DI or the yellow light emitting diode D2, the memory circuit 3 stores a signal that detects the current of the red light emitting diode DI or the yellow light emitting diode D2 based on the input signal to the terminal TD. The memory output signal of the memory circuit 3 is inputted from the terminal TE to one input point of the AND circuit 7, and the AND circuit 7
An output signal from a terminal TF of the decoder 4 is input to the other input point of the decoder 4, and a binary code signal from the control circuit 1 is input to the decoder 4.

The decoder 4 converts the binary code into a decimal code and outputs it to the terminal TF. The signal from the terminal TF is a control signal for the control circuit 1 to select and input the memory output signal of current detection, and the output signal of the AND circuit 7 is inputted to the OR circuit 6, and other signals of the OR circuit 6 are inputted. The output signal of the AND circuit for each display dot is input to the input line W1. By ORing the output signal of the AND circuit 7 with the OR circuit 6, the wiring to the terminal TG can be made common to display dots, and the number of wirings connected to the control circuit 1 can be reduced.

On the other hand, although it seems that the number of signals from the terminal TF increases, since the control circuit 1 can output the binary code to the decoder 4, the number of wires does not increase significantly. Although the OR circuit 6 is used here, the OR circuit 6 may be constructed by performing a wired OR on the output signal of the AND circuit 7.

Next, FIG. 2 will be explained. In the second interval TI, the red light emitting diode D1 and the yellow light emitting diode D2 are lit at the same time. In this section T1, the terminal T
A signal is output as logic "1" (Figure 2 (a))
, transistor Q1 is on. time t1 terminal TB
When the control signal is output from the TC as logic “1” (second
Figure (bl, (C1>, transistors Q3 and Q4 are respectively turned on. Power source E1 is applied to light emitting diodes DI and D2 via transistors Q3 and Q4 and limiting resistors R1 and R2, and light emitting diodes DI and D2 emit light. (Second
(dl, (e)), the current flowing through the light emitting diodes DI and D2 becomes the base current of the transistor Q2, and a logic "1" signal is input to the terminal TH of the memory circuit 3 (
Figure 2(f)). On the other hand, since the control signal is input to the terminal TD of the memory circuit 3 at that time (FIG. 2(g)),
The signal at the terminal TH is stored, and a continuous signal is output to the terminal TE (FIG. 2(h)).

Here, the time t1 is as short as 500 μs, but by detecting the current flowing through the light emitting diode during this time t1 and storing the signal, a pulse-like signal can be converted into a level-like signal. The time t1 can be shortened to the response speed of semiconductors such as the memory circuit 3. Therefore, control circuit 1
By outputting the control signal to the terminal TF, it is possible to input the storage output signal from the terminal TG without being constrained by time (Fig. 2 (il, fil),
A control signal is output from the decoder 4 to the AND circuit of each display dot, and current detection data of the light emitting diodes of all display dots can be collected in time series.

Next, section T2 in FIG. 2 is a red light emitting diode D.
This is to show a method of detecting whether or not current is flowing through the circuit. In section T2, unlike section T1, no control signal is output from terminal TC. Therefore, since transistor Q3 remains on and transistor Q4 remains off, current flows only through red light emitting diode D1 and that current is detected.

The section T3 is for showing a method of detecting whether or not current is flowing through the yellow light emitting diode D2. Section T3
, a control signal is output from the terminal TC, but no control signal is output from the terminal TB. Therefore, since transistor Q4 remains on and transistor Q3 remains off, current flows only through yellow light emitting diode D2 and that current is detected.

Section T2. As shown in T3, by providing a control circuit that controls the power supply for each emitted color and controlling the power supply of the light emitting diode for each emitted color, the current detection circuit of the light emitting diode is common to each emitted color. However, the current of the light emitting diode can be detected for each color of light emitted by each display dot, and the device can be made simple and inexpensive.

Section T4. T5 is red light emitting diode D1 due to disconnection.
This is to explain the current detection operation when power is not supplied to the circuit. In the interval T2 to T5, no current is applied to the light emitting diode on one side so that the light emitting diode on one side does not light up, but the time is 500μ.
Since the light is as short as s, it does not appear to the human eye that the light is turned off due to an afterimage phenomenon. Here, transistors Q3 and 04
can be used commonly for each display dot, so it is not complicated.

In this way, the control circuit 1 can collect data by receiving the current detection signal of the light emitting diode for each display dot and each light emitting color, but the amount of data is the product of the number of display dots and the number of light emitting colors. This results in a large amount. In addition, if you want to centrally manage the current detection data of the light emitting diodes, connect the telephone line W from the control circuit 1 to the terminal TI.
3 to the solid device 2, but if the amount of data is large, the transmission time will be longer and the data will be sent to the solid device 2 via
Therefore, the memory circuit that stores the data becomes enormous.

Therefore, there are two methods for obtaining the minimum amount of data for understanding the status of the information display device.

One method is as follows. This is a problem because one of the light emitting diodes emitting light of a different color is disconnected, and the display color of the display dots changes. In this case, the logical product of the current detection data of the light emitting diodes of different emission colors is calculated, and the result is used as the lighting data of the display dots.

Another method is as follows. This is a case where all of the light emitting diodes constituting the display dots are disconnected and display cannot be performed. In this case, the logical sum of current detection data of light emitting diodes of different emission colors is calculated, and the result is used as the lighting data of the display dots. There are two ways to obtain this logical sum: one is to process the data for each emitted color using the control circuit 1, and the other is to detect the current flowing through all the light emitting diodes of the display dots, as shown in section T1 in FIG. be.

Regardless of whether the logical product data or the logical sum data is obtained, it can be easily realized by the control circuit 1, and the amount of data can be reduced.

Next, there is a method for detecting the currents in the light emitting diodes DI and D2. By using the currents flowing in the light emitting diodes DI and D2 as the base current of the transistor Q2 in FIG. The current of the light emitting diode can be detected.

In the explanation of this embodiment, the light emitting colors of the light emitting diodes are explained as two colors, red and yellow, but other colors, single color, or three colors are also possible, and the number of light emitting diodes is also explained as two per display dot. However, the present invention is not limited to this number. Moreover, although the lighting time of the light emitting diode was described as 500 μs and the blinking frequency was 100 Hz, the present invention is not limited to this, and it goes without saying that the light emitting diode can be lit continuously during the day.

〔Effect of the invention〕

As explained above, the present invention controls the supply of power to the light emitting diode, collects detected data of the current flowing through the light emitting diode in a storage circuit for each display dot or for each luminescent color of each display dot, and stores the data in the storage circuit. By controlling the input of the output signal from the light emitting diode to the control circuit, there is no time constraint on collecting detected data, and the input line to the control circuit can be shared by all display dots, so the lighting time tl of the light emitting diode can be reduced. Even if it is short, detection data of the current flowing through the light emitting diode can be collected, and the number of detection signal wiring can be reduced.
This has the effect that the number of current detection circuits can be reduced, the amount of detection data can be reduced, and the detection circuit can be simplified.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of an information display device according to the present invention, FIG. 2 is a time chart for explaining the operation of the device, and FIG. 3 is an explanatory diagram showing display dots. DESCRIPTION OF SYMBOLS 1... Control circuit, 2... Solid device, 3... Memory circuit, 4... Decoder, 5.6... OR circuit, 7...
・AND circuit, El...power supply, D...display dot,
Dl...Red light emitting diode-F, D2...Yellow light emitting diode, Q1-Q5...Transistor, R1, R2
...Resistance, TA~Tl...terminal, Wl...input line, W2...output line, W3...telephone line.

Claims (4)

[Claims] (1) In an information display device in which display dots made up of a plurality of light emitting diodes of different light emitting colors are arranged in a matrix in the vertical and horizontal directions to display characters, etc. in a dotted manner, a detection circuit that detects the current flowing through the light emitting diodes; , a memory circuit that performs a memory operation to store the output signal of the detection circuit when current is applied to the light emitting diode, an AND circuit to which the output of the memory circuit is connected to one input terminal, and the other of the AND circuit. An information display device comprising: a decoder whose output is connected to an input terminal of the decoder for controlling an output signal of the memory circuit, and collecting detection data of a current flowing through the light emitting diode for each display dot. (2) The detection circuit is composed of a transistor, and this transistor uses the current flowing through the light emitting diode as a base current, and uses the collector signal as a current detection signal of the light emitting diode. information display device. (3) In an information display device in which display dots consisting of a plurality of light emitting diodes with different luminescent colors are arranged in a matrix in a vertical and horizontal manner, and characters etc. are displayed in a dotted manner, the total value of the current flowing through the light emitting diodes is displayed on the display dots. a detection circuit that performs detection at each time, a memory circuit that performs a memory operation to store the output signal of the detection circuit when current is applied to the light emitting diode, and an AND circuit in which the output of the memory circuit is connected to one input terminal thereof. and a decoder whose output is connected to the other input terminal of the AND circuit to control the output signal of the memory circuit, and a control circuit to control power on/off for each of the light emitting diodes of different light emitting colors. An information display device characterized in that a current flowing through a light emitting diode is detected for each luminescent color of each display dot. (4) A patent claim characterized in that the control circuit calculates the AND or OR of the current detection data of the light emitting diodes of each light emitting color of each display dot, and uses the result as the current detection data of each display dot. The information display device according to item 3 of the scope of the invention. (4) The detection circuit is composed of a transistor, and this transistor uses the current flowing through the light emitting diode as a base current, and uses the collector signal as a current detection signal of the light emitting diode. information display device.