JPH0743754Y2 - Driving device for dot matrix light emitting display device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device for a dot matrix light emitting display device.

2. Description of the Related Art A dot matrix light emitting display device (hereinafter referred to as "matrix display device") is a light emitting diode (hereinafter referred to as "LED").
, Etc.) and a driving device for selectively lighting the light emitting elements to obtain an arbitrary lighting display pattern. The display unit includes one to a plurality of display units, and data processing required for display lighting is performed using a control device (hereinafter, referred to as "CPU") including a computer or the like.

Such a conventional matrix display device (display unit 1
FIG. 6 shows an example of the configuration (only one is shown). In this matrix display device, the drive device 2'includes a shift register 21 that temporarily stores pattern display data and a latch circuit group that temporarily transfers the pattern display data stored in the shift register 21 in parallel. 22 and
Depending on the pattern display data from this latch circuit group 22,
16x16 LED dot matrix light emitting display 1'has a drive element (not shown) for selectively designating one matrix axis (pattern display side, Y axis in this example) corresponding to the LED to be displayed. The first driver circuit 23 and a 4-bit scanning signal for sequentially scanning the other matrix axis (scanning side, X axis in this example) of the dot matrix light emitting display 1'are received, and this scanning signal is sent to the light emitting display. A line decoder 24 'for converting into a scanning signal corresponding to the other matrix axis of 1
And a second driver circuit 25 which is driven by receiving a scanning signal from the line decoder 24 'and cooperates with the first driver circuit 23 to selectively energize and turn on the LED to be turned on.

In the configuration of the driving device 2'for the conventional matrix display device as shown in FIG. 6, the number of input lines from the outside to the line decoder 24 is increased (4 in the illustrated example), and the wiring is increased. There is a drawback that the structure becomes complicated. The inventor of the present invention has previously found that the above-mentioned drawbacks can be solved by making the drive device as shown in FIG. 7, for example (Japanese Patent Application No. 60-170339).

The configuration example of FIG. 7 will be briefly described. The drive device 2 ″ is a shift register that shifts and stores the pattern display data sent from the CPU in time series through the DATA terminal by the clock pulse sent from the CPU through the CLK terminal.
21, a latch circuit group 22 for temporarily transferring the pattern data stored in the shift register 21 in parallel in parallel by the latch pulse sent from the CPU through the LATCH terminal, and each of the latch circuit group 22. 16 depending on output
× 16 LED dot matrix The matrix axis on the pattern display side (Y
A first driver circuit 23 having a drive element (not shown, for example, a switching transistor or the like is adopted) for selectively designating an axis is provided. The pattern display data is the Y axis of the matrix axes, that is, Y1.
It is a 16-bit signal that specifies which of Y16 should be energized.

In the driving device 2 ″, the latch pulse is
It is also sent to the 4-bit hexadecimal counter 26, and the output of this counter 26 is further input to the line decoder 24.
The counter 26 is stepped up every time a latch pulse is input and outputs a 4-bit signal. The 4-bit signal thus output is further fed by the line decoder 24 to the scanning side matrix axis, That is, it is converted into a scanning signal for sequentially scanning X1 to X16 on the X axis, whereby the pattern display data and the scanning signal are synchronized. In addition, the counter 26 receives a reset pulse from the CPU through the RES terminal each time a latch pulse is input 16 times and the X-axis scanning is sequentially performed, that is, each time 16 types of pattern display data forming one word are sent. Has been sent. this is,
When the first pattern display data for one word is output from the first driver circuit 23, scanning on the X axis is performed by X1.
This is performed to correct the lighting drive of the dot-matrix light-emitting display 1 so that it is started from the axis when a malfunction due to noise or the like occurs.

Here, the configuration of the line decoder 24 is as shown in FIG. 8, and the outputs 26a to 26d of the counter 26 are input to 16 AND gates AND1 'to AND16', and the counter 26
Are sequentially converted into X-axis scanning signals according to the outputs 26a to 26d of. Reference numeral 25 denotes a second driver circuit having the same configuration as the first driver circuit 23, which is driven by the scanning signal output from the line decoder 24 and is driven by the first driver circuit 23.
In cooperation with the above, any LED of the dot matrix light emitting display 1 is selectively energized and lit.

The operation of the driving device 2 ″ having such a configuration will be described with reference to the time chart of FIG.

A multi-bit data signal a, which is pattern display data generated by a CPU (not shown) or the like, is sequentially sent to and accumulated in the shift register 21 by the clock pulse b. And
Each time the latch pulse d is sent, the pattern display data (in this example, a 16-bit signal designating the Y axis to be energized) accumulated in the shift register 21 is temporarily stored in the latch circuit group 22. The first driver circuit 23 is driven by the stored data, and the LED to be lit
The Y-axis corresponding to is designated.

At the same time, the latch pulse d is sent to the counter 26,
The value of the counter 26 is incremented. The output of the counter 26 becomes a 4-bit signal and is sent to the line decoder 24.
The line decoder 24 outputs the scanning signal f which drives the second driver circuit 25 by the output signal and sequentially scans the X axis.

Problems to be Solved by the Invention In each of the above matrix display devices, since the LEDs are lit by the dynamic drive method, each row and column of the matrix is lit up in a pulsed manner one after another in a very short time. Is erased, and by repeating it, the entire display pattern is made to appear as if it is continuously lit. Further, the ratio of the width of one cycle to the width of one lighting pulse is called a duty ratio.

By the way, in such dynamic drive lighting, if the Y axis is the pattern display side and the X axis is the scanning side, X
The duty ratio of each row on the axis side is 1 / (the number of dots on the X-axis), and the lighting time for one pulse is 1 / (scanning speed × the number of dots on the X-axis), and the LED for one row is lit for that time. However, since the lighting time is shorter than continuous lighting by the static drive method, the brightness of the LED will inevitably decrease.

Therefore, in order to obtain the desired brightness, a current exceeding the rated current is passed through each LED. For this reason, scanning stops for some reason and the LEDs in the same row of the matrix
Is continuously lit, for example, when the SCAN signal cannot be obtained from the SCAN terminal in the example of FIG. 6,
Alternatively, when the latch pulse d is no longer emitted in the example of FIG. 7 (see (d) of FIG. 9), one row of the X axis of the LED matrix (X2 axis in the example of FIG. 9). Only the LED will continue to light up, in other words, the current of several times the rated current will continue to flow through the LED of that row, and there is a problem that the LED of the dot matrix light emitting display body will be deteriorated or damaged. Occurs. Therefore, it has been desired to develop a driving device having a means for preventing the occurrence of the above problems as a driving device for a dot matrix light emitting display device of a dynamic drive system.

It is an object of the present invention to provide a driving device for a dot matrix light emitting display device by a dynamic drive method that can solve the above problems.

Means for Solving the Problems The present invention proposed to achieve the above object scans each row of a luminous element group arranged in a matrix in order by switching each row at the rising edge or the falling edge of a scan switching signal. , In a driving device that drives a dot matrix light emitting display device by a dynamic drive method by applying a display signal corresponding to the scanning row to each column during a scanning period of each row, triggering by rising or falling of a scan switching signal The monostable multivibrator that outputs a display permission signal that is active only for a period shorter than the scanning period of one row after the trigger is performed by the scan inhibition time and the display permission signal that this monostable multivibrator outputs are displayed. An energization prohibition circuit that prohibits energization to the light-emitting element group when inactive is provided. It is characterized by that.

During normal operation, the pulse of the scan switching signal surely rises or falls every scanning period of one row. Then, the monostable multivibrator is triggered by the scan switching signal to activate the display permission signal output from the vicinity of the start of the scanning period of one row for a certain period of time, and then returns it to the inactive state to end the scanning period. . Therefore, when the scanning period starts, first, the display permission signal output from the monostable multivibrator becomes active, so that the luminous element group of the scanning row is turned on according to the display signal applied to each column. When the display permission signal is switched to inactive, the energization prohibition circuit prohibits energization to these light-emitting element groups, so that the lighting is forcibly stopped, and then the scanning prohibition time elapses and the scanning period is stopped. Ends. Then, this operation is repeated every scanning period of each row.

As a result, during normal operation, the driving device of the present invention is lit up and displayed for a certain period set in the monostable multivibrator from the start of each scanning period, and thereafter lights up until the next scanning period starts. Since the display is stopped, when driving the dot matrix light emitting display device by the dynamic drive method, it becomes possible to provide a scan inhibition time for preventing the overlapping of the lighting displays of the adjacent rows when switching the scan. .

In addition, if an abnormal situation occurs in which the scan switching signal does not change even after the scan period ends, the monostable multivibrator will not be triggered by this scan switch signal, so it will be inactive at the end of the last scan period. The display permission signal is continuously output. Then, since the state in which the energization to the light emitting element group by the energization prohibiting circuit is prohibited is maintained, the lighting display of the light emitting element group remains stopped.

As a result, in the driving device of the present invention, the energization prohibition circuit forcibly stops the lighting display of the light emitting element groups in an abnormal state, so that the dot matrix light emitting display apparatus continues to turn on the light emitting element groups in the same row. Will be able to prevent.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. The present embodiment is configured by providing the protection circuit 20 in the driving device shown in FIG. 7 which is designed to change the pattern display data and scan the scanning signal in synchronization with the latch pulse. is there.

The circuit configuration of the line decoder 24 'is as shown in FIG. 2 and is substantially the same as that of the line decoder 24 of FIG. 7 described above, but the inhibit terminal INH is provided in this embodiment. Since the output of the multivibrator MM2 is input to the terminal INH, when the output of the multivibrator MM2 is at the “L” level, the output of one of the AND gates AND1 to AND16 that matches the output of the counter 26. Becomes the “H” level, the scanning signal is sent from the second driver circuit 25, and the dot matrix light emitting display 1 is turned on. However, when the output becomes "H" level, all the outputs of the AND gates AND1 to AND16 become "L" level. Therefore, the scanning signal is not output from the second driver circuit 25, and the dot matrix light emitting display 1 is prohibited from lighting.

As shown in FIG. 3, the protection circuit 20 is composed of a monostable multivibrator MM3 in one stage, and has an external resistor Rx3.
And the time constant tW3 is determined by the capacitor Cx3. The A input terminal AIN of the multivibrator MM3 is connected to the latch pulse supply line 27, and the B input terminal BIN and the clear terminal CD are connected to the DC power supply Vcc and held at "H" level.

The time constant tW3 of the multivibrator MM3 is set to be shorter than the pulse interval of the latch pulse (that is, the scanning period of one row) by a predetermined time. As shown in FIG. 4, the multivibrator MM3 inverts its output to the “H” level when the time corresponding to the time constant tW3 has elapsed after being triggered by the input of the latch pulse, so that the “H” level is set. Until the time is reversed, the inhibit signal becomes "L" during the time and scanning of the X axis is permitted, but the output is "H".
, That is, the time Ti until the next latch pulse is input to the multivibrator MM3 is the scan inhibition time. The scanning prohibition time Ti is a so-called when the lighting of each row is moved and scanned by the dynamic drive method, the lighting display of the light emitting element groups in the adjacent rows overlap each other due to an afterimage phenomenon and make the display pattern difficult to see. This is done to prevent the bleeding phenomenon.

In the above-described embodiment, the output of the line decoder is prohibited by the output of the protection circuit. However, for example, the power supply circuit of the second driver circuit 25 is opened by the output of the protection circuit and scanning is performed by the circuit 25. It is possible to obtain the same effect as that of each of the above-described embodiments by using other appropriate configurations such as not generating a signal.

Further, the drive device to which the present invention is applied is not limited to the drive device having the configuration shown in FIG. 1 as in each of the above-described embodiments, but the protection circuit 2 is provided in the matrix display device 2'shown in FIG. It goes without saying that the case of configuring the drive device 2 as shown in FIG. 5 is also widely included.

Although the row scanning mode has been described in the above embodiment, the viewpoint may be changed to a column scanning mode, and such a mode is also included in the present invention.

Effect of the Invention As is apparent from the above description, according to the present invention, in the dot matrix light emitting display device by the dynamic drive method, it is possible to prevent the lighting display of adjacent rows from overlapping each other during each scanning period during normal operation. Protection for preventing the LEDs in the same row of the matrix from continuing to light up even if the scanning of the matrix light-emitting display is stopped due to some reason A drive device having a function can be provided.

[Brief description of drawings]

1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is a circuit diagram of its line decoder, FIG. 3 is a circuit diagram of its protection circuit,
FIG. 4 is a time chart thereof, FIG. 5 is a circuit diagram of another embodiment, FIG. 6 is a circuit diagram of a dot matrix display device of a conventional example, FIG. 7 is a circuit diagram of an improved example thereof, and FIG. A circuit diagram of a line decoder used for that purpose, and FIG. 9 are time charts for explaining the operation of the dot matrix display device shown in FIG. 1 ... Dot matrix light emitting display, 2 ... Driving device,
20 …… Protection circuit, MM3 …… Monostable multivibrator, 2
4 '... Line decoder

Claims (1)

[Scope of utility model registration request] 1. Each row of a luminous element group arranged in a matrix is sequentially switched at each rising or falling of a scan switching signal, and a display signal corresponding to the scanning row is displayed within a scanning period of each row. In a drive device that drives a dot matrix light emitting display device by a dynamic drive method by applying it to each column, it is triggered by the rising or falling of a scan switching signal, and is longer than the scanning period of one row after this trigger is performed. A monostable multivibrator that outputs a display permission signal that is active only for a short period of the scan inhibition time, and prohibits energization to the light emitter element group when the display permission signal output by this monostable multivibrator is inactive A dot matrix light emitting display device characterized in that an energization prohibition circuit is provided. Drive.