JPH10254385A - Led dot matrix display device and gradation display method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a high gradation display with high display quality and to delay a read-out speed of the data in a full color LED dot matrix display unit. SOLUTION: The display cycle of one picture is divided into two parts, and data comparison for performing the gradation display is performed using different counters at respective cycles. That is, a comparison counter 4a performing an even-jumped count according to the number of gradation and the comparison counter 4b performing an odd-jumped count are provided, and the output data of these counters 4a, 4b are switched at every display cycle by a switch circuit 7, and are compared with the display data read out from a memory 1 by a comparison circuit 5, and the line data are inputted to an LED dot matrix unit 6, and an LED is lighted.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an LED dot matrix display device for displaying various kinds of information, advertisements, etc., and more particularly to an LED dot matrix display device for performing gradation display by a full-color LED unit and a gradation display method thereof. .

[0002]

2. Description of the Related Art FIG. 4 is a diagram showing a line structure of an LED dot matrix unit in which LEDs are incorporated in a dot matrix, and shows a case of 16 × 16 dots.

[0003] In the dynamic lighting method in such an LED dot matrix unit, when the duty ratio is 1/16 as shown in FIG. 4, first, data of the segment lines (1 to 16) is input, and the common line (1) is inputted.
Is turned on, and then the same operation is performed on the common line (2). When the common line (16) is reached, the operation returns to the common line (1). Thus, one screen is displayed.

On the other hand, in a full-color LED dot matrix unit, gradation display is performed by a gradation display control circuit as shown in FIG. That is, when the input data is 8 bits (0 to 255) and the dynamic lighting operation of the matrix unit in FIG.
When the operation is added, for example, the lighting time of the common line (1) in FIG.
The segment data is input to the LED dot matrix unit 6 through the LED and the common line (1) is turned on.

At this time, when the comparison data in the comparison circuit 5 is larger than the value from the comparison counter 4, the LED is turned on. Next, the value of the comparison counter 4 increases by 1, the 8-bit data of the same segment line is read again, and the common line (1) is similarly turned on through the comparison circuit 5.

Then, the same operation as above is repeatedly performed,
When the comparison counter 4 finishes increasing to 255, it moves to the common line (2) and performs the same operation. This operation is further performed up to the common line (16), and the display is performed in one cycle.

In this way, by performing data rewriting 256 times in one segment line of one screen through the comparison circuit 5, gradation display can be realized.

In FIG. 5, reference numeral 1 denotes a memory for storing external input data, 2 denotes a read circuit for reading the data, and 3 denotes an OSC circuit for providing a data read frequency.

Here, considering the display time of one screen, 1
It is known that a frequency that does not cause human eyes to flicker as a display on a screen is 60 Hz or more. Also, LE based on CRT output of personal computer etc.
Considering that the D unit is displayed, the cycle of the input data is 60 Hz.

However, in the dynamic lighting display of the LED dot matrix unit, the frequency is doubled to 120 Hz.
It is said that a display with less flicker can be obtained by making a round of the common line at about the same frequency.

Considering the switching time at one screen of 120 Hz, if the display time of one screen of the LED dot matrix unit is 120 Hz = 8.3 msec, the common line switching frequency at each duty ratio is one screen frequency / Table 1 shows the number of common lines.

[0012]

[Table 1]

The common line switching time at each duty ratio with respect to the input data period is as shown in FIG. As shown in FIG. 6, since the input data cycle is 60 Hz, when the screen display frequency is set to 120 Hz, 2
The display of the cycle is performed.

Now, during these common line switching periods, the 256 gradation PWM is passed through a circuit as shown in FIG.
Is completed, the readout frequency of the display data by the OSC circuit is the common line switching frequency / 256 *
From the number of transfer dots, about 8 MHz = 128 nsec.

That is, in order to complete the PWM of 256 gradations, the display data is rewritten and displayed at the transfer rate of 8 MHz.

When considered in this way, the data reading speed inside the unit is high, and there are problems such as noise. Therefore, it is desirable that the data reading speed be low if possible.

[0017]

As described above, as described above, the LED
In the dynamic lighting display in the dot matrix unit, it is desirable to make the display time of one screen short so as not to make the human eyes feel flicker and to improve the display quality.
When the WM is realized, it is necessary to increase the data reading speed inside the unit, and there is a problem that noise occurs.

The present invention has been made in view of the above-mentioned problems, and can reduce the speed of reading display data without deteriorating the display quality and reduce the noise and the like. An object is to provide a dot matrix display device and a gradation display method thereof.

[0019]

According to the present invention, there is provided an LED dot matrix display device comprising: a memory for storing display data; a counter for performing a counting operation according to the number of gradations; A comparison circuit for comparing the read data and lighting the LEDs of the LED dot matrix, wherein the counter is divided into a plurality of counters that count at different jump numbers, and provided.
These counters are sequentially switched in a display cycle and input to the comparison circuit.

In the above display device, the counter is divided into a counter for counting even-numbered steps and a counter for counting odd-numbered steps, and these counters are switched every cycle in two display cycles. It was done.

In the gradation display method for an LED dot matrix display device according to the present invention, a display cycle is divided into a plurality of cycles, and in each cycle, output data of a counter which counts at a different jump number and a display read out from a memory. Compare the data with the LED dot matrix LED
Is turned on.

[0022]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. In this embodiment, the reading speed of display data is reduced, 256 gray scale display is realized, and an LED dot matrix unit is used. 1 in dynamic lighting
3 shows a configuration of a full-color gradation display control circuit capable of maintaining a screen cycle at 120 Hz.

In FIG. 1, 1 is an externally input 8
A memory for storing bit display data, a read circuit for reading the display data, an OSC circuit,
Reference numerals 4a and 4b denote comparison counters which perform a counting operation according to the number of gradations of 256. The comparison counter 4a counts even-number steps, and the comparison counter 4b counts odd-number steps.

Reference numeral 5 denotes a comparison circuit for comparing the output data of the counters 4a and 4b with the data read from the memory 1 to turn on the LEDs of the LED dot matrix unit 6, and 7 controls the counters 4a and 4b in a display cycle. A switching circuit that switches and outputs the output data to the comparison circuit 5.

As described above, if one screen display is set to 120 Hz, two cycles can be displayed with respect to the input data cycle. Further, if the number of gray scales in one cycle of the common line switching period is 128, the data reading speed can be reduced to half. As means for realizing 256 gradations at half the reading speed,
The circuit scheme of FIG. 1 is shown.

That is, the LE of FIG.
When lighting the D dot matrix unit, first,
The segment data of the common line 1 is read and input to the comparison circuit 5. At this time, an even-numbered counter 4a is selected as the comparison counter, the output data of the counter 4a is compared with the segment data, and the line data is input to the LED dot matrix unit 6 through the comparison circuit 5, and the common line 1 Lights up.

Next, the even-numbered comparison counter 4a is incremented by 2, and the data of the same segment line is read out again and input to the comparison circuit 5, and the common line 1 is similarly turned on through this comparison circuit 5. Subsequently, the same operation is repeatedly performed, and the even-numbered comparison counter jumps by two (0, 2, 2).
After counting up to 254 at 4), the process moves to common line 2 and the same operation is performed.

Further, the same operation as described above is performed on the common line 1.
Perform up to 6 and go around once. Then, the operations up to this point are executed at 120 Hz in the first cycle.

Next, the odd counter 4b is selected as the comparison counter, and the same operation is performed at 120 Hz in the second cycle. The process is performed until the odd-numbered comparison counter 4b jumps by two (1, 3, 5,...) And counts up to 255. In this manner, by displaying different 128 gradations in one screen display period of 120 Hz,
Display of 256 gradations can be realized.

At this time, since one screen is at 120 Hz, the display quality of the LED dot matrix unit 6 is improved.

Further, the data reading speed is 4 times the common line switching frequency / 128 * the number of transferred dots.
MHz, which can be reduced to half of the conventional method. Therefore, noise and the like are reduced. The display time at this time is summarized as shown in FIG.

Next, another embodiment of the present invention will be described. As described above, the higher the frequency of one round of the common line in the dynamic lighting of the LED dot matrix unit, the smaller the flicker of display and the higher the display quality. Therefore, in the above-described embodiment, a display with good division is performed at 120 Hz for a data input cycle of 60 Hz.

However, data may be input on the basis of one screen at 30 Hz, for example, as in a standard television signal of the NTSC system. In this case, the display cycle can be divided into four to reduce the data reading speed. .

That is, in order to lengthen the PWM timing, 64 gradations are controlled in a V-Sync (vertical synchronization signal) period. At this time, as described above, the display frame is 4 Hz at 120 Hz with respect to the input frame of 30 Hz.
Because of the cycle, there are 64 gradations, and 25 in 4 cycles.
Six gradation display is possible. FIG. 3 is a diagram showing the display time at this time, and 33.3 msec at an input frame of 30 Hz.
c.

The data comparison in each gradation frame is performed by providing four comparison counters and skipping every four counts.
56 gradation PWM is realized. Further, by setting 64 gradations in each display frame, the data transfer frequency becomes 2 MHz. Table 2 summarizes the results at each duty ratio at this time (PWM = H-Sync / 64 gradations).

[0036]

[Table 2]

[0037]

As described above, according to the present invention, the LED
In the dynamic lighting of the dot matrix unit, the display cycle is divided into a plurality of cycles, and in each cycle, data comparison for gray scale display is performed by counters that perform different counting operations. This has the effect of reducing the data reading speed and reducing noise and the like.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a display time in one embodiment.

FIG. 3 is an explanatory diagram showing a display time in another embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a line structure of an LED dot matrix unit.

FIG. 5 is a block diagram showing a conventional example.

6 is an explanatory diagram showing a display time in the circuit of FIG.

[Explanation of symbols]

 Reference Signs List 1 memory 2 readout circuit 3 OSC circuit 4a comparison counter 4b comparison counter 5 comparison circuit 6 LED dot matrix unit

Claims (3)

[Claims] 1. A memory for storing display data, a counter for performing a count operation according to the number of gradations, and comparing the output data of the counter with the data read from the memory to turn on the LEDs of the LED dot matrix. An LED dot matrix, wherein the counter is divided into a plurality of counters that count at different jump numbers, and these counters are sequentially switched in a display cycle and input to the comparison circuit. Display device. 2. The counter according to claim 1, wherein the counter is divided into a counter for counting even-numbered steps and a counter for counting odd-numbered steps, and these counters are switched every cycle in two display cycles. 2. The LED dot matrix display device according to 1. 3. A gradation display method for LED dot matrix display, wherein a display cycle is divided into a plurality of cycles, and in each cycle, output data of a counter which counts at different jump numbers and display data read from a memory are compared. A method of displaying a gradation of an LED dot matrix display device, wherein LEDs of an LED dot matrix are turned on.