JP2917876B2 - Display method of LED display - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display method of an LED display for adjusting the brightness by adjusting the light emission time of a plurality of LEDs.

[0002]

2. Description of the Related Art An LED display which displays an image by arranging a plurality of LEDs vertically and horizontally can adjust the brightness of a spot by changing the light emission time of each LED. An image can be displayed by modulating the time during which the LED emits light with the gradation data.

[0003] This method uses red, green, blue, or RGB.
Are arranged close to each other to form one picture element, and a large number of picture elements are arranged vertically and horizontally to realize a full-color LED display unit. This LED display unit can display one picture element in multi-color by adjusting the light emission luminance of three kinds of LEDs whose emission colors are red, green and blue. The LED display unit of this structure has red, green and blue L
The emission color of the ED is controlled by the gradation data to adjust the emission color and brightness.

[0004] The LED display unit having this structure includes a lighting circuit that blinks the LED for a time corresponding to the grayscale data of the digital signal. Lighting circuit is LED
Flashes at a frequency of 60 to prevent flickering.
Hz, for example, about 100 Hz.
Assuming a frequency of 100 Hz, the LED flashes 100 times per second. This lighting circuit adjusts the light emission luminance by adjusting the LED lighting time based on the gradation data. The longer the lighting time of one LED, the brighter the eyes, and the shorter the lighting time, the darker the eyes.

In an LED display in which a large number of LEDs are arranged vertically and horizontally, the LEDs are divided into a plurality of sets, and the divided L
A dynamic lighting method for lighting the ED in a time-sharing manner;
There is a static lighting method in which the ED is not divided. In the dynamic lighting, the LEDs are divided into a plurality of groups and lighted sequentially, so that a lighting circuit can be simplified. For example, an LED display in which LEDs are arranged in 16 rows × 16 columns can be turned on in order by dividing each column into one set and dividing the whole into 16 parts. In this method, all the LEDs can be turned on by 16 sets of lighting circuits.

A 16-row × 16-column LED display is
In the dynamic lighting that is divided into 16 columns, for example, if one image is displayed at 16 msec (frequency is 60 Hz), the display time of one column is 1 msec. That is, the light emission luminance of one row of LEDs is controlled by controlling the lighting time during 1 msec to the gradation data. In this specification, one cycle of turning on the LED in this manner is defined as a luminance modulation frame cycle. In the above example, the luminance modulation frame period is 1 msec. During the luminance modulation frame period of 1 msec, the lighting time of the LED is controlled by the gradation data to adjust the light emission luminance of the LED. The brightest LED is turned on for about 1 msec. By dividing the luminance modulation frame period into 256 gradations (8 bits), the light emission luminance of the LED can be adjusted to 256 gradations.

The lighting time of the LED is determined by gradation data input to the lighting circuit. To achieve this,
The lighting circuit compares the input gradation data with a gradation control clock. FIG. 1 shows the time during which the lighting circuit turns on the LED. In this figure, the value of the gradation data is represented by the digital value “1”.
2 ". The gradation data of the digital value is a numerical value from 0 to 255 in the case of an 8-bit digital signal, for example. The LED starts at the beginning of the luminance modulation frame period,
For example, it is turned on by the first input gradation control clock after reset. Thereafter, the count value of the tone control clock that is successively input is changed to “12” of the tone data.
When the count number of the inputted gradation control clock reaches “12” which is gradation data, the LED is turned off. The lighting circuit outputs a pulse width from the first gradation control clock to the input of the twelfth gradation control clock, and lights the LED with this pulse.

[0008]

According to this method, the LED is turned on for a time proportional to the digital value of the gradation data in the luminance modulation frame period. Since the LED is turned on for a time proportional to the gradation data, the LED emits light with a luminance proportional to the gradation data. However, such a method of causing the LED to emit light at a luminance proportional to the gradation data cannot be used in any environment to display an LED display in an ideal state. For example, an LED display used in a very bright place has a drawback that the screen is too dark, and an LED display used in a dark place has a drawback that the screen is too bright.

To make the LED emit light with the optimum brightness for the usage environment, the gradation data can be corrected. For example, by correcting the gradation data with a specific function using a microcomputer or the like, the LED can emit light in an optimal state. However, the method of correcting the gradation data may lower the luminance resolution. For example,
When the 8-bit gradation data is corrected, there is a disadvantage that the gradation data for substantially causing the LED to emit light is reduced to 6 bits or the like. This is because the corrected gradation data is also 8 bits. The corrected gradation data can be converted from 8 bits to 12 to 16 bits to prevent a decrease in the resolution of the gradation data. However, if the number of bits is increased, the subsequent processing circuit becomes complicated.

The present invention has been developed with the object of solving this drawback. An important object of the present invention is to adjust the period of the gradation control clock instead of correcting the gradation data. An object of the present invention is to provide a display method of an LED display that can emit an LED with ideal luminance.

[0011]

According to the display method of the LED display of the present invention, the LED is turned on and off as described below to achieve the above-mentioned object. The LED adjusts the light emission luminance by controlling the lighting time in the luminance modulation frame cycle with the gradation data. The LED is turned on at the beginning of the luminance modulation frame period. The lit LED compares the gradation control clocks that are successively input with the gradation data of the digital signal by the lighting circuit in the luminance modulation frame cycle, and counts the count value of the input gradation control clocks. When the count reaches the key data, the LED is turned off.

Further, in the display method of the LED display according to the present invention, the number of gradation control clocks in one luminance modulation frame period is set to be the same or substantially the same, and the dividing ratio memory is stored in the first half and the second half of the luminance modulation frame period. , Gradation system
Stores frequency division ratio using count number of control clock as address
And the dividing ratio output from the dividing ratio memory is
Select based on the data from the brightness sensor and
Outputs a gradation control clock with a period that is an integral multiple of the clock period
The period of the gradation control clock is initially long and gradually
Shorter or initially shorter and progressively shorter
The lighting period of the LED is adjusted for the same grayscale data by changing the period so that is longer .

FIG. 2 shows the principle diagram. FIG. 1 shows a conventional L
The display method of the ED display will be described. In the method of FIG. 1, the period of the gradation control clock is the same, but (2) and (3) of FIG.
In the method of the present invention, the period of the gradation control clock changes with time. In FIG. 2B, the period of the grayscale control clock at the beginning of the luminance modulation frame period is short and gradually longer. In (3) of FIG. 2, the period of the first gradation control clock in the luminance modulation frame period is long and gradually shortened. For example, if the digital value of the gradation data is “1”
2 ", the LED for adjusting the period of the gradation control clock is turned on and turned off up to point B as shown in (2) of FIG. 2, but the period of the gradation control clock is ( When the adjustment is performed as in 3), the LED is turned on to the point C and turned off.
That is, even if the digital value of the gradation data is the same “12”, the light emission time is shorter than that of the gradation control clock of (1) if the period of the gradation control clock is the period of (2) in FIG. ,
If the gradation control clock is (3) in FIG. 2, the light emission time will be long.

FIG. 3 is a graph showing the lighting time of the LED with respect to the gradation data. In this drawing, a straight line A causes the LED to emit light in a time proportional to the digital value of the gradation data. That is, a conventional method of causing the LED to emit light without changing the cycle of the gradation control clock will be described. Curve B corrects the light emission time of the LED to be shorter than the digital value of the gradation data. In particular, the light emission time of the LED is corrected to be short in a low luminance region. In order to perform such correction, the period of the gradation control clock is initially shortened and gradually increased as shown in FIG. The curve C in FIG. 3 corrects the emission time of the LED longer than the digital value of the gradation data. Particularly, in the low light emission region, the light emission time of the LED is lengthened to emit light brightly. In order to emit light in this manner, the period of the gray scale control clock is first increased and gradually reduced as shown in (3) of FIG.

In the display method of the LED display according to the present invention, in the luminance modulation frame period, the period of the gradation control clock is changed between the first and second periods, but the number of gradation control clocks in the luminance modulation frame period is not changed. For example, when the gradation data is an 8-bit digital signal, the number of gradation control clocks in the luminance modulation frame cycle is set to 256. Therefore, as shown in FIG. 2 (2), when the period of the gradation control clock is shortened at the beginning of the luminance modulation frame period, it is lengthened at the end, and the number of gradation control clocks in the luminance modulation frame period To 256
Align with Since the number of gradation control clocks in the luminance modulation frame period is the same, the luminance at which the LED emits the maximum light with the gradation data does not change.

In FIG. 3, the method of emitting light by correcting the gradation data as shown by the curve B is suitable, for example, when displaying an LED display in a dark place. This is because when the gradation data is bright, the light emission luminance of the LED is darkened. Conversely, the light emitting method indicated by the curve C is suitable for displaying an LED display in a bright place. Even when the gradation data is dark, it is brightened and LE
This is because D emits light.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. However, the embodiments described below exemplify an LED display unit for embodying the technical idea of the present invention, and the present invention does not specify the LED display unit as follows.

FIG. 4 shows a lighting circuit 1 which emits light by modulating the brightness of an LED with gradation data. This circuit includes a comparator 2 to which gradation data of a digital signal and a gradation control clock are input, and a pulse to output a pulse having a time width for causing an LED to emit light when an output of the comparator 2 and a reset signal are input. An output circuit 3 and a gradation control clock generation circuit 4 for inputting a gradation control clock whose cycle is adjusted to the comparator 2 are provided.

The comparator 2 compares the digital value of the inputted gradation data with the count value of the gradation control clock,
When the count value of the gradation control clock becomes equal to the gradation data, a light-off pulse for turning off the LED is output.
If the gradation data is an 8-bit digital signal, 0 to 0
255 gradation data is input. Therefore,
The comparator 2 outputs a light-off pulse signal when a grayscale control clock of 0 to 255 counts equal to the grayscale data is input. When the reset signal is input, the comparator 2 resets the count value of the gradation control clock.

The pulse output circuit 3 receives the reset signal and the light-off pulse, and outputs an on-off pulse at a time interval from the input of the reset signal to the input of the light-off pulse. ON / OFF pulse is LED driver 5
Is input to The driver 5 turns on the LED at the time interval of the on / off pulse.

FIG. 5 shows the gradation control clock generation circuit 4. The gradation control clock generation circuit 4 shown in the figure includes a programmable divider 4A for dividing an input reference clock by a division ratio controlled by a division ratio memory 4C, and a counter 4B for counting the output of the programmable divider 4A. And a frequency division ratio memory 4C storing a frequency division ratio using the count value input from the counter 4B as an address.
And

The programmable divider 4A divides the input reference clock and outputs a gray scale control clock having a cycle that is an integral multiple of the reference clock cycle. For example, when the input reference clock is divided into 周, the programmable divider 4A outputs a gradation control clock having a cycle twice as long as the reference clock. The reference clock of the programmable divider 4A is set equal to the minimum cycle of the gray scale control clock, or set to an integral number of the minimum cycle of the gray scale control clock. Programmable divider 4A
Adjusts the cycle of the grayscale control clock at a ratio of dividing the reference clock. The ratio at which the programmable divider 4A divides the reference clock is stored in the division ratio memory 4C.

The frequency division ratio memory 4C stores the frequency division ratio using the count number of the gradation control clock output from the gradation control clock generation circuit 4 as an address. For example, as shown in FIG. 2 (2), in order to output a gradation control clock in which the initial period is short and the period is gradually increased, the frequency division ratio memory 4C requires the count value output from the counter 4B. In other words, as the address of the dividing ratio memory 4C increases, for example, 1/2, 1/3, 1/4, 1/5, 1/6,.
A numerical value for frequency division such as 1 / n is stored as a frequency division ratio of one group. Conversely, as shown by (3) in FIG. 2, when outputting a gradation control clock whose period is gradually shortened, the frequency division ratio is increased to 1 / n · ..1 / 6, 1/5, 1 /
Numerical values of 4, 1/3 and 1/2 are stored as a group of division ratios. The dividing ratio memory 4C stores the dividing ratio of a plurality of groups, and the dividing ratio of each group to be stored is switched by input correction data. The division ratio memory 4C stores the division ratios of a plurality of groups in which the number of gradation control clocks in the luminance modulation frame period is constant and the division ratio is changed by the correction data.

The correction data is, for example, data such as the brightness of the surroundings on which the LED display is displayed. As the brightness correction data, the frequency division ratio stored in the frequency division ratio memory 4C is selected, and the lighting time of the LED with respect to the gradation data is changed as shown in (2) and (3) of FIG. When the periphery of the LED display is bright, the frequency division ratio stored in the frequency division ratio memory 4C is set as a group whose period is initially longer and gradually becomes shorter. Conversely, when the periphery of the LED display is dark, the frequency division ratio stored in the frequency division ratio memory 4C is switched to a group having a shorter cycle and a longer cycle.

According to the display method of the present invention, the correction data is
Do not specify the brightness around the D display. The correction data can also be the type of video and the display time. When the type of video is the correction data, for a video that is dark as a whole, a group having a frequency division ratio shown in (3) of FIG. 2 is selected. Then, the gradation data is corrected as shown by the curve C in FIG. 3, and the light emission time of the LED can be made longer than the standard to make the image brighter. On the contrary, the bright image as a whole is shown in (2) of FIG.
Select the group of the dividing ratio indicated by. Then, the gradation data is corrected as shown by the curve B in FIG. 3, and the light emission time of the LED is made shorter than the standard, so that the shading of the image can be made clear and easy to see.

FIG. 6 shows an overall circuit diagram of an apparatus used for the display method of the LED display of the present invention. The LED display device of this circuit diagram includes a computer 6 connected to a source of video data such as a VTR 14, a monitor television 7 connected to the computer 6,
The video display controller 8 converts an output of the computer 6 into a signal for LED display, and a plurality of LED units 9 connected to the video display controller 8.

The computer 6 outputs a video signal, a reference clock, and a reset signal for determining a luminance modulation frame period to the video display controller 8. The video signal outputs an image to the video display controller 8 at a frame frequency of 60 to 160 Hz, for example, at a rate of one per 1/60 to 1/160 second. The computer 6 transmits the RGB video signals to the video display controller 8 in parallel. The reference clock is determined to have a short cycle that is 1 / integer of the gradation control clock. The period of the reset signal is determined to be a luminance modulation frame period in which the LED is adjusted to, for example, 8 bits and 256 levels of brightness to be lit once. The reference clock and the reset signal can be generated by the video display controller 8 without being generated by the computer 6.

In the apparatus shown in FIG. 6, a brightness sensor 10 is connected to a computer 6. The brightness sensor 10 is an LED
Detects the brightness of the surroundings displaying the unit 9 and turns on the LED
And outputs correction data for controlling the light emission luminance of. The correction data is input to the gradation control clock generation circuit 4 of the video display controller 8 via the computer 6. The correction data adjusts the cycle of the gradation control clock output from the gradation control clock generation circuit 4 to control the light emission luminance of the LED. The luminance sensor 10 can be connected to the video display controller 8 instead of being connected to the computer 6 and directly input correction data to the video display controller 8. Further, the computer 6
Correction data for specifying the type of image or the average luminance or the like input from the TR 14 can be input to the image display controller 8 to control the cycle of the gradation control clock.

The video display controller 8 has an A / D converter 11 and a gradation control clock generation circuit 4 built therein. The A / D converter 11 converts the RGB video signal output from the computer 6 into, for example, gradation data that is an 8-bit digital signal. Although not shown, three sets of A / D converters 11 are provided. This is for converting the RGB video signal into a digital signal by performing parallel processing. However, the A / D converter 11 having a high conversion speed has the following problem.
RGB video signals can be sequentially converted to digital signals in pairs. The gradation control clock generation circuit 4 converts a reference clock output from the computer 6 into a gradation control clock.

One or three sets of gradation control clock generation circuits 4 are provided. One set of gradation control clock generation circuits adjusts the lighting times of the RGB LEDs together as the same group. RG by one set of gradation control clock generation circuits
The method of controlling the lighting time of the LED B has a feature that the circuit can be simplified. The three sets of gradation control clock generation circuits classify the red, green, and blue LEDs into three groups,
There is a feature that a GB LED can be controlled to an optimum light emission luminance. The three sets of gradation control clock generation circuits are provided, for example, for a blue or red LE with low luminosity in a region where light emission luminance is low.
The lighting time of D can be made longer than that of the green LED.

The gradation data converted into a digital signal by the A / D converter 11 is transmitted to the LED unit 9 together with an address for specifying an LED to emit light. RG
A gradation control clock and a reset signal are transmitted to the LED unit 9 together with the B gradation data.

The LED unit 9 is, as shown in FIG.
Frame memory 12 for storing gradation data of one screen
A comparator 2 that compares the grayscale data output from the frame memory 12 with a grayscale control clock, a pulse output circuit 3 that outputs a pulse for turning on an LED from the output of the comparator 2, and a pulse output circuit 3. A driver 5 for turning on an LED with an output pulse and an address counter (not shown) for specifying an address of gradation data stored in the frame memory 12 are provided.

The frame memory 12 temporarily stores one frame of gradation data output from the video display controller 8. For example, the video display controller 8
Assuming that RGB gradation data is output as an 8-bit digital signal, the frame memory 12 stores the light emission luminance of the RGB LED for displaying one picture element as an 8-bit × 3 set (24-bit) digital signal. I do. This is because each of the RGB LEDs for displaying one picture element is lit with 8-bit gradation data. LED unit 9
However, assuming that 16 pixels of RGB LEDs are arranged vertically and horizontally, the frame memory 12 stores a digital signal of 24 × 16 × 16 bits as gradation data of one frame.

The frame memory 12 stores the gradation data output from the video display controller 8 in order. The frame memory 12 has 16 × 16 RGB Ls.
The ED gradation data is stored together with an address specifying each LED. However, the frame memory 12
Need not necessarily store the address. that is,
Since the output order of the frame memory 12 is determined,
This is because the addresses can be specified in the order of output from the frame memory 12.

The frame memory 12 has a buffer memory 13 connected to the output side. The buffer memory 13
One column of gradation data output from the frame memory 12 is temporarily stored. The frame memory 12 sequentially outputs one column of gradation data from the stored one frame of gradation data to the buffer memory 13. The gradation data output from the frame memory 12 to the buffer memory 13 is transmitted in parallel as 8-bit gradation data. For example, LE of a picture element of 16 columns x 16 rows
The LED unit 9 for dynamically lighting D causes the buffer memory 13 to store gradation data of 16 pixels in one row. If one picture element is displayed by three LEDs and each LED is displayed by 8-bit gradation data, the buffer memory 13 stores 8 × 3 ×
16-bit gradation data is stored.

The video data stored in the buffer memory 13 specifies the time during which one row of LEDs of the LED display is turned on in one luminance modulation frame cycle.
In other words, the buffer memory 13 stores the luminance at which one row of LEDs of the LED display emits light.
The gradation data as the luminance signal is stored in the frame memory 1
2 output. The frame memory 12 sequentially outputs one column of video data of each column to the buffer memory 13, and sequentially turns on the LEDs of each column of the LED display.

The output of the buffer memory 13 is connected to the comparator 2. The comparator 2 includes a video display controller 8
Is compared with the gradation control clock inputted from the buffer memory 13 and the gradation control clock inputted from the buffer memory 13.
Are output to the pulse output circuit 3. Comparator 2
The pulse output circuit 3 is provided with 16 × 3 sets to emit 16 × 3 LEDs in one row.

The driver 5 turns on all the LEDs by sequentially switching the LEDs in each row. The driver 5 turns on one row of LEDs together with the on / off pulse output from the pulse output circuit 3 for the time specified by the gradation data, that is, the luminance.

The driver 5 switches the common line of the LED display at a constant period and a common driver 5A, and adjusts the lighting time of the LED by the output signal of the buffer memory 13 to turn on the LED at the luminance corresponding to the video data. And a segment driver 5B.
The LED display turns on an LED that connects both the common driver 5A and the segment driver 5B to a power supply (not shown). That is, both drivers 5
Is turned on, the LED is turned on.

The common driver 5A is controlled by the video display controller 8 to sequentially switch the LEDs in each column and connect to the power supply. For example, if the frame period is 1/60
Seconds (approximately 16 msec)
When using a × 16 picture element, the common driver 5A
The common line is switched at a cycle of about 1 msec.

The segment driver 5B incorporates a switching element (not shown) that is switched by an on / off pulse output from the pulse output circuit 3. When the switching element is turned on, the LED in the column connecting the common line to the power supply is turned on. The ON time of the switching element adjusts the brightness of the LED. When the switching element is turned on, the LED emits light by passing a constant current. If the ON time of the switching element is short, L
The ED emits dark light. When the ON time of the switching element becomes long, the LED emits light brightly. The ON time of the switching element is determined by the pulse width of the ON / OFF pulse.

The segment driver 5B controls the ON time of each switching element with the ON / OFF pulse of the pulse output circuit 3 to adjust the brightness of the LED to emit light. The plurality of switching elements are turned on / off in parallel by the on / off pulse of the pulse output circuit 3. Therefore, the on time of the switching elements connected to each column is adjusted by the on / off pulse output from the pulse output circuit 3.

The segment driver 5B turns on the LEDs in the column connected to the power supply by the common driver 5A for a time corresponding to the gradation data, and when the common driver 5A is switched to the next column, the LEDs in each column are successively turned on. Is turned on for a predetermined time. Therefore, the segment driver 5B
Turns on and off the switching elements in synchronization with the common driver 5A, turns on all the LEDs one after another for a predetermined time, and emits light at a predetermined luminance.

The frame memory 12 sequentially outputs one frame of video data to the buffer memory 13, and the gradation data in the buffer memory 13 is processed by the comparator 2 and the pulse output circuit 3, and drives the driver 5 to drive the LED 5. Display video on the display.

[0045]

The display method of the LED display according to the present invention has a feature that the LED can be adjusted to an ideal light emission time by correcting the cycle of the gradation control clock without correcting the gradation data. In particular, the display method of the LED display of the present invention adjusts the lighting time of the LED even by the same gradation data by changing the period between the first half and the second half of the luminance modulation frame period. This method is characterized in that the lighting time of the LED can be adjusted very finely without increasing the number of bits of the gradation data, so that the LED can be lit with ideal light emission luminance.

[Brief description of the drawings]

FIG. 1 is a graph showing a gradation control clock in a display method of a conventional LED display.

FIG. 2 is a graph showing a gradation control clock in a display method of an LED display according to the related art and the embodiment of the present invention.

FIG. 3 is a graph showing a change in LED lighting time with respect to gradation data in a display method of an LED display according to an embodiment of the present invention.

FIG. 4 is a block diagram showing a lighting circuit used in a display method of an LED display according to an embodiment of the present invention.

5 is a block diagram showing a gradation control clock generation circuit of the lighting circuit shown in FIG. 4;

FIG. 6 is a block diagram of an apparatus using a display method of an LED display according to an embodiment of the present invention.

FIG. 7 is a block diagram of an LED unit of the device shown in FIG. 6;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Lighting circuit 2 ... Comparator 3 ... Pulse output circuit 4 ... Grayscale control clock generation circuit 4A ... Programmable divider 4B ... Counter 4C ... Division ratio memory 5 ... Driver 5A ... Common driver 5B ... Segment driver 6 ... Computer 7 ... Monitor TV 8 Video display controller 9 LED unit 10 Luminance sensor 11 A / D converter 12 Frame memory 13 Buffer memory 14 VTR

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G09G 3/00-3/16 G09G 3/20-3/32 H04N 5/66

Claims (3)

(57) [Claims] 1. A lighting circuit compares an LED lit at an early stage of a luminance modulation frame cycle with a gradation control clock inputted one after another and gradation data of a digital signal by a lighting circuit. When the count value of the clock reaches a digital value that specifies gradation data, the LED is turned off, and the LED lighting time is adjusted by controlling the lighting time of the LED with the gradation data within the luminance modulation frame period to adjust the light emission luminance. The number of gradation control clocks in one luminance modulation frame period is the same or substantially the same, and the gradation control clock is stored in the frequency division ratio memory in the first half and the second half of the luminance modulation frame period.
When the frequency division ratio is stored with the count number of
The division ratio output from the division ratio memory is
Selected based on the data from the
Output a gradation control clock with a period that is an integral multiple of the
The control clock cycle is initially longer and gradually shorter
Or shorter at first and gradually longer
The period is changed as described above , and L
A method for displaying an LED display, comprising adjusting a lighting time of an ED. 2. The number of gradation control clocks in one luminance modulation frame period is made to be the same or substantially the same, and the period of the gradation control clock is changed between the first half and the second half of the luminance modulation frame period. The display method for an LED display according to claim 1, wherein the lighting time is adjusted together. 3. The number of gradation control clocks in one luminance modulation frame period is made the same or almost the same, and the period of the gradation control clocks is changed between the first half and the second half of the luminance modulation frame period, so that the RGB LED The display method of an LED display according to claim 1, wherein the lighting time is adjusted independently.