JPH07311560A - Multicolor led display unit - Google Patents

Abstract

PURPOSE:To provide a multicolor display unit which can eliminate luminance nonuniformity of LED using a simple circuit consitution. CONSTITUTION:The multicolor display unit is provided with a plurality of LEDs which are arranged close to each other and emit different luminuous colors and an LED lighting circuit which flashes each LED and adjusts its lummous color and brightness. The LED lighting circuit is provided with a pulse width modulation circuit 2 which outputs pulses corresponding to input gray level data and an LED drive circuit 3 that lights LEDs by output pulses of the pulse width modulation circuit 2 which nonlinearly modulates output pulse widths in accordance with input gray level data.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to LEDs of different emission colors.
The present invention relates to an LED display unit for displaying multi-color by adjusting the light emission output of each LED.

[0002]

2. Description of the Related Art A full-color LED display unit can be realized by using red, blue and green LEDs. This LED display unit displays one dot in full color with three types of LEDs whose emission colors are red, blue and green.
One-dot three-color LEDs are arranged close to each other. The LED display unit having this structure can change the emission color by adjusting the brightness of the red, blue, and green LEDs. For example, when all the LEDs are turned on, it becomes white, and when the red and blue LEDs are turned on, magenta, red and green become yellow, and green and blue become cyan. Furthermore, the brightness of each LED can be adjusted to produce various emission colors.

The LED display unit uses a lighting circuit to blink each LED at regular intervals. When the lighting circuit adjusts the time for lighting the LED, it is possible to adjust the brightness perceived by the eyes, that is, the substantial emission brightness of the LED. The longer the LED is turned on once, the brighter it feels. When the lighting time is shortened, it feels dark. The frequency with which the lighting circuit blinks the LED is adjusted to be higher than 40 Hz, for example about 100 Hz, to prevent flicker. When the blinking cycle is 100 Hz, the LED blinks 100 times per second.

The lighting circuit uses the input gradation data for LE.
The lighting time of D is calculated. In order to specify the lighting time of the LED, the lighting circuit includes a pulse width modulation circuit which outputs a pulse having a time width corresponding to the input gradation data.
The output pulse of the pulse width modulation circuit is L for lighting the LED.
The pulse signal is input to the ED drive circuit, and the LED drive circuit switches by the pulse signal to blink the LED. For example, in the LED drive circuit, the input pulse is "High".
The LED is turned on when "h" and turned off when "Low".

The gradation data input to the pulse width modulation circuit is information for determining the brightness of the LED. The pulse width modulation circuit modulates the time width of the output pulse in accordance with the input grayscale data. The pulse width modulation circuit becomes brighter as the input grayscale data becomes brighter.
Increase the time width of the output pulse. FIG. 1 is a graph showing the time width of the output pulse with respect to the grayscale data input to the pulse width modulation circuit. As shown in this figure, if the time width of the output pulse is widened in proportion to the gradation data, the lighting time of the LED can be lengthened in proportion to the gradation data. Since the LED with a long lighting time feels bright to the eyes, the LED can be brightly lit in proportion to the gradation data.
The brightness of the red, blue, and green LEDs is adjusted in proportion to the input gradation data.

[0006]

As described above, L which adjusts the brightness of the red, blue, and green LEDs in proportion to the gradation data.
The ED display unit can display full color. However, in the LED display unit having this structure, variations in brightness among the LED units of each emission color poses a serious problem. If there is a variation in the emission brightness between the LED units, tile-like brightness unevenness is identified, and the quality of the display is greatly deteriorated. In order to prevent this adverse effect, the LEDs of each emission color are level-selected according to brightness. However, using the identified LED,
If the brightness is finely adjusted based on the gradation data, the uneven brightness becomes more noticeable, and it becomes necessary to select the LEDs at a finer level. Therefore, there is a drawback that the yield of LEDs is significantly reduced.

In order to prevent this drawback, a technique for positively adjusting the brightness has been developed. The first method is LE
This is a method of adjusting the current value for driving D. This method modulates a pulse into a time width with gradation data, and further, L
The drive current of the ED is adjusted to correct the uneven brightness. That is, the pulse is width-modulated by the gradation data and the
The amplitude of the pulse is modulated by the uneven brightness of the pulse. This method can be well matched with pulse width modulation with grayscale data. However, a constant current circuit for adjusting the drive current of the LED and a switching circuit for correcting the current value are required, which has the drawback of complicating the circuit. Furthermore, in order to amplitude-modulate the output pulse, LE
A switching element that reduces the current flowing through D is required. The switching element that reduces the current has a large internal resistance and consumes part of the LED drive current. For this reason, the switching element consumes a large amount of power and cannot effectively use the power. Further, the switching element generates heat and a large amount of heat is generated, and it is necessary to design the heat capacity of the switching element to be large.

As a second technique for correcting the luminance unevenness of the LED, there is a technique for adjusting the luminance at which the LED is turned on by the blink rate in the frame period. In this method, if the spread width is widened, the variable width range of the pulse in which the grayscale data is modulated must be narrowed. Further, this method has a drawback that the luminance unevenness of the LED can be corrected only at one point where the gradation pulse exists.

The present invention was developed for the purpose of solving this drawback, and an important object of the present invention is to provide a multi-color LED display unit capable of eliminating uneven brightness of LEDs with an extremely simple circuit configuration. To provide.

[0010]

The multi-color LED display unit of the present invention has the following constitution in order to achieve the above-mentioned object. The LED display unit includes a plurality of LEDs of different emission colors, which are arranged close to each other, and each L for displaying a plurality of colors.
An LED lighting circuit for adjusting the emission color and brightness by blinking the ED is provided.

The LED lighting circuit outputs a pulse corresponding to the input gradation data, and a pulse width modulation circuit, and the LED is lit by the output pulse of the pulse width modulation circuit.
And an ED drive circuit. The pulse width modulation circuit has a built-in gain adjusting means for adjusting the pulse width modulation gain with respect to the grayscale data, depending on the color of the emitted light or the individual LEDs. The gain adjusting means may be the emission color or the individual LE.
The pulse width for the gradation data is corrected by D, and L
It is configured to correct the emission brightness of the ED.

The gain adjusting means corrects the uneven brightness of the LED units of each emission color or the uneven brightness of the individual LED units. FIG. 2 shows L having different emission colors.
It shows a state in which the uneven brightness of the ED unit is corrected.
The LED display unit shown in this figure has LEDs for the same gradation data in the order of green, red, and blue in order from the longest.
The lighting time of is corrected to make it brighter.
The LED unit of each emission color adjusts the modulation gain so that white balance can be obtained when the same gradation data is obtained. The gain adjusting means corrects the input gradation data and performs pulse width modulation so that the emission luminance shown in FIG. 2 is obtained. Therefore, even if the grayscale data of red, blue, and green are the same, the output pulse width is not corrected to have the same pulse width. Even if the same gradation data is input, the pulse width is corrected wider in the order of green, red, and blue. The gain adjusting means corrects the pulses for lighting the green, red, and blue LEDs at the same ratio even if the input level of the gradation data is changed. Therefore, even if the level of the input gradation data changes, the white balance of the red, blue, and green LEDs is not disturbed.

Further, the gain adjusting means includes individual LEDs.
It is also possible to correct the emission brightness of. The gain adjusting means for achieving this corrects the drive pulse of each LED to a predetermined width when the same gradation data is input,
Correct to the same brightness.

[0014]

In the multi-color LED display unit of the present invention, the input grayscale data is pulse width modulated by the pulse width modulation circuit. The output pulse of the pulse width modulation circuit is input to the LED drive circuit, and the LED drive circuit blinks the LED with the input pulse. The LED drive circuit is turned on when a pulse is input to light the LED. Therefore, when the pulse width is wide, the lighting time of the LED is long, and conversely, when the pulse width is narrow, the LE is long.
The lighting time of D becomes short.

The pulse width modulation circuit width-modulates the pulse in accordance with the input gradation data. Preferably, the pulse width modulation circuit nonlinearly modulates the pulse with respect to the input grayscale data, that is, nonlinearly. As shown in FIG. 3, the pulse width modulation circuit makes the pulse width smaller than the linear state when the gradation data is small, and makes the pulse width larger than the linear state when the gradation data is large. This is because the amount of change in the stimulus value is high in the dark and decreases in the bright.

Further, in the LED display unit of the present invention, the pulse width modulation circuit has a built-in gain adjusting means. The gain adjusting means, as shown in FIG. 3, corrects the gain for pulse width modulation of the input gradation data. That is, for an LED that needs to be brightly lit, the pulse width is corrected to be wide as shown by a broken line A in the figure, and the LED is dimly lit.
The ED narrows the pulse width as shown by the broken line C in the figure. The gain adjusting means always corrects the pulse width with the same gain for the gradation data. Therefore, even if the input level of the gradation data changes, the pulse width is corrected at the same ratio as shown by the curves A, B, and C in the figure.

As shown in FIG. 3, if the gain for modulating the pulse width is corrected by the gain adjusting means, the emission brightness of the LED can be corrected as shown in FIG. In FIG. 3, the broken lines A, B, and C are shown in order of green, red, and blue LEDs.
LED has a characteristic that corrects the emission brightness of
As for the luminance of, the green, red, and blue are brightly lit in descending order as shown in FIG. This is because the LED becomes brighter as the pulse width becomes wider. Correct the emission brightness as shown in FIG.
When the correction is performed so that the white balance is good, the white balance can be obtained by using the red, blue, and green LEDs having different emission luminances.

[0018]

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

The multi-color LE shown in FIGS. 4 and 5
The D display unit includes LEDs of red, blue, and green emission colors arranged close to each other, and an LED lighting circuit for blinking the LEDs of each emission color. The three LEDs whose emission colors are red, blue and green are arranged close to each other. This LED display unit adjusts the brightness by the emission time of three LEDs emitting red, blue, and green to display one dot in full color. A large number of LEDs are connected in a matrix as shown in FIG.

The lighting circuit includes a pulse width modulation circuit 2 that outputs a pulse corresponding to the input gradation data, and an LED that lights the LED with an output pulse of the pulse width modulation circuit 2.
And a drive circuit 3. The LED drive circuit 3 includes a scan driver 3a that switches a common line that horizontally connects LEDs in a fixed cycle and an LED that is vertically connected by a pulse width modulation circuit 2 and that has a pulse corresponding to grayscale data. And a gradation driver 3b that lights in a width. The LED display unit shown in FIG.
LE by connecting both a and the gradation driver 3b to the power supply 8
Turn on D.

The scan driver 3a sequentially switches the LEDs on each column to connect the power source 8. Scan driver 3a
In order to prevent the flickering of the blinking LEDs, the four lines of common lines are set to 100 Hz, for example, as shown in the figure.
Switch in the cycle. The switching circuit for switching the common lines in four rows at 100 Hz has a lighting time of one row of 2.5 ms.

The gradation driver 3b contains a plurality of switching elements 3s. When the switching element 3s is turned on, the LEDs in the row connecting the common line to the power supply 8 are turned on. The ON time of the switching element 3s adjusts the brightness of the LED. Switching element 3s
When the LED is turned on, the LED emits a constant current. To make the LED emit light in the dark, the switching element 3
In order to shorten the ON time of s to shorten the lighting time and emit bright light, the ON time of the switching element 3s is lengthened to lengthen the lighting time.

The gradation driver 3b controls the on-time of each switching element 3s by the output of the pulse width modulation circuit 2 and adjusts the brightness of the LED to emit light.
In order to turn on / off the switching element 3s, the pulse width modulation circuit 2 outputs a pulse having a predetermined time width. The plurality of switching elements 3s are processed in parallel by the output of the pulse width modulation circuit 2. Therefore, the switching element 3s connected to each column is adjusted by the pulse signal output from the pulse width modulation circuit 2 to be turned on.

The gradation driver 3b is the scanning driver 3
The LED of the row connected to the power source 8 at a is turned on for a time corresponding to the gradation data, and when the scan driver 3a is switched to the next row, the LEDs of each column are turned on one after another for a predetermined time. Therefore, the gradation driver 3b turns on and off the switching element 3s in synchronization with the scanning driver 3a, and sequentially turns on all LEDs for a predetermined time to emit light with a predetermined brightness.

As described above, when the scanning driver 3a and the gradation driver 3b cause the LEDs of the respective colors to emit light for a time corresponding to the input gradation data to generate the light and shade of the LEDs, the color expression is the number of products. Will be possible.

The LED display unit shown in FIGS. 4, 5 and 6 includes three sets of pulse width modulation circuits 2 dedicated to red, blue and green. LE of red, blue, and green with gradation data of each color
This is because D is made to blink independently. The three sets of pulse width modulation circuits 2 correct the input grayscale data by the gain adjusting means 13 and perform pulse width modulation.

As shown in FIG. 7, the gain adjusting means 13 is composed of three sets of non-linear counters 6 and a reference clock frequency variable circuit 9 for controlling the count time of the non-linear counters 6. The time counted by the non-linear counter 6 is controlled by the reference clock frequency variable circuit 9. The non-linear counter 6 controls the red, blue, and green pulse width modulation circuits 2 at the counting time, that is, at the count frequency.
Correct the modulation gain of. The red, blue and green pulse width modulation circuits 2 are controlled by the gain adjusting means 13 so that the broken line A in FIG.
The modulation gain of the output pulse is corrected as indicated by B and C. The broken line in FIG. 3 indicates that the modulation gain of the pulse width modulation circuit 2 is increased in the order of green, red, and blue.

In order to explain that the count time of the nonlinear counter 6 adjusts the modulation gain of the pulse width modulation circuit 2, the operation of the pulse width modulation circuit 2 will be described first.

The red, blue, and green pulse modulation circuit 2 converts the input red, blue, and green gradation data into pulses having a predetermined time width. The red pulse width modulation circuit 2 receives red gradation data, the blue pulse width modulation circuit 2 receives blue gradation data, and the green pulse width modulation circuit 2 receives green gradation data.
The width of the blue and green LEDs is modulated to a lighting pulse.

FIG. 8 shows a red pulse width modulation circuit 2. The blue and green pulse width modulation circuit 2 can be realized by the same circuit. As shown in FIGS. 2 and 3, the pulse width modulation circuit 2 shown in this figure not only corrects the modulation gain of the LEDs of each emission color by the emission color but also modulates the gradation data nonlinearly. . The non-linear modulation of the gradation data makes the brightness of the LED darker than that in the linear state when the level of the gradation data is small, and makes it brighter than the nonlinear state when the level of the gradation data becomes large. To realize this, a nonlinear counter 6 is connected to the pulse width modulation circuit 2. Further, the storage circuit 1 which temporarily stores the input red gradation data is connected to the input side of the pulse width modulation circuit 2. The gradation data of red is input to the storage circuit 1 from the outside of the LED display unit each time. As shown in this figure, the pulse width modulation circuit 2 to which the non-linear counter 6 is connected becomes a non-linear pulse width modulation circuit 2 that non-linearly modulates the pulse width in accordance with the grayscale data input from the storage circuit 1. .

The memory circuit 1 shown in FIG. 8 can store and latch 8-bit gradation data sequentially sent from an external device such as an LED display controller at a predetermined column address. In the figure, reference numeral 4 is a memory therefor, which is composed of 8 bits × 16. 5 is 1
The buffer memory 5 is for outputting the gradation data of 16 dots for each row to the nonlinear pulse width modulation circuit 2 in parallel simultaneously. The storage circuit 1 including the memory 4 and the buffer memory 5 can be similarly configured by a shift register and a latch circuit for 8 bits and 16 dots. The storage circuit 1 temporarily stores the sequentially inputted gradation data in the memory 4. The stored value of the memory 4 is output to the buffer memory 5, and the buffer memory 5 simultaneously outputs the gradation data to be stored to the nonlinear pulse width modulation circuit 2.

Reference numeral 2 denotes a pulse width modulation circuit 2 for non-linearly modulating gradation data, which is a digital mono-multi composed of a digital comparator 7 for inverting the output signal from the non-linear counter 6. The non-linear counter 6 is an 8-bit binary counter, which is released from reset by the row latch pulse and starts counting. The digital comparator 7 is an 8-bit magnitude comparator and is provided for 16 bits.

An 8-bit binary signal, which is the count value of the non-linear counter 6, is input to one input side of the digital comparator 7. To the other input side of the digital comparator 7, 8-bit grayscale data for 16 dots is input from the buffer memory 5. Each digital comparator 7 compares the count value input from the non-linear counter 6 with the grayscale data input from the buffer memory 5. The count value output from the non-linear counter 6 increases as time passes.
The digital comparator 7 compares the output from the non-linear counter 6 with the grayscale data which is the output of the buffer memory 5, and when both match, inverts the output set at the time of starting the counting and outputs the pulse. Output. The time width of the pulse output from the digital comparator 7 becomes longer as the gradation data is larger. This is because the output of the digital comparator 7 is not inverted unless the count value output from the non-linear counter 6 becomes large.

The non-linear counter 6 does not count linearly with time but counts non-linearly. The non-linear counter 6 is early at the beginning of counting and becomes slower to count as time passes. This is because the digital comparator 7 modulates gradation data into a non-linear pulse width. When the count value is input from a counter that counts linearly with respect to time, the digital comparator linearly width-modulates the pulse with respect to the input grayscale data. On the other hand, when a non-linear count value is input from the non-linear counter 6, the digital comparator 7 non-linearly width-modulates the pulse of the gradation data.

The solid line in FIG. 9 shows the count value of the non-linear counter 6 that counts non-linearly with respect to time, and the broken line shows the count value of the linear counter that counts linearly with respect to time. In this figure, the time when the count value is A1 is the time T1 for the non-linear counter 6 and the time T2 for the linear counter. That is, the non-linear counter 6 has a shorter time than the linear counter. Digital comparator 7
Compares the count value of the non-linear counter 6 with the gradation data, and inverts the output when both are the same. That is, a pulse having a time width from resetting until both inputs become the same is output. For example, if the gradation data whose level is A1 is input to the digital comparator,
The non-linear pulse width modulation circuit 2 connected with the non-linear counter 6 outputs a pulse of time T1, and the pulse width modulation circuit connected with the linear counter outputs a pulse of time T2. The nonlinear pulse width modulation circuit 2 connected to the nonlinear counter 6 outputs a pulse having a short time width.

However, when a large level of grayscale data of A2 is input to the nonlinear pulse width modulation circuit 2, until the count value of the nonlinear counter 6 reaches this level,
It takes longer than linearly counting and outputs a pulse corresponding to time T4 having a wide time width. That is, as shown in FIG. 9, the digital comparator 7 connected with the non-linear counter 6 which counts fast first and gradually slows down counts the time width of the output pulse with respect to the grayscale data as shown in FIG. Modulates nonlinearly and outputs.

The pulse signal output from the digital comparator 7 is the gradation driver 3 which is the LED drive circuit 3.
Input to b. The LED drive circuit 3 receives the pulse output from the nonlinear pulse width modulation circuit 2
Equipped with an enable terminal to blink.

FIG. 10 is a concrete block diagram of the non-linear counter 6 which counts non-linearly with respect to time. The non-linear counter 6 shown in this figure is provided with a total of 16 types of count pulses P _{0 to} P ₁₅ by the reference clock frequency variable circuit 9. 4 → 16 decoder 11
Is a decoder circuit for generating a selection signal for selecting the 16 types of count pulses from the upper 4 bits of the binary counter 12.

Reference numeral 10 is a selection circuit for selecting one from 16 types of count pulses and inputting it to the binary counter 12 according to the selection signal.

The non-linear counter 6 in this figure counts non-linearly and outputs the count value to the digital comparator 7. The digital comparator 7 connected to the non-linear counter 6 in this figure outputs a pulse having a pulse width y with respect to the grayscale data x, as indicated by the broken line in FIG. The broken line shown by the broken line in this figure is the curve y = ax ⁿ (n =
2.2) can be approximated by 16 broken lines. In this equation, n is a constant that determines nonlinearity. n =
When set to 1, the gradation data is linearly pulse-width modulated.

Further, in the equation of the function y = ax ⁿ , the constant a specifies the modulation gain of the pulse width modulation circuit 2.
When the value of a is large, the slope of the curve in FIG. 11 becomes large and the modulation gain becomes large. On the contrary, when the value of a is reduced, the modulation gain is reduced and the slope of the curve becomes gentle. The modulation gain of the pulse width modulation circuit 2, that is, FIG.
The slope of the curve of 1 can be adjusted by the cycle of the clock pulse output from the reference clock frequency variable circuit 9 to the nonlinear counter 6, that is, the frequency.

When the frequency of the reference clock frequency variable circuit 9 becomes high and the cycle of the clock pulse becomes short, the number of pulses input to the non-linear counter 6 per unit time increases. That is, the number of counts of the non-linear counter 6 increases. In other words, it takes less time to reach a certain count. Since the digital comparator 7 compares the gradation data with the count value input from the non-linear counter 6, the time when the count value output from the non-linear counter 6 to the digital comparator 7 becomes the same as the gradation data is shortened. . Therefore, the time determined by the digital comparator 7 becomes shorter, and the time width of the output pulse becomes shorter. Therefore, when the frequency of the reference clock frequency variable circuit 9 is increased, the modulation gain of the pulse width modulation circuit 2 is adjusted to be low. This is because the pulse width of the input grayscale data is corrected to be narrow.

FIG. 12 shows clock pulses output from the reference clock frequency variable circuit 9 to the red, blue, and green nonlinear counters 6. In this figure, as shown in FIG. 3, the modulation gains are adjusted in the order of green, red, and blue in descending order. If the frequency of the clock pulse is high, the modulation gain becomes small, so the reference clock frequency variable circuit 9
The clock pulse output from the nonlinear counter 6 to
Green, red, and blue are higher in descending order.

The reference clock frequency variable circuit 9 is red,
In order to adjust the cycle of the clock pulse output to the blue and green nonlinear counters 6, a gain signal for controlling the frequency of each clock pulse is input. As shown in FIG. 13, the reference clock frequency variable circuit 9 is a PROM which is a program counter for dividing an input reference clock pulse and a memory for setting a division ratio of the program counter with an input gain signal. Can be achieved with. Other than this embodiment, the same effect can be obtained by any means that can change the cycle of the clock pulse.

As shown in FIG. 14, the LED units of each luminescent color are sorted into luminance ranks A to H for each LED unit of each luminescent color and mounted on the dot matrix unit. For example, when using a dark green LED unit of rank C, a red LED unit of rank E, and a bright blue LED unit of rank G in combination, increase the modulation gain in the order of green, red, and blue. To adjust the white balance of the LED unit of each emission color.

FIG. 15 shows a reference clock frequency variable circuit 9 of an LED display unit which uses LED units sorted by ranks A to H as shown in FIG. The reference clock frequency variable circuit 9 shown in this figure is
It is composed of a frequency dividing circuit 14 for obtaining a clock pulse having a reference frequency of PA to PH and a gate circuit 15 for selecting a clock pulse having a reference frequency of PA to PH. A gain signal is input to the gate circuit 15 as a selection signal according to the brightness rank of each LED unit.

In the above embodiment, the gradation data is 8 bits and the emission colors of the LEDs are red, blue and green. However, in the LED display unit of the present invention, the gradation data is 4
It can be bit or otherwise. If the number of bits of gradation data is reduced, the number of colors that can be expressed will be reduced, but the circuit scale can be simplified. Further, full color display is possible in which the LED emission colors are three colors of red, blue and green, but it goes without saying that it is also possible to use two emission color LEDs.

Further, in the LED display units of the above embodiments, the modulation gains of the LED units of each emission color are adjusted, but the modulation gains of individual LEDs can also be adjusted. The LED display unit that realizes this distinguishes the brightness of each LED into ranks, and adjusts the modulation gain of the gradation data that is input according to the rank of the brightness of each LED.

[0049]

The multi-color LED display unit of the present invention corresponds to the brightness of the LED unit of each emission color, or corresponds to the brightness of each LED.
The modulation gain for pulse width modulation with respect to the input gradation data is adjusted. Therefore, it is possible to eliminate the uneven brightness of the LED and realize a high quality LED display unit. In particular, the LED display unit of the present invention is
Adjust the LED drive current as before, or
The LED lighting time is corrected by controlling the modulation gain that performs pulse width modulation, rather than by pulsing the pulse that lights the LED to adjust the brightness that the eye perceives. For this reason,
The LED display unit of the present invention can reduce the heat generation of the circuit for blinking the LED, and can use a small capacity switching element for this circuit. Can be produced. Further, since the modulation gain is corrected to correct the brightness unevenness of the LED, the brightness can be accurately corrected in the entire range of the gradation data, and an extremely high quality LED display unit can be obtained. . Furthermore, since the LEDs with uneven brightness can be used to correct the variation in the brightness of the LED display unit,
It also simplifies the selection of LEDs and realizes the features that LEDs can be made inexpensive.

[Brief description of drawings]

FIG. 1 is a graph showing a pulse width linearly modulated by gradation data input to a pulse width modulation circuit.

FIG. 2 is a graph showing a relationship in which a non-linear pulse width modulation circuit provided in the LED display unit of the present invention gain-adjusts gradation data and modulates it to the emission brightness of the LED.

FIG. 3 is a graph showing a relationship in which a non-linear pulse width modulation circuit provided in the LED display unit of the present invention performs gain adjustment of gradation data and performs pulse width modulation.

FIG. 4 is a front view showing an array of LEDs of the LED display unit according to the embodiment of the present invention.

5 is a block diagram showing a lighting circuit of the LED display unit shown in FIG.

6 is a block diagram of the lighting circuit shown in FIG.

FIG. 7 is a block diagram of the lighting circuit shown in FIG.

8 is a block diagram of the lighting circuit shown in FIG.

FIG. 9 is a graph showing count values with respect to time of a non-linear counter.

FIG. 10 is a block diagram of a non-linear counter.

FIG. 11 is a graph showing a characteristic in which the pulse width modulation circuit performs pulse width modulation on gradation data.

FIG. 12 is a graph showing clock pulses output by the reference clock frequency variable circuit to the red, blue, and green nonlinear counters.

FIG. 13 is a block diagram showing an example of a reference clock frequency variable circuit.

FIG. 14: Luminance ranks A to LED units of each emission color
Graph showing H

FIG. 15 is a block diagram of a reference clock frequency variable circuit of an LED display unit using LED units sorted by ranks A to H shown in FIG.

[Explanation of symbols]

1 ... Memory circuit 2 ... Pulse width modulation circuit 3 ... LED drive circuit 3a ... Scan driver 3b ...
Gradation driver 3s ... Switching element 4 ... Memory 5 ... Buffer memory 6 ... Non-linear counter 7 ... Digital comparator 8 ... Power supply 9 ... Reference clock frequency variable circuit 10 ... Selection circuit 11 ... 4 → 16 Decoder 12 ... Binary counter 13 ... Gain adjustment Means 14 ... Dividing circuit 15 ... Gate circuit

Claims (2)

[Claims] 1. A multi-colored multi-color apparatus comprising a plurality of LEDs of different emission colors arranged close to each other, and an LED lighting circuit for controlling the lighting time of each LED to adjust the emission color and brightness. In the LED display unit, the LED lighting circuit outputs a pulse having a time width corresponding to the input grayscale data, and an LED that lights the LED with the output pulse of the pulse width modulation circuit.
A pulse width modulation circuit that includes a gain adjusting unit that adjusts the modulation gain of the pulse width for the gradation data according to the emission color, and the gain adjusting unit adjusts the pulse width for the gradation data according to the emission color. A multi-color LED display unit, which is configured to correct unevenness of light emission luminance of LED units having different emission colors. 2. A multicolor LED comprising a plurality of LEDs of different emission colors arranged close to each other and an LED lighting circuit for controlling the lighting time of each LED to adjust the emission color and brightness. In the LED display unit, the LED lighting circuit outputs a pulse having a time width corresponding to the input grayscale data, and an LED that lights the LED with the output pulse of the pulse width modulation circuit.
And a pulse width modulation circuit for driving the individual LEDs.
, The gain adjusting means for adjusting the modulation gain of the pulse width for the gradation data is built in, and the gain adjusting means is
A multi-color LED display unit, characterized in that it is configured to correct the pulse width for gradation data by individual LEDs to correct the unevenness of the emission brightness of LED units of different emission colors.