JP2018180423A - Led display system and led display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress power consumption of an LED display device.SOLUTION: An LED display system 300 includes a control apparatus 200 and an LED display device 100. The control apparatus 200 includes: an average luminance calculation unit 24 which calculates an average luminance value of pixels constituting each frame in a video signal; a correction coefficient calculation unit 25 which calculates a luminance correction coefficient for correcting luminance of a video signal, on the basis of the average luminance value calculated in the average luminance calculation unit 24, so that power consumption of the LED display device 100 may be equal to or lower than a predetermined value; and a video signal distribution unit 14 which distributes the video signal and the luminance correction coefficient calculated in the correction coefficient calculation unit 25, to the LED display device 100. The LED display device 100 includes: a plurality of LEDs 1 serving as display pixels; a luminance adjustment unit 9 which adjusts luminance of a video signal, on the basis of a luminance correction coefficient distributed from the video signal distribution unit 14; and an LED driving unit 4 which drives the LEDs 1 on the basis of the video signal with luminance adjusted in the luminance adjustment unit 9.SELECTED DRAWING: Figure 1

Description

  In the present invention, a control device and a plurality of LEDs (Light Emitting Diodes) are arranged in a matrix, and an image is displayed by controlling blinking of each LED based on a video signal distributed from the control device. The present invention relates to an LED display system including an LED display device, and more particularly to an LED brightness control technique.

  LED display devices that use a plurality of LEDs as display pixels are often used for indoor / outdoor advertisement display etc. due to technological development and cost reduction of LEDs. Until now, these LED display devices have mainly displayed moving images such as natural images and animations, but as the visual distance becomes shorter as the pixel pitch becomes narrower, conferences in indoor applications It is also used for applications such as monitoring. In particular, in monitoring applications, LED display devices often display an image close to a still image input from, for example, a personal computer or the like.

  In general, LEDs of three primary colors of R, G and B are used as display pixels of the LED display device, and the color tone is achieved by PWM (Pulse Width Modulation) control of the light emission time of the R, G and B LEDs. Is expressed. However, since the LEDs consume the maximum power in the lighting state and consume almost no power in the non-lighting state, for example, 20 for the full bit all white signal (LEDs of each color of R, G and B emit 100% duty ratio) In a% gray signal (LEDs of R, G, and B each emit light with a duty ratio of 20%), the power consumption of the LEDs is approximately 20%. As described above, in the LED display device, the power consumption largely varies depending on the contents of the video signal.

  Therefore, Patent Document 1 discloses a display device that achieves power saving by suppressing an increase in power supply capacity. In the display device described in Patent Document 1, the current value flowing to the display panel is predicted based on the input video signal. When the sum of the current values in frame units becomes equal to or greater than a predetermined threshold value, the display device performs video signal processing for correcting the contrast and brightness of the image, and the current value flowing through the display panel is predetermined. Control not to exceed the maximum value of.

Patent No. 4808913

  An LED display generally comprises a plurality of devices. For example, a full HD (1920 × 1080 pixels) image is displayed by combining a 320 × 180 pixel LED display (hereinafter also referred to as “unit LED unit”) with a total of 36 units of 6 units in the horizontal direction × 6 units in the vertical direction. . Each unit LED unit consumes the maximum power when displaying a full bit all white signal (LEDs of R, G and B each emits light with a duty ratio of 100%), and the power consumption becomes the rated value. Therefore, in the system having the resolution of FullHD as described above, it is necessary to prepare a power capacity of 36 × unit power consumption of the unit LED unit.

  However, there are many images that can be displayed with relatively little power consumption such as gray back or light color, etc., for monitoring applications etc., and it is often excessive to prepare the maximum power capacity calculated from the rated value . In addition, there is a problem that additional power supply construction is required if the existing facility capacity is insufficient despite the fact that the amount of power consumption calculated at the maximum rated value is excessive.

  Here, the technology described in Patent Document 1 relates to a single LED display device, and relates to an LED display system including a control device and an LED display device that displays an image based on a video signal from the control device. is not. In addition, when a plurality of unit LED units display an image, such as when a large screen is configured by a plurality of unit LED units, power saving control is performed in each unit LED unit according to the technology described in Patent Document 1. There is a problem that the brightness of a plurality of unit LED units can not be collectively controlled, for example, only a part of the unit LED units is lowered in brightness due to power saving control.

  Therefore, the present invention has been made in view of the above problems, and it is an LED display system including a control device and an LED display device for displaying an image based on a video signal distributed from the control device. The purpose is to reduce the power consumption of the LED display device.

  The LED display system according to the present invention is an LED display system including a control device and an LED display device that displays an image based on a video signal distributed from the control device. The control device includes an average luminance calculation unit, a correction coefficient calculation unit, and a video signal distribution unit. The average luminance calculation unit calculates an average luminance value of pixels constituting a frame for each frame in the video signal. The correction coefficient calculation unit calculates, based on the average luminance value calculated by the average luminance calculation unit, a luminance correction coefficient for correcting the luminance of the video signal so that the power consumption of the LED display device becomes equal to or less than a predetermined value. . The video signal distribution unit distributes the video signal and the luminance correction coefficient calculated by the correction coefficient calculation unit to the LED display device. The LED display device includes a plurality of LEDs, a brightness controller, and an LED driver. The plurality of LEDs become display pixels. The luminance adjustment unit adjusts the luminance of the video signal based on the luminance correction coefficient distributed from the video signal distribution unit. The LED drive unit drives the plurality of LEDs based on the video signal whose luminance has been adjusted by the luminance adjustment unit.

  According to the present invention, the LED display device generates the video signal based on the luminance correction coefficient for correcting the luminance of the video signal so that the power consumption of the LED display device becomes equal to or less than the predetermined value. The power consumption of the LED display device can be suppressed to a predetermined value or less by adjusting the luminance of the LED.

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram which shows the whole structure of the LED display system which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the LED display apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the control apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the threshold level of the average luminance value which concerns on Embodiment 1 of this invention. It is a figure which shows the setting value of the luminance correction coefficient which concerns on Embodiment 1 of this invention. It is a timing chart of the signal processing in the LED display system concerning Embodiment 1 of the present invention. It is a figure which shows the threshold level of the average luminance value which concerns on Embodiment 2 of this invention. It is a figure which shows the setting value of the luminance correction coefficient which concerns on Embodiment 2 of this invention.

Embodiment 1
<Configuration of LED Display System>
First, the entire configuration of the LED display system 300 according to Embodiment 1 of the present invention will be described. FIG. 1 is a block diagram showing an entire configuration of an LED display system 300 according to Embodiment 1 of the present invention. As shown in FIG. 1, the LED display system 300 includes an LED display device 101 and a control device 200. The LED display device 101 displays an image based on the image signal distributed from the control device 200.

  The LED display device 101 includes a plurality of LED display devices 100, and one screen is configured by a plurality of LED display units 5 (see FIG. 2) respectively included in the plurality of LED display devices 100. In the example of FIG. 1, in the LED display device 101, one screen is configured by the LED display device 100 of a total of 36 units of 6 units in the horizontal direction × 6 units in the vertical direction. Hereinafter, the LED display device 100 is also referred to as a “unit LED unit 100”. Further, the LED display device 101 is also referred to as “LED unit 101”.

  In the present embodiment, the pixel configuration of the unit LED unit 100 is 320 horizontal pixels × 180 vertical pixels, and the LED unit 101 displays FullHD (1920 × 1080 pixels) by the unit LED unit 100 of 36 units.

  The control device 200 distributes a video signal to the LED unit 101 and controls the LED unit 101. In the present embodiment, since the control device 200 controls the plurality of unit LED units 100, the plurality of unit LED units 100 are divided into three groups, and video signals and control signals from the control device 200 are grouped in each group. A daisy chain connection to the LED unit 100 is made. Hereinafter, the control device 200 is also referred to as an “LED control unit”. The method of controlling each unit LED unit 100 by the LED control unit 200 will be described in detail later.

<Configuration of Unit LED Unit>
FIG. 2 is a block diagram showing an example of the configuration of the LED display device (unit LED unit) 100 according to Embodiment 1 of the present invention. As shown in FIG. 2, the unit LED unit 100 includes an image input terminal 2, an image signal processing circuit 3, a frame memory 50, a brightness adjustment unit 9, an LED drive unit 4, an LED display unit 5, a microcomputer 7, a memory 8, And a control terminal 6.

  A video signal from the LED control unit 200 is input to the video input terminal 2. The video signal processing circuit 3 performs signal processing such as selection processing of an area necessary for display from the video signal input from the video input terminal 2 using the frame memory 50. The luminance adjusting unit 9 adjusts the luminance of the video signal subjected to the signal processing in the video signal processing circuit 3 based on a luminance correction coefficient distributed from the LED control unit 200 described later.

  The LED drive unit 4 PWM drives the LED display unit 5 based on the video signal whose luminance is adjusted by the luminance adjustment unit 9. The LED display unit 5 is configured by arranging the LEDs 1 as display pixels in a matrix of 320 horizontal pixels × 180 vertical pixels. The LED 1 includes three red (R), green (G) and blue (B) LEDs per pixel. The LED display unit 5 is driven by the LED drive unit 4 based on the video signal to display a video.

  The control terminal 6 is an input / output terminal for communication control signals between the LED control unit 200 and the unit LED unit 100. The memory 8 stores, for example, a luminance correction coefficient distributed from the LED control unit 200 described later. The microcomputer 7 controls the video signal processing circuit 3 and the LED drive unit 4 and performs read and write control to the memory 8.

<Configuration of LED Control Unit>
FIG. 3 is a block diagram showing an example of the configuration of a control device (LED control unit) 200 according to Embodiment 1 of the present invention. As shown in FIG. 3, the LED control unit 200 includes a video input terminal 10, a video signal processing circuit 11, a video signal distribution unit 14, a memory 15, a control circuit 13, video output terminals 17, 18 and 19, and a control terminal 21. 22, 23 and an external terminal 20.

  A video signal from an external device such as a PC is input to the video input terminal 10. The video signal processing circuit 11 performs video signal processing such as gamma correction of the video signal input from the video input terminal 10. The video signal distribution unit 14 divides the video signal subjected to the signal processing in the video signal processing circuit 11 and distributes the video signal to the LED unit 101 through the video output terminals 17 to 19.

  The memory 15 is, for example, a nonvolatile or volatile semiconductor memory such as a RAM, a ROM, a flash memory, an EPROM, an EEPROM, a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a DVD or the like. In the memory 15, for example, a program for controlling each component of the LED control unit 200 is stored. The memory 15 has a reference table 16 used when the correction coefficient calculation unit 25 described later calculates the luminance correction coefficient.

  The control circuit 13 includes an average luminance calculation unit 24, a correction coefficient calculation unit 25, an external communication unit 26, a communication unit 27, and a setting unit 28.

  The average luminance calculation unit 24 calculates an average luminance value of pixels constituting a frame for each frame in the video signal subjected to the signal processing in the video signal processing circuit 11. The correction coefficient calculation unit 25 refers to the reference table 16 based on the average luminance value calculated by the average luminance calculation unit 24 and corrects the luminance of the video signal so that the power consumption of the LED unit 101 becomes equal to or less than a predetermined value. To calculate the luminance correction coefficient to The operations of the average luminance calculator 24 and the correction coefficient calculator 25 will be described in detail later.

  The external communication unit 26 receives, via the external terminal 20, a control signal for controlling the LED control unit 200 and the unit LED unit 100 input from an external device such as a PC. The communication unit 27 transmits and receives control signals to and from the unit LED unit 100 via the control terminals 21 to 23. The setting unit 28 sets, in the reference table 16, setting values received from the external device or the like and received by the external communication unit 26.

  Each function of the average luminance calculating unit 24, the correction coefficient calculating unit 25, the external communication unit 26, the communication unit 27, and the setting unit 28 is realized by the control circuit 13. The control circuit 13 is a CPU (Central Processing Unit, central processing unit, processing unit, arithmetic unit, microprocessor, microcomputer, processor, DSP) that executes programs stored in the memory 15 even if it is dedicated hardware. Say).

  When the control circuit 13 is dedicated hardware, the control circuit 13 corresponds to, for example, a single circuit, a complex circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof. . The functions of the respective units of the average brightness calculation unit 24, the correction coefficient calculation unit 25, the external communication unit 26, the communication unit 27, and the setting unit 28 may be realized collectively by the control circuit 13, or the functions of the respective units are processed differently. It may be realized by a circuit.

  When the control circuit 13 is a CPU, each function of the average luminance calculating unit 24, the correction coefficient calculating unit 25, the external communication unit 26, the communication unit 27, and the setting unit 28 is realized by software, firmware, or a combination of software and firmware Be done. Software and firmware are described as a program and stored in the memory 15. The control circuit 13 realizes the functions of the respective units by reading and executing the program stored in the memory 15. In addition, it can be said that this program causes a computer to execute the procedures and methods of the average luminance calculation unit 24, the correction coefficient calculation unit 25, the external communication unit 26, the communication unit 27, and the setting unit 28.

  A part of each function of average brightness calculation unit 24, correction coefficient calculation unit 25, external communication unit 26, communication unit 27, and setting unit 28 is realized by dedicated hardware, and a part is performed by software or firmware. It may be realized.

<Method to correct the brightness of LED>
Next, the luminance correction method of the LED 1 in the LED display system 300 according to the present embodiment will be described in detail.

  As shown in FIG. 1, when configuring the LED display system 300 including the LED control unit 200 and the LED unit 101 configured by the unit LED unit 100 of 36 units, the LED control unit 200 individually performs the unit LED unit 100. In order to control the ID, an ID number is set in each unit LED unit 100. In the example of FIG. 1, ID = 1 to 36 are set to the unit LED unit 100 of 36 units.

  Further, in the example of FIG. 1, the LED unit 101 is a group of unit LED units 100 of ID = 1 to 12, a group of unit LED units 100 of ID = 13 to 24, a unit LED unit 100 of ID = 25 to 36. The three unit LED units 100 of ID = 6, ID = 18, and ID = 30 are connected to the LED control unit 200.

  Specifically, the video output terminals 17 to 19 of the LED control unit 200 are connected to the video input terminal 2 of the unit LED unit 100 of ID = 6, 18 and 30, respectively. Similarly, the control terminals 21 to 23 of the LED control unit 200 are connected to the control terminal 6 of the unit LED unit 100 of ID = 6, 18 and 30, respectively.

  As shown in FIG. 3, in the LED control unit 200, the video signal input from the video input terminal 10 is subjected to processing such as gamma correction by the video signal processing circuit 11 and converted to the resolution of the LED unit 101 to be the output destination. Be done. In this embodiment, this resolution is 1920 × 1080 pixels (Full HD).

  After the video signal processed by the video signal processing circuit 11 is divided into three areas of 640 × 1080 pixels by the video signal distribution unit 14, the ID = 1 to 12, 13 to 24, 25 respectively. It is distributed to three groups of ̃36 unit LED units 100.

  The video signal processed by the video signal processing circuit 11 is distributed to the LED unit 101 by the video signal distribution unit 14, and at the same time, the average luminance value of the pixels constituting the frame for each frame is calculated by the average luminance calculation unit 24. It is calculated.

<Method of calculating average luminance value>
Hereinafter, the method of calculating the average luminance value will be described in detail. In the present embodiment, as described above, the resolution of the video signal processed by the video signal processing circuit 11 is 1920 × 1080 pixels. The luminance value of each color of R, G, B is output to each pixel. The upper left coordinates of the display screen of the LED unit 101 are (h, v) = (1, 1), and the lower right coordinates are (h, v) = (1920, 1080). The luminance value of each color of R, G, B for each pixel Let Yr (h, v), Yg (h, v), Yb (h, v) represent.

  The average luminance calculation unit 24 calculates a sum Yrall of luminance values of R pixels in the pixels (1920 × 1080 pixels) constituting the frame and a sum Ygall of luminance values of G pixels and a luminance of B pixels according to the following equation (1). Calculate the sum Yball of values.

  Further, from the equation (1), the total value Yall of the luminance values of all the pixels is calculated by the following equation (2).

  Then, from the equation (2), the average luminance value Yave of the pixels constituting the frame is calculated by the following equation (3).

  The average luminance value Yave of the pixels constituting the frame for one frame can be obtained by the above formulas (1) to (3). At this time, luminance values Yr (1920, 1080), Yg (1920, 1080), and Yb (1920, 1080) of final pixels for one frame have already been distributed to the LED unit 101.

  In Equations (1) to (3), after adding the results of adding the luminance values of each of R, G, and B for one frame for three colors, the average luminance value Yave is determined by dividing by the total number of pixels. However, the method of calculating the average luminance value Yave is not limited to this. For example, the luminance value of each of R, G, B colors is added for each horizontal line, and the average luminance value for one horizontal line is calculated by dividing by 1920, and the value obtained by adding these for one frame is divided by 1080 vertical lines The calculation efficiency of the average luminance calculation unit 24 can be improved by a method such as the above.

  Here, it is assumed that the luminance values Yr (h, v), Yg (h, v) and Yb (h, v) of each of R, G and B colors are 8 bits (= 256 gradations: values of 0 to 255) Then, the average luminance value Yave for one frame has a value of 0 to 765. In this embodiment, the case where Yr (h, v), Yg (h, v), Yb (h, v) have 8 bits and the average luminance value Yave has a value of 0 to 765 will be described as an example. .

  The power control adjustment value P is stored in the reference table 16. The power control adjustment value P can be set in advance, for example, by the user inputting a set value from the external terminal 20.

  The power control adjustment value P, when all pixels are lit at the maximum luminance value (R = 255, G = 255, B = 255), that is, the maximum power consumption of the all white full bit signal which is the product rated value. On the other hand, it is set about what percentage or less can be used. For example, they are set in five steps such as P1 = 100%, P2 = 87.5%, P3 = 75%, P4 = 62.5%, P5 = 50%.

  The correction coefficient calculation unit 25 calculates the luminance correction coefficient Cy to be distributed to the LED unit 101 based on the power control adjustment value P set in the reference table 16 and the average luminance value Yave calculated for each frame.

  More specifically, when P3 is selected as the power control adjustment value P, for example, the correction coefficient calculation unit 25 calculates 573.7 which is 75% of the maximum value 765 that the average luminance value Yave can take. As a threshold value, a luminance correction coefficient Cy is selected which reduces the average luminance Yave of one frame to a threshold value or less when the average luminance value Yave for each frame exceeds 573.7.

<Method of calculating luminance correction coefficient>
Hereinafter, the method of calculating the luminance correction coefficient Cy will be described in more detail. FIG. 4 is a diagram showing an example of five threshold levels Th_L of Th1 to Th5 set for the average luminance value Yave in the first embodiment of the present invention. FIG. 5 is a diagram showing an example of the luminance correction coefficient Cy set for each of the threshold levels Th_L = Th1 to Th5 set in five steps for each of the power control adjustment values P = P1 to P5. is there.

  The setting values shown in FIGS. 4 and 5 are stored in the reference table 16, and the correction coefficient calculation unit 25 is preset with the average luminance value Yave for each frame calculated by the average luminance calculation unit 24. By referring to the lookup table 16 based on the power control adjustment value P, the value of the luminance correction coefficient Cy can be obtained for each frame.

  For example, when P3 = 75% is selected as the power control adjustment value P, the average luminance value Yave is smaller than 573.7, that is, as shown in FIG. When Th_L = Th3 to Th5, the power consumption of the LED unit 101 does not exceed 75% of the maximum power consumption. That is, since it is not necessary to correct the luminance of the video signal, as shown in FIG. 5, the luminance correction coefficient Cy of the threshold levels Th_L = Th3 to Th5 at the power control adjustment value P = P3 is 100%. ing.

  On the other hand, when the average luminance value Yave is 573.7 or more, the power consumption of the LED unit 101 is 75% or more of the maximum power consumption, so it is necessary to correct the luminance of the LED. Specifically, when the average luminance value Yave is 573.7 ≦ Yave <669.3, that is, as shown in FIG. 4, when the threshold level Th_L = Th2, the power consumption of the LED unit 101 is the maximum power consumption. The luminance correction coefficient Cy at the threshold level Th_L = Th2 at the power control adjustment value P = P3 is 85.7% (= 100 × 573.7), as shown in FIG. /669.3).

  Similarly, when the average luminance value Yave is 669.3 ≦ Yave ≦ 765, that is, when Th_L = Th1, the power control adjustment value is set such that the power consumption of the LED unit 101 is smaller than 75% of the maximum power consumption. The luminance correction coefficient Cy of the threshold level Th_L = Th1 at P = P3 is 75% (= 100 × 573.7 / 765).

  In the above description, in order to simplify the calculation, only the power consumption of the LED 1 is considered as the power consumption of the LED unit 101, and the average luminance value Yave in the video signal is less than a predetermined ratio with respect to the maximum luminance value. In the above case, it has been described that the power consumption of the LED unit 101 is equal to or less than the predetermined ratio of the maximum power consumption. More specifically, the luminance correction coefficient Cy is the power consumption of components other than the LED 1 Set in consideration.

<Signal processing timing>
Hereinafter, the timing of signal processing in the LED display system 300 according to Embodiment 1 of the present invention will be described in detail. FIG. 6 is a timing chart of signal processing in the LED display system 300 according to Embodiment 1 of the present invention.

  As described above, in order to calculate the average luminance value Yave for one frame, a video signal for one frame is required. However, the video signal output from the video signal processing circuit 11 has the average luminance calculator 24 and It is simultaneously input to the video signal distribution unit 14 in time series. Therefore, when the luminance correction coefficient Cy for one frame is determined, the video signal is distributed to the LED unit 101 via the video signal distribution unit 14.

  Thus, the luminance correction coefficient Cy is the head of the frame following the frame for which the average luminance value Yave has been obtained in the video signal, that is, Yr (1,1), Yg (1,1), Yb (1,1). And is distributed to the LED unit 101 via the video signal distribution unit 14. That is, the luminance correction coefficient Cy is distributed to the LED unit 101 side in such a manner as to delay the video signal by one frame.

  In the video signal processing circuit 3 of the unit LED unit 100 of ID = 1 to 12, as the video signal of the n (n is an integer of 1 or more) frame, Yr (n) (h, v), Yg (n) (h, v) , Yb (n) (h, v) from (h, v) = (1, 1) to (640, 1080) in sequence. Further, the video signal processing circuit 3 selects a portion to be displayed from the distributed video signal according to its own ID number stored in the memory 8.

  Specifically, for example, in the unit LED unit 100 of ID = 1, the signal region of (h, v) = (1, 1) to (320, 180) is selected by the video signal processing circuit 3. Similarly, in the unit LED unit 100 of ID = 2, the signal area of (h, v) = (1, 181) to (320, 360) is identical to that of the unit LED unit 100 of ID = 3 (h, v) = ( The signal area of 1,361) to (320, 540) has the signal area of (h, v) = (1, 541) to (320, 720) in the unit LED unit 100 of ID = 4. The signal area of (h, v) = (1, 721) to (320, 900) in the unit LED unit 100 is (h, v) = (1, 901) to (320) in the unit LED unit 100 of ID = 6. , 1080) are selected respectively.

  Further, in the unit LED unit 100 of ID = 7, the signal regions of (h, v) = (321, 1) to (640, 180) are selected by the video signal processing circuit 3. Similarly, in the unit LED unit 100 of ID = 8, the signal area of (h, v) = (321, 181) to (640, 360) is identical to that of the unit LED unit 100 of ID = 9 (h, v) = ( In the unit LED unit 100 of ID = 10, the signal regions of (h, v) = (321, 541) to (640, 720) have ID = 11. The signal area of (h, v) = (3211, 721) to (640, 900) in the unit LED unit 100 is (h, v) = (321, 901) to (640) in the unit LED unit 100 of ID = 12. , 1080) are selected respectively.

  The same process is performed in the unit LED unit 100 of ID = 13-24 and ID = 25-36.

  Further, in the LED driving unit 4, it is necessary to control the LED display unit 5 by PWM driving the video signal in time division. Therefore, the video signal processing circuit 3 rearranges the video signals input in time series to the timing required by the LED drive unit 4 via the frame memory 50. That is, in the video signal processing circuit 3, a delay of one frame occurs when the video signals are rearranged.

  The video information of the (n + 1) th frame is distributed from the video signal distribution unit 14 of the LED control unit 200 to the video signal processing circuit 3 of the unit LED unit 100. A luminance correction coefficient Cy (n) is added to the signal.

  In the unit LED unit 100, the microcomputer 7 reads the luminance correction coefficient Cy (n) for the above-mentioned nth frame, and the video signal processing circuit 3 delays the luminance signal for one frame and outputs the luminance correction coefficient Cy. The luminance adjustment unit 9 compares the luminance values Yr (n) (h, v), Yg (n) (h, v), Yb (n) (h, v) of the nth frame for which (n) is calculated. Luminance correction is performed by the following equation (4).

  Here, Yro (n), Ygo (n), and Ybo (n) indicate the luminance values of the video signal whose luminance has been adjusted by the luminance adjustment unit 9. The luminance values Yro (n), Ygo (n) and Ybo (n) are output to the LED drive unit 4, and the LED drive unit 4 is based on the luminance values Yro (n), Ygo (n) and Ybo (n). , Drive the LED display unit 5.

  In the above example, the luminance correction coefficient Cy is delayed by one frame with respect to the video signal in the LED control unit 200, and the video signal is delayed by one frame by the frame memory 50 in the unit LED unit 100. Although the case where the timing of the luminance correction coefficient Cy and the video signal are matched has been described as an example, the delay amount need not necessarily be one frame, and the video signal input to the unit LED unit 100 and the luminance correction coefficient Cy The delay amount may be two or more frames as long as control is made to coincide with time.

  As described above, in order to calculate the average luminance value Yave for one frame, since a video signal for one frame is required, a delay for one frame occurs. Therefore, in order to distribute the luminance correction coefficient Cy and the video signal at the same timing, it is necessary to delay the video signal by one frame in the LED control unit 200. However, in the present embodiment, even if the video signal is delayed in the LED control unit 200, the luminance correction coefficient can be obtained by using the delay in the signal processing in the video signal processing circuit 3 in the unit LED unit 100. The timing of Cy and the video signal are matched. Thus, power control can be performed in frame units without adding a frame memory in the LED control unit 200.

  That is, the average luminance value Yave is calculated for each frame by the LED control unit 200, and the luminance correction coefficient Cy selected from the average luminance value Yave and the desired power control adjustment value P is added to the head of the video signal of the next frame. The unit LED unit 100 uses the luminance correction coefficient Cy added to the head of the video signal of the next frame while delaying one frame to perform the clipping processing of the distributed video signal, etc. By adjusting the brightness of the video signal of the frame for which the correction coefficient Cy has been calculated, it is possible to set the power consumption below the desired power control adjustment value P for each frame.

  Therefore, even when a video signal whose power consumption is instantaneously increased is input, the power consumption can be reduced in frame units, and the LED display system can always reduce power consumption below a certain level. Since it becomes possible to control 300, it is not necessary to lower the luminance unnecessarily even for a video signal whose power consumption is not large, and it is possible to minimize the reduction in luminance of the entire LED display system 300. .

  Here, in the case of calculating the average luminance value Yave in the unit LED unit and performing the above-mentioned power saving control, in the case where a plurality of unit LED units display an image, for example, in the case of configuring one screen by a plurality of unit LED units In this case, since power saving control is performed for each unit LED unit, only part of the unit LED units may reduce the brightness due to the power saving control, and the brightness of the entire screen may not be uniform. However, according to the LED display system 300 according to the present embodiment, since power saving control can be performed on the entire display screen of the LED unit 101, the luminance of only a part of the screen does not decrease, and the entire display screen The brightness uniformity of is maintained.

Second Embodiment
FIG. 7 is a diagram showing an example of the threshold level Th_L of the average luminance value Yave in the LED display system according to Embodiment 2 of the present invention. FIG. 8 shows luminances set for each of ten threshold levels Th_L = Th1 to Th10 for each of the power control adjustment values P = P1 to P5 in the LED display system according to Embodiment 2 of the present invention. It is a figure which shows an example of the correction coefficient Cy. As shown in FIG. 7, in the present embodiment, ten threshold levels of Th_L = Th1 to Th10 are set for the average luminance value Yave. On the other hand, as shown in FIG. 8, in the present embodiment, the luminance correction coefficient Cy to be transmitted to the LED unit 101 is set to five steps at the maximum.

  Specifically, a method of correcting the luminance of the LED in the LED display system according to the present embodiment will be described. In the following, only portions different from the LED display system 300 according to the first embodiment will be described.

  Based on the average luminance value Yave (n) of the nth frame, Th_L (n) shown in FIG. 7 is determined. If Yave (n) = 600, then Th_L (n) = Th4. Next, the threshold level Th_L (n + 1) is similarly determined according to the average luminance value Yave (n + 1) of the n + 1 th frame, and the determination threshold level Th_L is determined according to the step difference between Th_L (n) and Th_L (n + 1). Determine '(n + 1).

  More specifically, if the step difference between the threshold levels of Th_L (n) and Th_L (n + 1) is within ± 1, then Th_L ′ (n + 1) = Th_L (n), and otherwise Th_L. It is assumed that '(n + 1) = Th_L (n + 1). For example, if Yave (n + 1) = 650, Th_L (n + 1) = Th3 and Th_L '(n + 1) = Th4 remains, and if Yave (n + 1) = 500, Th_L (n + 1) = Th6 and Th_L' (n + 1) = It becomes Th6.

  Next, the luminance correction coefficient Cy to be transmitted to the LED unit 101 is calculated from the determination threshold level Th_L ′ and the power control adjustment value P. FIG. 8 shows an example of obtaining the luminance correction coefficient Cy from the determination threshold level Th_L '. For example, when the power control adjustment value P = P3 is selected, if Th_L '(n + 1) = Th3, then Cy (n + 1) = 85.7% as shown in FIG.

  That is, the average luminance value Yave is calculated for each frame by the LED control unit 200, and the average luminance value Yave is classified into 2 n (n is an integer of 1 or more) steps of threshold level Th_L from this average luminance value Yave. Compare with the threshold level of the immediately preceding frame, reflect the luminance correction coefficient Cy delivered to the LED unit 101 when the threshold level Th_L changes by two or more steps, and deliver it to the LED unit 101 By setting the luminance correction coefficient Cy to n steps at the maximum, in the case where there is almost no change in luminance such as a still image and the average luminance value Yave of the video signal is in the vicinity of the threshold, the luminance correction coefficient Cy is By changing frequently, it can suppress that the display of the LED display part 5 flickers.

  In the above example, the average luminance value Yave for each frame is divided into 10 levels, and the luminance correction coefficient Cy to be transmitted to the LED unit 101 is 5 levels at maximum, but the average luminance value Yave is 10 levels. The luminance correction coefficient Cy to be transmitted to the LED unit 101 is updated only when Th_L changes by two or more steps, with the luminance correction coefficient Cy at a maximum of 10 steps, and Cy is not changed when the change of Th_L is one step or less Control may be performed. Even in this case, flicker can be suppressed as described above.

  In the present invention, within the scope of the invention, each embodiment can be freely combined, or each embodiment can be appropriately modified or omitted.

  DESCRIPTION OF SYMBOLS 1 LED, 2, 10 image input terminal 3, 11 video signal processing circuit, 4 LED drive part, 5 LED display part, 6, 21-23 control terminal, 7 microcomputer, 8, 15 memory, 9 brightness adjustment part, 13 Control circuit, 14 video signal distribution unit, 16 reference table, 17-19 video output terminals, 20 external terminals, 24 average luminance calculation unit, 25 correction coefficient calculation unit, 26 external communication unit, 27 communication unit, 28 setting unit, 50 Frame memory, 100 LED display unit (unit LED unit), 101 LED display unit (LED unit), 200 control unit (LED control unit), 300 LED display system.

Claims (7)

An LED display system comprising: a control device; and an LED display device for displaying an image based on a video signal distributed from the control device,
The controller is
An average luminance calculator configured to calculate an average luminance value of pixels constituting a frame of each frame in the video signal;
A correction coefficient for calculating a luminance correction coefficient for correcting the luminance of the video signal so that the power consumption of the LED display device becomes equal to or less than a predetermined value based on the average luminance value calculated by the average luminance calculation unit A calculation unit,
And a video signal distribution unit for distributing the video signal and the luminance correction coefficient calculated by the correction coefficient calculation unit to the LED display device.
The LED display device is
Multiple LEDs that become display pixels,
A luminance adjustment unit that adjusts the luminance of the video signal based on the luminance correction coefficient distributed from the video signal distribution unit;
An LED display system comprising: an LED drive unit that drives the plurality of LEDs based on the video signal whose luminance has been adjusted by the luminance adjustment unit. The LED display system according to claim 1, wherein
A plurality of the LED display devices display video based on the video signal distributed from the control device,
The correction coefficient calculation unit corrects the luminance of the video signal such that the power consumption of the plurality of LED display devices is equal to or less than a predetermined value, based on the average luminance value calculated by the average luminance calculation unit. Calculate the brightness correction factor of
An LED display system, wherein a video signal distribution unit distributes the video signal and the luminance correction coefficient calculated by the correction coefficient calculation unit to each of the plurality of LED display devices. The LED display system according to claim 1 or 2, wherein
The video signal distribution unit adds the luminance correction coefficient calculated by the correction coefficient calculation unit to the head of the video signal after a predetermined frame from the frame for which the luminance correction coefficient is calculated, to the LED display device. Deliver
The LED display device includes a video signal processing unit that performs signal processing of the video signal distributed from the video signal distribution unit,
The video signal is delayed by the predetermined frame in the video signal processing unit,
The LED display system, wherein the brightness adjustment unit adjusts the brightness of a frame for which the brightness correction coefficient is calculated in the video signal delayed by the predetermined frame in the video signal processing unit based on the brightness correction coefficient. The LED display system according to any one of claims 1 to 3, wherein
The control device sets an n-stage (n is an integer of 1 or more) threshold level set in advance with respect to the average luminance value, and the luminance correction coefficient for each of the n-stage threshold levels. Have a reference table,
The LED display system, wherein the correction coefficient calculation unit calculates the luminance correction coefficient by referring to the reference table based on the average luminance value calculated by the average luminance calculation unit. The LED display system according to claim 4, wherein
The correction coefficient calculation unit
When the average luminance value of the current frame in the video signal is changed by two or more steps at the threshold level of n steps from the average luminance value of the immediately preceding frame, the luminance correction coefficient is changed ,
The luminance correction coefficient is not changed when the average luminance value of the current frame in the video signal is changed by only one step at the threshold level of n steps from the average luminance value of the immediately preceding frame. , LED display system. The LED display system according to any one of claims 1 to 3, wherein
The control device is configured to: preset 2n (n is an integer of 1 or more) threshold levels preset for the average brightness value; and n the brightness correction coefficients for the 2n threshold levels Have a reference table set up,
The correction coefficient calculation unit calculates the brightness correction coefficient by referring to the reference table based on the average brightness value calculated by the average brightness calculation unit.
If the average luminance value of the current frame in the video signal is changed by two or more steps at the threshold level of 2n steps from the average luminance value of the immediately preceding frame, the luminance correction coefficient is changed ,
The luminance correction coefficient is not changed when the average luminance value of the current frame in the video signal is changed by only one step at the threshold level of 2n steps from the average luminance value of the immediately preceding frame. , LED display system.   The LED display apparatus in the LED display system as described in any one of Claims 1-6.

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