JP2015087709A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device in which display operation can be controlled by consumption power matched with power supply capability on a setting side.SOLUTION: A display device includes: a display panel DP in which self-luminous elements EL are arranged in a matrix shape on a substrate; and a control unit CNTL that controls light emission of the self-luminous elements on the basis of video data to be input. The control unit recognizes current consumption power of the display panel, and when the current consumption power is equal to or greater than a first limit value Min, performs control so that video data of lower gradation than gradation of the video data to be input are displayed.

Description

  Embodiments described herein relate generally to a display device.

  In recent years, the demand for flat display devices typified by liquid crystal display devices has been rapidly increased by taking advantage of the features of thinness, light weight, and low power consumption. Among them, an active matrix display device in which each pixel is provided with a pixel switch having a function of electrically separating an on-pixel and an off-pixel and holding a video signal to the on-pixel includes various types of information including portable information devices. It is used for the display.

  As such a flat-type active matrix display device, an organic EL display device using a self-luminous element has attracted attention, and research and development have been actively conducted. The organic EL display device has characteristics that it does not require a backlight, is suitable for moving image reproduction because of high-speed responsiveness, and is suitable for use in a cold region because the luminance does not decrease at low temperatures.

  By the way, in the organic EL display device, the higher the display luminance in the screen, the more power is consumed. Therefore, various techniques for reducing power consumption have been proposed. For example, in the technique described in Patent Document 1, power consumption is reduced by reducing the luminance of a portion of the screen that is difficult for the viewer to notice, but at this time, the image is not generated so that the viewer does not feel uncomfortable. A technique capable of reducing power consumption while maintaining a sense of contrast is disclosed.

JP 2011-2520 A

  By the way, the normal mode is that the side supplying the display device (manufacturer) is different from the side manufacturing the set incorporating the supplied display device (manufacturer). However, the conventional display device has not been provided with a function of executing power control in a flexible manner corresponding to the power supply capability on the set side. Therefore, conventionally, it is necessary to design the power supply capacity on the set side corresponding to the power consumption of the display device, or it is necessary to design the power of the display device so as to be within the power supply capability on the set side.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a display device capable of controlling a display operation with power consumption in accordance with the power supply capability on the set side.

  One aspect of the present invention includes a display panel in which self-light-emitting elements are arranged in a matrix on a substrate, and a control unit that controls light emission of the self-light-emitting elements based on input video data. Grasps the current power consumption of the display panel, and when the current power consumption is equal to or higher than the first limit value, displays video data having a gradation lower than the gradation of the input video data. The display device is controlled as follows.

It is a figure which shows the structure of the display apparatus and display part (pixel circuit) of 1st Embodiment. It is a figure for demonstrating operation | movement of the electric power limit function of the display apparatus in 1st Embodiment. It is a figure for demonstrating operation | movement of the electric power limit function of the display apparatus in 1st Embodiment. It is a figure which shows the structure of the controller which performs the electric power limit function of the display apparatus in 1st Embodiment. It is a flowchart which shows the process sequence of the electric power limit part of the display apparatus in 1st Embodiment. It is a figure which shows the process which calculates | requires the real-time electric power of the display apparatus in 1st Embodiment. It is a figure which shows the data structure of the power memory of the display apparatus in 1st Embodiment. It is a flowchart which shows the process sequence of the brightness | luminance control part of the display apparatus in 1st Embodiment. It is a figure which shows the operation timing of the electric power limit function in the display apparatus of 1st Embodiment.

[First Embodiment]
FIG. 1 is a diagram illustrating a configuration of a display device and a display unit (pixel circuit) according to the first embodiment. As shown in FIG. 1, the display device according to the present embodiment is configured as an active matrix display device, and includes a display panel DP and a controller CNTL that controls the operation of the display panel DP.

  The display panel DP includes a display unit on a glass substrate which is an insulating substrate having light transmittance. The display portion is provided with a plurality of gate lines SG extending along the row direction and a plurality of signal lines SL extending along the column direction, and each of the gate lines SG and the signal lines SL surrounded by the gate lines SG and the signal lines SL is provided. In the region, an EL (Electroluminescence) element that emits light of each color of RGB and a pixel circuit that drives each EL element are provided. Note that the resolution of the display device shown in FIG. 1 is 720 RGB × 1280 lines.

  The pixel circuit shown in FIG. 1 is illustrated in a simplified manner for explaining the basic operation. The pixel circuit includes a pixel switch SST, a drive transistor DRT, and an auxiliary capacitor Cs.

  In the pixel circuit, the first terminal of the drive transistor DRT is electrically connected to the high potential power supply line Pvdd (high potential power supply), and the second terminal of the drive transistor DRT is connected to the control terminal of the drive transistor DRT via the auxiliary capacitor Cs. Connect electrically. The second terminal of the drive transistor DRT is electrically connected to the anode electrode of the EL element, and the cathode electrode of the EL element is electrically connected to the low potential power supply line Pvss (low potential power supply).

  The first terminal of the pixel switch SST is electrically connected to the signal line SL, the second terminal of the pixel switch SST is electrically connected to the control terminal of the driving transistor DRT, and the control terminal of the pixel switch SST is the gate line. It is electrically connected to SG.

  Here, the gate lines SG are driven by SG scanning circuits arranged on the left and right of the display unit, and the signal lines SL are driven by a controller CNTL arranged at the lower part of the display panel DP. The controller CNTL is provided in a system driver IC described later.

  A flexible printed circuit board (FPC) is provided at the end of the display panel DP, and video signals, synchronization signals, various command signals, and the like are communicated with the set-side system via the flexible printed circuit board. The system driver IC receives these signals and generates a control signal to the SG scanning circuit, and D / A converts the digital video signal to supply an analog video signal Vsig to the signal line SL.

  Since the n-th gate line SG (n) is set to the high level “H”, the connected pixel switch SST becomes conductive, and the video signal Vsig output from the system driver IC is written in the auxiliary capacitor Cs. As a result, the EL driving transistor DRT is turned on and a current flows between Pvdd and Pvss which are EL power sources, so that the EL element emits light. The magnitude of the current flowing at this time corresponds to the potential of the auxiliary capacitor Cs, that is, the video signal Vsig.

  The brightness of the EL element is proportional to the value of the current flowing through the EL element, and the EL current is controlled by the video signal Vsig. Therefore, as the voltage of the video signal Vsig is higher, the EL current increases and the EL element emits light brighter. Therefore, the higher the luminance of the EL element, the more power is consumed. Here, the power supply voltages Pvdd and Pvss for causing the EL element to emit light are directly supplied from the set side, or are generated inside the display device from another power source supplied from the set side. In addition, the power supply capacity on the set side may be limited by various factors such as the product size or battery duration, the amount of heat generated by the set, and there may be cases where it is not possible to supply enough power to light up the EL element. . In any case, it is necessary to control the power of the display device so as to be within the power supply capability on the set side.

  Next, a power control method in the display device of this embodiment will be described. In the present embodiment, a power limit function is provided on the display device side so that the display device can be driven within the range of power supply capacity on the set side.

  FIG. 2 is a diagram for explaining the operation of the power limit function of the display device according to the first embodiment.

  FIG. 2A shows an input image and a display image. Here, the input image is an image of video data sent from the set side, and the display image is an image displayed when the power limit function is applied to the input image. FIG. 2B shows a time transition of power consumed by the display device when the above-described display image is displayed. FIG. 2C shows a time transition of the parameter Gain (gain) used for the power limit function.

  In the first embodiment, “power limit Max” and “power limit Min” are provided as power thresholds when executing the power limit function. “Power limit Max” is a maximum value of power that is allowed to be used in the display device, and is a value corresponding to the power supply capacity on the set side. “Power limit Min” is a power value that gives the timing at which the display device starts limit control. When the power of the display device exceeds the “power limit Min”, the display device controls the video signal Vsig so that the power does not exceed the “power limit Max”.

  Since the input image of the first frame is a dark image, the power consumption is lower than the power limit Min. Therefore, image data obtained by multiplying the input image by Gain = 1 is used as the display image. That is, the input image is displayed as it is. Next, when the input image is switched to a bright image in the second frame, the power consumption increases rapidly as the display image is sequentially scanned and replaced with a bright image. The power limit Min is reached.

  When the power consumption exceeds the power limit Min, the controller CNTL uses the input data R_in / G_in / B_in sent from the set side as the display data. Therefore, after that, an image darker than the input image is displayed and the increase in power becomes moderate.

  In the next third frame, the value obtained by integrating the input image data of the previous frame (second frame) over one frame period is converted into power, and the value is less than 1 so that the value does not exceed the power limit Min value. The image data multiplied by Gain is displayed. In this way, an image obtained by multiplying the input image of the third frame by a gain less than 1 in advance is used as a display image, so that an image darker than the input image is displayed.

  FIG. 3 is a diagram for explaining the operation of the power limit function of the display device according to the first embodiment. FIG. 3 shows the operation when the input images (video data) sent from the set side are the same, but the power limit value is set lower than in the case of FIG.

  In the second frame, after the power consumption exceeds the power limit Min, the increase in power is moderated by multiplying the input image data by Gain less than 1, but the power consumption continues to rise and the power limit Max value is increased. To exceed. When the power consumption exceeds the power limit Max value, the image data is masked to black in the subsequent display lines (the image data is converted to black level “L” data) to prevent further increase in power. To stop the light emission of the EL element. For this reason, a black display region is generated in the display image.

  In the next third frame, the value obtained by integrating the input video data of the previous frame (second frame) over one frame period is converted into power, and the value is less than 1 so that the value does not exceed the power limit Min value. The video data multiplied by Gain is displayed. As described above, an image obtained by multiplying the input image of the third frame by Gain in advance is used as a display image, so that an image darker than the input image is displayed.

  Next, the operation of the power limit function will be described in detail.

  FIG. 4 is a diagram illustrating a configuration of the controller CNTL that executes the power limit function of the display device according to the first embodiment. The controller CNTL includes a power limit unit 10, a brightness control unit 11, a control constant table 20, a power memory 21, and a buffer memory 22.

  The power limit unit 10 processes the video input data RGB_in input from the set side to obtain LimitMaxFlg (existence flag for exceeding the power limit Max), Gain_next (gain of the next frame), and Gain_now (gain of the current frame). And output as processing data to the luminance control unit 11. The brightness control unit 11 uses the processing data output from the power limit unit 10 to process the video input data RGB_in to obtain video output data RGB_out. This video output data RGB_out corresponds to the video signal Vsig. Further, the luminance control unit 11 obtains a gain and outputs it to the power limit unit 10.

  The power limit unit 10 refers to the data stored in the control constant table 20 and the power memory 21 when processing the video input data RGB_in.

  The control constant table 20 stores “power conversion coefficient”, “power limit Max”, and “power limit Min” as constants. These values are determined based on the power supply capability on the set side. These values are configured to be rewritable.

  The power memory 21 stores a power value for each line of the currently displayed screen. The buffer memory 22 stores temporary data used when the power limit unit 10 executes processing.

  FIG. 5 is a flowchart illustrating a processing procedure of the power limit unit 10 of the display device according to the first embodiment. The power limit unit 10 can also be configured as a processing block that realizes a processing procedure described below.

  In step S01, every time one line of video input data RGB_in is input, the power limit unit 10 calculates the sum (Rline, Gline, Bline) of each color of one line of R / G / B digital data according to the equation (1). Ask. Here, RGB_in is gradation data.

Rline = ΣRin (1 to 720 dots)
Gline = ΣGin (1 to 720 dots)
Bline = ΣBin (1 to 720 dots) ・ ・ ・ Formula (1)
In step S02, the power limit unit 10 converts the sum of each color into the power (Rpower, Gpower, Bpower) of each color according to the equation (2). The power conversion coefficients Rc, Gc, and Bc are determined based on the light emission efficiency of each color EL element.

Rpower = Rline * Power conversion factor Rc
Gpower = Gline * Power conversion factor Gc
Bpower = Bline * Power conversion coefficient Bc (2)
And the electric power limit part 10 calculates | requires line electric power (line_power) by adding the electric power of each color according to Formula (3).
line_power = Rpower + Gpower + Bpower (3)
[Calculation of next frame gain (Gain_next)]
In steps S05 and S06, the power limit unit 10 calculates Gain_next (gain of the next frame).

In step S05, the power limit unit 10 integrates the line power line_power over one frame period to obtain one screen power (frame_power).
frame_power = Σline_power (1 to 1280 lines) ・ ・ ・ Formula (4)
In step S06, the power limit unit 10 obtains the gain (Gain_next) of the next frame from the power limit Min value (Limit_min) set in the control constant table 20 and the frame_power by the equation (5). The obtained gain (Gain_next) of the next frame is output to the luminance control unit 11.

Gain_next = (Limit_min) / (frame_power) (5)
However, Gain_next = 1 when Limit_min ≧ frame_power.

[Real-time power calculation]
The power limit unit 10 calculates real-time power, which is current power consumption, in steps S10 to S12 every time one line of video input data RGB_in is input in parallel with the calculation processing of the next frame gain.

In step S10, the power limit unit 10 obtains a power value (line_power_gain) obtained by multiplying the line power (line_power) by the Gain value fed back from the luminance control unit 11.
line_power_gain = line_power * Gain ・ ・ ・ Formula (6)
Gain fed back from the luminance control unit 11 is a value applied to the video input data RGB_in to be displayed on the current display unit.

  In step S <b> 11, the power limit unit 10 calculates the power (real-time power) of the currently displayed screen.

  FIG. 6 is a diagram illustrating processing for obtaining real-time power of the display device according to the first embodiment.

Since the processing of steps S01 and S02 has already been described, the description thereof will be omitted. Further, the power value (line_power_gain) obtained in step S10 is assumed to be the power value of the mth frame and the nth line.
line_power_gain (m, n) = line_power * Gain (7)
FIG. 7 is a diagram illustrating a data structure of the power memory 21 of the display device according to the first embodiment.

  The power memory 21 is provided with an area of 1280 words corresponding to the number of lines (1-1280) of the display unit, and each word stores the power (line_power_gain) for each currently displayed line. . In the example illustrated in FIG. 7, the power of the 1st to (n−1) th line of the mth frame is stored in the 1st to (n−1) words, and the nth of the (m−1) th frame is stored in the n to 1280 words. ˜1280 lines of power are stored. The power memory 21 stores “current frame power” described below.

In the state shown in FIG. 7, the total value of 1 to 1280 words is called the current frame power (frame_power_now (m, n-1)) at the time of storing the mth frame and the (n-1) th line.
frame_power_now (m, n-1) = Σline_power_gain (8)
In step S11 of FIG. 6, the power limit unit 10 searches the power memory 21 and calculates the current frame power (frame_power_now (m, n)) when the mth frame and the nth line are stored based on the equation (9). To calculate. As a result, the current frame power (real-time display power) can be obtained.

frame_power_now (m, n) = frame_power_now (m, n-1)
-line_power_gain (m-1, n)
+ line_power_gain (m, n) (9)
The line power line_power_gain (m−1, n) one frame before (m−1) used in Expression (9) is stored in the power memory 21 having 1280 words. Also, the line power line_power_gain (m, n) of the current frame (m) is replaced with line_power_gain (m−1, n) stored in the power memory 21 after the above equation is calculated. Similarly, the current frame power (real-time display power) is also replaced with the latest value.

  In step S <b> 12 of FIG. 5, the power limit unit 10 compares the obtained real-time power with the power limit Min value and the power limit Max value. When the real-time display power exceeds the power limit Max value, LimitMaxFlg = “H” is output to the luminance control unit 11. Further, Gain_now (gain of current frame) shown in Expression (10) is output to the luminance control unit 11 depending on whether or not the real-time power exceeds the power limit Min value.

Gain_now = (Limit_min) / (frame_power_now (m, n)) Equation (10)
However, Gain_now = 1 is set when Limit_min ≧ frame_power_now. FIG. 8 is a flowchart showing a processing procedure of the luminance control unit 11 of the display device according to the first embodiment. The luminance control unit 11 can also be configured as a processing block that realizes a processing procedure described below.

  In step S20, the luminance control unit 11 checks whether Gain_now (the gain of the current frame) is smaller than 1.

  When Gain_now is 1 (NO in S20), since the real-time power is smaller than the power limit Min value, in step S21, Gain_next (gain of the next frame) is set to gain.

  When Gain_now is smaller than 1 (YES in S20), since the real-time power is equal to or greater than the power limit Min value, Gain_now (gain of the current frame) is set to gain (Gain) in step S21.

  In step S24, the luminance control unit 11 checks whether LimitMaxFlg is “H”.

  When LimitMaxFlg is “H” (YES in S4), since the real-time display power exceeds the power limit Max value, in order to stop the light emission of the EL elements after the scanned line in step S25, the gain ( “L (black mask level)” is set in Gain). In step S26, the set gain (Gain) is output to the power limit unit 10 and reflected in the power limit process.

  If LimitMaxFlg is not “H” (NO in S4), the gain (Gain) set in the previous step is not changed, and the set gain (Gain) is output to the power limit unit 10 in Step S26. And reflected in the power limit process.

  In step S27, the luminance control unit 11 multiplies the video input data RGB_in input from the set side by a gain (Gain).

  According to the operations of the power limit unit 10 and the brightness control unit 11 described above, the video displayed in the current frame using the Gain (value of 1 or less) selected based on the power required for displaying the previous frame. Therefore, it is possible to suppress exceeding the power limit Min value in the current frame. Furthermore, the display power is monitored in real time, and when the real time power is equal to or greater than the limit Min value, the brightness of the displayed data is controlled so as to suppress the increase in power. Further, when the real-time power exceeds the power limit Max value, the light emission of the EL elements after the already scanned line is stopped.

  By such an operation, the display operation can be controlled with the power consumption matching the power supply capability on the set side.

  FIG. 9 is a diagram illustrating the operation timing of the power limit function in the display device according to the first embodiment.

  The power limit function consists of two routes. In the first route, the video input data for one line input from the set side is integrated, converted into electric power for each line, and compared with a limit value to calculate a gain for multiplying the data for the next line. In the second route implemented in parallel with this, the gain is calculated from the power obtained by integrating the video input data of the previous frame. The obtained gain is multiplied by the video input data of the next frame and used as video display data of the next frame.

[Second Embodiment]
In the second embodiment, only the power limit control based on the real-time power described in FIG. 6 of the first embodiment is executed, and the next frame power limit control based on the previous frame power is not executed. This is different from the embodiment. Parts having the same or similar functions as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof is omitted.

  In the second embodiment, steps S05 and S06 in FIG. 5 are not executed, and Gain_next (gain of the next frame) = 1 is fixed. Thereby, only power limit control based on real-time power can be executed.

  The several embodiments described above have been presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  Each function described in the above embodiment may be configured using hardware, or may be realized by reading a program describing each function into a computer using software. Each function may be configured by appropriately selecting either software or hardware.

  Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

  DP ... Display panel, CNTL ... Controller, SG ... Gate line, SL ... Signal line, SST ... Pixel switch, DRT ... Drive transistor, Cs ... Auxiliary capacitor, Pvdd ... High potential power supply, Pvss ... Low potential power supply, RGB_in ... Video input Data, RGB_out: video output data, 10: power limit unit, 11: luminance control unit, 20: control constant table, 21: power memory.

Claims (9)

A display panel in which self-emitting elements are arranged in a matrix on a substrate;
A control unit for controlling light emission of the self-light-emitting element based on input video data,
The controller is
The current power consumption of the display panel is grasped, and when the current power consumption is greater than or equal to the first limit value, video data having a gradation lower than the gradation of the input video data is displayed. Display device to control. The controller is
2. The display according to claim 1, wherein when the current power consumption is equal to or greater than a second limit value greater than the first limit value, control is performed so that subsequent video data is displayed in black in the current frame. apparatus. The power consumption of the display panel is the sum of the power values obtained by multiplying the gradation value of the displayed video data by the power conversion coefficient of the self-luminous element,
The display device according to claim 2, wherein the power conversion coefficient is provided for each self-luminous element for each color. When the current power consumption is greater than or equal to the first limit value, the control unit displays the video data of gradation obtained by multiplying the gradation of the input video data by a gain coefficient smaller than 1. Control
The display device according to claim 3, wherein the gain coefficient is obtained by (first limit value) / (current power consumption).   The display device according to claim 4, wherein the first limit value and the second limit value are rewritable. A display panel in which self-emitting elements are arranged in a matrix on a substrate;
A control unit for controlling light emission of the self-light-emitting element based on input video data,
The controller is
Grasp the current power consumption of the display panel,
When the current power consumption is greater than or equal to the first limit value, control is performed to display the video data of the gradation obtained by multiplying the gradation of the input video data by the first gain coefficient smaller than 1. ,
When the current power consumption is smaller than the first limit value, control is performed to display the video data of the gradation obtained by multiplying the gradation of the input video data by the second gain coefficient,
The first gain coefficient is (first limit value) / (current power consumption),
The second gain factor is
When (first limit value) <(power consumption of the previous frame), (first limit value) / (power consumption of the previous frame),
When (first limit value) ≧ (power consumption of the previous frame), it is 1.
Display device. The controller is
The display according to claim 6, wherein when the current power consumption is equal to or greater than a second limit value that is greater than the first limit value, the subsequent video data is controlled to be displayed in black in the current frame. apparatus. The power consumption of the display panel is the sum of the power values obtained by multiplying the gradation value of the displayed video data by the power conversion coefficient of the self-luminous element,
The display device according to claim 7, wherein the power conversion coefficient is provided for each of the light-emitting elements for each color.   The display device according to claim 8, wherein the first limit value and the second limit value are rewritable.

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