CN107424571B - Organic light emitting diode display device and driving method thereof - Google Patents
Organic light emitting diode display device and driving method thereof Download PDFInfo
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- CN107424571B CN107424571B CN201710775424.9A CN201710775424A CN107424571B CN 107424571 B CN107424571 B CN 107424571B CN 201710775424 A CN201710775424 A CN 201710775424A CN 107424571 B CN107424571 B CN 107424571B
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
- G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
- G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
- G09G3/3266—Details of drivers for scan electrodes
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
- G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
- G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
- G09G3/3275—Details of drivers for data electrodes
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0233—Improving the luminance or brightness uniformity across the screen
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
- G09G2330/02—Details of power systems and of start or stop of display operation
- G09G2330/021—Power management, e.g. power saving
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- Control Of El Displays (AREA)
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Abstract
An organic light emitting diode display device and a driving method thereof are disclosed. The organic light emitting diode display device includes: a line scanning circuit for generating a plurality of line scanning signals; a column driving circuit for generating a plurality of driving signals corresponding to the plurality of row scanning signals according to driving data; a plurality of pixel units arranged in a pixel array, the plurality of pixel units respectively including at least one organic light emitting diode; and a brightness adjusting circuit for preprocessing the display data to generate the driving data, wherein the preprocessing of the brightness adjusting circuit comprises generating the driving data which is used for representing the pixel gray scale and the preset picture brightness according to the display data. The organic light emitting diode display device adjusts the brightness of a picture by adopting a display data preprocessing mode, so that the power consumption can be reduced, and a control circuit can be simplified to reduce the system cost.
Description
Technical Field
The present invention relates to the field of display technologies, and in particular, to an organic light emitting diode display device and a driving method thereof.
Background
The Organic Light Emitting Diode display device employs an Organic Light Emitting Diode (OLED) as a pixel element. An OLED includes a semiconductor anode, a metal cathode, and a hole transport layer, a light emitting layer, and a charge transport layer sandwiched therebetween. When a voltage is applied, electrons and holes recombine in the light-emitting layer to emit light. Each pixel unit of the LED display device includes, for example, pixel elements of three primary colors of red, green, and blue, and each pixel element generates light emission of a corresponding color due to a difference in composition of a light emitting layer, thereby realizing color display. The pixel elements of the organic light emitting diode display device emit light autonomously, do not need a backlight source, and have the advantages of fast response time, high light emitting efficiency, high brightness, wide viewing angle and the like, so the organic light emitting diode display device is a new application technology of a new generation of flat panel displays.
The organic light emitting diode display device mainly comprises a display panel, a row scanning circuit and a column driving circuit. The display panel includes an array formed by arranging a plurality of pixel units in rows and columns. Each pixel unit comprises at least one pixel element and at least one thin film transistor connected with the pixel element. In each frame period, the row scanning circuit time-divisionally and selectively turns on the thin film transistors connected to the pixel elements of each row, and the column driving circuit applies a driving current corresponding to display data of the pixel elements of the row to the anodes of the pixel elements.
In the liquid crystal display device, the brightness of the whole picture can be changed by utilizing the height adjustment of the backlight module, so that the liquid crystal display device can reduce the picture brightness surface and reduce the power consumption. In the organic light emitting diode display device, a backlight module is omitted, which is advantageous in that the thickness dimension can be reduced, but is disadvantageous in that it is difficult to adjust the screen brightness.
Therefore, it is desirable to adjust the picture brightness in the organic light emitting diode display device to meet the demand for improving the display quality or reducing the power consumption.
Disclosure of Invention
In view of the above problems, it is an object of the present invention to provide a driving method for an organic light emitting diode display device, in which blank frames of corresponding data are inserted between image frames according to luminance levels to adjust picture luminance.
According to an aspect of the present invention, there is provided an organic light emitting diode display device including: a line scanning circuit for generating a plurality of line scanning signals; a column driving circuit for generating a plurality of driving signals corresponding to the plurality of row scanning signals according to driving data; a plurality of pixel units arranged in a pixel array, the plurality of pixel units respectively including at least one organic light emitting diode; and a brightness adjustment circuit for preprocessing display data to generate the drive data, wherein the plurality of pixel cells are connected to the row scanning circuit and the column driving circuit, the plurality of row scanning signals are used for scanning pixel cells of different rows, the plurality of drive signals are used for generating drive currents to be applied to the pixel cells of different columns so as to control effective brightness of the plurality of pixel cells in a frame period, and the preprocessing of the brightness adjustment circuit comprises generating the drive data which is used for representing pixel gray scale and preset picture brightness in a combined manner according to the display data.
Preferably, the preprocessing of the brightness adjustment circuit includes inserting at least one blank frame corresponding to the picture brightness in a plurality of image frames in which the effective brightness of each pixel unit in a frame period corresponds to the gray scale of the corresponding pixel, and in the at least one blank frame in which the effective brightness of all the pixel units in a frame period corresponds to a constant gray scale.
Preferably, a ratio between the number of the plurality of image frames and the number of the at least one blank frame is set according to the screen brightness.
Preferably, a constant gray level of the at least one blank frame is set according to the screen brightness.
Preferably, the plurality of image frames and the at least one blank frame have a frame period length equal to each other.
Preferably, the at least one blank frame is periodically distributed among the plurality of image frames.
Preferably, consecutive blank frames of the at least one blank frame are located between two adjacent image frames of the plurality of image frames.
Preferably, the brightness adjustment circuit dynamically adjusts the frame rate of the driving data according to the number of the at least one blank frame such that the driving data and the display data include the same number of image frames per unit time.
Preferably, the plurality of pixel units respectively include a plurality of pixel elements for displaying different colors.
Preferably, the brightness adjusting circuit adjusts brightness of pictures of different colors respectively.
Preferably, the plurality of pixel units respectively include: a driving transistor and an organic light emitting diode sequentially connected in series between a supply voltage and ground; and the selection switch tube is connected between the driving end and the grid electrode of the driving transistor, the driving end receives a driving signal, and the grid electrode of the selection switch tube is connected to the selection end to receive a scanning signal.
Preferably, the plurality of pixel units further include: a storage capacitor connected between the gate of the drive transistor and ground.
Preferably, the preprocessing of the brightness adjustment circuit includes setting pixel units of a plurality of local areas in an image frame as blank pixels, in normal pixels of the image frame, effective brightness of each pixel unit in a frame period corresponds to a gray level of the corresponding pixel, and in blank pixels of the image frame, effective brightness of all pixel units in a frame period corresponds to a constant gray level.
Preferably, a ratio between the number of the normal pixels and the number of the blank pixels in the image frame is set according to the screen brightness.
Preferably, a constant gray level of the blank pixel is set according to the screen brightness.
Preferably, the plurality of local regions are a plurality of sub-regions uniformly distributed in an image frame corresponding to the image frame.
Preferably, the plurality of pixel units respectively include a plurality of pixel elements for displaying different colors.
Preferably, the plurality of local regions are pixel elements of a predetermined color in the plurality of pixel units.
Preferably, in the same frame, the pixel elements of the selected color are set to a constant effective brightness, and in successive frames, the pixel elements of the selected different colors are set to a constant effective brightness, thereby maintaining the color effect of successive pictures.
According to another aspect of the present invention, there is provided a driving method for an organic light emitting diode display device including a plurality of pixel units arranged in a pixel array, the method including: preprocessing the display data to generate driving data; generating a plurality of driving signals corresponding to the plurality of line scanning signals according to the driving data; employing the plurality of line scanning signals for scanning pixel units of different lines; and employing the plurality of drive signals for generating drive currents to be applied to the pixel cells of different columns to control effective brightness of the plurality of pixel cells in a frame period, wherein the preprocessing comprises generating drive data for characterizing both pixel gray scale and predetermined picture brightness based on the display data.
Preferably, the preprocessing includes inserting at least one blank frame corresponding to the screen brightness in a plurality of image frames in which the effective brightness of each pixel unit in a frame period corresponds to the gray scale of the corresponding pixel, and in the at least one blank frame in which the effective brightness of all pixel units in a frame period corresponds to a constant gray scale.
Preferably, a ratio between the number of the plurality of image frames and the number of the at least one blank frame is set according to the screen brightness.
Preferably, a constant gray level of the at least one blank frame is set according to the screen brightness.
Preferably, the plurality of image frames and the at least one blank frame have a frame period length equal to each other.
Preferably, the at least one blank frame is periodically distributed among the plurality of image frames.
Preferably, consecutive blank frames of the at least one blank frame are located between two adjacent image frames of the plurality of image frames.
Preferably, the method further comprises the following steps: dynamically adjusting a frame rate of the driving data according to the number of the at least one blank frame such that the driving data and the display data include the same number of image frames per unit time.
Preferably, the plurality of pixel units respectively include a plurality of pixel elements for displaying different colors.
Preferably, the brightness of the picture of the different colors is adjusted separately.
Preferably, the preprocessing includes setting pixel units of a plurality of local regions in an image frame as blank pixels, in normal pixels of the image frame, effective luminances of the respective pixel units in a frame period correspond to gray scales of the respective pixels, and in blank pixels of the image frame, effective luminances of all the pixel units in the frame period correspond to constant gray scales.
Preferably, a ratio between the number of the normal pixels and the number of the blank pixels in the image frame is set according to the screen brightness.
Preferably, a constant gray level of the blank pixel is set according to the screen brightness.
Preferably, the plurality of local regions are a plurality of sub-regions uniformly distributed in an image frame corresponding to the image frame.
Preferably, the plurality of pixel units respectively include a plurality of pixel elements for displaying different colors.
Preferably, the plurality of local regions are pixel elements of a predetermined color in the plurality of pixel units.
Preferably, the pixel elements of the selected color are set to a constant effective luminance in the same frame, and the pixel elements of the selected different color are set to a constant effective luminance in successive frames.
According to the organic light emitting diode display device of the embodiment of the invention, the display data is converted into the driving data in a display data preprocessing mode, wherein blank frames are inserted between image frames so as to adjust the brightness of the image by using the blank frames. The adjusting method can adjust the effective brightness of all the pixel units according to the same proportion, so that the image brightness is improved during high-quality image display and reduced during low-quality image display according to the display requirement, and the power consumption is reduced. The adjusting method does not need to include an additional switch tube in the pixel unit for adjusting the effective lighting time of the organic light emitting diode OLED to adjust the image brightness, and the control circuit does not need to generate a duty ratio signal corresponding to the image brightness. The organic light emitting diode display device according to the embodiment of the present invention may further reduce power consumption and may simplify a control circuit to reduce system cost, compared to an existing organic light emitting diode display device.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings.
Fig. 1 illustrates a schematic block diagram of a structure of an organic light emitting diode display device according to the related art.
Fig. 2 illustrates a schematic circuit diagram of a pixel unit in the organic light emitting diode display device of fig. 1.
Fig. 3 illustrates a schematic block diagram of a structure of an organic light emitting diode display device according to an embodiment of the present invention.
Fig. 4 illustrates a schematic circuit diagram of a pixel unit in the organic light emitting diode display device in fig. 3.
Fig. 5a and 5b illustrate dynamic frame rates of driving data at different screen luminances of the organic light emitting diode display device according to an embodiment of the present invention, respectively.
Detailed Description
The invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by like reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale. In addition, lead-out lines other than the corresponding driving electrodes and sensing electrodes are not drawn in the drawings, and some well-known portions may not be shown.
In the following description, numerous specific details of the invention, such as structure, materials, dimensions, processing techniques and techniques of the devices are described in order to provide a more thorough understanding of the invention. However, as will be understood by those skilled in the art, the present invention may be practiced without these specific details.
Herein, the pixel element of the organic light emitting diode display device is an organic light emitting diode OLED. For the sake of simplicity, only an example of a monochrome display device comprising one pixel element per pixel cell is shown herein. It will be appreciated that the invention is not so limited and may be applied to a colour display device comprising a plurality of pixel elements per pixel unit.
Fig. 1 illustrates a schematic block diagram of a structure of an organic light emitting diode display device according to the related art.
The structure of the oled display device 100 mainly includes a row scanning circuit 110, a column driving circuit 120, a brightness adjusting circuit 140, and a display panel. The display panel includes an n × m array formed by arranging a plurality of pixel units 130 in rows and columns.
The output end of the row scan circuit 110 is connected to the scan lines S1 through Sn, and the scan lines S1 through Sn are further connected to the control ends of the pixel units 130 in a corresponding row.
The output terminal of the column driving circuit 120 is connected to the driving lines D1 to Dm, and the driving lines D1 to Dm are further connected to the driving terminals of the pixel units 130 in a corresponding column respectively.
The output end of the brightness adjusting circuit 140 is connected to the enable lines E1 to Em, and the enable lines E1 to Em are further connected to the adjusting ends of the pixel units 130 in the corresponding row.
In operation, the organic light emitting diode display device displays images frame by frame, thereby forming a continuous video picture in a plurality of frame periods. In each frame period, the row scanning circuit 110 scans to selectively turn on the selection switch tubes in one row of the pixel units 130 in a time-sharing manner.
Further, during the period that the selection switch tube of the pixel unit 130 in the selected row is turned on, the column driving circuit 120 applies a driving current corresponding to the display data to the anodes of the pixel elements in the pixel unit 130 in the selected row. In each frame period, the effective brightness of the pixel element corresponds to the drive current, and thus corresponds to the gray scale of the corresponding pixel in the image.
Further, during the period that the selection switch tube of the pixel unit 130 in the selected row is turned on, the brightness adjusting circuit 120 provides the enable signal to the additional switch tube in the pixel unit in the row of the corresponding row. The enable signal is a pulse signal having a duty ratio corresponding to the picture brightness. The additional switching tube controls the active lighting time of the driving current applied to the anodes of the pixel elements in the row of pixel cells 130 according to the enable signal.
The effective brightness of the pixel element in one frame period depends on the magnitude of the drive current and the duty cycle of the enable signal. The driving currents of the pixel elements correspond to the gray scales of the corresponding image pixels respectively, and the effective lighting time corresponds to the brightness of the whole picture. Therefore, each row of pixel units of the organic light emitting diode display device can adjust the effective brightness according to the same proportion, and the adjustment of the picture brightness is realized.
Fig. 2 illustrates a schematic circuit diagram of a pixel unit in the organic light emitting diode display device of fig. 1.
The pixel unit 130 includes a selection switch tube MS1, an additional switch tube MS2, a driving transistor MD, a capacitor CD, and an organic light emitting diode OLED. In this embodiment, the selection switch MS1, the additional switch MS2, and the driving transistor MD are, for example, P-type MOS transistors, respectively. In alternative embodiments, N-type MOS transistors may be used instead of P-type MOS transistors.
In the pixel unit 130, the driving transistor MD, the additional switching tube MS, and the organic light emitting diode OLED are sequentially connected in series between a supply voltage and ground (i.e., analog ground). The connection of the selection switch tube MS1 is between the driving end and the gate of the driving transistor MD. The gate of the selection switch tube MS1 and the gate of the additional switch tube MS2 are connected to the selection terminal and the enable terminal, respectively, to receive the selection signal Si and the enable signal Ei, respectively. The selection switch tube MS1 receives the driving signal Di via the driving end. The capacitor C1 is connected between the gate of the drive transistor MD and ground and serves as a storage capacitor.
In the frame period, the led display device 100 time-divisionally turns on the selection switch MS1 in each row of pixel units 130 under the control of the scan signal. During the on period of the selection switch tube MS1, the driving signal Di is applied to the gate of the driving transistor MD via the selection switch tube MS1, so that the driving transistor MD generates the driving current Id corresponding to the display data. The driving current Id is applied to the organic light emitting diode OLED via the additional switching tube MS 2.
The effective luminance of the organic light emitting diode OLED in one frame period depends on the magnitude of the driving current Id and the duty ratio of the enable signal Ei. The duty ratio of the enable signal Ei determines an effective lighting time of the organic light emitting diode OLED. The driving current Id of the pixel unit 130 corresponds to the gray scale of the corresponding image pixel, and the duty ratio of the enable signal Ei corresponds to the brightness of the whole image. Therefore, each row of pixel units of the organic light emitting diode display device can adjust the effective brightness according to the same proportion, and the adjustment of the picture brightness is realized.
In the above-mentioned organic light emitting diode display device according to the related art, the picture brightness is adjusted using an additional switching tube connected in series with the organic light emitting diode. The adjusting method can adjust the effective brightness of all the pixel units according to the same proportion in a plurality of continuous frame periods, thereby improving the picture brightness during high-quality image display and reducing the picture brightness during low-quality image display according to the display requirement so as to reduce the power consumption. However, since the additional switching tube is connected in series with the light emitting diode, the additional switching tube itself generates additional power consumption.
Further, the operation of the additional switching tube requires the brightness adjusting circuit to provide an enable signal with a duty ratio corresponding to the brightness of the picture, resulting in a complicated control circuit. To generate the enable signal, the operating frequency of the brightness adjusting circuit will be higher than that of the row driving circuit, resulting in an increase in system cost.
Fig. 3 illustrates a schematic block diagram of a structure of an organic light emitting diode display device according to an embodiment of the present invention.
The structure of the oled display device 200 mainly includes a row scanning circuit 110, a column driving circuit 120, a brightness adjusting circuit 240, and a display panel. The display panel includes an n × m array formed by arranging a plurality of pixel units 130 in rows and columns, where n and m are natural numbers, respectively.
The output end of the row scan circuit 110 is connected to the scan lines S1 through Sn, and the scan lines S1 through Sn are further connected to the control ends of the pixel units 130 in a corresponding row.
The brightness adjusting circuit 240 is connected to the column driving circuit 120, and is used for preprocessing the display data to generate the driving data for representing the gray scale of the pixel and the brightness of the image. In this embodiment, the driving data is formed by inserting at least one blank frame corresponding to the brightness of a picture among a plurality of image frames for representing the gray levels of pixels.
The column driving circuit 120 generates a driving signal according to the driving data. The output terminal of the column driving circuit 120 is connected to the driving lines D1 to Dm, and the driving lines D1 to Dm are further connected to the driving terminals of the pixel units 130 in a corresponding column respectively.
In operation, the organic light emitting diode display device displays images frame by frame, thereby forming a continuous video picture in a plurality of frame periods. In each frame period, the row scanning circuit 110 scans to selectively turn on the selection switch tubes in one row of the pixel units 230 in a time-sharing manner.
Further, during the period that the selection switch tube of the pixel unit 230 in the selected row is turned on, the column driving circuit 120 applies a driving current corresponding to the driving data to the anodes of the pixel elements in the pixel unit 230 in the selected row. In each frame period of an image frame, the effective brightness of the pixel element corresponds to the drive current, and thus corresponds to the gray level of the corresponding pixel in the image. The effective brightness of the pixel element is then constant during the frame period of each blank frame. In one embodiment, the blank frame is a black picture, and thus, inserting a blank frame between image frames will reduce the picture brightness. In another embodiment, the blank frame is a white picture, and thus, inserting a blank frame between image frames will increase picture brightness.
In this embodiment, the brightness level of the picture brightness can be adjusted by changing the ratio between the number of blank frames relative to the number of image frames. The blank frame is not limited to a black frame or a white frame, but may be any single gray scale frame, that is, the gray scales of all pixel units in the blank frame are constant values. When a plurality of blank frames are used, the plurality of blank frames may be successively inserted between two adjacent image frames or may be respectively inserted between two adjacent image frames.
Therefore, each row of pixel units of the organic light emitting diode display device can adjust the effective brightness according to the same proportion, and the adjustment of the picture brightness is realized.
Further, since the display data transmitted from the control terminal to the oled display device has a predetermined frame rate, the brightness adjusting circuit further dynamically adjusts the frame rate of the driving data according to the image brightness, so that all image frames can be displayed, thereby achieving the image brightness adjustment while maintaining the display quality of the dynamic image.
Fig. 4 illustrates a schematic circuit diagram of a pixel unit in the organic light emitting diode display device in fig. 3.
The pixel unit 230 includes a selection switch tube MS1, a driving transistor MD, a capacitor CD, and an organic light emitting diode OLED. In this embodiment, the selection switch MS1 and the driving transistor MD are, for example, P-type MOS transistors, respectively. In alternative embodiments, N-type MOS transistors may be used instead of P-type MOS transistors.
In the pixel unit 230, the driving transistor MD and the organic light emitting diode OLED are sequentially connected in series between a power supply voltage and ground. The connection of the selection switch tube MS1 is between the driving end and the gate of the driving transistor MD. The gate of the selection switch MS1 is connected to the selection terminal to receive the selection signal Si. The selection switch tube MS1 receives the driving signal Di via the driving end.
In the frame period, the led display device 100 time-divisionally turns on the selection switch MS1 in each row of pixel units 230 under the control of the scan signal. During the on period of the selection switch tube MS1, the driving signal Di is applied to the gate of the driving transistor MD via the selection switch tube MS1, so that the driving transistor MD generates the driving current Id corresponding to the display data. The driving current Id is applied to the organic light emitting diode OLED via the additional switching tube MS 2.
The effective brightness of the organic light emitting diode OLED in one frame period depends on the magnitude of the driving current Id. The number of blank frames inserted in a plurality of consecutive image frames is used to adjust the brightness of the picture, and the ratio between the number of image frames and the number of blank frames determines the brightness level. Therefore, each row of pixel units of the organic light emitting diode display device can adjust the effective brightness according to the same proportion, and the adjustment of the picture brightness is realized.
In the organic light emitting diode display device according to the embodiment of the present invention, the display data is converted into the driving data in a display data preprocessing manner, wherein blank frames are inserted between the image frames to adjust the brightness of the picture using the blank frames. The adjusting method can adjust the effective brightness of all the pixel units according to the same proportion, so that the image brightness is improved during high-quality image display and reduced during low-quality image display according to the display requirement, and the power consumption is reduced. The adjusting method does not need to include an additional switch tube in the pixel unit for adjusting the effective lighting time of the organic light emitting diode OLED to adjust the image brightness, and the control circuit does not need to generate a duty ratio signal corresponding to the image brightness. The organic light emitting diode display device according to the embodiment of the present invention may further reduce power consumption and may simplify a control circuit to reduce system cost, compared to an existing organic light emitting diode display device.
Fig. 5a and 5b illustrate dynamic frame rates of driving data at different screen luminances of the organic light emitting diode display device according to an embodiment of the present invention, respectively.
In the organic light emitting diode display device according to the embodiment of the present invention, the brightness adjusting circuit 230 shown in fig. 3 preprocesses display data and inserts blank frames between image frames to adjust the brightness of a picture using the blank frames. In the case where the frame rate of the data signal is 4Hz, the organic light emitting diode display device may display 4 image frames fm1 to fm4 in a time period of each second.
In this embodiment, in an image frame, the effective brightness of each pixel unit in one frame period corresponds to the gray scale of the corresponding pixel, for example, the driving signal of each pixel unit takes a value between 0 and 255 levels of voltage. In the blank frame, the effective brightness of all the pixel units in one frame period corresponds to a constant gray level, for example, the driving signals of all the pixel units are 0-level voltages, so that the blank frame inserted between the image frames is a black picture. As shown in fig. 5a, in the case where one blank frame fb1 is inserted into 4 image frames, the frame rate of the driving data generated from the display data is 5Hz, and the screen luminance is 80% of the full luminance. As shown in fig. 5b, in the case where two blank frames fb1, fb2 are inserted into 4 image frames, the frame rate of the driving data generated from the display data is 6Hz, and the screen luminance is 67.7% of the full luminance.
Although two blank frames fb1, fb2 are shown in fig. 5b separated by one image frame. However, the present invention is not limited thereto, and two blank frames may be consecutively inserted between two adjacent image frames or spaced apart from each other by one or more image frames.
In this embodiment, the frame rate of the drive data generated from the display data is dynamically varied between 4-6 Hz. However, the present invention is not limited thereto, and the frame rate of the driving data is dynamically changed between 30 to 240Hz, for example, in an actual product. The upper limit of the dynamic range is limited by the refresh rate of the display device. If the standard frame rate of the display data is 60Hz and the maximum frame rate of the driving data is 240Hz, a maximum of 180 blank frames can be inserted into 60 image frames in a time period of one second, thereby realizing 180-level picture brightness adjustment. Further, by setting a constant gray scale of the blank frame, more levels of picture brightness adjustment can be realized. In the present specification, the concept of "row" and "column" is not limited to the lateral concept shown in the drawings and the longitudinal concept shown in the drawings, and embodiments conforming to the basic principle of the present invention are within the scope of the present invention according to actual needs.
In the above-described embodiments, it is described that the luminance adjustment circuit generates the drive data from the display data, in which the frame rate of the drive data is dynamically adjusted so that blank frames are inserted between the image frames. In an alternative embodiment, the luminance adjusting circuit maintains the frame rate substantially constant when generating the driving data from the display data, and further sets the pixels of the plurality of partial areas as blank pixels according to the screen luminance in each image frame. The plurality of local regions include a plurality of sub-regions uniformly distributed in the image screen, or pixel elements of a predetermined color in a pixel unit. The effective brightness of the blank pixel in the frame period corresponds to a constant gray level, such as a minimum gray level (normally off) or a maximum gray level (normally on).
This alternative embodiment sets the number of the plurality of blank pixels according to the picture brightness, so that the required picture brightness can be set while maintaining the frame rate unchanged. In the case where the plurality of local areas are pixel elements of predetermined colors, for example, in the same frame, pixel elements of a selected color are set to a constant effective luminance, and in successive frames, pixel cells of different colors are selected, thereby maintaining the color effect of successive frames. For example, in three consecutive image frames, the pixel elements of the red, green and blue colors are set to a constant effective brightness, respectively, and the pixel elements of the remaining colors are lit up according to the display data.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and their full scope and equivalents.
Claims (12)
1. An organic light emitting diode display device comprising:
a line scanning circuit for generating a plurality of line scanning signals;
a column driving circuit for generating a plurality of driving signals corresponding to the plurality of row scanning signals according to driving data;
a plurality of pixel units arranged in a pixel array, the plurality of pixel units respectively including at least one organic light emitting diode; and
a brightness adjustment circuit for preprocessing display data to generate the driving data,
wherein the plurality of pixel units are connected to the row scanning circuit and the column driving circuit, the plurality of row scanning signals are used for scanning pixel units in different rows, the plurality of driving signals are used for generating driving current to be applied to pixel units in different columns so as to control effective brightness of the plurality of pixel units in a frame period,
the preprocessing of the brightness adjustment circuit includes generating, based on the display data, drive data for characterizing both a pixel gray scale and a predetermined picture brightness, wherein pixel cells of a plurality of local areas in an image frame are set as blank pixels, in normal pixels of the image frame, effective brightness of each pixel cell in a frame period corresponds to a gray scale of the corresponding pixel, in blank pixels of the image frame, effective brightness of all pixel cells in a frame period corresponds to a constant gray scale,
in the same frame, the pixel element of the selected color is set to be the constant effective brightness, and in the continuous frames, the pixel unit of the selected different color is set to be the constant effective brightness, thereby maintaining the color effect of the continuous frames.
2. The organic light emitting diode display device according to claim 1, wherein a ratio between the number of normal pixels and the number of blank pixels in the image frame is set according to the screen luminance.
3. The organic light emitting diode display device of claim 1, wherein a constant gray scale of the blank pixel is set according to the screen brightness.
4. The organic light emitting diode display device of claim 1, wherein the plurality of local regions are a plurality of sub-regions uniformly distributed in an image picture corresponding to the image frame.
5. The organic light emitting diode display device of claim 1, wherein the plurality of pixel units respectively comprise a plurality of pixel elements for displaying different colors.
6. The organic light emitting diode display device of claim 5, wherein the plurality of local regions are pixel elements of a predetermined color in the plurality of pixel units.
7. A driving method for an organic light emitting diode display device including a plurality of pixel units arranged in a pixel array, the method comprising:
preprocessing the display data to generate driving data;
generating a plurality of driving signals corresponding to the plurality of line scanning signals according to the driving data;
employing the plurality of line scanning signals for scanning pixel units of different lines;
employing the plurality of drive signals for generating drive currents to be applied to the pixel cells of different columns to control effective brightness of the plurality of pixel cells in a frame period,
wherein the preprocessing includes generating, based on the display data, drive data for characterizing both a pixel gray scale and a predetermined picture brightness, wherein pixel cells of a plurality of local areas in an image frame are set as blank pixels, in normal pixels of the image frame, effective brightness of each pixel cell in a frame period corresponds to a gray scale of the corresponding pixel, in blank pixels of the image frame, effective brightness of all pixel cells in a frame period corresponds to a constant gray scale,
in the same frame, the pixel element of the selected color is set to be the constant effective brightness, and in the continuous frames, the pixel unit of the selected different color is set to be the constant effective brightness, thereby maintaining the color effect of the continuous frames.
8. The method according to claim 7, wherein a ratio between the number of normal pixels and the number of blank pixels in the image frame is set according to the screen brightness.
9. The method of claim 7, wherein the constant gray level of the blank pixel is set according to the picture brightness.
10. The method of claim 7, wherein the plurality of local regions are a plurality of sub-regions that are evenly distributed in an image picture to which the image frame corresponds.
11. The method of claim 7, wherein the plurality of pixel cells each comprise a plurality of pixel elements for displaying a different color.
12. The method of claim 11, wherein the plurality of local regions are pixel elements of a predetermined color in the plurality of pixel cells.
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| US10699641B2 (en) | 2017-12-27 | 2020-06-30 | Wuhan China Star Optoelectronics Semiconductor Display Technology Co., Ltd. | OLED display panel and OLED display device |
| CN107993609A (en) * | 2018-03-16 | 2018-05-04 | 成都晶砂科技有限公司 | Method, system and the drive circuit that analog- and digital- combination drive display unit is shown |
| CN111276092B (en) * | 2020-01-21 | 2021-04-23 | 卡莱特云科技股份有限公司 | Optimization parameter determination method and device |
| WO2022088017A1 (en) * | 2020-10-30 | 2022-05-05 | 京东方科技集团股份有限公司 | Driving method for display panel, storage medium, drive device, and display device |
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| CN101373585A (en) * | 2007-08-20 | 2009-02-25 | 旭曜科技股份有限公司 | Display drive method and driver using the same |
| CN101661719B (en) * | 2008-08-27 | 2012-06-27 | 晶宏半导体股份有限公司 | Black frame inserting method for liquid crystal display |
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