KR101409539B1 - Organic electroluminescence display device and driving method thereof - Google Patents

Abstract

The present invention provides a display device comprising: a display section including a plurality of subpixels; A scan driver for supplying a scan signal to the display unit; And a data driver for converting an image data signal supplied from the outside into an analog data signal and a digital data signal according to a gray level and supplying an analog data signal and a digital data signal to the display unit.

Organic electroluminescence display, gradation, compensation

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic light emitting display,

The present invention relates to an organic light emitting display and a driving method thereof.

An organic electroluminescent device used in an organic electroluminescent display device is a self-luminous device in which a light emitting layer is formed between two electrodes located on a substrate.

In addition, the organic light emitting display device may include a top emission type, a bottom emission type, or a dual emission type depending on a direction in which light is emitted. It is divided into a passive matrix and an active matrix depending on the driving method.

In such an organic light emitting display, when a scan signal, a data signal, a power supply, and the like are supplied to a plurality of subpixels arranged in a matrix form, the selected subpixel emits light, thereby displaying an image.

On the other hand, in the organic light emitting display device, a compensation method using a voltage or a current has been proposed in order to solve the problem that the driving transistor is very sensitive to the electrical characteristics and the luminance is uneven.

In the case of the voltage compensation method, a programming time of a predetermined time is required to compensate the threshold voltage of the driving transistor, and a large number of transistors and complicated control signals must be used. In the case of the current compensation method, although the current mobility and the threshold voltage are compensated, the parasitic capacitance component of the data line is very large.

Therefore, in the conventional organic light emitting display, a compensation method capable of solving the luminance unevenness problem and improving the display quality should be provided.

SUMMARY OF THE INVENTION An object of the present invention is to provide an improved compensation method capable of solving the luminance non-uniformity problem and improving display quality in an organic light emitting display.

According to an aspect of the present invention, there is provided a display device comprising: a display unit including a plurality of subpixels; A scan driver for supplying a scan signal to the display unit; And a data driver for converting an image data signal supplied from the outside into an analog data signal and a digital data signal according to a gray level and mixing and supplying the analog data signal and the digital data signal to the display unit.

The data driver determines the grayscale of the video data signal as a higher bit group and a lower bit group. When the grayscale of the video data signal is a higher bit group, the data driver converts the video data signal into an analog data signal, The image data signal can be converted into a digital data signal.

The data driver may determine the lower 3 bits to 4 bits of the gradation of the video data signal as a lower bit group and judge the remaining bits as a higher bit group.

The data driver may include: a determination unit determining whether the gradation of the image data signal is an upper bit group or a lower bit group; An analog driver for converting an image data signal corresponding to an upper bit group received from the determination unit into an analog data signal and outputting the analog data signal; And a digital driver for converting the image data signal corresponding to the lower bit group received from the determination unit into a digital data signal and outputting the digital data signal.

The data driver includes a first switch located between the output terminals of the analog driver section and a second switch located between the output terminals of the digital driver section and the first switch is controlled such that the analog data signal and the digital data signal are selectively supplied to the display section The switching operation can be performed.

The digital driver may output the control signal through the second switch such that the subpixel is selectively supplied with the analog data signal and the digital data signal and is driven in the analog mode and the digital mode.

The sub-pixel includes a first switching transistor having a gate connected to the first scan wiring, one end connected to the data wiring and the other end connected to the first node, a gate connected to the second scan wiring, A third switching transistor having a gate connected to the second node, one end connected to the first node and the other end connected to the third node, and a gate connected to the second scan wiring, A fourth switching transistor having one end connected to the third node and the other end connected to the fourth node, a fifth switching transistor having a gate connected to the first scan wiring and one end connected to the fourth node, A driving transistor having one end connected to the first power supply line and the other end connected to the fourth node, a first electrode connected to the other end of the fifth switching transistor, and a second electrode connected to the second power supply line A first capacitor having one end coupled to the second node and the other end connected to the first power supply line and a second capacitor having one end connected to the first power supply line and the other end connected to the third node, .

The subpixel can operate in an analog mode when a logic high signal is supplied from the control wiring and in a digital mode when a logic low signal is supplied from the control wiring.

In operation in the analog mode, a gray level corresponding to the driving current of the driving transistor is expressed in the subpixel, and in the digital mode, the gray level corresponding to the emission time of the organic light emitting diode can be expressed.

The first to fourth switching transistors may be P-type transistors, and the fifth switching transistor may be an N-type transistor.

The transistors included in the subpixel may be poly transistors.

According to another aspect of the present invention, there is provided an image processing method comprising: a determination step of determining whether a gray level of an image data signal supplied from the outside is an upper bit group or a lower bit group; A converting step of converting the image data signal corresponding to the upper bit group into an analog data signal and the image data signal corresponding to the lower bit group into a digital data signal; And a supplying step of mixing and supplying the analog data signal and the digital data signal to the subpixel.

In the determination step, if the gray level of the video data signal is in the lower 3 bits to 4 bits, it is determined to be a lower bit group, and the remaining bits can be determined as a higher bit group.

And a setting step of supplying a control signal to the subpixel so that the subpixel selectively supplied with the analog data signal and the digital data signal is driven in the analog mode and the digital mode after the conversion step.

In operation in the analog mode, the subpixels are represented by gradations corresponding to the driving currents of the driving transistors included in the subpixels. In operation in the digital mode, the subpixels correspond to the emission times of the organic light emitting diodes included in the subpixels The gradation can be expressed.

The present invention has an effect of providing an improved compensation method capable of solving the luminance unevenness problem and improving display quality in an organic light emitting display. Further, the present invention has an effect that the analog data signal and the digital data signal can be written in a hybrid form. In addition, the present invention has an effect of providing ease in realizing a large-area organic light emitting display device by separately supplying low-gradation gamma and high-gradation gamma.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a schematic plan view of an organic light emitting display according to an embodiment of the present invention.

As shown in FIG. 1, the organic light emitting display device may include a substrate 110. In addition, a display unit DP including a plurality of sub-pixels P may be included on the substrate 110. [ Further, it may include an adhesive member SL located at the outer periphery of the display portion DP. Further, it may include a sealing substrate 190 for sealing the substrate 110 with the adhesive member SL. In addition, it may include a driving unit DR for supplying a driving signal or the like to the display unit DP. In addition, it may include a pad unit PD for transmitting a drive signal or the like supplied from the outside to the driver DR.

Here, the substrate 110 can be selected to have excellent mechanical strength and dimensional stability as a material for forming devices. As a material of the substrate 110, a glass plate, a metal plate, a ceramic plate, or a plastic plate (polycarbonate resin, acrylic resin, vinyl chloride resin, polyethylene terephthalate resin, polyimide resin, polyester resin, Resin, etc.), but are not limited thereto.

Here, the adhesive member SL may be, but not limited to, a front sealant, an edge sealant, a frit, and the like.

The sealing substrate 190 may be formed of a transparent material when the organic light emitting display device is a top emission type, a transparent or opaque material when the bottom emission type is a transparent material, or a transparent material when the organic light emitting display is a double- .

On the other hand, the subpixel P may emit three colors of red, green, and blue to realize various images, but is not limited thereto. The luminescent concept of subpixels will be described in more detail as follows.

2 is an illustration of an image implementation of a subpixel included in an organic light emitting display device.

2, the organic light emitting display includes subpixels having a red light emitting layer 130R, a green light emitting layer 130G, and a blue light emitting layer 130B that emit red light, green light, and blue light, respectively, can do.

One subpixel may include a transistor, a capacitor, and an organic light emitting diode, and the organic light emitting diode included in one subpixel may include one or more light emitting layers.

Here, the organic light emitting diode included in each sub-pixel includes a first electrode 120 and a first electrode 120, which are disposed on the first electrode 120, 130G and 130B and a second electrode 140 located on the light emitting layers 130R, 130G and 130B. The first electrode 120 and the second electrode 140 may be respectively selected as an anode or a cathode depending on the formation method of the organic light emitting diode.

Meanwhile, the light emitting layers 130R, 130G, and 130B of the organic light emitting diode may include at least one of a hole injecting layer, a hole transporting layer, an electron transporting layer, and an electron injecting layer. Their hierarchical structure will be described in more detail as follows.

3 is a hierarchical structure diagram of the organic light emitting diode shown in FIG.

3, the organic light emitting diode includes a hole injection layer 131, a hole transport layer 132, a light emitting layer 133, an electron transport layer 134, and an electron injection layer (not shown) disposed on the first electrode 120 135 and a second electrode 140 located on the electron injection layer 135. [

First, a hole injection layer 131 may be positioned on the first electrode 120. The hole injection layer 131 may function to smoothly inject holes from the first electrode 120 into the light emitting layer 133 and may be formed of cupper phthalocyanine (CuPc), poly (3,4) -ethylenedioxythiophene (PEDOT) But is not limited to, at least one selected from the group consisting of PANI (polyaniline) and NPD (N, N-dinaphthyl-N, N'-diphenyl benzidine).

The hole injection layer 131 described above can be formed by evaporation or spin coating.

The hole transport layer 132 plays a role of facilitating the transport of holes and includes a hole transport material such as NPD (N, N-dinaphthyl-N, N'-diphenyl benzidine), TPD (N, N'- , N'-bis- (phenyl) -benzidine), s-TAD and MTDATA (4,4 ', 4 "-tris (N-3-methylphenyl-N-phenylamino) But is not limited thereto.

The hole transporting layer 132 may be formed by an evaporation method or a spin coating method. The light emitting layer 133 may be formed of a material that emits red, green, blue, and white light, and may be formed using phosphorescent or fluorescent materials.

When the light emitting layer 133 is red, it includes a host material containing CBP (carbazole biphenyl) or mCP (1,3-bis (carbazol-9-yl) a phosphorescent dopant including at least one selected from the group consisting of iridium, iridium, PQIr (acac) (bis (1-phenylquinoline) acetylacetonate iridium), PQIr (tris (1-phenylquinoline) iridium) and PtOEP (octaethylporphyrin platinum) Or PBD: Eu (DBM) 3 (Phen) or Perylene. However, the present invention is not limited thereto.

When the light emitting layer 133 is green, it may be made of a phosphorescent material including a dopant material including a host material including CBP or mCP and containing Ir (ppy) 3 (fac tris (2-phenylpyridine) iridium) Alternatively, it may be made of a fluorescent material including Alq3 (tris (8-hydroxyquinolino) aluminum), but is not limited thereto.

When the light emitting layer 133 is blue, the light emitting layer 133 may include a phosphorescent material including a host material including CBP or mCP and a dopant material including (4,6-F2ppy) 2Irpic.

Alternatively, the fluorescent material may include any one selected from the group consisting of spiro-DPVBi, spiro-6P, distyrylbenzene (DSB), distyrylarylene (DSA), PFO polymer, and PPV polymer. It is not limited.

Here, the electron transport layer 134 plays a role of facilitating the transport of electrons, and may be any one selected from the group consisting of Alq3 (tris (8-hydroxyquinolino) aluminum), PBD, TAZ, spiro-PBD, BAlq and SAlq But is not limited thereto.

The electron transport layer 134 may be formed by evaporation or spin coating, but is not limited thereto. The electron transport layer 134 may prevent holes injected from the first electrode 120 from passing through the light emitting layer 133 and moving to the second electrode 140. In other words, it may serve as a hole blocking layer and may serve to efficiently combine holes and electrons in the light emitting layer 133.

Here, the electron injection layer 135 serves to smooth the injection of electrons, and Alq3 (tris (8-hydroxyquinolino) aluminum), PBD, TAZ, spiro-PBD, BAlq or SAlq may be used, .

The electron injection layer 135 may be formed by vacuum evaporation of organic and inorganic materials forming the electron injection layer, but is not limited thereto.

Here, the hole injection layer 131 or the electron injection layer 135 may further include an inorganic material, and the inorganic material may further include a metal compound. The metal compound may include an alkali metal or an alkaline earth metal. Metal compound including an alkali metal or alkaline earth metal LiQ, LiF, NaF, KF, RbF, CsF, FrF, BeF 2, MgF 2, CaF 2, SrF 2, BaF any one selected from the group consisting of ₂ and RaF ₂ or more But is not limited thereto.

That is, the inorganic material in the electron injection layer 135 facilitates hopping of electrons injected from the second electrode 140 into the light emitting layer 133 to balance the holes and electrons injected into the light emitting layer 133 The luminous efficiency can be improved.

The inorganic material in the hole injection layer 131 reduces the mobility of holes injected from the first electrode 120 into the light emitting layer 133 to balance the holes and electrons injected into the light emitting layer 133, Can be improved.

The present invention is not limited to FIG. 3, and at least one of the electron injection layer 135, the electron transport layer 134, the hole transport layer 132, and the hole injection layer 131 may be omitted.

Referring again to FIG. 1, a plurality of sub-pixels P included in the display unit DP may be driven by a driving unit DR to display an image. The driving unit DR can receive various driving signals and the like required for driving from the outside through the pad unit PD located on the substrate 110. [ Accordingly, the driving unit DR can generate a scan signal, a data signal, and the like corresponding to various driving signals supplied from the outside, and can supply the generated scan signals, data signals, and the like to the display unit DP.

The driving unit DR may include a scan driver for supplying a scan signal to a plurality of subpixels P and a data driver for supplying a plurality of subpixels with a data signal. The scan driver and the data driver may be located outside the substrate 110 or the substrate 110. The scan driver and the data driver may be disposed outside the substrate 110 or the substrate 110. For example, have.

Hereinafter, an organic light emitting display according to an exemplary embodiment of the present invention will be described in detail with reference to a scan driver, a data driver, and a display unit.

4 is a schematic block diagram of an organic light emitting display according to an embodiment of the present invention.

As shown in FIG. 4, an organic light emitting display according to an embodiment of the present invention may include a display unit DP including a plurality of sub-pixels P. FIG. In addition, it may include a scan driver SDR for supplying a scan signal to the display unit DP. The data driver may further include a data driver (DDR) for converting an image data signal supplied from the outside into an analog data signal and a digital data signal according to a gray level and mixing and supplying the analog data signal and the digital data signal to the display unit DP.

The data driver DDR determines the gradation of the video data signal as a higher bit group and a lower bit group. If the gradation of the video data signal is a higher bit group, the video data signal is converted into an analog data signal. If it is a lower bit group, the image data signal can be converted into a digital data signal.

In order to drive as described above, the data driver DDR may include a determination unit COMP, an analog driver DDR1, and a digital driver DDR2.

When the video data signal is supplied to the data driver DDR, the determination unit COMP can determine whether the gradation of the supplied video data signal is a high bit group or a low bit group. Also, the analog driving unit DDR1 may convert the image data signal corresponding to the upper bit group received from the determination unit COMP into an analog data signal and output the analog data signal. The digital driving unit DDR2 may convert the image data signal corresponding to the lower bit group received from the determination unit COMP into a digital data signal and output the digital data signal.

The data driver DDR may determine the lower 3 bits to 4 bits of the gray level of the image data signal as a lower bit group and determine the remaining bits as a higher bit group. Alternatively, when an image is represented by 8 bits, the range of the lower bit group may be determined with the data loading condition and the frame frequency supplied to the display unit DP, and the range may be set by digital driving.

That is, the determination criterion of the upper bit and the lower bit may vary depending on the number of the plurality of subframes constituting the video data signal and the data loading condition. However, in the present invention, description will be made on the assumption that the number of the plurality of subframes constituting the video data signal is four, that is, eight bits.

Here, it is referred to that the video data signal supplied from the outside to the data driver DDR is a digital video data signal and the digital video data signal is composed of one frame including a plurality of subframes.

The data driver DDR may include a first switch S1 located between the output terminals of the analog driver DDR1 and a second switch S2 located between the output terminals of the digital driver DDR2 .

The first switch S1 included in the data driver DDR may be switched to selectively supply the analog data signal and the digital data signal to the display unit DP. The data driver DDR can output the control signal through the second switch S2 so that the subpixel P is selectively supplied with the analog data signal and the digital data signal and is driven in the analog mode and the digital mode.

The control signal output from the second switch S2 included in the data driver DDR may output a logic high signal or a logic low signal as a digital signal.

When a control signal corresponding to a logic high or logic low signal is output as described above, the subpixel P supplied thereto can operate in an analog mode and a digital mode by a circuit constructed therein.

Hereinafter, the circuit configuration of the subpixel configured to receive the driving signals from the data driver DDR and the scan driver SDR and to vary the gray level representation will be described in more detail. However, the circuit configuration of Fig. 5 is only a sub pixel circuit structure for explaining an example of the embodiment, but the present invention is not limited to this.

5 is a diagram illustrating a circuit configuration of a subpixel according to an embodiment of the present invention.

5, the subpixel has a gate connected to the first scan line SCAN1 [m], one end connected to the data line IDATA [n], and the other end connected to the first node A 1 switching transistor SW1. The second switching transistor SW2 has a gate connected to the second scan line SCAN2 [m], one end connected to the control line DA [n], and the other end connected to the second node B . In addition, the third switching transistor SW3 may include a third switching transistor SW3 whose gate is connected to the second node B, one end is connected to the first node A, and the other end is connected to the third node C. The fourth switching transistor SW4 may include a gate connected to the second scan line SCAN2 [m], one end connected to the third node C, and the other end connected to the fourth node D . In addition, a fifth switching transistor SW5 having a gate connected to the first scan line SCAN1 [m] and one end connected to the fourth node D may be included. The driving transistor TR1 may include a gate connected to the third node C, one end connected to the first power supply line VDD, and the other end connected to the fourth node D. The organic light emitting diode OLED may have a first electrode connected to the other end of the fifth switching transistor SW5 and a second electrode connected to the second power supply line VSS. In addition, a first capacitor C1 having one end connected to the second node B and the other end connected to the first power supply line VDD may be included. In addition, a second capacitor C2 having one end connected to the first power supply line VDD and the other end connected to the third node C may be included.

Here, the first through fourth switching transistors SW1, SW2, SW3, and SW4 may be a P-type transistor and the fifth switching transistor SW5 may be an N-type transistor, but the present invention is not limited thereto. The transistors SW1, SW2, SW3, SW4, SW5, and TR1 included in the subpixel P may be poly transistors but are not limited thereto.

Here, according to the sub-pixel circuit configuration as described above, the organic light emitting display device can be driven by the following driving waveforms.

6 is a diagram illustrating driving waveforms for explaining a driving method according to an embodiment of the present invention.

6, the subpixel can receive the first scan signal scan1 [m] output from the scan driver through the first scan line SCAN1 [m], and the second scan signal scan2 [m]) can be supplied through the second scan line SCAN2 [m]. Further, the subpixel cell can receive the analog and digital data signals idata [n] output from the data driver through the data line iDATA [n]. Further, the subpixel can receive the control signal da [n] output from the data driver through the control line DA [n].

Here, if the first scan signal SCAN1 [m] corresponding to a logic low is supplied to the subpixel through the first scan line SCAN1 [m], the first switching transistor SW1 can be turned on, The switching transistor SW5 can be turned off.

When the second scan signal SCAN2 [m] corresponding to the logic low is supplied to the subpixel through the second scan line SCAN2 [m], the second switching transistor SW2 and the fourth switching transistor SW4 are turned on, Can be turned on. At this time, depending on whether the control signal da [n] supplied through the control line DA [n] is logic high or logic low, the charge amount in the first capacitor C1 may be varied, And may be selected as an analog mode or a digital mode depending on the charged amount of the capacitor C1. That is, when the logic high signal is supplied from the control line DA [n], the logic circuit operates in the analog mode and when the logic low signal is supplied from the control line DA [n] .

Thereafter, when a data signal corresponding to each gradation is supplied through the data line IDATA [n], the corresponding data voltage can be stored in the second capacitor C2 included in the subpixel, and the organic light emitting diode OLED Can emit light.

In operation in the analog mode, the corresponding gray-scale can be expressed by the driving current of the driving transistor TR1. In operation in the digital mode, the sub-pixel is gray-scaled corresponding to the emission time of the organic light- Can be expressed.

A driving method of an organic light emitting display including the above-described structure may be as follows.

7 is a driving flowchart for explaining an embodiment of the present invention.

The driving method according to an embodiment of the present invention may include a determining step (S102), a converting step (S104), and a supplying step (S108).

The determination step S102 is a step of determining whether the grayscale of the video data signal supplied from the outside is an upper bit group or a lower bit group.

For this, in the determination step (S102), it is possible to determine whether the gradation of the image data signal supplied from the outside is a higher bit group or a lower bit group by using a determination unit (COMP) included in the data driver (DDR).

Here, the data driver DDR may determine the lower 3 bits to 4 bits of the gradation of the image data signal as a lower bit group, and determine the remaining bits as a higher bit group. However, the determination criterion of the upper bit and the lower bit may be different depending on the number of the plurality of subframes constituting the video data signal. However, in the present invention, description will be made on the assumption that the number of the plurality of subframes constituting the video data signal is four, that is, eight bits.

Here, it is referred to that the video data signal supplied from the outside to the data driver DDR is a digital video data signal and the digital video data signal is composed of one frame including a plurality of subframes.

The conversion step S104 is a step of converting the image data signal corresponding to the higher bit group into the analog data signal and the image data signal corresponding to the lower bit group into the digital data signal.

For this, in the conversion step S104, the image data signal corresponding to the upper bit group received from the determination unit COMP using the analog driving unit DDR1 may be converted into an analog data signal and output. Further, the image data signal corresponding to the lower bit group received from the determination unit COMP using the digital driving unit DDR2 can be converted into a digital data signal and output.

On the other hand, after the conversion step (S104), a setting step (S106) of supplying a control signal to the subpixel such that the subpixel selectively supplied with the analog data signal and the digital data signal is driven in the analog mode and the digital mode have.

For this, in the conversion step S104, the first switch S1 included in the data driver DDR may be used to selectively supply the analog data signal and the digital data signal to the display unit DP.

And the second switch S2 can be used so that the subpixel P is selectively supplied with the analog data signal and the digital data signal and is driven in the analog mode and the digital mode. At this time, the control signal output from the second switch S2 included in the data driver DDR may output a logic high signal or a logic low signal as a digital signal. When a control signal corresponding to a logic high or logic low signal is output as described above, the subpixel P supplied thereto can operate in an analog mode and a digital mode by a circuit constructed therein.

The supply step S108 is a step of supplying the analog data signal and the digital data signal to the subpixel.

To this end, in the supplying step S108, the first scan signal and the second scan signal are supplied to the subpixel using the scan driver SDR, and the analog data signal and the digital data signal are supplied using the data driver DDR .

Hereinafter, a driving method according to an embodiment of the present invention will be described with reference to subpixels arranged in a 3 * 3 form, one frame data signal, and driving waveform examples. However, in the following description of the driving method according to the embodiment of the present invention, FIGS. 4 and 5 will be referred to together to improve understanding.

8 is a layout diagram of subpixels for explaining a driving method according to an embodiment of the present invention.

As shown in FIG. 8, to explain a driving method according to an embodiment of the present invention, subpixels are arranged in a 3 * 3 form as an example.

In this figure, (1) shows high gradation and low gradation level to be supplied to the 3 * 3 subpixel located on the display unit DP, and (2) high gradation is the analog data signal AD is supplied and the low gradation indicates that the digital data signal DD is supplied.

The data driver DDR may use the determination unit COMP, the analog driver DDR1, and the digital driver DDR2 as described above to express the gradation.

Accordingly, the high gray (HG) corresponding to the upper bit is converted into the analog data signal AD and supplied to the corresponding subpixel, and the lower gray (LG) corresponding to the lower bit is converted into the digital data signal DD And can be supplied to the corresponding subpixel.

On the other hand, according to the above-described assumption, one frame can be supplied to the subpixel in the following manner.

9 is a schematic diagram of a frame data signal for explaining a driving method according to an embodiment of the present invention. It is assumed that one frame data signal (1 Frame) supplied to the subpixel P is composed of four subframes (SF1, SF2, SF3, SF4), that is, 8 bits Lt; / RTI >

As shown in FIG. 9, the data driver DDR may program the sub-pixel by supplying the first sub-frame SF1 corresponding to the upper bit as an analog data signal. In addition, the operation mode of the subpixel can be set to the analog or digital mode using the control signal output from the data driver DDR. At this time, the interval during which the first subframe SF1 is supplied may be an interval in which an analog program and a mode setting (Analog Program & Mode Setting) can be performed.

Here, when the mode is set in a period in which the first sub-frame SF1 is supplied, the second sub-frame SF2, the third sub-frame SF3, and the fourth sub-frame SF4, You can program with digital data signals.

The 3 * 3 subpixels supplied with the first to fourth subframes SF1 to SF4 can perform operations corresponding to the supplied data signals, respectively. Accordingly, the first sub-frame SF1 can express a desired high gradation according to the driving current of the driving transistor TR1 driven corresponding to the data voltage stored in the second capacitor C2. In addition, the second to fourth sub-frames SF2 to SF4 except for the first sub-frame SF1 can display a desired low gray scale by controlling the emission time according to the first scan signal scan1 [n].

Here, it can be assumed that " I _Gray "in the figure is a state in which an analog or digital data signal is held," 1 "in the drawing can be assumed to be a gradation representation state corresponding to an analog data signal, Can be assumed to be a gradation representation state corresponding to the digital data signal.

The present invention provides an organic light emitting display having a hybrid compensation method using an analog current compensation method and a digital voltage driving method. By using the hybrid compensation method as described above, improved image quality can be realized compared with the conventional compensation method. In addition, since the lower 3 bits to 4 bits can be removed from the output channel of the analog driving unit included in the data driver, that is, the current DAC (Digital to Analog Converter), the problem of current offset can be solved, Can be lowered and a simple driving method can be provided. Also, the present invention can provide ease in realizing a large-area organic light emitting display device by separately supplying low-gradation gamma and high-gradation gamma.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be practiced. It is therefore to be understood that the embodiments described above are to be considered in all respects only as illustrative and not restrictive. In addition, the scope of the present invention is indicated by the following claims rather than the detailed description. Also, all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included within the scope of the present invention.

1 is a schematic plan view of an organic light emitting display according to an embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic light emitting display.

FIG. 3 is a hierarchical structure view of the organic light emitting diode shown in FIG. 2. FIG.

4 is a schematic block diagram of an organic light emitting display according to an embodiment of the present invention.

5 is a diagram illustrating an exemplary circuit configuration of a subpixel according to an embodiment of the present invention.

6 is a diagram illustrating a driving waveform for explaining a driving method according to an embodiment of the present invention.

7 is a driving flow chart for explaining an embodiment of the present invention.

8 is a layout diagram of subpixels for explaining a driving method according to an embodiment of the present invention.

9 is a schematic diagram of a frame data signal for explaining a driving method according to an embodiment of the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS

DP: Display P: Sub-pixel

DDR: data driver SDR: scan driver

DDR1: Analog driver DDR2: Digital driver

COMP:

Claims (15)

A display section; A scan driver for supplying a scan signal to the display unit; And And a data driver for converting an image data signal supplied from the outside into an analog data signal and a digital data signal according to gray levels and supplying the analog data signal and the digital data signal to the display unit, The data driver may include: A first switch located between the output terminal of the analog driving section and the data line connected to the sub pixel, and a second switch positioned between the output terminal of the digital driving section and the control line connected to the sub pixel, Wherein the first switch is operated so that the analog data signal and the digital data signal are selectively supplied to the display unit. The method according to claim 1, The data driver may include: The gradation of the image data signal is determined as an upper bit group and a lower bit group, and if the gradation of the image data signal is the upper bit group, the image data signal is converted into the analog data signal, And converts the image data signal into the digital data signal if the data is a lower bit group. 3. The method of claim 2, The data driver may include: The lower 3 bits to 4 bits of the gradation of the image data signal are determined as the lower bit group and the remaining bits are determined as the upper bit group. The method according to claim 1, The data driver may include: A determination unit determining whether the gradation of the image data signal is an upper bit group or a lower bit group; The analog driving unit converting the video data signal corresponding to the upper bit group received from the determination unit into the analog data signal and outputting the analog data signal; And And a digital driver for converting the image data signal corresponding to the lower bit group received from the determination unit into the digital data signal and outputting the digital data signal. delete The method according to claim 1, The data driver may include: Wherein the subpixel is selectively supplied with the analog data signal and the digital data signal and outputs a control signal through the second switch so as to be driven in an analog mode and a digital mode. The method according to claim 1, The sub- A first switching transistor having a gate connected to the first scan wiring and a first end connected to the data wiring and the other end connected to the first node, a gate connected to the second scan wiring, a first end connected to the control wiring, A third switching transistor having a gate connected to the second node and having one end connected to the first node and the other end connected to the third node, a gate connected to the second scan wiring, A fourth switching transistor having one end connected to the third node and the other end connected to the fourth node, a fifth switching transistor having a gate connected to the first scan wiring and one end connected to the fourth node, A driving transistor having a gate connected to the first power supply line, one end connected to the first power supply line and the other end connected to the fourth node, and a first electrode connected to the other end of the fifth switching transistor A first capacitor having one end connected to the second node and the other end connected to the first power supply line, and a second capacitor having one end connected to the first power supply line, And a second capacitor connected at the other end to the third node. 8. The method of claim 7, The sub- Wherein the organic light emitting display device operates in an analog mode when a logic high signal is supplied from the control wiring and operates in a digital mode when a logic low signal is supplied from the control wiring. 8. The method of claim 7, Wherein, in the operation in the analog mode, the subpixel has a gradation corresponding to a driving current of the driving transistor, Wherein the subpixels represent a corresponding gray level according to an emission time of the organic light emitting diode when the organic light emitting diode is operated in the digital mode. 8. The method of claim 7, Wherein the first to fourth switching transistors are P-type transistors and the fifth switching transistor is an N-type transistor. 8. The method of claim 7, The transistors included in the sub- An organic light emitting display device which is a poly transistor. A determination step of determining whether the grayscale of the video data signal supplied from the outside is an upper bit group or a lower bit group; A conversion step of converting the image data signal corresponding to the higher bit group into an analog data signal and converting the image data signal corresponding to the lower bit group into a digital data signal; A setting step of supplying a control signal to the subpixel such that the subpixel selectively supplied with the analog data signal and the digital data signal is driven in an analog mode and a digital mode; And And supplying the analog data signal and the digital data signal to the subpixel. 13. The method of claim 12, In the determination step, And determining the remaining bits as the lower bit group if the gradation of the image data signal is a lower 3 bits to 4 bits. delete 13. The method of claim 12, In the analog mode, the subpixels are expressed with gradations corresponding to driving currents of the driving transistors included in the subpixels, Wherein the sub-pixel has a gray level corresponding to an emission time of the organic light emitting diode included in the sub-pixel when the digital mode is operated.

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