KR101378855B1 - Organic Light Emitting Display and Method of Driving the same - Google Patents

Abstract

The present invention provides a switching transistor for driving in response to a scan signal, a capacitor for receiving a data signal as the switching transistor drives and storing the data signal as a data voltage, a driving transistor for driving in response to the data voltage stored in the capacitor; The organic light emitting diode may include an organic light emitting diode that receives power as the driving transistor is driven and emits light, and a sensing transistor that is driven to sense a threshold voltage of the driving transistor and is connected to one end and the other end of the driving transistor and has a gate connected to the sensing signal line. A display unit in which a plurality of subpixels are arranged; A scan driver supplying a scan signal; And a data driver configured to supply a data signal, wherein the capacitor provides an organic light emitting display device that receives a reference voltage greater than or equal to the ground voltage below the power supply from a reference voltage line when the sensing transistor is driven.

Organic light emitting display device, threshold voltage, data correction

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 light emitting display device used in an organic light emitting display device is a self-light emitting device having a light emitting layer formed between two electrodes positioned 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 the organic light emitting display device, when a scan signal, a data signal, and a power are supplied to a plurality of subpixels arranged in a matrix form, the selected subpixels emit light to display an image.

Meanwhile, in such an organic light emitting display device, the driving transistor must be continuously turned on in order for the organic light emitting diode to emit light. Therefore, when the driving signal is continuously supplied to the gate of the driving transistor, there is a problem that the threshold voltage Vth increases and the current flow decreases with time. If such a phenomenon continues, the performance of the driving transistor deteriorates and the organic light emitting diode can not be normally emitted, and the lifetime of the panel is also shortened and reliability is lowered.

SUMMARY OF THE INVENTION An object of the present invention is to provide an organic light emitting display device and a driving method thereof that can solve a problem in which a driving transistor deteriorates with time.

According to the above-mentioned problem solving means, the present invention provides a switching transistor for driving in response to a scan signal, a capacitor for receiving a data signal as the switching transistor is driven to store the data signal as a data voltage, and a data voltage stored in the capacitor. Drive transistors, an organic light emitting diode that receives power as the drive transistors emit light, and drives to sense threshold voltages of the drive transistors, and is connected to one end and the other end of the drive transistors and is gated to a sensing signal line. A display unit in which a plurality of subpixels including sensing transistors connected to each other are disposed; A scan driver supplying a scan signal; And a data driver configured to supply a data signal, wherein the capacitor provides an organic light emitting display device that receives a reference voltage greater than or equal to the ground voltage below the power supply from a reference voltage line when the sensing transistor is driven.

The data driver may detect a threshold voltage through a data line that supplies a data signal when the sensing transistor is driven, and adjust the data signal with reference to the detected threshold voltage.

The data driver may include a lookup table that is dataized corresponding to the threshold voltage, and adjust the data signal based on a correction coefficient included in the lookup table.

When the sensing transistor is driven, the capacitor may receive a reference voltage greater than the ground voltage below the power supply from the reference voltage wiring.

The power supply can switch below ground voltage when the sense transistor is driven.

The subpixel includes a switching transistor having a gate connected to a scan line and one end connected to a data line, an organic light emitting diode having a first electrode connected to a first power line, and one end connected to a second electrode of the organic light emitting diode and switching transistors. A driving transistor having a gate connected to the other end of the driving transistor and the other end connected to the second power supply wiring; a capacitor connected at one end to the gate of the driving transistor and the other end connected to the reference voltage wiring; It may include a sense transistor connected to the gate.

The transistors may be a-Si transistors.

In another aspect, the present invention provides a scan signal to one of a plurality of subpixels arranged in a display unit to drive a switching transistor, and to switch the power supplied to the subpixel to a ground voltage or less to a gate of a sensing transistor included in the subpixel. A sensing step of supplying a sensing signal to drive the sensing transistor and supplying a reference voltage to a capacitor included in the subpixel to sense a threshold voltage of the driving transistor included in the subpixel as a data driver; And selecting a correction coefficient included in the lookup table with reference to the threshold voltage, and adjusting a data signal based on the selected correction coefficient and supplying the data signal to the subpixel.

In the correction step, the correction coefficient may be data converted corresponding to the threshold voltage.

The sensing step may include a preparation step of supplying a scan signal to all subpixels to remove the previous data voltage before supplying the scan signal to the subpixels.

The reference voltage can be supplied after the preparation step.

The sensing step may be repeated one or more times every frame or random frame.

The reference voltage may be equal to or less than the ground voltage.

The present invention has the effect of providing an organic light emitting display device and a driving method thereof that can solve the problem that the driving transistor is deteriorated over time.

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 may include a display unit 120 on which a plurality of subpixels P are disposed. The plurality of subpixels P located on the substrate 110 are vulnerable to moisture or oxygen.

Thus, the sealing substrate 130 may be provided, and the adhesive member 140 may be formed on the outer substrate 110 of the display unit 120 to encapsulate the substrate 110 and the sealing substrate 130. Meanwhile, a plurality of sub-pixels P may be driven by a driving unit 150 positioned on the substrate 110 to display an image.

Here, the subpixel P may be defined as one unit pixel by bundling the red, green, and blue subpixels together. However, four or more subpixels P may be defined as one unit pixel, further including a subpixel emitting white or other colors (for example, orange, yellow, etc.).

The subpixel P may include at least an organic light emitting layer. The organic light emitting layer may further include at least one of a hole injecting layer, a hole transporting layer, an electron transporting layer, and an electron injecting layer. The organic light emitting layer may further include a buffer layer, a blocking layer, and the like so as to control the flow of holes or electrons between the anode and the cathode It is possible.

Although one driver 150 is shown on the substrate 110, the driver 150 may include a scan driver for supplying scan signals to sub pixels and a data driver for supplying data signals to the sub pixels .

Here, the scan driver may be divided into an even frame and an odd frame to supply a scan signal to subpixels on the left and right sides of the display unit.

Here, the data driver may adjust a data signal to be supplied to the subpixel. Detailed description thereof will be described below.

Hereinafter, the cross-sectional structure of the subpixel will be attached and described in more detail.

FIG. 2A is a cross-sectional exemplary view of the subpixel shown in FIG. 1, and FIG. 2B is another cross-sectional exemplary view of the subpixel shown in FIG.

As shown in FIG. 2A, the substrate 110 may be located. 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.) and the like.

A buffer layer 111 may be positioned on the substrate 110. The buffer layer 111 may be formed to protect a thin film transistor formed in a subsequent process from an impurity such as an alkali ion or the like flowing out from the substrate 110. The buffer layer 111 may be made of silicon oxide (SiO ₂ ), silicon nitride (SiN x), or the like.

The semiconductor layer 112 may be located on the buffer layer 111. The semiconductor layer 112 may comprise amorphous silicon or polycrystalline silicon crystallized therefrom. Although not shown here, the semiconductor layer 112 may include a channel region, a source region, and a drain region, and the source region and the drain region may be doped with P-type or N-type impurities.

A gate insulating layer 113 may be disposed on the substrate 110 including the semiconductor layer 112. The gate insulating layer 113 may be selectively formed using silicon oxide (SiO ₂ ), silicon nitride (SiNx), or the like.

The gate electrode 114 may be positioned on the gate insulating layer 113 to correspond to a channel region which is a predetermined region of the semiconductor layer 112. Gate electrode 114 is made of aluminum (Al), aluminum alloy (Al alloy), titanium (Ti), silver (Ag), molybdenum (Mo), molybdenum alloy (Mo alloy), tungsten (W), tungsten silicide (WSi ₂ ). ≪ / RTI >

The interlayer insulating film 115 may be positioned on the substrate 110 including the gate electrode 114. [ The interlayer insulating film 115 may be an organic film or an inorganic film, or a composite film thereof.

When the interlayer insulating film 115 is an inorganic film, it may include silicon oxide (SiO ₂ ), silicon nitride (SiNx), or silicate on glass (SOG). On the other hand, an organic film may include an acrylic resin, a polyimide resin, or a benzocyclobutene (BCB) resin. The first and second contact holes 115a and 115b for exposing a part of the semiconductor layer 112 may be disposed in the interlayer insulating film 115 and the gate insulating film 113. [

The first electrode 116a may be located on the interlayer insulating film 115. [ The first electrode 116a may be an anode and may have a single layer structure including a conductive layer such as indium tin oxide (ITO) or indium zinc oxide (IZO).

The first electrode 116a may include a conductive layer such as indium tin oxide (ITO) or indium zinc oxide (IZO) to have a multi-layer structure. The description thereof will be described in more detail with reference to the accompanying drawings.

Source and drain electrodes 116b and 116c may be located on the interlayer insulating film 115. [ The source and drain electrodes 116b and 116c may be electrically connected to the semiconductor layer 112 through the first and second contact holes 115a and 115b. A part of the drain electrode 116c may be located on the first electrode 116a and may be electrically connected to the first electrode 116a.

The source and drain electrodes 116b and 116c may include a low-resistance material for lowering the wiring resistance. The source and drain electrodes 116b and 116c may be formed of one selected from the group consisting of aluminum (Al), aluminum (Alnd), molybdenum (Mo), chromium (Cr), titanium nitride (TiN), molybdenum nitride And a metal layer such as a nitride (CrN) or the like. The description thereof will be described in more detail with reference to the accompanying drawings.

The transistor located on the substrate 110 includes the gate electrode 114, the source and drain electrodes 116b and 116c, and the transistor array having a plurality of transistors and capacitors can be electrically connected to the following organic light emitting diodes have. (However, the structure of the capacitor is omitted)

An insulating film 117 that exposes a part of the first electrode 116a may be disposed on the first electrode 116a (e.g., an anode). The insulating film 117 may include an organic material such as a benzocyclobutene (BCB) resin, an acrylic resin, or a polyimide resin.

The organic light emitting layer 118 may be disposed on the exposed first electrode 116a, and the second electrode 119 (eg, a cathode) may be positioned on the organic light emitting layer 118. The second electrode 119 may be a cathode that supplies electrons to the organic light emitting layer 118 and may include magnesium (Mg), silver (Ag), calcium (Ca), aluminum (Al) .

The organic light emitting diode connected to the source or drain electrodes 116b and 116c of the transistor included in the transistor array disposed on the substrate 110 includes the first electrode 116a, the organic light emitting layer 118, and the second electrode 119, . ≪ / RTI >

Unlike FIG. 2A, referring to FIG. 2B, the first electrode 116a positioned on the source or drain electrodes 116b and 116c may be positioned on the planarization layer 117a to planarize the surface of the transistor array. In this case, the insulating film 117b may be positioned to expose a part of the first electrode 116a (e.g., an anode) on the planarization film 117a.

2A and 2B, the structure of the transistor included in the transistor array may vary depending on whether the gate structure is the top gate or the batam gate. In addition, the structure of the transistor may vary depending on the number of masks used in forming the transistor array and the semiconductor layer material. Therefore, the cross-sectional structure of the subpixel is not limited thereto.

On the other hand, the organic light emitting display device according to an embodiment of the present invention can sense the threshold voltage of the driving transistor using a sensing transistor included in the sub-pixel, and adjust the data signal to be supplied to the sub-pixel using the sensed threshold voltage. have.

To this end, the subpixel includes a switching transistor for driving in response to a scan signal, a capacitor for receiving a data signal as the switching transistor drives and storing the data signal as a data voltage, and a driving transistor for corresponding to the data voltage stored in the capacitor. The organic light emitting diode may include an organic light emitting diode that receives power as the driving transistor is driven to emit light, and a sensing transistor that drives the sensing transistor to sense a threshold voltage of the driving transistor.

Hereinafter, with reference to the drawings shown in more detail.

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

3 illustrates a sensing transistor in a 2T1C structure including two transistors and one capacitor as one embodiment of the present invention, and the present invention is not limited to the 2T1C structure.

As illustrated in FIG. 3, the subpixel may include a switching transistor T1 having a gate connected to the scan line SCAN [n] and one end connected to the data line DATA [n]. In addition, the organic light emitting diode D may include an organic light emitting diode D connected to the first power line VDD. In addition, one end of the organic light emitting diode D may include a driving transistor T2 having one end connected to the other end of the switching transistor T1 and the other end connected to the second power line GND. . In addition, one end may be connected to the gate of the driving transistor T2, and the other end thereof may include a capacitor C connected to the reference voltage line VREF. In addition, the sensing transistor T3 may be connected to one end and the other end of the driving transistor T2 and connected to a gate of the sensing signal line VSENS.

The transistors T1, T2, and T3 may be a-Si transistors.

As the sensing transistor T3 is included in the subpixel, the data driver detects the threshold voltage of the driving transistor T2 through the data line DATA [n] for supplying a data signal when the sensing transistor T3 is driven. The data signal may be adjusted with reference to the detected threshold voltage.

Here, when the sensing transistor T3 is driven, the capacitor C may receive a reference voltage equal to or lower than a ground voltage from the reference voltage wiring VREF. However, when the sensing transistor T3 is not driven, the voltage supplied to the capacitor C through the reference voltage line VREF may be maintained below the ground voltage.

Herein, when the sensing transistor T3 is driven, the power supplied to the subpixel may be switched below the ground voltage. However, when the sensing transistor T3 is not driven, the power supplied to the subpixel through the first power line VDD may maintain the ground voltage or more.

That is, in the organic light emitting display device described above, the sensing transistor T3 connected to the source and the drain of the driving transistor T2 in order to improve the change in the threshold voltage Vth due to the positive shift which is a structural problem of the subpixel. It may be provided.

In addition, the power supplied to the first power line VDD may be switched to a power level higher than or equal to the ground voltage. In addition, the threshold voltage detected by the driving transistor T2 may be fed back to the data driver or the timing controller to correct the data signal and supply the corrected data signal to the corresponding subpixel.

In this case, when the sensing signal is supplied to the sensing signal line VSENS connected to the gate of the sensing transistor T3, the sensing transistor T3 may be driven. In this case, when the power supplied to the first power line VDD is switched to the ground voltage, the driving transistor T2 may be changed to a capacitor.

Hereinafter, the detailed description will be made with reference to FIG. 4 for detailed description.

FIG. 4 is an equivalent view of a part of the subpixel illustrated in FIG. 3.

Referring to FIG. 4, the subpixel circuit is equivalently shown in a state where the switching transistor included in the subpixel is turned off.

Here, the driving transistor T_Cg is changed to a capacitor as described above. For ease of understanding, the organic light emitting diode Cd is also shown as a capacitor.

As shown in FIG. 4, the voltage (threshold voltage) of the node A (A) may be determined by the voltage distribution of the capacitor C, the organic light emitting diode Cd, and the driving transistor T_Cg.

When the switching transistor is driven in this state, the data driver can detect the voltage (threshold voltage) of the node A (A) through the data line DATA [n]. Then, the data driver may generate the data signal based on the correction factor included in the lookup table with reference to the sensed voltage (threshold voltage) of the node A (A). Here, the correction coefficient may be data that corresponds to the threshold voltage.

Accordingly, the data driver selects a correction coefficient included in the lookup table based on the threshold voltage, which is the voltage of node A (A), and adjusts the data signal to be supplied to the corresponding subpixel using the selected correction coefficient.

Hereinafter, the driving method of the organic light emitting display device described above will be described.

5 is an exemplary driving waveform diagram according to an embodiment of the present invention.

Referring to FIG. 5, in the method of driving an organic light emitting display device according to an embodiment of the present invention, the scan driver is divided into an even frame and an odd frame to supply a scan signal to a display unit. Although it is an example, it is not limited to this.

Referring to the driving waveform, a plurality of subpixels arranged on the display unit receive a scan signal Scan [1] .. Scan [n], and the subpixels receiving the scan signal supply a data signal Data [n]. The emission step of receiving and emitting light may be performed.

However, the subpixel emitting light may supply power Vdd to emit light in a general state. The sensing signal Vsens is not supplied, and the reference voltage Vref can maintain the ground voltage.

In this series of processes, as the scan signals supplied to the display unit are supplied to the even frame and the odd frame, the scan signals may be supplied as follows.

First, when a scan signal is supplied to an even frame, a subpixel positioned in the display may receive a scan signal from the left side. Next, when the scan signal is supplied to the odd frame, the sub-pixel located in the display may receive the scan signal from the right side.

In this case, the sub-pixel positioned in the display unit may perform the sensing step and the correction step regardless of the scan signal supplied to the even frame or odd frame. The description is referred to together with FIGS. 3 and 4 for ease of understanding.

In the sensing step Vth sensing, the switching transistor T1 may be driven by supplying a scan signal Scan [1] to one of a plurality of subpixels arranged in the display unit. In addition, the power supply Vdd supplied to the subpixel is switched to the ground voltage or less, and the sensing transistor T3 may be driven by supplying the sensing signal Vsens to the gate of the sensing transistor T3 included in the subpixel. In addition, the reference voltage Vref may be supplied to the capacitor C included in the subpixel to detect the threshold voltage of the driving transistor T2 included in the subpixel as the data driver. The reference voltage Vref may be equal to or less than a ground voltage.

Here, the sensing step (Vth Sensing) may be repeated one or more times every frame or random frame. That is, as described above, the Vth sensing may be performed irrespective of whether the scan signal is supplied as an even frame or an odd frame.

Meanwhile, the threshold voltage described above may be sensed through the gate of the driving transistor T2. For clarity, the description will be further described with reference to FIG. 4.

Referring to FIG. 4, the voltage (threshold voltage) of the node A (A) may be determined by the voltage distribution of the capacitor C, the organic light emitting diode Cd, and the driving transistor T_Cg.

When the switching transistor is driven in this state, the data driver can detect the voltage (threshold voltage) of the node A (A) through the data line DATA [n]. Then, the data driver may generate the data signal based on the correction factor included in the lookup table with reference to the sensed voltage (threshold voltage) of the node A (A). Here, the correction coefficient may be data that corresponds to the threshold voltage.

Accordingly, the data driver selects a correction coefficient included in the lookup table based on the threshold voltage, which is the voltage of the node A (A), and adjusts the data signal to be supplied to the corresponding subpixel using the selected correction coefficient.

On the other hand, in the sensing step Vth Sensing, the scan signal Scan [1] .. Scn [n] is applied to all the subpixels in order to remove the previous data voltage before supplying the scan signal Scan [1] to the subpixel. It may include a ready step (Ready) to supply. Accordingly, the reference voltage Vref may be supplied after the preparation step.

The reason why the scan signal Scan [1] .. Scn [n] is supplied to all the subpixels through the preparation step is parasitic due to the threshold voltage obtained from the subpixel to be detected in the Vth sensing. This is to prevent the value from being added. However, the preparation step does not necessarily have to be preceded.

Next, in the correcting step, the data driver may select a correction coefficient included in the lookup table with reference to the threshold voltage and adjust the data signal based on the selected correction coefficient to supply the subpixel. The correction coefficient used in the correction step may be data corresponding to the threshold voltage.

In order to solve the problem that the driving transistor deteriorates over time, the present invention includes a sensing transistor in a subpixel and an organic electric field capable of adjusting a data signal based on a threshold voltage of the driving transistor sensed as the sensing transistor is driven. There is an effect of providing a light emitting display device and a driving method thereof.

Accordingly, the present invention can improve display quality by maintaining the luminance of the panel uniformly through the compensation as described above, and has an effect of improving the lifetime.

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. Therefore, the embodiments described above are to be understood as illustrative and not restrictive in all aspects. 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.

FIG. 2A is an exemplary cross-sectional view of the subpixel shown in FIG. 1; FIG.

FIG. 2B is another cross-sectional exemplary view of the subpixel shown in FIG. 1; FIG.

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

4 is an equivalent view of a portion of the subpixel illustrated in FIG. 3;

5 is an exemplary drive waveform diagram according to an embodiment of the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS

110: substrate 120: display unit

130: sealing substrate 140: adhesive member

150: driver P: subpixel

DATA [n]: data wiring SCAN [n]: scan wiring

T1: switching transistor T2: driving transistor

T3: sensing transistor D: organic light emitting diode

VSENS: sense signal wiring VREF: reference voltage wiring

C: Capacitor VDD: First Power Wiring

GND: 2nd power supply wiring

Claims (13)

A switching transistor for driving in response to a scan signal, a capacitor for receiving a data signal as the switching transistor drives and storing the data signal as a data voltage, a driving transistor for driving in response to the data voltage stored in the capacitor; An organic light emitting diode that receives power as the driving transistor is driven and emits light, and is driven to sense a threshold voltage of the driving transistor, and a sensing transistor connected to one end and the other end of the driving transistor and having a gate connected to the sensing signal line. A display unit in which a plurality of subpixels including a plurality are disposed; A scan driver which supplies the scan signal; And And a data driver configured to supply the data signal, wherein the capacitor receives a reference voltage greater than or equal to the ground voltage from the reference voltage line when the sensing transistor is driven. The method of claim 1, The data driver may include: The organic light emitting display device when the sensing transistor is driven to sense the threshold voltage through a data line for supplying the data signal and to adjust the data signal with reference to the detected threshold voltage. 3. The method of claim 2, The data driver may include: And a data table corresponding to the threshold voltage, and adjusting the data signal based on a correction coefficient included in the table. delete The method of claim 1, And the power source switches below the ground voltage when the sensing transistor is driven. The method of claim 1, The sub- One end is connected to the switching transistor having a gate connected to the scan line and one end connected to the data line, the organic light emitting diode having a first electrode connected to a first power line, and one end connected to a second electrode of the organic light emitting diode and The driving transistor having a gate connected to the other end of the switching transistor and having the other end connected to the second power line, the capacitor having one end connected to the gate of the driving transistor and the other end connected to the reference voltage wiring, and one end and the other end of the driving transistor. And a sensing transistor connected to the gate and connected to a sensing signal line. Claim 7 has been abandoned due to the setting registration fee. The method of claim 1, The transistors, An organic light emitting display device which is an a-Si transistor. A scan signal is supplied to one of the plurality of subpixels arranged in the display unit to drive a switching transistor, the power supplied to the subpixel is switched to a ground voltage or less, and a sensing signal is supplied to a gate of a sensing transistor included in the subpixel. Sensing the threshold voltage of the driving transistor included in the sub-pixel by driving the sensing transistor and supplying a reference voltage to the capacitor included in the sub-pixel; And And selecting a correction coefficient included in the lookup table with reference to the threshold voltage, and adjusting a data signal based on the selected correction coefficient and supplying the data signal to the sub-pixel. 9. The method of claim 8, In the correction step, And the correction coefficient is data corresponding to the threshold voltage. 9. The method of claim 8, In the sensing step, And a preparation step of supplying a scan signal to all subpixels to remove a previous data voltage before supplying the scan signal to the subpixels. 11. The method of claim 10, The reference voltage is, A method of driving an organic light emitting display device to be supplied after the preparation step. 9. The method of claim 8, The detecting step, A method of driving an organic light emitting display device that is repeated one or more times every frame or random frame. 9. The method of claim 8, The reference voltage is, And a method of driving an organic light emitting display device that is equal to or less than the ground voltage.

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