KR20100042390A - Organic light emitting display - Google Patents

Abstract

PURPOSE: An organic light emitting display device is provided to improve the display quality by solving the afterimage of a display panel by solving non-uniform brightness. CONSTITUTION: A plurality of wirings comprises a data wiring, a signal wiring, and a power wiring. A sub pixel is connected to the plurality of wirings. A data driver(120) is connected to the data line. A scan driver(130) is connected to the signal wiring. A power unit(140) is connected to the power line.

Description

Organic Light Emitting Display

Embodiments of the present invention relate to an organic light emitting display device.

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 method, a bottom-emission method, or a dual-emission method according to a direction in which light is emitted. According to the driving method, it is divided into a passive matrix type and an active matrix type.

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.

On the other hand, the sub-pixel disposed in the conventional organic light emitting display device must keep the driving transistor turned on continuously to emit the organic light emitting diode. As a result, when the driving signal is continuously supplied to the gate of the driving transistor, a threshold voltage Vth increases and a current flow decreases with time. If this phenomenon continues, the performance of the driving transistor deteriorates, resulting in afterimages appearing on the panel or the organic light emitting diode not being normally emitted, and the life of the panel is shortened. In addition, in the conventional organic light emitting display device, when the amount of current supplied through the power line is large, since the power is lowered by the resistance and the amount of current of the power line, there is a problem of luminance unevenness in which the brightness is lowered and the brightness varies for each subpixel.

An embodiment of the present invention for solving the above problems of the background art is to improve the display quality by solving the luminance non-uniformity problem of the organic light emitting display device.

According to the above-described problem solving means, an embodiment of the present invention includes a plurality of wirings including a data wiring, a first signal wiring, a second signal wiring, a first power wiring and a second power wiring; A sub pixel connected to the plurality of wires; A data driver connected to the data line; And a scan driver connected to the first and second signal wires. And a power supply unit connected to the first and second power lines, wherein the sub-pixels are turned on by the first signal supplied through the first signal line to initialize the node A to the first voltage supplied through the first power line. A first transistor, a second transistor turned on by the second signal supplied through the second signal wiring, and initializing the node B to a third voltage supplied through the data wiring; and between the first power supply wiring and the node B. A first capacitor positioned, a second capacitor positioned between the node B and the node A, a third transistor driven by an effective data voltage charged to the second capacitor, and positioned between the third transistor and the second power supply wiring. The present invention provides an organic light emitting display device including an organic light emitting diode that emits light by driving a third transistor.

The voltage difference between the two capacitors may have a difference voltage corresponding to an amount obtained by subtracting the third voltage from the first voltage by maintaining the node A at the first voltage and the node B at the third voltage when the first transistor is turned off. Can be.

When the data voltage is supplied through the data wiring, the node A may be charged with an effective data voltage corresponding to the sum of the data voltage and the difference voltage.

The node B may be maintained at the effective data voltage by the first capacitor when the second transistor is turned off.

The third voltage may have a level between the first voltage and the second voltage.

The current (IOLED) flowing through the organic light emitting diode while the organic light emitting diode emits light may be represented by the following equation.

K is a constant value determined by the mobility and parasitic capacitance of the third transistor, V _GS is a difference voltage between the gate voltage (Vg) and the source voltage (Vs) of the third transistor, V _TH is the threshold voltage of the third transistor, V _{data_e} is a data voltage, VDD is a first voltage, V _{data_i} is a third voltage, and ΔV _data is a voltage corresponding to a threshold voltage and a mobility difference of a subpixel.

The scan driver may turn on the first transistor in a section in which the organic light emitting diode does not emit light.

The subpixel further includes a fourth transistor configured to sense a current (IOLED) flowing between the third transistor and the organic light emitting diode, and the data driver is configured to supply the data wiring according to the current (IOLED) sensed by the fourth transistor. The electronic device may further include a correction unit configured to adjust the data voltage.

After the first transistor is turned off, the fourth transistor may be turned on so as to overlap the interval in which the data voltage is supplied.

The subpixel may include: a first transistor having a gate connected to the first signal line, one end of the first power line, and the other end connected to the node A; A second transistor having a gate connected to the second signal line, one end connected to the data line, and the other end connected to the node B; A first capacitor connected between the first power line and the node B; A second capacitor coupled between Node A and Node B; A third transistor having a gate connected to the node A and one end connected to the first power line; And an organic light emitting diode having a first electrode connected to the other end of the third transistor and a second electrode connected to the second power line, wherein the first to third transistors may be formed of a P type.

The embodiment of the present invention has the effect of solving the problem of afterimages appearing on the display panel as well as the problem of luminance unevenness caused by the power supply drop to improve the display quality.

Hereinafter, with reference to the accompanying drawings, the specific content for the practice of the present invention will be described.

1 is a schematic configuration diagram of an organic light emitting display device according to an embodiment of the present invention.

As shown in FIG. 1, an organic light emitting display device according to an embodiment of the present invention includes a display panel 110 in which subpixels P connected to a plurality of wirings are arranged in a matrix form, and data wirings D1 to Dm. ) And a scan driver 130 connected to the first signal wires S11 to S1n and the second signal wires S21 to S2n, and the first power wires VDD1 to VDDm and the second power source wires. The power supply unit 140 may be connected to the power supply line VSS, and the timing controller 150 may control the data driver 120 and the scan driver 130.

The subpixels P disposed on the display panel 110 may include data wirings D1 to Dm, first signal wirings S11 to S1n, second signal wirings S21 to S2n, and first power wirings VDD1 to VDDm. ) And the second power supply wiring (VSS).

The data driver 120 converts the digital video data RGB into an analog data voltage in response to the data control signal DDC supplied from the timing controller 150 and supplies the converted data voltage to the data wirings D1 to Dm. Accordingly, the data driver 120 is connected to the data wirings D1 to Dm of the subpixel P disposed on the display panel 110 to supply data such as an effective data voltage to the subpixel P. FIG.

The scan driver 130 transmits the first signal and the second signal to the first signal wirings S11 to S1n and the second signal wirings S21 to S2n in response to the gate control signal GDC supplied from the timing controller 150. Can be supplied to Accordingly, the scan driver 130 is connected to the first signal wirings S11 to S1n and the second signal wirings S21 to S2n of the subpixel P disposed on the display panel 110, and thus the subpixel P is connected to the scan driver 130. The scan pulses, such as the first signal and the second signal, are supplied.

The power supply unit 140 supplies the first voltage and the second voltage to the first power lines VDD1 to VDDm and the second power line VSS of the sub-pixel P disposed on the display panel 110. The first voltage may have a voltage higher than the second voltage. The first power lines VDD1 to VDDm may be wired to be connected to all the sub pixels P, respectively, and the second power lines VSS may be commonly formed to be connected to all the sub pixels P.

The timing controller 150 not only supplies the digital video data RGB supplied from the outside to the data driver 120 but also uses the vertical / horizontal synchronization signal H.Vsync and the clock signal CLK. The control signals DDC and GDC for controlling the operation timing of the 120 and the scan driver 130 may be generated.

Hereinafter, the subpixel P shown in FIG. 1 will be described in more detail with reference to FIG. 2.

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

As shown in FIG. 2, the subpixel P has a first transistor having a gate connected to the first signal line S11, one end thereof connected to the first power line VDD1, and the other end connected to the node A (A). (T1) may be included. In addition, the subpixel P may include a second transistor T2 having a gate connected to the second signal line S21, one end connected to the data line D1, and the other end connected to the node B (B). . In addition, the subpixel P may include a first capacitor C1 connected between the first power line VDD1 and the node BB. In addition, the subpixel P may include a second capacitor C2 connected between the node A (A) and the node B (B). In addition, the subpixel P may include a third transistor T3 having a gate connected to the node A (A) and one end connected to the first power line VDD1. In addition, the subpixel P may include an organic light emitting diode OLED having a first electrode connected to the other end of the third transistor T3 and a second electrode connected to the second power supply line VSS.

On the other hand, in the embodiment of the present invention, the first to third transistors (T1 to T3) is formed as a P type as an example, but those skilled in the art may be formed to N type through this.

The operation of the circuit configuration of the sub-pixel P described above is as follows.

FIG. 3 is a driving waveform diagram of the subpixel of FIG. 2. However, in FIG. 3, the first voltage, the second voltage, and the third voltage are omitted. This is because the first voltage and the second voltage may be supplied in a form of maintaining a constant level of mutual potential, and the third voltage may have a level between the first voltage and the second voltage. to be. Hereinafter, the first voltage is represented by 'VDD', the second voltage is represented by 'VSS', and the third voltage is represented by 'Vdata_i'.

First, when the first signal S11 is supplied through the first signal line S11, the first transistor T1 is turned on. Then, the first voltage VDD applied to the first power line VDD1 is supplied to the node A (A) through the first transistor T1 so that the node A (A) is initialized to the first voltage VDD.

Next, when the second signal S21 is supplied through the second signal line S21 while the first transistor T1 is turned on, the second transistor T2 is turned on. Then, the third voltage Vdata_i supplied from the data line D1 is supplied to the node B B through the second transistor T2 so that the node B B is initialized to the third voltage Vdata_i.

Next, when the first transistor T1 is turned off in the period where the second transistor T2 is turned on, the node A (A) is maintained at the first voltage VDD and the node B (B) is the third voltage Vdata_i. The voltage difference between the both ends of the second capacitor C2 may have a difference voltage (VDD-Vdata_i) corresponding to an amount obtained by subtracting the third voltage (Vdata_i) from the first voltage (VDD).

Next, the voltage supplied through the data line D1 may be changed and supplied to the data voltage Vdata_e in the section where the second transistor T2 is turned on. In this case, the node A (A) may be charged with a valid data voltage Vdata_e + Vc2 corresponding to the amount Vc2 (the voltage charged in the second capacitor), which is the sum of the data voltage Vdata_e and the difference voltage.

Next, when the second transistor T2 is turned off, the node B B may be maintained at the valid data voltage Vdata_e + Vc2 by the first capacitor C1. At this time, the third transistor T3 is driven by the effective data voltage Vdata_e + Vc2 charged in the second capacitor C2, and the organic light emitting diode OLED is driven by the third transistor T3. It can emit light.

By the above operation, the current IOLED flowing in the organic light emitting diode OLED while the organic light emitting diode OLED emits light may be represented by Equation 1 below.

K is a constant value determined by the mobility and parasitic capacitance of the third transistor T3, V _GS is a difference voltage between the gate voltage Vg and the source voltage Vs of the third transistor T3, and V _TH is zero. The threshold voltage of the three transistors T3, V _{data_e} is a data voltage, VDD is a first voltage, V _{data_i} is a third voltage, and ΔV _data is a voltage corresponding to the threshold voltage and mobility difference of the subpixel P.

4 and 5 are diagrams for describing an emission operation of a subpixel.

Referring to FIG. 4, as a signal corresponding to the driving waveform shown in FIG. 3 is supplied to the wires connected to the subpixel P, the organic light emitting diode OLED included in the subpixel P may be divided into one frame ( It operates with a light emitting section and a non-light emitting section in a time axis (Time) direction in which scan signals V-scan including first and second signals S11 and S21 are supplied within one frame.

Referring to FIG. 5, the light emitting section described above typically includes the first transistor T1 based on the first signal S11 supplied in the next order from the section in which the second transistor T2 is turned off by the second signal S21. ) May be defined up to a section in which it is turned on. However, the light emission period may be performed from the period in which the third transistor T3 is driven to the period in which the driving is stopped by the effective data voltage Vdata_e + Vc2 charged in the second capacitor C2.

On the other hand, when the sub-pixel P operates with the light emitting and non-light emitting sections as described above, the scan driver 130 may turn on the first transistor T1 in a section in which the organic light emitting diode OLED does not emit light. . As a result, the third transistor T3 stops driving and is turned off during the non-light emitting period, thereby preventing the display panel 110 from being deteriorated. The display panel 110 retains an afterimage due to hysteresis of the third transistor T3. This can be alleviated.

Hereinafter, a subpixel according to another embodiment of the present invention will be described.

6 is a circuit diagram illustrating a subpixel according to another exemplary embodiment of the present invention.

As illustrated in FIG. 6, the first pixel having a gate connected to the first signal line S11, one end thereof connected to the first power line VDD1, and the other end connected to the node A (A) as shown in FIG. 6. (T1) may be included. In addition, the subpixel P may include a second transistor T2 having a gate connected to the second signal line S21, one end connected to the data line D1, and the other end connected to the node B (B). . In addition, the subpixel P may include a first capacitor C1 connected between the first power line VDD1 and the node BB. In addition, the subpixel P may include a second capacitor C2 connected between the node A (A) and the node B (B). In addition, the subpixel P may include a third transistor T3 having a gate connected to the node A (A) and one end connected to the first power line VDD1. In addition, the subpixel P may include an organic light emitting diode OLED having a first electrode connected to the other end of the third transistor T3 and a second electrode connected to the second power supply line VSS. In addition, the transistor may include a fourth transistor T4 having a gate connected to the third signal line S31, one end connected to the data line D1, and another end connected to the first electrode of the organic light emitting diode OLED.

On the other hand, in another embodiment of the present invention, the first to third transistors (T1 to T3) is formed as a P type as an example, but those skilled in the art may be formed to N type through this.

The operation of the circuit configuration of the sub-pixel P described above is as follows.

FIG. 7 is a driving waveform diagram of the subpixel of FIG. 6. However, in FIG. 7, the first voltage, the second voltage, and the third voltage are omitted. This is because the first voltage and the second voltage may be supplied in a form of maintaining a constant level of mutual potential, and the third voltage may have a level between the first voltage and the second voltage. to be. Hereinafter, the first voltage is represented by 'VDD', the second voltage is represented by 'VSS', and the third voltage is represented by 'Vdata_i'.

First, when the first signal S11 is supplied through the first signal line S11, the first transistor T1 is turned on. Then, the first voltage VDD applied to the first power line VDD1 is supplied to the node A (A) through the first transistor T1 so that the node A (A) is initialized to the first voltage VDD.

Next, when the second signal S21 is supplied through the second signal line S21 while the first transistor T1 is turned on, the second transistor T2 is turned on. Then, the third voltage Vdata_i supplied from the data line D1 is supplied to the node B B through the second transistor T2 so that the node B B is initialized to the third voltage Vdata_i.

Next, when the first transistor T1 is turned off in the period where the second transistor T2 is turned on, the node A (A) is maintained at the first voltage VDD and the node B (B) is the third voltage Vdata_i. The voltage difference between the both ends of the second capacitor C2 may have a difference voltage (VDD-Vdata_i) corresponding to an amount obtained by subtracting the third voltage (Vdata_i) from the first voltage (VDD).

Next, the voltage supplied through the data line D1 may be changed and supplied to the data voltage Vdata_e in the section where the second transistor T2 is turned on. In this case, the node A (A) may be charged with a valid data voltage Vdata_e + Vc2 corresponding to the amount Vc2 (the voltage charged in the second capacitor), which is the sum of the data voltage Vdata_e and the difference voltage.

Next, when the second transistor T2 is turned off, the node B B may be maintained at the valid data voltage Vdata_e + Vc2 by the first capacitor C1. At this time, the third transistor T3 is driven by the effective data voltage Vdata_e + Vc2 charged in the second capacitor C2, and the organic light emitting diode OLED is driven by the third transistor T3. It can emit light.

By the above operation, the current IOLED flowing in the organic light emitting diode OLED while the organic light emitting diode OLED emits light may be represented by Equation 2 below.

K is a constant value determined by the mobility and parasitic capacitance of the third transistor T3, V _GS is a difference voltage between the gate voltage Vg and the source voltage Vs of the third transistor T3, and V _TH is zero. The threshold voltage of the three transistors T3, V _{data_e} is a data voltage, VDD is a first voltage, V _{data_i} is a third voltage, and ΔV _data is a voltage corresponding to the threshold voltage and mobility difference of the subpixel P.

According to another embodiment of the present invention, the organic light emitting diode OLED included in the sub-pixel P is also shown in FIG. 4, and the first and second signals S11 and S21 within one frame. It operates with a light emitting section and a non-light emitting section in a time axis (Time) direction to which a scan signal (V-scan) including a) is supplied.

As described above with reference to FIG. 5, the light emitting period is typically the first transistor T1 by the first signal S11 supplied in the next order from the section in which the second transistor T2 is turned off by the second signal S21. ) May be defined as up to a section in which it is turned on. However, the emission period may be defined as a period from which the third transistor T3 is driven to a period when the driving is stopped by the effective data voltage Vdata_e + Vc2 charged in the second capacitor C2.

On the other hand, when the sub-pixel P operates with the light emitting and non-light emitting sections as described above, the scan driver 130 may turn on the first transistor T1 in a section in which the organic light emitting diode OLED does not emit light. . As a result, the third transistor T3 stops driving and is turned off during the non-light emitting period, thereby preventing the display panel 110 from being deteriorated. The display panel 110 retains an afterimage due to hysteresis of the third transistor T3. This can be alleviated.

Referring to FIG. 7, the subpixel P according to another embodiment of the present invention may perform an operation similar to the subpixel P described above with reference to FIGS. 2 to 5. However, there is a difference in driving of the data driver 120 and the scan driver 130 that interlock with the fourth transistor T4 included in the sub-pixel P, which will be described in more detail.

The scan driver 130 is connected to the gate of the fourth transistor T4 through the third signal wire S31. After the first transistor T1 is turned off, the scan driver 130 may turn on the third signal line S31 so that the fourth transistor T4 is turned on by partially overlapping the fourth transistor T4 in a section where the data voltage Vdata_e is supplied. Signal S31 can be supplied. However, the fourth transistor T4 is not driven every frame and may be temporarily driven if necessary.

When the fourth transistor T4 is turned on, the fourth transistor T4 can transfer the current IOLED flowing between the third transistor T3 and the organic light emitting diode OLED to the data driver 120. That is, the fourth transistor T4 may sense a current IOLED flowing through the organic light emitting diode OLED and transmit the sensed current to the data driver 120.

In this case, the data driver 120 may further include a correction unit which adds or subtracts a data voltage to be supplied to the data line D1 according to the current IOLED sensed by the fourth transistor T4. The correction unit compensates for the threshold voltage V _THP and the mobility μ _p of the subpixel P to alleviate the luminance non-uniformity problem.

When the sub-pixel P performs the above operation, it is possible to alleviate the hysteresis afterimage caused by the third transistor T3, and to compensate for the Mura through the data driver 120 and to reduce the power supply. It is possible to solve the problem of luminance unevenness due to the same time. When the sub-pixel P is configured in such a form, since the transistor does not require more transistors than the conventional structure, the reduction of the aperture ratio can be prevented while taking a compensation structure that can solve the luminance non-uniformity problem.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, the technical configuration of the present invention described above may be modified in other specific forms by those skilled in the art to which the present invention pertains without changing its technical spirit or essential features. It will be appreciated that it 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 shown by the claims below, rather than the above detailed description. In addition, all changes or modifications derived from the meaning and scope of the claims and equivalent concepts should be construed as being included in the scope of the present invention.

1 is a schematic configuration diagram of an organic light emitting display device according to an embodiment of the present invention.

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

3 is a driving waveform diagram of a sub-pixel of FIG. 2;

4 and 5 are diagrams for explaining the light emission operation of a sub-pixel.

6 is a circuit diagram illustrating a subpixel according to another exemplary embodiment of the present invention.

7 is a driving waveform diagram of a sub-pixel of FIG. 6;

<Explanation of symbols on main parts of the drawings>

110: display panel 120: data driver

130: scan driver 140: power supply

150: timing controller

Claims (10)

A plurality of wirings including a data wiring, a first signal wiring, a second signal wiring, a first power wiring and a second power wiring; A sub pixel connected to the plurality of wires; A data driver connected to the data line; And A scan driver connected to the first and second signal wires; And a power supply unit connected to the first and second power wirings, The sub pixel is, A first transistor turned on by the first signal supplied through the first signal wiring to initialize the node A to a first voltage supplied through the first power wiring, and a second supplied through the second signal wiring A second transistor that is turned on by the signal and initializes the node B to a third voltage supplied through the data line, a first capacitor positioned between the first power line and the node B, the node B and the node. A second capacitor positioned between A, a third transistor driven by an effective data voltage charged by the second capacitor, and a drive between the third transistor and the second power wiring and driven by the third transistor; An organic light emitting display device comprising an organic light emitting diode emitting light by a light emitting diode. The method of claim 1, The voltage difference between both ends of the second capacitor, When the first transistor is turned off, the node A is maintained at the first voltage and the node B is maintained at the third voltage, so that the node A has a difference voltage corresponding to a quantity obtained by subtracting the third voltage from the first voltage. An organic light emitting display device. The method of claim 2, The node A, When a data voltage is supplied through the data line, And the effective data voltage corresponding to the sum of the data voltage and the difference voltage. The method of claim 1, The node B, And when the second transistor is turned off, the first capacitor maintains the effective data voltage. The method of claim 1, The third voltage is, And a level between the first voltage and the second voltage. The method of claim 1, The organic light emitting display device according to claim 1, wherein the current (IOLED) flowing through the organic light emitting diode while the organic light emitting diode emits light is represented by the following equation.

K is a constant value determined by mobility and parasitic capacitance of the third transistor, V _GS is a difference voltage between the gate voltage Vg and the source voltage Vs of the third transistor, and V _TH is the third voltage. A threshold voltage of three transistors, V _{data_e} is a data voltage, VDD is the first voltage, V _{data_i} is the third voltage, and ΔV _data is a voltage corresponding to the threshold voltage and mobility difference of the subpixel. The method of claim 1, The scan driver, And the first transistor is turned on in a section in which the organic light emitting diode does not emit light. The method of claim 1, The sub pixel is, A fourth transistor configured to sense a current (IOLED) flowing between the third transistor and the organic light emitting diode, The data driver, And a correction unit configured to adjust a data voltage to be supplied to the data line according to the current (IOLED) sensed by the fourth transistor. The method of claim 8, The fourth transistor is, And after the first transistor is turned off, the organic light emitting display device is turned on to overlap the period in which the data voltage is supplied. The method of claim 1, The sub pixel is, A first transistor having a gate connected to the first signal line, one end of which is connected to the first power line, and the other end of which is connected to the node A; A second transistor having a gate connected to the second signal line, one end connected to the data line, and the other end connected to the node B; The first capacitor connected between the first power line and the node B; The second capacitor connected between the node A and the node B; The third transistor having a gate connected to the node A and one end connected to the first power line; And The organic light emitting diode having a first electrode connected to the other end of the third transistor and a second electrode connected to the second power line; And the first to third transistors are formed of P type.

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