KR101322151B1 - Organic Light Emitting Display and method for driving the same - Google Patents

Abstract

According to an exemplary embodiment of the present invention, a signal line including scan lines and data lines, a display unit including pixel circuits positioned in an area defined by the signal lines, and a data signal corresponding to each scan line are received from the outside. The present invention provides an organic light emitting display device including a signal processor for modulating and supplying data signals corresponding to scan lines at different modulation levels.

Description

Organic Light Emitting Display and Method for Driving the Same

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

2 is a block diagram illustrating an organic light emitting display device according to an embodiment of the present invention.

3 is a circuit diagram illustrating a pixel circuit of an organic light emitting display device according to an exemplary embodiment of the present invention.

4 is a block diagram illustrating a signal processor according to an exemplary embodiment of the present invention.

5A through 5C are graphs illustrating data signals, gate voltages of driving transistors, and voltages between the source and gate electrodes of the driving transistors, which are applied to the organic light emitting display, according to scan lines.

6A through 6C are graphs illustrating data signals applied to an organic light emitting display device, a gate voltage of a driving transistor, and a voltage between source and gate electrodes of a driving transistor for each scan line, according to an exemplary embodiment.

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

2. Description of the Related Art In recent years, the importance of flat panel displays (FPDs) has been increasing with the development of multimedia. In response, a number of liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays (FEDs), organic light emitting devices (Organic Light Emitting Devices), etc. Branch-type flat panel displays have been put into practical use.

In particular, the organic light emitting display device has a high response time with a response speed of 1 ms or less, low power consumption, and self-emission. In addition, there is no problem in the viewing angle, which is advantageous as a moving picture display medium regardless of the size of the apparatus. In addition, since it can be manufactured at a low temperature and the manufacturing process is simple based on the existing semiconductor process technology, it is attracting attention as a next generation flat panel display device.

In general, an organic light emitting display device is a display device that electrically excites fluorescent organic compounds and emits light, and performs voltage driving or current driving of N × M organic light emitting diodes (OLEDs) arranged in a matrix form. Programming to express an image. The organic light emitting display device may be driven by a passive matrix method and an active matrix method using a thin film transistor. The passive matrix method forms anodes and cathodes at right angles and selects and drives lines, whereas the active matrix method connects a thin film transistor to each pixel electrode and depends on the voltage maintained by a capacitor capacitance connected to the gate electrode of the thin film transistor. Drive.

The pixel circuit of the organic light emitting display device includes pixel circuits including at least a switching transistor, a capacitor, a driving transistor, and a light emitting diode, and includes a data signal applied to the gate electrode of the driving transistor and a reference voltage applied to the source electrode of the driving transistor. The diode emits light by the driving current generated by the difference of.

Since the pixel circuits are arranged in the form of rows and columns, wiring resistances vary according to their positions. In particular, since currents generated in the pixel circuits flow through the reference power line connected to the pixel circuit, a voltage higher than the ground voltage is applied to the reference power line, and a higher voltage is applied to the portion of the reference power line having a large amount of flowing current.

Therefore, the pixel circuits receive different reference voltages according to their positions due to the difference in the wiring resistance of the reference power line. This causes a luminance unevenness between the pixel circuits and reduces the brightness of the screen by reducing the brightness of the entire panel.

Accordingly, an object of the present invention is to provide an organic light emitting display device having improved screen quality by securing luminance uniformity between pixel circuits and increasing panel brightness.

In order to achieve the above object, the present invention provides a signal line including scan lines and data lines, a display unit including pixel circuits positioned in an area defined by the signal lines, and a plurality of scan lines from outside. The present invention provides an organic light emitting display device including a signal processor that receives a corresponding data signal and modulates a data signal corresponding to each scan line to a different modulation level.

Applying a selection signal to pixel circuits connected to the scan line through the scan lines to pixel circuits positioned at the intersections of the scan lines and the data lines, and receiving the data signals corresponding to the scan lines. Determining a modulation level of the data signals according to the order of a line, modulating the data signals according to the determined modulation level, converting the modulated data signals into analog data signals, and converting the pixel circuits through the data line. It provides a method of driving an organic light emitting display device comprising the step of supplying to the field.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

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

Referring to FIG. 1, an organic light emitting display device according to an embodiment of the present invention includes a display unit 110 and a eastern portion (not shown) for applying a driving signal to the display unit 110 on the substrate 100. And a pad unit 115 connected to the display unit 110 and the driving unit to transmit a driving signal to the display unit 110.

The display unit 110 includes a plurality of pixel circuits P11 -Pnm, each pixel circuit defined by signal lines including scan lines, data lines, power supply voltage lines, and reference voltage lines 170 (VSS1-VSSn). Is located in the area.

Here, the reference voltage lines 170 (VSS1-VSSn) may include a main reference voltage line 170 positioned at an edge of the display unit 110 and auxiliary reference voltage lines VSS1-VSSn connected to each pixel circuit. Can be.

The main reference voltage line 170 is positioned at both sides of the display 110 to reduce wiring resistance in the display 110, and the pixel circuits P11-Pnm may receive a reference voltage at both sides of the display 110. have.

2 is a block diagram illustrating an organic light emitting display device according to an embodiment of the present invention described above, and FIG. 3 is a circuit diagram illustrating a pixel circuit of an organic light emitting display device according to an embodiment of the present invention. .

Referring to FIG. 2, the organic light emitting display device includes a display unit 110, a scan driver 120, a data driver 130, a controller 140, a power supply unit 150, and a signal processor 180.

The display unit 110 includes the data lines D1 -Dm arranged in the first direction and the scan lines S1 -Sn and the data lines (D1 -Dm) crossing the first direction and arranged in the second direction. ) And pixel circuits P11 -Pnm positioned in an area where the scan lines S1 -Sn cross each other.

The control unit 140 outputs a control signal to the scan driver 120, the data driver 130, and the power supply unit 150, and the power supply unit 150 supplies the power voltage line 160 according to the control signal of the control unit 140. The voltage required for driving the display unit 110 is output through the VDD1-VDDm) and the reference power line 170 (VSS1-VSSn).

Here, the main reference power line 170 may be located at both sides of the display unit 110 to reduce the variation in wiring resistance in the panel.

The scan driver 120 outputs a scan signal to scan lines S1 -Sn connected to the scan driver 120 according to a control signal of the controller 140. Thus, the pixel circuits P11 -Pnm positioned in the display unit 110 are selected in response to the scan signals S1 -Sn.

The signal processor 180 receives data signals from the outside, modulates the data signals to have a different modulation level for each data signal corresponding to each scan line, and transmits the data signals to the data driver 130.

The data driver 130 may correspond to the data signals through the data lines D1 -Dm connected to the data driver 130 in synchronization with the scan signal output from the scan driver 120 according to the control signal of the controller 140. Applied to the pixel circuits 110. Accordingly, the display 110 displays an image image by emitting light from the pixel circuits P1-Pnm in response to the data signals.

Referring to FIG. 3, the pixel circuit receives data through a switching transistor T1 and a switching transistor T2 that transfer a data signal from the data line Dm in response to a selection signal from the scan line Sn. A capacitor Cst for storing a signal, a driving transistor T2 for generating a driving current according to a data signal stored in the capacitor Cst, a light emitting operation according to the driving current, and connected to a power supply voltage line VDD. Organic light emitting diodes (OLED).

The gate electrode of the driving transistor T2 is connected to the drain electrode of the switching transistor T1 to receive a data signal, and the driving transistor T2 is connected to the difference between the reference voltage line VSS and the data signal connected to the source electrode. The corresponding driving current is generated and supplied to the organic light emitting diode OLED connected to the drain electrode.

The amount of current flowing through the organic light emitting diode OLED can be expressed as follows.

t

t

Here, K is a constant, Vgs is the difference between the source-gate voltage of the driving transistor, and Vth is the threshold voltage of the driving transistor.

When a current is generated in the pixel circuit and the current flows through the reference voltage line VSS, a voltage higher than the reference voltage is applied to the node A by the current flowing in the reference voltage line and the wiring resistance R.

4 is a block diagram illustrating a signal processor according to an exemplary embodiment of the present invention.

Referring to FIG. 4, the signal processor 150 includes a plurality of look-up tables 153 and a signal modulator 155 in which different modulation levels are stored.

The signal processor 150 sequentially receives data signals corresponding to one scan line from the outside. Then, the modulation level of the data signals corresponding to each scan line is selected using the plurality of look-up tables 153, and the signal modulator 155 modulates the data signals according to the modulation level. Generated data signals.

In other words, the data signals to be input to the pixel circuits S11-S1m connected to the first scan line S1 and the data signals to be input to the pixel circuits Sn1-Snm connected to the last scan line Sn are modulated. Levels may vary. The modulation level of the data signals corresponding to the last scan line may be greater than the modulation level of the data signals corresponding to the first scan line.

In addition, modulation levels of data signals to be input to the pixel circuits Sn1 -Snm connected to the same scan line Sn may be different. The modulation level may increase in either direction depending on the position of the main reference power line 170 of FIG. 2. That is, in one embodiment of the present invention, the data signals to be input to the pixel circuits Sn1 -Snm connected to the same scan line Sn are modulated of the data signals as the position of the pixel circuits Sn1 -Snm approaches the center. The level can be increased.

Hereinafter, the modulation level will be described in detail with reference to FIGS. 2, 3, and 5A to 5C.

5A through 5C are graphs illustrating data signals applied to the organic light emitting display device, voltages of the node A of the driving transistor, and voltages of the source and gate electrodes of the driving transistor for each scan line and data line.

As shown in FIG. 5A, when data signals having the same magnitude are applied to all scan lines S1 -Sn of the organic light emitting display device, each scan line is illustrated in node A of FIG. 3 as shown in FIG. 5B. And voltages of different magnitudes are applied according to data lines.

This is due to the wiring resistance of the organic light emitting display device. As shown in FIG. 2, the reference voltage line VSSn connected to the pixel circuits connected to the nth scan line is connected to the nth scan line from the first scan line. Current generated from the pixel circuits flows. Therefore, since a large amount of current flows, a high voltage is applied to the node A of the pixel circuit connected to the nth scan line.

In addition, referring to FIG. 2, since the main reference voltage line 170 applying the reference voltage is located at both sides of the display unit 110, the reference voltage is the auxiliary reference voltage lines VSS1-VSSn through the main reference voltage line 170. Is applied from both sides along the Therefore, as the position of the data line connected to the pixel circuit moves away from both sides, the voltage of the node A becomes higher, and the result shown in the graph shown in FIG. 5B is obtained.

That is, since the wiring resistance is different for each scan line and data line, as illustrated in FIG. 5C, the magnitude of the voltage Vgs between the source and gate of the driving transistor also varies for each scan line and data line. Therefore, even if the same data is applied, all of the pixel circuits show different luminance, resulting in uneven luminance.

Accordingly, the signal processor 180 according to an embodiment of the present invention includes a look-up table 183 in which different modulation levels are stored so that data signals corresponding to each scan line can be modulated at different modulation levels. do. Each look-up table 183 may be set to have a different modulation level for each data line corresponding to each scan line.

Accordingly, the modulation level of the data signals corresponding to each scan line is determined by referring to the look-up table 183 in consideration of the order of the scan lines, and the signal modulator 185 refers to the selected look-up table. Modulate the data signals.

The modulated data signals may be transmitted to the converter 135, and the converter 135 converts the modulated data signals into analog data signals and transmits the analog data signals to the display unit 110.

Here, the signal processor may be located separately from the controller or the data driver, and may also be located in the data driver. The converter may be located in the data driver.

Hereinafter, a driving method of an organic light emitting display device according to an embodiment of the present invention will be described in detail with reference to FIGS. 2 to 4.

2 to 4, when a control signal is applied from the controller 140, the scan driver 120 applies a scan signal to the pixel circuits through the first scan line S1. Therefore, the pixel circuits S11-S1m connected to the first scan line are selected.

Data signals are input to the signal processor 180 from the outside. The signal processor 180 receives a data signal corresponding to the first scan line, and determines a modulation level using the first look-up table LUT1 183. Here, since the data signals are sequentially received for each scan line, the number of look-up tables (LUT1) 183 may be the same as the number of scan lines, and the order of the look-up tables may be specified in the order in which the data signals are received. Can be.

Then, the signal modulator 185 generates modulated data signals according to the modulation level stored in the look-up table LUT1 183.

Next, the modulated data signals are supplied to the data driver 130, and the data driver 130 converts the modulated data signals into analog data signals and supplies them to the pixel circuits S11-S1m connected to the first scan line. .

The pixel circuits S11-S1m receive a data signal, store a voltage corresponding to a difference between the reference voltage VSS and the data signal, and generate a driving current corresponding thereto to emit light.

The above operation may be repeatedly performed until the last scan line for one frame, and the data signals applied to the organic light emitting display device according to the exemplary embodiment of the present invention will be described below.

6A through 6C illustrate data signals applied to an organic light emitting display device according to an embodiment of the present invention, voltages of node A of a driving transistor, and voltages of source-gate electrodes of a driving transistor for each scan line and data line. The graphs shown.

Referring to FIG. 6A, a signal processor of an organic light emitting display device according to an embodiment of the present invention supplies a data signal modulated to different levels for each scan line and data line to a data driver. That is, the modulation level of the data signals corresponding to the last scan line may be greater than the data signals corresponding to the first scan line, and the modulation level may be larger as the data lines are located in the center.

Therefore, as shown in FIG. 6B, the voltage applied to the node A of the driving transistor of FIG. 2 is changed for each scan line and data line. As a result, as shown in FIG. 6C, for each scan line and data line. Since the voltage difference between the gate and the source of the driving transistor is constant, luminance uniformity between the pixel circuits can be ensured.

 While the invention has been shown and described with reference to certain preferred embodiments, the invention is not so limited, and the invention is not limited to the scope and spirit of the invention as defined by the following claims. It will be readily apparent to one of ordinary skill in the art that various modifications and variations can be made.

The present invention has the effect of improving the quality of the screen of the organic light emitting display device by ensuring the uniformity of the luminance between each pixel circuit.

Claims (10)

Signal lines including scan lines and data lines; A display unit including pixel circuits positioned in an area defined by the signal lines; And A signal processor that receives a data signal corresponding to each scan line from an external source, modulates the data signals corresponding to each scan line with a different modulation level, and The signal processing unit supplies a modulation level of the data signals corresponding to the last scan line larger than the data signals corresponding to the first scan line, and increases the modulation level of the data signals as the data lines are located in the center. An organic light emitting display device, characterized in that for supplying. The method of claim 1, And the signal processor modulates data signals corresponding to each scan line to different modulation levels for each data line. The method of claim 1, And a data driver for supplying a data signal to the pixel circuits through the data line. And the data driver receives modulated data signals, converts them into analog data signals, and supplies the converted data signals to the pixel circuits. The method of claim 1, The modulation level of the organic light emitting display device increases as the number of scan lines increases. The method of claim 1, The signal processing unit receives a data signal for one scan line from an external source, and looks up to determine a modulation level, and modulates the data signals according to a modulation level of the look-up table and supplies the data signal to a data driver. An organic light emitting display device comprising a portion. The method of claim 1, The pixel circuit may include a switching transistor that transfers a data signal from the data line according to a scan signal from the scan line, a capacitor that receives the data signal from the switching transistor and stores the data signal, and according to the data signal stored in the capacitor. An organic light emitting display device comprising: a driving transistor generating a driving current; and a light emitting diode receiving the driving current to perform a light emitting operation. Applying a selection signal to pixel circuits connected to the scan line through the scan lines to pixel circuits positioned at the intersections of the scan lines and the data lines; Determining a modulation level of the data signals according to the order of the scan lines by receiving data signals corresponding to the scan lines; Modulating data signals according to the determined modulation level; And Converting the modulated data signals into analog data signals and supplying the modulated data signals to the pixel circuits through the data line; The determining of the modulation level of the data signals may be performed by increasing the modulation level of the data signals corresponding to the last scan line, rather than the data signals corresponding to the first scan line. The method of driving an organic light emitting display device, characterized in that to increase the modulation level. The method of claim 7, wherein And a data signal corresponding to each scan line is modulated for each data signal corresponding to each data line. The method of claim 7, wherein Wherein the modulation level is different for each data signal corresponding to each scan line. 10. The method of claim 9, A method of driving an organic light emitting display device, wherein a modulation level of data signals corresponding to a last scan line is greater than a modulation level of data signals corresponding to a first scan line.

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