KR100666643B1 - Organic electro luminescent display device and operation method of the same - Google Patents

Abstract

An organic EL(Electro-Luminescence) display device and a driving method thereof are provided to improve the brightness of sub-pixels by adjusting a driving current according to the light emitting efficiencies of respective color sub-pixels. An organic EL display device includes a pixel unit(100), a scan driver(200), a data driver(300), a precharge unit(600), and a demultiplexer(500). The pixel unit includes red, green, and blue sub-pixels and displays an image. The scan driver supplies scan signals to the pixel unit. The data driver supplies data signals to the pixel unit according to a descending order of the light emitting efficiencies of the pixels. The precharge unit precharges data lines for transmitting the data signal to the pixels. The demultiplexer receives at least two data signals from the data driver and transmits the data signals to the sub-pixels according to a descending order of the light emitting efficiencies of the sub-pixels.

Description

Organic Electroluminescent Display Device and Operation Method of the same}

1 is a block diagram of a conventional organic light emitting display device.

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

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

4 is a characteristic diagram of a data voltage according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

100: pixel portion 200: scan driver

300: data driver 400: light emission control driver

500: demultiplexer 600: precharge unit

700: demultiplexer control unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting display device, and more particularly, to an organic light emitting display device for supplying a data signal using a demultiplexer. A light emitting display device is provided.

Recently, flat panel display devices that can replace cathode ray tubes (CRTs) have been actively researched. In particular, organic light emitting display devices have attracted attention as next-generation flat panel display devices due to their excellent luminance and viewing angle characteristics.

Unlike the liquid crystal display, the organic light emitting display device uses a light emitting diode that emits a specific light without requiring a separate light source unit. Such a light emitting diode emits light corresponding to the amount of driving current flowing into the anode electrode.

1 is a block diagram of a conventional organic light emitting display device.

The organic light emitting display device includes a pixel unit 10, a scan driver 20, a data driver 30, and a light emission control driver 40.

The scan driver 20 sequentially supplies scan signals to the scan lines S1 to Sn in response to a scan control signal from a timing controller (not shown), that is, a start pulse and a clock signal.

The data driver 30 supplies data voltages corresponding to the R, G, and B data to the data lines D1 to Dm in response to a data control signal supplied from a timing controller (not shown).

The light emission control driver 40 includes a shift register, and supplies the light emission control signals to the light emission control lines E1 to En sequentially in response to a start pulse and a clock signal from a timing controller (not shown).

The pixel unit 10 includes a plurality of pixels P11 to Pnm positioned in an area where a plurality of scan lines S1 to Sn, a plurality of data lines D1 to Dm, and a plurality of emission control lines E1 to En cross each other. And a predetermined image is displayed according to the applied data voltage.

One unit pixel (Pnm) is composed of red, green and blue subpixels.

The red, green, and blue subpixels of the pixel portion 10 have the same pixel circuit configuration, and emit red, green, and blue light corresponding to the current to which each organic EL element is applied. Accordingly, the pixel Pnm displays a specific color by combining light emitted from the red, green, and blue subpixels forming the pixel Pnm.

The organic light emitting display device includes m output lines to supply a data signal from the data driver 30 to the m data lines connected to the pixel unit 10. Therefore, m data integrated circuits supplying data signals to respective output lines are required. However, such data integrated circuits are difficult to provide as many as the number of data lines due to problems of panel area and manufacturing cost, and more data integrated circuits have to be provided as the number of pixels of the organic light emitting display device increases.

In order to solve the above problems, an organic light emitting display device including a demultiplexer has been proposed. In the organic light emitting display device including the demultiplexer, an output line of one data integrated circuit is connected to k data lines to sequentially turn on transistors of the demultiplexer to supply a data signal. Therefore, when three data lines are connected to one output line, the number of data integrated circuits is reduced to one third.

However, in the organic light emitting display device including the demultiplexer, the data signal is supplied from the demultiplexer for the same time regardless of the color of the subpixels. Therefore, when a black data signal is supplied to a subpixel having a low luminous efficiency, a large amount of current flows through the organic EL element, which makes it difficult to express a desired color.

An object of the present invention to solve the above problems is to provide a driving method for adjusting the driving order and driving time of the demultiplexer according to the luminous efficiency in an organic light emitting display device comprising a demultiplexer.

According to an aspect of the present invention, there is provided a driving method of an organic light emitting display device including a demultiplexer for supplying a data signal to red, green and blue data lines, and a precharge unit for precharging the data lines. Precharging the data lines by receiving a precharge voltage from the precharge unit during a blanking period between a previous scan section and a current scan section following the previous scan section; And supplying data signals from the demultiplexer in the order of colors having high luminous efficiency during the current scanning period.

In addition, the present invention for achieving the above object, the pixel portion including a red, green and blue sub-pixels for displaying a predetermined image; A scan driver for supplying a scan signal to the pixel portion; A data driver for supplying a data signal to the pixel portion; A precharge unit for precharging the data lines which transfer the data signal to the pixels; And a demultiplexer unit receiving two or more data signals from the data driver and transferring the two or more data signals to the data lines in an order of high luminous efficiency.

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

Example

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

Referring to FIG. 2, the organic light emitting display device according to the present exemplary embodiment includes a pixel unit 100, a scan driver 200, a data driver 300, a light emission control driver 400, a demultiplexer 500, and a pre-car. It is composed of the branch 600 and the demultiplexer control unit 700.

The pixel unit 100 includes a plurality of pixels P11 to Pnm formed in regions defined by a plurality of scan lines S1 to Sn, a plurality of emission control lines E1 to En, and a plurality of data lines DR1 to DBm. It is composed of Each pixel Pnm is composed of red, green, and blue subpixels PRnm, PGnm, and PBnm, and each of the data lines DRm, DGm, and DBm for applying a respective data signal from the data driver 300. Connected with

The red, green, and blue subpixels (PRnm, PGnm, PBnm) of the pixel Pnm have the same pixel circuit configuration. The red, green, and blue subpixels (PRnm, PGnm, and PBnm) emit red, green, and blue light corresponding to a current applied to the organic EL element OLED. Accordingly, the pixel Pnm displays a specific color by combining light emitted from the red, green, and blue subpixels PRnm, PGnm, and PBnm forming the pixel Pnm.

Since the plurality of data lines DR1 to DBm formed on the pixels P11 to Pnm are formed across the pixel unit 100, they have capacitance. The capacitance due to the data lines DR1 to DBm generates a loading effect when a data signal is applied from the data driver 300. That is, a phenomenon in which signal transmission is delayed due to generation of unwanted impedance components occurs. These capacitances are parasitic capacitors that are equivalently formed by insulating layers or metal wires formed by different layers from the data lines DBm on the data lines DBm and the pixels PB1m to PBnm.

The scan driver 200 sequentially supplies a scan signal to a plurality of scan lines S1 to Sn in synchronization with a scan control signal supplied from a timing controller (not shown), that is, start pulses and clock signals.

The emission control driver 400 may be configured as a shift register that outputs the emission control signal in synchronization with a control signal supplied from a timing controller (not shown), that is, a start pulse and a clock signal. In addition, the emission control driver 400 may not be separately provided, and may generate an emission control signal by performing a logical operation on an output signal or scan signals of the shift register output from the scan driver 200.

The data driver 300 receives R, G, and B data from a timing controller (not shown), and receives a control signal, that is, a horizontal synchronous signal and a vertical synchronous signal. The data driver 300 includes a plurality of data driver circuits for supplying a data signal to each of the data output lines DL1 to DLm, and each of the data driver circuits is R, G, B from a timing controller (not shown). Receive data and control signals.

Each of the data driving circuits includes a shift register for transferring data continuously supplied to each sampling latch in units of bits by a control signal, a sampling latch for sampling and receiving one bit of data from the shift register, and the sampled data. It consists of a holding latch for storing the digital-to-analog converter (D / A converter) for converting the stored data into an analog value. In addition, the data driving circuit may further include a level shifter for increasing the amplitude of the output signal of the holding latch and supplying the amplitude to the D / A converter.

The number of data supplied to each data driving circuit corresponds to the number of data lines DRm, DGm, and DBm connected to one demultiplexer 510. Therefore, when each data driving circuit is connected to the demultiplexer 510 for supplying data signals to three data lines DRm, DGm, and DBm connected to the red, green, and blue subpixels PRnm, PGnm, and PBnm, respectively. The data driver circuit receives three pieces of data of R, G, and B.

The data driving circuit samples the supplied R, G, and B data, and performs analog conversion to supply the R, G, and B data signals to the data output line DLm.

The demultiplexer unit 500 receives R, G, and B data signals from the plurality of data output lines DL1 to DLm and receives the plurality of data lines DR1 to DBm according to the demultiplexer control signals DMR, DMG, and DMB. Supply the data signal. The demultiplexer 500 is connected to a data output line DLm extending from each data driving circuit, and is composed of a plurality of demultiplexers 510 for receiving R, G, and B data signals.

Each demultiplexer 510 receives a data signal from a data output line DLm connected to one data driving circuit, and each data line DRm, DGm, and DBm according to a control signal supplied from the demultiplexer controller 700. Supply the data signal.

The demultiplexer 510 includes three transistors MRm, MGm, and MBm connected to the R, G, and B data lines DRm, DGm, and DBm, respectively, when three data signals are applied to R, G, and B. do.

Each transistor MRm is turned on by receiving the control signal DMR from the demultiplexer controller 700 to supply a data signal supplied from the data output line DLm to a corresponding data line DRm.

These transistors (MRm, MGm, MBm) are composed of a P-type MOSFET (Metal Oxide Semiconduct or Field Effect Transistor). Therefore, the transistors MRm, MGm, and MBm of the demultiplexer 500 may be formed by the same process as the transistors of the pixel circuit formed in the pixel unit 100. The demultiplexer 500 is formed on the same substrate as the pixel 100 to implement a system on panel (SOP).

The demultiplexer controller 700 supplies the same control signals DMR, DMG, and DMB to the plurality of demultiplexers 510 of the demultiplexer 500. Each control signal DMR is supplied to a transistor MRm connected to a data line DRm that supplies the same color of each demultiplexer 510, and simultaneously these transistors MR1, MR1, ... MRm Turn on In addition, the demultiplexer controller 700 controls the precharge unit 600 by supplying a precharge voltage Vpc and a precharge control signal pc to the precharge unit 600. The demultiplexer control unit 700 may be independently implemented as a single integrated circuit, or may be included in a timing controller (not shown) to control signals DMR, DMG, DG, and the like using the demultiplexer 700 and the precharge unit 600. DMB, Vpc, pc) can be supplied.

The precharge unit 600 is composed of a plurality of transistors PR1 to PBm connected to each data line DRm and supplying a precharge voltage Vpc.

The transistors PR1 to PBm receive the precharge control signal pc from the demultiplexer controller 700 and are simultaneously turned on to supply the precharge voltage Vpc to the plurality of data lines DR1 to DBm. The transistors PR1 to PBm forming the precharge unit 600 may be formed of P-type MOSFETs and may be formed through the same process as the transistors of the pixel unit 100. Therefore, the precharge unit 600 is formed on the same substrate as the pixel unit 600, and implements SOP like the demultiplexer unit 500. As described above, although the transistors MG1 to MBm and PG1 to PBm are illustrated as P type MOSFETs, the transistors MG1 to MBm and PG1 to PBm may be designed by the person skilled in the art. Will keep the same conduction type.

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

An operation of the organic light emitting display device of FIG. 2 will be described with reference to FIG. 3. In FIG. 3, an operation of the demultiplexer 510 connected to the m th data output line DLm and the pixels P1m to Pnm of the m th column that receives a data signal from the demultiplexer 510 will be described.

When the low level n−1 th scan signal is supplied from the scan driver 200 to the pixel unit 100, the pixels Pn−11 to Pn−1m positioned in the n−1th row are activated.

At this time, the demultiplexer control signals DMG, DMR, and DMB are supplied to the demultiplexer 500 to supply data signals to the subpixels in the order of colors having high luminous efficiency from the demultiplexer controller 700.

Hereinafter, luminous efficiency of the subpixels is lowered in the order of green, red, and blue subpixels (PG, PR, PB).

When the low level green demultiplexer control signal DMG is applied to the demultiplexer 510, the transistor MGm connected to the data line DGm for applying a data signal to the green subpixels PG1m to PGnm is turned on. . Therefore, the data signal of the green is transferred from the data driving circuit to the storage capacitor of the activated green subpixel PGn-1m through the data line DGm. Therefore, the green data signal is stored in the storage capacitor without being affected by the parasitic capacitance of the data line DGm.

Next, when a low level red demultiplexer control signal DMR is applied to the demultiplexer 510, a transistor MRm connected to a data line DRm for applying a data signal to the red subpixels PR1m to PRnm. Is turned on. Accordingly, the red data signal is transmitted from the data driving circuit to the storage capacitor of the activated red subpixel PRn-1m through the data line DRm. Therefore, the red data signal is stored in the storage capacitor without being affected by the parasitic capacitance of the data line DRm.

Lastly, when the low level blue demultiplexer control signal DMB is applied to the demultiplexer 510, the transistor MBm connected to the data line DBm for applying the data signal to the blue subpixels PB1m to PBnm is applied. Is turned on. Therefore, the blue data signal is transmitted from the data driving circuit to the storage capacitor of the activated blue subpixel PBn-1m through the data line DBm. Therefore, the blue data signal is stored in the storage capacitor without being affected by the parasitic capacitance of the data line DBm.

As described above, the green, red, and blue demultiplexer control signals DMG, DMR, and DMB are sequentially applied while the low level n−1 th scan signal is supplied, so that the corresponding pixel Pn−1m is applied. The predetermined color is displayed.

The green, red and blue demultiplexer control signals (DMG, DMR, DMB) have different duty depending on the luminous efficiency. That is, the demultiplexer control signal DMB of the transistor MBm connected to the data line DBm of the color having low luminous efficiency has a smaller duty. This may vary depending on the phosphorescence or fluorescence of the organic EL device.

The scan driver 200 supplies scan signals having a duty shorter than one horizontal period, and the scan signal is not supplied for a time corresponding to the difference between the one horizontal period and each scan period. Therefore, a blanking period exists for a predetermined time between the n-th scan signal and the n-th scan signal, and the data lines DR1 to DBm are precharged during the blanking period. Therefore, the data lines DR1 to DBm are precharged while the scan signal is not supplied, so that the precharge voltage Vpc does not affect the light emission of the pixels P11 to Pnm.

When the n−1 th scan signal changes to the high level, the demultiplexer controller 700 supplies the precharge control signal pc to the precharge unit 600.

The precharge control signal pc simultaneously turns on the plurality of transistors P1 to Pm connected to the data lines DR1 to DBm, and the plurality of transistors P1 to Pm respectively set the precharge voltage Vpc. Is supplied to the data lines DR1 to DBm. The precharge voltage Vpc may be an intermediate level of the data voltages supplied to the data lines DR1 to DBm. When the supplied data voltage is 10V to 0V, the precharge voltage Vpc is about 5V. .

Therefore, the data lines DR1 to DBm are precharged to a voltage value of an intermediate level. In the case of the organic light emitting display device using the demultiplexer 510, the data supply period is short, so that the data lines DR1 to DBm emit light when the data lines DR1 to DBm are not sufficiently charged or discharged. In this case, there is a problem that an image of a desired brightness is not realized. In this case, when precharging each of the data lines DR1 to DBm to an intermediate level, even when the data signal is supplied for a short time, the charging / discharging time is shortened so that a specific data signal can be supplied to each data line.

The precharge period, that is, the blanking period between the scan signals, is maintained for a much shorter time than the period for supplying the data signal to each of the data lines DR1 to DBm.

When the nth scan signal of the low level is supplied from the scan driver 200, the pixels Pn1 to Pnm positioned in the nth row are activated. In this case, the transistors P1 to Pm of the precharge unit 600 are turned off to not transmit the precharge voltage Vpc to the data lines DR1 to DBm.

While the low level nth scan signal is applied, the demultiplexer control signals DMG, DMR, and DMB are supplied to the demultiplexer 510 in the order of colors having high luminous efficiency from the demultiplexer controller 700.

When the low level green demultiplexer control signal DMG is applied to the demultiplexer 510, the transistor MGm connected to the data line DGm for applying a data signal to the green subpixels PG1m to PGnm is turned on. . Therefore, the data signal of the green is supplied from the data driving circuit to the storage capacitor of the activated green subpixel PGnm.

Next, when a low level red demultiplexer control signal DMR is applied to the demultiplexer 510, a transistor MRm connected to a data line DRm for applying a data signal to the red subpixels PR1m to PRnm. Is turned on. Therefore, the red data signal is supplied from the data driving circuit to the storage capacitor of the activated red subpixel PRnm.

Lastly, when the low level blue demultiplexer control signal DMB is applied to the demultiplexer 510, the transistor MBm connected to the data line DBm for applying the data signal to the blue subpixels PB1m to PBnm is applied. Is turned on. Therefore, the blue data signal is supplied from the data driving circuit to the storage capacitor of the activated blue subpixel PBnm.

The green, red, and blue data signals are transmitted to the pixel portion through the precharged data lines DRm, DGm, and DBm, and thus driving can be performed for a short time. Accordingly, in the pixel Pnm, each of the subpixels PRnm, PGnm, and PBnm emits light corresponding to the data signal to display a specific color.

4 is a characteristic diagram of a data voltage according to an embodiment of the present invention.

Referring to FIG. 4, the voltage Vdata of the data signal stored in the red, green, and blue subpixels according to the driving order of the demultiplexer will be described. In FIG. 4, the x-axis is regarded as the supply time of the demultiplexer control signals DMG, DMR, and DMB, and the y-axis is regarded as the voltage Vdata of the data signal stored in each of the subpixels PGnm, PRnm, and PBnm. At this time, 0 to t1 indicated on the x-axis indicate the turn-on time of the green transistor MGm of the demultiplexer 510, t1 to t2 the turn-on time of the red transistor MRm, and t2 to t3 the turn-on time of the blue transistor MBm, respectively. Indicates.

When the same V1 data voltage is supplied to the red, green, and blue subpixels (PRnm, PGnm, PBnm), the green subpixel (PGnm) having the best luminous efficiency continues from the green data line (DBm) for one horizontal period. It receives a charge and charges a charge almost equal to V1. Therefore, the organic EL device of the green subpixel PGnm emits light by receiving the correct driving current ID close to 0 in Equation 1 below.

In this case, ΔV is the difference voltage between the actual voltage stored in the storage capacitor and the applied data voltage Vdata, and Vth is a threshold voltage of the driving transistor.

The red subpixel PRnm, which has a lower luminous efficiency than the green subpixel PGnm, receives a charge corresponding to V1 from the data line DRm for a time minus t1 in the first horizontal period. Therefore, the storage capacitor of the red subpixel (PRnm) does not charge to V1 but charges a charge of V2 lower than V1. The organic EL device of the red subpixel PRnm is supplied with a driving current ID having a negative ΔV in Equation 1 above. Therefore, the organic EL device of the red subpixel (PRnm) is supplied with a larger amount of driving current (ID) than the supplied data voltage (Vdata) to compensate for the low luminous efficiency.

The blue subpixel PBnm, which has a lower luminous efficiency than the red subpixel PRnm, receives a charge corresponding to V1 from the data line DBm for a time minus t2 in the first horizontal period. Therefore, the storage capacitor of the blue subpixel (PBnm) does not charge to V1 but charges a charge of V3 lower than V1. The organic EL device of the blue subpixel PBnm supplies the driving current ID having a negative ΔV of an absolute value greater than the absolute value of ΔV of the red subpixel PBnm in Equation 1 above. Receive. The organic EL device of the blue subpixel (PBnm) is supplied with a larger amount of driving current (ID) than the supplied data voltage to compensate for very low luminous efficiency.

According to the present invention as described above, in the organic light emitting display device including the demultiplexer, the value of the driving current is adjusted by varying the time for charging the storage capacitor of the subpixel according to the luminous efficiency of each color subpixel. . Therefore, it is possible to prevent the emission of light of low luminance according to the light emitting efficiency of the subpixels.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (13)

A driving method of an organic light emitting display device comprising a demultiplexer for supplying a data signal to red, green and blue data lines and a precharge unit for precharging the data lines. Precharging the data lines by receiving a precharge voltage from the precharge unit during a blanking period between a previous scan section and a current scan section following the previous scan section; And And supplying data signals from the demultiplexer in order of high luminous efficiency during the current scanning period. The method of claim 1, wherein precharging the plurality of data lines comprises: Simultaneously turning on the transistors of the precharge unit; And And applying a precharge voltage to the data lines through transistors of the turned on precharge unit. The method of claim 2, wherein supplying the data signals to the data lines comprises: Turning off the transistors of the precharge unit; And turning on the transistors connected to the data lines in a color order of high luminous efficiency among the transistors of the demultiplexer and supplying a data signal to the sub-pixels according to the luminous efficiency. 4. The method of claim 3, wherein the luminous efficiency is lowered in the order of green, red, and blue. The method of claim 4, wherein the turn-on time of the transistors of the demultiplexer is shortened in the order of green, red, and blue. The method of claim 5, wherein the precharge voltage is a voltage of an intermediate level of the plurality of data signals. A pixel unit including red, green, and blue subpixels, and configured to display a predetermined image; A scan driver for supplying a scan signal to the pixel portion; A data driver for supplying data signals to the pixel portion in order of color having high luminous efficiency; A precharge unit for precharging the data lines which transfer the data signal to the pixels; And And a demultiplexer unit which receives two or more data signals from the data driver and transfers the two or more data signals to the subpixels in the order of colors having high luminous efficiency. The organic light emitting display device of claim 7, wherein the precharge unit comprises a plurality of transistors that are simultaneously turned on to supply a precharge voltage to each data line. The organic light emitting display device of claim 8, wherein the precharge voltage is a voltage of an intermediate level of the plurality of data signals. 10. The organic light emitting display device of claim 9, wherein the demultiplexer comprises a plurality of transistors which are turned on in order of high luminous efficiency to supply the data signal to the data line. The organic light emitting display device of claim 10, wherein the luminous efficiency is lowered in the order of green, red, and blue. 12. The organic light emitting display device according to claim 11, wherein the transistors of the demultiplexer and the transistors of the precharge unit are MOSFETs of the same conductivity type. The organic light emitting display device of claim 12, wherein the pixel unit, the demultiplexer, and the precharge unit are formed on the same substrate.

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