KR20100072657A - Organic electroluminescent display device and method of driving the same - Google Patents

Abstract

PURPOSE: An organic electroluminescence device and a driving method there are provided to emit the light of a desired brightness regardless of shift of the threshold voltage by reflecting the threshold voltage to the voltage applied in a gate electrode of a driving transistor. CONSTITUTION: A gate wiring intersects with a data line. A switching transistor is connected to n-th gate wiring and data line. A driving transistor supplies the current to the organic electroluminescent diode(OLED). A first capacitor(C1) is connected to a gap between a drain electrode of the switching transistor and a gate electrode of the driving transistor. A first sampling transistor samples the threshold voltage of the organic electroluminescent diode at a first node.

Description

Organic electroluminescent display device and method of driving the same {Organic electroluminescent display device and method of driving the same}

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

As the information society develops, the demand for display devices for displaying images is increasing in various forms. Recently, liquid crystal displays (LCDs), plasma display panels (PDPs), organic fields Various flat display devices such as organic light emitting diodes (OLEDs) are being utilized.

Among these flat panel display devices, the organic light emitting display device can be driven at low voltage, has a thin shape, is excellent in viewing angle, and has a fast response speed.

As the organic light emitting display device, an active matrix type organic light emitting display device in which a plurality of pixels are positioned in a matrix form and displays an image is widely used.

1 is an equivalent circuit diagram of a pixel of a general organic light emitting display device.

As shown in the figure, the organic light emitting diode has a gate wiring GL and a data wiring DL which cross each other to define the pixel P. As shown in FIG.

Each pixel P includes a switching transistor T1, a driving transistor T2, and an organic light emitting diode OLED. The gate electrode and the source electrode of the switching transistor T1 are connected to the gate wiring and the data wiring GL and DL, respectively.

The gate electrode of the driving transistor T2 is connected to the drain electrode of the switching transistor T1. The source electrode of the driving transistor T2 is connected to the power supply voltage line VDDL, and the drain electrode is connected to the first electrode of the organic light emitting diode OLED, that is, an anode.

The second electrode of the organic light emitting diode OLED, that is, the cathode, is connected to the ground terminal GND.

On the other hand, the storage capacitor C is located between the gate electrode and the source electrode of the driving transistor T2.

As the switching transistors and the driving transistors T1 and T2, a P type transistor can be used.

In the organic light emitting diode having the above configuration, when the negative gate voltage is scanned and applied through the gate wiring GL, the switching transistor T1 is turned on. Accordingly, the data voltage Vdata passes through the switching transistor T1 and is applied to the gate electrode of the driving transistor T2. Accordingly, the current I _OLED is supplied to the organic light emitting diode OLED through the driving transistor T2. As a result, the organic light emitting diode OLED emits light to display an image.

Meanwhile, the storage capacitor C stores the data voltage Vdata applied to the driving transistor T2 until the next frame is scanned.

The current I _OLED supplied to the organic light emitting diode OLED is controlled by the data voltage Vdata applied to the gate electrode of the driving transistor T2.

For example, the current I _OLED supplied to the organic light emitting diode OLED is obtained through Equation 1 as follows.

(수식1)

(Formula 1)

Here, Vgs is a voltage difference between the gate electrode and the source electrode of the driving transistor T2, Vth is a threshold voltage of the driving transistor T2, and k is a constant value.

However, in the organic light emitting display device, a deviation of the threshold voltage Vth of the driving transistor T2 occurs between a plurality of pixels due to the characteristics of the manufacturing process. As a result, the current supplied to the organic light emitting diode OLED has a different value from the desired value, thereby causing a problem that the luminance of the emitted light is different from the desired value.

In order to solve such a problem, an organic light emitting diode having a voltage compensation method for compensating the threshold voltage Vth of the driving transistor T2 has been proposed. In the voltage compensating organic light emitting diode, the threshold voltage Vth of the driving transistor T2 is sampled and reflected on the gate electrode of the driving transistor T2. Accordingly, the current I _OLED supplied to the organic light emitting diode OLED may be obtained through, for example, Equation 2 as follows.

(수식2)

(Formula 2)

As such, the current I _OLED supplied to the organic light emitting diode OLED does not depend on the threshold voltage Vth of the driving transistor T2, unlike the above formula (1). Accordingly, compensation for the threshold voltage Vth of the driving transistor T2 is performed.

However, although the threshold voltage Vth of the driving transistor T2 is compensated for as described above, the organic light emitting diode OLED is deteriorated and the threshold voltage Vtho of the organic light emitting diode OLED is shifted. In this case, this cannot be corrected. Accordingly, even when a data voltage Vdata for emitting light having a desired brightness is applied, light having a brightness lower than the desired brightness is emitted. Furthermore, since the threshold voltage Vtho of the deteriorated organic light emitting diode OLED cannot be corrected, non-restored afterimage may occur over time, and the organic light emitting diode OLED may have a lifetime. Will have a limit.

On the other hand, in Equation (2), the current I _OLED flowing through the organic light emitting diode OLED depends on the power supply voltage Vdd. However, when the area of the organic light emitting diode is increased and a high luminance is to be realized, a voltage drop of the power supply voltage Vdd may occur for pixels far from the power supply voltage Vdd source. As a result, a difference in luminance occurs between the pixels.

As described above, conventionally, since the correction of the threshold voltage and compensation for the power supply voltage of the organic light emitting diode are not performed, the organic light emitting diode cannot emit light having a desired luminance. As a result, a problem of deterioration of image quality occurs.

The present invention has a problem to provide an organic electroluminescent device and a driving method thereof capable of improving image quality.

In order to achieve the above-described problems, the present invention, the data wiring; An n-th, n-th, and n-th gate wiring line which intersects the data wiring line and is sequentially arranged; A switching transistor connected to the nth gate line and a data line; A driving transistor supplying a current to the organic light emitting diode and connected to a power supply voltage line at a source electrode; A first capacitor connected between the drain electrode of the switching transistor and the gate electrode of the driving transistor; A first sampling transistor connected between the first node to which the switching transistor and the first capacitor are connected, and the organic light emitting diode to sample the threshold voltage of the organic light emitting diode at the first node; A second sampling transistor connected between a second node connected to the driving transistor and the first capacitor and a drain electrode of the driving transistor, the second sampling transistor sampling a power supply voltage and a threshold voltage of the driving transistor at the second node; A light emission control transistor connected to an nth light emission control line and connected between the organic light emitting diode and a drain electrode of the driving transistor to control a current supplied to the organic light emitting diode; An organic light emitting display device includes a second capacitor connected between any one of the first and second nodes and the power supply voltage line.

The first and second sampling transistors may be connected to the n−1 th gate wiring.

The other electrode of the second capacitor is connected to the first node, and a turn-on voltage is applied to the n-th light emitting control line during the first first section of the section where the turn-on voltage is applied to the n-th gate wiring. And a turn-off voltage to the n-th light emission control line during a second half of the section where the turn-on voltage is applied to the n-th gate wiring and a third section during which a turn-on voltage is applied to the n-th gate wiring. Is applied, and a turn-on voltage may be applied to the nth emission control wiring after the third period.

A first initialization transistor connected to the n-th-th gate line and applying an initialization voltage to the first node; 2 may further include an initialization transistor.

The other electrode of the second capacitor is connected to the second node, a first section in which a turn-on voltage is applied to the n-second gate wiring, and a turn-on voltage is applied to the n-th gate wiring. A turn-off voltage may be applied to the nth light emitting control wiring during the second section, and a turn-on voltage may be applied to the nth light emitting control wiring after the second section.

In another aspect, the present invention provides a power supply circuit including: a first node connected to a first transistor and a switching transistor connected to an nth gate wiring and a data wiring among n-th, n-1, and n-th gate wirings; Initializing a driving transistor connected to the second node connected to the first capacitor; After initializing the first and second nodes, the first sampling transistor is turned on to sample the threshold voltage of the organic light emitting diode at the first node, and the second sampling transistor is turned on to supply power to the second node. Sampling a threshold voltage of the driving transistor; After sampling the threshold voltage of the organic light emitting diode and the threshold voltage of the driving transistor, applying a data voltage to the first node to form a current passing through the driving transistor; And turning on a light emitting control transistor connected to an nth light emitting control wiring to supply a current passing through the driving transistor to the organic light emitting diode.

The first and second sampling transistors may be connected to the n−1 th gate wiring.

The initializing of the first and second nodes may include applying a turn-on voltage to the n-th light emitting control line during the first first period of the section where the turn-on voltage is applied to the n-th gate wiring. And electrically connecting two nodes to the organic light emitting diode, and sampling the threshold voltage of the organic light emitting diode and the threshold voltage of the driving transistor comprises turning on the n-th gate wiring. A turn-off voltage is applied to the nth light emitting control wiring during the second half of the period in which the voltage is applied, thereby electrically connecting the second node to the organic light emitting diode and connecting the second node of the driving transistor. It may comprise the step of electrically connecting to the drain electrode.

The initializing of the first and second nodes may include turning on first and second initialization transistors connected to the n-th-th gate line during a first period in which a turn-on voltage is applied to the n-th-th gate line. And applying an initialization voltage to the first and second nodes through the first and second initialization transistors, respectively, and sampling the threshold voltage of the organic light emitting diode and the threshold voltage of the driving transistor. A turn-off voltage is applied to the n-th light emission control line during the second period during which the turn-on voltage is applied to the n-th gate wiring, thereby electrically connecting the first node to the organic light emitting diode and And electrically connecting two nodes to the drain electrode of the driving transistor.

The method may further include storing the data voltage component using a second capacitor connected to the power supply voltage line.

In the organic light emitting device according to the present invention, the threshold voltage of the organic light emitting diode is reflected in the voltage applied to the gate electrode of the driving transistor, so that light having a desired luminance is irrespective of the shift of the threshold voltage of the organic light emitting diode. It will emit light. As such, since the shift of the threshold voltage of the organic light emitting diode can be corrected, it is possible to improve the problem of non-restored afterimages occurring over time and to improve the life of the organic light emitting diode. do.

On the other hand, even if a variation in the threshold voltage of the organic light emitting diode is generated among the plurality of pixels due to the characteristics of the manufacturing process of the organic light emitting diode, a current is generated to correct the variation of the threshold voltage. Therefore, regardless of the change in the threshold voltage, light having a desired luminance can be emitted.

In addition, the power supply voltage and the threshold voltage of the driving transistor are also sampled and reflected in the voltage applied to the gate electrode of the driving transistor. Accordingly, since the current does not depend on the change of the power supply voltage and the threshold voltage of the driving transistor, it is possible to compensate for the power supply voltage and the threshold voltage of the driving transistor.

Furthermore, before the corresponding pixel is selected and the data voltage is applied to both ends of the capacitor connected between the switching transistor and the driving transistor, a separate initialization voltage is applied and initialization is performed. As such, since the initialization can be stably performed at an early stage, it is possible to effectively suppress the slowdown of the screen and the reduction of the contrast ratio (C / R).

Hereinafter, with reference to the drawings will be described embodiments of the present invention.

2 is a view schematically showing an organic light emitting display device according to an embodiment of the present invention, FIG. 3 is an equivalent circuit diagram of a pixel of an organic light emitting display device according to an embodiment of the present invention, and FIG. The waveform diagram of the voltage supplied to the gate wiring and the data wiring of the organic light emitting diode according to the embodiment.

As shown, the organic light emitting display device 100 according to the embodiment of the present invention includes a display unit 200 and a driving unit.

In the display unit 100, a plurality of gate lines GL to GLn extend in a first direction, for example, a row direction. A plurality of data lines DL1 to DLm extend in a second direction intersecting the first direction, for example, a column direction. As described above, the plurality of gate lines GL to GLn and the plurality of data lines DL1 to DLm that cross each other define a plurality of pixels P arranged in a matrix form. On the other hand, a plurality of light emitting control wirings EL1 to ELn extending in the first direction are disposed corresponding to the plurality of gate wirings. In addition, the first and second auxiliary gate lines AGL1 and AGL2 are disposed on the previous row line and the previous row line of the first gate line GL1. These first and second auxiliary gate lines AGL1 and AGL2 serve as pre-electric gate wiring and previous gate wiring with respect to the pixels P connected to the first gate wiring GL1.

Referring to FIG. 4, each pixel P of the display unit 100 includes a plurality of transistors, for example, first to seventh transistors T1 to T7, first and second capacitors C1 and C2, and an organic light source. Electroluminescent diodes (OLEDs) can be constructed. In the embodiment of the present invention, the P type transistor is used as the first to seventh transistors T1 to T7 as an example. On the other hand, it is apparent to those skilled in the art that an N type transistor can be used as the first to seventh transistors T1 to T7. Furthermore, it will be apparent to those skilled in the art that some of the first to seventh transistors T1 to T7 can use P type transistors, and the rest can use N type transistors.

The driving unit may include an interface 310, a timing controller 320, a power generator 330, a gate driver 340, a data driver 350, and a gamma voltage generator 360. .

The interface 310 includes a data signal RGB, a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a clock signal DCLK, a data enable signal DE, and the like from an external system such as a video card. The control signal TCS is received and transmitted to the timing controller 320.

The timing controller 320 samples the control signal SCS for controlling the data driver 350 and the data signal RGB supplied from the interface 310 in accordance with the control signal SCS, thereby controlling these control signals SCS. And a data signal RGB to the data driver 350. In addition, the timing controller 320 supplies a control signal GCS for controlling the gate driver 340 to the gate driver 340.

The gamma voltage generator 360 divides the high potential common voltage and the low potential common voltage generated from the power generator 330 to generate a gamma voltage Vgamma corresponding to each gray level of the data signal RGB. Supply to the data driver 350.

The power generator 330 supplies the driving voltages for driving the components of the driver. In addition, the power supply voltage Vdd and the initialization voltage Vref are generated.

The gate driver 340 sequentially scans the first and second auxiliary gate lines AGL1 and AGL2 and the plurality of gate lines GL1 to GLn in response to the control signal GCS supplied from the timing controller 320. do. During each scan period, a turn-on voltage in the form of a pulse is supplied to the gate wirings GL1 to GLn. On the other hand, the turn-off voltage is continuously supplied to the gate lines GL1 to GLn until the scan period of the next frame.

On the other hand, the gate driver 340 sequentially scans the plurality of light emitting control wirings EL1 to ELn, and supplies a turn-off voltage in the form of a pulse to each of the light emitting control wirings EL1 to ELn during each non-light emitting period. On the other hand, during each light emitting period, the turn-on voltage is continuously supplied to each of the light emission control wirings EL1 to ELn.

Here, the polarity (or level) of the turn-on / turn-off voltage output by the gate driver 340 is determined according to the type of the transistor connected to the gate wiring and the emission control wiring.

The data driver 350 supplies the data signal RGB to the plurality of data wires DL1 to DLm in response to the control signal SCS supplied from the timing controller 320. That is, the data voltage Vdata corresponding to the data signal RGB value is generated using the gamma voltage Vgamma, and the generated data voltage Vdata is output to the data wirings DL1 to DLm.

Hereinafter, the structure of the pixel on the display unit 100 will be described in more detail with reference to FIG. 4. In FIG. 4, one pixel and a data line DL are illustrated for convenience of description, and the data line DL of FIG. 4 is disposed on any one of the first to nth data lines DL1 to DLn of FIG. 3. Yes.

The first transistor T1 may function as the switching transistor T1. The gate electrode of the first transistor T1 configured in the pixel P of the nth row line may be connected to the nth gate line GLn. The source electrode may be connected to the data line DL. The drain electrode of the first transistor T1 may be connected to the first electrode of the first capacitor C1. Here, the contact point of the first transistor T1 and the first capacitor C1 is referred to as a first node N1.

The second transistor T2 may function as the driving transistor T2. The source electrode of the second transistor T2 may be connected to the power supply voltage line VDDL. The drain electrode may be connected to the drain electrode of the fourth transistor T3 and the source electrode of the fifth transistor T5. The gate electrode may be connected to the second electrode of the first capacitor C1 and the first electrode of the second capacitor C2. Here, the contact point of the second transistor T2 and the first capacitor C1 is referred to as a second node N2.

The third transistor T3 may function as the first sampling transistor T3. The gate electrode of the third transistor T3 may be connected to the previous gate line GLn-1, that is, the n-th-th gate line GLn-1. The source electrode may be connected to the first node N1. Meanwhile, the drain electrode may be connected to a first electrode of the organic light emitting diode OLED, for example, an anode.

The fourth transistor T4 can function as the second sampling transistor T4. The gate electrode of the fourth transistor T4 may be connected to the previous gate line GLn-1, that is, the n-th-th gate line GLn-1. The source electrode may be connected to the second node N2. The drain electrode may be connected to the drain electrode of the second transistor T2.

The fifth transistor T5 can function as the light emission control transistor T5. The gate electrode of the fifth transistor T5 may be connected to the nth emission control wiring ELn. The source electrode may be connected to the drain electrode of the second transistor T2. Meanwhile, the drain electrode may be connected to an anode of the organic light emitting diode OLED.

The sixth transistor T6 may function as the first initialization transistor T6. The gate electrode of the sixth transistor T6 may be connected to the pre-electrode gate line GLn-2, that is, the n-2nd gate line GLn-2. The source electrode may be connected to the initialization wiring VREFL. The drain electrode may be connected to the first node N1.

The seventh transistor T7 may function as the second initialization transistor T7. The gate electrode of the seventh transistor T7 may be connected to the pre-electric gate line GLn-2, that is, the n-th-2nd gate line GLn-2. The source electrode may be connected to the initialization wiring VREFL. The drain electrode may be connected to the second node N2.

The first capacitor C1 may function as a boost capacitor C2. The first electrode of the first capacitor C1 may be connected to the first node N1, and the second electrode may be connected to the second node N2.

The second capacitor C2 may function as the storage capacitor C2. The first electrode of the second capacitor C2 may be connected to the gate electrode of the second transistor T2, and the second electrode may be connected to the power supply voltage line VDDL. Meanwhile, the first electrode of the second capacitor C2 may be connected to the first node N1.

As described above, the first to seventh transistors T1 to T7, the first and second capacitors C1 and C2, and the organic light emitting diode OLED are connected to each other and input to the pixel P. It operates through a number of signals and emits light.

Hereinafter, the function of the components as described above will be described in detail.

The first transistor T1 is turned on when the corresponding (or present) gate wiring, for example, the n-th gate wiring GLn is selected and a turn-on voltage is applied, so that the data voltage Vdata is applied to the first transistor T1. Will pass. When the first transistor T1 is P type, a low level voltage or a negative polarity voltage may be used as the turn on voltage.

The second transistor T2 adjusts the amount of current I _OLED passing through the second transistor T2 according to the level of the voltage applied to the gate electrode.

The third transistor T3 is turned on when the turn-on voltage is applied to the previous gate line, for example, the n-th gate line GLn-1, to sample the threshold voltage Vtho of the organic light emitting diode OLED. Done. The threshold voltage Vtho sampled in this way is reflected in the first node N1. When the third transistor T3 is P type, a low level voltage or a negative polarity voltage may be used as the turn on voltage.

The fourth transistor T4 is turned on when the turn-on voltage is applied to the previous gate wiring, for example, the n-th gate wiring GLn-1, so as to sample the threshold voltage Vth of the second transistor T2. do. The threshold voltage Vth sampled in this way is reflected in the second node N1. When the fourth transistor T4 is P type, a low level voltage or a negative polarity voltage may be used as the turn on voltage.

The fifth transistor T5 is turned on when the turn-on voltage is applied to the corresponding light emission control wiring, for example, the nth light emission control wiring ELn, so that the current I _OLED passing through the second transistor T2 is fifth. Passes through transistor T5. When the fifth transistor T5 is P type, a low level voltage or a negative polarity voltage may be used as the turn on voltage.

The sixth transistor T6 is turned on when the turn-on voltage is applied to the all-electric gate wiring, for example, the n-th-th gate wiring GLn-2, and passes the initialization voltage Vref. The initialization voltage Vref is reflected in the first node N1. When the sixth transistor T6 is P type, a low level voltage or a negative polarity voltage may be used as the turn on voltage.

The seventh transistor T7 is turned on when the turn-on voltage is applied to the pre-electric gate wiring, for example, the n-th-th gate wiring GLn-2, and passes the initialization voltage Vref. The initialization voltage Vref is reflected in the second node N2. When the seventh transistor T7 is P type, a low level voltage or a negative polarity voltage may be used as the turn on voltage.

The second capacitor C2 stores the voltage applied to the gate electrode of the second transistor T2, that is, the second node N2. Accordingly, the data voltage Vdata component input to the pixel P when the current frame is scanned is stored in the second capacitor C2 until the pixel P is scanned the next frame. Accordingly, the current I _OLED may flow in the organic light emitting diode OLED according to the data voltage Vdata applied in the current frame until the next frame is scanned or initialized.

The first capacitor C1 couples the first electrode of the first capacitor C1, that is, the voltage change amount ΔV at the first node N1 to couple the second electrode of the first capacitor C1. That is, it is reflected to the second node N2. In other words, when a voltage change occurs in the first node N1, the voltage change amount ΔV is coupled by the first capacitor C1, and eventually ΔV is reflected in the second node N2. do. As such, the first capacitor C1 couples the voltage change amount ΔV of the first node N1 to the second node N2 to boost the voltage of the second node N2. .

When the fifth transistor T5 is turned on, the organic light emitting diode OLED receives the current I _OELD generated according to the data voltage Vdata, thereby emitting light.

Hereinafter, referring to FIGS. 3 and 4, a method of driving an organic light emitting display device according to an exemplary embodiment of the present invention will be described in detail.

First, when the pre-electric gate line, for example, the n-second gate line GLn-2 is selected and the turn-on voltage is applied during the first period t1, the sixth and seventh transistors T6 and T7 are turned on. . Accordingly, the initialization voltage Vref is applied to the first and second nodes N1 and N2 so that the first capacitor C1 is initialized (V1 = V2 = Vref). That is, the pixel P is initialized by the initialization voltage Vref. As such, the first period t1 is a scan period in which the pre-electric gate line is scanned, and corresponds to an initialization period. The initialization voltage Vref may have a voltage range from the power supply voltage Vdd to a negative voltage.

Next, when the previous gate line, for example, the n-th gate line GLn-1 is selected and the turn-on voltage is applied during the second period t2, the third and fourth transistors T3 and T4 turn on. do. Accordingly, the threshold voltage Vth and the power supply voltage Vdd of the second transistor T2, that is, the driving transistor T2, are sampled at the second node N2 through the turned-on fourth transistor T4. As a result, the second node N2 has a voltage of V2 = Vdd-Vth. Meanwhile, the threshold voltage Vtho component of the organic light emitting diode OLED is sampled at the first node N1 through the turned-on third transistor T3, and as a result, the first node N1 is configured to have V1 = Vtho. Will have voltage. As such, the second period t2 is a scan period in which the previous gate line is scanned, and corresponds to a sampling period.

Next, when the corresponding (or present) gate line, for example, the n-th gate line GLn, is selected and the turn-on voltage is applied during the third period t3, the first transistor T1 is turned on. Accordingly, the data voltage Vdata transferred through the data wiring DL is applied to the first node N1 (V1 = Vdata). Meanwhile, as the first capacitor C1 is coupled to the second node N2 as much as the voltage change amount (that is, ΔV = Vdata−Vtho) at the first node N1, the second node N2 is applied. Has a voltage of V2 = Vdd-Vth + ΔV = Vdd-Vth + (Vdata-Vtho). As such, the third section t3 is a scan section in which the corresponding gate line is scanned, and corresponds to a data programming section in which the corresponding data voltage is applied.

Here, the polarity of the applied data voltage Vdata may be determined according to the type of the second transistor T2. For example, in the case where the second transistor T2 is configured as a P type, the data voltage Vdata has a negative polarity.

As such, the second node voltage (V2), i.e. the second transistor, by a voltage (V2) applied to the gate electrode of (T2) the second transistor (T2) applied to the (N2) is turned on current (I _OLED) Will be generated. The current I _OLED passing through the second transistor T2 may be obtained through Equation 3 below.

(Formula 3)

Here, Vgs is a voltage difference between the gate electrode and the source electrode of the second transistor T2, and k is a constant value.

On the other hand, the turn-off voltage may be applied to the corresponding (or present) light emission control wiring ELn from before the start time of the first section t1 to the end time of the second section t2. As described above, during the period in which the turn-off voltage is applied to the emission control wiring EL, the third transistor T3 is turned off so that the current I _OLED does not flow through the organic light emitting diode OLED. After that, the turn-on voltage is applied to the light emission control wiring EL from the third section t3. Accordingly, the fifth transistor T5 is turned on and the current I _OLED generated in the second transistor T2 is supplied to the organic light emitting diode OLED through the fifth transistor T5. As a result, the organic light emitting diode OLED emits light having luminance corresponding to the current I _OLED value.

Meanwhile, the second capacitor C2 stores the voltage of the second node N2, V1 = Vdd-Vth + (Vdata-Vtho), until the second node N2 is initialized in the next frame. The fifth transistor T5 passes the current I _OLED until the turn-off voltage is applied in the next frame. Accordingly, the second transistor T2 generates the current I _OLED according to the data voltage Vdata of the current frame during the storage period until the second node N2 is initialized in the next frame, and the organic light emitting diode The OLED emits light having luminance according to the data voltage Vdata of the current frame during the light emitting period until the turn-off voltage is applied to the fifth transistor T5 in the next frame.

Through the operation as described above, it is possible to drive the organic light emitting device according to the embodiment of the present invention.

Referring to Equation 3, the current I _OLED supplied to the organic light emitting diode OLED depends on the data voltage Vdata and the threshold voltage Vtho of the organic light emitting diode OLED. Accordingly, even if the organic light emitting diode OLED is deteriorated and the threshold voltage Vtho is shifted and increased, the threshold voltage Vtho is included in Equation 3, so that the current is changed according to the shift of the threshold voltage Vtho. (I _OLED ) becomes high. As such, the increased current corrects the shift of the threshold voltage Vtho, thereby correcting the decrease in luminance of the emitted light according to the shift of the threshold voltage Vhto, so that the light having the desired luminance is emitted. In other words, referring to Equations 1 and 2, the threshold voltage Vtho does not affect the generation of the current I _OLED , and thus, when the threshold voltage Vtho is shifted, it is lower than the desired luminance. Luminance light is emitted. In contrast, in the embodiment of the present invention, the threshold voltage Vtho is reflected in the voltage applied to the gate electrode of the second transistor T2, so that the shift of the threshold voltage Vtho is reduced even if the threshold voltage Vtho is shifted. Higher current I _OLED is generated to calibrate. Therefore, regardless of the shift of the threshold voltage Vtho, light having a desired luminance is emitted through the organic light emitting diode OLED. As described above, in the embodiment of the present invention, since the shift of the threshold voltage Vtho can be corrected, the problem of non-restored afterimage occurring in the past can be improved, and the organic light emitting diode ( OLED's lifetime can be improved.

On the other hand, even if a variation of the threshold voltage Vtho of the organic light emitting diode OLED is generated among the plurality of pixels due to the characteristics of the manufacturing process of the organic light emitting diode, the current ( I _OLED ) is generated. Therefore, regardless of the change in the threshold voltage Vtho, light having a desired luminance can be emitted through the organic light emitting diode OLED.

In addition, the power supply voltage Vdd and the threshold voltage Vth of the second transistor T2 are also sampled and reflected in the voltage applied to the gate electrode of the second transistor T2. Accordingly, the power supply voltage Vdd and the threshold voltage Vth of the second transistor T2 are not included in Equation 3. That is, since the current I _OLED does not depend on the change of the power supply voltage Vdd and the threshold voltage Vth of the second transistor T2, the threshold voltage of the power supply voltage Vdd and the second transistor T2 ( Vth) can be compensated.

Furthermore, before the corresponding pixel is selected and the data voltage Vdata is applied to the first and second nodes N1 and N2, a separate initialization voltage Vref is applied to perform initialization. As such, since the initialization can be stably performed at an early stage, it is possible to effectively suppress the slowdown of the screen and reduction of the contrast ratio (C / R).

FIG. 5 is a view illustrating a process in which a threshold voltage is sampled when the threshold voltage of the organic light emitting diode is shifted in the organic light emitting diode according to the embodiment of the present invention to correct the shift of the threshold voltage. In FIG. 5, the left graph is a current-voltage (I-V) graph of the organic light emitting diode, and shows how the threshold voltage Vtho is shifted with deterioration. The right graph is a voltage-time (V-T) graph, which shows waveforms of the voltage of the second node V2 and the voltage Va of the anode of the organic light emitting diode over time.

The graph on the left shows a case where the threshold voltage Vtho of the organic light emitting diode (OLED in FIG. 3) shifts. As the threshold voltage Vtho is shifted as described above, the voltage Va at the anode is shifted in the second section t2, that is, the turn-on voltage is applied to the previous gate line GLn-1 of FIG. 3. Able to know. Accordingly, in the second period t2, the shifted threshold voltage Vtho is sampled through the third transistor (T3 of FIG. 3) and applied to the first node (N1 of FIG. 3). On the other hand, since the shifted threshold voltage Vtho is not reflected to the second node (N2 in FIG. 3) during this period t2, the voltage V2 of the second node is substantially the same before and after the shift. It can be seen.

As a result, the shifted threshold voltage Vtho is reflected to the second node (N2 of FIG. 3) by the first capacitor C1 of FIG. 3 in the third section st3. That is, the shifted threshold voltage Vtho is reflected on the gate electrode of the second transistor (T2 of FIG. 3). This can be seen from the fact that the voltage V2 of the second node after the threshold voltage is shifted has a lower value than the voltage V2 of the second node before the threshold voltage Vtho is shifted. In other words, it can be seen that the voltage applied to the gate electrode is lowered due to the increase of the threshold voltage Vtho.

The shifted threshold voltage Vtho determines the current I _OLED supplied to the organic light emitting diode together with the data voltage Vdata.

Therefore, even though the threshold voltage Vtho of the organic light emitting diode is shifted and raised, the voltage applied to the gate electrode is corrected because the threshold voltage Vtho is reflected on the gate electrode of the second transistor. As a result, a higher current I _OLED is generated than before the shift to correct the shift of the threshold voltage Vtho. Therefore, in the organic light emitting diode, light having a desired luminance corresponding to the data voltage Vdata is generated regardless of the shift of the threshold voltage Vtho.

6 is a view schematically showing an organic light emitting display device according to another embodiment of the present invention, FIG. 7 is an equivalent circuit diagram of a pixel of an organic light emitting display device according to another embodiment of the present invention, and FIG. The waveform diagram of the voltage supplied to the gate wiring and the data wiring of the organic light emitting diode according to another embodiment of the present invention.

For convenience of explanation, in other embodiments of the present invention shown in FIGS. 6 and 7, descriptions similar to those of the organic light emitting display devices shown in FIGS. 2 and 3 may be omitted.

As shown, the organic light emitting display device 100 according to another embodiment of the present invention includes a display unit 200 and a driving unit.

In the display unit 100, a plurality of gate lines GL to GLn extend in a first direction, for example, a row direction. A plurality of data lines DL1 to DLm extend in a second direction intersecting the first direction, for example, a column direction. On the other hand, a plurality of light emitting control wirings EL1 to ELn extending in the first direction are disposed corresponding to the plurality of gate wirings. The auxiliary gate line AGL is disposed on the previous low line of the first gate line GL1. The auxiliary gate line AGL may serve as a previous gate line with respect to the pixels P connected to the first gate line GL1.

Referring to FIG. 7, each pixel P of the display unit 100 includes a plurality of transistors, for example, first to fifth transistors T1 to T5, first and second capacitors C1 and C2, and an organic light source. Electroluminescent diodes (OLEDs) can be constructed. As the first to fifth transistors T1 to T5, a P type transistor is used as an example.

The driving unit may include an interface 310, a timing controller 320, a power generator 330, a gate driver 340, a data driver 350, and a gamma voltage generator 360. .

Hereinafter, the structure of the pixel on the display unit 100 will be described in more detail with reference to FIG. 7. In FIG. 7, one pixel and a data line DL are illustrated for convenience of description, and the data line DL of FIG. 7 is disposed on any one of the first to nth data lines DL1 to DLn of FIG. 6. Yes.

The first transistor T1 may function as the switching transistor T1. The gate electrode of the first transistor T1 configured in the pixel P of the nth row line may be connected to the nth gate line GLn. The source electrode may be connected to the data line DL. The drain electrode of the first transistor T1 may be connected to the first electrode of the first capacitor C1. Here, the contact point of the first transistor T1 and the first capacitor C1 is referred to as a first node N1.

The second transistor T2 may function as the driving transistor T2. The source electrode of the second transistor T2 may be connected to the power supply voltage line VDDL. The drain electrode may be connected to the drain electrode of the fourth transistor T3 and the source electrode of the fifth transistor T5. The gate electrode may be connected to the second electrode of the first capacitor C1. Here, the contact point of the second transistor T2 and the first capacitor C1 is referred to as a second node N2.

The third transistor T3 may function as the first sampling transistor T3. The gate electrode of the third transistor T3 may be connected to the previous gate line GLn-1, that is, the n-th-th gate line GLn-1. The source electrode may be connected to the first node N1. Meanwhile, the drain electrode may be connected to a first electrode of the organic light emitting diode OLED, for example, an anode.

The fourth transistor T4 can function as the second sampling transistor T4. The gate electrode of the fourth transistor T4 may be connected to the previous gate line GLn-1, that is, the n-th-th gate line GLn-1. The source electrode may be connected to the second node N2. The drain electrode may be connected to the drain electrode of the second transistor T2.

The fifth transistor T5 can function as the light emission control transistor T5. The gate electrode of the fifth transistor T5 may be connected to the nth emission control wiring ELn. The source electrode may be connected to the drain electrode of the second transistor T2. Meanwhile, the drain electrode may be connected to an anode of the organic light emitting diode OLED.

The first capacitor C1 may function as a boost capacitor C2. The first electrode of the first capacitor C1 may be connected to the first node N1, and the second electrode may be connected to the second node N2.

The second capacitor C2 may function as the storage capacitor C2. The first electrode of the second capacitor C2 may be connected to the first node N1, and the second electrode may be connected to the power supply voltage line VDDL. Meanwhile, the first electrode of the second capacitor C2 may be connected to the second node N2.

As described above, the first to fifth transistors T1 to T5, the first and second capacitors C1 and C2, and the organic light emitting diode OLED are connected to each other and input to the pixel P. It operates through a number of signals and emits light.

Hereinafter, the function of the components as described above will be described in detail.

The first transistor T1 is turned on when the corresponding (or present) gate wiring, for example, the n-th gate wiring GLn is selected and a turn-on voltage is applied, so that the data voltage Vdata is applied to the first transistor T1. Will pass.

The second transistor T2 adjusts the amount of current I _OLED passing through the second transistor T2 according to the level of the voltage applied to the gate electrode.

The third transistor T3 is turned on when the turn-on voltage is applied to the previous gate wiring, for example, the n-th gate wiring GLn-1, and samples the threshold voltage Vtho of the organic light emitting diode OLED. Done. The threshold voltage Vtho sampled in this way is reflected in the first node N1.

The fourth transistor T4 is turned on when the turn-on voltage is applied to the previous gate wiring, for example, the n-th gate wiring GLn-1, so as to sample the threshold voltage Vth of the second transistor T2. do. The threshold voltage Vth sampled in this way is reflected in the second node N1.

The fifth transistor T5 is turned on when the turn-on voltage is applied to the corresponding light emission control wiring, for example, the nth light emission control wiring ELn, so that the current I _OLED passing through the second transistor T2 is fifth. Passes through transistor T5.

The second capacitor C2 stores the voltage applied to the first node N1. Accordingly, the data voltage Vdata component input to the pixel P when the current frame is scanned is stored in the second capacitor C2 until the pixel P is scanned or initialized in the next frame.

The first capacitor C1 couples the first electrode of the first capacitor C1, that is, the voltage change amount ΔV at the first node N1 to couple the second electrode of the first capacitor C1. That is, it is reflected to the second node N2. In other words, when a voltage change occurs in the first node N1, the voltage change amount ΔV is coupled by the first capacitor C1, and eventually ΔV is reflected in the second node N2. do. As such, the first capacitor C1 couples the voltage change amount ΔV of the first node N1 to the second node N2 to boost the voltage of the second node N2. .

When the fifth transistor T5 is turned on, the organic light emitting diode OLED receives the current I _OELD generated according to the data voltage Vdata, thereby emitting light.

Hereinafter, referring to FIGS. 7 and 8, a method of driving an organic light emitting display device according to an exemplary embodiment of the present invention will be described in detail.

First, in the scan section where the previous gate line, for example, the n-th gate line GLn-1 is selected and the turn-on voltage is applied, the corresponding emission control wiring, for example, the nth emission control wiring GLn, As an initial section maintaining the turn-on voltage, during the first section t1, the third to fifth transistors T3 to T5 are turned on. Accordingly, the first and second nodes N1 and N2 are connected to the organic light emitting diode OLED to perform initialization.

Next, the second section t2 after the first section t1, that is, the nth light emission control wiring line, among the scan sections in which the n-th gate line GLn-1 is selected and the turn-on voltage is applied thereto. During the period in which the turn-off voltage is applied to GLn, the fifth transistor T5 is turned off. Accordingly, the threshold voltage Vth and the power supply voltage Vdd of the second transistor T2 are sampled at the second node N2 through the turned-on fourth transistor T4, and as a result, the second node N2 is sampled. ) Has a voltage of V2 = Vdd-Vth. Meanwhile, the threshold voltage Vtho of the organic light emitting diode OLED is sampled at the first node N1 through the turned-on third transistor T3, and as a result, the first node N1 receives a voltage of V1 = Vtho. Will have

Next, when the corresponding gate line, for example, the n-th gate line GLn is selected and the turn-on voltage is applied during the third period t3, the first transistor T1 is turned on. Accordingly, the data voltage Vdata transferred through the data wiring DL is applied to the first node N1 (V1 = Vdata).

Meanwhile, as the first capacitor C1 is coupled to the second node N2 as much as the voltage change amount (that is, ΔV = Vdata−Vtho) at the first node N1, the second node N2 is applied. Has a voltage of V2 = Vdd-Vth + ΔV = Vdd-Vth + (Vdata-Vtho).

As such, the second node voltage (V2), i.e. the second transistor, by a voltage (V2) applied to the gate electrode of (T2) the second transistor (T2) applied to the (N2) is turned on current (I _OLED) Will be generated. The current I _OLED generated in the second transistor T2 can be obtained through Equation 3 in the above embodiment.

Next, when the turn-on voltage is applied to the nth light emission control wiring ELn during the fourth period t4, the fifth transistor T5 is turned on. Accordingly, the current I _OLED generated in the second transistor T2 is supplied to the organic light emitting diode OLED through the fifth transistor T5. As a result, the organic light emitting diode OLED emits light having luminance corresponding to the current I _OLED value. As such, the fourth section t4 corresponds to the light emitting section.

Meanwhile, the second capacitor C2 stores the voltage of the first node N1, V1 = Vdata, until the first node N1 is initialized in the next frame. The fifth transistor T5 passes the current I _OLED until the turn-off voltage is applied in the next frame.

Through the operation as described above, it is possible to drive the organic light emitting display device according to another embodiment of the present invention.

As described above, in another embodiment of the present invention, the threshold voltage Vtho is reflected in the voltage applied to the gate electrode of the second transistor T2, so that the desired luminance is obtained regardless of the shift of the threshold voltage Vtho. Light having the light is emitted through the organic light emitting diode OLED. As described above, in another embodiment of the present invention, since the shift of the threshold voltage Vtho can be corrected, it is possible to solve the problem of non-restored afterimages occurring over time, and the organic light emitting diode It is possible to improve the lifetime of the (OLED).

On the other hand, even if a variation of the threshold voltage Vtho of the organic light emitting diode OLED is generated among the plurality of pixels due to the characteristics of the manufacturing process of the organic light emitting diode, the current ( I _OLED ) is generated. Therefore, regardless of the change in the threshold voltage Vtho, light having a desired luminance can be emitted through the organic light emitting diode OLED.

In addition, the power supply voltage Vdd and the threshold voltage Vth of the second transistor T2 are also sampled and reflected in the voltage applied to the gate electrode of the second transistor T2. Accordingly, the current I _OLED does not depend on the change in the threshold voltage Vth of the power source voltage Vdd and the second transistor T2, and thus the threshold voltage of the power source voltage Vdd and the second transistor T2. (Vth) can be compensated.

Embodiment of the present invention described above is an example of the present invention, it is possible to change freely within the scope included in the spirit of the present invention. Accordingly, the invention includes modifications of the invention within the scope of the appended claims and their equivalents.

1 is an equivalent circuit diagram of a pixel of a general organic light emitting display device.

2 is a view schematically showing an organic light emitting display device according to an embodiment of the present invention.

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

4 is a waveform diagram of a voltage supplied to a gate wiring and a data wiring of an organic light emitting display device according to an exemplary embodiment of the present invention.

FIG. 5 is a view illustrating a process in which a threshold voltage is sampled when the threshold voltage of the organic light emitting diode is shifted in the organic light emitting diode according to the embodiment of the present invention to correct the shift of the threshold voltage. FIG.

6 is a view schematically showing an organic light emitting display device according to another embodiment of the present invention.

7 is an equivalent circuit diagram of a pixel of an organic light emitting display device according to another embodiment of the present invention;

8 is a waveform diagram of a voltage supplied to a gate wiring and a data wiring of an organic light emitting display device according to another exemplary embodiment of the present invention.

Claims (10)

Data wiring; An n-th, n-th, and n-th gate wiring line which intersects the data wiring line and is sequentially arranged; A switching transistor connected to the nth gate line and a data line; A driving transistor supplying a current to the organic light emitting diode and connected to a power supply voltage line at a source electrode; A first capacitor connected between the drain electrode of the switching transistor and the gate electrode of the driving transistor; A first sampling transistor connected between the first node to which the switching transistor and the first capacitor are connected, and the organic light emitting diode to sample the threshold voltage of the organic light emitting diode at the first node; A second sampling transistor connected between a second node connected to the driving transistor and the first capacitor and a drain electrode of the driving transistor, the second sampling transistor sampling a power supply voltage and a threshold voltage of the driving transistor at the second node; A light emission control transistor connected to an nth light emission control line and connected between the organic light emitting diode and a drain electrode of the driving transistor to control a current supplied to the organic light emitting diode; A second capacitor connected between any one of the first and second nodes and the power supply voltage wiring Organic electroluminescent device comprising a. The method of claim 1, The first and second sampling transistors are connected to the n-th gate wiring. The method of claim 2, The other electrode of the second capacitor is connected to the first node, A turn-on voltage is applied to the n-th light emission control line during the first first period of the section where the turn-on voltage is applied to the n-th gate wiring, The turn-off voltage is applied to the nth light emitting control line during the second half of the period where the turn-on voltage is applied to the n-th gate wiring and the third period when the turn-on voltage is applied to the nth gate wiring. Licensed, The turn-on voltage is applied to the nth light emitting control wiring after the third section. Organic electroluminescent device. The method of claim 2, A first initialization transistor connected to the n-th-th gate line and applying an initialization voltage to the first node; a first initialization transistor connected to the n-th-second gate line and applying the initialization voltage to the second node. An organic light emitting display device further comprising an initialization transistor. The method of claim 4, wherein The other electrode of the second capacitor is connected to the second node, A turn-off voltage is applied to the n-th light emission control line during a first section in which a turn-on voltage is applied to the n-th gate wiring and a second section in which a turn-on voltage is applied to the n-th gate wiring. , The turn-on voltage is applied to the nth light emitting control wiring after the second section. Organic electroluminescent device. A first node to which the switching transistor connected to the nth gate line and the data line of the n-2, n-1, nth gate lines and the data line and the first capacitor are connected, a driving transistor connected to the power supply voltage line, and the first node Initializing a second node to which the one capacitor is connected; After initializing the first and second nodes, the first sampling transistor is turned on to sample the threshold voltage of the organic light emitting diode at the first node, and the second sampling transistor is turned on to supply power to the second node. Sampling a threshold voltage of the driving transistor; After sampling the threshold voltage of the organic light emitting diode and the threshold voltage of the driving transistor, applying a data voltage to the first node to form a current passing through the driving transistor; Turning on a light emitting control transistor connected to an nth light emitting control wiring to supply a current passing through the driving transistor to the organic light emitting diode; Organic electroluminescent device driving method comprising a. The method of claim 6, And the first and second sampling transistors are connected to the n-th gate wiring. The method of claim 7, wherein Initializing the first and second nodes, The turn-on voltage is applied to the n-th light emission control line during the first section of the section where the turn-on voltage is applied to the n-th gate wiring, so that the first and second nodes are electrically connected to the organic light emitting diode. Connecting to the Sampling the threshold voltage of the organic light emitting diode and the threshold voltage of the driving transistor, Electrically connecting the second node to the organic light emitting diode by applying a turn-off voltage to the n-th light emitting control wiring during the second half of the section where the turn-on voltage is applied to the n-th gate wiring. And electrically connecting the second node to the drain electrode of the driving transistor. Organic electroluminescent device driving method. The method of claim 7, wherein Initializing the first and second nodes, During the first period during which the turn-on voltage is applied to the n-th-th gate line, the first and second initialization transistors connected to the n-th-th gate line are turned on, through the first and second initialization transistors, respectively. Applying an initialization voltage to the first and second nodes, Sampling the threshold voltage of the organic light emitting diode and the threshold voltage of the driving transistor, A turn-off voltage is applied to the n-th light emission control line during the second period during which the turn-on voltage is applied to the n-th gate wiring, thereby electrically connecting the first node to the organic light emitting diode and Electrically connecting two nodes to a drain electrode of the driving transistor; Organic electroluminescent device driving method. The method of claim 6, And storing the data voltage component using a second capacitor connected to the power supply voltage line.

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