KR20100054895A - Organic electro-luminescent display device and driving method thereof - Google Patents

Organic electro-luminescent display device and driving method thereof Download PDF

Info

Publication number
KR20100054895A
KR20100054895A KR1020080113713A KR20080113713A KR20100054895A KR 20100054895 A KR20100054895 A KR 20100054895A KR 1020080113713 A KR1020080113713 A KR 1020080113713A KR 20080113713 A KR20080113713 A KR 20080113713A KR 20100054895 A KR20100054895 A KR 20100054895A
Authority
KR
South Korea
Prior art keywords
thin film
film transistor
voltage
switching
driving
Prior art date
Application number
KR1020080113713A
Other languages
Korean (ko)
Inventor
김승태
배한진
이정윤
임호민
Original Assignee
엘지디스플레이 주식회사
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 엘지디스플레이 주식회사 filed Critical 엘지디스플레이 주식회사
Priority to KR1020080113713A priority Critical patent/KR20100054895A/en
Publication of KR20100054895A publication Critical patent/KR20100054895A/en

Links

Images

Classifications

    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104Forming layers
    • H01L21/02365Forming inorganic semiconducting materials on a substrate
    • H01L21/02518Deposited layers
    • H01L21/0257Doping during depositing
    • H01L21/02573Conductivity type
    • H01L21/02576N-type
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L21/00Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104Forming layers
    • H01L21/02365Forming inorganic semiconducting materials on a substrate
    • H01L21/02518Deposited layers
    • H01L21/0257Doping during depositing
    • H01L21/02573Conductivity type
    • H01L21/02579P-type
    • GPHYSICS
    • G09EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09GARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2310/00Command of the display device
    • G09G2310/02Addressing, scanning or driving the display screen or processing steps related thereto
    • G09G2310/0202Addressing of scan or signal lines
    • HELECTRICITY
    • H01BASIC ELECTRIC ELEMENTS
    • H01LSEMICONDUCTOR DEVICES; ELECTRIC SOLID STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H01L2924/00Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
    • H01L2924/10Details of semiconductor or other solid state devices to be connected
    • H01L2924/11Device type
    • H01L2924/13Discrete devices, e.g. 3 terminal devices
    • H01L2924/1304Transistor
    • H01L2924/1306Field-effect transistor [FET]
    • H01L2924/13069Thin film transistor [TFT]

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting display device and a method of driving the same. By removing the threshold voltage (Vth) component of the driving thin film transistor (DR) which has a large influence on the change in the provided driving current (I OLED ), the driving thin film transistor ( There is an advantage to provide a high-quality organic electroluminescent display device exhibiting a uniform brightness by minimizing the variation of electrical characteristics of DR).

Description

Organic electroluminescent display device and driving method thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting display device and a method of driving the same, and in particular, to reduce the uniformity of the driving current of the organic light emitting diode (OLED) due to variations in the electrical characteristics of the thin film transistor, and particularly to change the threshold voltage (Vth). The present invention relates to an organic light emitting display device and a method of driving the same, which compensate for a change in an organic light emitting diode (OLED) driving current.

In order to solve the drawbacks of the active matrix liquid crystal display (AMLCD) which does not have its own luminescence property, the proposed display device is an active matrix organic light emitting display device (AMOLED). A self-luminous display device which emits light by emitting light, has advantages of being able to be driven at a low voltage and capable of thin manufacturing.

1 illustrates a pixel structure of an active matrix organic electroluminescent display device according to the related art, and illustrates a pixel structure of a two-transistor one-capacitor 2T-1C.

The substrate includes a scan line S, a data line D, a switching thin film transistor SW, a capacitor C, a driving thin film transistor DR, and an organic light emitting diode OLED. Each of the thin film transistors SW and DR is an NMOS channel type thin film transistor TFT.

A gate of the switching thin film transistor SW is connected to the scan line S, and a source thereof is connected to the data line D. One side of the capacitor C is connected to the drain of the switching thin film transistor SW, and the other side is applied with a ground voltage VSS.

The drain of the driving thin film transistor DR is connected to the cathode of the organic light emitting diode OLED to which the driving voltage VDD is applied, the gate is connected to the drain of the switching thin film transistor SW, and the source is ground. ) A ground voltage VSS such as a potential is applied.

The driving method of the pixel illustrated in FIG. 1 will be described with reference to the signal timing diagram of FIG. 2.

When the switching thin film transistor SW is turned on by a scan signal which is a positive selection voltage Vgh applied from the gate driver IC (not shown) to the scan line S, the switching line SW is turned on to the data line D. Electric charges are accumulated in the capacitor C by the applied data voltage Vdata. In this case, the data voltage Vdata is a bipolar voltage because the channel type of the driving thin film transistor DR is NMOS-type. Thereafter, the amount of current flowing in the channel of the driving thin film transistor DR is determined according to the potential difference between the voltage charged in the capacitor C and the driving voltage VDD, and the amount of light emitted is determined by the determined amount of current. The organic light emitting diode OLED emits light.

However, in the organic light emitting display device having the pixel structure, the pixels exhibit different luminance under the same conditions due to variations in electrical characteristics between the driving thin film transistors DR of each pixel of the panel. do.

These causes are different depending on the backplane of the panel, the characteristics of the driving thin film transistor (DR) by the excimer laser annealing (ELA) process in the panel using a low-temperature polysilicon (LTPS) backplane. Due to the change, even when the same voltage is applied to the driving thin film transistor DR of each pixel, a different current flows for each channel, thereby decreasing luminance uniformity.

In addition, in the panel using the amorphous silicon (a-Si) backplane, the manufacturing process has little effect, but the characteristic change of the driving thin film transistor DR occurs due to deterioration due to driving, and thus each driving thin film transistor TFT is produced. The problem of inferior luminance uniformity is caused by different degree of deterioration.

Accordingly, as shown in FIG. 3, the electrical characteristic deviation of the driving thin film transistor DR causes the current flowing through the organic light emitting diode OLED to be different for each pixel, and thus displays different luminance even with pixels having the same condition. Therefore, it is natural that luminance uniformity of the entire panel is inferior, which is recognized as image distortion such as afterimage or mura on the panel.

Accordingly, in order to improve the panel luminance uniformity deterioration caused by the variation of the electrical characteristics of the driving thin film transistor (DR of FIG. 1) configured for each pixel of the organic light emitting display device, referring to Equation (1) below, manufacturing process by improving the characteristic variation caused by the variation of the threshold voltage (Vth) of the thin film transistor which has the greatest influence on the change of the driving current (I OLED ) provided to the organic light emitting diode (OLED) through the (square) relationship An object of the present invention is to provide a high-quality organic light emitting display device that exhibits uniform luminance by minimizing variations in electrical characteristics of the driving thin film transistor DR, which may be caused by deterioration during driving.

Formula (1) I OLED = 1/2 * μ * C OX * (W / L) * (Vgs-Vth) 2

In Equation (1), μ: mobility, C OX : capacitance, W / L: channel ratio (width / length), Vgs: gate-source voltage, Vth: threshold voltage

In order to achieve the above object, the present invention provides an organic light emitting device to which a driving voltage or a ground voltage is applied; A driving thin film transistor for supplying a driving current to the organic light emitting device; A first switching thin film transistor inputted with a data voltage and controlled by a-th (a: random natural number) scan signal to output the data voltage; A second switching thin film transistor configured to receive an initialization voltage and to be controlled to be switched by an initialization signal to output the initialization voltage; A third switching thin film transistor configured between the second switching thin film transistor and the driving thin film transistor and switched by the a-th scan signal; A fourth switching thin film transistor configured between an output terminal of the first switching thin film transistor and the driving thin film transistor, the fourth switching thin film transistor being switched and controlled by a current supply signal; A first capacitor formed between the gate terminal and the source terminal of the driving thin film transistor; An organic light emitting display device including a second capacitor configured between an output terminal of the first switching thin film transistor and a gate terminal of the driving thin film transistor is provided.

In the organic light emitting display device, the base voltage is characterized in that the voltage level is variable.

In the organic light emitting display device, the third switching thin film transistor is controlled to be controlled by a selection signal.

In the organic light emitting display device, the selection signal is the same signal as the a-th scan signal.

In the organic light emitting display device, the first to fourth switching thin film transistors and the fourth switching thin film transistors and the driving thin film transistors are all NMOS-type or all PMOS-type.

In the organic light emitting display device, when the NMOS type, the initializing voltage is a voltage lower than or equal to the source terminal voltage of the driving thin film transistor, and in the case of the PMOS type, the initializing voltage is a source of the driving thin film transistor. The voltage is higher than or equal to the voltage.

In the organic light emitting display device, in the case of the NMOS type, the data voltage is higher than the base voltage, and in the case of the PMOS type, the data voltage is lower than the base voltage.

In the organic light emitting display device, the first capacitor is a parasitic capacitance component formed between the gate terminal and the source terminal of the driving thin film transistor DR.

In addition, the present invention provides an organic light emitting device to which a driving voltage or a ground voltage is applied; A driving thin film transistor for supplying a driving current to the organic light emitting device; A first switching thin film transistor having a data voltage input thereto, the first switching thin film transistor being switched by a a-th (a: arbitrary natural number) scan signal and outputting the data voltage; A second switching thin film transistor configured to receive an initialization voltage and to be controlled to be switched by an initialization signal to output the initialization voltage; A third switching thin film transistor configured between the second switching thin film transistor and the driving thin film transistor and switched by the a-th scan signal; A fourth switching thin film transistor configured between an output terminal of the first switching thin film transistor and the driving thin film transistor, the fourth switching thin film transistor being switched and controlled by a current supply signal; A first capacitor formed between the gate terminal and the source terminal of the driving thin film transistor; A driving method of an organic light emitting display device comprising a second capacitor configured between an output terminal of the first switching thin film transistor and a gate terminal of the driving thin film transistor.

(1) applying the base voltage to a high level and switching the second switching thin film transistor to an on-switching state; (2) providing the initialization voltage and switching the first and third switching thin film transistors into an on-switching state; (3) switching the second switching thin film transistor to an off-switching state; (4) providing the data voltage; (5) applying the base voltage to a low level, switching the fourth switching thin film transistor to an on-switching state, and switching the first third switching thin film transistor to an off-switching state to emit the organic light emitting device A first driving method comprising driving;

(1) applying the base voltage to a high level and switching the second and fourth switching thin film transistors into an on-switching state; (2) providing the initialization voltage and switching the first and third switching thin film transistors into an on-switching state; (3) switching the second switching thin film transistor to an off-switching state; (4) providing the data voltage and switching the fourth switching thin film transistor to an off-switching state; (5) applying the ground voltage to a low level, switching the fourth switching thin film transistor to an on-switching state, and switching the first and third switching thin film transistors to an off-switching state to thereby form the organic light emitting device. A driving method of an organic light emitting display device is characterized by being driven by one of the second driving methods including the step of driving light emission.

In the method of driving the organic light emitting display device, the third switching thin film transistor may be controlled to be controlled by a selection signal.

In the method of driving the organic light emitting display device, the selection signal is the same signal as the a-th scan signal.

In the method of driving the organic light emitting display device, when the driving thin film transistor is an NMOS type, a base voltage having a potential higher than the voltage obtained by subtracting the threshold voltage of the organic light emitting diode from the driving voltage is applied. When the driving thin film transistor is a PMOS type, the driving voltage is applied at a voltage higher than the base voltage, and when the driving thin film transistor is a PMOS type, a base voltage having a potential lower than the voltage obtained by adding the threshold voltage of the organic light emitting diode is applied. It is characterized by applying at a voltage lower than the base voltage.

In the method of driving the organic light emitting display device, when the driving thin film transistor is an NMOS type, the driving voltage is higher than a low level voltage of the base voltage, and when the driving thin film transistor is a PMOS type, the driving voltage. Is a voltage lower than the high level voltage of the ground voltage.

According to the present invention having the above characteristics, by removing the threshold voltage (Vth) component of the driving thin film transistor (DR) which has a large influence on the change of the driving current (I OLED ) provided to the organic light emitting device (OLED) In addition, there is an advantage of providing a high quality organic electroluminescent display device that exhibits uniform luminance by minimizing variation of electrical characteristics of the driving thin film transistor DR, which may be caused by deterioration during a manufacturing process or driving.

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

4 is a pixel structure diagram of an organic light emitting display device according to a first embodiment of the present invention.

In the illustrated pixel, the organic light emitting diode OLED, the first switching thin film transistors to the fourth switching thin film transistors S1 to S4, the driving thin film transistor DR, the first capacitor Cst1, and the second capacitor It consists of (Cst2). At this time, the first capacitor Cst1 may use a parasitic capacitance component generated between the gate terminal and the source terminal of the driving thin film transistor DR without configuring a separate capacitor device.

The driving thin film transistor DR has a ground voltage VSS applied to a source terminal, an organic light emitting diode OLED connected to a drain terminal, and switched by a signal input to a gate terminal. The driving current I OLED is supplied to the device OLED.

The first switching thin film transistor S1 receives a data voltage Vdata and an arbitrary a-th (a: natural number) scan signal {scan (a)} for displaying an image through a data line and a scan line, respectively. The switching control is performed by the scan signal scan (a) to output the data voltage Vdata for displaying an image.

An initialization voltage Vinit is input to the second switching thin film transistor S2, and is controlled to be controlled by an initialization signal init to output the initialization voltage Vinit.

The third switching thin film transistor S3 is configured between the output terminal of the second switching thin film transistor S2 and the drain terminal of the driving thin film transistor DR and is controlled by the scan signal scan (a). do.

The fourth switching thin film transistor S4 is configured between an output terminal of the first switching thin film transistor S1 and a source terminal of the driving thin film transistor DR, and is controlled by a current supply signal cs.

The first capacitor Cst1 is configured between the source terminal and the gate terminal of the driving thin film transistor DR. In this case, the first capacitor Cst1 may be replaced with a parasitic capacitance component generated between the gate terminal and the source terminal of the driving thin film transistor DR without configuring a separate capacitor device.

The second capacitor Cst2 is configured between an output terminal of the first switching thin film transistor S1 and a gate terminal of the driving thin film transistor DR.

At this time, the first switching thin film transistors to the fourth switching thin film transistors S1 to S4 and the driving thin film transistors DR are all NMOS-type channel types, but all may be configured as PMOS-types as necessary. . In addition, in the organic light emitting display device according to an embodiment of the present invention, a base voltage VSS that is changed to a high level potential and a low level potential is applied. Hereinafter, a driving method according to the utilization will be described with reference to a signal timing diagram. Let's do it.

FIG. 5 is a signal timing diagram illustrating an operation according to a first driving method of an organic light emitting display device according to a first embodiment of the present invention, wherein the base voltage VSS, the current supply signal cs, and the initialization are shown in FIG. The signal init, the initialization voltage Vdata, the scan signal scan (a), and the data voltage Vdata are shown.

First, the operation of this frame, which starts from the second section (②) after the light emission driving in the previous frame ends in the first section (①), is a negative bias application section, and is a high level base voltage (hereinafter referred to as VSS_H). ) Is applied at a high level, the current supply signal cs and the scan signal scan (a) are applied at a low level, and the initialization signal init is applied at a high level. Accordingly, the first, third, and fourth switching thin film transistors S1, S3, and S4 are switched to the off-switching state, and the second switching thin film transistor S2 is switched to the on-switching state to initialize the low level. The voltage (hereinafter referred to as Vinit_L) is output.

At this time, the voltage of the base voltage of the high level (hereinafter referred to as VSS_H) is applied as a voltage higher than the low level voltage of the initialization voltage Vinit, and thus the voltage between the gate terminal and the source terminal of the driving thin film transistor DR (ie, Vgs) is in a state where a negative bias is applied. As such, when the Vgs component is switched to the negative voltage state, the variation in the threshold voltage Vth caused by the characteristic change of the driving thin film transistor DR due to the driving of the pixel can be compensated, that is, the degradation of the pixel driving. The shifted threshold voltage Vth characteristic curve can be moved to its original position.

In the third section ③ corresponding to the next initialization section, a high level initializing voltage (hereinafter referred to as Vinit_H) is provided and a high level scan signal scan (a) is applied. Accordingly, the first, second, and third switching thin film transistors S1, S2, and S3 are in on-switching state, and the fourth switching thin film transistor S4 is in an off-switching state.

In addition, the high level initializing voltage Vinit_H is applied to a voltage higher than the high level base voltage VSS_H and the driving voltage VDD, so that the first capacitor Cst1 and the second capacitor Cst2 are respectively applied to the high voltage. A voltage for measuring the threshold voltage Vth of the driving thin film transistor DR is stored.

Thereafter, in the fourth section (④), which is the threshold voltage Vth sensing section, the initialization signal (init) is switched to the low level so that the first and third switching thin film transistors (S1, S3) are on-switching state. The second and fourth switching thin film transistors S2 and S4 are in an off-switching state.

In this case, when the low level data voltage (hereinafter, Vdata_L) lower than the high level base voltage VSS_H and the driving voltage VDD is supplied through the first switching thin film transistor S1, the first capacitor Cst1. ) Is stored in the threshold voltage Vth of the driving thin film transistor DR and (Vth + Vdata_L) is stored in the second capacitor Cst2.

Next, when a high level data voltage (hereinafter, Vdata_H) corresponding to the image data is provided in the fifth section ⑤, which is a programming period for writing image data, the threshold voltage Vth is applied to the first capacitor Cst1. The second capacitor Cst2 stores (Vth + Vdata_H). In this case, the voltage applied between the gate terminal and the source terminal of the driving thin film transistor DR, that is, Vgs, may be expressed as follows.

The formula for calculating the charge amount Q is Q = C * V, so the total charge amount Q (total)} is

Q (first capacitor) + Q (second capacitor) = Q (total),

C (first capacitor) * Vth + C (second capacitor) * (Vdata_H + Vth) = (Cst1 + Cst2) * Vgs. finally,

(2) Vgs = {Cst2 / (Cst1 + Cst2) * (Vdata_H)} + Vth

Subsequently, substituting Vgs according to Equation (2) into Equation (1),

At I OLED = 1/2 * μ * C OX * (W / L) * (Vgs-Vth) 2 ,

Equation (3) I OLED = 1/2 * μ * C OX * (W / L) * [{Cst2 / (Cst1 + Cst2)} * Vdata_H] 2

Finally, Equation (3) can be derived.

At this time, the initialization voltage Vinit is a voltage lower than or equal to a source terminal voltage of the driving thin film transistor DR when the driving thin film transistor DR is an NMOS type, and the driving thin film transistor DR is a PMOS type. In this case, the initialization voltage Vinit is higher than or equal to the source terminal voltage of the driving thin film transistor DR.

In addition, when the driving thin film transistor DR is an NMOS type, the data voltage Vdata is higher than the base voltage VSS, and when the driving thin film transistor DR is a PMOS type, the data voltage Vdata. Is a voltage lower than the base voltage VSS.

In addition, when the driving thin film transistor DR is an NMOS type, a base voltage VSS of a potential higher than the voltage obtained by subtracting the threshold voltage Vth_oled of the organic light emitting diode from the driving voltage VDD is applied. The data voltage Vdata is applied at a voltage higher than the base voltage VSS. In addition, when the driving thin film transistor DR is a PMOS type, a base voltage VSS of a potential lower than a voltage obtained by adding the threshold voltage Vth_oled of the organic light emitting diode to the driving voltage VDD is applied. The data voltage Vdata may be applied at a voltage lower than the base voltage VSS.

In addition, when the driving thin film transistor DR is an NMOS type, the driving voltage VDD is higher than the low level voltage (ie, VSS_L) of the base voltage VSS, and the driving thin film transistor DR is a PMOS. In the case of -type, the driving voltage VDD is lower than the high level voltage (ie, VSS_H) of the base voltage VSS.

As can be seen from Equation (3), the threshold voltage Vth component of the driving thin film transistor DR disappears among the elements that determine the driving current I OLED for emitting the organic light emitting diode OLED. It can be seen that.

Accordingly, in the sixth period ⑥, which is the light emission period, the base voltage VSS is switched to the low level, and the fourth switching thin film transistor S4 is switched to the on-switching state, so that a current flows in the driving thin film transistor DR. The light emission driving is performed while the threshold voltage Vth of the driving thin film transistor DR has a great influence on the change of the driving current I OLED provided to the organic light emitting diode OLED by Equation (3). It can be seen that the variation in characteristics due to the variation can be improved, and the variation in electrical characteristics of the driving thin film transistor DR, which may be caused by deterioration during the manufacturing process or driving, can be minimized.

FIG. 6 is a signal timing diagram according to the second driving method of the first embodiment of the present invention, and similarly to the first driving method of the first embodiment, the base voltage VSS, the current supply signal cs, and the initialization signal init. ), The initialization voltage Vdata, the scan signal {scan (a)}, and the data voltage Vdata.

First, the operation of this frame, which starts from the second section (②) after the light emission driving in the previous frame ends in the first section (①), is a negative bias application section, and is a high level base voltage (hereinafter referred to as VSS_H). ) Is applied at a high level, the current supply signal cs and the initialization signal init are applied at a high level, and the scan signal scan (a) is applied at a low level.

Accordingly, the first and third switching thin film transistors S1 and S3 are switched to the off-switching state, and the second and fourth switching thin film transistors S2 and S4 are switched to the on-switching state. A low level initialization voltage (hereinafter referred to as Vinit_L) is output through the switching thin film transistor S2.

In this case, the voltage of the high level base voltage (hereinafter referred to as VSS_H) is applied as a voltage higher than the low level voltage of the initialization voltage Vinit, and thus the voltage between the gate terminal and the source terminal of the driving thin film transistor DR (ie, , Vgs) is in a state where a negative bias is applied. As such, when the Vgs component is switched to the negative voltage state, the variation in the threshold voltage Vth caused by the characteristic change of the driving thin film transistor DR due to the driving of the pixel can be compensated, that is, the degradation of the pixel driving. The shifted threshold voltage Vth characteristic curve can be moved to its original position.

In the third section ③ corresponding to the next initialization section, a high level initialization voltage (hereinafter referred to as Vinit_H) and a data voltage Vdata are provided, and a high level scan signal scan (a) is applied. . Therefore, all of the first, second, third, and fourth switching thin film transistors S1, S2, S3, and S4 are on-switched.

In addition, the high level initializing voltage Vinit_H is applied to a voltage higher than the high level base voltage VSS_H and the driving voltage VDD, respectively, to the first capacitor Cst1 and the second capacitor Cst2. A voltage for measuring the threshold voltage Vth of the driving thin film transistor DR is stored.

Thereafter, in the fourth section ④ which is the threshold voltage Vth sensing section, the initialization signal init is switched to the low level so that the first, third, and fourth switching thin film transistors S1, S3, and S4 are The on-switching state and the second switching thin film transistor S2 are in the off-switching state.

At this time, the threshold voltage Vth of the driving thin film transistor DR is stored in the first capacitor Cst1 and the voltage (Vth + Vdata) is stored in the second capacitor Cst2.

Next, when the fourth switching thin film transistor S4 is switched to the off-switching state by switching the current supply signal cs to a low level in the fifth section ⑤, which is a programming section for writing image data, A voltage applied between the gate terminal and the source terminal of the driving thin film transistor DR in a state where a threshold voltage Vth is stored in the first capacitor Cst1 and (Vth + Vdata) is stored in the second capacitor Cst2, In other words, Vgs can be expressed as

The formula for calculating the charge amount Q is Q = C * V, so the total charge amount Q (total)} is

Q (first capacitor) + Q (second capacitor) = Q (total),

C (first capacitor) * Vth + C (second capacitor) * (Vdata + Vth) = (Cst1 + Cst2) * Vgs. finally,

Equation (4) Vgs = {Cst2 / (Cst1 + Cst2) * (Vdata)} + Vth

Subsequently, substituting Vgs according to Equation (2) into Equation (1),

At I OLED = 1/2 * μ * C OX * (W / L) * (Vgs-Vth) 2 ,

Equation (5) I OLED = 1/2 * μ * C OX * (W / L) * [{Cst2 / (Cst1 + Cst2)} * Vdata] 2

Finally, Equation (3) can be derived.

That is, as shown in Equation (5), the threshold voltage Vth component of the driving thin film transistor DR among the elements that determine the driving current I OLED for emitting the organic light emitting diode OLED. You can see this disappeared.

Subsequently, in the sixth period ⑥, which is the light emission period, the base voltage VSS is changed to a low level, and the fourth switching thin film transistor S4 is switched to an on-switching state to provide a current to the driving thin film transistor DR. The light emission driving is performed while the threshold voltage of the driving thin film transistor DR having a great influence on the change of the driving current I OLED provided to the organic light emitting diode OLED by Equation (5). Vth) it can be seen to improve the characteristic deviation caused by the variation, it is possible to minimize the electrical characteristic deviation of the driving thin film transistor (DR) that may be caused by deterioration during the manufacturing process or driving.

FIG. 7 is a pixel structure diagram of an organic light emitting display device according to a second exemplary embodiment of the present invention, except that a switching signal of the third switching thin film transistor S3 is separated into a separate signal, that is, a selection signal sel. The same is true for the features of the pixel structure of the first embodiment described above. In this case, the selection signal sel of the third switching thin film transistor S3 may be substantially the same as the a-th scan signal a (natural number) for switching the first switching thin film transistor S1.

Accordingly, the first driving method and the second driving method of the second embodiment of the present invention shown in FIGS. 8 and 9 correspond to the first driving method and the second driving method of the first embodiment described with reference to FIGS. 5 and 6, respectively. The same description as described above will be omitted.

1 is a pixel structure diagram illustrating a pixel structure of an active matrix organic light emitting display device according to the related art.

2 is a signal timing diagram for driving the pixel of FIG. 1.

FIG. 3 is a voltage-current graph for explaining a difference between driving current I OLED flowing through the organic light emitting diode OLED according to variation of electrical characteristics of the driving thin film transistor DR shown in FIG. 1.

4 is a pixel structure diagram of an organic light emitting display device according to a first embodiment of the present invention.

5 is a signal timing diagram illustrating a first driving method of an organic light emitting display device according to a first embodiment of the present invention.

6 is a signal timing diagram illustrating a second driving method of an organic light emitting display device according to a first embodiment of the present invention.

7 is a pixel structure diagram of an organic light emitting display device according to a second embodiment of the present invention.

8 is a signal timing diagram illustrating a first driving method of an organic light emitting display device according to a second embodiment of the present invention.

9 is a signal timing diagram illustrating a second driving method of an organic light emitting display device according to a second embodiment of the present invention.

<Brief description of the main parts of the drawing>

DR: driving thin film transistor Cst1, Cst2: first and second capacitors

OLED: organic light emitting device

S1 to S4: First to fourth switching thin film transistor

Claims (13)

  1. An organic light emitting diode to which a driving voltage or a ground voltage is applied;
    A driving thin film transistor for supplying a driving current to the organic light emitting device;
    A first switching thin film transistor having a data voltage input thereto, the first switching thin film transistor being switched by a a-th (a: arbitrary natural number) scan signal and outputting the data voltage;
    A second switching thin film transistor configured to receive an initialization voltage and to be controlled to be switched by an initialization signal to output the initialization voltage;
    A third switching thin film transistor configured between the second switching thin film transistor and the driving thin film transistor and switched by the a-th scan signal;
    A fourth switching thin film transistor configured between an output terminal of the first switching thin film transistor and the driving thin film transistor, the fourth switching thin film transistor being switched and controlled by a current supply signal;
    A first capacitor formed between the gate terminal and the source terminal of the driving thin film transistor;
    A second capacitor configured between an output terminal of the first switching thin film transistor and a gate terminal of the driving thin film transistor
    Organic electroluminescent display device comprising a
  2. The method according to claim 1,
    The base voltage is an organic light emitting display device, characterized in that the voltage level is variable
  3. The method according to claim 2,
    The third switching thin film transistor is an organic light emitting display device, characterized in that the switching control by a selection signal
  4. The method according to claim 3,
    And the selection signal is the same signal as the a-th scan signal.
  5. The method according to claim 4,
    The first to fourth switching thin film transistors and the fourth switching thin film transistor and the driving thin film transistor are all NMOS-type or all PMOS-type organic light emitting display device
  6. The method according to claim 5,
    In the case of the NMOS-type, the initialization voltage is a voltage lower than or equal to the source terminal voltage of the driving thin film transistor, and in the case of the PMOS-type, the initialization voltage is a voltage higher than or equal to the source terminal voltage of the driving thin film transistor. Organic electroluminescent display device
  7. The method of claim 6,
    In the case of the NMOS type, the data voltage is higher than the base voltage, and in the case of the PMOS type, the data voltage is lower than the base voltage.
  8. The method according to claim 1,
    The first capacitor is an organic light emitting display device, characterized in that the parasitic capacitance component formed between the gate terminal and the source terminal of the driving thin film transistor DR.
  9. An organic light emitting diode to which a driving voltage or a ground voltage is applied; A driving thin film transistor for supplying a driving current to the organic light emitting device; A first switching thin film transistor having a data voltage input thereto, the first switching thin film transistor being switched by a a-th (a: arbitrary natural number) scan signal and outputting the data voltage; A second switching thin film transistor configured to receive an initialization voltage and to be controlled to be switched by an initialization signal to output the initialization voltage; A third switching thin film transistor configured between the second switching thin film transistor and the driving thin film transistor and switched by the a-th scan signal; A fourth switching thin film transistor configured between an output terminal of the first switching thin film transistor and the driving thin film transistor, the fourth switching thin film transistor being switched and controlled by a current supply signal; A first capacitor formed between the gate terminal and the source terminal of the driving thin film transistor; A driving method of an organic light emitting display device comprising a second capacitor configured between an output terminal of the first switching thin film transistor and a gate terminal of the driving thin film transistor.
    (1) applying the base voltage to a high level and switching the second switching thin film transistor to an on-switching state;
    (2) providing the initialization voltage and switching the first and third switching thin film transistors into an on-switching state;
    (3) switching the second switching thin film transistor to an off-switching state;
    (4) providing the data voltage;
    (5) applying the base voltage to a low level, switching the fourth switching thin film transistor to an on-switching state, and switching the first third switching thin film transistor to an off-switching state to emit the organic light emitting device Driving step
    The first driving method comprising a,
    (1) applying the base voltage to a high level and switching the second and fourth switching thin film transistors into an on-switching state;
    (2) providing the initialization voltage and switching the first and third switching thin film transistors into an on-switching state;
    (3) switching the second switching thin film transistor to an off-switching state;
    (4) providing the data voltage and switching the fourth switching thin film transistor to an off-switching state;
    (5) applying the ground voltage to a low level, switching the fourth switching thin film transistor to an on-switching state, and switching the first and third switching thin film transistors to an off-switching state to thereby form the organic light emitting device. Driving light emission
    A method of driving an organic light emitting display device, characterized in that driven by one of the second driving method including a.
  10. The method of claim 9,
    The third switching thin film transistor is controlled by a selection signal driving method of an organic light emitting display device
  11. The method of claim 10,
    The selection signal is a driving method of an organic light emitting display device, characterized in that the same signal as the a-th scan signal.
  12. The method of claim 9,
    When the driving thin film transistor is an NMOS type, a base voltage of a potential higher than the voltage obtained by subtracting the threshold voltage of the organic light emitting diode from the driving voltage is applied, and the data voltage is applied to a voltage higher than the base voltage. When the driving thin film transistor is a PMOS type, a base voltage of a potential lower than a voltage obtained by adding the threshold voltage of the organic light emitting diode to the driving voltage is applied, and the data voltage is applied to a voltage lower than the base voltage. Method of driving an organic light emitting display device
  13. The method of claim 9,
    The driving voltage is higher than the low level voltage of the base voltage when the driving thin film transistor is NMOS-type, and the driving voltage is lower than the high level voltage of the base voltage when the driving thin film transistor is PMOS type. A method of driving an organic light emitting display device, characterized in that
KR1020080113713A 2008-11-15 2008-11-15 Organic electro-luminescent display device and driving method thereof KR20100054895A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
KR1020080113713A KR20100054895A (en) 2008-11-15 2008-11-15 Organic electro-luminescent display device and driving method thereof

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
KR1020080113713A KR20100054895A (en) 2008-11-15 2008-11-15 Organic electro-luminescent display device and driving method thereof

Publications (1)

Publication Number Publication Date
KR20100054895A true KR20100054895A (en) 2010-05-26

Family

ID=42279447

Family Applications (1)

Application Number Title Priority Date Filing Date
KR1020080113713A KR20100054895A (en) 2008-11-15 2008-11-15 Organic electro-luminescent display device and driving method thereof

Country Status (1)

Country Link
KR (1) KR20100054895A (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101411619B1 (en) * 2012-09-27 2014-06-25 엘지디스플레이 주식회사 Pixel circuit and method for driving thereof, and organic light emitting display device using the same
US9148930B2 (en) 2012-12-13 2015-09-29 Samsung Display Co., Ltd. Pixel and organic light emitting display using the same

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR101411619B1 (en) * 2012-09-27 2014-06-25 엘지디스플레이 주식회사 Pixel circuit and method for driving thereof, and organic light emitting display device using the same
US9148930B2 (en) 2012-12-13 2015-09-29 Samsung Display Co., Ltd. Pixel and organic light emitting display using the same

Similar Documents

Publication Publication Date Title
TWI389074B (en) Method and system for programming and driving active matrix light emitting device pixel
US7868859B2 (en) Self-luminous display device and driving method of the same
CN101251978B (en) Display device and driving method thereof
US7719492B2 (en) Threshold voltage compensation method for electroluminescent display devices
US7564433B2 (en) Active matrix display devices
KR101202040B1 (en) Organic light emitting diode display and driving method thereof
CN1591105B (en) Electro-optical device, method of driving the same, and electronic apparatus
US7236149B2 (en) Pixel circuit, display device, and driving method of pixel circuit
JP5466694B2 (en) System and driving method for light emitting device display
JP3901105B2 (en) Pixel circuit, display device, and driving method of pixel circuit
JP2007323040A (en) Organic light-emitting diode display device and driving method thereof
US7764248B2 (en) Display and method for driving display
JP2008529071A (en) Voltage-programmed pixel circuit, display system, and driving method thereof
US8913090B2 (en) Pixel circuit, organic electro-luminescent display apparatus, and method of driving the same
US9305494B2 (en) Organic light emitting display device and method for driving the same
US7898509B2 (en) Pixel circuit, display, and method for driving pixel circuit
KR20110139764A (en) Display device using capacitor coupled light emission control transitors
JP2009533717A (en) Stable drive scheme for active matrix display
US8531361B2 (en) Organic light emitting diode display and method of driving the same
JP4398413B2 (en) Pixel drive circuit with threshold voltage compensation
JP2009508168A (en) Luminance reduction compensation technology in electroluminance devices
JP4131227B2 (en) Pixel circuit, display device, and driving method of pixel circuit
US8736523B2 (en) Pixel circuit configured to perform initialization and compensation at different time periods and organic electroluminescent display including the same
JP2004295131A (en) Drive circuit for display device
JP5665256B2 (en) Luminescent display device

Legal Events

Date Code Title Description
WITN Withdrawal due to no request for examination