KR101594679B1 - Organic light emitting diode display device - Google Patents

Abstract

The exemplary embodiment of the present invention forms a reference voltage line corresponding to R, G, and B sub-pixels and W sub-pixels in the organic light emitting diode panel to individually control the reference voltage applied to each pixel to obtain an optimal luminance Can be implemented.

Description

TECHNICAL FIELD [0001] The present invention relates to an organic light emitting diode (OLED) display device,

The present invention relates to an organic light emitting diode display.

2. Description of the Related Art [0002] With the development of information society in recent years, demands for the display field have been increasing in various forms. In response to this demand, various flat panel display devices having characteristics such as thinning, light weight and low power consumption have been developed, A liquid crystal display device, a plasma display panel device, and an organic light emitting diode (OLED) device have been studied.

An organic light emitting diode (OLED) device is a self-emitting display device using an organic compound emitting light such as red (R), green (G), and blue (B) Panel and a drive circuit. Therefore, unlike a liquid crystal display device, an organic light emitting diode display device does not require a separate light source. As a result, there is no need for a backlight unit, so that the manufacturing process is simple compared with a liquid crystal display device, and the manufacturing cost is reduced. Control ratio, etc., and is capable of DC low voltage driving, has a high response speed, is resistant to external impact, and has a wide operating temperature range. Particularly, in the active matrix type, a voltage for controlling a current applied to a pixel region is charged in a storage capacitor, and a voltage is maintained until a next frame signal is applied, Regardless of the number of gate wirings. Therefore, in the active matrix system, even if a low current is applied, the same brightness is exhibited, which has advantages of low power consumption and large size.

Each of the red (R), green (G), blue (B) and white (W) pixels of the conventional organic light emitting diode display device includes an organic light emitting diode and a driving transistor for controlling current flowing in the organic light emitting diode can do.

A current flowing in the driving transistor can be adjusted according to a potential difference between the gate and the source terminal of the driving transistor and the organic light emitting diode can emit light while a current flowing in the driving transistor flows in the organic light emitting diode. That is, it is possible to control the degree of emission of the organic light emitting diode by controlling a voltage applied to the driving transistor. However, such a conventional organic light emitting diode display device has a problem that it is difficult to obtain the optimum luminance due to the deviation of the threshold voltage of the driving transistor.

The embodiment of the present invention provides an organic light emitting diode display device having a reference voltage line corresponding to each pixel for optimal luminance implementation.

An organic light emitting diode display device according to an embodiment of the present invention includes a driving transistor, an organic light emitting diode that emits light by a current adjusted in accordance with a potential difference between gate and source terminals of the driving transistor, And a plurality of red (R), green (G), blue (B) and white (W) pixels each including a sensing transistor for supplying either one of a first reference voltage and a second reference voltage to the source terminal, The first reference voltage is determined according to a threshold voltage of the driving transistors of the R, G, and B pixels and is supplied to the source terminals of the driving transistors of the R, G, and B pixels. And is determined according to the threshold voltage of the driving transistor and supplied to the source terminal of the driving transistor of the W pixel.

In the organic light emitting diode display device according to an embodiment of the present invention, each of the pixels further includes a scan transistor controlled by a scan signal on a gate line and supplying a data voltage on a data line to a gate terminal of the drive transistor, A data voltage is supplied to a gate terminal of the driving transistor and an initialization voltage to a source terminal of the driving transistor during an initialization period to vary a voltage on a source terminal of the driving transistor during a sensing period, A threshold voltage of the driving transistor is sensed by sensing a voltage on a terminal, and the first and second reference voltages are supplied to a source terminal of the driving transistor during a light emission period.

In the organic light emitting diode display according to the embodiment of the present invention, the sensing transistors of the R, G and B pixels share a first sub reference voltage line, and the sensing transistor of the W pixel is connected to a second sub reference voltage line Emitting diode display device.

In the organic light emitting diode display according to an embodiment of the present invention, the sensing transistor supplies a voltage on the sub reference voltage line to a source electrode of the driving transistor in response to a sensing signal.

In the organic light emitting diode display according to an embodiment of the present invention, an initialization voltage on the sub reference voltage line is supplied to a source electrode of the driving transistor during the initialization period, and a source terminal of the driving transistor is floated Floating) organic light emitting diode display.

The organic light emitting diode display device according to the present invention further includes a sensing unit sensing a voltage on a source terminal of the driving transistor and detecting a threshold voltage of the driving transistor from a sensed voltage, .

In the organic light emitting diode display according to an embodiment of the present invention, the threshold voltage detected from the sensing unit is set to a value corresponding to a scattering degree with respect to a threshold voltage of the driving transistor of the R, G and B pixels and a threshold voltage of the driving transistor of the W pixel And a reference voltage portion for setting the first and second reference voltages from a scattering diagram for the organic light emitting diode display.

In the organic light emitting diode display according to an embodiment of the present invention, a main reference voltage line for supplying the first and second reference voltages provided from the reference voltage unit to the first and second sub reference voltage lines; And a switching device for selectively connecting the main reference voltage line and the first and second sub reference voltage lines.

In the organic light emitting diode display device according to the embodiment of the present invention,

A first switching element for controlling an electrical connection between the main reference voltage line and the first sub reference voltage line and a second switching element for controlling an electrical connection between the main reference voltage line and the second sub reference voltage line The organic light emitting diode display device.

In the organic light emitting diode display according to an exemplary embodiment of the present invention, a demultiplexer for selectively connecting any one of the first and second sub reference voltage lines to the reference voltage unit; Further comprising an organic light emitting diode display device.

The exemplary embodiment of the present invention forms a reference voltage line corresponding to R, G, and B sub-pixels and W sub-pixels in the organic light emitting diode panel to individually control the reference voltage applied to each pixel to obtain an optimal luminance Can be implemented.

1 is a view showing an organic light emitting diode display device.
2 is a view showing an organic light emitting diode display device.
Fig. 3 shows the distribution of the threshold voltages of R, G and B sub-pixels and W sub-pixels.
4 is a block diagram illustrating a sensing unit of an organic light emitting diode display according to an exemplary embodiment of the present invention.
5 is a diagram illustrating a structure of a reference voltage supply unit and pixels of an organic light emitting diode display according to an embodiment of the present invention.
6 to 8 are diagrams showing pixels of any one of R, G, B, and W according to an embodiment of the present invention.
9 is a waveform diagram for explaining the threshold voltage compensation.
10 is a circuit diagram of R pixels and W pixels among RGB pixels according to an embodiment of the present invention.
Figs. 11 to 13 are diagrams showing waveforms applied to the circuit diagram of Fig. 10. Fig.

Hereinafter, an organic light emitting diode display device according to an embodiment of the present invention will be described in detail with reference to the drawings. The following embodiments are provided by way of example so that those skilled in the art can fully understand the spirit of the present invention. Therefore, the present invention is not limited to the embodiments described below, but may be embodied in other forms. In the drawings, the size and thickness of an apparatus may be exaggerated for convenience. Like reference numerals designate like elements throughout the specification.

The organic light emitting diode (OLED) display device according to the present invention supplies a reference voltage to each sub-pixel of RGBW of an organic light emitting diode. The configuration and operation of the organic light emitting diode display device and a specific configuration of the organic light emitting diode device will be described first.

1 is a view showing an organic light emitting diode display device.

Referring to FIG. 1, the organic light emitting diode display device includes an electron injection layer (EIL), an electron transport layer (ETL), and an electron transport layer (ETL) stacked between a cathode (anode) (EML), a hole transport layer (HTL), and a hole injection layer (HIL). In this organic light emitting diode display device, when a predetermined voltage is applied between the anode and the cathode, electrons generated from the cathode move to the light emitting layer through the electron injection layer and the electron transport layer, and holes generated from the anode move to the hole injection layer and the hole Transporting layer to the light-emitting layer. Thus, in the light emitting layer, electrons and holes supplied from the electron transporting layer and the hole transporting layer are recombined to emit light.

2 is a view showing an organic light emitting diode display device.

The active matrix organic light emitting diode display device 100 using the organic light emitting diode display device described above includes a pixel 101, an organic light emitting diode panel 102, a scan driver 103, a data driver 104, A timing controller 106, a power supply 107, a supply pad 108, a base pad 109, a reference voltage unit 110, and a sensing unit 111, as shown in FIG.

 An organic light emitting diode (OLED) panel 102 having pixels 101 arranged at intersections of scan lines SL and data lines DL, respectively, as shown in FIG. 2, A data driver 104 for driving the data lines DL of the organic light emitting diode panel 102 and a data driver 104 for driving the scan lines SL of the data driver 104, A gamma voltage generator 105 for supplying a plurality of gamma voltages to the scan driver 103 and a timing controller 106 and pixels 101 for controlling the data driver 104 and the scan driver 103, The power supply unit 107 may be provided.

The pixels 101 may include sub-pixels that emit R, G, B, and W, respectively.

In the organic light emitting diode panel 102, the pixels 101 are arranged in a matrix form. The organic light emitting diode panel 102 is provided with a supply pad 108 for receiving a high voltage source VDD from the power supply unit 107 and a base pad 109 for receiving a ground voltage GND from the power supply unit 107 Can be installed.

The high potential power supply VDD supplied to the supply pad 108 is supplied to each of the pixels 101 and the base low voltage GND supplied to the base pad 109 is also supplied to each of the pixels 101. [ . The scan driver 103 may sequentially drive the scan lines SL by supplying scan pulses to the scan lines SL.

The gamma voltage generator 105 may supply a gamma voltage having various voltage values to the data driver 104.

The data driver 104 converts the digital data signal input from the timing controller 106 into an analog data signal using the gamma voltage from the gamma voltage generator 105. [ The data driver 104 supplies the analog data signal to the data lines DL on the organic light emitting diode panel 102 whenever a scan pulse is supplied to any one of the scan lines.

The timing controller 106 generates a data control signal for controlling the data driver 104 and a scan control signal for controlling the scan driver 103 using synchronous signals supplied from an external system (for example, a graphics card) .

The data control signal generated by the timing control unit 106 is supplied to the data driver 104 to control the data driver 104.

The scan control signal generated by the timing controller 106 is supplied to the scan driver 103 to control the scan driver 103. In addition, the timing control section 106 supplies the digital data signal supplied from the external system to the data driver 104.

The pixels 101 receive a data signal from the data line DL when a scan pulse is supplied to the scan line SL, and generate light corresponding to the data signal.

The reference voltage unit 110 may set the reference voltage to be applied, which is the organic light emitting diode panel 102, and apply the set reference voltage to each pixel 101. [

The sensing unit 111 senses the threshold voltage of the transistor in each pixel 101 and applies a compensation signal to the organic light emitting diode panel 102 using the sensed data, So that high luminance can be realized.

As described above, the sensing unit 111 senses the threshold voltage of each pixel 101, sets a reference voltage in the reference voltage unit 110, and outputs a reference voltage on the organic light emitting diode panel 102 can do.

In order to set the reference voltage as described above, the dispersion of the initial threshold voltage (Vth) of the driving transistor is used, and the threshold voltage (Vth) of the driving transistor may vary depending on the size of the driving transistor.

The threshold voltage of the driving transistor can be expressed by the following equation (1).

---(1)

---(One)

는 메탈(Metal)과 반도체(Semiconductor)의 일함수 전위차이고,

는 산화막 표면에서의 고정전하이고,

는 이온층에서의 양전하이고,

는 게이트의 단위 면적당 커패시턴스(capacitance)이며,

는 Ei(intrinsic level)와 Ef(fermi level)의 차이의 크기이다.In the above equation (1)

Is a work function potential difference between a metal and a semiconductor,

Is a fixed charge on the oxide film surface,

Is a positive charge in the ion layer,

Is a capacitance per unit area of the gate,

Is the magnitude of the difference between Ei (intrinsic level) and Ef (fermi level).

는 다음 수학식(2)를 충족할 수 있다.In the mathematical expression (1), the capacitance per unit area of the gate

Can satisfy the following equation (2).

---(2)

---(2)

는 자유공간 유전율(permittivity of free space)이고,

은 비유전율(relative dielectric constant)이며,

는 산화막 두께(Oxide thickness)이다.In the above equation (2)

Is the permittivity of free space,

Is a relative dielectric constant,

Is an oxide thickness.

According to Equations (1) and (2), it can be seen that the threshold voltage Vth can be varied according to the size and dielectric constant of the gate of the driving transistor.

The size of the driving transistor of the R sub pixel is approximately 142 mu m, the size of the driving transistor of the G sub pixel is approximately 122 mu, the size of the driving transistor of the B sub pixel is approximately 145 mu, The size of the driving transistor of the organic EL element can be approximately 82 (um). As described above, the size of the driving transistor of the W sub-pixel is smaller than that of the driving transistor of the R G B sub-pixel. The reason why the size of the driving transistor of the W sub-pixel is small is because the light emitting efficiency is good compared with other pixels and there is no separate color filter.

Since the size of the driving transistor of the W sub-pixel is small, the threshold voltage of the driving transistor of the W sub-pixel may be higher than the threshold voltage of the driving transistor of the RGB sub-pixel.

Fig. 3 shows the distribution of the threshold voltages of R, G and B sub-pixels and W sub-pixels.

Referring to FIG. 3, it can be seen that the scattering tendency of the threshold voltages of the R, G, and B sub-pixels and the scattering tendency of the threshold voltage of the W sub-pixel are plotted.

Threshold voltages of R, G and B subpixels are similar to each other, but the dispersion of the threshold voltage of W subpixels is slightly higher than that of R, G and B subpixels .

That is, since the driving transistor of the W sub-pixel is smaller than the size of the driving transistor of the RGB sub-pixel, the scattering of the threshold voltage is higher.

Therefore, each of the threshold voltages of the driving transistors of the R, G, and B sub-pixels and the threshold voltage of the driving transistor of the W sub-pixel are individually sensed and the individual reference voltages to be supplied to the sub-pixels are set based on the sensed threshold voltages. For example.

Hereinafter, an organic light emitting diode display device 100 for supplying a reference voltage to the R, G and B sub-pixels and w sub-pixels will be described.

4 is a block diagram illustrating a sensing unit of an organic light emitting diode display according to an exemplary embodiment of the present invention.

4, the organic light emitting diode display according to the present invention includes a reference voltage unit 110 including a reference voltage setting unit 220 and a reference voltage supply unit 330, a sensing unit 111, (Not shown).

The reference voltage setting unit 220 sets the reference voltage for the driving transistors of the R, G, and B sub-pixels using the threshold voltage information for the driving transistor of each pixel obtained through the sensing transistor on the organic light emitting diode panel 102, And a second reference voltage for the driving transistor of the W sub-pixel.

The first and second reference voltages set in the reference voltage setting unit 220 may be supplied to the pixels 101 from the reference voltage supply unit 330. The first reference voltage may be supplied to each of the R, G, and B sub-pixels, and the second reference voltage may be supplied to the W sub-pixel. In this manner, R (Red), G (Green), and B (Blue) sub pixels and W (White) sub pixels are individually connected to two reference voltage lines 1 and the second reference voltage line, the reference voltages of the R, G, and B sub-pixels and the W sub-pixel can be optimized, thereby achieving the optimal luminance. have.

5 is a diagram illustrating a structure of a reference voltage supply unit and pixels of an organic light emitting diode display device 100 according to an embodiment of the present invention.

A specific structure of the reference voltage supplier 330 and the pixels 101 of the organic light emitting diode display 100 according to the embodiment of the present invention will be described.

On the organic light emitting diode panel 102, R, G, B and W sub-pixels are formed.

A first driving transistor T1, a first scan transistor T2, a first sensing transistor T3, a first storage capacitor C1, and a first organic light emitting diode device D1 may be included on the R sub-pixel .

A first organic light emitting diode device D1 may be connected between the node 1 N1 and the low potential power supply Vss and between the high potential power supply Vdd and the first node N1 and the second node N2, 1 driving transistor T1 may be connected. The source terminal of the first driving transistor Tl is connected to the node 1 N1 and the gate terminal of the first driving transistor Tl is connected to the node 2 N2 and the drain of the first driving transistor Tl The terminal may be connected to a high potential power supply (VDD).

A first scan transistor T2 may be connected between the node N2 and the data line DL and the scan line SL.

A first storage capacitor C1 may be connected between the node 1 (N1) and the node 2 (N2).

The first sensing transistor T3 may be connected to the sensing unit 111 through a gate terminal to be controlled by a sensing signal of the sensing unit 111 and may be connected between the node N2 and the node N3.

Although the R sub-pixel has been described above, the structure may be applied to the G and B sub-pixels as well.

On the other hand, the scan transistor T2 may be turned on by a scan pulse supplied from the gate line, and the drive transistor T1 may be controlled by the voltage of the node 2 (N2).

The capacitor C1 may be charged by a potential difference between node 1 (N1) and node 2 (N2).

A second driving transistor T4, a second scan transistor T5, a second sensing transistor T6, a second storage capacitor C2, and a second organic light emitting diode D2 may be included on the W sub-pixel .

The second organic light emitting diode D2 may be connected between the node N4 and the low potential power supply Vss and between the high potential power supply Vdd and the node N4 and the node N5, 2 driving transistor T4 may be connected. The source terminal of the second driving transistor T4 is connected to the node 4 (N4), the gate terminal of the second driving transistor T4 is connected to the node 5 (N5), the drain of the second driving transistor T4 The terminal may be connected to a high potential power supply (VDD).

A second scan transistor T5 may be connected between the node N5 and the data line DL and the scan line SL.

A second storage capacitor C2 may be connected between node 4 (N4) and node 5 (N5).

The second sensing transistor T6 may be connected between the node N4 and the node N6 such that the gate terminal is connected to the sensing unit 111 and the node N4 is controlled by the sensing unit 111. [

On the other hand, the second scan transistor T5 may be turned on by a scan pulse supplied from the gate line, and the second drive transistor T4 may be controlled by the voltage of the fifth node N5.

The second storage capacitor C2 may be charged by a potential difference between nodes 4 (N4) and 5 (N5).

The reference voltage supplier 330 may include a main reference voltage line MRVL and first and second sub reference voltage lines SRVL1 and SRVL2. The main reference voltage line MRVL supplies a reference voltage to the first and second sub reference voltage lines SRVL1 and SRVL2, respectively. The reference voltage may be transmitted to the first and second sub reference voltage lines SRVL1 and SRVL2 at the different time points.

The reference voltage supplier 330 includes a first switching device S1 connected between the main reference voltage line MRVL and the first sub reference voltage line SRVL1, And a second switching element S2 connected between the second sub reference voltage line SRVL2 and the second sub reference voltage line SRVL2.

The first switching element S1 is connected between the main reference voltage line MRVL and the sixth node N6 to enable conduction between the main reference voltage line MRVL and the sixth node N6 in accordance with the switching operation. have. The second switching element S2 is connected between the main reference voltage line MRVL and the third node N3 and is opened or closed between the main reference voltage line MRVL and the third node N3 according to the switching operation. Can be short-circuited.

Although the specific circuit structure of the reference voltage supply unit 330 is described above, it can be implemented using a demultiplexer. That is, the input line applied to the demultiplexer becomes the main reference voltage line MRVL, and the output line output to the demultiplexer can be the first and second sub reference voltage lines SRVL1 and SRVL2.

It may also be a multiplexer or a bi-directional multiplexer instead of the demultiplexer.

The first and second sub reference voltage lines SRVL1 and SRVL2 connected to the main reference voltage line MRVL and the main reference voltage line MRVL, The first and second switching elements S1 and S2 that control the electrical connection of the two sub reference voltage lines SRVL1 and SRVL2 can be used to supply the respective reference voltages to the R, G, and B sub pixels and w sub pixels , The sub reference voltage lines SRVL1, SRVL2 (SRVL2, SRVL2, SRVL2, SRVL2, SRVL2, SRVL2, SRVL2, And the switching elements S1 and S2 can be used.

The embodiment of the present invention optimizes the reference voltage by setting the reference voltage for each pixel differently instead of the R / G / B / W sub-pixels sharing the reference voltages. In order to set the reference voltage, There is a case in which the initial threshold voltage is scattered and the initial threshold voltage of each driving transistor is slightly different from the threshold voltage for each pixel. In this case, a reference voltage line is provided for each pixel and a separate reference voltage can be individually set for each pixel So that an optimal luminance can be realized.

On the other hand, when the reference voltage line is increased to provide the reference voltage for each pixel, the size of the drive chip may increase. Therefore, the demultiplex introduced in the embodiment of the present invention can be used to increase the size of the drive chip The reference voltage can be individually supplied and thus the optimum luminance can be realized.

Hereinafter, the threshold voltage compensation method of the present invention will be described in detail with reference to a circuit diagram and a waveform diagram.

FIGS. 6 to 8 are views showing pixels of any one of R, G, B, and W according to the embodiment of the present invention, and FIG. 9 is a waveform diagram for explaining threshold voltage compensation.

Referring to FIGS. 6 and 9, the threshold voltage compensation may include an initialization period (Tinitial), a sensing period (Tsensing), and a sampling period (Tsampling).

For convenience of explanation, R pixels among RGBW pixels will be described, and the same description can be applied to the remaining pixels.

<Initialization period: Tinit>

6 and 9, the scan transistor T2 is turned on by the high level scan signal on the scan line SL in the initialization period (Tinit), and the scan transistor T2 is turned on by the sensing signal of the sensing unit 111, The transistor T3 is turned on.

When the scan transistor T2 is turned on, the data voltage Vdata is applied to the data line DL and the node 2 is charged to the data voltage Vdata. When the sensing transistor T3 is turned on, an initializing voltage Vinit is applied to the reference voltage line RVL to charge the node N1 to the initializing voltage Vinit. In this case, the data voltage Vdata may be a predetermined data voltage to compensate for a threshold voltage, not a data voltage for the organic light emitting diode D1 to emit light. The initialization voltage Vinit may be set lower than the low potential power supply Vss or the low potential power supply Vss may be set higher than the initialization voltage Vinit to prevent the organic light emitting diode device D1 from emitting light have.

At this time, the gate-source voltage of the driving transistor Tl is larger than the threshold voltage Vth of the driving transistor Tl. Therefore, the driving transistor Tl is turned on, and the current flowing in the driving transistor Tl as a source follower has an appropriate initialization value.

The source follower method connects the compensation capacitor C1 between the gate and source electrodes of the driving transistor T1 and follows the source voltage of the driving transistor T1 to the gate voltage when the threshold voltage Vth of the driving transistor T1 is detected. . Further, since the drain electrode of the driving transistor Tl is separated from the gate electrode and is supplied with the power supply voltage from the high potential power supply (VDD), the source follower method has not only a threshold voltage having a positive value but also a threshold voltage Can be detected.

<Sensing period: Tsen>

7 and 9 illustrate pixel operation during the sensing period Tsen.

During the sensing period Tsen the scan transistor T2 is still on and the sensing transistor T3 is still on. However, the initialization voltage (Vinit) is no longer supplied to the node 1 (N1) through the reference voltage line (RVL).

7 and 9, when the voltage supply on the reference voltage line RVL is cut off in the sensing period Tsen to make the node 1 N1 floating, the current flowing through the driving transistor Tl The voltage of the node 1 (N1) can rise.

에 이르는 경우, 즉 구동 트랜지스터(T1)의 문턱 전압(Vth)에 이르는 경우 상기 구동 트랜지스터(T1)에 흐르는 전류는 0이되므로 노드1(N1)의 전압은

로 일정하게 유지하게 된다.The voltage of the node 1 N1 rises and the voltage of the node 1 N1 due to the voltage difference between the node 1 N1 and the node 2 N2 due to the threshold voltage Vth of the driving transistor Tl. this

That is, the threshold voltage Vth of the driving transistor T1, the current flowing through the driving transistor T1 becomes zero, so that the voltage of the node 1 (N1)

.

<Sampling period: Tsam>

Figs. 7 and 9 are diagrams for explaining pixel operation in the sampling period Tsam.

During the sampling period Tsam, the scan transistor T2 is still on and the sensing transistor T3 is still on.

가 기준 전압 라인(RVL)을 통해서 검출된다.7 and 9, in the sampling period Tsam, the source terminal of the driving transistor T1, that is, the voltage on the node 1 (N1)

Is detected through the reference voltage line RVL.

That is, the threshold voltage Vth of the driving transistor Tl can be detected using the difference between the Vdata voltage applied to the node N2 and the source voltage detected at the node 1 (N1).

&Lt; Light emission period &

8 is a diagram showing the pixel operation in the light emission period.

Referring to FIG. 8, in the light emission step, the scan transistor T2 may be turned on and the sensing transistor T3 may be turned on.

가 노드2(N2)로 인가된다. 그리고 상기 센싱 트랜지스터(T3)가 턴온되고 기준 전압 라인(RVL)을 통해 레퍼런스 전압(Vref)이 노드1(N1)로 인가된다.When the scan transistor T2 is turned on and the data line DL is compensated

Is applied to the node 2 (N2). The sensing transistor T3 is turned on and the reference voltage Vref is applied to the node 1 through the reference voltage line RVL.

A current flows to the driving transistor Tl by a potential difference between the node 2 and the node 1 and the current flows to the organic light emitting diode D1.

The above expression can be expressed by the following equation.

는 구동 트랜지스터(T1)의 이동도 및 기생용량에 의해 결정되는 상수값을 각각 의미한다.Here, 'Vgs' is the difference voltage between the gate voltage Vg and the source voltage Vs of the driving transistor T1, 'Vdata' is the data voltage, 'Vinit' is the initialization voltage, 'Ioled''Vth' is the threshold voltage of the driving transistor Tl,

Denotes a constant value determined by the mobility of the driving transistor T 1 and the parasitic capacitance, respectively.

As described above, it can be seen that the current Ioled of the organic light emitting diode device D1 is greatly affected by the threshold voltage Vth of the driving transistor Tl.

When the voltage applied to the node 2 (N2) is Vdata + Vth through the compensation of the threshold voltage Vth as described above, the current flowing through the organic light emitting diode D1 can be expressed by the following equation.

를 인가하는 경우, 유기발광다이오드소자(D1)에 흐르는 전류는 구동 트랜지스터(T1)의 문턱 전압에 영향을 받지 않고, 데이터 전압(Vdata)와 기준 전압(Vref)에만 의존하도록 할 수 있다.That is, the node 2 (N2)

The current flowing through the organic light emitting diode D1 can be made to depend only on the data voltage Vdata and the reference voltage Vref without being influenced by the threshold voltage of the driving transistor Tl.

&Lt; Reference voltage setting step &

Referring to FIG. 9, it can be seen that the dispersion of the threshold voltage differs for each pixel. That is, the dispersion of the W pixel tends to be shifted to the right rather than the dispersion of the threshold voltage for the RGB pixels.

Although the RGB pixels and the W pixels are shown in the drawings, the threshold voltage distributions of the R, G, B, and W pixels may differ. However, in order to compensate for each of these differences, there is a problem that the wiring increases and the area of the driver IC becomes larger, and the difference between the threshold voltage of the RGB pixel and the threshold voltage of the W pixel becomes the most noticeable, It is preferable to set the reference voltage by dividing the pixels.

Hereinafter, a method of setting the reference voltage will be described.

When the threshold voltage Vth of each pixel detected in the sampling step Tsam for compensating the threshold voltage is analyzed and analyzed, the minimum value Min and the maximum value Max are divided and distributed based on the average value Typ in FIG. 3 . That is, the threshold voltage of the driving transistor of all the pixels is measured and analyzed by data analysis to set the reference voltage Vref.

For example, two reference values Ref1 and Ref2 are defined for the threshold voltages of the scattered driving transistors. These reference values Ref1 and Ref2 can be divided into reference values Ref1 (RGB) and Ref2 (RGB) for the driving transistors of RGB and reference values Ref1 (W) and Ref2 (W) for the driving transistor of W . On the other hand, the criterion for distinguishing Ref1 from Ref2 can be selectively used according to the channel type (N channel or P channel) of the driving transistor. That is, the threshold voltage of the driving transistor can be selectively used depending on whether it has a positive value or a negative value.

The reference voltage Vref for the RGB pixel and the reference voltage Vref for the W pixel corresponding to the reference values Ref1 and Ref2 are set and are supplied to the organic light emitting diode device through the sub reference voltage lines SRVL1 and SRVL2 during the light emitting period, As shown in FIG.

가 된다. 이때 제시된 식에서 기준전압(Vref)은 해당 화소의 문턱전압의 산포도로부터 결정된 값이므로, 문턱 전압의 편차가 보정된 전류가 유기발광다이오드소자에 흐르게 된다.The current flowing in the organic light emitting diode element during the light emission period is approximately

. In this case, the reference voltage Vref is a value determined from the dispersion of the threshold voltage of the pixel, so that the current with the deviation of the threshold voltage corrected flows to the organic light emitting diode device.

10 is a circuit diagram of R pixels and W pixels among RGB pixels according to an embodiment of the present invention, and FIGS. 11 to 13 are diagrams showing waveforms applied to the circuit diagram of FIG.

10 and 11, the SREF switch, the SAM switch, the second scan transistor T5, the second sensing transistor T6, and the first switch S1 (S1) are turned on during the initialization period (Tinit) Is turned on, the Vdata voltage is applied to the node 5 (N5), and the initialization voltage (Vinit) is applied to the node 4 (N4).

As the SREF switch and the SAM switch are turned off during the sensing period Tsen, the voltage of the node 4 (N4) rises according to the floating state, and the SAM switch is turned on during the sampling period Tsam, Can be detected. The difference voltage between the detected voltage Vdata-Vth and the Vdata applied to the node 5 (N5) becomes the threshold voltage Vth of the second driving transistor T4.

The detected voltage may be applied to an analog-to-digital converter (ADC) to be digitized.

10 and 12, the SREF switch, the SAM switch, the first scan transistor T2, the first sensing transistor T3, and the second switch (T3) are turned on during the initialization period (Tinit) S2 are turned on, the Vdata voltage is applied to the node 2 (N2), and the initialization voltage (Vinit) is applied to the node 1 (N1).

As the SREF switch and the SAM switch are turned off during the sensing period Tsen, the voltage of the node 1 (N1) rises according to the floating state, and the SAM switch is turned on during the sampling period (Tsam) Can be detected. The difference voltage between the detected voltage and Vdata applied to the node 2 (N2) becomes the threshold voltage (Vth) of the first driving transistor T1.

The detected voltage may be applied to an analog-to-digital converter (ADC) to be digitized. That is, the analog to digital converter (ADC) converts the detected voltage into a digital value and stores information on the threshold voltage (Vth) in a memory (not shown). The analog digital converter (ADC) and the memory may be included in the sensing unit 111 of FIG.

The sensing unit 111 detects a threshold voltage Vth and provides the reference voltage to the reference voltage setting unit 220.

The reference voltage setting unit 220 divides the threshold voltage for the RGB pixel and the threshold voltage for the W pixel, analyzes the dispersion of the threshold voltage described in FIG. 3, and controls the driving transistor for the RGB according to the dispersion of the threshold voltage (Ref1 (W) or Ref2 (W)) for the driving transistor of W and the reference value (Ref1 (RGB) or Ref2 The reference voltage setting unit 220 provides information on the determined reference value to the reference voltage supplying unit 330.

The reference voltage supplier 330 generates a reference voltage Vref corresponding to the reference value based on information on the reference value from the reference voltage setting unit 220 to drive the source electrode and the W pixel of the driving transistor of the RGB pixel To the source electrode of the transistor.

At this time, the current flowing from the drain terminal to the source terminal of the driving transistor is determined according to the potential difference between the data voltage supplied to the gate terminal of the driving transistor and the reference voltage (Vref) supplied to the source terminal of the driving transistor, The degree of emission of the organic light emitting diode can be controlled.

Meanwhile, the reference voltage supplier 330 may include a memory having a database in which a reference voltage Vref corresponding to a reference value is tabulated.

Referring to FIGS. 10 and 13, the first switch S1 and the SREF switch are turned on for a certain period of the light emission period, and the reference value Ref1 (W) or Ref2 (W) is applied to the node 4 (N4) (RGB) or Ref2 (RGB) is applied to the node 1 (N1) of the RGB pixel by turning on the second switch S2 and the SREF switch for the remaining part of the period, The reference voltage Vref corresponding to the reference voltage Vref can be applied.

The threshold voltage of each pixel can be compensated by dividing the RGB pixel and the W pixel and supplying a proper reference voltage to each pixel to compensate for the deviation of the threshold voltage for each pixel of the pixel, And the luminance of the W pixel can be optimized. Further, in order to optimize the brightness of each pixel, it is not necessary to provide a separate driving driver by using the main reference voltage line MRVL and the sub reference voltage lines SRVL1 and SRVL2. Therefore, it is possible to prevent the increase of the complexity of the driving driver and the increase of the area.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

100. Organic Light Emitting Diode Display
101. Pixels
102. Organic Light Emitting Diode Panel
103. The scan driver
104. Data Drivers
105. A gamma voltage generator
106. Timing controller
107. Power supply
108. Feed pad
109. Base Pad
110. Reference voltage section
111. Sensing unit
220. Reference voltage setting section
330. A reference voltage supply

Claims (20)

An organic light emitting diode that emits light by a current adjusted in accordance with a potential difference between a gate and a source terminal of the driving transistor and a source terminal of the driving transistor, A plurality of red (R), green (G), blue (B) and white (W) pixels including a sensing transistor for supplying any one of them,
The first reference voltage is determined according to a threshold voltage of the driving transistors of the R, G, and B pixels and is supplied to the source terminals of the driving transistors of the R, G, and B pixels,
Wherein the second reference voltage is determined according to a threshold voltage of the driving transistor of the W pixel and supplied to a source terminal of the driving transistor of the W pixel. The method according to claim 1,
Each of the pixels
Further comprising a scan transistor controlled by a scan signal on a gate line and supplying a data voltage on a data line to a gate terminal of the drive transistor,
Supplying a data voltage to a gate terminal of the driving transistor and an initialization voltage to a source terminal of the driving transistor during an initialization period,
Varying the voltage on the source terminal of the driving transistor during a sensing period,
Sensing a voltage on a source terminal of the driving transistor during a sampling period to detect a threshold voltage of the driving transistor,
And supplies the first and second reference voltages to a source terminal of the driving transistor during a light emission period. 3. The method of claim 2,
The sensing transistors of the R, G and B pixels share a first sub reference voltage line,
And the sensing transistors of the W pixel are connected to the second sub reference voltage line. The method of claim 3,
And the sensing transistor supplies a voltage on the sub reference voltage line to a source terminal of the driving transistor in response to a sensing signal. 5. The method of claim 4,
Supplying an initializing voltage on the sub reference voltage line to the source terminal of the driving transistor during the initialization period,
And a source terminal of the driving transistor is floated during the sensing period. 6. The method of claim 5,
And a sensing unit sensing a voltage on a source terminal of the driving transistor and detecting a threshold voltage of the driving transistor from a sensed voltage. The method according to claim 6,
The threshold voltage detected from the sensing unit is set to the first and second reference voltages based on a dispersion of the R, G, and B pixels with respect to the threshold voltage of the driving transistor and a dispersion of the threshold voltage of the driving transistor of the W pixel And a reference voltage unit. 8. The method of claim 7,
A main reference voltage line for supplying the first and second reference voltages provided from the reference voltage section to the first and second sub reference voltage lines;
And a switching device for selectively connecting the main reference voltage line and the first and second sub reference voltage lines. 9. The method of claim 8,
The switching device includes:
A first switching element for controlling an electrical connection between the main reference voltage line and the first sub reference voltage line and a second switching element for controlling an electrical connection between the main reference voltage line and the second sub reference voltage line, Organic light emitting diode display. 8. The method of claim 7,
A main reference voltage line for supplying the first and second reference voltages provided from the reference voltage section to the first and second sub reference voltage lines; And
A demultiplexer for selectively connecting any one of the first and second sub reference voltage lines to the main reference voltage line; Further comprising an organic light emitting diode display device. An organic light emitting diode (OLED) connected to the driving transistor and adapted to emit light according to a current controlled by the driving transistor; And a sensing transistor for sensing a threshold voltage of the driving transistor and supplying either one of a first reference voltage and a second reference voltage to a connection terminal of the organic light emitting diode and the driving transistor, And a second pixel for displaying a second color different from the first color,
Wherein the first reference voltage is determined according to a threshold voltage of the driving transistor of the first pixel,
Wherein the second reference voltage is determined according to a threshold voltage of the driving transistor of the second pixel. 12. The method of claim 11,
Wherein each of the first and second pixels comprises:
Further comprising a scan transistor controlled by a scan signal on a gate line and supplying a data voltage on a data line to a gate terminal of the drive transistor,
Supplying a data voltage to a gate terminal of the driving transistor and an initialization voltage to a source terminal of the driving transistor during an initialization period,
Varying the voltage on the source terminal of the driving transistor during a sensing period,
Sensing a voltage on a source terminal of the driving transistor during a sampling period to detect a threshold voltage of the driving transistor,
And supplies the first and second reference voltages to a source terminal of the driving transistor during a light emission period. 13. The method of claim 12,
The sensing transistors of the first pixel share a first sub-reference voltage line,
And the sensing transistors of the second pixel are connected to the second sub reference voltage line. 14. The method of claim 13,
And the sensing transistor supplies a voltage on the sub reference voltage line to a source terminal of the driving transistor in response to a sensing signal. 15. The method of claim 14,
Supplying an initializing voltage on the sub reference voltage line to the source terminal of the driving transistor during the initialization period,
And a source terminal of the driving transistor is floated during the sensing period. 16. The method of claim 15,
And a sensing unit sensing a voltage on a source terminal of the driving transistor and detecting a threshold voltage of the driving transistor from a sensed voltage. 17. The method of claim 16,
A threshold voltage detected from the sensing unit is set to a reference voltage for setting the first and second reference voltages from the dispersion of the threshold voltage of the driving transistor of the first pixel and the dispersion of the threshold voltage of the driving transistor of the second pixel, And an organic light emitting diode (OLED) display unit. 18. The method of claim 17,
A main reference voltage line for supplying the first and second reference voltages provided from the reference voltage section to the first and second sub reference voltage lines;
And a switching device for selectively connecting the main reference voltage line and the first and second sub reference voltage lines. 19. The method of claim 18,
The switching device includes:
A first switching element for controlling an electrical connection between the main reference voltage line and the first sub reference voltage line and a second switching element for controlling an electrical connection between the main reference voltage line and the second sub reference voltage line The organic light emitting diode display device. 18. The method of claim 17,
A main reference voltage line for supplying the first and second reference voltages provided from the reference voltage section to the first and second sub reference voltage lines; And
A demultiplexer for selectively connecting any one of the first and second sub reference voltage lines to the main reference voltage line; Further comprising an organic light emitting diode display device.

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