KR102627269B1 - Organic Light Emitting Display having a Compensation Circuit for Driving Characteristic - Google Patents

Abstract

The organic light emitting diode display device according to the present invention includes a driving transistor, a light emission control transistor, and a driving characteristic compensation circuit. The gate electrode of the driving transistor is connected to a first node that receives the data voltage, the source electrode is connected to the input terminal of the high potential driving voltage, and the drain electrode is connected to the second node connected to the anode electrode of the organic light emitting diode. The light emission control transistor controls the current path between the second node and the organic light emitting diode. The driving characteristics compensation circuit receives feedback from the sensing voltage of the second node reflecting the threshold voltage of the driving transistor, compares it with the data voltage, and provides a constant output voltage to the first node when the sensing voltage and the data voltage are the same.

Description

Organic Light Emitting Display having a Compensation Circuit for Driving Characteristic}

The present invention relates to an active matrix type organic light emitting display device, and particularly to an organic light emitting display device having a driving characteristic compensation circuit.

The active matrix type organic light emitting display device includes an organic light emitting diode (OLED) that emits light on its own, and has the advantages of fast response speed, high luminous efficiency, brightness, and viewing angle.

Organic light-emitting diodes, which are self-luminous devices, include an anode electrode and a cathode electrode, and an organic compound layer (HIL, HTL, EML, ETL, EIL) formed between them. The organic compound layer includes a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and an electron injection layer. EIL). When a driving voltage is applied to the anode and cathode electrodes, holes passing through the hole transport layer (HTL) and electrons passing through the electron transport layer (ETL) are moved to the emitting layer (EML) to form excitons, and as a result, the emitting layer (EML) Visible light is generated.

Each pixel of an organic light emitting display device includes a driving transistor (thin film transistor) to control the driving current flowing through the organic light emitting diode. It is desirable that the electrical characteristics of the driving transistor, such as threshold voltage and mobility, are designed to be the same for all pixels, but in reality, the electrical characteristics of the driving transistor for each pixel are non-uniform due to process conditions, driving environment, etc. For this reason, the driving current according to the same data voltage varies for each pixel, resulting in a luminance difference between pixels. To solve this problem, an image quality compensation technology is known that reduces luminance unevenness by sensing the characteristic parameters (threshold voltage, mobility) of the driving transistor from each pixel and appropriately correcting the input data according to the sensing results.

Image quality compensation technology includes external compensation methods and internal compensation methods. The external compensation method directly obtains the sensing voltage after operating the driving transistor, converts it into digital data, and compensates the image data using the compensation value determined accordingly. The external compensation method not only requires an analog-to-digital converter to convert the sensing voltage into digital data, but also has the disadvantage of not being able to compensate in real time.

The internal compensation method compensates using the driving current passing through the driving transistor regardless of the size of the threshold voltage of the driving transistor, and real-time compensation is possible. However, applying the internal compensation method requires a large number of transistors in the pixel, which has the disadvantage of complicating the circuit and reducing the aperture ratio.

The present invention is intended to provide an organic light emitting display coating capable of real-time compensation while simplifying the circuit.

The organic light emitting diode display device according to the present invention includes a driving transistor, a light emission control transistor, and a driving characteristic compensation circuit. The gate electrode of the driving transistor is connected to a first node that receives the data voltage, the source electrode is connected to the input terminal of the high potential driving voltage, and the drain electrode is connected to the second node connected to the anode electrode of the organic light emitting diode. The light emission control transistor controls the current path between the second node and the organic light emitting diode. The driving characteristics compensation circuit receives feedback from the sensing voltage of the second node reflecting the threshold voltage of the driving transistor, compares it with the data voltage, and provides a constant output voltage to the first node when the sensing voltage and the data voltage are the same.

Since the present invention does not require an analog-to-digital converter to convert the sensing voltage into digital data, the size of the driving circuit can be significantly reduced.

Additionally, the present invention can perform real-time compensation without requiring a large number of transistors as in a general internal compensation circuit. Since the present invention does not require a large number of transistors in the pixel circuit, the aperture ratio can be increased and high brightness can be displayed.

1 is a diagram showing an organic light emitting display device according to an embodiment of the present invention.
Figure 2 is a diagram showing a pixel circuit and a driving characteristic compensation circuit according to the first embodiment.
Figure 3 shows a driving signal for driving a pixel according to the present invention.
Figures 4 and 5 are diagrams explaining pixel driving.
Figure 6 is a diagram showing a pixel circuit and a driving characteristic compensation circuit according to a second embodiment.
Figure 7 is a diagram showing a pixel circuit and a driving characteristic compensation circuit according to a third embodiment.
Figure 8 is a diagram showing a pixel circuit and a driving characteristic compensation circuit according to the fourth embodiment.
Figure 9 is a diagram showing a pixel circuit and a driving characteristic compensation circuit according to the fifth embodiment.
Figure 10 is a diagram showing a pixel circuit and a driving characteristic compensation circuit according to the sixth embodiment.
Figure 11 is a diagram showing a pixel circuit and a driving characteristic compensation circuit according to the seventh embodiment.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the attached drawings. Like reference numerals refer to substantially the same elements throughout the specification. In the following description, if it is determined that a detailed description of a known function or configuration related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

In an embodiment of the present invention, switch elements may be implemented as transistors with an n-type or p-type MOSFET (Metal Oxide Semiconductor Field Effect Transistor) structure. Although the following embodiments have been described focusing on a p-type transistor, it should be noted that the present invention is not limited thereto. A transistor is a three-electrode device including a gate, source, and drain. The source is an electrode that supplies carriers to the transistor. Within the transistor, carriers begin to flow from the source. The drain is the electrode through which carriers exit the transistor. That is, the flow of carriers in the MOSFET flows from the source to the drain. In the case of an n-type MOSFET (NMOS), because the carriers are electrons, the source voltage has a lower voltage than the drain voltage so that electrons can flow from the source to the drain. In an n-type MOSFET, since electrons flow from the source to the drain, the direction of current flows from the drain to the source. In the case of a p-type MOSFET (PMOS), since the carrier is a hole, the source voltage is higher than the drain voltage to allow holes to flow from the source to the drain. In a p-type MOSFET, current flows from the source to the drain because holes flow from the source to the drain. It should be noted that the source and drain of the MOSFET are not fixed. For example, the source and drain of a MOSFET can change depending on the applied voltage. The invention should not be limited by the source and drain of the transistor in the following embodiments.

1 is a diagram showing an organic light emitting display device according to an embodiment of the present invention. FIG. 2 shows a pixel array formed on the display panel of FIG. 1.

Referring to FIG. 1, an organic light emitting display device according to an embodiment of the present invention includes a display panel 100 on which pixels P are formed, and a data driver for driving data lines DL1 to DLn (n is a natural number). (400), a gate driver 300 for driving the gate lines GL1 to GLm (m is a natural number), and a timing controller for controlling the driving timing of the data driver 400 and the gate driver 300 ( 200).

The display panel 100 includes a display area (AA) where pixels (P) are arranged to display an image, and a non-display area (NAA) where the image is not displayed. The display area (AA) may be referred to as a pixel array, and the non-display area (NAA) may be referred to as a bezel surrounding the display area (AA).

In the display area (AA) of the display panel 100, a plurality of data lines (DL1 to DLn) and a plurality of gate lines (GL1 to GLm) intersect, and pixels (P) are arranged in a matrix form in each intersection area. do. Each pixel line HL1 to HLm includes pixels arranged in the same row. Hereinafter, in this specification, the X direction shown in FIG. 1 will be referred to as the row direction, and the Y direction will be referred to as the column direction. When there are mХn pixels P arranged in the display area AA, the display area AA includes m pixel lines.

Pixels P placed on the first pixel line HL1 are connected to the first gate line GL1, and pixels P placed on the nth pixel line HLm are connected to the mth gate line GLm. do. Gate lines GL1 to GLm may include multiple lines providing respective gate signals.

The transistors constituting the pixels P may be implemented as oxide transistors including an oxide semiconductor layer. Oxide transistors are advantageous for increasing the area of the display panel 100 when considering electron mobility, process deviation, etc. However, the present invention is not limited to this, and the semiconductor layer of the transistor may be formed of amorphous silicon, polysilicon, etc.

The timing controller 200 controls the operation timing of the data driver 400 based on timing signals such as the vertical synchronization signal (Vsync), the horizontal synchronization signal (Hsync), the dot clock signal (DCLK), and the data enable signal (DE). A data control signal for controlling and a clock signal (MCLK) for controlling the operation timing of the gate driver 300 are generated.

The gate driver 300 may generate gate signals based on the clock signal (MCLK). This gate driver 300 may be formed directly on the non-display area (NAA) of the display panel 100 according to the gate-driver in panel (GIP) method.

The data driver 400 converts the image data (DATA) input from the timing controller 200 into an analog data voltage based on the data control signal (DDC). Specific examples of the data driver 400 will be described later.

Figure 2 is a diagram showing a pixel circuit and a driving characteristic compensation circuit according to the first embodiment.

Referring to FIG. 2, the pixel (P) according to the first embodiment includes an organic light emitting diode (OLED), a driving transistor (DT), a storage capacitor (Cst), first and second transistors (T1, T2), and a light emission control unit. It includes a transistor T3 (hereinafter referred to as a third transistor).

The organic light emitting diode (OLED) includes an anode electrode connected to the drain electrode of the third transistor (T3) and a cathode electrode connected to the input terminal of the low potential driving voltage (EVSS).

The driving transistor DT includes a gate electrode connected to the first node N1, a source electrode connected to the input terminal of the high potential driving voltage EVDD, and a drain electrode connected to the second node N2. The driving transistor (DT) controls the driving current (Ioled) flowing through the organic light-emitting diode (OLED) according to the voltage (Vsg) between the source and gate.

The storage capacitor Cst is connected between the first node N1 and the second node N2 to store the voltage between the source and gate of the driving transistor DT in the sensing and data period.

The first transistor T1 includes a gate electrode connected to the scan line SCL, a source electrode connected to the output terminal of the amplifier 501, and a drain electrode connected to the first node N1. The first transistor T1 responds to the scan signal SCAN and applies the output voltage Vout of the amplifier 501, which reflects the data voltage Vdata, to the first node N1 during the sensing and data writing period.

The second transistor T2 includes a gate electrode connected to the scan line SCL, a source electrode connected to the second node N2, and a drain electrode connected to the pull-down circuit unit 500. The second transistor T2 connects the second node N2 and the voltage detection node VN in response to the scan signal SCAN during the sensing and data writing period.

The third transistor T3 includes a gate electrode connected to the emission line EML, a source electrode connected to the second node N2, and a drain electrode connected to the anode of the organic light emitting diode (OLED). The third transistor T3 connects the second node N2 and the anode electrode of the organic light emitting diode (OLED) during the light emission period.

The driving characteristics compensation circuit 500 receives feedback from the sensing voltage (Vsen) of the second node (N2) reflecting the threshold voltage of the driving transistor (DT) and compares it with the data voltage. And the driving characteristics compensation circuit 500 adjusts the output voltage (Vout) applied to the first node (N1) until the sensing voltage (Vsen) and the data voltage (Vdata) are at the same level.

For this purpose, the driving characteristics compensation circuit 500 includes an amplifier 501, a data provider 510 connected to the first input terminal (-) of the amplifier 501, and a pull-down connected to the second input terminal (+) of the amplifier 501. Includes a circuit unit 550.

The amplifier 501 has a first input terminal (-) connected to the data providing unit 510, a second input terminal (+) connected to the pull-down circuit unit 500, and a second input terminal (+) connected to the drain electrode of the first transistor (T1). Includes +). The amplifier 501 may be composed of an OP AMP, and compares the data voltage (Vdata) applied to the first input terminal (-) and the sensing voltage (Vsen) applied to the second input terminal (+) to generate an output voltage (Vout). Adjust. The amplifier 501 compares the voltage of the first input terminal (-) and the second input terminal (+), and when the voltage of the first input terminal (-) is greater than the voltage of the second input terminal (+), the output voltage (Vout) lower the voltage. The amplifier 501 compares the voltage of the first input terminal (-) and the second input terminal (+), and when the voltage of the first input terminal (-) is less than the voltage of the second input terminal (+), the output voltage (Vout) Increase the voltage of

The data provider 510 is connected between the data line (DL) and the first input terminal (-) of the amplifier 501, and transmits the data voltage (Vdata) provided from the data line (DL) to the first input terminal (-) of the amplifier 501. Apply to the input terminal (-). The data provider 510 may directly connect the data line DL to the first input terminal (-) of the amplifier 501, and may include one or more resistors to adjust the size of the data voltage Vdata. .

The pull-down circuit unit 550 is connected between the voltage detection node (VN) and the second input terminal (+) of the amplifier 501. The pull-down circuit unit 550 applies the voltage value of the sensing current flowing to the voltage detection node (VN) to the second input terminal (+) of the amplifier 501.

The driving characteristics compensation circuit 500 may be disposed in the data driver 400, but the location of the driving characteristics compensation circuit 500 is not limited to this.

Figure 3 is a diagram showing a pixel driving signal according to the present invention. FIG. 4 is a diagram showing the operation of a pixel in a sensing and data writing period, and FIG. 5 is a diagram showing the operation of a pixel in a light emission period.

Referring to Figures 3 and 4, in the sensing and data writing period (Tw), the scan signal (SCAN) becomes a turn-on voltage and the emission control signal (EM) becomes a turn-off voltage. In the sensing and data writing period (Tw), the third transistor (T3) is turned off. The first transistor (T1) is turned on by the scan signal and receives the output voltage (Vout) of the amplifier 501. The output voltage (Vout) of the amplifier 501 is programmed as the data voltage (Vdata), and as a result, the gate voltage of the driving transistor (DT) is charged with a voltage reflecting the data voltage (Vdata).

As the voltage of the first node N1 increases due to the output voltage Vout, the driving transistor DT is turned on, and the current Isd flows through the source and drain of the driving transistor DT.

The pull-down circuit unit 500 detects the current (Isd) passing through the source-drain of the driving transistor (DT) via the voltage detection node (VN), obtains the sensing voltage (Vsen), and removes the sensing voltage (Vsen). 2 Write in the input terminal (+). The amplifier 501 uses the sensing voltage (Vsen) as a feedback voltage to adjust the output voltage (Vout). The sensing voltage (Vsen) is a voltage at which the threshold voltage deviation of the driving transistor (DT) is compensated and is proportional to the data voltage (Vdata). That is, during the sensing and data writing period (Tw), the driving characteristics compensation circuit 500 performs an operation to compensate for the deviation of the threshold voltage simultaneously with the programming process of writing data.

The process of programming the output voltage (Vout) of the amplifier 501 to the data voltage (Vdata) in the sensing and data writing period (Tw) will be described later.

Referring to Figures 3 and 5, in the emission period Te, the scan signal SCAN becomes a turn-off voltage and the emission control signal EM becomes a turn-on voltage. In the light emission period Te, the first transistor T1 and the second transistor T2 are turned off. The third transistor T3 connects the second node N2 and the anode of the organic light emitting diode (OLED) in response to the emission control signal EM. The driving transistor (DT) generates a driving current proportional to the data voltage (Vdata) programmed at the gate electrode during the sensing and data writing period (Tw), and the organic light-emitting diode (OLED) emits light.

The process of programming the data voltage (Vdata) with the threshold voltage deviation compensated for to the gate electrode of the driving transistor (DT) in the sensing and data writing period (Tw) is as follows.

In the sensing and data writing period (Tw), the amplifier 501 compares the data voltage (Vdata) and the sensing voltage (Vsen). The sensing voltage (Vsen) varies depending on the threshold voltage of the driving transistor (DT).

When the sensing voltage (Vsen) is lower than the data voltage (Vdata), the output voltage (Vout) of the amplifier 501 is lowered. That is, the voltage of the first node N1 decreases, and the voltage Vsg between the source and gate of the driving transistor DT increases. As the voltage between the source and gate of the driving transistor DT increases, the amount of driving current passing through the driving transistor DT increases. As a result, the voltage of the second node N2 corresponding to the drain electrode of the driving transistor DT increases. That is, when the sensing voltage (Vsen) is lower than the data voltage (Vdata), the voltage of the second node (N2) increases and the sensing voltage (Vsen) increases. Accordingly, the difference between the sensing voltage (Vsen) and the data voltage (Vdata) gradually decreases. When the voltage levels of the sensing voltage (Vsen) and the data voltage (Vdata) are the same, the output voltage (Vout) of the amplifier 501 does not change, and as a result, the voltage of the first node (N1) remains constant. Ultimately, the sensing voltage (Vsen) is set to the same size as the data voltage (Vdata), and the second node (N2) is programmed with a constant voltage proportional to the data voltage (Vdata).

When the sensing voltage (Vsen) is higher than the data voltage (Vdata), the output voltage (Vout) of the amplifier 501 increases. That is, the voltage of the first node N1 increases, and the voltage Vsg between the source and gate of the driving transistor DT decreases. When the voltage between the source and gate of the driving transistor DT decreases, the amount of driving current Isd passing through the driving transistor DT decreases. As a result, the voltage of the second node N2 corresponding to the drain electrode of the driving transistor DT is lowered. When the voltage of the second node (N2) decreases, the voltage of the output pressure detection node (VN) also decreases. Accordingly, the voltage applied to the second input terminal (+) of the amplifier 501 also decreases. That is, when the sensing voltage (Vsen) is higher than the data voltage (Vdata), the voltage of the second node (N2) is lowered and the sensing voltage (Vsen) is lowered. Accordingly, the difference between the sensing voltage (Vsen) and the data voltage (Vdata) gradually decreases. When the voltage levels of the sensing voltage (Vsen) and the data voltage (Vdata) are the same, the output voltage (Vout) of the amplifier 501 does not change, and as a result, the voltage of the first node (N1) remains constant. Ultimately, the sensing voltage (Vsen) is set to the same size as the data voltage (Vdata), and the second node (N2) is programmed with a constant voltage proportional to the data voltage (Vdata).

As such, the present invention uses a driving characteristic compensation circuit composed of a negative feedback circuit to program the data voltage (Vdata) without being affected by the threshold voltage of the driving transistor (DT).

In particular, the present invention can compensate for the threshold voltage in real time by programming the data voltage (Vdata) and simultaneously compensating the threshold voltage through a feedback circuit.

In addition, conventional external compensation detects the anode voltage of an organic light-emitting diode (OLED) as a sensing voltage and converts it into digital data to obtain sensing data. And a lookup table is needed to obtain compensation values according to the sensing data. On the other hand, since the present invention compensates for the threshold voltage based on the analog voltage, unlike the prior art, it does not require an analog digital converter (ADC). Additionally, there is no need for a lookup table to store compensation values that match the sensing data.

Additionally, compared to a typical internal compensation pixel circuit, there are very few transistors included in the pixel, so the aperture ratio can be increased.

FIG. 6 is a diagram showing a pixel circuit and a driving characteristics compensation circuit according to a second embodiment, and FIG. 7 is a diagram showing a pixel circuit and a driving characteristics compensation circuit according to a third embodiment. Figures 6 and 7 show a driving characteristic compensation circuit according to an embodiment of the data provider. Hereinafter, a detailed description of the same configuration as the embodiment described above in FIGS. 6 and 7 will be omitted.

Referring to FIG. 6, the driving characteristics compensation circuit according to the second embodiment includes an amplifier 501, a data provider 510 connected to the first input terminal (-) of the amplifier 501, and a second input terminal of the amplifier 501. It includes a pull-down circuit unit 550 connected to (+).

The data providing unit 510 includes a first resistor (R1) connected between the data line (DL) and the first input terminal (-). The first resistor R1 determines the size of the data voltage Vdata from the data line DL.

Referring to FIG. 7, the pixel circuit and driving characteristics compensation circuit according to the third embodiment include the amplifier 501, the data provider 510 connected to the first input terminal (-) of the amplifier 501, and the amplifier 501. It includes a pull-down circuit unit 550 connected to the second input terminal (+).

The data providing unit 510 includes a first resistor (R1) and a second resistor (R2). The first resistor (R1) is connected between the data line (DL) and the first input terminal (-). One end of the second resistor (R2) is connected to the input terminal of the low potential voltage (ELVSS), and the other end is connected between the first resistor (R1) and the first input terminal (-). The size of the data voltage (Vdata) applied to the first input terminal (-) of the amplifier 501 is determined according to the ratio of the first resistor (R1) and the second resistor (R2). Accordingly, the data provider 510 shown in FIG. 7 can determine the size of the data voltage (Vdata) in more detail.

FIG. 8 is a diagram showing a driving characteristics compensation circuit according to a fourth embodiment, and FIG. 9 is a diagram showing a driving characteristics compensation circuit according to a fifth embodiment. Figures 8 and 9 show a driving characteristic compensation circuit according to an embodiment of the pull-up circuit unit. Hereinafter, a detailed description of the same configuration as the above-described embodiment in the embodiment shown in FIGS. 8 and 9 will be omitted.

Referring to FIG. 8, the driving characteristics compensation circuit according to the fourth embodiment includes an amplifier 501, a data provider 510 connected to the first input terminal (-) of the amplifier 501, and a second input terminal of the amplifier 501. It includes a pull-down circuit unit 500 connected to (+).

The pull-down circuit unit 500 corresponds to a block that converts the driving current of the driving transistor (DT) into the sensing voltage (Vsen), and may be configured as a circuit with a predetermined impedance. The pull-down circuit unit 500 may include a voltage detection node (VN) and a diode (DI) connected to an input terminal of the low potential voltage (ELVSS). The diode (DI) can be designed to have the same characteristics as those of an organic light emitting diode (OLED).

The reasons for setting the characteristics of the diode (DI) to be the same as those of the organic light emitting diode (OLED) are as follows.

In the sensing and data writing period (Tw), the driving current (Idiode) of the driving transistor (DT) flows to the input terminal of the low potential voltage (ELVSS) via the second transistor (T2) and the voltage detection node (VN). That is, during the sensing and data writing period (Tw), the current flows from the drain electrode of the driving transistor (DT) to the input terminal of the low potential voltage (ELVSS). Therefore, the sum of the voltage difference between the drain and source of the driving transistor (DT) (Vds) and the voltage difference between both ends of the diode (DI) corresponds to the difference between the high potential driving voltage (ELVDD) and the low potential voltage (ELVSS). Ultimately, in the sensing and data writing period (Tw), the voltage (Vds) between the drain and source of the driving transistor (DT) is the voltage difference between the voltage detection node (VN) and the low potential voltage (ELVSS) at the high potential driving voltage (ELVDD). It corresponds to the size obtained by subtracting (Vds=ELVDD-Vb, where Vb is the voltage of the voltage detection node).

In the light emission period Te, the driving current Idiode of the driving transistor DT flows to the input terminal of the low potential voltage ELVSS via the third transistor T3 and the organic light emitting diode (OLED). Therefore, the voltage (Vdc) between the drain and source of the driving transistor (DT) in the light emission period (Tw) is the size obtained by subtracting the anode voltage of the organic light emitting diode (OLED) from the high potential driving voltage (ELVDD) (Vds = ELVDD-Vc) , where Vc corresponds to the anode voltage of the organic light-emitting diode.

As seen, the voltage (Vdc) between the drain and source of the driving transistor (DT) varies depending on the current flowing through the diode (DI) or organic light emitting diode (OLED). That is, if the driving characteristics of the diode (DI) of the pull-down circuit unit 500 are different from the driving characteristics of the organic light-emitting diode (OLED) of the pixel (P), it is driven in the sensing and data writing period (Tw) and the light emission period (Tw). The “Vds” of the transistor (DT) varies.

Basically, the driving transistor (DT) operates in the saturation region, so the same driving current flows regardless of “Vds”, but it may be somewhat affected when the current amount is small. Therefore, in order to ensure optimal driving characteristics, it is desirable that the driving characteristics of the diode (DI) of the pull-down circuit unit 500 are set to be the same as those of the organic light-emitting diode (OLED).

Figure 9 is a diagram showing a pixel circuit and a driving characteristic compensation circuit according to the fifth embodiment. Detailed description of the same configuration as the embodiment described above in FIG. 9 will be omitted.

Referring to FIG. 9, the pixel circuit according to the fifth embodiment includes an amplifier 501, a data provider 510 connected to the first input terminal (-) of the amplifier 501, and a second input terminal (+) of the amplifier 501. ) includes a pull-down circuit unit 500 connected to

The pull-down circuit unit 550 includes a third resistor (R3) connected between the voltage detection node (VN) and the input terminal of the low potential voltage (ELVSS). When the pull-down circuit unit 550 is comprised of the third resistor R3, the gamma characteristics of the data voltage Vdata in the data providing unit 510 may vary.

The size of the data voltage (Vdata) according to the image data (DATA) is set to take into account the voltage-current characteristics of the organic light-emitting diode (OLED). Organic light-emitting diodes (OLEDs) have non-linear characteristics in which the amount of change in current decreases in proportion to the voltage in areas of high voltage, and the size of the data voltage (Vdata) is determined by taking into account the voltage-current characteristics of organic light-emitting diodes (OLEDs). It is set. As in the fourth embodiment shown in FIG. 8, when the pull-down circuit unit 550 uses a diode (DI) corresponding to the characteristics of the organic light emitting diode (OLED) of the pixel, the data voltage (Vdata) is a general organic light emitting diode (Vdata). The one applied to the display device can be used. In contrast, since the voltage of the pull-down circuit unit 550 in the embodiment shown in FIG. 9 changes linearly with respect to the current flowing through the voltage detection node VN, it is preferable to vary the data voltage Vdata non-linearly.

Figure 10 is a diagram showing a pixel circuit and a driving characteristic compensation circuit according to the sixth embodiment. Detailed description of the same configuration as the embodiment described above in FIG. 10 will be omitted.

Referring to FIG. 10, the driving characteristics compensation circuit according to the sixth embodiment includes an amplifier 501, a data provider 510 connected to the first input terminal (-) of the amplifier 501, and a second input terminal of the amplifier 501. It includes a pull-down circuit unit 500 connected to (+).

The pull-down circuit unit 550 includes a diode (DI) and a third resistor (R3) connected in parallel between the voltage detection node (VN) and the input terminal of the low potential voltage (ELVSS). The third resistor R3 facilitates the formation of a current path for the driving transistor DT even at low gray levels. When the voltage applied to the gate electrode of the driving transistor DT is low, a current path from the source electrode to the drain electrode of the driving transistor DT may not be formed smoothly. The third resistor RE connected in parallel with the diode DI ensures smooth current flow through the driving transistor DT even when the data voltage Vdata is low in low gray level.

Figure 11 is a diagram showing a pixel circuit and a driving characteristic compensation circuit according to the seventh embodiment. Detailed description of the same configuration as the embodiment described above in FIG. 11 will be omitted.

Referring to FIG. 11, the pixel circuit according to the seventh embodiment includes an organic light emitting diode (OLED), a driving transistor (DT), a storage capacitor (Cst), a first transistor (T1), a second transistor (T2), and a third transistor (T2). It includes a transistor (T3) and a fourth transistor (T4).

The fourth transistor T4 includes a gate electrode connected to the scan line (SCL), a drain electrode connected to the input terminal of the initialization voltage (Vinit), and a source electrode connected to the anode electrode of the organic light emitting diode (OLED). The fourth transistor T4 applies an initialization voltage Vinit to the anode electrode of the fourth organic light emitting diode OLED in response to the scan signal SCAN. That is, the fourth transistor T4 is initialized by discharging the anode electrode of the organic light emitting diode (OLED) during the sensing and data writing period (Tw). The drain electrode of the fourth transistor (T4) may be connected to the low potential voltage (ELVSS), and the anode electrode of the organic light emitting diode (OLED) may be initialized to the low potential voltage (ELVSS).

Through the above-described content, those skilled in the art will be able to see that various changes and modifications can be made without departing from the technical idea of the present invention. Therefore, the technical scope of the present invention should not be limited to what is described in the detailed description of the specification, but should be defined by the scope of the patent claims.

100: display panel 200: timing controller
300: Gate driver 400: Gate driver
500: Driving characteristics compensation circuit 501: Amplifier
510: data provision unit 550: pull-down circuit unit

Claims (13)

A driving transistor whose gate electrode is connected to a first node receiving a data voltage, a source electrode connected to an input terminal of a high potential driving voltage, and a drain electrode connected to a second node connected to an anode electrode of an organic light emitting diode;
a light emission control transistor that controls a current path between the second node and the organic light emitting diode; and
A driving characteristic compensation circuit that compares the sensing voltage of the second node with the data voltage and provides a constant output voltage to the first node when the sensing voltage and the data voltage are equal,
The driving characteristics compensation circuit is,
an amplifier that adjusts the size of the output voltage by comparing the data voltage provided to a first input terminal and the sensing voltage provided to a second input terminal; and
A pull-down circuit connected to a second input terminal of the amplifier,
In response to a scan signal, it further includes a second transistor connecting the second node and the pull-down circuit unit,
The source electrode of the second transistor is connected to the voltage detection node of the pull-down circuit unit,
The pull-down circuit unit,
An organic light emitting display device comprising a diode connected between the voltage detection node and a low-potential voltage input terminal. delete According to claim 1,
The amplifier is
When the voltage of the first input terminal is greater than the voltage of the second input terminal, the level of the output voltage is lowered,
An organic light emitting display device that is an OP AMP that increases the level of the output voltage when the voltage of the first input terminal is less than the voltage of the second input terminal. According to claim 1,
The driving characteristics compensation circuit is
An organic light emitting display device comprising a first resistor connected between the first input terminal and a data line providing the data voltage. According to claim 4,
The driving characteristics compensation circuit is
The organic light emitting display device further includes a node between the first input terminal and the first resistor and a second resistor connected to an input terminal of a low potential voltage. According to claim 1,
During the sensing and data writing period
The organic light emitting display device further includes a first transistor connecting the output terminal of the amplifier and the first node in response to a scan signal. According to claim 6,
The pull-down circuit part
An organic light emitting display device that obtains the voltage of the second node as a sensing voltage when a current flows from the high potential driving voltage to the second node during the sensing and data writing period. According to claim 7,
The second transistor is,
In the above sensing and data writing period,
An organic light emitting display device connecting the second node and the pull-down circuit unit in response to the scan signal. delete delete According to claim 1,
The pull-down circuit part
The organic light emitting display device further includes a third resistor connected in parallel with the diode between the voltage detection node and the input terminal of the low potential voltage. According to claim 6,
The gate electrode of the light emission control transistor is controlled by a light emission control signal,
The light emission control signal is
Maintaining the turn-off voltage during the sensing and data writing period,
An organic light emitting display device maintaining a turn-on voltage during the light emission period following the sensing and data writing period. According to claim 6,
The organic light emitting display device further includes an initialization control unit that provides an initialization voltage to an anode electrode of the organic light emitting diode in response to the scan signal during the sensing and data writing period.

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