KR102603602B1 - Pixel Compensation Device And Organic Light Emitting Display Device Including The Same - Google Patents

Abstract

A pixel compensation device according to an embodiment of the present invention includes a sensing unit connected to a driving element of each pixel through a sensing line. The sensing unit may include a first integrator that senses a drain-source current flowing through the driving element in response to a gate-source voltage of the driving element; a first analog-to-digital converter that converts the current sensing result of the first integrator into analog-digital and outputs first sensing result data; a second integrator that senses the source electrode voltage of the driving element changed according to the drain-source current; and a second analog-to-digital converter that converts the voltage sensing result of the second integrator into analog-digital and outputs second sensing result data.

Description

Pixel Compensation Device And Organic Light Emitting Display Device Including The Same}

The present invention relates to an organic light emitting display device, and particularly to a pixel compensation device and an organic light emitting display device including the same.

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

An organic light emitting display device arranges pixels, each including OLED, in a matrix form and adjusts the luminance of the pixels according to the gradation of image data. Each pixel includes a driving element, that is, a driving TFT (Thin Film Transistor), that controls the driving current flowing through the OLED according to the voltage applied between the gate electrode and the source electrode. The driving characteristics of a driving TFT change depending on temperature or deterioration. If the driving characteristics of the driving TFT vary for each pixel, the luminance between pixels will vary even if the same image data is written, making it difficult to realize the desired image.

External compensation techniques are known to compensate for changes in driving characteristics for the driving TFT. External compensation technology senses the driving characteristics of the driving TFT and modulates the image data according to the change in driving characteristics based on the sensing results.

The driving characteristics of the driving TFT include threshold voltage and electron mobility. The principle of sensing electron mobility is to sense the amount of voltage that changes at the source electrode of the driving TFT for a certain period of time while the driving TFT is turned on. This electron mobility sensing method has a fast sensing speed because sensing is performed while the driving TFT is turned on. Meanwhile, the principle of sensing the threshold voltage is to sense the voltage charged at the source electrode of the driving TFT when the driving TFT, which operates as a source follower, is saturated. This threshold voltage sensing method has a slow sensing speed because it must wait until the driving TFT is saturated for voltage sensing.

The panel temperature may fluctuate during screen display, and in this case, not only the electron mobility characteristics but also the threshold voltage characteristics may change. Electron mobility sensing is possible while the screen is displayed, so electron mobility characteristics that change in real time can be quickly reflected in the sensing value and compensated. On the other hand, threshold voltage sensing cannot be implemented during screen display and is performed only during the screen-off state, i.e., during the power-off period, so the continuously changing threshold voltage characteristics during screen display cannot be quickly reflected in the sensing value. If the threshold voltage fluctuations of the driving TFT are not properly compensated in real time, the compensation value update cycle becomes long, which may deteriorate the reliability of compensation.

Accordingly, the present invention provides a pixel compensation device that can sense not only the electron mobility of the driving TFT but also the threshold voltage in real time during screen display, and an organic light emitting display device including the same.

A pixel compensation device according to an embodiment of the present invention includes a sensing unit connected to a driving element of each pixel through a sensing line. The sensing unit may include a first integrator that senses a drain-source current flowing through the driving element in response to a gate-source voltage of the driving element; a first analog-to-digital converter that converts the current sensing result of the first integrator into analog-digital and outputs first sensing result data; a second integrator that senses the source electrode voltage of the driving element changed according to the drain-source current; and a second analog-to-digital converter that converts the voltage sensing result of the second integrator into analog-digital and outputs second sensing result data.

The present invention senses not only the electron mobility of the driving TFT but also the threshold voltage in real time during screen display, so that continuously changing driving characteristics during screen display can be quickly reflected in the sensed value. The present invention can increase compensation reliability by shortening the update cycle of the compensation value by appropriately compensating for the threshold voltage variation as well as the electronic mobility variation of the driving TFT in real time.

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 array connected to the pixel driver of the present invention.
Figure 3 is a diagram showing a schematic connection relationship between a pixel, a sensing unit, and a compensation unit of the present invention.
Figure 4 is a diagram showing that the sensing drive of the present invention is performed within a vertical blank period.
Figure 5 is a diagram showing a specific connection relationship between a pixel and a sensing unit according to an embodiment of the present invention.
FIG. 6 is a diagram showing the driving timing of the pixel and sensing unit of FIG. 5.
Figure 7 is a diagram showing a specific connection relationship between a pixel and a sensing unit according to another embodiment of the present invention.
FIG. 8 is a diagram showing the driving timing of the pixel and sensing unit of FIG. 7.

The advantages and features of the present specification and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present specification is not limited to the embodiments disclosed below and will be implemented in various different forms, but the present embodiments only serve to ensure that the disclosure of the present specification is complete, and that common knowledge in the technical field to which this specification pertains is provided. It is provided to fully inform those who have the scope of the invention, and this specification is only defined by the scope of the claims.

The shape, size, ratio, angle, number, etc. disclosed in the drawings for explaining embodiments of the present specification are illustrative, and the present specification is not limited to the matters shown. Like reference numerals refer to like elements throughout the specification. When 'includes', 'has', 'consists of', etc. mentioned in the specification are used, other parts may be added unless '~ only' is used. When a component is expressed in the singular, the plural is included unless specifically stated otherwise.

When interpreting a component, it is interpreted to include the margin of error even if there is no separate explicit description.

In the case of a description of a positional relationship, for example, if the positional relationship between two parts is described as 'on top', 'on top', 'at the bottom', 'next to ~', 'right next to' Alternatively, there may be one or more other parts placed between the two parts, unless 'directly' is used.

First, second, etc. may be used to describe various components, but these components are not limited by these terms. These terms are merely used to distinguish one component from another. Accordingly, the first component mentioned below may be the second component within the technical idea of the present specification.

Like reference numerals refer to substantially like elements throughout the specification.

In this specification, the pixel circuit and the gate driver formed on the substrate of the display panel may be implemented as a TFT with an n-type MOSFET (Metal Oxide Semiconductor Field Effect Transistor) structure, but are not limited to this and may also be implemented as a TFT with a p-type MOSFET structure. there is. TFT is a three-electrode device including a gate, source, and drain. The source is an electrode that supplies carriers to the transistor. Within the TFT, carriers begin to flow from the source. The drain is the electrode through which carriers go out of the TFT. That is, the flow of carriers in the MOSFET flows from the source to the drain. In the case of n-type TFT (NMOS), because the carriers are electrons, the source voltage has a lower voltage than the drain voltage to allow electrons to flow from the source to the drain. Since electrons flow from the source to the drain in an n-type TFT, the direction of current flows from the drain to the source. On the other hand, in the case of p-type TFT (PMOS), since the carrier is a hole, the source voltage is higher than the drain voltage so that holes can flow from the source to the drain. In a p-type TFT, current flows from the source to the drain because holes flow from the source to the drain.

Hereinafter, embodiments of the present specification will be described in detail with reference to the attached drawings. In the following description, if it is determined that a detailed description of a known function or configuration related to the present specification may unnecessarily obscure the gist of the present specification, the detailed description will be omitted.

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 array connected to the pixel driver of the present invention. And, Figure 3 is a diagram showing a schematic connection relationship between the pixel, sensing unit, and compensation unit of the present invention.

Referring to FIGS. 1 to 3 , an organic light emitting display device according to an embodiment of the present invention may include a display panel 10, a timing controller 11, and a panel driver. The panel driver includes a data driver circuit 12 and a gate driver circuit 13.

In the display panel 10, a plurality of data lines 14 and sensing lines 16 and a plurality of gate lines 15 intersect, and pixels PXL are arranged in a matrix form in each intersection area. Construct a pixel array.

The pixel array includes a plurality of pixel lines (PNL1 to PNL4), and each pixel line (PNL1 to PNL4) includes a plurality of pixels (PXL) and a plurality of signal lines. The signal lines are data lines 14 for supplying data voltages for display and sensing to the pixels (PXL), supplying a reference voltage to the pixels (PXL) and sensing the driving characteristics of the pixels (PXL). sensing lines 16 for supplying a display scan signal (SCAN) and a sensing scan signal (SCAN) to the pixels (PXL), and gate lines (15) for supplying a high-potential pixel voltage to the pixels (PXL). It may include high potential power lines (PWL) to supply. Each pixel (PXL) included in the pixel array may further receive a low-potential pixel voltage from the power generator. The power generator may supply a low-potential pixel voltage to the pixel (PXL) through a low-potential power line or pad portion.

Each pixel (PXL) may be connected to one of the data lines 14, one of the sensing lines 16, and one of the gate lines 15. The pixels PXL constituting the pixel array may include a red pixel for displaying red, a green pixel for displaying green, a blue pixel for displaying blue, and a white pixel for displaying white. Four pixels including a red pixel, a green pixel, a blue pixel, and a white pixel may constitute one pixel unit (UPXL). However, the configuration of the pixel unit (UPXL) is not limited to this. A plurality of pixels (PXL) constituting the same pixel unit (UPXL) may share one sensing line 16 or may be independently connected to different sensing lines.

The pixel (PXL) of the present invention may include a plurality of TFTs including an OLED and a driving TFT (Thin Film Transistor). TFTs may be implemented as a P type, an N type, or a hybrid type combining the P type and the N type. Additionally, the semiconductor layer of the TFT may include amorphous silicon, polysilicon, or oxide.

Organic light emitting display devices with such pixel arrays employ external compensation technology. External compensation technology is a technology that senses the driving characteristics of the driving TFT provided in the pixels (PXL) and corrects the input image data (DATA) according to the sensed value. The driving characteristics of the driving TFT refer to the threshold voltage of the driving TFT and the electron mobility of the driving TFT.

The organic light emitting display device of the present invention performs an external compensation operation during an image display operation. The external compensation operation may be performed in a vertical blank period during the image display operation. The vertical blank period is a period in which video data (DATA) is not written, and is disposed between vertical active sections in which one frame of video data (DATA) is written.

The timing controller 11 can implement display driving and sensing driving by controlling the sensing driving timing and display driving timing for the pixel lines (PNL1 to PNL4) of the display panel 10 according to a predetermined sequence. The “pixel line” described in the present invention does not mean a physical signal line, but rather a collection of pixels (PXL) that are adjacent to each other along the extension direction of the gate line.

The timing controller 11 may generate different timing control signals (GDC, DDC) for display driving and timing control signals (GDC, DDC) for sensing driving.

The gate control signal (GDC) includes a gate start pulse (GSP) and a gate shift clock (GSC). The gate start pulse (GSP) is applied to the gate stage that generates the first scan signal and controls the gate stage to generate the first scan signal. The gate shift clock (GSC) is a clock signal commonly input to the gate stages and is a clock signal for shifting the gate start pulse (GSP).

The data control signal (DDC) includes a source start pulse (Source Start Pulse, SSP), a source sampling clock (SSC), and a source output enable signal (Source Output Enable, SOE). The source start pulse (SSP) controls the data sampling start timing of the data driving circuit 12. The source sampling clock (SSC) is a clock signal that controls the sampling timing of data in each of the source drive ICs based on the rising or falling edge. The source output enable signal (SOE) controls the output timing of the data driving circuit 12. The data control signal (DDC) includes various signals for controlling the operation of the sensing unit included in the data driving circuit 12.

Sensing drive writes the sensing data voltage (VDATA-SEN) to the pixels (PXL) included in the sensing target pixel line to sense the driving characteristics of the corresponding pixels (PXL), and based on the sensing result data (SDV) This means updating the compensation value to compensate for changes in the driving characteristics of the corresponding pixels (PXL). Sensing drive is implemented by the panel driver and pixel compensation device of the present invention. The pixel compensation device includes a sensing unit 124 and a compensation unit 110. The sensing unit 124 may be built into the data driving circuit 12, and the compensation unit 110 may be built into the timing controller 11, but are not limited to this.

Meanwhile, display driving corrects the digital image data (DATA) to be input to the corresponding pixels (PXL) based on the updated compensation value, and generates a display data voltage (VDATA-) corresponding to the corrected image data (DATA). This means applying DIS) to the corresponding pixels (PXL) to display the input image. Display driving is implemented by the panel driving unit of the present invention.

The timing controller 11 transmits the corrected image data (DATA) to the data driving circuit 12 for display driving.

The data driving circuit 12 includes at least one source driver integrated circuit (IC). This source driver IC may include digital-to-analog converters (hereinafter referred to as DAC) 122 and a sensing unit 124 connected to each sensing line 16.

The DACs 122 include DAC1, which generates a display data voltage (VDATA-DIS) when driving the display and a data voltage for sensing (VDATA-SEN) when driving the display, and a reference voltage (VREF) when driving the display and sensing. It may include DAC2 that generates.

DAC1 converts the corrected image data (DATA) into digital-analog when driving the display, generates a data voltage (VDATA-DIS) for display, and supplies it to the data lines 14. DAC1 considers the luminous efficiency of each color during sensing operation, generates a preset sensing data voltage (VDATA-SEN) for each color of the pixels (PXL), and supplies it to the data line 14.

DAC2 can be connected to the sensing line 16 through the first connection switch (SW1). The first connection switch SW1 is turned on only during the voltage programming period during display driving and sensing driving, and is turned off at other times. DAC2 generates a reference voltage (VREF) when driving the display and sensing and supplies it to the sensing line (16).

The sensing unit 124 does not operate when the display is driven, but operates only when the sensing is driven. The sensing unit 124 may include two integrators and two analog-to-digital converters (hereinafter referred to as ADCs) to sense not only the electron mobility of the driving TFT (DT) but also the threshold voltage in the vertical blank period. . The sensing unit 124 may further include a sample and hold unit and an ADC in addition to two integrators and two ADCs to sense not only the electron mobility of the driving TFT (DT) but also the threshold voltage in the vertical blank period. there is.

The gate driving circuit 13 generates a scan signal (SCAN) for display driving and sensing driving based on the gate control signal (GDC) and then supplies it to the gate lines 15. When driving the display, the gate driving circuit 13 may generate a display scan signal (SCAN) and sequentially supply it to the gate lines 15 according to the writing order of the image data (DATA). The gate driving circuit 13 can generate a sensing scan signal (SCAN) during sensing operation and supply it only to the gate line 15 connected to the sensing target pixel line. The gate driving circuit 13 may be built in a non-display area (or bezel area) of the display panel 10.

Figure 4 is a diagram showing that the sensing drive of the present invention is performed within a vertical blank period.

Referring to FIG. 4, the display driving of the present invention is performed in a vertical active period (VAP), and the sensing driving of the present invention is performed in a vertical blank period (VBP). In other words, the sensing operation of the present invention is performed in real time while the screen is displayed. The present invention senses not only the electron mobility of the driving TFT but also the threshold voltage in real time during screen display, so that continuously changing driving characteristics during screen display can be quickly reflected in the sensed value. The present invention can increase compensation reliability by shortening the update cycle of the compensation value by appropriately compensating for the threshold voltage variation as well as the electronic mobility variation of the driving TFT in real time.

Meanwhile, the sensing drive is performed on one pixel line per vertical blank period, and at this time, the pixels (PXL) included in the pixel line stop emitting light. This is to increase the accuracy of sensing. Because the corresponding pixel line is sensed while the screen is turned on in the vertical blank period, the sensed pixel line may be noticeable. In this case, the emission time of the sensed pixel line is inevitably shorter than the emission time of the non-sensed pixel lines. In order to reduce the visibility of line dims due to differences in emission times, the position of the sensed pixel line changes every frame, but changes regardless of the display scan order (i.e., randomly).

Figure 5 is a diagram showing a specific connection relationship between a pixel and a sensing unit according to an embodiment of the present invention. And, FIG. 6 is a diagram showing the driving timing of the pixel and sensing unit of FIG. 5.

Referring to FIG. 5, one pixel (PXL) according to an embodiment of the present invention includes an OLED, a driving TFT (DT), first and second switch TFTs (ST1, ST2), and a storage capacitor (Cst). .

OLED is a light-emitting device that emits light with an intensity corresponding to the driving current (Ids) drawn from the driving TFT (DT). The anode electrode of the OLED is connected to the second node (N2), and the cathode electrode is connected to the input terminal of the low-potential pixel voltage (EVSS). The OLED turns on and starts emitting light when the voltage of the second node (N2) increases to the operating point voltage when the display is driven. However, during sensing operation, the OLED does not emit light. This is because sensing operation occurs before the voltage of the second node (N2) increases to the operating point of the OLED.

The driving TFT (DT) is a driving element that generates a driving current (Ids) corresponding to the gate-source voltage. The gate electrode of the driving TFT (DT) is connected to the first node (N1), the drain electrode is connected to the input terminal of the high-potential pixel voltage (EVDD) through a high-potential power line, and the source electrode is connected to the second node (N2). is connected to

The first and second switch TFTs (ST1, ST2) serve to set the gate-source voltage of the driving TFT (DT). When driving a display, the voltage between the gate and source of the driving TFT (DT) corresponds to the difference between the display data voltage (VDATA-DIS) and the reference voltage (VREF). During sensing operation, the voltage between the gate and source of the driving TFT (DT) corresponds to the difference between the sensing data voltage (VDATA-SEN) and the reference voltage (VREF). Additionally, the second switch TFT (ST2) serves to connect the driving TFT (DT) and the sensing unit 124 during sensing operation.

The gate electrode of the first switch TFT (ST1) is connected to the gate line 15, the drain electrode is connected to the data line 14, and the source electrode is connected to the first node (N1). The first switch TFT (ST1) is turned on according to the display scan signal (SCAN) from the gate line 15 when the display is driven, and the display data voltage (VDATA-DIS) charged in the data line 14 is turned on to the first switch TFT (ST1). Applies to node (N1). In addition, the first switch TFT (ST1) is turned on in accordance with the sensing scan signal (SCAN) from the gate line 15 during sensing operation and uses the sensing data voltage (VDATA-SEN) charged in the data line 14. It is applied to the first node (N1).

The gate electrode of the second switch TFT (ST2) is connected to the gate line 15, the drain electrode is connected to the second node (N2), and the source electrode is connected to the sensing line 16. The second switch TFT (ST2) is turned on according to the display scan signal (SCAN) from the gate line (15) when the display is driven, and the reference voltage (VREF) charged in the sensing line (16) is connected to the second node (N2). Authorized to. In addition, the second switch TFT (ST2) is turned on according to the sensing scan signal (SCAN) from the gate line 15 during sensing operation, and the reference voltage (VREF) charged in the sensing line 16 is connected to the second node ( After being applied to N2), the driving current flowing through the driving TFT (DT) is applied to the sensing unit 124 through the sensing line 16, and at the same time, the source electrode voltage (Vsen) of the driving TFT (DT) is applied to the sensing line (DT). It is applied to the sensing unit 124 through 16).

The storage capacitor Cst is connected between the first node N1 and the second node N2 to maintain the gate-source voltage of the driving TFT DT for a desired period.

Referring to FIG. 5, the sensing unit 124 according to an embodiment of the present invention includes first and second integrators to sense not only the electron mobility of the driving TFT (DT) but also the threshold voltage in the vertical blank period. It may include ADC1 and ADC2. The sensing unit 124 operates during a sensing drive performed in a vertical blank period.

The first integrator senses the driving current (i.e., drain-source current (Ids)) flowing through the driving TFT (DT) in response to the gate-source voltage of the driving TFT (DT). For this purpose, the first integrator includes a first operational amplifier (AMP1) and a first feedback capacitor (CFB1).

The first operational amplifier (AMP1) has a first inverting input terminal (-) connected to the sensing line 16, a first non-inverting input terminal (+) into which the free voltage (Vpre) is input, and a current sensing result (VI It has a first output terminal through which -SEN) is output. The first feedback capacitor CFB1 is connected between the first inverting input terminal (-) and the first output terminal.

ADC1 is connected to the first output terminal of the first operational amplifier (AMP1). ADC1 converts the current sensing result (VI-SEN) of the first integrator into analog-digital and outputs first sensing result data (SDV1).

The second integrator senses the source electrode voltage (Vsen) of the driving TFT (DT) changed according to the drain-source current (Ids) of the driving TFT (DT). To this end, the second integrator includes an input resistor (Rin), a second operational amplifier (AMP2), and a second feedback capacitor (CFB2).

The input resistance (Rin) is connected to the sensing line (16).

The second operational amplifier (AMP2) has a second inverting input terminal (-) connected to the input resistance (Rin), a second non-inverting input terminal (+) to which the free voltage (Vpre) is input, and a voltage sensing result (VV). It has a second output terminal through which -SEN) is output. The second feedback capacitor CFB2 is connected between the second inverting input terminal (-) and the second output terminal.

ADC2 is connected to the second output terminal of the second operational amplifier (AMP2). ADC2 converts the voltage sensing result (VV-SEN) of the second integrator into analog-digital and outputs second sensing result data (SDV2).

Referring to FIG. 6, the sensing drive is performed in the vertical blank period (VBP) and proceeds in the following order: initialization period (①), programming period (②), and sensing period (③).

In the initialization period (①), the sensing scan signal (SCAN) is input at an off level and the reference voltage control signal (SPRE) is input at an on level. In the initialization period (①), the first connection switch (SW1) is turned on to apply the reference voltage (VREF) to the sensing line (16). As a result, the sensing line 16 is initialized to the reference voltage (VREF).

In the programming period (②), the sensing scan signal (SCAN) and the reference voltage control signal (SPRE) are input at the on level. In the programming period (②), the first switch TFT (ST1) is turned on and the sensing data voltage (VDATA-SEN) is applied to the first node (N1), and the second switch TFT (ST2) and the first connection switch are connected to each other. (SW1) is turned on and the reference voltage (VREF) is applied to the second node (N2). As a result, the voltage between the gate and source of the driving TFT (DT) is programmed.

In the sensing period (③), the sensing scan signal (SCAN) is input at an on level and the reference voltage control signal (SPRE) is input at an off level. In the sensing period (③), the source electrode of the driving TFT (DT) is connected to the sensing unit 124 through the second switch TFT (ST2) and the sensing line 16. A drain-source current (Ids) flows in the driving TFT (DT) in response to the programmed gate-source voltage, and the source electrode voltage (Vsen) of the driving TFT (DT) is changed by this drain-source current (Ids). ) rises from the reference voltage (VREF). During the sensing period (③), the driving TFT (DT) remains turned on.

The first integrator senses the drain-source current (Ids) flowing through the driving TFT (DT) within the sensing period (③) during which the driving TFT (DT) remains turned on. The current sensing result (VI-SEN) of the first integrator is It is calculated as

The second integrator senses the source electrode voltage (Vsen) of the driving TFT (DT) increased according to the drain-source current (Ids) during the sensing period (③) during which the driving TFT (DT) remains turned on. The voltage sensing result (VV-SEN) of the second integrator is - It is calculated as

The compensation unit 110 stores first sensing result data (SDV1), which is a digital value of the current sensing result (VI-SEN) of the first integrator, and second sensing result data, which is a digital value of the voltage sensing result (VV-SEN) of the second integrator. Using (SDV2), first compensation data for compensating for changes in electron mobility of the driving TFT (DT) and second compensation data for compensating for changes in the threshold voltage of the driving TFT (DT) are calculated.

The compensation unit 110 is provided in advance with a first lookup table in which the first voltage change slope is stored, and maps the second sensing result data (SDV2) to the first lookup table to compensate for the change in electron mobility of the driving TFT (DT). First compensation data can be calculated to do this.

The compensation unit 110 substitutes the first sensing result data (SDV1), the second sensing result data (SDV2), and the first compensation data into the current equation of the driving TFT (DT), Ids=α*(Vgs-Vth) ^2. Thus, second compensation data to compensate for the change in threshold voltage of the driving TFT (DT) can be calculated. Here, the first sensing result data (SDV1) is a value substituted for “Ids” in the current formula, the second sensing result data (SDV2) is a value substituted for “Vgs” in the current formula, and the first compensation data is the current This is the value substituted for “α” in the formula. “Vgs” in the current formula is the gate-source voltage (Vg-Vs), and “Vg” is a previously known value as the sensing data voltage (VDATA-SEN). “Vs” becomes the second sensing result data (SDV2).

Figure 7 is a diagram showing a specific connection relationship between a pixel and a sensing unit according to another embodiment of the present invention. And, FIG. 8 is a diagram showing the driving timing of the pixel and sensing unit of FIG. 7.

Referring to FIG. 7, one pixel (PXL) according to an embodiment of the present invention includes an OLED, a driving TFT (DT), first and second switch TFTs (ST1, ST2), and a storage capacitor (Cst). . This is substantially the same as what was described in FIG. 5.

Referring to FIG. 7, the sensing unit 124 according to another embodiment of the present invention includes first and second integrators to sense not only the electron mobility of the driving TFT (DT) but also the threshold voltage in the vertical blank period. It may include ADC1 and ADC2, and may further include a sample and hold unit (SH) and ADC3. The sensing unit 124 operates during a sensing drive performed in a vertical blank period.

The first and second integrators and ADC1 and ADC2 are substantially the same as those described in FIG. 5.

The sample and hold unit (SH) senses the source electrode voltage (Vsen) of the driving TFT (DT) changed according to the drain-source current (Ids) of the driving TFT (DT). The sample and hold unit (SH) senses the source electrode voltage (Vsen) of the driving TFT (DT) increased according to the drain-source current (Ids) during the sensing period when the driving TFT (DT) remains turned on. .

ADC3 converts the voltage sensing result (Vsen) of the sample and hold unit (SH) into analog-digital and outputs third sensing result data (SDV3).

Referring to Figure 8, the sensing drive is performed in the vertical blank period (VBP) and proceeds in the following order: initialization period (①), programming period (②), first sensing period (③), and second sensing period (④). do.

In the initialization period (①), the sensing scan signal (SCAN) is input at an off level and the reference voltage control signal (SPRE) is input at an on level. In the initialization period (①), the first connection switch (SW1) is turned on to apply the reference voltage (VREF) to the sensing line (16). As a result, the sensing line 16 is initialized to the reference voltage (VREF).

In the programming period (②), the sensing scan signal (SCAN) and the reference voltage control signal (SPRE) are input at the on level. In the programming period (②), the first switch TFT (ST1) is turned on and the sensing data voltage (VDATA-SEN) is applied to the first node (N1), and the second switch TFT (ST2) and the first connection switch are connected to each other. (SW1) is turned on and the reference voltage (VREF) is applied to the second node (N2). As a result, the voltage between the gate and source of the driving TFT (DT) is programmed.

In the first sensing period (③), the sensing scan signal (SCAN) is input at an on level and the reference voltage control signal (SPRE) is input at an off level. In the sensing period (③), the source electrode of the driving TFT (DT) is connected to the sensing unit 124 through the second switch TFT (ST2) and the sensing line 16. A drain-source current (Ids) flows in the driving TFT (DT) in response to the programmed gate-source voltage, and the source electrode voltage (Vsen) of the driving TFT (DT) is changed by this drain-source current (Ids). ) rises from the reference voltage (VREF). In the first sensing period (③), the driving TFT (DT) remains turned on.

The first integrator senses the drain-source current (Ids) flowing through the driving TFT (DT) within the first sensing period (③) during which the driving TFT (DT) remains turned on. The current sensing result (VI-SEN) of the first integrator is It is calculated as

The second integrator senses the source electrode voltage (Vsen) of the driving TFT (DT) increased according to the drain-source current (Ids) during the first sensing period (③) during which the driving TFT (DT) remains turned on. do. The voltage sensing result (VV-SEN) of the second integrator is - It is calculated as

In the second sensing period (④), the sensing scan signal (SCAN) is maintained at the on level, the reference voltage control signal (SPRE) is maintained at the off level, and the sampling signal (SAMP) is input at the on level. In the second sensing period (④), the black display data voltage (BLK) is applied to the gate electrode of the driving TFT (DT), and the source electrode of the driving TFT (DT) is applied to the second switch TFT (ST2) and the sensing line ( It is connected to the sensing unit 124 through 16). In the second sensing period (④), the drain-source current (Ids) does not flow in the driving TFT (DT) due to the black display data voltage (BLK) applied to the gate electrode, and the source of the driving TFT (DT) The electrode voltage Vsen is maintained at the voltage at the end of the first sensing period ③. In the second sensing period (④), the driving TFT (DT) remains turned off.

The sample and hold unit (SH) measures the source electrode voltage ( Vsen) is sensed within the second sensing period (④) during which the driving TFT (DT) remains turned off.

The compensation unit 110 stores first sensing result data (SDV1), which is a digital value of the current sensing result (VI-SEN) of the first integrator, and second sensing result data, which is a digital value of the voltage sensing result (VV-SEN) of the second integrator. (SDV2) and the digital value of the voltage sensing result (Vsen) of the sample and hold unit (SH) is the first to compensate for the change in electron mobility of the driving TFT (DT) using the third sensing result data (SDV3). Compensation data and second compensation data for compensating for changes in the threshold voltage of the driving TFT (DT) are calculated.

The compensation unit 110 is equipped in advance with a second look-up table in which the second voltage change slope is stored, and maps the third sensing result data (SDV3) to the second look-up table to compensate for the change in electron mobility of the driving TFT (DT). First compensation data can be calculated to do this.

The compensation unit 110 substitutes the first sensing result data (SDV1), the second sensing result data (SDV2), and the first compensation data into the current equation of the driving TFT (DT), Ids=α*(Vgs-Vth) ^2. Thus, second compensation data to compensate for the change in threshold voltage of the driving TFT (DT) can be calculated. Here, the first sensing result data (SDV1) is a value substituted for “Ids” in the current formula, the second sensing result data (SDV2) is a value substituted for “Vgs” in the current formula, and the first compensation data is the current This is the value substituted for “α” in the formula. “Vgs” in the current formula is the gate-source voltage (Vg-Vs), and “Vg” is a previously known value as the sensing data voltage (VDATA-SEN). “Vs” becomes the second sensing result data (SDV2).

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.

10: display panel 11: timing controller
12: data driving circuit 13: gate driving circuit
14: data line 16: sensing line
15: gate line 110: compensation unit
124: Sensing unit

Claims (11)

A sensing unit connected to the driving element of each pixel through a sensing line,
The sensing unit,
a first integrator that senses a drain-source current flowing through the driving element in response to a gate-source voltage of the driving element;
a first analog-to-digital converter that converts the current sensing result of the first integrator into analog-digital and outputs first sensing result data;
a second integrator that senses the source electrode voltage of the driving element changed according to the drain-source current; and
a second analog-to-digital converter that converts the voltage sensing result of the second integrator into analog-digital and outputs second sensing result data; and
Further comprising a compensation unit for compensating for changes in electron mobility and threshold voltage of the driving element,
The compensation department,
First compensation data is calculated based on the first sensing result data to compensate for the change in electron mobility of the driving element, and the first sensing result data and the second compensation data are calculated to compensate for the change in the threshold voltage of the driving element. A pixel compensation device that calculates second compensation data based on sensing result data. According to claim 1,
The first integrator is,
a first operational amplifier having a first inverting input terminal connected to the sensing line, a first non-inverting input terminal through which a free voltage is input, and a first output terminal through which the current sensing result is output;
A pixel compensation device including a first feedback capacitor connected between the first inverting input terminal and the first output terminal. According to claim 2,
The second integrator is,
an input resistance connected to the sensing line,
a second operational amplifier having a second inverting input terminal connected to the input resistor, a second non-inverting input terminal through which a free voltage is input, and a second output terminal through which the voltage sensing result is output;
A pixel compensation device including a second feedback capacitor connected between the second inverting input terminal and the second output terminal. According to claim 1,
The first integrator senses the drain-source current flowing through the driving element within a sensing period during which the driving element maintains a turn-on state,
The second integrator is a pixel compensation device that senses the source electrode voltage of the driving element increased according to the drain-source current during the sensing period in which the driving element remains turned on. According to claim 4,
The sensing period is allocated within a vertical blank period,
The vertical blank period is a pixel compensation device disposed between adjacent vertical active periods in which image data is written. According to claim 1,
The compensation department,
A first look-up table in which a first voltage change slope is stored is provided in advance, and the second sensing result data is mapped to the first look-up table to calculate the first compensation data for compensating for a change in electron mobility of the driving element. In addition to
A pixel compensation device for calculating the second compensation data for compensating for a change in the threshold voltage of the driving element based on the first sensing result data, the second sensing result data, and the first compensation data. According to claim 1,
The sensing unit,
a sample and hold unit that senses the source electrode voltage of the driving element changed according to the drain-source current; and
A pixel compensation device further comprising a third analog-to-digital converter that converts the voltage sensing result of the sample and hold unit into analog-digital and outputs third sensing result data. According to claim 7,
The sample and hold unit,
The source electrode voltage of the driving element increased according to the drain-source current during the first sensing period during which the driving element maintains the turn-on state, within the second sensing period during which the driving element maintains the turn-off state. A sensing pixel compensation device. According to claim 8,
The first sensing period and the second sensing period are allocated within a vertical blank period,
The vertical blank period is a pixel compensation device disposed between adjacent vertical active periods in which image data is written. According to claim 7,
The compensation department,
A second look-up table in which a second voltage change slope is stored is provided in advance, and the third sensing result data is mapped to the second look-up table to calculate the first compensation data to compensate for the change in electron mobility of the driving element. In addition to
A pixel compensation device for calculating the second compensation data for compensating for a change in the threshold voltage of the driving element based on the first sensing result data, the second sensing result data, and the first compensation data. A display panel equipped with a plurality of pixels;
A pixel compensation device according to any one of claims 1 to 10 that compensates for driving characteristics of the pixels;
a timing controller that corrects input image data based on the first compensation data and the second compensation data calculated by the pixel compensation device; and
An organic light emitting display device comprising a panel driver that writes the corrected input image data to the display panel.