KR102664733B1 - Light Emitting Display Device and Driving Method of the same - Google Patents

Abstract

The present invention provides a light emitting display device including a display panel, a driver, and a compensation circuit. The display panel displays images. The driving unit drives the display panel. The compensation circuit detects non-emission subpixels located in the surrounding area of the light-emitting subpixel on the display panel, and when a subpixel emitting at a gray level higher than the threshold is detected on the display panel, the surrounding non-emission subpixels and , a compensation data voltage is applied to subpixels on the display panel, including those driven by the black data voltage.

Description

Light emitting display device and driving method thereof {Light Emitting Display Device and Driving Method of the same}

The present invention relates to a light emitting display device and a method of driving the same.

As information technology develops, the market for display devices, which are a connecting medium between users and information, is growing. Accordingly, the use of display devices such as light emitting display (LED), quantum dot display (QDD), and liquid crystal display (LCD) is increasing.

The display devices described above include a display panel including subpixels, a driver that outputs a driving signal to drive the display panel, and a power supply that generates power to be supplied to the display panel or the driver.

The above display devices can display images by transmitting light or emitting light directly when driving signals, such as scan signals and data signals, are supplied to the subpixels formed on the display panel. .

Meanwhile, among the display devices described above, the light emitting display device has many advantages such as electrical and optical characteristics such as fast response speed, high brightness, and wide viewing angle, as well as mechanical characteristics that can be implemented in a flexible form. However, the light emitting display device still has room for improvement in terms of display panel configuration and driving method, so continuous research in this regard is needed.

The present invention, which aims to solve the problems of the above-mentioned background technology, prevents deterioration due to bias stress in subpixels that are driven under conditions that cause bias stress among non-light-emitting subpixels, and improves the driving reliability and lifespan of the device. It is done.

As a means of solving the above-described problem, the present invention provides a light emitting display device including a display panel, a driver, and a compensation circuit. The display panel displays images. The driving unit drives the display panel. The compensation circuit detects non-emission subpixels located in the surrounding area of the light-emitting subpixel on the display panel, and when a subpixel emitting at a gray level higher than the threshold is detected on the display panel, the surrounding non-emission subpixels and , a compensation data voltage is applied to subpixels on the display panel, including those driven by the black data voltage.

The compensation data voltage may be a voltage that turns on the driving transistor included in the non-light-emitting subpixel to prevent bias stress.

The organic light emitting diode included in the non-light emitting subpixel may emit light by turning on the driving transistor.

The compensation data voltage may have a higher level than the black data voltage used to display black on the display panel.

The compensation data voltage (Vblack') is calculated using Equation 1 below,

Vblack' = Vblack + Vcomp,

Vblack is the black data voltage used to display black on the display panel, and Vcomp is the compensation voltage added to the black data voltage, calculated using Equation 2 below,

Vcomp = Vturn-on - Vblack,

Vturn-on may be the voltage at the turn-on point of the driving transistor included in the subpixels on the display panel.

In another aspect, the present invention provides a light emitting display device including a display panel, a driver, and a compensation circuit. The display panel displays images. The driving unit drives the display panel. The compensation circuit unit applies a compensation data voltage having a higher level than the black data voltage used to display black on the display panel to the selected subpixel on the display panel to prevent bias stress of the driving transistor included in the selected subpixel.

The selected subpixel may include a non-emissive subpixel located in a peripheral area of the emissive subpixel that emits light on the display panel.

The selected subpixel may include a subpixel driven by a black data voltage among subpixels on the display panel.

In another aspect, the present invention provides a method of driving a light emitting display device. The driving method of the light emitting display device analyzes the input data signal and positions the subpixels that require bias stress compensation, including light emitting subpixels that emit light at a gray level higher than the threshold and non-light emitting subpixels that do not emit light, on the display panel. , and applying a compensation data voltage to a non-emission subpixel located in a peripheral area of the emitting subpixel and a subpixel driven by a black data voltage among subpixels on the display panel.

The compensation data voltage may have a higher level than the black data voltage used to display black on the display panel.

The step of detecting the position of the subpixel requiring bias stress compensation is the spatial extent of the light generated from the light-emitting subpixel to the light-emitting subpixel, and the spatial extent of the light emitted by the light-emitting subpixel at what gray level the adjacent non-light-emitting subpixel is. You can consider whether it will have an impact.

The present invention has the effect of preventing deterioration due to bias stress and improving device driving reliability and device lifespan by compensating for subpixels that are driven under conditions that cause bias stress among non-emission subpixels. In addition, the present invention has the effect of preventing distortion of the current-voltage characteristics ((I-V curve) of the driving transistor and improving display quality as well as realizing desired images. In addition, the present invention provides image analysis and spatial range setting. There is an effect of performing appropriate compensation for the bias stress of the driving transistor through setting compensation light emission conditions, etc.

1 is a block diagram schematically showing an organic light emitting display device according to an embodiment of the present invention.
FIG. 2 is a schematic configuration diagram of the subpixel shown in FIG. 1.
3 is an equivalent circuit diagram showing a subpixel including a compensation circuit according to an embodiment of the present invention.
FIGS. 4 and 5 are example diagrams of pixels that can be implemented based on the subpixels of FIG. 3.
Figure 6 is a block diagram briefly showing a compensation circuit of a subpixel according to an embodiment of the present invention.
Figure 7 is a block diagram briefly showing the sensing circuit shown in Figure 6.
Figure 8 is an example diagram of a line sensing method of the sensing circuit unit.
Figure 9 is a block diagram showing a timing control unit with a compensation circuit unit according to an embodiment of the present invention.
10 is a diagram for explaining operating conditions before applying the embodiment.
11 is a diagram for explaining operating conditions after applying the embodiment.
12 is a flowchart illustrating a compensation method according to an embodiment of the present invention.
Figure 13 is an exemplary diagram of a spatial range setting method according to an embodiment of the present invention.
14 and 15 are illustrations of a method for setting compensation light emission conditions according to an embodiment of the present invention.
Figure 16 is a graph of the threshold voltage change of the driving transistor before and after NBTiS improvement.
Figure 17 is a graph of color coordinate changes by gray level that can be seen before and after NBTiS improvement.
Figure 18 is a graph of luminance change by gray level that can be seen before and after NBTiS improvement.

Hereinafter, specific details for implementing the present invention will be described with reference to the attached drawings.

The display device according to the present invention can be implemented in a television, video player, personal computer (PC), home theater, automobile electric device, smartphone, etc., but is not limited thereto. The display device according to the present invention may be implemented as a light emitting display device (LED), a quantum dot display device (QDD), a liquid crystal display device (LCD), etc. Below, for convenience of explanation, a light-emitting display device that expresses images by directly emitting light is taken as an example. A light emitting display device may be implemented based on an inorganic light emitting diode or an organic light emitting diode. Below, for convenience of explanation, an implementation based on an organic light emitting diode will be described as an example.

In addition, the subpixel described below includes an n-type thin film transistor as an example, but it may also be implemented as a p-type thin film transistor or a combination of n-type and p-type. A thin film transistor is a three-electrode device including a gate, source, and drain. The source is an electrode that supplies carriers to the transistor. Within a thin film transistor, carriers begin to flow from a source. The drain is the electrode through which carriers go out in a thin film transistor. That is, in a thin film transistor, carriers flow from the source to the drain.

In the case of an n-type thin film transistor, 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 thin film transistor, since electrons flow from the source to the drain, the direction of current flows from the drain to the source. In contrast, in the case of a p-type thin film transistor, 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 thin film transistor, current flows from the source to the drain because holes flow from the source to the drain. However, the source and drain of a thin film transistor can change depending on the applied voltage. Reflecting this, in the following description, one of the source and drain will be described as the first electrode, and the other one of the source and drain will be described as the second electrode.

FIG. 1 is a block diagram schematically showing an organic light emitting display device according to an embodiment of the present invention, and FIG. 2 is a configuration diagram schematically showing the subpixel shown in FIG. 1.

As shown in Figures 1 and 2, the organic light emitting display device according to an embodiment of the present invention includes an image supply unit 110, a timing control unit 120, a scan driver 130, a data driver 140, and a display panel. 150 and a power supply unit 180 are included.

The image supply unit 110 (or host system) outputs various driving signals in addition to image data signals supplied from the outside or image data signals stored in internal memory. The image supply unit 110 may supply data signals and various driving signals to the timing control unit 120.

The timing control unit 120 includes a gate timing control signal (GDC) for controlling the operation timing of the scan driver 130, a data timing control signal (DDC) for controlling the operation timing of the data driver 140, and various synchronization signals ( Outputs the vertical synchronization signal (Vsync) and the horizontal synchronization signal (Hsync).

The timing control unit 120 supplies the data signal DATA supplied from the image supply unit 110 along with the data timing control signal DDC to the data driver 140. The timing control unit 120 may be formed in the form of an integrated circuit (IC) and mounted on a printed circuit board, but is not limited to this.

The scan driver 130 outputs a scan signal (or scan voltage) in response to a gate timing control signal (GDC) supplied from the timing controller 120. The scan driver 130 supplies scan signals to subpixels included in the display panel 150 through scan lines GL1 to GLm. The scan driver 130 may be formed in the form of an IC or directly on the display panel 150 using a gate in panel method, but is not limited thereto.

The data driver 140 samples and latches the data signal (DATA) in response to the data timing control signal (DDC) supplied from the timing control unit 120 and converts the digital data signal into analog data based on the gamma reference voltage. Converts to voltage and outputs.

The data driver 140 supplies data voltage to subpixels included in the display panel 150 through the data lines DL1 to DLn. The data driver 140 may be formed in the form of an IC and mounted on the display panel 150 or on a printed circuit board, but is not limited thereto.

The power supply unit 180 generates and outputs a high-potential first power source (EVDD) and a low-potential second power source (EVSS) based on an external input voltage. The power supply unit 180 provides not only the first and second power supplies (EVDD, EVSS) but also the voltage (e.g., scan high voltage, scan low voltage) required to drive the scan driver 130 or the data driver 140. Voltages (drain voltage, half-drain voltage), etc. can be generated and output.

The display panel 150 includes a drive signal including a scan signal and a data voltage output from a driver including the scan driver 130 and a data driver 140, and first and second power outputs from the power supply 180 ( Displays images in response to EVDD, EVSS). Subpixels of the display panel 150 directly emit light.

The display panel 150 may be manufactured based on a rigid or flexible substrate such as glass, silicon, or polyimide. And the subpixels that emit light may be composed of pixels containing red, green, and blue, or pixels containing red, green, blue, and white.

For example, one subpixel (SP) includes a pixel circuit (PC) including a switching transistor (SW), a driving transistor, a storage capacitor, and an organic light emitting diode. The subpixel (SP) used in organic light emitting displays emits light directly, so the circuit configuration is complex. In addition, there are various compensation circuits that compensate for the deterioration of not only the organic light-emitting diode that emits light, but also the driving transistor that supplies driving current to the organic light-emitting diode. Therefore, please refer to the fact that the pixel circuit (PC) included in the subpixel (SP) is shown in block form.

Meanwhile, in the above description, the timing control unit 120, scan driver 130, data driver 140, etc. were described as if they were individual components. However, depending on the implementation method of the light emitting display device, one or more of the timing control unit 120, scan driver 130, and data driver 140 may be integrated into one IC.

Figure 3 is an equivalent circuit diagram showing a subpixel including a compensation circuit according to an embodiment of the present invention, and Figures 4 and 5 are example diagrams of pixels that can be implemented based on the subpixel of Figure 3.

As shown in FIG. 3, the subpixel including the compensation circuit according to an embodiment of the present invention includes a switching transistor (SW), a sensing transistor (ST), a driving transistor (DT), a capacitor (CST), and an organic light emitting diode. (OLED).

The switching transistor SW has a gate electrode connected to the 1A scan line GL1a, a first electrode connected to the first data line DL1, and a second electrode connected to the gate electrode of the driving transistor DT. The driving transistor (DT) has a gate electrode connected to the capacitor (CST), a first electrode connected to the first power line (EVDD), and a second electrode connected to the anode electrode of the organic light emitting diode (OLED).

The capacitor CST has a first electrode connected to the gate electrode of the driving transistor DT and a second electrode connected to the anode electrode of the organic light emitting diode (OLED). The organic light emitting diode (OLED) has an anode connected to the second electrode of the driving transistor (DT) and a cathode electrode connected to the second power line (EVSS). The sensing transistor (ST) has a gate electrode connected to the 1B scan line (GL1b), a first electrode connected to the sensing line (VREF), and a second electrode connected to the anode electrode of the organic light emitting diode (OLED), which is a sensing node. .

The sensing transistor (ST) is a compensation circuit added to compensate for the deterioration or threshold voltage of the driving transistor (DT) and organic light-emitting diode (OLED). The sensing transistor (ST) acquires the sensing value through the sensing node defined between the driving transistor (DT) and the organic light-emitting diode (OLED). The sensing value obtained from the sensing transistor (ST) is transmitted to an external compensation circuit provided outside the subpixel through the sensing line (VREF).

The 1A scan line (GL1a) connected to the gate electrode of the switching transistor (SW) and the 1B scan line (GL1b) connected to the gate electrode of the sensing transistor (ST) have a separate structure or a common structure as shown. can be taken. The gate electrode common connection structure can reduce the number of scan lines and, as a result, prevent a decrease in the aperture ratio due to the addition of a compensation circuit.

As shown in FIGS. 4 and 5, the first to fourth subpixels SP1 to SP4 including a compensation circuit according to an embodiment of the present invention may be defined to form one pixel. At this time, the first to fourth subpixels (SP1 to SP4) may be arranged in the order of emitting red, green, blue, and white, respectively, but are not limited to this.

As in the first example of FIG. 4, the first to fourth subpixels (SP1 to SP4) including the compensation circuit are connected to share one sensing line (VREF), and the first to fourth data lines (DL1) ~ DL4) may have a separate and connected structure.

As in the second example of FIG. 5, the first to fourth subpixels (SP1 to SP4) including the compensation circuit are connected to share one sensing line (VREF), and each two subpixels are connected to one data line. It can have a shared connected structure. For example, the first and second subpixels SP1 and SP2 may share the first data line DL1, and the third and fourth subpixels SP3 and SP4 may share the second data line DL2. .

However, FIGS. 4 and 5 only show two examples, and the present invention can also be applied to display panels having subpixels of other structures not previously shown or described. Additionally, the present invention can be applied to a structure with a compensation circuit in a subpixel or a structure without a compensation circuit in a subpixel.

FIG. 6 is a block diagram briefly showing a compensation circuit of a subpixel according to an embodiment of the present invention, FIG. 7 is a block diagram briefly showing the sensing circuit shown in FIG. 6, and FIG. 8 is an example of a line sensing method of the sensing circuit. It is also a degree.

As shown in FIGS. 6 and 7, the data drivers 140a and 104b operate the subpixel SP to compensate for the data signal output from the first circuit unit 140a and the timing control unit, which outputs a data voltage to the subpixel SP. It includes a second circuit unit 140b that senses (SP).

The first circuit unit 140a includes a digital-to-analog conversion circuit unit 141 (DAC) that can convert the digital data signal supplied from the timing control unit into an analog data voltage (Vdata) and output it. The output terminal of the first circuit unit 140a is connected to the first data line DL1.

The second circuit unit 140b includes a voltage output switch unit (SW1), a sampling switch unit (SW2), and a sensing circuit unit 143. The voltage output switch unit (SW1) operates in response to the charging control signal (PRE). The sampling switch unit (SW2) operates in response to the sampling control signal (SAMP).

The voltage output switch unit (SW1) serves to output the initialization voltage generated by the voltage source (VREFF) through the first sensing line (VREF1). The initialization voltage generated by the voltage source (VREFF) may be generated as a voltage between the first power source (high potential voltage) and the second power source (low potential voltage), but is usually generated as a voltage close to the second power source. For example, the switch unit (SW1) for voltage output is simply shown in the form of a switch, but is not limited to this and may be implemented as an active element, etc.

The sampling switch unit (SW2) serves to sense the subpixel (SP) through the first sensing line (VREF1). The sampling switch unit (SW2) operates to sense device characteristics including the threshold voltage of the organic light-emitting diode (OLED), the threshold voltage or mobility of the driving transistor (DR), etc. using a sampling method. For example, the sampling switch unit (SW2) is also shown simply in the form of a switch, but is not limited to this and may be implemented as an active element, etc.

When the sampling switch unit (SW2) is turned on, the sensing circuit unit 143 senses the threshold voltage of the organic light emitting diode (OLED) and the threshold voltage or mobility of the driving transistor (DR) through the first sensing line (VREF1). It plays a role in integration and sampling. To this end, the sensing circuit unit 143 includes an integration circuit unit (CI), a sample & hold unit (SH), and an analog-to-digital conversion circuit (ADC) as shown in FIG. 7 .

The integration circuit unit (CI) includes a reset switch (RST), an integration capacitor (Cfb), an amplifier (AMP), etc. The integration circuit unit (CI) serves to integrate the current charged in the first sensing line (VREF1) and output an integrated value. The amplifier (AMP) includes an inverting terminal (-) that receives the current of the first sensing line (VREF1), a non-inverting terminal (+) that receives the reference voltage (VRE), and an output terminal that outputs an integral value. The integrating capacitor (Cfb) and reset switch (RST) are connected between the inverting terminal (-) and the output terminal of the amplifier (AMP).

The sample & hold unit (SH) serves to sample the integral value output from the integration circuit unit (CI) and output the accumulated value. The sample & hold unit (SH) may be composed of passive elements such as switches and capacitors to sample and accumulate integral values, but is not limited to this.

The analog-to-digital conversion circuit (ADC) serves to convert and output the accumulated value in analog form output from the sample & hold unit (SH) into the accumulated value in digital form. The digital output value output from the analog-to-digital conversion circuit (ADC) corresponds to the sensing value (SDATA) obtained by sensing the first sensing line (VREF1).

The compensation circuit unit 160 includes an image analysis unit 165 and a compensation value generation unit 167. The image analysis unit 165 functions to analyze the sensing value (SDATA) output from the sensing circuit unit 143 as well as the data signal input from the outside.

The compensation value generator 167 determines the degree of deterioration of the sensed element in response to the analysis result output from the image analysis unit 165 and generates a compensation value necessary for compensation. Descriptions related to the image analysis unit 165 and compensation value generation unit 167 are discussed in more detail below.

As shown in FIG. 8(a), the sensing circuit unit 143 sets one scan line arranged in the horizontal direction of the display panel 150 as a sensing line, and the sensing line connected to the subpixels Through these, the characteristics of the device can be sensed.

As shown in FIG. 8(b), the sensing circuit unit 143 sets a plurality of scan lines arranged in the horizontal direction of the display panel 150 as sensing lines, and senses lines connected to subpixels. Through these, the characteristics of the device can be sensed. However, this is only one example, and the sensing circuit unit 143 can sense the characteristics of devices included in subpixels under various conditions, such as block sensing or random sensing.

FIG. 9 is a block diagram showing a timing control unit having a compensation circuit unit according to an embodiment of the present invention, FIG. 10 is a diagram for explaining operating conditions before applying the embodiment, and FIG. 11 is a diagram showing operating conditions after applying the embodiment. This is a drawing to explain.

As shown in FIG. 9, the compensation circuit unit 160 according to an embodiment of the present invention may be included within the timing control unit 120. However, this is just one example, and the compensation circuit unit 160 may be included inside the image supply unit or the data driver unit. Additionally, the compensation circuit unit 160 according to an embodiment of the present invention can be applied to a display panel including subpixels without a compensation circuit as well as subpixels having a compensation circuit as shown in FIGS. 6 to 8.

The timing control unit 120 includes a data reception unit 121, a compensation circuit unit 160, and a data output unit 128. The timing control unit 120 analyzes and compensates for the data signal (DATA) input from the outside and outputs a non-compensated data signal (DATA) and a compensated data signal (CDATA). The uncompensated data signal (DATA) corresponds to a data signal that does not require compensation, and the compensated data signal (CDATA) corresponds to a compensated data signal.

The compensation circuit unit 160 includes an image analysis unit 165 and a compensation value generation unit 167.

The image analysis unit 165 analyzes the input data signal (DATA) and distinguishes between data signals of light-emitting subpixels that emit light and data signals of non-light-emitting subpixels that do not emit light on the display panel. The image analysis unit 165 detects data signals of non-emission subpixels through a data analysis process.

The compensation value generator 167 receives the data signal information of the non-emission sub-pixel from the image analysis unit 165, generates a weak compensation value, and provides it to the data signal of the non-emission sub-pixel. By linking the image analysis unit 165 and the compensation value generation unit 167, the portion corresponding to the data signal of the non-emission subpixel in the input data signal (DATA) is generated as a compensation data signal (CDATA).

Afterwards, the compensation data signal (CDATA) is converted into a compensation data voltage by the data driver and applied to the display panel. The compensation data voltage generated in this way slightly turns on the driving transistors of the subpixels, thereby relieving bias stress that the driving transistors may continuously receive.

Typically, the driving transistor included in the subpixel may be exposed to NBTiS (Negative Bias Temperature Illumination Stress). This bias stress appears most prominently when light-emitting subpixels that emit light and non-emission subpixels that do not emit light are mixed on the display panel (especially when both are located adjacent to each other).

Since non-emissive subpixels exposed to these mixed conditions are sensitive to ambient light due to NBTiS characteristics, the current-voltage characteristics ((I-V Curve) of the driving transistor are distorted, making it difficult to implement the desired image. Therefore, these conditions The more there is, the lower the display quality of the display panel, which also affects the lifespan of the device.

However, as in the embodiment of the present invention, by generating a compensation data voltage and slightly turning on the driving transistors of the non-light-emitting subpixels, the bias stress condition of the driving transistor can be alleviated. For example, the negative bias received by the n-type driving transistor moves to positive bias.

[Operating conditions before applying the embodiment]

As shown in FIG. 10, when the embodiment is not applied, the red sub-pixel (SPR) corresponds to the light-emitting sub-pixel and emits light from the organic light-emitting diode (OLED), but the green sub-pixel (SPG) adjacent to it corresponds to the light-emitting sub-pixel. corresponds to a non-emissive subpixel, so no light is emitted from the organic light emitting diode (OLED).

To enable the above conditions, the driving transistor (DT) of the red sub-pixel (SPR) remains turned on to generate a driving current to drive the organic light-emitting diode (OLED), but the driving transistor (DT) of the green sub-pixel (SPG) remains turned on. ) remains in the turn-off state. If these driving conditions are prolonged, the driving transistor (DT) of the green subpixel (SPG) is continuously exposed to NBTiS characteristics, and the current-voltage characteristics ((I-V Curve) of the driving transistor are distorted, making it difficult to implement the desired image. is triggered.

[Operating conditions after applying the embodiment]

As shown in FIG. 11, according to the application of the embodiment, the red subpixel (SPR) corresponds to the light emitting subpixel and emits light from the organic light emitting diode (OLED), and the green subpixel (SPG) adjacent to it corresponds to the light emitting subpixel. Although it corresponds to a light-emitting subpixel, weak light is emitted from the organic light-emitting diode (OLED) as it receives a compensation data voltage. This light is close to black and corresponds to a low-gray light emission amount that is so weak that it is not visible to humans.

To enable the above conditions, the driving transistor (DT) of the red subpixel (SPR) and the driving transistor (DT) of the green subpixel (SPG) are maintained in a turn-on state. However, the driving transistor (DT) of the green subpixel (SPG) is turned on because it receives the compensation data voltage. That is, the driving transistor (DT) of the green subpixel (SPG) receives only a turn-on voltage (Vgs) small enough for the current (Ids) to flow.

Accordingly, the driving transistor DT of the green subpixel (SPG) is subject to a positive bias condition rather than a negative bias condition.

As can be seen through the examples and descriptions of FIGS. 10 and 11, the embodiment can prevent a problem in which the driving transistor of a specific subpixel is continuously exposed to NBTiS characteristics. In addition, the embodiment can prevent the problem that the current-voltage characteristics ((I-V Curve) of the driving transistor are distorted due to continuous exposure to NBTiS characteristics, making it difficult to implement a desired image. In other words, the present invention can prevent the problem of making it difficult to implement a desired image. Due to the NBTiS characteristics applied to the driving transistor, it is possible to prevent the threshold voltage (Vth) from moving (negative shift) in a specific direction, for example, in the negative direction.

FIG. 12 is a flowchart for explaining a compensation method according to an embodiment of the present invention, FIG. 13 is an exemplary diagram of a spatial range setting method according to an embodiment of the present invention, and FIGS. 14 and 15 are diagrams for explaining a compensation method according to an embodiment of the present invention. These are examples of how to set compensation light emission conditions.

As shown in Figures 12 to 15, the compensation method according to an embodiment of the present invention includes a voltage measurement and storage step for each color (S110), a color-specific compensation data voltage calculation and storage step (S120), and setting conditions for NBTiS occurrence. It includes a step (S130), an NBTiS prevention driving condition tracking step (S140), and a compensation data voltage application step (S150).

The voltage measurement and storage step for each color (S110) uses a luminance meter to measure the voltage at the turn-on time of the driving transistor (Vturn-on) and the black data voltage (Vblack) for each color such as red, green, blue, and white subpixels. This is the step to save it. If the optical compensation step for gamma correction is preceded, a luminance-voltage lookup table obtained in advance can be used. That is, this step may be replaced by an optical compensation step. Meanwhile, the black data voltage (Vblack) is a voltage used to display black on the display panel and corresponds to a voltage of 0V or close to 0V.

The color-specific compensation data voltage calculation and storage step (S120) is based on the voltage at the turn-on time of the driving transistor (Vturn-on) and the black data voltage (Vblack) obtained previously. This is the step of calculating the compensation voltage (Vcomp) and storing it. This is to include subpixels driven by the black data voltage in the compensation target because they can also experience bias stress.

The equation for calculating the compensation voltage (Vcomp) can be expressed as Vcomp = Vturn-on - Vblack. The compensation voltage (Vcomp) refers to a value calculated by the compensation circuit unit included within the timing control unit.

The step of setting conditions for NBTiS occurrence (S130) includes setting a spatial range and setting a compensation light emission amount. The step of setting the spatial range is a step prepared to consider the spatial range that light generated from the emitting sub-pixel can affect the non-emitting sub-pixel.

FIG. 13(a) shows an example in which subpixels are divided into red blocks (RB), white blocks (WB), green blocks (GB), and blue blocks (BB) on a display panel and emit light. Figure 13(b) shows an example of setting the spatial range by defining the surrounding area of the emitting subpixels as a compensation area (CA) requiring compensation.

Figure 13(c) shows compensation light emission in the red block (RB), white block (WB), green block (GB), and blue block (BB) composed of light-emitting subpixels and the compensation light emission area (CE) around them. This shows an example of the subpixels being displayed on the display panel. Meanwhile, in Figure 13(c), the compensation emission area (CE) is shown as a white block to improve identification. However, as described above, if the compensation method according to the embodiment of the present invention is followed, the light is emitted so weakly that it is not visible to humans.

As can be seen from the example of FIG. 13, by setting the spatial range, it is possible to determine how many adjacent non-emitting subpixels from the emitting subpixels should be included in the compensation range. However, the example of FIG. 13 is only one example, and the spatial range may vary depending on the shape of the pattern formed by the subpixels emitting light on the display panel, the degree of bias stress received by the device, and the deterioration characteristics of the device.

Therefore, the present invention can prevent the phenomenon of shifting the threshold voltage of the driving transistor of the non-emitting subpixel around the image by using a spatial range setting method that takes into account that the light of the emitting subpixel can affect the non-emitting subpixel. there is. Additionally, the input image information may be analyzed, the image periphery may be detected, for example, as a halo, and then a compensation data voltage may be applied. Additionally, non-emissive subpixels that are not affected by light actually remain black, so the contrast ratio (CR) can be maintained even with compensated light emission.

The step of setting the compensation light emission condition is a step prepared to set a limit on the size of the data voltage that light generated from the light-emitting subpixel can apply to the non-light-emitting subpixel.

FIG. 14(a) shows an example in which a red subpixel (R) emits light at low gray level on a black background screen on a display panel. And FIG. 14(b) shows an example in which the red subpixel R emits light at a low gray level and no compensation is made because the effect on the surrounding subpixels is minimal.

In this way, when a subpixel emits light at a low gray level, the effect on other subpixels may be small. Therefore, according to an embodiment of the present invention, if the NBTiS generation condition is not satisfied, the compensation data voltage may not be applied to the surrounding subpixels (G, B, W).

Figure 15(a) shows an example in which a red subpixel (R) emits light at high gray level on a black background screen on a display panel. And FIG. 15(b) shows an example of compensation because the red subpixel R emits light at a high gray level and has an effect on surrounding subpixels.

In this way, when a subpixel emits light at a high gray level, the impact on other subpixels may be significant. Therefore, according to an embodiment of the present invention, if the NBTiS generation condition is satisfied, the compensation data voltage can be applied to the surrounding subpixels (G, B, W).

In the present invention, the middle gray scale and high gray scale, excluding the low gray scale, can be set to a gray scale higher than a threshold value, and subpixels around the subpixels that emit light at a gray scale higher than the threshold value can be compensated. However, it is particularly desirable to perform this on subpixels surrounding subpixels that emit light at high gray levels. This is because the bias stress experienced by the subpixels around the subpixels that emit light at high gray levels is high, and even if there are subpixels that emit weakly due to the compensation data voltage, they are not easily recognized around the subpixels that emit light at high gray levels. am.

As can be seen through the examples of FIGS. 14 and 15, by setting the compensation light emission conditions, it is possible to determine whether or not to apply the compensation data voltage to the adjacent non-emission subpixel when the light emitting subpixel emits light at what gray level. . However, the example of FIGS. 14 and 15 is just one example, and the compensation light emission conditions may vary depending on the characteristics of the device, the level of light energy, and the threshold voltage characteristics.

Therefore, the present invention can set the light amount (=luminance of the emitting subpixel) of the negative bias operation condition of the driving transistor by considering the compensated light emission condition of the non-emitting subpixel according to the gray level of the emitting subpixel. In addition, compensation can be performed by applying a compensation data voltage to the non-emission subpixel when the light-emitting subpixel has a certain luminance, that is, a certain voltage or more.

The NBTiS prevention driving condition tracking step (S140) is a tracking step for identifying the location of a subpixel to which a compensation data voltage is to be applied in response to the NBTiS prevention driving condition and selecting a subpixel requiring compensation. NBTiS prevention driving conditions refer to spatial range conditions set through image analysis and compensation light emission conditions based on real-time input data signals (data voltage) to determine the location of non-emission subpixels that require compensation light emission.

The compensation data voltage application step (S150) is a step of preparing and applying a compensation data voltage in response to the position of a non-emission subpixel that requires compensation light emission. To maintain color coordinates and luminance, the compensation data voltage can be expressed as Vblack' = Vblack + Vcomp by adding the compensation voltage to the black data voltage to be applied to the non-emission subpixel. According to this, the compensation data voltage is the sum of the black data voltage (Vblack) and the compensation voltage (Vcomp) and can be defined as the compensation black data voltage (Vblack'). And the compensation black data voltage (Vblack') may be defined as a voltage at a higher level than the black data voltage (Vblack).

In the compensation method according to an embodiment of the present invention, the step of measuring and storing the voltage for each color (S110), the step of calculating and storing the compensation data voltage for each color (S120), and the step of setting conditions for NBTiS occurrence (S130) can be set only once initially. there is. And the remaining NBTiS prevention driving condition tracking step (S140) and compensation data voltage application step (S150) may have their set values changed depending on the device environment, driving method, driving environment, etc. during driving. However, this is only one example and the present invention is not limited to this.

Figure 16 is a graph of the change in threshold voltage of the driving transistor that can be seen before and after NBTiS improvement, Figure 17 is a graph of color coordinate change by gray level that can be seen before and after NBTiS improvement, and Figure 18 is a graph of luminance change by gray level that can be seen before and after NBTiS improvement. It's a graph.

Referring to FIGS. 16 to 18, which are simulation results that can determine the results depending on whether the embodiment of the present invention is applied or not, there is no significant change in color coordinates and luminance, but the threshold voltage change (ΔVth) of the driving transistor according to time (t) ) can be seen to have decreased quite steadily. Therefore, the present invention can have a remarkable effect in improving the NBTiS characteristics of the driving transistor.

The present invention has the effect of preventing deterioration due to bias stress and improving device driving reliability and device life by compensating for subpixels that are driven under conditions that cause bias stress among non-emission subpixels. In addition, the present invention has the effect of preventing distortion of the current-voltage characteristics ((I-V curve) of the driving transistor and improving display quality as well as realizing desired images. In addition, the present invention provides image analysis and spatial range setting. There is an effect of performing appropriate compensation for the bias stress of the driving transistor through setting compensation light emission conditions, etc.

Although embodiments of the present invention have been described with reference to the accompanying drawings, the technical configuration of the present invention described above can be modified by those skilled in the art in the technical field to which the present invention belongs in other specific forms without changing the technical idea or essential features of the present invention. You will understand that it can be done. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive. In addition, the scope of the present invention is indicated by the claims described later rather than the detailed description above. In addition, the meaning and scope of the patent claims and all changes or modified forms derived from the equivalent concept should be construed as being included in the scope of the present invention.

120: timing control unit 140: data driver
150: display panel 160: compensation circuit unit
143: sensing circuit unit 165: image analysis unit
167: Compensation value generator DT: Driving transistor

Claims (14)

A display panel that displays images;
a driving unit that drives the display panel; and
Detecting a non-emission subpixel located in a surrounding area of a light-emitting subpixel on the display panel, and detecting a subpixel emitting light at a gray level higher than a threshold on the display panel, non-emission subpixels around the display panel; a compensation circuit unit that applies a compensation data voltage including a sub-pixel driven by a black data voltage among the sub-pixels on the display panel;
The compensation data voltage is applied to the non-emission subpixel as a compensation black data voltage by adding a compensation voltage to the black data voltage. According to paragraph 1,
The compensation data voltage is
A light emitting display device that is a voltage that turns on a driving transistor included in the non-light emitting subpixel to prevent bias stress. According to paragraph 2,
The organic light emitting diode included in the non-light emitting subpixel is
A light emitting display device that emits light when the driving transistor is turned on. According to paragraph 1,
The compensation data voltage is
A light emitting display device having a level higher than the black data voltage used to display black on the display panel. According to paragraph 1,
The compensation data voltage (Vblack') is calculated using Equation 1 below,
Vblack' = Vblack + Vcomp,
The Vblack is a black data voltage used to display black on the display panel, and the Vcomp is a compensation voltage added to the black data voltage, calculated by Equation 2 below,
Vcomp = Vturn-on - Vblack,
The Vturn-on is a voltage at the turn-on point of a driving transistor included in the subpixels on the display panel. A display panel that displays images;
a driving unit that drives the display panel; and
Compensation for preventing bias stress of a driving transistor included in the selected subpixel by applying a compensation data voltage having a higher level than the black data voltage used to display black on the display panel to the selected subpixel. Includes a circuit part,
The subpixel includes a light-emitting subpixel that emits light at a gray level higher than a threshold on the display panel, and a non-light-emitting subpixel that does not emit light and is located in a peripheral area of the light-emitting subpixel,
The compensation data voltage is applied to the non-emission subpixel as a compensation black data voltage by adding a compensation voltage to the black data voltage. delete According to clause 6,
The selected subpixel is
A light emitting display device including a subpixel driven by a black data voltage among subpixels on the display panel. Analyzing the input data signal, detecting the positions of subpixels requiring bias stress compensation, including light-emitting subpixels that emit light at a gray level higher than a threshold and non-light-emitting subpixels that do not emit light, on the display panel; and
Applying a compensation data voltage to a non-emission subpixel located in a peripheral area of the light emitting subpixel and a subpixel driven by a black data voltage among subpixels on the display panel,
A method of driving a light emitting display device in which the compensation data voltage is applied to the non-emission subpixel as a compensation black data voltage by adding a compensation voltage to the black data voltage. According to clause 9,
The compensation data voltage is
A method of driving a light emitting display device having a level higher than the black data voltage used to display black on the display panel. According to clause 9,
The step of detecting the position of a subpixel requiring bias stress compensation is
The light generated from the light-emitting subpixel exceeds a limit on the size of the data voltage applied to the non-light-emitting subpixel,
A method of driving a light-emitting display device, wherein when the light-emitting subpixel emits light at a gray level higher than a threshold, an adjacent non-light-emitting subpixel is set as a subpixel requiring bias stress compensation. A display panel that displays images through subpixels including light emitting diodes and driving transistors;
a driving unit that drives the display panel; and
Detecting a non-emission subpixel located in a surrounding area of a light-emitting subpixel on the display panel, and detecting a subpixel emitting light at a gray level higher than a threshold on the display panel, non-emission subpixels around the display panel; a compensation circuit unit that applies a compensation data voltage including a sub-pixel driven by a black data voltage among the sub-pixels on the display panel;
A light emitting display device in which the driving transistor of the non-emission subpixel is turned on weaker than the driving transistor of the light emitting subpixel by the compensation data voltage, thereby applying a positive bias. A display panel that displays images through subpixels including light emitting diodes and driving transistors;
a driving unit that drives the display panel; and
Compensation for preventing bias stress of a driving transistor included in the selected subpixel by applying a compensation data voltage having a higher level than the black data voltage used to display black on the display panel to the selected subpixel. Includes a circuit part,
The subpixel includes a light-emitting subpixel that emits light at a gray level higher than a threshold on the display panel, and a non-light-emitting subpixel that does not emit light and is located in a peripheral area of the light-emitting subpixel,
A light emitting display device in which the driving transistor of the non-emission subpixel is turned on weaker than the driving transistor of the light emitting subpixel by the compensation data voltage, thereby applying a positive bias. A method of driving a light emitting display device including a display panel that displays an image through subpixels including a light emitting diode and a driving transistor, comprising:
Analyzing the input data signal, detecting the positions of subpixels requiring bias stress compensation, including light-emitting subpixels that emit light at a gray level higher than a threshold and non-light-emitting subpixels that do not emit light, on the display panel; and
Applying a compensation data voltage to a non-emission subpixel located in a peripheral area of the light emitting subpixel and a subpixel driven by a black data voltage among subpixels on the display panel,
A method of driving a light emitting display device in which the driving transistor of the non-emission subpixel is turned on weaker than the driving transistor of the light emitting subpixel by the compensation data voltage, thereby applying a positive bias.

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