KR102461693B1 - Organic light emitting diode display device and driving method thereof - Google Patents

Abstract

The present invention relates to an organic light emitting diode display device and a driving method thereof, which compensates for the measured conductance deviation of the driving TFT by changing the duty ratio of the emission control signal EM while maintaining the gate voltage of the driving TFT constant. Using a first compensation value and a second compensation value for compensating for a threshold voltage deviation of the driving TFT measured by applying a voltage in an optimal measurement region set to a voltage range greater than or equal to the threshold voltage of the driving TFT to the gate of the driving TFT Modulates pixel data. According to the present invention, image quality can be improved by compensating for deviation in driving characteristics of the driving TFT without complicating the pixel structure, and the measurement and compensation time for driving characteristics of the driving TFT can be shortened.

Description

Organic light emitting diode display and driving method thereof

The present invention relates to an organic light emitting diode display for compensating for a change in driving characteristics of a pixel using an external compensation method and a driving method thereof.

Since the organic light emitting diode display is a self-luminous device, it consumes less power and can be made thinner than a liquid crystal display that requires a backlight. In addition, the organic light emitting diode display has a wide viewing angle and a fast response speed. The organic light emitting diode display is expanding its market while competing with the liquid crystal display as process technology has been advanced to the level of large-screen mass production.

Pixels of the organic light emitting diode display include organic light emitting diodes (hereinafter, referred to as "OLEDs"), which are self-luminous devices. In OLED, a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL) between the anode and the cathode ) and an organic compound layer such as an electron injection layer (EIL) are stacked. An organic light emitting diode display reproduces an input image by using a phenomenon in which light is emitted when electrons and holes are combined in an organic material layer in an OLED of a pixel by flowing a current through a fluorescent or phosphorescent organic material thin film.

The organic light emitting diode display may be variously classified according to a type of a light emitting material, a light emitting method, a light emitting structure, a driving method, and the like. The organic light emitting diode display is divided into fluorescence emission and phosphorescence emission according to a light emitting method, and may be divided into a top emission structure and a bottom emission structure according to a light emitting structure. In addition, the organic light emitting diode display may be divided into a passive matrix OLED (PMOLED) and an active matrix OLED (AMOLED) according to a driving method.

Pixels of the OLED display include a driving TFT (Thin Film Transistor) that controls the driving current flowing through the OLED according to the data of the input image.

The TFTs of the pixels are manufactured in a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) structure. Characteristics of the driving TFT such as threshold voltage and mobility should be designed to be the same in all pixels, but the characteristics of the driving TFT are non-uniform depending on process deviation, driving time, driving environment, and the like. Accordingly, a technique for compensating for a characteristic change of a driving TFT is applied to an OLED display device. The change in the characteristics of the driving TFT means a change in the characteristics of the driving TFT such as the threshold voltage and mobility of the driving TFT.

A compensation method for compensating for a change in driving characteristics of a pixel in an OLED display is divided into an internal compensation method and an external compensation method.

The internal compensation method automatically compensates the threshold voltage deviation between the driving TFTs inside the pixel circuit. Since the current flowing through the OLED must be determined regardless of the threshold voltage of the driving TFT for internal compensation, the configuration of the pixel circuit becomes complicated. Moreover, the internal compensation method is difficult to compensate for the mobility deviation between the driving TFTs.

The external compensation method senses electrical characteristics (threshold voltage, mobility) of the driving TFTs, and compensates for the electrical characteristic deviation by modulating pixel data in a compensation circuit outside the display panel based on the sensing result. Recently, studies on these external compensation methods have been actively conducted. A conventional external compensation method directly receives a sensing voltage from each pixel through a sensing line connected to the pixels in a display panel, converts the sensing voltage into digital sensing data, and transmits the sensing voltage to a timing controller. The timing controller compensates for variations in electrical characteristics of the driving TFT by modulating digital video data of an input image based on the digital sensing data.

In order to implement the existing internal compensation method and the external compensation method, the pixel structure and operation are complicated. The complex pixel structure increases the defect rate of the display panel to lower the yield, and it is difficult to improve the resolution of the display panel because the pixel aperture ratio cannot be secured.

The present invention provides an OLED display device capable of improving image quality by compensating for deviation in driving characteristics of a driving TFT without complicating a pixel structure, and shortening a driving characteristic measurement and compensation time of a driving TFT, and a driving method thereof.

The OLED display device of the present invention includes a driving TFT for controlling current flowing through an organic light emitting diode, a first switch TFT for supplying a data voltage input through a data line in response to a scan pulse to the gate of the driving TFT, and an emission control signal. and a third switch TFT for connecting a current path between the driving TFT and the anode of the organic light emitting diode in response, and at least one capacitor connected between the gate of the driving TFT.

The OLED display includes a modulator that modulates the pixel data by adding or multiplying pixel data of an input image by adding or multiplying preset first and second compensation values, and a display panel that writes the data modulated by the modulator to the pixels It includes a driving circuit.

The first compensation value is set to a value for compensating for a conductance deviation of the driving TFT determined according to the mobility and the channel ratio of the driving TFT. The second compensation value is set to a value that compensates for a threshold voltage deviation of the driving TFT.

The driving method of the OLED display includes setting a first compensation value for compensating for a measured conductance deviation of the driving TFT by changing a duty ratio of the emission control signal while maintaining a gate voltage of the driving TFT constant. , setting a second compensation value for compensating for a threshold voltage deviation of the driving TFT measured by applying two voltages within an optimal measurement region set to a voltage range equal to or higher than the threshold voltage of the driving TFT to the gate of the driving TFT; modulating the pixel data by adding or multiplying the first and second compensation values to pixel data of an input image, and writing the modulated data to the pixels.

The present invention measures the conductance deviation of the driving TFT based on the measured luminance change of the pixel while changing the duty ratio of the emission control signal while maintaining the gate voltage of the driving TFT constant, and a voltage range above the threshold voltage of the driving TFT. The threshold voltage deviation of the driving TFT is measured based on the measured luminance change of the pixel by applying two voltages within the optimal measurement region set to , to the gate of the driving TFT. The present invention modulates pixel data by deriving first and second compensation values for allowing the same current to flow in the pixels based on the measured characteristic deviation of the driving TFT between the pixels. As a result, according to the present invention, image quality can be improved by compensating for deviation in driving characteristics of a driving TFT without complicating the pixel structure in an OLED display device, and a measurement and compensation time for driving characteristics of the driving TFT can be shortened.

The present invention can compensate for the characteristic deviation of the driving TFT in each pixel without the need for a sensing line, a sensing switch, an analog-digital converter (ADC) connected to the sensing line, a sampling capacitor, etc., which were required in the existing external compensation method. Components necessary for the external compensation method can be removed from the display panel and the drive IC (Integrated Circuits).

1 is a flowchart illustrating a method of driving an OLED display according to an embodiment of the present invention.
2 and 3 are diagrams illustrating a luminance measuring means of a pixel used when measuring a characteristic deviation of a driving TFT in the pixels using a camera or an optical scan module.
4 and 5 are circuit diagrams illustrating a pixel structure according to an embodiment of the present invention.
6 to 8 are circuit diagrams illustrating other embodiments of a pixel.
9 and 10 are diagrams illustrating a method of measuring a characteristic deviation of a second TFT (driving TFT).
11 and 12 are diagrams illustrating examples in which luminance deviation distributions of pixels vary according to grayscale.
13 and 14 are diagrams illustrating an OLED display device according to an embodiment of the present invention.

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

Referring to FIG. 1, the present invention measures the characteristic deviation of the driving TFT in each of the pixels (S1). The characteristic deviation of the driving TFT means the deviation of the threshold voltage (Vth) and conductance of the driving TFT in pixels. When the gate-source voltage Vgs of the driving TFT is greater than the threshold voltage Vth, a source-drain channel is formed and current flows. The conductance of the driving TFT is determined by the ratio (W/L) of the channel width (W) to the length (L) of the driving TFT and the mobility (μ). The mobility μ of the driving TFT may vary depending on the temperature.

In the present invention, deviations of two or more of the threshold voltage (Vth), conductance, gate-source voltage (Vgs), and temperature characteristics of the driving TFT are measured in each pixel, and a compensation value is set so that the deviations are minimized between the pixels. . The compensation value is stored in the memory of the OLED display (S2). When the characteristics of the driving TFTs are the same between the pixels, the current flowing through the OLED of the pixels becomes the same, so that the luminance of the pixels can be uniformly controlled.

According to the present invention, a compensation value is added or multiplied to the pixel data DATA of the input image to modulate the data, and the modulated data voltage Vdata is supplied to the pixels to write the data to the pixels (S3 and S4).

2 and 3 are diagrams illustrating a luminance measuring means of a pixel used when measuring a characteristic deviation of a driving TFT in the pixels using a camera or an optical scanner.

Referring to FIG. 2 , the OLED of the pixels is emitted by supplying a data voltage to the pixels, and the pixels are photographed with a camera. Algorithms for measuring the luminance of pixels from a camera image are known. The luminance of pixels can be measured from the image obtained from the camera. Since the camera takes pictures relatively far from the display panel 10 , the luminance of all pixels of the display panel 10 can be measured at once.

Referring to FIG. 3 , a data voltage is supplied to the pixels to emit OLEDs of the pixels, and the luminance of the pixels is measured with an optical scan module. The optical scan module may move along a preset scan direction at a distance from the display panel to simultaneously measure the luminance of pixels disposed in one line of the pixel array. The optical scan module can measure the luminance of pixels 1:1 and can measure the luminance without moire.

The resolution of the camera 20 is preferably greater than or equal to the resolution of the display panel 10 . The resolution of the optical scan module 30 is preferably the same as the resolution of one line of the display panel 10 . The output voltage of the camera 20 or the optical scan module 30 may be converted into digital data through an analog-digital converter (ADC) and transmitted to a deviation measuring system of the driving TFT.

4 and 5 are circuit diagrams illustrating a pixel structure according to an embodiment of the present invention.

4 and 5 , a pixel (Pixel, P) includes first to third TFTs ( T1 , T2 , and T3 ), a capacitor (CST), and an OLED. The TFTs may be implemented as an n-type MOSFET as shown in FIG. 4 or may be implemented as a p-type MOSFET as shown in FIG. 5 .

The OLED may be composed of organic compound layers in which a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), an electron injection layer (EIL), and the like are stacked.

The first TFT T1 is a first switch element that applies a data voltage Vdata' input through a data line to the gate of the second TFT T2 in response to the scan pulse S(n). The gate of the first TFT T1 is connected to the scan line. The drain (or source) of the first TFT ( T1 ) is connected to the data line, and the source (or drain) of the first TFT ( T1 ) is connected to the gate of the second TFT ( T2 ) through a node connected to the second TFT ( T2 ) ) is connected to the gate of The source and drain of the TFT are opposite to each other in the n-type MOSFET and the p-type MOSFET.

The second TFT (T2) is a driving element that controls the current flowing through the OLED according to the gate voltage. The second TFT T2 controls the current flowing through the OLED according to the gate voltage. The gate voltage of the second TFT T2 is the data voltage Vdata'. The drain (or source) of the second TFT T2 is connected to a power line to which the pixel power voltage EVDD is applied. The source (or drain) of the second TFT T2 is connected to the anode of the OLED via the drain-source of the third TFT.

The third TFT ( T3 ) is a second switch element for emitting light by connecting a current path between the second TFT ( T2 ) and the anode of the OLED in response to the emission control signal EM(n). The gate of the third TFT T3 is connected to the emission control line to which the emission control signal EM(n) is applied. The drain (or source) of the third TFT (T3) is connected to the source (or drain) of the second TFT (T2). The source (or drain) of the third TFT T3 is connected to the anode of the OLED. The cathode of the OLED is connected to a base voltage source (EVSS).

The capacitor CST is connected to the power line to which the pixel power voltage EVDD is applied and the gate of the second TFT T2 . This capacitor CST stores the voltage difference between the fixed pixel power supply voltage EVDD and the gate voltage of the second TFT T2, so that even if a current flows in the OLED, the gate-source voltage Vgs of the second TFT T2. ) is kept constant, so that it is possible to measure the characteristic deviation of the second TFT (T2) without Vgs fluctuation. On the other hand, since the anode voltage of the OLED changes when a current flows through the OLED, when the capacitor CST is connected between the gate of the second TFT and the anode of the OLED, the second TFT ( The gate voltage of T2) may be changed.

The luminance of an OLED (or the luminance of a pixel) is proportional to the current. If the luminance of the OLED is low, it is difficult to accurately measure the luminance with a camera, an optical scan module, or a luminance meter, and the measurement time is long, which increases the time required to measure the characteristic deviation of the second TFT (T2) at low current. The present invention increases the gate voltage of the second TFT (T2) so that the luminance of the OLED is increased to increase the current in the OLED to increase the luminance of the OLED and reduce the light emission time of the third TFT (T3) to reduce the luminance of the OLED to low luminance. By lowering it to , it is possible to quickly and accurately measure the characteristic deviation of the second TFT (T2), ie, the driving TFT, in the low grayscale.

The third TFT (T3) adjusts the lighting duty ratio of the OLED when measuring the characteristic deviation of the second TFT (T2). To this end, the present invention controls the pulse width of the emission control signal EM in each of the pixels by PWM (Pulse Width Modulation) as shown in FIG. measure

6 to 8 are circuit diagrams illustrating other embodiments of a pixel.

Referring to FIG. 6 , the pixels may include first and second capacitors CST1 and CST2 . The first capacitor CST1 is connected between the gate and the drain (or source) of the second TFT T2 as in the above-described embodiments of FIGS. 4 and 5 . The second capacitor CST2 is connected between the gate and the source (or drain) of the second TFT T2 . Other components of the pixel except for the capacitor structure are substantially the same as in FIGS. 4 and 5 .

Referring to FIG. 7 , the third TFT T3 may be connected between a power line to which the pixel power voltage EVDD is applied and a drain (or source) of the second TFT T2 . The gate of the third TFT T3 is connected to the emission control line. The drain (or source) of the third TFT is connected to the power supply line, and the source (or drain) of the third TFT (T3) is connected to the drain (or source) of the second TFT (T2). The capacitor CST is connected between the power line and the gate of the second TFT T2 . Other components of the pixel except for the second TFT T2 , the third TFT T3 and the capacitor CST are substantially the same as in FIGS. 4 and 5 .

Referring to FIG. 8 , the third TFT T3 may be connected between a power line to which the pixel power voltage EVDD is applied and a drain (or source) of the second TFT T2 . The gate of the third TFT T3 is connected to the emission control line. The drain (or source) of the third TFT is connected to the power supply line, and the source (or drain) of the third TFT (T3) is connected to the drain (or source) of the second TFT (T2). One electrode of the capacitor CST is connected to a node between the source (or drain) of the third TFT and the drain (or source) of the second TFT T2. The other electrode of the capacitor CST is connected to the gate of the second TFT T2. Other components of the pixel except for the second TFT T2 , the third TFT T3 and the capacitor CST are substantially the same as in FIGS. 4 and 5 .

9 and 10 are diagrams illustrating a method of measuring a characteristic deviation of the second TFT T2. 11 and 12 are diagrams illustrating examples in which luminance deviation distributions of pixels vary according to grayscale.

Referring to FIG. 9 , the third TFT T3 is turned on according to the emission control signal EM. The third TFT T3 allows a current to flow through the OLED for the duration of the pulse width of the emission control signal EM. Accordingly, the luminance of the OLED is proportional to the duty ratio of the emission control signal EM.

According to the present invention, the OLED is lit by appropriately applying the gate voltage of the second TFT (T2). The gate voltage of the second TFT T2 is the data voltage Vdata. The present invention adjusts the ON/OFF time of the third TFT (T3) to control the lighting time of each of the pixels, so that when the current in each of the pixels is low and high, the second TFT (T2) is Measure the conductance deviation. The conductance deviation means a deviation between the mobility μ and the channel ratio (W/L) of the driving TFT, that is, the second TFT T2 .

In the present invention, the duty ratio of the emission control signal EM is differently adjusted in each of the pixels to measure the conductance of the driving TFT when the current of the pixels is low and when the current is high. For example, if the conductance of the driving TFT and the OLED are ideal, the duty ratio of the emission control signal EM is ( As shown in B), the OLED luminance at 50% becomes 1/2. This is because when the duty ratio of the emission control signal EM is reduced to 1/2, the lighting time of the OLED is reduced to 1/2 to lower the luminance.

In the present invention, in order to measure the conductance of the second TFT T2 when the current in the pixels is low, the duty ratio of the emission control signal EM is set low, and the conductance of the second TFT T2 is increased in the high gray scale of the pixels. To measure, the duty ratio of the emission control signal is set high. In FIG. 9 , the duty ratio of the emission control signal EM is illustrated as 50% and 100%, but it should be noted that the present invention is not limited thereto. For example, the duty ratio of the low luminance may be set between 10% and 50%, and the duty ratio of the high luminance may be set between 80 and 100%.

The present invention measures the low luminance of the OLED by setting the gate voltage of the second TFT (T2) to an appropriate level to enable measurement of the luminance of the OLED and lowering the luminance of the pixel by controlling the duty ratio of the emission control signal (EM) to be small. can do. Accordingly, the present invention can quickly and accurately measure the conductance of the driving TFT at the low luminance of each of the pixels.

When measuring the conductance deviation of the TFT (T2), the gate voltage is a voltage equal to or higher than the threshold voltage (Vth) of the second TFT (T2) that causes the OLED to be turned on. Preferably, the second TFT (T2) has the best mobility Vth+ It is set to a voltage between 0.5V and Vth+2V. The on/off time of the third TFT T3 is controlled by the pulse width of the emission control signal EM.

Since the conductance of the second TFT T2 varies according to the Vgs of the second TFT T2, measuring the conductance of the second TFT T2 when Vgs changes may result in inaccurate measurement results. In the present invention, the lighting time of the third TFT (T3) is controlled by PWM while the gate voltage of the second TFT (T2) is fixed to prevent Vgs fluctuation, and the luminance of the OLED is measured by measuring the driving TFT between pixels. The conductance deviation can be calculated accurately. The luminance of an OLED can be measured with a camera, an optical scan module, or a luminance meter.

The present invention measures the low luminance of the OLED by setting the gate voltage of the second TFT (T2) to an appropriate level to enable measurement of the luminance of the OLED and lowering the luminance of the pixel by controlling the duty ratio of the emission control signal (EM) to be small. can do. Accordingly, the present invention can quickly and accurately measure the conductance of the low-brightness driving TFT in each of the pixels.

In the present invention, the high grayscale luminance of the OLED can be measured by increasing the luminance of the pixel by greatly controlling the duty ratio of the emission control signal EM while the gate voltage of the second TFT T2 is fixed. Accordingly, the present invention can quickly and accurately measure the conductance of the driving TFT at the high gradation luminance of each of the pixels.

The present invention can measure the conductance of the second TFT T2 while changing the Vgs of the second TFT T2 in order to analyze the conductance deviation according to the Vgs of the second TFT T2. The Vgs of the second TFT T2 may be changed by adjusting the gate voltage of the second TFT T2 , that is, the data voltage.

The mobility μ of the driving TFT may vary depending on the temperature. In the present invention, in order to measure the temperature characteristic deviation of the second TFT T2 in each of the pixels, the mobility of the TFT according to the temperature change can be measured by repeating the above conductance measurement method while changing the temperature of the pixels.

The present invention derives a first compensation value that minimizes the conductance deviation of the driving TFT in each of the pixels by measuring the luminance of the OLED while changing data to be written in each of the pixels. The data are stored in a memory to form a database of the conductance deviation and the first compensation value of the second TFT T2 measured in each of the pixels. As described above, the conductance deviation of the driving TFT includes a conductance deviation according to Vgs and a conductance deviation according to temperature.

The characteristic deviation of the driving TFT (TFT) varies depending on the gate voltage of the second TFT (T2), that is, the data voltage (Vdata). In the present invention, in order to accurately measure the deviation of the threshold voltage (Vth) of the driving TFT in each of the pixels, a voltage within an optimal measurement region is applied to the gate of the driving TFT as shown in FIG. 10 and OLED luminance is measured at that time. Considering the accuracy and time of measurement, the measurement can be performed while applying the voltage within the optimal measurement region to the gate of the driving TFT one or more times.

The voltage of the optimal measurement region should be a voltage equal to or higher than the Vth of the driving TFT so that the luminance measurement of the OLED is easy, and it is preferable that the driving TFT be set to a high voltage. The luminance range of OLED in the measurement optimal region is 0.4 [nit] ~ 30 [nit]. The voltage in the measurement optimal region satisfying these conditions may be set to a voltage between the threshold voltage (Vth) and (1 grayscale voltage + 1.5V) in the TFT of the n-type MOSFET structure, but is not limited thereto. The voltage of the optimal measurement region may be set to a voltage between the threshold voltage (Vth) and (1 grayscale voltage - 1.5V) in the TFT of the p-type MOSFET structure, but is not limited thereto.

In the low grayscale, the luminance of the OLED is widely dispersed according to the characteristic deviation of the driving TFT as shown in FIG. 11 . Accordingly, the threshold voltage deviation of the driving TFT between pixels can be accurately measured at low grayscale. On the other hand, since the luminance of the OLED in the high gray scale is almost constant between pixels as shown in FIG. 12 , it is difficult to know the difference in the characteristics of the driving TFT between the pixels. The voltage in the optimal measurement region should be set between a voltage at which the luminance of the OLED emits light at a level of 0.4 [nit] to 30 [nit], that is, equal to or higher than the Vth of the driving TFT, and a predetermined low grayscale voltage.

In FIG. 10, “frequency” is the number of accumulated pixels according to Vgs. 11 and 12, “frequency” is the cumulative number of pixels according to the luminance of the OLED.

The present invention derives a second compensation value that minimizes the threshold voltage deviation of the driving TFT between the pixels by measuring the circuitry of the OLED while changing the data to be written in each of the pixels. The second compensation value may be set for each temperature by measuring the threshold voltage deviation of the driving TFT for each temperature. The data is stored in a memory to form a database of the threshold voltage deviation and the second compensation value of the second TFT T2 measured in each of the pixels.

The present invention can compensate for the characteristic deviation of the driving TFT between pixels in the following way. When there is a difference in the characteristics of the driving TFT between pixels, the threshold voltage Vth and conductance parameters of the driving TFT are adjusted in each of the pixels to equalize the current flowing through the OLED of the pixels. In Equation 1 below, K is a conductance parameter including mobility (μ) and channel ratio (W/L). Vth is the threshold voltage parameter. The first compensation value is set to a value that adjusts K so that the conductance deviation of the driving TFT in each of the pixels is minimized. The second compensation value is set to a value at which the deviation of the threshold voltage Vth of the driving TFT in each of the pixels is minimized. In order to compensate for a characteristic deviation of the driving TFT between pixels, pixel data of an input image is modulated with first and second compensation values. The first compensation value may be multiplied by the pixel data, and the second compensation value may be added to the pixel data. Since the calculation method may vary depending on the compensation algorithm, the present invention is not limited thereto.

13 and 14 are diagrams illustrating an OLED display device according to an embodiment of the present invention.

13 and 14 , an OLED display device according to an embodiment of the present invention includes a display panel 10 and a display panel driving circuit.

The data of the input image is displayed on the pixel array of the display panel 10 . The pixel array of the display panel 10 includes a plurality of data lines 14 , a plurality of scan lines 15 intersecting the data lines 14 , and pixels arranged in a matrix form. Each of the pixels P is implemented as a pixel circuit as shown in FIGS. 4 to 8 .

The display panel driving circuit includes a data driving circuit 12 , a scan driving circuit 13 , and a timing controller 11 . The display panel driving circuit writes the input image data modulated with the first and second compensation values to the pixel array of the display panel 10 in order to compensate for the driving TFT characteristic deviation between pixels.

The data driving circuit 12 uses a digital-to-analog converter (hereinafter referred to as "DAC") to compensate for analog gamma compensation of the pixel data DATA' of the input image modulated by the timing controller 11 . The data voltage Vdata' is generated by converting the voltage into a voltage, and the data voltage Vdata' is output to the data lines 14 .

The scan driving circuit 13 outputs the scan pulse S(n) and the emission control pulse EM(n) to the scan lines 15 under the control of the timing controller 11 . The scan driving circuit 13 shifts the scan pulse S(n) and the light emission control pulse EM(n) using a shift register under the control of the timing controller 11 .

The timing controller 11 receives pixel data DATA of an input image and input timing signals from a host system (not shown). The input timing signals include a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a data enable signal DE, and a dot clock DCLK. The timing controller 11 is configured to control the operation timing of the data driving circuit 12 and the scan driving circuit 13 based on the timing signals Vsync, Hsync, DE, and DCLK received together with the pixel data of the input image. A timing control signal (DDC, GDC) is generated.

The timing controller 11 includes a modulation circuit for modulating data. The modulation circuit may include a memory storing first and second compensation values, and a logic unit that modulates pixel data of an input image using the first and second compensation values. The memory and the logic unit may be embedded in the timing controller 11 or installed outside the timing controller 11 . The data DATA' modulated by the logic unit is transmitted to the data driving circuit 12 .

The host system may be implemented as any one of a television (Television) system, a set-top box, a navigation system, a DVD player, a Blu-ray player, a personal computer (PC), a home theater system, and a phone system.

14 is an example in which the OLED display device of the present invention is applied to a mobile device such as a smart phone. In the example of FIG. 14 , the data driving circuit 12 is integrated in the drive IC 100 . The memory 102 stores first and second compensation values. The logic unit 101 modulates pixel data input from the application processor (AP) 200 using the first and second compensation values and outputs the modulated pixel data to the drive IC 100 .

Those skilled in the art from the above description will be able to see that various changes and modifications can be made without departing from the technical spirit of the present invention. Accordingly, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

10: display panel 11: timing controller
12: data driving circuit 13: scan driving circuit
101: logic unit 102: memory

Claims (8)

A driving TFT for controlling a current flowing through the organic light emitting diode, a first switch TFT for supplying a data voltage input through a data line in response to a scan pulse to the gate of the driving TFT, and the driving TFT and the above in response to a light emission control signal a display panel having pixels including a third switch TFT connecting a current path between the anodes of the organic light emitting diode and at least one capacitor connected to a gate of the driving TFT;
a modulator for modulating the pixel data by adding or multiplying preset first and second compensation values to pixel data of an input image; and
and a display panel driving circuit for writing data modulated by the modulator to the pixels;
The first compensation value is set to a value for compensating for a conductance deviation of the driving TFT measured by changing the duty ratio of the emission control signal while maintaining the gate voltage of the driving TFT constant;
The conductance of the driving TFT is determined according to the mobility and the channel ratio of the driving TFT,
and the second compensation value is set to a value for compensating for a threshold voltage deviation of the driving TFT. A driving TFT for controlling a current flowing through the organic light emitting diode, a first switch TFT for supplying a data voltage input through a data line in response to a scan pulse to the gate of the driving TFT, and the driving TFT and the above in response to a light emission control signal A method of driving an organic light emitting diode display having pixels including a third switch TFT connecting a current path between the anodes of the organic light emitting diode, and at least one capacitor connected to a gate of the driving TFT, the method comprising:
setting a first compensation value for compensating for the measured conductance deviation of the driving TFT by changing the duty ratio of the emission control signal while maintaining the gate voltage of the driving TFT constant;
setting a second compensation value for compensating for the measured threshold voltage deviation of the driving TFT by applying a voltage within an optimal measurement region set to a voltage range equal to or greater than the threshold voltage of the driving TFT to the gate of the driving TFT;
modulating the pixel data by adding or multiplying the first and second compensation values to pixel data of an input image; and
writing pixel data modulated by a modulator to the pixels;
A method of driving an organic light emitting diode display device wherein the conductance of the driving TFT is determined according to mobility and a channel ratio of the driving TFT. 3. The method of claim 2,
A method of driving an organic light emitting diode display, wherein at least one of the first and second compensation values is set for each temperature. 3. The method of claim 2,
At least one of the first and second compensation values is set for each gate-source voltage of the driving TFT. 3. The method of claim 2,
A method of driving an organic light emitting diode display, wherein the deviation of the conductance of the driving TFT and the deviation of the threshold voltage of the driving TFT are measured based on the change in luminance of the organic light emitting diode. 3. The method of claim 2,
A method of driving an organic light emitting diode display, wherein the luminance of the organic light emitting diode is measured by a camera or an optical scan module. 3. The method of claim 2,
The voltage range of the optimal measurement region is a voltage at which the luminance of the organic light emitting diode emits light at a level of 0.4 [nit] to 30 [nit]. 3. The method of claim 2,
The voltage range of the optimal measurement region is greater than or equal to a threshold voltage of the driving TFT and is set to a voltage between a predetermined low grayscale voltage.

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