KR101572270B1 - Organic Light Emitting Diode Display And Driving Method Thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting diode display device and a driving method thereof that can change brightness while maintaining white balance.

The organic light emitting diode display device driven by the RGB common method includes a display panel having a plurality of pixels each including an organic light emitting diode arranged in a matrix form at intersecting regions of data lines and gate lines; A data driving circuit for converting target compensation data for maintaining white balance by referring to gamma reference voltages into data voltages and supplying the data to the data lines; A gamma reference voltage generating circuit for dividing the high-potential gamma power source to generate the gamma reference voltages; Calculates APL values for each frame of the input image by analyzing the input data, generates gamma power adjustment data based on the APL value and an input temperature sensing value, and refers to the gamma power adjustment data, To the target compensation data; And a gamma power adjustment circuit for varying an output level of the high-potential gamma power supply in response to the gamma power adjustment data.

Description

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

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting diode (OLED) display device, and more particularly, to an organic light emitting diode display device capable of changing brightness while maintaining white balance and a driving method thereof.

2. Description of the Related Art In recent years, various flat panel displays (FPDs) have been developed to reduce weight and volume, which are disadvantages of cathode ray tubes. Such a flat panel display device includes a liquid crystal display (LCD), a field emission display (FED), a plasma display panel (PDP), and an electroluminescence Device).

PDP has attracted attention as a display device that is most advantageous for large screen size but small size because of its simple structure and manufacturing process, but it has disadvantage of low luminous efficiency, low luminance and high power consumption. A TFT LCD having a thin film transistor (hereinafter, referred to as "TFT") as a switching element is the most widely used flat panel display device, but it is a non-luminous device and thus has a narrow viewing angle and low response speed. On the other hand, the electroluminescent device is divided into an inorganic light emitting diode display device and an organic light emitting diode display device according to the material of the light emitting layer. In particular, the organic light emitting diode display device uses self light emitting devices that emit self- Brightness and viewing angle are large.

The organic light emitting diode display device has an organic light emitting diode (OLED) as shown in FIG. The OLED has an anode electrode, a cathode electrode, and organic compound layers (HIL, HTL, EML, ETL, EIL) formed between both electrodes.

The organic compound layer includes a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and an electron injection layer EIL).

When a driving voltage is applied to the anode electrode and the cathode electrode, holes passing through the HTL and electrons passing through the ETL are transferred to the EML to form excitons, Thereby generating visible light.

The organic light emitting diode display device arranges a plurality of R, G and B pixels each including the OLED as described above in a matrix form, selects pixels by selectively turning on the TFT as an active element through a scan pulse, And controls the brightness of the pixels according to the gradation of the digital video data.

Such organic light emitting diode display devices typically convert digital video data into data voltages based on gamma reference voltages generated through the RGB independent gamma method. As shown in FIG. 2, the RGB independent gamma method has gamma resistance strings independent of R, G, and B, and divides each gamma resistor string to generate R, G, and B gamma reference voltages V0 to V9 . In the RGB independent gamma method, since the output level of the high-potential gamma power (RVCC, GVCC, BVCC) can be adjusted for each of R, G and B, the average picture level (APL) It is easy to maintain the white balance when the output level of the high-potential gamma power source is changed such as driving. Here, the APL drive is widely used for improving the contrast ratio and improving the power consumption according to the display image by increasing the brightness of white in the dark image while decreasing the brightness in the white image in the bright image. For example, APL driving improves power consumption by lowering the brightness of white in the image of the snow in the ski area, and enhances the brightness of white in the image that shows the night sky stars. However, the RGB independent gamma method requires independent gamma resistor strings for R, G, and B, and also requires three gamma (gamma) resistors to change the output levels of the R, G, and B high gamma gamma powers (RVCC, GVCC, BVCC) A power adjusting circuit is required, which leads to a disadvantage that the circuit size becomes large.

In order to reduce the circuit size, an RGB common gamma method can be considered. As shown in FIG. 3, the RGB common gamma method divides one gamma resistor string to generate gamma reference voltages (V0 to V9) in common regardless of R, G, and B. However, in the RGB common gamma method, since the output level of the high-potential gamma power (RVCC = GVCC = BVCC) can not be adjusted by R, G, and B, the output level of the high- If it changes, it is impossible to maintain the white balance. For example, when the output level of the high-potential gamma power source (RVCC = GVCC = BVCC) is changed from 10 V to 12 V for driving the APL, the data voltages for R, G and B for expressing the maximum gradation are increased to the same magnitude. However, since the OLED luminous efficiency is different for R, G and B, if the data voltages for R, G and B are increased to the same magnitude, the white balance is broken.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an organic light emitting diode display device and a method of driving the same, in which luminance can be changed while maintaining white balance under the RGB common gamma system.

According to an embodiment of the present invention, an organic light emitting diode (OLED) display device driven by an RGB common gamma method is arranged in a matrix for each intersection of data lines and gate lines, and includes an organic light emitting diode A display panel having a plurality of pixels; A data driving circuit for converting target compensation data for maintaining white balance by referring to gamma reference voltages into data voltages and supplying the data to the data lines; A gamma reference voltage generating circuit for dividing the high-potential gamma power source to generate the gamma reference voltages; Calculates APL values for each frame of the input image by analyzing the input data, generates gamma power adjustment data based on the APL value and an input temperature sensing value, and refers to the gamma power adjustment data, To the target compensation data; And a gamma power adjustment circuit for varying an output level of the high-potential gamma power supply in response to the gamma power adjustment data.

The organic light emitting diode display device further includes a temperature sensor formed on the display panel to generate the temperature sensing value.

The organic light emitting diode display further includes an EEPROM including a first gamma lookup table storing reference compensation data and a second gamma lookup table storing difference data; The reference compensation data corresponding to the reference output level of the high-potential gamma power source is predetermined for each gradation in consideration of white balance; The difference value data is used for obtaining the target compensation data by being added to or subtracted from the reference compensation data, and is previously set to a different value according to the gamma power adjustment data.

Wherein the timing controller compares the value of the gamma power adjustment data with a predetermined set value; Generating the target compensation data by adding or subtracting the difference data to or from the reference compensation data if the value of the gamma power adjustment data is greater than or equal to the set value; As a result of the comparison, when the value of the gamma power adjustment data is smaller than the set value, the reference compensation data is generated as the target compensation data.

The set value indicates a threshold value of the gamma power adjustment data capable of maintaining the white balance when the output level of the high-potential gamma power source changes.

The second gamma look-up table is stored in the capacity allocated to the first gamma look-up table in the EEPROM.

An organic light emitting diode (OLED) display device including a display panel having a plurality of pixels each including an organic light emitting diode and arranged in a matrix form at intersecting regions of data lines and gate lines according to an embodiment of the present invention, The APL value for each frame of the input image is analyzed by analyzing the input data, the gamma power adjustment data is generated based on the APL value and the input temperature sensing value, and the gamma power adjustment data (A) modulating the input data into target compensation data for maintaining a white balance with reference to the input data; (B) varying an output level of the high-potential gamma power supply in response to the gamma power adjustment data; Dividing the high-potential gamma power supply to generate gamma reference voltages (C); And (D) converting the target compensation data into a data voltage with reference to the gamma reference voltages and supplying the data to the data lines.

Even when the output level of the high-potential gamma power is changed according to the image state and the panel temperature under the RGB common gamma system, the OLED display and the driving method thereof according to the present invention can use the two gamma LUTs, The white balance can be maintained. Since the reference compensation data is stored in the first LUT among the two gamma LUTs and the difference data between the target compensation data and the reference compensation data is stored in the second LUT, Can be effectively allocated to the EEPROM.

Furthermore, since the organic light emitting diode display device and the driving method thereof according to the present invention can achieve similar effects to the RGB independent gamma method according to the RGB common gamma method, it is possible to solve the problem that the circuit size increases due to the RGB independent gamma method have.

Hereinafter, preferred embodiments of the present invention will be described with reference to FIGS. 4 to 6. FIG.

4 illustrates an organic light emitting diode display device according to an embodiment of the present invention.

Referring to FIG. 4, an organic light emitting diode display device according to an embodiment of the present invention includes a display panel 10, a timing controller 11, a gamma power adjusting circuit 12, a gamma reference voltage generating circuit 13, A gate drive circuit 15, a temperature sensor 16, and an EEPROM 17, as shown in FIG.

A plurality of data lines DL and a plurality of gate lines GL are intersected with each other in the display panel 10 and R, G and B pixels are arranged in a matrix form in the intersection areas. R pixels each include an R OLED to display an image corresponding to R data. The G pixels each include G OLED to display an image corresponding to G data. The B pixels display an image corresponding to the B data including B OLED. Each of the pixels is connected to the data line DL through the TFT, receives the data voltage corresponding to the data, and is connected to the gate line GL through the TFT to receive the scan pulse. Further, each of the pixels is connected to a driving voltage supply line, and is supplied with a high potential driving voltage Vdd and a low potential driving voltage Vss. A temperature sensor 16 is formed on one side of the display panel 10. The temperature sensor 16 senses the temperature of the display panel 10 and analog-to-digital converts the analog temperature value to generate a temperature sensing value Tsen.

The timing controller 11 analyzes 8-bit digital video data (hereinafter referred to as "input data") (R / G / B / 8 bits) input from the outside and outputs an APL ), And receives a temperature sensing value (Tsen) from the temperature sensor 16. [ Then, gamma power adjustment data (CDATA) is generated based on the APL value and the temperature sensing value (Tsen) to adjust the luminance of the display image according to the image state and the panel temperature. The timing controller 11 refers to the gamma power adjustment data CDATA so as to change the input data (R / G / B / 8 bits) so that the brightness of the display image is changed while the white balance is maintained, (Rc / Gc / Bc /: 10 bits) of digital video data (hereinafter referred to as "target compensation data"). The timing controller 11 generates a data control signal DDC and a gate control signal DDC based on first timing information Hsync, Vsync, DCLK, DE input from the outside and second timing information loaded from the EEPROM 17, (GDC).

The gamma power adjustment circuit 12 adjusts the brightness of the display image by adjusting the output level of the high-potential gamma power supply (MVCC) in response to the gamma power adjustment data (CDATA) from the timing controller 11. [ The gamma power regulating circuit 12 may be implemented with a programmable gamma IC (Programmable Gamma Integrated Circuit). Since the present invention is based on the RGB common gamma method, only one gamma power adjustment circuit 12 is required.

The gamma reference voltage generating circuit 13 includes a gamma resistor string including a plurality of resistors connected between a high-potential gamma power supply (MVCC) and a base power supply (GND) as shown in FIG. 3, To generate a plurality of gamma reference voltages (V0 to V9) that are divided between the reference voltages. Here, since the high-potential voltage that determines the magnitude of the gamma reference voltages V0 to V9 depends on the output level of the high-potential gamma power supply MVCC, the magnitude of the gamma reference voltages V0 to V9 is proportional to the magnitude of the high- (MVCC). The gamma reference voltages (V0 to V9) are generated in common regardless of R, G, and B.

The data driving circuit 14 converts the 10-bit target compensation data Rc / Gc / Bc / 10 bits into R, G, and B bits by referring to the gamma reference voltages V0 to V9 under the control of the data control signal DDC. And supplies the R, G, and B gamma compensation voltages to the data lines DL of the display panel 10 as R, G, and B data voltages. The luminance adjustment value by the gamma reference voltages (V0 to V9) is reflected in the R, G, and B data voltages, and the white balance compensation value by the target compensation data (Rc / Gc / Bc /: 10 bits) is reflected.

The gate drive circuit 15 generates a scan pulse swung between the gate turn-on voltage for turning on the TFT in the pixels and the gate turn-off voltage for turning off the TFT under the control of the gate control signal GDC . The scan lines are supplied to the gate lines GL to sequentially drive the gate lines GL to select the horizontal line of the display panel 10 to which the R, G, and B data voltages are to be supplied.

The EEPROM 17 stores second timing information necessary for driving the display panel 10, reference compensation data, and difference value data. The second timing information includes a gate output enable signal for controlling the output timing of the scan pulse, a source output enable signal for controlling the output timing of the data voltage, and the like.

5 shows the details of the configuration of the timing controller 11 and the EEPROM 17.

Referring to FIG. 5, the timing controller 11 includes a main controller 111, an EEPROM controller 112, a drive information register 113, and a control signal generator 114. The EEPROM 17 includes a look-up table (LUT) # 1 (171) and a gamma LUT # 2 (172). The EEPROM 17 stores data in 8-bit units.

The gamma LUT # 1 171 stores 10-bit reference compensation data (DATA_REF: 10 bits). The reference compensation data (DATA_REF: 10 bits) is determined in advance for each of the gradations R, G and B in consideration of the white balance in correspondence with the predetermined reference output level of the high-potential gamma power supply (MVCC).

The gamma LUT # 2 (172) stores difference value data (DATA_DIFF). The difference value data DATA_DIFF is used to obtain the target compensation data Rc / Gc / Bc / 10 bits, which is added to or subtracted from the reference compensation data DATA_REF (10 bits) All.

The gamma LUT # 1 171 stores the reference compensation data (DATA_REF: 10 bits) in units of 10 bits, while the EEPROM 17 is capable of storing data in units of 8 bits, : 10 bits) is allocated to the gamma LUT # 1 (171). However, since the capacity occupied by the reference compensation data (DATA_REF: 10 bits) is actually 10 bits, six bits out of the 16 bits remain. The present invention stores gamma LUT # 2 172 for difference data (DATA_DIFF) in the capacity allocated to gamma LUT # 1 (171) by storing difference value data (DATA_DIFF) Can be stored. As a result, according to the present invention, it is not necessary to increase the capacity of the EEPROM 17 in order to store the gamma LUT # 2 172. For example, if the target compensation data (Rc / Gc / Bc / 10 bit) is changed to 1020 to match the white balance under the assumption that the reference compensation data (DATA_REF: 10 bit) , The target value '1020' need not be stored, and the difference value '20' between the target value and the reference value is stored in the gamma LUT # 2 172. If '1020' (target value) other than '20' (difference value) is stored, 16 bits are required for the gamma LUT # 2 172 in the EEPROM 17 additionally.

The EEPROM control unit 112 receives information stored in the gamma LUT # 1 171 and information stored in the gamma LUT # 2 172 together with second timing information from the EEPROM 17 when driving power is applied to the display apparatus And stores it in the read-in drive information register 113.

The control signal generator 114 generates a control signal based on the second timing information stored in the driving information register 113 and the first timing information Hsync, Vsync, DCLK, A data control signal DDC for controlling the operation timing of the gate drive circuit 15 and a gate control signal GDC for controlling the operation timing of the gate drive circuit 15. [

The main controller 111 analyzes the 8-bit input data (R / G / B / 8 bits) and calculates an APL value for each frame of the input image. The main controller 111 receives the temperature sensing value Tsen from the temperature sensor 16, . Then, gamma power adjustment data (CDATA) is generated based on the APL value and the temperature sensing value (Tsen) to adjust the luminance of the display image according to the image state and the temperature. Here, the gamma power adjustment data CDATA has a smaller value as the APL value is larger, that is, as the display image of one frame is brighter, and as the APL value is smaller, that is, as the display image of one frame is darker, The value becomes larger. The gamma power adjustment data CDATA has a smaller value as the temperature sensing value Tsen is higher, that is, as the temperature of the display panel 10 is higher, and as the temperature sensing value Tsen is lower, 10) is lower, the value becomes larger. Therefore, the value of the gamma power adjustment data CDATA is finally determined to the APL value and the temperature sensing value Tsen.

The main controller 111 compares the finally determined gamma power adjustment data CDATA with a predetermined set value. Here, the set value indicates a threshold value of the gamma power adjustment data CDATA that can maintain the white balance when the output level of the high-potential gamma power supply MVCC changes. If the value of the gamma power adjustment data CDATA is smaller than the set value, the main controller 111 sets the reference compensation data (DATA_REF: 10 bits) of the gamma LUT # 1 171 stored in the drive information register 113, (Rc / Gc / Bc / 10 bits) for maintaining the white balance. On the other hand, when the value of the gamma power adjustment data CDATA is equal to or greater than the set value, the main controller 111 outputs the difference data DATA_DIFF of the gamma LUT # 2 172 stored in the drive information register 113 to the drive information register (Rc / Gc / Bc /: 10 bits) for maintaining the white balance by adding and subtracting the reference compensation data (DATA_REF: 10 bits) of the gamma LUT # 1 (171)

6 illustrates a method of driving an organic light emitting diode display according to an embodiment of the present invention.

Referring to FIG. 6, the driving method analyzes the input data, calculates an APL value for each frame of the input image (S10), and obtains a temperature sensing value from the temperature sensor (S20). The driving method generates gamma power adjustment data based on the APL value and the temperature sensing value (S30). This driving method adjusts the luminance of the display image according to the image state and the panel temperature by adjusting the output level of the high-potential gamma power supply based on the gamma power adjustment data (S40).

This driving method compares the value of the gamma power adjustment data with a predetermined set value (S50). Here, the set value indicates a threshold value of the gamma power adjustment data capable of maintaining the white balance when the output level of the high-potential gamma power source changes.

If the value of the gamma power adjustment data is greater than or equal to the set value, the driving method selects the gamma LUT # 1 and the gamma LUT # 2 (S60), and stores the difference data of the gamma LUT # And adds or subtracts the compensation data to generate target compensation data for maintaining white balance (S70).

As a result of the comparison, if the value of the gamma power adjustment data is smaller than the set value, the driving method selects the gamma LUT # 1 (S80), and sets the reference compensation data of the gamma LUT # 1 as the target compensation data for maintaining the white balance (S90).

As described above, according to the present invention, even if the output level of the high-potential gamma power is changed according to the image state and the panel temperature under the RGB common gamma system, the organic light- The white balance can be maintained by modulating the data with the target compensation data. Since the reference compensation data is stored in the first LUT among the two gamma LUTs and the difference data between the target compensation data and the reference compensation data is stored in the second LUT, Can be effectively allocated to the EEPROM.

Furthermore, since the organic light emitting diode display device and the driving method thereof according to the present invention can achieve similar effects to the RGB independent gamma method according to the RGB common gamma method, it is possible to solve the problem that the circuit size increases due to the RGB independent gamma method have.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining the principle of light emission of a general organic light emitting diode display device. FIG.

2 is a diagram showing R, G, and B gamma resistor strings according to the RGB independent gamma scheme;

FIG. 3 is a diagram showing one gamma resistor string according to the RGB common gamma method; FIG.

4 is a block diagram showing an organic light emitting diode display device according to an embodiment of the present invention.

5 is a detailed circuit diagram of the timing controller and the EEPROM of FIG. 4;

6 is a flowchart illustrating a method of driving an organic light emitting diode display according to an exemplary embodiment of the present invention.

Description of the Related Art

10: Display panel 11: Timing controller

12: gamma power adjustment circuit 13: gamma reference voltage generation circuit

14: Data driving circuit 15: Gate driving circuit

16: Temperature sensor 17: EEPROM

111: main controller 112: EEPROM control unit

113: drive information register 114: control signal generator

171: Gamma LUT # 1 172: Gamma LUT # 2

Claims (10)

An organic light emitting diode display device driven by an RGB common gamma system, A display panel having a plurality of pixels each including an organic light emitting diode, the display panel being disposed in a matrix form at intersecting regions of the data lines and the gate lines; A data driving circuit for converting target compensation data for maintaining white balance by referring to gamma reference voltages into data voltages and supplying the data to the data lines; A gamma reference voltage generating circuit for dividing the high-potential gamma power source to generate the gamma reference voltages; Calculates APL values for each frame of the input image by analyzing the input data, generates gamma power adjustment data based on the APL value and an input temperature sensing value, and refers to the gamma power adjustment data, To the target compensation data; And And a gamma power adjustment circuit for varying an output level of the high-potential gamma power supply in response to the gamma power adjustment data, The target compensation data is obtained by adding a predetermined difference value to a different value according to the gamma power adjustment data to predetermined reference compensation data for each gradation in consideration of the white balance corresponding to the level of the gamma reference voltages, To the organic light emitting diode display device. The method according to claim 1, And a temperature sensor formed on the display panel to generate the temperature sensing value. The method according to claim 1, Further comprising an EEPROM including a first gamma lookup table in which the reference compensation data is stored and a second gamma lookup table in which the difference data is stored. The method of claim 3, The timing controller includes: Compare the value of the gamma power adjustment data with a predetermined set value; Generating the target compensation data by adding or subtracting the difference data to or from the reference compensation data if the value of the gamma power adjustment data is greater than or equal to the set value; And generates the reference compensation data as the target compensation data if a value of the gamma power adjustment data is smaller than the set value as a result of the comparison. 5. The method of claim 4, Wherein the set value indicates a threshold value of the gamma power adjustment data capable of maintaining the white balance at the output level change of the high-potential gamma power source. The method of claim 3, Wherein the second gamma lookup table is stored in the capacity allocated to the first gamma lookup table in the EEPROM. delete A method of driving an organic light emitting diode (OLED) display device having a display panel having a plurality of pixels each including an organic light emitting diode and arranged in a matrix for each of intersections of data lines and gate lines and driven by an RGB common gamma method, Calculates APL values for each frame of the input image by analyzing the input data, generates gamma power adjustment data based on the APL value and an input temperature sensing value, and refers to the gamma power adjustment data, (A) modulating the image data into target compensation data for maintaining white balance; (B) varying an output level of the high-potential gamma power supply in response to the gamma power adjustment data; Dividing the high-potential gamma power supply to generate gamma reference voltages (C); And (D) converting the target compensation data into a data voltage and supplying the data to the data lines with reference to the gamma reference voltages, For the step (A), the reference compensation data stored in the first gamma lookup table and the difference data stored in the second gamma lookup table are used; The reference compensation data corresponding to the reference output level of the high-potential gamma power source is predetermined for each gradation in consideration of white balance; Wherein the difference value data is used to obtain the target compensation data by being added to or subtracted from the reference compensation data, and is determined to be a different value according to the gamma power adjustment data. 9. The method of claim 8, The step (A) Comparing the value of the gamma power adjustment data with a predetermined set value; Generating the target compensation data by adding or subtracting the difference data to or from the reference compensation data if the value of the gamma power adjustment data is greater than or equal to the set value; And And generating the reference compensation data as the target compensation data if the value of the gamma power adjustment data is less than the set value as a result of the comparison. 10. The method of claim 9, Wherein the set value indicates a threshold value of the gamma power adjustment data capable of maintaining the white balance at the output level change of the high-potential gamma power supply.

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