KR100675645B1 - Driving system of oled and method for driving oled - Google Patents

Abstract

The present invention relates to a driving system and a driving method of an organic light emitting display device. The driving system of the organic light emitting display device according to the present invention includes an organic light emitting device including a plurality of pixels including a red pixel, a green pixel, and a blue pixel. An OLED panel; A control unit for receiving first digital data and converting the first digital data into second digital data for gradation display; And a level shift unit converting the second digital signal into a data voltage, supplying the data voltage to the pixels, and supplying different source voltages to the red, green, and blue pixels, respectively. do.

Description

Driving system and driving method of an electroluminescent device {DRIVING SYSTEM OF OLED AND METHOD FOR DRIVING OLED}

1 is a look-up table (LUT) for use as R, G, B color data signals in an organic light emitting device according to the prior art.

2 is a block diagram of an organic light emitting display device according to the present invention;

3 is a view illustrating a unit pixel including an organic light emitting display device and a driving circuit in the organic light emitting display device according to the present invention;

4 is a timing diagram of digital driving of the organic light emitting display device of FIG. 2 in the organic light emitting display device according to the present invention;

5 is a view illustrating a control unit for use in the organic light emitting display device of FIG. 2 in the organic light emitting display device according to the present invention; FIG.

6 is an example of a look-up table (LUT) included in the controller of FIG. 5 in the organic light emitting device according to the present invention.

*** Explanation of symbols for main parts of drawing ***

100: EL display device 101: pixel

103: OLED (organic light emitting diode device) 110: A / D converter

120: frame memory section 125: latch

130: level shift unit 140: control unit

150: scan driver 160: organic light emitting device panel

The present invention relates to an electroluminescent device, and more specifically, gamma from the outside even when using the same Look Up Table (LUT) by separating and adjusting the digital R, G, and B data levels input to the organic field panel. The present invention relates to a driving system and a driving method of an organic light emitting display device which can be controlled.

Typical flat panel display apparatuses include liquid crystal displays, field emission displays, plasma display panels, and EL display panels.

Among them, the EL display panel is a self-luminous element that emits a phosphor by recombination of electrons and holes, and is classified roughly into an inorganic EL using an inorganic compound and an organic EL using an organic compound.

Unlike other display devices, such an EL display panel can be driven at a low driving voltage (10V), and it is excellent in recognition because it uses self-luminous, and unlike an LCD, a backlight can be made ultra thin because it does not require a backlight.

In addition, the EL display panel has advantages such as a wide viewing angle and a fast response speed compared to a liquid crystal display device (LCD), and thus is expected as a next generation display device.

The organic EL display element is usually composed of an electron injection layer, an all embroidery layer, a light emitting layer, a hole transport layer, and a hole injection layer laminated between a cathode and an anode. In the organic EL device, when a predetermined voltage is applied between the anode and the cathode, electrons generated from the cathode move to the light emitting layer through the electron injection layer and the electron transport layer, and holes generated from the anode are transferred through the hole injection layer and the hole transport layer. Move toward the light emitting layer.

Accordingly, the light emitting layer emits light by recombination of electrons and holes supplied from the electron transport layer and the hole transport layer.

The field display device includes an organic light emitting diode (OLED) panel in which a plurality of pixels are arranged in a matrix. The pixels include field cells, such as organic light emitting diodes. The organic light emitting diode panel is connected to a scan driver and a data driver controlled by a controller.

The scan driver is operated to activate a pixel, and the data driver supplies a driving voltage to the activated pixel. The pixel emits light according to the driving voltage. Each pixel displays any one of red (R), green (G), and blue (B).

The electric field display device displays an image in gradation. Each pixel in the field display device is controlled to emit or not emit light for each frame. In detail, each frame is divided into a plurality of subframes, and the pixel is emitted or non-emitted during the subframe corresponding to each bit of the digital data signal.

For example, during a 12 bit digital data signal, one frame is divided into 12 subframes. It is possible to display the gradation of a desired image by adding up the emission time in each subframe during the one subframe.

In the case of gradation display, the digital data is converted into other digital data based on the lookup table (LUT). The lookup table (LUT) is stored in a control unit for driving a scan driver and a data driver of an electric field display device. The digital data signal is input to the controller. The control unit includes a multiplexer for receiving a digital data signal, and determines that the digital signal corresponds to a red (R) signal, a green (G) signal, or a blue (B) signal. The controller includes three independent lookup tables (LUTs) used as red (R) signals, green (G) signals, and blue (B) signals, respectively.

1 is a look up table (LUT) for use as R, G, and B color data signals in an organic light emitting diode according to the prior art.

Each lookup table (LUT) has a plurality of index values corresponding to other digital data signals.

As shown in FIG. 1, the lookup tables LUT-R, LUT-G, and LUT-B have different index values corresponding to different digital data signals. For example, when the 6-bit digital data signal is "111110", the lookup table LUT-R has an "11111111" index value, and the lookup table LUT-G has an "10111111" index value, and the lookup table (LUT-B) has an index value of "11011111".

The lookup tables LUTS may convert the number of bits of the digital data signal as well as the digital data signal value. In particular, when a 6-bit digital data signal is input to the controller and processed through a lookup table (LUT), an 8-bit digital data signal having another bit stream is output from the controller. This 8-bit digital data signal is supplied to the data driver. The number of bits of the digital data signal is extended to perform gamma control, and display a desired gray scale.

The field display device may use different lookup tables (LUTS) for the R, G and B signals to obtain color coordinates, gamma control and contrast ratios. In the organic light emitting display device, color pixels such as a red (R) pixel, a green (G) pixel, and a blue (B) pixel may have different efficiencies. The other lookup table LUTS having different index values for the red (R) signal, the green (G) signal, and the blue (B) signal may compensate for the difference between the R, G, and B pixels.

However, according to the application of the same source voltage VDD, the R pixel, the G pixel, and the B pixel cannot display the desired grayscale image. When the same source voltage is applied to the driving transistors of the R pixel, the G pixel, and the B pixel, different color reactions may appear in the R pixel, the G pixel, and the B pixel. The source voltage VDD and the lookup table LUTS may be determined and cannot be controlled only when the electric field display device is operated.

Furthermore, regardless of the brightness of the surrounding environment, the image is represented by the full white brightness of the conventional electric field display device.

As described above, the source voltage VDD appears, cannot be changed in response to the surrounding environment, and power consumption increases.

Therefore, the conventional electric field display device needs a driving system and a driving method that improve the above problems.

Accordingly, the present invention has been made to solve the above-mentioned problems of the prior art, the present invention is to separate the digital R, G, B data level input to the panel by using the same root (LUT) to separate the gamma from the outside It is an object of the present invention to provide a driving system and a driving method of the electroluminescent device capable of controlling.

An electroluminescent device driving system for achieving the object of the present invention, the organic light emitting device (OLED) panel consisting of a plurality of pixels including a red pixel, a green pixel and a blue pixel; A control unit for receiving first digital data and converting the first digital data into second digital data for gradation display; And a level shift unit converting the second digital signal into a data voltage, supplying the data voltage to the pixels, and supplying different source voltages to the red, green, and blue pixels, respectively. It is characterized by.

In addition, the method of driving an electroluminescent device according to the present invention comprises the steps of: changing analog data into first digital data; Converting the first digital data into gradation display second digital data; Continuously activating a plurality of pixels in response to the second digital data; Converting the TKDRL second digital data into a data voltage; Supplying the data voltage to a plurality of pixels including red pixels, green pixels, and blue pixels; And supplying another source voltage to the red pixel, the green pixel, and the blue pixel.

Hereinafter, a driving system and a driving method of an electroluminescent device according to the present invention will be described in detail with reference to the accompanying drawings.

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

3 is a diagram illustrating a unit pixel including an organic light emitting display device and a driving circuit in the organic light emitting display device according to the present invention.

4 is a timing diagram of digital driving of the organic light emitting display device of FIG. 2 in the organic light emitting display device according to the present invention.

5 is a view illustrating a control unit for use in the organic light emitting display device of FIG. 2 in the organic light emitting display device according to the present invention.

6 is an example of a look-up table (LUT) included in the controller of FIG. 5 in the organic light emitting diode according to the present invention.

As shown in FIG. 2, the EL display device 100 according to the present invention includes an organic light emitting diode (OLED) panel 160. The organic light emitting diode panel 160 includes a plurality of pixels. The pixel displays an R color, a G color, or a B color. The pixel includes an organic light emitting diode that emits red, green, or blue light displaying an R, G, or B color.

In addition, the scan driver 150 and the level shift unit 130 are connected to the organic light emitting display panel 160 to drive the OLED panel 160. The scan driver 150 continuously activates the pixels, and the level shift fitter 130 supplies the respective data voltages to the pixels. The pixels emit light corresponding to each data voltage. The EL display device 100 includes a control unit 140. An analog / digital (A / D) converter 110 is connected to the control unit 140 to convert analog data into digital data. The digital data is supplied to the controller 140.

The controller 140 supplies data to the frame memory unit 120 and the scan driver 150. The frame memory unit 120 passes data through the latch 125. The latch 125 holds the data in a range that latches data corresponding to the number of pixels per row ROW of the OLED panel 160. Thus, the latch 125 passes the data to the level shift unit 130 at the same time. The R data, G data, and B data are converted into data voltages and output from the level shift unit 130 to the OLED panel 160. The level shift unit 130 operates to set different source voltages depending on the R data, the G data, and the B data, as described later.

The EL display device 100 includes an optical sensor (not shown) connected to the controller 140. The optical sensor (not shown) senses the brightness level in the surrounding environment. The controller 140 receives a sensing signal BS from the optical sensor (not shown) and supplies a control signal CS to the level shift unit 130.

According to the control signal CS, the level shift unit 130 may supply a high source voltage or a low source voltage.

The EL display device 100 operates in a bright environment and can be supplied with a high source voltage. On the other hand, when the EL display device 100 operates in a relatively dark environment, a low source voltage can be supplied.

FIG. 3 is a view for explaining the structure of a pixel 101 for use in the organic EL display device 100 of FIG.

Referring to FIG. 3, a pixel 101 according to the present invention is included in an OLED panel 160. The pixel 101 emits red light applied to data passing through the data line DL. In another embodiment, the pixel 101 may emit blue light or green light. As shown in FIG. 3, the pixel 101 includes an EL cell (OLED) 103 and a cell driver 105. The cell driver 105 is composed of an EL cell (OLED) 103, three PMOS transistors T1, T2, and T3 and a storage capacitor Cs for driving the EL cell OLED 103.

The cell driver 105 is a switch connected between the storage capacitor Cs connected to the power line PL and the data line DL and the storage capacitor Cs and controlled by the light emitting scan line SLp. The first PMOS transistor T1 for switching, the second PMOS transistor T2 for switching connected between the power supply line PL and the storage capacitor Cs and controlled by the non-emission scan line SLe, and the power supply line It is composed of a driving third PMOS transistor T3 connected between the VDD-R and the EL cell (OLED) 103 and controlled by the storage capacitor Cs.

In addition, the emission scan line SLp includes a writing signal, that is, a program signal PS for turning on the first PMOS transistor T1 at the emission time LT of each subframe SF. ). The first PMOS transistor T1 is turned on by the program signal T1 to charge the data signal to the storage capacitor Cs, thereby driving the third PMOS transistor T3 according to the charging voltage during the light emission time LT. Turn on / turn off.

The non-emission scan line SLe supplies an erase signal ES for turning on the second PMOS transistor T2 at the non-emission time UT of each subframe SF. The second PMOS transistor T2 is turned on by the erase signal ES to discharge the storage capacitor Cs to turn off the third PMOS transistor T3 during the non-emission time UT.

4 illustrates a digital driving method of the EL display device 100 for expressing the gradation of a digital data signal.

Each frame is divided into a plurality of subframes SF corresponding to each bit of the digital data signal. As an example, the 12-bit data signal represents 256 gray levels, and one frame is divided into 12 subframes SF1 to SF12 corresponding to the 12-bit digital data signal.

Here, the first subframe SF1 of the 12 subframes SF1 to SF12 corresponds to the least significant bit of the digital data signal, and the twelfth subframe SF12 corresponds to the most significant bit of the digital data signal.

Each of the twelve subframes SF1 to SF12 is divided into a light emission time LT1 to LT12 and a non-light emission time UT1 to UT12. At this time, the light emission time LT1 to LT12 of each subframe SF1 to SF12 is " 1: 2: 4: 8: 16: 32 " for representing 2 ⁸ (256) gray levels of a 12-bit digital data signal. You can use any code, such as binary code, such as "..." or binary code, such as "1: 2: 4: 6: 10: 14: 19 ....".

During each subframe period SF1 through SF12, the EL display device sequentially scans all the pixels in the vertical direction, for example, from the top to the bottom of the EL panel to emit light. Accordingly, the light emission times LT1 to LT12 of the respective subframes SF1 to SF12 follow the diagonal lines as shown in FIG. 4 within each of the subframes SF1 to SF12.

Thus, the sum of the light emission times LT1 to LT12 in each of the subframes SF1 to SF12 during one frame can represent the desired gray level of the image.

The desired picture is represented here as in FIG. 2 using a non-binary code. During the divided subframe, the EL display device 100 emits light from the top to the bottom in the V-scan (vertical) direction at different times, and expresses the gray scale by the sum of the respective emission times.

The source voltage is supplied to the power line VDD-R. The source voltage VDR may be supplied to the third transistor T3. The source voltage VDR may be a high voltage or a low voltage depending on a surrounding environment. When the environment is at a high brightness level, high voltage is supplied to the source voltage (VDR). On the other hand, when the surrounding environment is at a low brightness level, the low voltage is supplied to the source voltage VDR. When the pixel 101 emits green light or blue light, the source voltage value for the pixel 101 may be different. Depending on whether the pixel 101 emits red light, green light or blue light, a different value of the source voltage can be supplied.

The source voltage VDR is supplied to the drain terminal of the third transistor T3. The level shift unit 130 converts the digital data signal into a corresponding data voltage. The data voltage is supplied to the gate terminal of the third transistor T3. The source voltage VDR is supplied to the drain terminal of the third transistor T3. When another source voltage is supplied to the red pixel, the green pixel, and the blue pixel, the voltage between the gate terminal and the drain terminal of the third transistor T3 is different in the red, green, and blue pixels.

As a result, because other source voltages are supplied, the voltage between the gate and drain terminals of the driving transistor can be controlled, and the gamma curve can be controlled.

By supplying different source voltages to the red pixels, the green pixels, and the blue pixels, the gamma curve can be controlled and the desired gray scale can be expressed. Thus, no other lookup table (LUT) for the red data signal, the green data signal and the blue data signal is needed. A single lookup table (LUT) is used for the red, green and blue data signals. 5 illustrates the structure of the controller 400 of the organic light emitting display device according to the present invention.

As shown in FIG. 5, the controller 140 includes a single lookup table 115 and a scan controller 145. The single lookup table 115 is applied to the digital data signal despite the red, green or blue data signal. The digital data signal is converted into a digital data signal having a bit number suitable for gray scale display. The scan controller 145 receives a digital data signal and supplies a control signal to the scan driver 150. The scan driver 150 supplies a data write signal and a data erase signal to control the pixels to turn off the light emission during the non-emission time and to emit light during the light emission time.

The single lookup table 115 includes a plurality of index values in response to the digital data signal.

6 shows a lookup table 115 for use in accordance with red, green and blue signals.

In the case of the red, green and blue data signals of " 111110 ", the lookup table LUT converts it to a data signal of " 11111111 ". The converted data has 8 bits indicating gray scale. The converted data is supplied to the frame memory unit 120 and the level shift 130. The level shift unit 130 converts a data signal, for example, "11111111" into a corresponding data voltage and supplies it to the pixels of the OLED panel 160. The R data, the G data or the B data are independently processed and output from the level shift unit 130. In addition, the level shift unit 130 supplies another source voltage to the red pixel, the green pixel, or the blue pixel. The voltage between the gate and drain terminals of the driving transistor, such as the third transistor T3, is controlled.

Since the voltage between the gate terminal and the drain terminal of the driving transistor is adjusted differently for each of the red, green, or blue pixels, the same single lookup table (LUT) is used to adjust the gamma curve even if the R, G, and B pixel efficiency is different. Can be.

In the EL display device, the contrast ratio due to the control of the data voltage does not decrease. The EL display device can externally adjust the gamma curve by using a different source voltage instead of some lookup tables (LUTs) stored in the controller. Furthermore, the red, green and blue pixels can be controlled independently and independently.

As described above, according to the driving system and driving method of the organic light emitting display device according to the present invention, since the voltage between the gate terminal and the drain terminal of the driving transistor is adjusted differently for each red, green or blue pixel, R, Even if the G and B pixel efficiencies are different, the same single lookup table (LUT) can be used to adjust the gamma curve.

In addition, according to the EL display device of the present invention, the contrast ratio according to the control of the data voltage does not decrease. The EL display device can externally adjust the gamma curve by using a different source voltage instead of some lookup tables (LUTs) stored in the controller. Furthermore, the red, green and blue pixels can be controlled independently and independently.

On the other hand, while described above with reference to a preferred embodiment of the present invention, those skilled in the art various modifications of the present invention without departing from the spirit and scope of the invention described in the claims below And can be changed.

Claims (16)

An organic light emitting diode (OLED) panel including a plurality of pixels including a red pixel, a green pixel, and a blue pixel; A control unit for receiving first digital data and converting the first digital data into second digital data for gradation display; And A level shift unit converting the second digital signal into a data voltage, supplying the data voltage to the pixels, and supplying a different source voltage to each of the red, green, and blue pixels. A drive system for an electroluminescent device, characterized in that. The driving system of claim 1, wherein the control unit comprises a single look up table for storing a plurality of index values. The electroluminescence device of claim 1, wherein the first digital data comprises a lookup table (LUT) applied to a red data signal, a green data signal, a blue data signal, and the red, green, and blue data signals. Device driving system. 4. The driving system of claim 3, wherein the red, green, and blue data signals are converted into a bit stream of corresponding red, green, and blue data signals. The driving system of claim 1, wherein the other source voltage is determined according to a gamma curve. The driving system of claim 1, wherein each pixel comprises a driving transistor, another source voltage supplied to a drain terminal of the driving transistor, and a data voltage supplied to a gate terminal of the driving transistor. . 2. The driving system of claim 1, wherein the first digital data is composed of N bits, and the second digital data is composed of M bits larger than the N bits. 8. The driving system of claim 7, further comprising a scan driver for continuously activating the plurality of pixels and supplying a control signal from the controller. 9. The driving system of claim 8, wherein the scan driver activates a plurality of pixels that emit and not emit light in response to the second digital data. The driving system of claim 1, further comprising a frame memory unit received from the control unit and storing the second digital data. Converting analog data into first digital data; Converting the first digital data into gradation display second digital data; Continuously activating a plurality of pixels in response to the second digital data; Converting the second digital data into a data voltage; Supplying the data voltage to a plurality of pixels including red pixels, green pixels, and blue pixels; And And supplying another source voltage to the red pixel, the green pixel, and the blue pixel. 12. The method of claim 11, wherein the converting the first digital data into the second digital data comprises applying a lookup table (LUT) to the first digital data. Driving method. The method of claim 12, wherein the converting the first digital data into the second digital data comprises applying a single lookup table (LUT) to the red digital data, the green digital data, and the blue digital data of the first digital data. A method of driving an electroluminescent element. The method of claim 11, wherein the supplying of the other source voltage comprises: Supplying a first source voltage to the red pixel; Supplying a second source voltage to the green pixel; And supplying a third source voltage to the blue pixel. 15. The method of claim 14, wherein the supplying of the other source voltages further comprises controlling the drain-gate voltages of the red, green, and blue pixels. 12. The method of claim 11, further comprising storing second digital data in the frame memory unit.

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