KR20180067106A - Orgainc emitting diode display device - Google Patents

Abstract

The present invention relates to an organic light emitting diode display device capable of preventing a sensing deviation between sensing channels by removing the offset component of a current integrator in a sensing mode. In one embodiment, a relative offset value of the current integrator and an offset compensation value using the same are detected by using a cross sensing value and a normal sensing value of a sensing line in a sensing mode. A characteristic of each pixel is sensed by using a data signal for sensing to which the offset compensation value is applied. So, the offset value of the current integrator can be canceled. The organic light emitting diode display device includes a display panel, a memory, a data driver, and a timing controller.

Description

[0001] ORGANIC EMITTING DIODE DISPLAY DEVICE [0002]

The present invention relates to an organic light emitting diode (OLED) display device capable of preventing an interchannel sensing deviation due to an offset of a current integrator.

2. Description of the Related Art Recently, flat panel display devices that display images using digital data include a liquid crystal display (LCD) using liquid crystal, an OLED display using an organic light emitting diode (OLED) An electrophoretic display (EPD) and the like.

Of these, OLED display devices are self-luminous devices that emit organic light-emitting layers by recombination of electrons and holes, and are expected to be a next-generation display device because of their high luminance, low driving voltage, and ultra thin films.

Each of the plurality of pixels constituting the OLED display device includes an OLED element and a pixel circuit which independently drives the OLED element. The pixel circuit regulates the brightness of the OLED element by controlling the current Ids driving the OLED element by a driving thin film transistor (hereinafter referred to as TFT) according to the driving voltage Vgs corresponding to the data signal.

However, since characteristics such as the threshold voltage (hereinafter referred to as Vth) and mobility of the driving TFT are not uniform for each pixel in the OLED display device, the current Ids differs from the same driving voltage Vgs to cause a luminance deviation.

In order to solve this problem, the OLED display senses the characteristic of each pixel, detects and stores a compensation value for compensating for the characteristic deviation of each pixel using the sensing result, And uses external compensation technology to compensate the data.

As a method of sensing current among external compensation methods, a method of sensing a pixel current using a current integrator for each sensing channel is known. However, in the sensing method using the current integrator, there is an error due to the offset of the current integrator itself existing in each sensing channel. Such an error not only directly affects the sensing value but also affects the compensation data for adjusting the luminance uniformity of the display device.

For example, even if the same current is supplied from the pixels to be sensed, the sensing value changes due to the offset difference of the current integrators between the sensing channels, and the compensation data extracted from the sensing value includes an error, When each pixel is driven by using the compensated data signal, a picture quality defect such as a vertical line is displayed on the screen.

The present invention provides an OLED display device capable of preventing a sensing deviation between sensing channels by removing an offset component of a current integrator in a sensing mode.

The sensing mode of the OLED display according to an exemplary embodiment includes an initial sensing step including a normal sensing step and a cross sensing step under the control of a timing controller and a pixel sensing step for sensing characteristics of each pixel after the initial sensing step do.

In the normal sensing step, the data driver senses each sensing line connected to the pixel driven by the sensing data through the normal path via the current integrator of each sensing channel, and outputs it as a normal sensing value.

In the cross sensing step, the data driver senses each sensing line connected to the pixel driven by the sensing data through a cross path via the current integrator of the adjacent sensing channel, and outputs the sensing result as a cross sensing value.

The timing controller calculates an offset compensation value for compensating the offset of the current integrator of each sensing channel by comparing the normal sensing value and the cross sensing value and stores the offset compensation value in the memory. Then, in the pixel sensing step, The offset compensation value and the compensation value of each pixel are applied to compensate the sensing data.

The OLED display according to an exemplary embodiment of the present invention detects a relative offset value of the current integrator and an offset compensation value using the normal sensing value and the cross sensing value of the sensing line in a sensing mode, It is possible to offset the offset value of the current integrator by sensing the characteristics of each pixel.

Accordingly, it is possible to prevent the sensing deviation between the sensing channels due to the offset of the current integrator, and to accurately compensate the characteristics of each pixel, thereby preventing the image quality deterioration due to the inter-channel sensing deviation.

1 is a block diagram schematically illustrating an OLED display according to an embodiment of the present invention.
2 is an equivalent circuit diagram showing an example of the pixel configuration shown in FIG.
3 is a block diagram illustrating a current sensing device of an OLED display according to an embodiment of the present invention.
4 is a circuit diagram illustrating a sensing unit of a data driver according to an embodiment of the present invention.
5A and 5B are diagrams illustrating a normal sensing operation and a cross sensing operation of the sensing unit shown in FIG.

FIG. 1 is a block diagram schematically showing an OLED display device having a sensing function according to an embodiment of the present invention. FIG. 2 is an equivalent circuit diagram illustrating one pixel configuration shown in FIG. 1, FIG. 7 is a block diagram schematically illustrating a current sensing device of an OLED display according to an embodiment.

1, an OLED display according to an exemplary embodiment includes a display panel 100, a panel driver 130 including a data driver 110 and a gate driver 120, a timing controller 140, Memory 150 and the like.

The OLED display device sets a compensation value for compensating for the nonuniformity characteristic of each pixel in advance and stores the compensation value in the memory 150. The OLED display device reflects the driving characteristic of each pixel, And updates the stored compensation value. For example, in at least one sensing period such as a power-on time, a power-off time, a blank period of each frame, or the like, the OLED display operates in a sensing mode to sense driving characteristics of each pixel, And updates the compensation value of each pixel stored in the memory 150. [ In the memory 150, a plurality of compensation values for compensating TFT Vth, mobility, Vth of OLED, etc. of each pixel may be stored for each pixel.

The display panel 100 displays an image through a pixel array in which pixels P having OLED elements are arranged in a matrix form. The pixels P include red (R), green (G), and blue (B) pixels, and further include a W (White) pixel for brightness enhancement. Each pixel P has an OLED element and a pixel circuit which independently supplies a current proportional to the data signal supplied from the data driver 110 to the OLED element.

The pixel circuit may include the first and second switching TFTs ST1 and ST2, the driving TFT DT and the storage capacitor Cst as illustrated in FIG. 2, but the present invention is not limited to the configuration of FIG. 2, May be used.

The OLED element has an anode connected to the driver TFT (DT), a cathode connected to the low potential voltage (EVSS), and a light emitting layer between the anode and the cathode, and light proportional to the amount of current supplied from the driver TFT Occurs.

The first switching TFT ST1 is turned on by the control of the gate line GLn1 to transfer the data voltage Vdata from the data line DL to the gate electrode of the driving TFT DT. The second switching TFT ST2 is turned on by the control of the gate line GLn2 to transfer the reference voltage Vref from the sensing line SL to the source electrode of the driving TFT DT, And transfers the current of the TFT DT to the sensing line SL. The first and second switching TFTs ST1 and ST2 may be controlled by different gate lines GLn1 and GLn2 or may be controlled by the same gate line GL.

The storage capacitor Cst charges the voltage Vdata-Vref between the gate electrode and the source electrode of the drive TFT DT reflecting the data voltage Vdata and supplies the voltage Vdata-Vref to the drive voltage Vgs of the drive TFT DT.

The driving TFT DT controls the current supplied from the high potential voltage supply line PL to supply a current Ids proportional to the driving voltage Vgs to the OLED element to adjust the brightness of the OLED element.

The gate driver 120 drives the gate lines GL of the display panel 100 under the control of the timing controller 140. During the display mode and the sensing mode, the gate driver 120 drives the gate lines GL on a scan line basis.

The data driver 110 includes a data supply unit 210 for supplying a data signal to the display panel 100 and a sensing unit 220 for sensing the display panel 100 as shown in FIG.

The data supply unit 210 converts the display image data supplied from the timing controller 140 into analog data signals under the control of the timing controller 140 during the display mode and outputs the analog data signals to the data lines DL of the display panel 100 And the sensing unit 220 supplies the reference signal to the sensing line SL of the display panel 100.

Under the control of the timing controller 140 during the sensing mode, the data supply unit 210 converts the sensing data supplied from the timing controller 140 into an analog data signal and supplies the analog data signal to the display panel 100. The sensing unit 220 Supplies a reference signal to the sensing line SL of the display panel 100. [ Next, the sensing unit 220 senses the current reflected by the characteristic of each pixel P driven by the sensing data, and supplies the sensing information of each pixel to the timing controller 140. The pixel current sensed from each pixel P has characteristic information of the driving TFT such as Vth and mobility of the driving TFT DT and deterioration information of the OLED element such as Vth of the OLED element, The pixel current varies depending on the Vth of the OLED element, the mobility, and the Vth of the OLED element.

In particular, in the initial sensing step prior to the pixel sensing step of sensing the characteristics of each pixel P in the sensing mode, the data driver 110 controls the sensing unit 220 using the sensing data under the control of the timing controller 140 The second sensing operation for detecting the offset component of the current integrator existing in each sensing channel of the current sensing channel is performed first.

Specifically, under the control of the timing controller 140, the initial sensing step includes a normal sensing step and a cross sensing step.

The data supplying unit 210 and the sensing unit 220 control the pixels P of at least one scan line by using the sensing data and the reference signal under the control of the timing controller 140 in the normal sensing step during the initial sensing step The sensing unit 220 senses each sensing line SL through a normal path using a current integrator of the sensing channel and supplies the sensing signal to the timing controller 140 as a normal sensing value.

The data supplying unit 210 and the sensing unit 220 are controlled by the timing controller 140 so as to detect pixels P of at least one scan line using the sensing data and the reference signal in the cross sensing step of the initial sensing step The sensing unit 220 senses each sensing line SL through a cross path using a current integrator of another adjacent sensing channel and supplies the sensing signal to the timing controller 140 as a cross sensing value .

The timing controller 140 controls the driving timings of the gate driver 120 and the data driver 110. [ In addition, the timing controller 140 compensates the image data to be supplied to each pixel using the compensation value of each pixel stored in the memory 150, and supplies the compensated data to the data driver 110. To this end, the timing controller 140 includes a compensation value extractor 240 and a data processor 250, as shown in FIG.

The compensation value extracting unit 240 extracts a compensation value for compensating for the nonuniform characteristic of each pixel by using the sensing information of each pixel supplied from the data driver 110 during the sensing mode, Update.

In particular, in the initial sensing step before the pixel sensing step, the compensation value extractor 240 compares the normal sensing value for each sensing line SL supplied from the data driver 100 with the cross sensing value A relative offset value of each sensing channel (current integrator) for one sensing channel (current integrator) is detected, and an offset compensation value of each sensing channel for compensating the relative offset value is calculated and stored in the memory 150 do.

Specifically, the compensation value extractor 240 calculates a delta, which is a difference between a normal sensing value and a cross sensing value for each sensing channel, and outputs a delta difference of each sensing channel to a reference sensing channel As a relative offset value of each of the other sensing channels. The reference sensing channel may be any one of a plurality of sensing channels. The compensation value extractor 240 determines an offset compensation value of the reference sensing channel for compensating the delta of the reference sensing channel and the offset compensation value using the reference offset compensation value and the relative offset value, The offset compensation value for each sensing channel is stored in the memory 150.

The data processing unit 250 compensates the input image data or the sensing data using the compensation values stored in the memory 150 and outputs the compensated data to the data driver 110 in each of the display mode and the sensing mode.

In particular, when sensing the characteristics of each pixel in the pixel sensing step, the data processing unit 250 calculates an offset compensation value for each sensing channel calculated in the previous initial sensing step and stored in the memory 150, And supplies the corrected sensing data to the data driver 110. The data driver 110 supplies the sensing data to the data driver 110, Accordingly, when the characteristics of each pixel are sensed, the offset value of the current integrator existing in the sensing channel can be canceled by the offset compensation value applied to the sensing data.

4 is a circuit diagram showing a configuration of a sensing unit 220 of the data driver 100 according to an embodiment of the present invention.

4, the sensing unit 220 includes a current-to-voltage conversion unit 222 that integrates the input current for each channel from the display panel 100 and outputs the integrated current as a sensing voltage, (Hereinafter referred to as ADC) 226 for converting the supplied sensing voltage into digital data and outputting it as sensing information to the timing controller 140, and a current-to-voltage converter 222 (Hereinafter, referred to as " MUX ") 224.

The current-to-voltage conversion unit 222 includes sensing channels CH1 to CHn individually connected to a plurality of sensing lines SL1 to SLn of the display panel 100. FIG. The sensing channels CH1 to CH4 individually connected to the lines SL1 to SL4 will be described with reference to FIG.

The sensing channels CH1 to CH4 are connected to the first switches SW11 to SW41 individually connected to the sensing lines SL1 to SL4 and the first to third switches SW11 to SW41 and the current integrators A1 to A4, the sampling / holders SH1 to SH4 individually connected to the current integrators A1 to A4 and the sensing lines SL1 to SL4 are connected to the current integrators A1 to A4 of the adjacent channels individually And second switches SW12 to SW42 connected to the second switch SW2.

Each of the current integrators A1 to A4 further includes a reset switch RST and a capacitor Cfb connected in parallel between the input and output terminals.

The current-voltage conversion unit 222 may further include one dummy sensing channel CHn + 1 connected to the last sensing channel or the second switch SWn2 of the first sensing channel in the cross sensing step during the initial sensing step have. The dummy sensing channel CHn + 1 is connected between the current integrator An + 1, the sampling / holder SHn + 1 connected to the second switch SWn2 of the adjacent channel and the input / output terminals of the current integrator An + A reset switch RST and a capacitor Cfb connected in parallel to each other, and is used only in the cross sensing step.

The first switches SW11 to SW41 are turned on in the normal sensing step and in the pixel sensing step in the initial sensing step to connect the sensing lines SL1 to SL4 of the display panel 100 to the current integrators A1- A4).

The second switches SW12, SW22, SW32, ..., SWn2 are turned on in the cross sensing step during the initial sensing step to connect the sensing lines SL1 to SL3 of the display panel 100 to the current integrator (A2, A3, A4, ..., An + 1).

Each of the current integrators A1 to An + 1 receives the input current through the first input switch SW # 1, # = 1 to n or the second input switch SW # 2, # = 1 to n And the other input terminal is connected to the reference voltage Vref to integrate the input current and output it as the sensing voltage to the output terminal. Each of the sampling / holders SH #, # = 1 to n + 1 is connected to the corresponding current integrator A # And outputs the sensing voltage.

The reset switch RST is turned on in the reset period of each current integrator A # so that the input terminals (-, +) and the output terminal of the current integrator A # and the sensing line SL # Vref). The reset switch RST is then turned off in the sensing period of each current integrator A # so that each current integrator A # acts as a current integrator and the current input through the sensing line SL # ). As the sensing time elapses, the potential difference across the capacitor Cfb increases due to the current input to the inverting input terminal (-) of the current integrator A # so that the potential of the output terminal gradually increases from the reference voltage Vref , And the sampling / holder (SH #) samples and holds the reduced voltage and outputs it as the sensing voltage. Since the slope increases as the magnitude of the current increases, the sensing voltage sampled at the same time also increases. Through this principle, the current integrator A # converts the input current into a sensing voltage and outputs the sensing voltage. The sampling / holder SH # samples and holds the output voltage of the current integrator A # and outputs it as a sensing voltage.

The MUX 224 sequentially connects the plurality of sensing channels CH1 to CHn + 1 to the ADC 226 and successively outputs the sensing voltages held in the plurality of sensing channels CH1 to CHn + 1 to the ADC 226 Output. The ADC 226 converts the sensing voltage into sensing data and outputs it to the timing controller 140.

5A and 5B illustrate operations of the normal sensing step and the cross sensing step of the sensing unit 220 according to an embodiment of the present invention.

5A, the first switches SW11 to SW41 in the sensing unit 220 are turned on in the normal sensing step during the initial sensing step, so that the sensing lines SL1 to SL4 are connected to the sensing channels CH1 to CH4, And the current integrators A1 to A4 of FIG. Accordingly, the sensing unit 220 senses each sensing line SL # through the normal path using the current integrator A # of the sensing channel CH # and supplies the sensed line SL # to the timing controller 140 as a normal sensing value . The normal sensing value of each sensing line SL # using the normal path of the original channel CH # includes the offset Vos # present in the current integrator A # of the original channel CH #.

5B, the second switches SW12 to SW42 in the sensing unit 220 are turned on in the sensing step of the initial sensing step, and the sensing lines SL1 to SL3 are connected to the current integrators A2- A4, respectively. Accordingly, the sensing unit 220 outputs the sensing line SL # to a cross-path using the current integrator A # + 1 or A # -1 of the adjacent sensing channel CH # + 1 or CH # cross path) and supplies the sensing signal to the timing controller 140 as a cross sensing value. The cross sensing value of each sensing line SL # using the cross path of the adjacent channel (CH # + 1 or CH # -1) is equal to the cross sensing value of the current integrator A # + (Vos # + 1 or Vos # -1) existing in the A # 1 or A # -1.

The timing controller 140 uses the normal sensing value and the cross sensing value of each sensing line SL # supplied from the data driver 110 to calculate the relative offset value of the current integrator of each sensing channel CH # And the offset compensation value, and offset the offset value of the current integrator by sensing the characteristic of each pixel by using the sensing data signal to which the offset compensation value is applied.

Accordingly, it is possible to prevent the sensing deviation between the sensing channels due to the offset of the current integrator, and to accurately compensate the characteristics of each pixel, thereby preventing the image quality deterioration due to the inter-channel sensing deviation.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of illustration, Can be carried out within a range. Accordingly, such modifications are deemed to be within the scope of the present invention, and the scope of the present invention should be determined by the following claims.

100: Display panel 110: Data driver
120: gate driver 130: panel driver
140: timing controller 150: memory
210: Data supply unit 220:
240: compensation value extraction unit 250:
222: current-voltage conversion unit 224: MUX
226: ADC

Claims (5)

A display panel including a plurality of pixels;
A memory storing a compensation value for a characteristic of each pixel;
A data driver for supplying sensing data of each pixel to the display panel during sensing mode, sensing the characteristics of each driven pixel through a sensing line and outputting sensing information,
The compensation value of each pixel stored in the memory is applied to compensate for the sensing data of each pixel during the sensing mode and supplied to the data driver and the compensation value of each pixel is calculated from the sensing information supplied from the data driver And a timing controller for extracting and updating the memory,
Wherein the sensing mode includes an initial sensing step including a normal sensing step and a cross sensing step under the control of the timing controller and a pixel sensing step of sensing characteristics of each pixel after the initial sensing step,
In the normal sensing step, the data driver senses each sensing line connected to a pixel driven by the sensing data through a normal path via a current integrator of each sensing channel and outputs the sensing signal as a normal sensing value,
In the cross sensing step, the data driver senses each sensing line connected to a pixel driven by the sensing data through a cross path via a current integrator of an adjacent sensing channel and outputs the sensed cross sensing value,
The timing controller calculates an offset compensation value for compensating an offset of the current integrator of each sensing channel by comparing the normal sensing value and the cross sensing value and stores the offset compensation value in the memory, And compensates the sensing data by applying an offset compensation value of each sensing channel and a compensation value of each pixel. The method according to claim 1,
Wherein the data driver includes a data supply unit for supplying the sensing data, and a sensing unit having sensing channels connected to the sensing lines,
Each sensing channel of the sensing unit
A current integrator provided in each sensing channel, a sampling / holder for sampling and holding the output voltage of the current integrator,
A first switch for connecting each of the sensing lines to a current integrator belonging to the corresponding channel,
And a second switch for connecting each of the sensing lines to a current integrator belonging to an adjacent channel. The method of claim 2,
The first switch is turned on in the normal sensing step and the pixel sensing step,
And the second switch is turned on in the cross sensing step. The method of claim 2,
The sensing unit
Further comprising a dummy sensing channel adjacent to the first or last sensing channel,
Wherein the dummy channel comprises a dummy current integrator connected to a second switch of an adjacent sensing channel, and a dummy sampling and holder. The method according to any one of claims 1 to 4,
The timing controller
A relative offset value of each of the other sensing channels for one of the reference sensing channels is detected based on the computed result of the delta calculation of the normal sensing value and the cross sensing value for each sensing line and the relative offset value is compensated And calculates the offset compensation value.

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