KR102578839B1 - Method and apparatus for sensing current of orgainc emitting diode display device - Google Patents

Abstract

The present invention relates to a current sensing method and device for an OLED display device that can reduce noise and enable low-current sensing of each pixel using simultaneous sensing of pixels of multiple scan lines. One embodiment includes a sensing mode During each scan period, pixels of a plurality of scan lines are simultaneously driven, and pixels of a plurality of scan lines simultaneously driven in each scan period are simultaneously sensed.

Description

Current sensing method and device for organic light emitting diode display device {METHOD AND APPARATUS FOR SENSING CURRENT OF ORGAINC EMITTING DIODE DISPLAY DEVICE}

The present invention relates to a current sensing method and device for an organic light emitting diode display device that enables low-current sensing of each pixel and reduces noise using simultaneous sensing of pixels of a plurality of scan lines.

Recently, flat display devices that display images using digital data include Liquid Crystal Display (LCD) using liquid crystals, OLED display devices using Organic Light Emitting Diode (OLED), and electrophoretic particles. A representative example is an electrophoretic display (EPD) using .

Among these, the OLED display device is a self-luminous device that emits light in an organic light-emitting layer by recombination of electrons and holes. It has high brightness, low driving voltage, and can be made ultra-thin, so it is expected to be a next-generation display device.

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

However, in OLED display devices, characteristics such as the threshold voltage (Vth) and mobility of the driving TFT are non-uniform for each pixel, so the current (Ids) varies compared to the same driving voltage (Vgs), resulting in luminance deviation. In addition, luminance deviations also occur due to differences in characteristics of OLED devices.

To solve this problem, the OLED display device senses the characteristics of each pixel, uses the sensing results to detect and store a compensation value to compensate for the characteristic deviation of each pixel, and uses the stored compensation value to determine the image to be supplied to each pixel. We use external compensation technology to compensate for data.

Among the external compensation methods, the current sensing method individually senses the current from each pixel, but since the current of each pixel is very low in the hundreds of nA range, it is difficult to sense low current, and the low current sensed is connected to the panel and circuit part. It has a vulnerability of being sensitive to noise caused by power, etc.

For this reason, when the low current sensed from each pixel is affected by noise components and distorted, it is difficult to accurately detect the desired pixel characteristics and corresponding compensation value from the current sensing value, so the current sensing method of the conventional OLED display device is There is a problem that compensation performance deteriorates.

The present invention provides a current sensing method and device for an OLED display device that enables low-current sensing of each pixel and reduces noise using simultaneous sensing of pixels of a plurality of scan lines.

In order to solve the above problem, the current sensing device of the OLED display device according to an embodiment of the present invention includes a display panel including a plurality of pixels, a gate driver that simultaneously drives a plurality of scan lines during each scan period during the sensing mode, and , a data supply unit that supplies data signals to pixels driven in each scan period, and a sensing unit that simultaneously senses pixels of a plurality of scan lines that are simultaneously driven in each scan period.

The sensing unit senses the composite current for a plurality of pixels sharing the corresponding reference line for each sensing channel in the plurality of scan lines driven in each scan period through the corresponding reference line, converts it into composite sensing data, and outputs it.

The calculation unit calculates the sensing data for each of the plurality of pixels through a predetermined operation using the synthetic sensing data supplied from the sensing unit. The compensation value extraction unit extracts the compensation value of each pixel using the sensing data of each pixel supplied from the calculation unit and updates the compensation value of each pixel stored in the memory.

The current sensing method of an OLED display device according to an embodiment of the present invention simultaneously drives pixels of a plurality of scan lines in each scan period during the sensing mode and supplies data signals to the simultaneously driven pixels. The current sensing method simultaneously senses the pixels of multiple scan lines that are driven simultaneously in each scan period, senses the composite current for multiple pixels sharing the reference line for each sensing channel through the reference line, and generates the composite sensing data. Convert to The current sensing method calculates sensing data for each of multiple pixels through a predetermined operation using synthetic sensing data. The current sensing method extracts the compensation value of each pixel using the sensing data of each pixel and updates the compensation value of each pixel stored in memory.

Each of n scan lines (n is a natural number greater than or equal to 2) that are driven simultaneously in each scan period are driven simultaneously in combination with other scan lines in other scan periods, and are driven n times during the sensing mode.

During each scan period, the composite current for n pixels sharing the corresponding reference line is sensed for each sensing channel. Each of the n pixels is combined with other pixels that share a reference line and sensed n times during the sensing mode.

Sensing data for each pixel is calculated through a set arithmetic operation using a plurality (>n) of synthetic sensing data supplied for each sensing channel.

One embodiment of the present invention simultaneously senses the current for pixels of multiple scan lines to increase the current size and calculates the sensing value of each pixel through multiple operations on the multiple sensing values to provide a signal to the multiple pixels. Through the simultaneous sensing and calculation process, the low current of each pixel with reduced noise components can be sensed more accurately.

Accordingly, an embodiment of the present invention can detect an accurate compensation value from the sensing value of each pixel by reducing the noise component, and use the compensation value to improve the ability to compensate for the uneven characteristics of each pixel. there is.

1 is a block diagram schematically showing the configuration of a current sensing device of an OLED display device according to an embodiment of the present invention.
FIG. 2 is an equivalent circuit diagram illustrating one pixel configuration applied to FIG. 1.
Figure 3 is a diagram showing a sequential current sensing method of an OLED display device according to an embodiment of the present invention.
Figure 4 is a timing diagram showing a scan waveform for current sensing of an OLED display device according to an embodiment of the present invention.
Figure 5 is a block diagram schematically showing the configuration of an OLED display device according to an embodiment of the present invention.
Figure 6 is a graph showing sensing data for each channel showing the noise reduction effect of the OLED display device according to an embodiment of the present invention compared to the prior art.

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

Referring to FIG. 1, the current sensing device of the OLED display device according to one embodiment includes a display panel 100, a data supply unit 10, a sensing unit 20, an operation unit 30, and a compensation value extractor 40. , a memory 50, a data processing unit 60, etc. The data supply unit 10 and the sensing unit 20 may be built into a data driver that drives the data lines of the display panel 100. The compensation value extraction unit 40 and the image processing unit 60 may be built into the timing controller. The calculation unit 30 may be built into a data driver or timing controller.

The OLED display device pre-sets a compensation value to compensate for the uneven characteristics of each pixel and stores it in the memory 50, and stores the compensation value in the memory 50 by reflecting the driving characteristics of each pixel that change over driving time. Update the saved reward value. For example, in at least one sensing period such as power-on time, power-off time, blank period of each frame, etc., the OLED display device operates in a sensing mode to sense the driving characteristics of each pixel and reflect the sensing results. Thus, the compensation value of each pixel stored in the memory 50 is updated. A plurality of compensation values that compensate for the TFT Vth, mobility, OLED Vth, etc. of each pixel may be stored in the memory 50 for each pixel.

The display panel 100 includes pixels (P1, P2, P3, ...) arranged in a matrix form, but for convenience of explanation, FIG. 1 shows pixels (pixels) representing each of the three scan lines (L1 to L3). P1, P2, P3) are shown. Each pixel P includes an OLED element and a pixel circuit that supplies a current corresponding to a data signal to the OLED element.

The pixel circuit includes first and second switching TFTs (ST1, ST2), a driving TFT (DT), and a storage capacitor (Cst) as illustrated in FIG. 2, but is not limited to the configuration of FIG. 2 and may include pixels of various configurations. circuit may be used.

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

The first switching TFT (ST1) is turned on under the control of the gate line (GL) and transfers 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 under the control of the gate line (GL) to transfer the reference voltage (Vref) from the reference line (RL) to the source electrode of the driving TFT (DT), and is driven in sensing mode. The current from the TFT (DT) is transmitted to the reference line (RL). The first and second switching TFTs (ST1, ST2) may be controlled by the same gate line (GL) or may be controlled by different gate lines.

The storage capacitor (Cst) charges (Vdata-Vref) between the gate electrode and source electrode of the driving TFT (DT) and supplies it as the driving voltage (Vgs) of the driving TFT (DT).

The driving TFT (DT) controls the current supplied from the high potential voltage (EVDD) supply line (PL) and supplies a current (Ids) proportional to the driving voltage (Vgs) to the OLED device to control the brightness of the OLED device.

In each of the display mode and the sensing mode, the data supply unit 10 converts the digital data supplied from the data processing unit 60 into an analog data signal and supplies it to each data line DL of the display panel 100. The data processing unit 60 compensates for data using the compensation value of each pixel stored in the memory 50 and outputs the compensated data to the data supply unit 10 .

In the display mode, pixels P1, P2, and P3 are driven on a per-scan line basis. On the other hand, in the sensing mode, the pixels (P1, P2, P3) are driven in units of a plurality of scan lines (n numbers; n is a natural number of 2 or more), so that multiple pixels of a plurality of scan lines driven simultaneously in each scan period are sensed simultaneously. It can be. Each of the pixels P1, P2, and P3 is driven by a sensing data signal supplied from the data line DL through the first switching TFT (ST1) in the corresponding scan period, and is driven by the sensing data signal supplied through the second switching TFT (ST2). Pixel current reflecting the driving characteristics (TFT characteristics, OLED characteristics) of each pixel is output through the reference line (RL).

Each of the n scan lines that are driven simultaneously in each scan period is also included as one of the n scan lines that are driven in other scan periods, such as the previous or next scan period, and is driven in other scan periods, so during the sensing mode, each scan line is simultaneously driven. It is driven n times and sensed n times while changing the driven scan line.

The sensing unit 20 simultaneously senses n pixels connected to the corresponding reference line RL for each sensing channel on n scan lines that are simultaneously driven in each scan period. Accordingly, the sensing unit 20 senses a composite current obtained by combining the currents of n simultaneously driven pixels through each reference line RL, thereby increasing the size of the sensed current. The sensing unit 20 converts the composite current of n simultaneously sensed pixels into digital composite sensing data and supplies it to the calculation unit 30. For example, the sensing unit 20 may integrate the composite current sensed through a current integrator, convert it into a voltage, and then convert it into composite sensing data through an analog-to-digital converter (ADC).

The calculation unit 30 performs an arithmetic operation using n synthetic sensing data supplied from the sensing unit 20 to detect pixel information for each of the n pixels and outputs each pixel information to the compensation value extraction unit 40. The compensation value extraction unit 40 extracts the compensation value of each pixel from each pixel information supplied from the calculation unit 30 and updates the compensation value of the memory 50.

Figure 3 is a diagram sequentially showing the current sensing process of the OLED display device according to an embodiment of the present invention, and as shown in Figure 4, when two scan lines are driven simultaneously in each scan period, one sensing channel is illustrated. will be.

Referring to FIGS. 3(a) and 4, two scan lines (L1, L2) are generated by scan pulses simultaneously supplied to the first and second gate lines (GL1, GL2) in the first sensing period (#1). These are driven simultaneously, and the sensing unit 20 simultaneously detects two pixels (P1, P2) of two scan lines (L1, L2) through a reference line (RL) shared by the pixels (P1, P2, and P3). Sensing. Accordingly, the sensing unit 20 generates a first composite current (A+B) in which the current (A) of the first pixel (P1) and the current (B) of the second pixel (P2) are synthesized through the reference line (RL). ) is sensed.

Referring to FIGS. 3(a) and 4, two scan lines (L2, L3) are supplied simultaneously to the second and third gate lines (GL2, GL3) in the second sensing period (#2). These are driven simultaneously, and the sensing unit 20 simultaneously senses two pixels (P2, P3) of two scan lines (L2, L3) through the corresponding reference line (RL). Accordingly, the sensing unit 20 generates a second composite current (B+C) in which the current (B) of the second pixel (P2) and the current (C) of the third pixel (P3) are synthesized through the reference line (RL). ) is sensed.

Referring to FIGS. 3(a) and 4, two scan lines (L1, L3) are supplied simultaneously to the first and third gate lines (GL1, GL3) in the third sensing period (#3). These are driven simultaneously, and the sensing unit 20 simultaneously senses the two pixels (P1 and P3), thereby transmitting the current (A) of the first pixel (P1) and the current (A) of the third pixel (P3) through the reference line (RL). (C) senses the third synthesized current (A+C).

The first pixel (P1) of the first scan line (L1) is sensed simultaneously with the second pixel (P2) of the second scan line (L2) in the first sensing period, and the third scan line (L2) is sensed simultaneously in the third sensing period. It is sensed simultaneously with the third pixel (P2) of L3). The second pixel (P2) of the second scan line (L2) is sensed simultaneously with the first pixel (P1) of the first scan line (L1) in the first sensing period, and the third scan line ( It is sensed simultaneously with the third pixel (P2) of L3). In other words, it can be seen that each of the first to third pixels (P1, P2, and P3) is sensed twice in combination with other pixels.

In this way, the sensing unit 20 simultaneously senses three pixels (P1, P2, P3) of three scan lines through the corresponding reference line (RL) in three different combinations, two pixels at a time, as shown in Table 1 below. By doing so, three composite currents with different pixel combinations (A+B = x, B+C = y, C+A = z) are sequentially sensed and digitally converted to produce Output three synthetic data (x, y, z) with different combinations.

Sensing period #One #2 #3 sensing current x = A+B y = B+C z = C+A

The calculation unit 30 calculates the pixel for each of the three pixels (P1, P2, and P3) through the four arithmetic operations shown in Equation 2 below using the three synthetic data (x, y, z) supplied from the sensing unit 20. Calculate information (A, B, C) respectively. For example, Equation 2 below used in the calculation unit 30 can be determined based on the principle of Equation 1 below.

<Equation 1>

x = A+B, y = B+C, z = C+A

▶ x-y = A-C, y-z = B-A

▶ (A-C) - (B-A) = (x-y)-(y-z)

▶ 2A-(C+B) = x-2y+z

▶ 2A-y = x-2y+z

▶ 2A = x-y+z

<Equation 2>

A = (x-y+z)/2, B = x-{(x-y+z)/2}, C = y-{x-{(x-y+z)/2}}

As such, an embodiment of the present invention can increase the size of the sensed current by simultaneously driving a plurality of scan lines and simultaneously sensing a plurality of pixels sharing the same reference line, thereby reducing noise margin. immunity) can be improved, and noise components can be canceled out during calculations using multiple synthetic currents. Accordingly, an embodiment of the present invention can easily detect accurate low-current pixel characteristics and compensate for uneven luminance of each pixel by detecting an accurate compensation value from accurate pixel characteristics, thereby improving the image quality of the OLED display device. can be improved.

Figure 5 is a block diagram briefly showing the configuration of an OLED display device with a current sensing function according to an embodiment of the present invention.

Referring to FIG. 5, an OLED display device according to an embodiment includes a display panel 100, a panel driver 130 including a data driver 110 and a gate driver 120, a timing controller 140, and a memory 600. ) and power supply, etc.

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 gate driver 120 drives the gate lines GL (FIG. 2) of the display panel 100 under the control of the timing controller 140. During the display mode, the gate driver 120 drives the gate lines on a scan line basis. During the sensing mode, the gate driver 120 drives the gate lines in units of a plurality of scan lines, and in each scan period, the gate lines included in the plurality of scan lines are driven simultaneously.

The data driver 110 converts the digital data signal supplied from the timing controller 140 into an analog data signal and supplies it to the data line (DL; FIG. 2) of the display panel 100 and the reference line of the display panel 100. A reference signal is supplied to (RL; Figure 2). During the display mode, the data driver 110 converts the display image data signal supplied from the timing controller 140 into an analog signal and supplies it to the display panel 100. During the sensing mode, the data driver 110 converts the sensing data signal supplied from the timing controller 140 into an analog signal and supplies it to the display panel 100, and senses the current reflecting the characteristics of the pixels P. The results are supplied to the timing controller 140. In particular, the data driver 110 senses the composite current of two or more pixels (P) of multiple scan lines that are driven simultaneously during each scan period, converts the sensed composite current into composite sensing data, and sends it to the timing controller 140. Print out.

The timing controller 140 controls the driving timing of the gate driver 120 and the data driver 100, compensates the image data to be supplied to each pixel using the compensation value of each pixel stored in the memory 50, and compensates the Data is supplied to the data driver 110. In particular, the timing controller 140 detects each pixel information through an operation process on the synthetic sensing data supplied from the data driver 110 during the sensing mode, extracts a compensation value from each pixel information, and compensates the memory 50. Update the value. The timing controller 140 includes the calculation unit 30, compensation extraction unit 40, and data processing unit 60 described above in FIG. 1.

Figure 6 shows the sensing data of each pixel for each channel of the OLED display device according to an embodiment of the present invention, compared with the prior art. In Figure 6, the X-axis represents the channel number and the Y-axis represents sensing data.

Referring to FIG. 6(a), it can be seen that, as in the related art, there is a large difference between channels in the sensing data sensed from each pixel, and this is due to the noise component included in the sensing data.

Referring to FIG. 6(b), 10 scan lines are simultaneously driven by the current sensing device according to an embodiment of the present invention to simultaneously sense the current of 10 pixels for each channel, and then the current of each pixel is calculated through a calculation process. This shows the results of detecting sensing data. It can be seen that the noise component has been reduced and the difference in sensing data between channels has been greatly reduced.

As described above, an embodiment of the present invention can accurately sense the low-current sensing value of each pixel by reducing the noise component through the simultaneous sensing and calculation process of a plurality of pixels, and obtain an accurate compensation value from the sensed value. Since can be detected, the compensation ability for the non-uniform characteristics of each pixel can be improved by using the compensation value.

In the above, specific embodiments have been shown and described to illustrate the technical idea of the present invention, but the present invention is not limited to the same configuration and operation as the specific embodiments as described above, and various modifications may be made without departing from the technical idea of the present invention. It can be implemented within the scope. Accordingly, such modifications should be considered to fall within the scope of the present invention, and the scope of the present invention should be determined by the claims described below.

10: data supply unit 20: sensing unit
30: calculation unit 40: compensation value extraction unit
50: Memory 100: Display panel
110: data driver 120: gate driver
130: panel driving unit 140: timing controller

Claims (7)

a display panel including a plurality of pixels;
A gate driver that simultaneously drives a plurality of scan lines during each scan period during the sensing mode,
a data supply unit that supplies data signals to pixels driven in each scan period;
By simultaneously sensing the pixels of the plurality of scan lines driven simultaneously in each scan period, a composite current for the plurality of pixels sharing the corresponding reference line for each sensing channel in the plurality of scan lines driven in each scan period is generated. It includes a sensing unit that senses through the reference line, converts it into synthetic sensing data, and outputs it,
A current sensing device for an OLED display device in which the sensing unit increases current size by simultaneously sensing pixels of the plurality of scan lines to improve sensing accuracy for low current sensed from each pixel. In claim 1,
an operation unit that calculates sensing data for each of the plurality of pixels through a predetermined operation using synthetic sensing data supplied from the sensing unit;
A current sensing device for an OLED display device further comprising a compensation value extraction unit that extracts the compensation value of each pixel using the sensing data of each pixel supplied from the calculation unit and updates the compensation value of each pixel stored in the memory. In claim 2,
Each of the n scan lines (n is a natural number of 2 or more) simultaneously driven in each scan period is simultaneously driven in combination with other scan lines in another scan period, and is driven n times during the sensing mode;
The sensing unit senses a composite current for n pixels sharing a corresponding reference line for each sensing channel during each scan period, and each of the n pixels is combined with other pixels sharing the reference line n times. being sensed,
A current sensing device of an OLED display device in which the calculation unit calculates the sensing data of each pixel through a predetermined arithmetic operation using a plurality (>n) of synthetic sensing data supplied from the sensing unit for each sensing channel. In claim 2,
The data supply unit and the sensing unit are built into a data driver,
The compensation value extractor is built into the timing controller,
The calculation unit is a current sensing device of an OLED display device built into the data driver or the timing controller. Simultaneously driving pixels of a plurality of scan lines in each scan period during the sensing mode and supplying data signals to the simultaneously driven pixels;
By simultaneously sensing the pixels of the plurality of scan lines driven simultaneously in each scan period, a composite current for the plurality of pixels sharing the corresponding reference line for each sensing channel in the plurality of scan lines driven in each scan period is generated. It includes the step of sensing through the corresponding reference line, converting it to synthetic sensing data, and outputting it,
The simultaneous sensing step is
A current sensing method for an OLED display device that increases the current size by simultaneously sensing pixels of the plurality of scan lines to improve sensing accuracy for low current sensed from each pixel. In claim 5,
calculating sensing data for each of the plurality of pixels through a predetermined operation using the synthesized sensing data;
A current sensing method for an OLED display device, further comprising extracting a compensation value for each pixel using the sensing data of each pixel and updating the compensation value for each pixel stored in a memory. In claim 6,
Each of the n scan lines (n is a natural number of 2 or more) simultaneously driven in each scan period is simultaneously driven in combination with other scan lines in another scan period, and is driven n times during the sensing mode;
During each scan period, a composite current for n pixels sharing a corresponding reference line is sensed for each sensing channel, and during the sensing mode, each of the n pixels is combined with another pixel sharing the reference line. Sensed n times,
A current sensing method for an OLED display device in which the sensing data of each pixel is calculated through a set arithmetic operation using a plurality (>n) of synthetic sensing data for each sensing channel.