KR101954779B1 - Organic light emitting diode display device and method of measuring capacity of pixel current measuring line of the same - Google Patents

Abstract

The present invention relates to an organic light emitting diode (OLED) display device and a method of measuring the capacitance of the pixel current measuring line. The OLED display device includes a display panel displaying an image using a video signal and a plurality of control signals, ; Switching means for controlling the pixel current to flow through the pixel current measuring line and the line capacitor; Voltage measuring means for measuring a line voltage charged in the line capacitor by a pixel current flowing in the pixel current measuring line; And a current measuring means for measuring a first or second current flowing into or out of the display panel, wherein the line capacity is calculated using the sum of the line voltage variations of the first or second current and the pixel current measurement line .

Description

TECHNICAL FIELD [0001] The present invention relates to an organic light emitting diode (OLED) display device and a method for measuring the capacitance of the pixel current measuring line. BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

The present invention relates to an organic light emitting diode (OLED) display device and a method of measuring the capacitance of the pixel current measuring line, and more particularly, to a method of measuring the capacitance of a pixel current measuring line using a first or second current flowing into or out of a display panel, And more particularly to an organic light emitting diode (OLED) display device and a method of measuring the capacitance of the pixel current measuring line.

2. Description of the Related Art [0002] With the development of information society in recent years, demands for the display field have been increasing in various forms. In response to this demand, various flat panel display devices having characteristics such as thinning, light weight and low power consumption have been developed, A liquid crystal display device, a plasma display panel device, and an organic light emitting diode display device have been studied.

An organic light emitting diode display device is a display device that emits light by using an organic compound that emits light such as red (R), green (G), and blue (B) light on a transparent substrate. A display panel, a drive circuit, and the like.

Unlike a liquid crystal display device, such an organic light emitting diode display device does not require a separate light source, which is advantageous in that the manufacturing process is simple and the manufacturing cost is reduced compared to a liquid crystal display device. It is in the limelight.

Particularly, in the active matrix type, the data voltage for controlling the current applied to the pixel is stored in the storage capacitor until the next frame signal is applied, It is possible to drive to maintain the light emitting state while a single screen is displayed.

In such an active matrix system, even if a low current is applied, the same luminance is exhibited, which has advantages of low power consumption and large size.

However, the organic light emitting diode display device may have uneven characteristics of transistors such as a threshold voltage (Vth) and a voltage-current (VI) characteristic of a driving transistor due to process variations and the like. Even if the same data voltage is applied, There is a problem that luminance unevenness occurs.

Accordingly, it has been proposed to provide a compensated data voltage to the display panel in order to reduce luminance unevenness due to a variation in the VI characteristic of the driving transistor.

FIG. 1 is a diagram for explaining a method of compensating an image signal in a conventional organic light emitting diode display. Referring to FIG.

In Fig. 1, A is a curve representing the average V-I characteristics of all the pixels, and B is a curve representing V-I characteristics of any pixels.

As shown in the figure, the value of the pixel current may be different from the driving voltage of the driving transistor even in the same display panel.

As a result, even if the same data voltage is applied, the amount of light emitted from the light emitting diodes varies, resulting in uneven brightness.

Hereinafter, a conventional video signal compensation method for solving such a problem will be described in order.

First, a part of pixels among a plurality of pixels of the display panel is selected, and a plurality of driving voltages are applied to the selected pixels to measure each pixel current.

Then, the obtained values are averaged to obtain an average V-I characteristic equation of all the pixels defined by Equation (1).

[Equation 1]

Here, Ids is the pixel current, Vgs is the input voltage of the driving transistor, and a and b are the first and second average coefficients that characterize the average V-I characteristic equation of all the pixels.

At this time, the V-I characteristic equation of an arbitrary pixel can be defined as shown in Equation (2).

A 'and b' can be calculated by defining each pixel current according to two or more driving voltages and substituting the calculated pixel current into Equation (2).

&Quot; (2) "

Where a 'and b' are the first and second pixel coefficients that characterize the V-I characteristic equation of any pixel.

The first and second total coefficients and the first and second pixel coefficients serve as first to fourth pixel characteristic coefficients used for compensating the data voltage.

As described above, the offset and gain necessary for the video signal compensation are corrected using the first through fourth pixel characteristic coefficients a, b, a 'and b'.

For example, the reference offset and gain may be stored in advance in the offset / gain memory section, and if the offset and gain are corrected using the first through fourth pixel characteristic coefficients a, b, a ', b' , And then updates the offset and gain in the offset / gain memory unit to the corrected value.

Then, the corrected offset and gain are stored in the offset / gain storage section, and the image signal is corrected by applying offset and gain, and transmitted to the display panel, thereby improving the luminance unevenness.

However, in the conventional image signal compensation method, since the pixel current is measured for each pixel in measuring the pixel current for correcting the image signal, there is a problem that it takes much time to measure the pixel current.

The present invention has been made to solve the above problems, and it is an object of the present invention to provide an organic light emitting diode display device capable of improving luminance unevenness by compensating for a video signal using a pixel current measured at high speed in units of pixel current measurement lines, And a method for measuring capacitance of a current measuring line.

An organic light emitting diode display device for calculating a line capacitance or a pixel current by using the sum of the first or second current flowing into or out of the display panel and the line voltage variation amount of the pixel current measurement line, And a method for measuring the capacity.

According to an aspect of the present invention, there is provided an organic light emitting diode (OLED) display device including: a display panel that displays an image using a video signal and a plurality of control signals and includes a plurality of pixel current measurement lines; Switching means for controlling the pixel current to flow through the pixel current measuring line and the line capacitor; Voltage measuring means for measuring a line voltage charged in the line capacitor by a pixel current flowing in the pixel current measuring line; And a current measuring means for measuring a first or second current flowing into or out of the display panel, wherein the line capacity is calculated using the sum of the line voltage variations of the first or second current and the pixel current measurement line .

에 의해 정의되며, Ivdd는 상기 제 1 전류이고, t1과 t2은 상기 제 1 및 제 2 시점이고, Vkn1, Vkn2는 각각 상기 제 1 및 제 2 시점에서의 화소 전류 측정라인의 라인 전압이고, M 및 n은 각각 화소 전류 측정시에 동시에 점등하는 수직 화소수 및 측정하는 수직 라인을 나타내는 번호일 수 있다.Here, the line capacitance (C _{line - n} )

, Ivdd is the first current, t1 and t2 are the first and second time points, Vkn1 and Vkn2 are the line voltage of the pixel current measurement line at the first and second time points, respectively, and M And n may be a number indicating the number of vertical pixels simultaneously lit at the time of measuring the pixel current and a number indicating a vertical line to be measured.

The compensation coefficient calculator may further include a compensation coefficient calculator for calculating the offset voltage and the gain of the line voltage based on the line voltage of the pixel current measuring line, A line voltage measuring unit for calculating a line voltage; A line capacitance unit for calculating the line capacitance using the first or second current and the voltage variation; And an offset and gain section for calculating the pixel current using the line capacitance and the line voltage variation and for calculating the offset and gain by the pixel characteristic coefficient calculated using the pixel current.

According to another aspect of the present invention, there is provided an organic light emitting diode (OLED) display device including: a display panel having a plurality of pixel current measurement lines for displaying an image using an image signal and a plurality of control signals; Switching means for controlling the pixel current to flow through the pixel current measuring line and the line capacitor; Voltage measuring means for measuring a line voltage charged in the line capacitor by a pixel current flowing in the pixel current measuring line; And a current measuring means for measuring a first or second current flowing into or out of the display panel, wherein the pixel current is calculated using the sum of the line voltage variations of the first or second current and the pixel current measurement line .

에 의해 정의되며, Ivdd는 상기 제 1 전류이고, t1과 t2은 상기 제 1 및 제 2 시점이고, Vkn1, Vkn2는 각각 상기 제 1 및 제 2 시점에서의 화소 전류 측정라인의 라인 전압이고, M 및 n은 각각 화소 전류 측정시에 동시에 점등하는 수직 화소수 및 측정하는 수직 라인을 나타내는 번호일 수 있다.Here, the pixel current (imn)

, Ivdd is the first current, t1 and t2 are the first and second time points, Vkn1 and Vkn2 are the line voltage of the pixel current measurement line at the first and second time points, respectively, and M And n may be a number indicating the number of vertical pixels simultaneously lit at the time of measuring the pixel current and a number indicating a vertical line to be measured.

The compensation coefficient calculator may further include a compensating coefficient calculator that calculates a compensation voltage of the line voltage by receiving the line voltage from the pixel current measuring line, A line voltage measuring unit for calculating a line voltage; And an offset and a gain unit for calculating a pixel current by using the first or second current and the line voltage variation and calculating an offset and a gain by the pixel characteristic coefficient calculated using the pixel current.

The pixel current measuring line may be a reference voltage line or a data line.

According to another aspect of the present invention, there is provided a method of measuring the capacitance of a pixel current measuring line of an organic light emitting diode (OLED) display device, comprising: Applying a voltage and measuring a first or second current flowing through the first and second power supply lines of the display panel; Measuring a line voltage of the pixel current measuring line at the first and second time points and calculating a line voltage variation using the measured line voltage; And calculating the line capacitance by receiving the first or second current and the line voltage variation amount.

에 의해 정의되며, Ivdd는 상기 제 1 전류이고, t1과 t2은 상기 제 1 및 제 2 시점이고, Vkn1, Vkn2는 각각 상기 제 1 및 제 2 시점에서의 화소 전류 측정라인의 라인 전압이고, M 및 n은 각각 화소 전류 측정시에 동시에 점등하는 수직 화소수 및 측정하는 수직 라인을 나타내는 번호일 수 있다.Here, the line capacitance (C _{line - n} )

, Ivdd is the first current, t1 and t2 are the first and second time points, Vkn1 and Vkn2 are the line voltage of the pixel current measurement line at the first and second time points, respectively, and M And n may be a number indicating the number of vertical pixels simultaneously lit at the time of measuring the pixel current and a number indicating a vertical line to be measured.

A method of measuring a capacitance of a pixel current measuring line of an organic light emitting diode display according to an embodiment of the present invention includes: calculating a pixel current by receiving the first or second current and the line capacitance; Calculating first and second pixel characteristic coefficients using the pixel current; And calculating and storing an offset and a gain using the first and second pixel characteristic coefficients.

According to another aspect of the present invention, there is provided a method for measuring a capacitance of a pixel current measuring line of an organic light emitting diode (OLED) display device, comprising: Applying a second voltage and measuring a first or second current flowing through the first and second power supply lines of the display panel; Measuring a line voltage of the pixel current measuring line at the first and second time points and calculating a line voltage variation using the measured line voltage; And calculating the pixel current by receiving the first or second current and the line voltage variation amount.

에 의해 정의되며, Ivdd는 상기 제 1 전류이고, t1과 t2은 상기 제 1 및 제 2 시점이고, Vkn1, Vkn2는 각각 상기 제 1 및 제 2 시점에서의 화소 전류 측정라인의 라인 전압이고, M 및 n은 각각 화소 전류 측정시에 동시에 점등하는 수직 화소수 및 측정하는 수직 라인을 나타내는 번호일 수 있다.Here, the pixel current (imn)

, Ivdd is the first current, t1 and t2 are the first and second time points, Vkn1 and Vkn2 are the line voltage of the pixel current measurement line at the first and second time points, respectively, and M And n may be a number indicating the number of vertical pixels simultaneously lit at the time of measuring the pixel current and a number indicating a vertical line to be measured.

A method of measuring a capacitance of a pixel current measuring line of an organic light emitting diode display according to an embodiment of the present invention includes: calculating first and second pixel characteristic coefficients using the pixel current; And calculating and storing an offset and a gain using the first and second pixel characteristic coefficients.

The pixel current measuring line may be a reference voltage line or a data line.

As described above, in the organic light emitting diode display device and the capacitance measurement method of the pixel current measurement line according to the present invention, the first or second current flowing into or out of the display panel and the line current variation amount of the pixel current measurement line The sum of the line capacitances or the pixel currents can be calculated.

Further, by measuring the line capacitance in the pixel current measurement line, calculating the pixel characteristic coefficient using the measured line capacitance, compensating the video signal by providing the offset and gain value corrected by the calculated pixel characteristic coefficient The error due to the line capacitance can be corrected to further improve the luminance unevenness.

FIG. 1 is a diagram for explaining a method of compensating an image signal in a conventional organic light emitting diode display. Referring to FIG.
2 is a schematic view illustrating an organic light emitting diode display device according to an embodiment of the present invention.
3 is a schematic diagram illustrating a source driver according to an embodiment of the present invention.
4 is a view schematically showing a compensation operation unit according to an embodiment of the present invention.
FIG. 5 is a diagram illustrating an operation of the organic light emitting diode display according to the embodiment of the present invention in a display mode. Referring to FIG.
6A to 6C are views for explaining the operation in the measurement mode of the organic light emitting diode display according to the embodiment of the present invention.
7A to 7C are views for explaining the operation in the measurement mode of the organic light emitting diode display according to another embodiment of the present invention.
8 is a view schematically showing a compensation coefficient calculation unit according to an embodiment of the present invention.
9 is a diagram for explaining a method of measuring a capacitance of a pixel current measuring line in an organic light emitting diode display device according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 2 is a view schematically showing an organic light emitting diode display device according to an embodiment of the present invention. FIG. 3 is a view schematically showing a source driver according to an embodiment of the present invention. 1 is a view schematically showing a compensation operation unit according to an example.

2, the organic light emitting diode display 100 according to the present invention includes a display panel 110 for displaying an image, a source driver 120, a gate driver 130, A compensation calculation unit 140, a compensation coefficient calculation unit 150, and the like.

The organic light emitting diode display 100 according to the present invention may operate in a display mode for displaying an image and a measurement mode for measuring a pixel current.

The display panel 110 may include a plurality of gate wirings SL and a plurality of data wirings DL that intersect each other to define a plurality of pixels P,

In each pixel P, first and second transistors, a driving transistor, a storage capacitor, a light emitting diode, and the like may be formed.

Here, the driving transistor controls the amount of current flowing through the light emitting diode, and the amount of current flowing through the light emitting diode is proportional to the magnitude of the data voltage transmitted to the driving transistor.

That is, the organic light emitting diode display device can display an image by applying different data voltages for each pixel P to display different gradations.

The storage capacitor holds the data voltage for one frame to keep the amount of current flowing through the LED constant and to maintain the gray level displayed by the LED constant.

The source driver 120 generates a data voltage using a video signal received from the timing controller and a plurality of data control signals, and supplies the generated data voltage to the display panel 110 through the data line DL.

The gate driver 130 may be formed by a GIP (Gate In Panel) method or the like. The gate driver 130 generates a gate voltage using a control signal transmitted from the timing controller, (Not shown).

The timing controller can receive a plurality of video signals and a plurality of control signals such as a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, and a data enable signal DE from a system such as a graphic card through an interface.

The compensation coefficient calculation unit 150 calculates the first to fourth pixel characteristic coefficients (a, b, a ', b' in FIG. 1) by measuring the pixel current in the display panel, Gain memory unit 146 of the compensation operation unit 140 after calculating the correction offset and the correction gain using the first to fourth pixel coefficient values.

The compensation coefficient calculation unit 150 may be configured as an external device of the organic light emitting diode display device 100.

3, the source driver 120 according to the present invention includes a first shift register 122 for receiving a video signal RGB, a second shift register 122 for selecting a sampling / holding circuit (S / H) A digital / analog conversion circuit DAC connected in parallel to each of the plurality of output channels CH1 to CHn, a plurality of sampling / holding circuits S / H, a sampling / holding circuit Connected between the sampling / holding circuit (S / H) and the plurality of output channels (CH1 to CHn), a first switch SW1 connected between the output terminals 2 switch SW2, a capacitor C connected in parallel to the input terminal of the sampling / holding circuit S / H, and a capacitor C connected between the sampling / holding circuit S / H and the analog / A sampling switch SS, and the like.

The first shift register 122 sequentially shifts the image signals in the display mode and the measurement mode in response to a shift clock, and then transfers the image signals to a digital / analog conversion circuit (DAC).

The digital-to-analog conversion circuit DAC converts the video signal into a data voltage in the display mode and the measurement mode, and transmits the data voltage to the first switch SW1 and the output channels CH1 to CHn.

The sampling / holding circuit S / H can sample or hold the voltage corresponding to the pixel current supplied through the output channels CH1 to CHn in the measurement mode.

The second shift register 124 sequentially shifts the sampling signal to the sampling switch SS while shifting in response to the ADC clock (ADC clock) in the measurement mode.

Here, the sampling signal is a signal for turning on the sampling switch SS. In the present invention, the sampling switch SS is turned on to control the line voltage in the pixel current measuring line (reference voltage wiring or data wiring) can do.

The sampling switch SS is sequentially turned on for each vertical line in response to the sampling signal from the second shift register 124 so that the voltage at the sampling / holding circuit S / ) In a sequential manner.

The analog / digital conversion circuit ADC converts the analog voltage in the sampling / holding circuit S / H, which is sequentially inputted through the sampling switch SS, into a digital voltage, and outputs the changed digital voltage to the compensation coefficient calculator 150. [ .

4, the compensation operation unit 140 includes a gamma correction unit 141a, a multiplier 141b, an adder 141c, an offset processor 142, a gain processor 144, an offset / gain memory Section 146 and the like.

The gamma correction unit 141a may output the corrected video signal by performing gamma correction on the video signal received from the system.

The multiplier 141b multiplies the gamma corrected video signal output from the gamma correction unit 141a by an offset corresponding to the horizontal line, which is the output of the offset processing unit 142. [

At this time, the offset processing unit 142 may use a dot clock signal to determine to which pixel of the display panel 110 the gamma corrected image signal corresponds, and output an offset corresponding thereto.

The adder 141c adds the multiplied image signal, which is the output of the multiplier 141b, and the gain corresponding to the horizontal line, which is the output of the gain processor 144. [

At this time, the gain processing unit 144 can determine which pixel of the display panel 110 the multiplied image signal corresponds to using the dot clock signal, and output a gain corresponding thereto.

The offset / gain memory unit 146 may store the reference offset and the reference gain for the average driving transistor in the display panel 110 in advance, and if the offset and the gain are corrected using the pixel characteristic coefficient, As shown in Fig.

Hereinafter, the operation of the pixel of the organic light emitting diode display device will be described.

FIG. 5 is a diagram illustrating an operation of the organic light emitting diode display according to the embodiment of the present invention in a display mode. Referring to FIG.

5, a plurality of transistors Tr1, Tr2, and Tr3, a storage capacitor Cst, and a light emitting diode OLED may be formed in a pixel of the display panel 110. Referring to FIG.

The source electrode and the gate electrode of the first transistor Tr1 are connected to the data line DL and the first gate line SL1 respectively and the drain electrode of the first transistor Tr1 is connected to the gate electrode of the driving transistor Tr3 And is connected to the connected first node N1.

The first transistor Tr1 is turned on according to the gate voltage supplied through the first gate line SL1 to supply the data voltage from the data line DL to the first node N1 do.

The source electrode and the gate electrode of the second transistor Tr2 are connected to the reference voltage line RL and the second gate line SL2 respectively and the drain electrode of the first transistor Tr1 is connected to the drain electrode of the driving transistor Tr3. And a second node N2 connected to the second node N2.

The first electrode and the second electrode are a source electrode and a drain electrode according to a current direction.

The second transistor Tr2 is turned on in accordance with the gate voltage supplied through the second gate line SL2 in the display mode to generate the reference voltage Vref from the reference voltage line RL And supplies it to the second node N2.

On the other hand, the second transistor Tr2 is turned on in accordance with the gate voltage supplied through the second gate line SL2 in the measurement mode, so that the pixel current flowing through the driving transistor Tr3 is supplied to the reference voltage line (RL).

The storage capacitor Cst stores the voltage difference between the data voltage and the reference voltage Vref supplied to the first and second nodes N1 and N2, respectively.

As a result, the storage capacitor Cst maintains the data voltage for one frame so as to keep the amount of current flowing through the light emitting diode OLED constant and to keep the gray level displayed by the light emitting diode OLED constant.

The source electrode and the gate electrode of the driving transistor T3 are respectively connected to the high potential voltage Vdd terminal and the first node N1 and the drain electrode of the driving transistor T3 is connected to the second node N2.

The driving transistor T3 controls the amount of current flowing through the light emitting diode OLED and the amount of current flowing through the light emitting diode OLED is proportional to the magnitude of the data voltage applied to the gate electrode of the driving transistor T3.

That is, the organic light emitting diode display device can display an image by displaying different gradations by applying data voltages of various sizes to each pixel.

The light emitting diode OLED is connected in series with the driving transistor Tr3 between the first power supply line PL1 and the second power supply line PL2.

The display panel 110 according to the present invention includes a third switch SW3 connected between the output channel CH and the data line DL and a third switch SW2 connected between the output channel CH and the reference voltage line RL And a fifth switch SW5 connected between the reference voltage source Vref and the reference voltage line RL.

The organic light emitting diode display may further include a sixth switch SW6 for supplying a high potential voltage Vdd or a low potential voltage Vss through the second power supply line PL2.

For example, the sixth switch SW6 may be located in the power supply unit or may be located between the power supply unit and the display panel 110. [

Hereinafter, a process of operating the organic light emitting diode display device in the display mode will be described. In the display mode, the sixth switch SW6 is connected to the low potential voltage (Vss) terminal.

A first switch SW1 and a third switch SW3 connected in series between a digital-to-analog conversion circuit (DAC) and a data line DL when the organic light emitting diode display device operates in the display mode, The fifth switch SW5 connected between the Vref terminal and the reference voltage wiring RL is turned on.

At this time, the video signal is converted into a data voltage in the digital / analog conversion circuit (DAC), and the converted data voltage is supplied to the data line DL through the first and third switches SW1 and SW3.

Then, the reference voltage Vref is transferred to the reference voltage line RL through the fifth switch SW5.

At this time, the first and second transistors Tr1 and Tr2 of the pixel may be simultaneously turned on to transfer the data voltage and the reference voltage Vref to the first node N1 and the second node N2, (Cst) charges the voltage difference.

When the first and second transistors Tr1 and Tr2 are turned off, the storage capacitor Cst supplies the charging voltage to the driving voltage of the driving transistor Tr3.

Thus, the light emitting diode OLED emits light proportional to the current corresponding to the driving voltage Vgs of the driving transistor Tr3.

On the other hand, a second switch SW2 connected between the sampling / holding circuit S / H and the output channel CH when the organic light emitting diode display device operates in the display mode, And the fourth switch SW4 connected between the first and second switches RL and RL is turned off.

6A to 6C are views for explaining the operation in the measurement mode of the organic light emitting diode display according to the embodiment of the present invention. At this time, the sixth switch SW6 is connected to the high-potential voltage (Vdd) terminal.

The first switch control signal S1, the third switch control signal S3 and the fifth switch control signal S5 of the high level are applied during the first time period A as shown in Fig. 6A, The second switch control signal S2 and the fourth switch control signal S4 may be applied.

The first switch SW1, the third switch SW3 and the fifth switch SW5 are turned on by the first to fifth switch control signals S1 to S5 as shown in Fig. 6B, 2 switch SW2 and the fourth switch SW4 are turned off.

Referring again to FIG. 6A, first and second gate voltages of a high level are applied during the first time (A), whereby the voltage difference between the data voltage and the reference voltage is stored in the storage capacitor Cst.

That is, during the first time (A), the respective voltages supplied through the reference voltage line RL and the data line DL are stored in the storage capacitor Cst, and as a result, the voltage V _N3 at the reference voltage line V0. (Vref = V0)

Meanwhile, in the measurement mode, the high voltage Vdd is transmitted through the sixth switch SW6 to one electrode of the light emitting diode OLED, and the light emitting diode OLED does not emit light.

The second switch control signal S2 and the fourth switch control signal S4 of the high level are applied during the second time period B and the first switch control signal S1 and the third switch control signal S3 may be applied.

The second switch SW2 and the fourth switch SW4 are turned on by the second to fourth switch control signals S2 to S4 and the first switch SW1 and the third switch SW3 are turned- Off.

Since the fifth switch control signal S5 maintains the high level, the fifth switch SW5 maintains the ON state.

Therefore, the reference voltage Vref is supplied via the reference voltage line RL during the second time period B, and V _{N3, which} is the voltage at the reference voltage line, is maintained at V0.

During the third time C, the first to fourth switch control signals S1 to S4 maintain the same level as B, and only the fifth switch control signal S5 can be changed to the low level and applied.

Thus, as shown in Fig. 6C, the first and fourth switches SW1 to SW4 maintain the same state as before, and the fifth switch SW5 is turned off.

Referring to FIG. 6A again, a first gate voltage of a low level and a high gate voltage of a high level are applied during the third time C, and the driving transistor Tr3 is turned on by the driving voltage stored in the storage capacitor Cst State can be maintained.

Then, while the driving transistor Tr3 is turned on, the pixel current flows to the reference voltage line RL through the second transistor Tr2.

At this time, the pixel current flowing through the reference voltage line RL charges the line capacitor C _line and the capacitor C, and as a result, the voltage of the reference voltage line RL rises.

That is, as shown in FIG. 6A, the voltage V _N3 at the reference voltage wiring line RL increases from the time when the fifth switch SW5 is turned off.

At this time, since the voltage of the reference voltage line RL rises in proportion to the pixel current, if the voltage of the reference voltage line RL is measured at a specific point in time, the pixel current flowing in the driving transistor Tr3 is calculated .

&Quot; (3) "

Here, Ids is the pixel current, V1 and V2 are the voltages in the reference voltage wiring at t1 and t2, C _line is the capacitance of the line capacitor, which is a parasitic capacitor connected in parallel with the reference voltage wiring, and C is the sampling / The capacitance of the capacitor connected in parallel to the input of the circuit. At this time, in order to obtain Ids by Equation (3), it is necessary to know C _line , which can be obtained by experiment.

In this measurement mode, each of the pixel currents is measured using a plurality of driving voltages, and the offset for threshold voltage compensation and the gain for mobility compensation can be calculated on a pixel-by-pixel basis using the measured pixel current.

The corrected offset and gain can be stored in the offset / gain storage unit in the organic light emitting diode display device, and the image signal can be corrected by applying offset and gain, and transmitted to the display panel to improve the luminance unevenness.

7A to 7C are views for explaining the operation in the measurement mode of the organic light emitting diode display according to another embodiment of the present invention.

5, the third to fifth switches SW3, SW4, and SW5 are omitted, and the first transistor Tr1 in the pixel circuit is connected to the reference The configuration is the same except that the voltage Vref is supplied to the first node N1 and the second transistor Tr2 supplies the data voltage to the second node N2.

As shown in Fig. 7A, during the first time A, the first and second switch control signals S1 and S2 of high level can be applied.

The first and second switches SW1 and SW2 are turned on by the first and second switch control signals S1 and S2 as shown in Fig. 7B.

Referring again to FIG. 7A, first and second gate voltages of a high level are applied during the first time (A), whereby the voltage difference between the reference voltage and the data voltage is stored in the storage capacitor Cst.

That is, during the first time period A, the voltages supplied through the reference voltage Vref terminal and the data line DL are stored in the storage capacitor Cst.

Meanwhile, in the measurement mode, the high voltage Vdd is transmitted through the sixth switch SW6 to one electrode of the light emitting diode OLED, and the light emitting diode OLED does not emit light.

During the second time B, the first transistor Tr1 is turned off as the first gate voltage of the low level is applied.

Therefore, during the second time period B, the reference voltage is not supplied through the first transistor Tr1, and the voltage V _N4 at the data line becomes V 0.

As shown in FIG. 7C, the first switch SW1 is turned off as the first switch control signal S1 of low level is applied.

Referring again to FIG. 7A, a high-level two-gate voltage is applied during the third time C, but the data voltage is no longer supplied because the first switch SW1 is turned off.

Accordingly, the driving transistor Tr3 maintains the on state by the driving voltage stored in the storage capacitor Cst and the pixel current is supplied to the data line DL through the second transistor Tr2 while the driving transistor Tr3 is turned on. ).

At this time, the pixel current flowing through the data line DL charges the line capacitor C _line and the capacitor C, and as a result, the voltage of the data line DL rises.

That is, as shown in FIG. 7A, the voltage V _N4 in the data line increases from the time when the first switch SW1 is turned off.

At this time, since the voltage of the data line DL rises in proportion to the pixel current, if the voltage of the data line DL is measured at a specific point in time, the pixel current flowing in the driving transistor Tr3 can be calculated using Equation (3) .

As described above, in the organic light emitting diode display device and the capacitance measurement method of the pixel current measurement line according to the present invention, in measuring the pixel current through the pixel current measurement line (reference voltage line, data line) The pixel current can be measured at a high speed using the voltage charged in the parasitic capacitor or the like.

In addition, offset and gain values corrected by the measured pixel current are provided to compensate for the image signal, thereby improving luminance unevenness.

However, in FIGS. 6A to 7C, there may be an error between the C _line calculated by the calculation method and the C _line of the actual display panel, and the luminance of the image may not be compensated due to the error. .

For example, if the capacitance of the line capacitor in the actual display panel is? Times the capacitance of the line capacitor by calculation, Ids' in Equation (3) becomes? * Ids.

When the first and second pixel coefficients are calculated using Ids' (? * Ids) as described above, they become a and b, respectively.

At this time, b becomes b ', which is the same regardless of the change of the capacitance of the line capacitor, but a becomes a * a' and becomes a times of a 'by the capacity of the line capacitor.

Hereinafter, a method for resolving the error between the C _line by the calculation and the C _line in the actual display panel will be described.

8 is a view schematically showing a compensation coefficient calculation unit according to an embodiment of the present invention. The compensation coefficient calculator may be configured as an external device of the organic light emitting diode display.

8, the compensation coefficient calculation unit 150 according to the present invention may include a line voltage measurement unit 252, a line capacitance unit 254, an offset / gain unit 256, and the like.

The line voltage measuring unit 252 receives the voltage in the pixel current measuring line and calculates the line voltage variation.

For example, assuming that the voltages at the pixel current measurement lines at t1 and t2 are V1 and V2, the line voltage variation amount is (V2-V1) / (t2-t1).

That is, the line voltage measuring unit 252 can calculate the line voltage change amount of each pixel current measuring line and transmit it to the line capacitance unit 254 and the offset / gain unit 256, respectively.

At this time, the pixel current measurement line may be a reference voltage wiring or a data wiring.

The line capacitance unit 254 includes a line capacitance calculation unit 254a and a current measurement unit 254b and calculates a line capacitance using the measured first or second current and supplies the calculated line capacitance to an offset / And transmits it to the inserting unit 256.

The line capacitance calculation unit 254a can calculate the line capacitance using the first or second current received from the current measurement unit 254b.

&Quot; (4) "

&Quot; (5) "

&Quot; (6) "

In this case, imn is the pixel current at the pixel located at the (m, n) position of the display panel, Cline_n is the sum of the capacitor capacitances present in the pixel current measurement line connected to the output channel CHn, and Vmn1 and Vmn2 Is the voltage of the pixel current measurement line at times t1 and t2 when measuring the pixel current, respectively.

In and M and N are numbers indicative of the number of vertical pixels simultaneously lit and the vertical line to be measured at the time of measuring the pixel current, respectively, and the first current (Ivdd Is a current flowing into the first power supply wiring, and the second current Ivss is a current flowing out to the second power supply wiring.

Since In is the same as the first or second current Ivdd or Ivss, the current measuring unit 254b measures the first or second current Ivdd or Ivss and outputs the first or second current Ivdd or Ivss from the line voltage measuring unit 252 to the line / Cline_n, which is the sum of the capacitor capacitances existing in the pixel current measurement line connected to the output channel CHn according to Equation (7) using the sum of the voltage change amount '(V2-V1) / (t2-t1) Can be obtained.

&Quot; (7) "

In this case, Cline_n is obtained using all the pixels of the pixel current measurement line, but it is not limited to this, but it is also possible to use only some pixels.

That is, when Cline_n is obtained by using all the pixels of the pixel current measuring line, since the measured current value is large, it is advantageous in terms of the S / N ratio, but only some of the pixel current measuring lines can be used.

The offset / gain unit 256 includes an Ids calculation unit 256a, a pixel characteristic coefficient calculation unit 256b, an offset / gain calculation unit 256c, and the like.

The Ids calculating unit 256a can calculate the pixel current using the line capacitance Cline_n received from the line capacitor 254 and the line voltage variation received from the line voltage measuring unit 252. [

It is also possible to calculate the pixel current imn without calculating Cline_n by using the line voltage change amount and Ivdd received from the line voltage measuring unit 252 according to Equation (8).

&Quot; (8) "

The pixel characteristic coefficient calculator 256b can calculate the pixel characteristic coefficients b 'and a' using Equations (9) and (10).

&Quot; (9) "

&Quot; (10) "

Here, V1 and V2 are the voltage of the pixel current measurement line at times t1 and t2, respectively, and Ids1 and Ids2 are pixel currents obtained by substituting V1 and V2 in the equation (2), respectively.

The offset / gain calculator 256c may calculate the offset and gain using Equations (11) and (12), and may transmit the calculated offset and gain to the offset / gain memory portion (146 in FIG. 4).

&Quot; (11) "

&Quot; (12) "

9 is a diagram for explaining a method of measuring a capacitance of a pixel current measuring line in an organic light emitting diode display device according to an embodiment of the present invention.

9, after an arbitrary pixel current measurement line is selected and the first and second voltages Vdd and Vss are applied, the first and second power supply lines, which flow through the first and second power supply lines of the display panel, The currents Ivdd and Ivss are measured (S100).

Then, the line voltage of the pixel current measuring line is measured at a specific time point (first and second time points), and the line voltage variation amount '(V2-V1) / (t2-t1)' is calculated using the measured line voltage (S110).

At this time, the sum of the line voltage variations in all the pixel current measurement lines can be transmitted to the offset / gain portion (256 in FIG. 8).

The first and second currents Ivdd and Ivss and the line voltage variation are received and the line capacitance is calculated according to Equation 7 at S120 and the first and second currents Ivdd and Ivss and the line capacitance are received, Ids is calculated using Equation 8 (S130).

Then, the pixel characteristic coefficients a 'and b' are calculated using Equations (9) and (10) using the calculated Ids (S140).

The offset and gain are calculated by Equations 11 and 12 using the pixel characteristic coefficients a 'and b' calculated next, and the calculated offset and gain are stored in the offset / gain memory portion 146 (FIG. 4) Lt; / RTI >

Therefore, in the organic light emitting diode display device and the capacitance measuring method of the pixel current measuring line according to the present invention, the total sum of the first or second current flowing into or out of the display panel and the line voltage variation amount of the pixel current measuring line is used So that the line capacitance or the pixel current can be calculated.

Further, since the compensated video signal is provided to the data driver of the display panel by compensating the video signal by providing an offset and a gain value calculated using the line capacitance or the pixel current, the error due to the line capacitance is corrected, Can be improved.

The embodiments of the present invention as described above are merely illustrative, and those skilled in the art can make modifications without departing from the gist of the present invention. Accordingly, the protection scope of the present invention includes modifications of the present invention within the scope of the appended claims and equivalents thereof.

100: organic light emitting diode display device 110: display panel
120: source driver 130: gate driver
140: compensation calculation unit 150: compensation coefficient calculation unit

Claims (14)

A display panel displaying an image using a video signal and a plurality of control signals, the display panel having a plurality of pixel current measurement lines;
Switching means for controlling the pixel current to flow through the pixel current measuring line and the line capacitor;
Voltage measuring means for measuring a line voltage charged in the line capacitor by a pixel current flowing in the pixel current measuring line;
And current measuring means for measuring a first or second current flowing into or out of the display panel,
Calculating a line capacitance using the sum of the first or second current and the line voltage variation amount of the pixel current measurement line,
The line capacitance (C line - _n )

Lt; / RTI >
Ivdd is the first current, t1 and t2 are the first and second time points, Vkn1 and Vkn2 are the line voltage of the pixel current measurement line at the first and second time points, respectively, and M and n are the pixel current Wherein the number of vertical pixels that are simultaneously lit at the time of measurement and the number of vertical lines to be measured are displayed.
delete The method according to claim 1,
And a compensating coefficient calculating unit for calculating and transmitting an offset and a gain for correcting the video signal using the line capacitance,
Wherein the compensation-
A line voltage measuring unit for receiving a line voltage in the pixel current measuring line and calculating a voltage change amount of the line voltage;
A line capacitance unit for calculating the line capacitance using the first or second current and the voltage variation;
An offset calculating circuit for calculating a pixel current by using the line capacitance and the line voltage variation and calculating an offset and a gain based on the pixel characteristic coefficient calculated using the pixel current,
And an organic light emitting diode (OLED) display device.
A display panel displaying an image using a video signal and a plurality of control signals, the display panel having a plurality of pixel current measurement lines;
Switching means for controlling the pixel current to flow through the pixel current measuring line and the line capacitor;
Voltage measuring means for measuring a line voltage charged in the line capacitor by a pixel current flowing in the pixel current measuring line;
And current measuring means for measuring a first or second current flowing into or out of the display panel,
Calculating a pixel current using the sum of the first or second current and the line voltage variation amount of the pixel current measurement line,
The pixel current (imn)

Lt; / RTI >
Ivdd is the first current, t1 and t2 are the first and second time points for measuring the line voltage, respectively, Vkn1 and Vkn2 are the line voltage of the pixel current measuring line at the first and second time points, And M and n are numbers indicating the number of vertical pixels simultaneously lit and the vertical line to be measured at the time of measuring the pixel current, respectively.
delete 5. The method of claim 4,
Further comprising a compensation coefficient calculation unit for calculating and transmitting an offset and a gain for correcting the video signal using the pixel current,
Wherein the compensation-
A line voltage measuring unit for receiving a line voltage in the pixel current measuring line and calculating a voltage change amount of the line voltage;
An offset calculating circuit for calculating a pixel current by using the first or second current and the line voltage variation and calculating an offset and a gain based on the pixel characteristic coefficient calculated using the pixel current,
And an organic light emitting diode (OLED) display device.
The method according to claim 1 or 4,
Wherein the pixel current measuring line is a reference voltage line or a data line.
Selecting any pixel current measurement line on the display panel to apply the first and second voltages and measuring a first or second current flowing through the first and second power supply lines of the display panel;
Measuring a line voltage of the pixel current measuring line at the first and second time points and calculating a line voltage variation using the measured line voltage;
Calculating the line capacitance by receiving the first or second current and the line voltage variation amount
Lt; / RTI >
The line capacitance (C line - _n )

Lt; / RTI >
Ivdd is the first current, t1 and t2 are the first and second time points, Vkn1 and Vkn2 are the line voltage of the pixel current measurement line at the first and second time points, Wherein the number of vertical pixels that are simultaneously lit at the time of current measurement and the number of the vertical line to be measured are measured.
delete 9. The method of claim 8,
Calculating a pixel current by receiving the first or second current and the line capacitance;
Calculating first and second pixel characteristic coefficients using the pixel current;
Calculating and storing an offset and a gain using the first and second pixel characteristic coefficients;
The method of claim 1, further comprising the step of measuring the capacitance of the pixel current measuring line of the organic light emitting diode display device.
Selecting any pixel current measurement line on the display panel to apply the first and second voltages and measuring a first or second current flowing through the first and second power supply lines of the display panel;
Measuring a line voltage of the pixel current measuring line at the first and second time points and calculating a line voltage variation using the measured line voltage;
Calculating the pixel current by receiving the first or second current and the line voltage variation amount
Lt; / RTI >
The pixel current (imn)

Lt; / RTI >
Ivdd is the first current, t1 and t2 are the first and second time points, Vkn1 and Vkn2 are the line voltage of the pixel current measurement line at the first and second time points, Wherein the number of vertical pixels that are simultaneously lit at the time of current measurement and the number of the vertical line to be measured are measured.
delete 12. The method of claim 11,
Calculating first and second pixel characteristic coefficients using the pixel current;
Calculating and storing an offset and a gain using the first and second pixel characteristic coefficients;
The method of claim 1, further comprising the step of measuring the capacitance of the pixel current measuring line of the organic light emitting diode display device.
The method according to claim 8 or 11,
Wherein the pixel current measuring line is a reference voltage line or a data line. A method of measuring capacitance of a pixel current measuring line of an organic light emitting diode display device,

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