KR101939231B1 - Organic light emitting diode display device and method of measuring pixel current of the same - Google Patents

Abstract

The present invention relates to an organic light emitting diode (OLED) display device and a method for measuring the pixel current thereof, and a display panel including a plurality of pixel current measurement lines, A data voltage for measurement is applied to a pixel to be measured connected to a first pixel current measurement line in measurement, a black data voltage is applied to a remaining pixel connected to the first pixel current measurement line, The first current flowing through the first pixel current measuring line and the second current flowing through the second pixel current measuring line are measured, and the first current and the second current are measured by applying a black data voltage to all connected pixels, And the pixel current in the pixel to be measured in which the noise is removed is measured.

Description

TECHNICAL FIELD [0001] The present invention relates to an organic light emitting diode (OLED) display, and a method of measuring the pixel current.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic light emitting diode (OLED) display device and a method of measuring a pixel current thereof, and more particularly to an OLED display device capable of reducing the influence of noise and leakage current A display device, and a method of measuring the pixel current.

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.

On the other hand, the pixel current is small and noise is easily inserted in the measurement.

For example, the noise may be generated from a commercial AC power source outside the display panel, or may be mixed with high frequency components such as various driving signals of a plurality of pixels in the display panel.

Therefore, conventionally, there is a problem that accurate pixel current measurement can not be performed due to such noise.

An object of the present invention is to provide an organic light emitting diode display device capable of reducing the influence of noise and leakage current generated in the outside and inside of a display panel during pixel current measurement, And to provide the above objects.

According to an aspect of the present invention, there is provided an organic light emitting diode display device including a display panel displaying an image using a video signal and a plurality of control signals and including a plurality of pixel current measurement lines, A data voltage for measurement is applied to the pixel to be measured connected to the first pixel current measurement line, a black data voltage is applied to the remaining pixels connected to the first pixel current measurement line, A first current flowing through the first pixel current measurement line and a second current flowing through the second pixel current measurement line are measured, and the first current and the second current are calculated And the pixel current in the pixel to be measured in which the noise is removed is measured.

Here, the pixel current measuring line may be a reference voltage line or a data line.

The calculation is preferably a subtraction process.

Further, the first current or the second current may be multiplied by a coefficient prior to the calculation.

It is preferable that the pixel current measurement is performed by converting the voltage into a voltage using the capacitance of the line capacitor existing in the pixel current measurement line.

According to another aspect of the present invention, there is provided a method of measuring a pixel current of an organic light emitting diode (OLED) display device including applying a data voltage for measurement to a pixel to be measured connected to a first pixel current measurement line, Applying a black data voltage to the remaining pixels connected to the first pixel current measurement line and applying a black data voltage to all pixels connected to the second pixel current measurement line; Measuring a first current flowing through the first pixel current measurement line and a second current flowing through the second pixel current measurement line; And measuring a pixel current in the pixel to be measured from which noise has been removed by calculating the first current and the second current.

Here, the pixel current measuring line may be a reference voltage line or a data line.

The calculation is preferably a subtraction process.

The method may further include multiplying the first current or the second current by a coefficient prior to the calculation.

It is preferable that the pixel current measurement is performed by converting the voltage into a voltage using the capacitance of the line capacitor existing in the pixel current measurement line.

As described above, the organic light emitting diode display device and the pixel current measuring method according to the present invention can more accurately measure the pixel current by reducing the influence of noise and leakage current generated from the outside and inside of the display panel .

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.
FIGS. 8 and 9 are views for explaining the noise inserted from the outside of the organic light emitting diode display device in the pixel current measurement.
10A and 10B are diagrams for explaining a noise removing method according to the first embodiment of the present invention.
FIGS. 11A and 11B are diagrams for explaining a process of removing noise while measuring a pixel current in an odd-numbered pixel current measurement line according to the present invention. FIG. 12A and FIG. Which is referred to for describing a process of removing noise while measuring a pixel current in a measurement line.
13A and 13B are views for explaining a noise removing method according to the second embodiment of the present invention.

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

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, (Not shown), a compensation coefficient calculation unit 150, a noise processing unit 160, 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.

The noise processor 160 can remove the noise by calculating the difference of the currents in the pixel current measurement lines connected to the two output channels.

At this time, when the noise inserted into each pixel current measurement line is in phase, the current is immediately subtracted. When the noise inserted into each pixel current measurement line is not in phase, a constant coefficient is multiplied or divided, and then the current is subtracted desirable.

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 set to the reference voltage To the 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 voltage of 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 image signal compensation method according to the present invention, in measuring the pixel current through the pixel current measurement line (reference voltage line, data line), the pixel current is charged into the parasitic capacitor or the like The pixel current can be measured at a high speed by using the voltage.

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

FIGS. 8 and 9 are views for explaining the noise inserted from the outside of the organic light emitting diode display device in the pixel current measurement. 7A.

As shown in FIG. 8, noises can be inserted into the display panel 110 of the organic light emitting diode display by measuring the pixel current.

The noise components entering from the outside of the display panel during the pixel current measurement have many noise components that change the potential of the entire display panel with respect to the ground potential.

In other words, during pixel measurement, all sampling / holding circuits (S / H) can have the same or similar noise in phase and amplitude.

Particularly, noise having substantially the same phase and amplitude can be inserted into the sampling / holding circuit (S / H) connected to the pixel current measuring line located at a distance from each other.

Likewise, in the case of the noise generated from the driving signal inside the display panel during the pixel current measurement, noise having the same or almost similar phase and amplitude may enter the pixel current measurement line at a distance from each other.

As described above, the noise generated from the outside and inside of the display panel has the same or almost similar phase and amplitude to the pixel current measuring lines arranged close to each other.

Therefore, in a state in which the black data voltage is applied to all the pixels of the second pixel current measurement line adjacent to the first pixel current measurement line connected to the pixel to be measured for measuring the pixel current in the pixel current measurement, The noise component can be removed by simultaneously measuring the voltage of the two pixel current measurement lines and calculating the difference between the measured voltages.

Hereinafter, the first line capacitor Cline1 and the second line capacitor Cline2 are connected to the sum of the capacitors of the pixel current measuring lines including the capacitor C existing at the input of the sampling / holding circuit S / H it means.

More specifically, referring to FIG. 9, as shown in FIG. 9, a data voltage for measurement may be applied to the pixel P1m to be measured while a black data voltage may be applied to the remaining pixels.

The first currents i11 to ilM flow in the first line capacitor Cline1 and the second currents i21 to i2M flow in the second line capacitor Cline2 during the third time period C in the measurement mode.

At this time, only the second transistor Tr2 connected to the m-th gate wiring connected to the pixel P1m to be measured is in the on state, and the second transistor Tr2 connected to the remaining gate wiring is in the off state.

However, since the black data voltage is applied to the neighboring pixel P2m, the third transistor of the neighboring pixel P2m is turned off and the size of the second m pixel current i2m is very small.

The pixels P1m and P2m connected to the m-th gate line among the plurality of pixels connected to the first and second pixel current measurement lines connected to the first output channel CH1 and the second output channel CH2, The first and second leakage currents I1 'and I2', which are the sum of the leakage currents in the remaining pixels except the first and second leakage currents I1 'and I2', can be defined by the following equations (4) and (5)

&Quot; (4) "

&Quot; (5) "

Here, i1k and i2k are leakage currents (leakage currents) in the respective pixels, and M is the number of vertical pixels of the display panel.

At this time, since the first and second pixel current measurement lines connected to the first output channel CH1 and the second output channel CH2 are adjacent to each other, it can be assumed that various conditions are similar, And the second leakage currents I1 'and I2' may be the same or substantially similar to each other.

If the second m pixel current i2m of the neighboring pixel P2m to which the black data voltage is applied can be ignored, the first current I1 flowing into the first line capacitor Cline1 and the first current I2 flowing into the second line capacitor Cline2 The difference of the second current I2 flowing in the pixel P1m may be substantially similar to the first m pixel current i1m of the pixel P1m to be measured as shown in Equation (6).

&Quot; (6) "

Therefore, the leakage current in the remaining pixels other than the pixel under measurement connected to the first pixel current measurement line can be eliminated by calculating (subtracting) the current sum in the first and second pixel current measurement lines.

Further, since the pixel current is converted into the voltage by the line capacitor, the charge voltage due to the leakage current can be removed by obtaining the voltage variation amount across the line capacitor, so that the charge voltage by the first m pixel current i1m can be obtained.

That is, the pixel current can be measured by converting the current into a voltage using the capacity of the line capacitor existing in the pixel current measurement line.

10A and 10B are diagrams for explaining a noise removing method according to the first embodiment of the present invention.

In FIG. 10A, the first line capacitor Cline1 and the second line capacitor Cline2 in the case where noise having the same phase and the same amplitude are inserted into the first output channel CH1 and the second output channel CH2, Respectively.

At this time, the measurement data voltage is applied through the first output channel CH1 and the black data voltage is applied through the second output channel CH2.

The voltages V11 and V12 in the first line capacitor Cline1 and the voltages V21 and V22 in the second line capacitor Cline2 are changed in a linear function form before the noise is inserted, .

Noises are inserted into the voltages V11 and V12 in the first line capacitor Cline1 and the voltages V21 and V22 in the second line capacitor Cline2 to change waveforms.

At this time, the waveform of the inserted noise may be in the form of an arbitrary waveform having the first noise voltage VN1 and the second noise voltage VN2 at the first and second time points t1 and t2, respectively.

As a result, the voltages' V11 and V12 'in the first line capacitor Cline1 become' V11 + VN1 and V12 + VN2 ', and the voltages' V21 and V22' in the second line capacitor Cline2 become 'V21 + VN1, V22 + VN2 '.

Here, V11 and V12 are voltages at the first pixel current measurement line connected to the first output channel (CH1) measured at the first and second time points t1 and t2, respectively, and V21 and V22 are voltages at the first and second time points Is a voltage at the second pixel current measurement line connected to the second output channel (CH2) measured at the second time point (t1, t2).

As shown in Fig. 10B, when the voltage at the second line capacitor Cline2 is inverted and the inverted voltage is added to the voltage at the first line capacitor Cline1 via the adder, the noise can be removed.

That is, when the voltage of the second line capacitor Cline2 is inverted and the inverted voltage is added to the voltage of the first line capacitor Cline1 through the adder, the noise is removed by the sum, the voltages at the two pixel current measurement lines at the times t1 and t2 become 'V11-V21 and V12-V22', respectively.

By applying the 'V11-V21 and V12-V22' to the equation (3), the noise-eliminated pixel current can be obtained.

FIGS. 11A and 11B are diagrams for explaining a process of removing noise while measuring a pixel current in an odd-numbered pixel current measurement line according to the present invention. FIG. 12A and FIG. Which is referred to for describing a process of removing noise while measuring a pixel current in a measurement line.

The pixel current measuring lines are preferably similar to the noise components even when the pixel current measuring lines located at a close distance from each other are selected so as to remove the noise through calculation.

In the following description, the first and second pixel current measurement lines are selected (computed) as neighboring pixel current measurement lines. However, the present invention is not limited thereto and it is not necessary to select neighboring pixel current measurement lines.

As shown in FIGS. 11A and 11B, first, a data voltage for measurement is applied through a first pixel current measurement line connected to the odd-numbered output channels CH1, CH3, CH4, ...) through the second pixel current measurement line.

Then, any pixel connected to the first pixel current measurement line connected to the odd-numbered output channels CH1, CH3, ... may be selected to measure the pixel current.

Next, as shown in FIGS. 12A and 12B, the measurement data voltage is applied through the second pixel current measurement line connected to the even-numbered output channels (CH2, CH4, ..), and the odd- CH1, CH3, ...) of the first pixel current measurement line.

The pixel current may be measured by selecting any pixel connected to the second pixel current measurement line connected to the even-numbered output channels (CH2, CH4, ..).

At this time, since the black data voltage is applied to the remaining pixels, a leakage current may be generated, which may interfere with accurate pixel current measurement in addition to noise from the outside of the display panel.

However, as described above, by calculating the voltage difference in the line capacitors in the neighboring pixel current measurement lines in the measurement mode, it is possible to eliminate the influence of the noise and the leakage current.

13A and 13B are views for explaining a noise removing method according to the second embodiment of the present invention.

When the leakage current in the pixel to which the black data voltage is applied is small and the elimination of the inserted noise is the main object, it is preferable that the amplitude of the noise of the pixel current measurement line adjacent to the pixel current measurement line to which the pixel to be measured is connected is not the same If it is experimentally known, it is also desirable to multiply by a constant coefficient and subtract.

13A, the charging waveforms of the first line capacitor Cline 1 and the second line capacitor Cline 2 at the time of insertion of the noise having the amplitudes of the amplitudes of the first output channel CH 1 and the second output channel CH 2 are Respectively.

The first noise is inserted into the voltages V11 and V12 in the first line capacitor Cline1 and the second noise is added to the voltages V21 and V22 in the second line capacitor Cline2 as shown in Fig. Is inserted and the waveform is changed.

At this time, the waveform of the inserted first noise may be in the form of an arbitrary waveform having the first noise voltage VN1 and the second noise voltage VN2 at the first and second time points t1 and t2, respectively, The noise may be a form in which the first noise is multiplied by?.

As a result, the voltages' V11 and V12 'in the first line capacitor Cline1 become' V11 + VN1 and V12 + VN2 ', and the voltages' V21 and V22' in the second line capacitor Cline2 become 'V21 + ? VN1, V22 +? VN2 '.

13B, when the voltage of the second line capacitor Cline2 is multiplied by 1 / [beta], and the inverted voltage and the voltage of the first line capacitor Cline1 are added together through an adder, noise is removed The pixel current can be measured.

That is, when the voltage obtained by inverting the voltage of the second line capacitor Cline2 and the voltage of the first line capacitor Cline1 are added together through an adder, the noise is removed by the sum and the first and second time points t1 , t2), the voltages on the two pixel current measurement lines become 'V11-V21 / β and V12-V22 / β', respectively.

Applying this 'V11-V21 / β, V12-V22 / β' to Equation (3), the noise-eliminated pixel current can be obtained.

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
160: Noise processor

Claims (12)

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,
A data voltage for measurement is applied to a pixel to be measured connected to a first pixel current measurement line in a pixel current measurement, a black data voltage is applied to a remaining pixel connected to the first pixel current measurement line, A black data voltage is applied to all the pixels connected to the line,
Measuring a first current flowing through the first pixel current measurement line and a second current flowing through the second pixel current measurement line,
And the pixel current in the pixel to be measured in which the noise is removed is measured by calculating the first current and the second current,
The first or second current measurement may be performed by measuring a value obtained by adding the capacitance of the capacitor connected in parallel to the input terminal of the sampling and holding circuit to the capacitance of the line capacitor existing in each pixel current measurement line, And dividing the difference by the time difference between the second time point and the first time point.
The method according to claim 1,
Wherein the pixel current measuring line is a reference voltage line or a data line.
The method according to claim 1,
Wherein the operation is a subtraction process.
The method according to claim 1,
Wherein the first current or the second current is multiplied by a coefficient prior to the operation.
delete A data voltage for measurement is applied to the pixel to be measured connected to the first pixel current measurement line, a black data voltage is applied to the remaining pixels connected to the first pixel current measurement line, Applying a black data voltage to all pixels;
Measuring a first current flowing through the first pixel current measurement line and a second current flowing through the second pixel current measurement line;
And measuring the pixel current in the pixel to be measured from which noise has been removed by calculating the first current and the second current,
The first or second current measurement may be performed by measuring a value obtained by adding the capacitance of the capacitor connected in parallel to the input terminal of the sampling and holding circuit to the capacitance of the line capacitor existing in each pixel current measurement line, And dividing the difference between the second time point and the first time point by a difference between voltages of the pixel current measuring lines.
The method according to claim 6,
Wherein the pixel current measurement line is a reference voltage line or a data line.
The method according to claim 6,
Wherein the calculation is a subtraction process. ≪ RTI ID = 0.0 > 11. < / RTI >
The method according to claim 6,
Further comprising the step of multiplying a first current or a second current by a coefficient prior to the calculation.
delete The method according to claim 1,
Wherein when the noise inserted into each pixel current measurement line is in phase, the second current is subtracted from the first current, and when the noise inserted into each pixel current measurement line is not in phase, And subtracts the second current from the first current.
The method according to claim 6,
Wherein when the noise inserted into each pixel current measurement line is in phase, the second current is subtracted from the first current, and when the noise inserted into each pixel current measurement line is not in phase, And subtracting the second current from the first current. A method of measuring a pixel current of an organic light emitting diode display, comprising:

Images