KR102438258B1 - Method of sensing organic light-emitting display device - Google Patents

Abstract

The present invention relates to an organic light emitting display device capable of shortening a time for sensing threshold voltage mobility of a driving transistor of the organic light emitting display device and a sensing method of the organic light emitting display device. The method includes an initialization step of applying a sensing data voltage to a gate node of a driving transistor, and turning on a sensing transistor to supply an initialization voltage to a source node of the driving transistor: turning off the sensing transistor and the sensing transistor pre-charging the line capacitor by varying the voltage provided to the line capacitor; charging the line capacitor connected to the sensing line by turning on the sensing transistor again; and a sampling step of turning off the sensing transistor again to output the voltage stored in the line capacitor as a sensing voltage, and sensing the threshold voltage by pre-charging the line capacitor of the sensing line prior to sensing the driving transistor. It is possible to reduce the time, thereby reducing the production time can have the effect of improving the production yield of the product.

Description

An organic light emitting display device and a sensing method of an organic light emitting display device TECHNICAL FIELD

The present invention relates to an organic light emitting display device and a sensing method of the organic light emitting display device, and more particularly, to an organic light emitting display device and an organic light emitting diode display capable of reducing a time for sensing threshold voltage mobility of a driving transistor of the organic light emitting display device The present invention relates to a sensing method of a light emitting display device.

In recent years, display devices have been rapidly developed along with the development of information and communication technologies. In particular, an organic light emitting diode display among display devices is a self-luminous device and does not need to include a separate backlight unit, so it can be formed thinner than other display devices and have low power consumption.

The organic light emitting display controls the current flowing from the drain to the source of the driving TFT by controlling the voltage between the gate terminal and the source terminal of the driving transistor (hereinafter referred to as a 'driving TFT'). The current flowing from the drain to the source of the driving TFT emits light while flowing to the organic light emitting diode, and the degree of light emission is controlled by controlling the amount of current.

The organic light emitting display senses the TFT parameter by an external compensation method. Here, the external compensation method includes a high-speed sensing waveform for compensating for mobility and a low-speed sensing waveform for compensating for a threshold voltage.

Since the threshold voltage is compensated by the low-speed sensing waveform, it takes a long time for the sensing voltage to be charged in the capacitor, which causes a problem that it takes a considerable amount of time to sense the threshold voltage.

An object of the present invention is to provide an organic light emitting display device and a sensing method of the organic light emitting display device that can reduce the time required for sensing a threshold voltage of a driving transistor of the organic light emitting display device.

An organic light emitting display device according to the present invention includes an organic light emitting device, a plurality of sub-pixels each having a driving transistor for controlling the amount of light emitted from the organic light emitting device, and a sensing transistor connected to at least one of the sub-pixels through a sensing line. a display panel; and a data driver for pre-charging a line capacitor of a sensing line before sensing the driving characteristic of the driving transistor after initialization of the driving transistor in a sensing mode for sensing the driving characteristic of the driving transistor.

The data driver of the organic light emitting diode display according to the present invention supplies the reference voltage changed for a predetermined time to the line capacitor of the sensing line to pre-charge the line capacitor of the sensing line.

The variable reference voltage output from the data driver of the organic light emitting diode display according to the present invention is higher than the initialization voltage of the driving transistor and lower than the sensing target voltage.

The sensing method of an organic light emitting display device according to the present invention includes an organic light emitting diode, a plurality of sub-pixels each having a driving transistor for controlling the amount of light emitted by the organic light emitting diode, and sensing connected to at least one of the sub-pixels through a sensing line. A sensing method of an organic light emitting display device including a transistor, comprising: an initialization step of applying a sensing data voltage to a gate node of a driving transistor, and turning on the sensing transistor to supply an initialization voltage to a source node of the driving transistor; turning off the sensing transistor and pre-charging a line capacitor by varying a voltage provided to the sensing transistor; charging the line capacitor connected to the sensing line by turning on the sensing transistor again; and a sampling step of turning off the sensing transistor again to output the voltage stored in the line capacitor as a sensing voltage.

In the sensing method of the organic light emitting display device according to the present invention, the pre-charging step includes maintaining a sensing data voltage applied to a gate node of the driving transistor, turning off the sensing transistor, and A line capacitor is pre-charged by applying a variable reference voltage through a sensing line connected to the source node of the driving transistor.

The embodiment of the present invention has an effect of reducing the threshold voltage sensing time by pre-charging the line capacitor of the sensing line prior to sensing the driving transistor.

In addition, by reducing the sensing time of the threshold voltage, it is possible to have the effect of reducing the production time and improving the production yield of the product.

1 is a block diagram schematically illustrating an organic light emitting diode display according to the present invention.
2 is an exemplary diagram of a sub-pixel structure of an organic light emitting diode display according to an embodiment of the present invention.
3 is a waveform diagram for sensing a threshold voltage of a general organic light emitting diode display.
4 is a waveform diagram for sensing a threshold voltage of an organic light emitting diode display according to the present invention.
5 is an exemplary diagram illustrating operations of a sub-pixel and a sensing transistor in the initialization period of FIG. 4 .
FIG. 6 is an exemplary diagram illustrating operations of a sub-pixel and a sensing transistor in the preliminary charging period of FIG. 4 .
7 is an exemplary diagram illustrating operations of a sub-pixel and a sensing transistor in the sensing period of FIG. 4 .
8 is an exemplary diagram illustrating operations of a sub-pixel and a sensing transistor in the sampling period of FIG. 4 .
9 is a flowchart illustrating a process of a sensing method of an organic light emitting display device according to the present invention.
10 is a signal waveform diagram of a sensed voltage in the organic light emitting diode display according to the present invention.
11 is an enlarged view of a portion “A” of FIG. 10 .

With respect to the embodiments of the present invention disclosed in the text, specific structural or functional descriptions are only exemplified for the purpose of describing the embodiments of the present invention, the embodiments of the present invention may be implemented in various forms and It should not be construed as being limited to the described embodiments.

Since the present invention can have various changes and can have various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to the specific disclosed form, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

Terms such as first, second, etc. may be used to describe various elements, but the elements are not limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component.

When a component is referred to as being “connected” or “connected” to another component, it may be directly connected or connected to the other component, but it is understood that other components may exist in between. it should be On the other hand, when it is said that a certain element is "directly connected" or "directly connected" to another element, it should be understood that there is no other element in the middle. Other expressions describing the relationship between elements, such as "between" and "immediately between" or "neighboring to" and "directly adjacent to", etc., should be interpreted similarly.

The terms used in the present application are only used to describe specific embodiments, and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. In this application, terms such as "comprises" or "having" are intended to designate that the disclosed feature, number, step, action, component, part, or combination thereof is present, but includes one or more other features or numbers, It should be understood that the possibility of the presence or addition of steps, operations, components, parts or combinations thereof is not precluded in advance.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as indicating meanings consistent with the meanings in the context of the related art, and should not be interpreted in an ideal or excessively formal meaning unless explicitly defined in the present application. does not

On the other hand, when an embodiment can be implemented differently, functions or operations specified in a specific block may occur differently from the order specified in the flowchart. For example, two consecutive blocks may be performed substantially simultaneously, or the blocks may be performed in reverse according to a related function or operation.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

1 is a schematic system configuration diagram of an organic light emitting diode display according to the present invention, and FIG. 2 is an exemplary diagram of a sub-pixel structure of an organic light emitting display according to an embodiment of the present invention.

Referring to FIG. 1 , in the organic light emitting diode display 100 according to the present invention, a plurality of data lines DL and a plurality of gate lines GL are disposed, and a plurality of sub-pixels (SP) are disposed. display panel 110 , a data driver 120 driving a plurality of data lines DL, a gate driver 130 driving a plurality of gate lines GL, a data driver 120 , and a gate driver and a timing control unit 140 for controlling 130 and the like.

The timing controller 140 supplies various control signals to the data driver 120 and the gate driver 130 to control the data driver 120 and the gate driver 130 .

The timing controller 140 starts scanning according to the timing implemented in each frame, and converts the input image data input from the outside according to the data signal format used by the data driver 120 to convert the converted driving data DATA. output and control the display driving data at an appropriate time according to the scan signal.

The data driver 120 drives the plurality of data lines DL by supplying the driving data voltage Vdata to the plurality of data lines DL. Here, the data driver 120 is also referred to as a 'source driver'.

The gate driver 130 sequentially supplies a scan signal of an on voltage or an off voltage to the plurality of gate lines GL under the control of the timing controller 140 , so that the plurality of gates The lines GL are sequentially driven. Here, the gate driver 130 is also referred to as a 'scan driver'.

When a specific gate line is opened by the gate driver 130 , the data driver 120 converts the image data received from the timing controller 140 into an analog data voltage and supplies it to the plurality of data lines DL.

Although the data driver 120 is illustrated to be positioned on only one side (eg, upper or lower side) of the display panel 110 in FIG. 1 , both sides (eg, the upper side) of the display panel 110 according to a driving method, a panel design method, etc. and below) may also be located.

Although the gate driver 130 is illustrated to be positioned only on one side (eg, left or right) of the display panel 110 in FIG. 1 , the gate driver 130 is positioned on both sides (eg, the left side) of the display panel 110 according to a driving method and a panel design method. may be located on both the left and right).

The above-described timing controller 140 may include various types of data including a vertical synchronization signal (Vsync), a horizontal synchronization signal (Hsync), an input data enable (DE) signal, a clock signal (CLK), etc. together with the input image data. Timing signals are received from the outside (eg host system).

The timing controller 140 converts the input image data input from the outside to match the data signal format used by the data driver 120 and outputs the converted image data, as well as the data driver 120 and the gate driver 130 . The data driver 120 and the gate driver 130 receive a timing signal such as a vertical synchronization signal (Vsync), a horizontal synchronization signal (Hsync), an input DE signal, and a clock signal to generate various control signals to control the output as

For example, in order to control the gate driver 130 , the timing controller 140 includes a gate start pulse (GSP), a gate shift clock (GSC), and a gate output enable signal (GOE). Various gate control signals (GCS: Gate Control Signal) including Gate Output Enable) are output.

Here, the gate start pulse GSP controls the operation start timing of one or more gate driver ICs constituting the gate driver 130 . The gate shift clock GSC is a clock signal commonly input to one or more gate driver integrated circuits and controls shift timing of a scan signal (gate pulse). The gate output enable signal GOE specifies timing information of one or more gate driver integrated circuits.

In addition, the timing controller 140 controls the data driver 120, a data start pulse (SSP: Source Start Pulse), a data sampling clock (SSC: Source Sampling Clock), a data output enable signal (SOE) : Outputs various data control signals (DCS: Data Control Signal) including Source Output Enable).

Here, the data start pulse SSP controls the data sampling start timing of one or more data driver ICs constituting the data driver 120 . The data sampling clock SSC is a clock signal that controls sampling timing of data in each of the data driver integrated circuits. The data output enable signal SOE controls the output timing of the data driver 120 .

The data driver 120 may include at least one data driver integrated circuit (SDIC) to drive a plurality of data lines.

Each data driver integrated circuit (SDIC) may include a shift register, a latch circuit, a digital to analog converter (DAC), an output buffer, a gamma voltage generator, etc. can

Each data driver integrated circuit SDIC may further include an analog-to-digital converter (ADC) in some cases.

The gate driver 130 may include at least one gate driver integrated circuit (GDIC).

Each gate driver integrated circuit GDIC may include a shift register, a level shifter, and the like.

Each sub-pixel SP disposed on the display panel 110 may include a circuit element such as a transistor.

For example, in the display panel 110 , each sub-pixel SP is composed of an organic light emitting diode (OLED) and circuit elements such as a driving transistor (DT) for driving the organic light emitting diode (OLED). .

The type and number of circuit elements constituting each sub-pixel SP may be variously determined according to a provided function and a design method.

Referring to FIG. 2 , in the organic light emitting diode display 100 according to the present invention, each sub-pixel includes an organic light emitting diode (OLED) and a driving transistor DT for driving the organic light emitting diode (OLED). : A sensing line that supplies a driving transistor, a second node N2 of the driving transistor DT, and a reference voltage (Vref), and transmits a sensing value of the driving transistor DT to the data driver 120 . The first transistor T1 electrically connected between the SL and the first node N1 of the driving transistor DT and the second electrically connected between the data line DL supplying the data voltage Vdata The second transistor T2 and a storage capacitor Cstg electrically connected between the second node N2 and the first node N1 of the driving transistor DT are included.

The sensing line SL includes an initialization control signal switch SPRE for applying the reference voltage Vref to the sensing transistor T1, and a line capacitor Csen that performs a charging operation for sensing the driving transistor DT; A sampling switch SAM for transferring the sensing threshold voltage of the driving transistor DT charged in the line capacitor Csen to the analog-to-digital converter ADC of the data driver 130 is configured.

The organic light emitting diode (OLED) may include a first electrode (eg, an anode electrode or a cathode electrode), an organic light emitting layer, and a second electrode (eg, a cathode electrode or an anode electrode).

The driving transistor DT drives the organic light emitting diode OLED by supplying a driving current to the organic light emitting diode OLED.

The second node N2 of the driving transistor DT may be electrically connected to the first electrode of the organic light emitting diode OLED, and may be a data node or a drain node. The first node N1 of the driving transistor DT may be electrically connected to a data node or a drain node of the second transistor T2 , and may be a gate node. The second node N2 of the driving transistor DT may be electrically connected to a driving voltage line supplying the driving voltage EVDD, and may be a drain node or a data node.

As shown in FIG. 2 , the first transistor T1 is turned on by the sensing signal SENSE, and the second node N2 of the driving transistor DT is referenced through the initialization control signal switch SPRE. A voltage Vref may be applied.

Also, when the first transistor T1 is turned on, it may be used as a voltage sensing path for the second node N2 of the driving transistor DT.

When the second transistor T2 is turned on by the scan signal SCAN, it transfers the data voltage Vdata supplied through the data line DL to the first node N1 of the driving transistor DT.

The storage capacitor Cst is electrically connected between the second node N2 and the first node N1 of the driving transistor DT, and applies a data voltage corresponding to the image signal voltage or a voltage corresponding thereto for one frame time. can keep you

The storage capacitor Cstg is not a parasitic capacitor (eg, Cgs, Cgd) which is an internal capacitor existing between the second node N2 and the first node N1 of the driving transistor DT, It is an external capacitor intentionally designed outside the driving transistor DT.

In the sensing mode for sensing the driving characteristics of the driving transistor DT, the data driver 120 of the present invention includes a sensing line ( SL) of the line capacitor Csen is pre-charged. The operation of the data driver 120 is controlled by the timing controller 140 .

3 is a waveform diagram for sensing a threshold voltage of a general organic light emitting diode display.

The timing controller 140 drives the display panel 110 in a display mode or a sensing mode. Here, the display mode means driving the display panel 110 to display a predetermined image by emitting organic light emitting devices included in each sub-pixel SP according to input data, and the sensing mode is driving for each pixel. It means driving the display panel 110 to sense the threshold voltage and/or mobility of the transistor. For example, the sensing mode may be performed when a user (or a product) is set before product shipment of the organic light emitting diode display device, and may be performed at a user setting or every set period after product shipment of the organic light emitting display device. Here, the set period may be a power-on period of the organic light emitting display device, a power-off period of the organic light emitting diode display, a power-on period after a set driving time, or a power-off period after a set driving time.

A typical threshold voltage sensing period includes an initialization step Tinit for initializing the driving transistor DT, a sensing step Tsense of charging the source node voltage of the driving transistor DT to the line capacitor Csen of the sensing line, and sampling The voltage charged in the line capacitor Csen of the sensing line SL is transferred to the analog-to-digital converter ADC according to the signal to sense the threshold voltage of the driving transistor DT. Although this sensing method enables relatively accurate sensing, sensing is possible only when the line capacitor Csen is charged by the storage capacitor Cstg. At this time, the time required for charging the line capacitor Csen is 10 ms per horizontal line for each color. Therefore, the general threshold voltage sensing time (“A”) becomes long, and in particular, in the case of a high-resolution model, a considerably long time is required.

4 is a waveform diagram for sensing a threshold voltage of an organic light emitting diode display according to the present invention. Unlike a signal waveform diagram for sensing a threshold voltage of a general organic light emitting diode display, the waveform diagram for sensing a threshold voltage of an organic light emitting display according to the present invention includes a precharge period (Tprecharge).

In the initialization period Tinit, the scan control signal SCAN, the sensing control signal SENSE, and the initialization reference voltage control signal SPRE are all applied at an on level. At this time, the initialization reference voltage Vref is applied in an off-level state.

In the preliminary charging period Tprecharge, the scan control signal SCAN and the initialization reference voltage control signal SPRE maintain an on level, but the sensing control signal SENSE is temporarily switched to an off level. At this time, the initialization reference voltage Vref is switched to an on-level state.

In the sensing period Tsense, the scan control signal SCAN maintains an on level, the sensing control signal SENSE temporarily switched to an off level is switched back to an on level, and the initialization reference voltage control signal SPRE is turned off. converted to level. At this time, although the initialization reference voltage Vref maintains an on-level state, the initialization reference voltage control signal SPRE is switched to an off-level, and thus does not substantially affect sensing.

In the sampling period Tsam, the sensing control signal SENSE is switched to the off level, the sampling signal SAM is switched to the on level, and the voltage charged in the line capacitor Csen of the sensing line is applied to the data driver 120 . to an analog-to-digital converter (ADC).

Since the line capacitor Csen is pre-charged to some extent by momentarily varying the reference voltage, the sensing time “B” for finally sensing the mobility of the threshold voltage of the driving transistor DT of the organic light emitting diode display can be shortened. have.

5 is an exemplary diagram illustrating operations of a sub-pixel and a sensing transistor in the initialization period of FIG. 4 .

During the initialization period Tinit, since the scan control signal SCAN, the sensing control signal SENSE, and the initialization reference voltage control signal SPRE are all applied at an on level, when the initialization reference voltage control switch SPRE is turned on, , a reference voltage Vref(a), which is an initialization voltage, may be supplied to the reference terminal Vs of the driving transistor DT through the sensing transistor T1 .

The scan transistor T2 is turned on to supply the sensing data voltage Vdata to the gate node Ng of the driving transistor DT. The sensing transistor T1 and the initialization reference voltage control switch SPRE are turned on to apply the initialization reference voltage control signal Vref to the source node Ns of the driving transistor DT. As a result, the driving transistor DT is initialized.

FIG. 6 is an exemplary diagram illustrating operations of a sub-pixel and a sensing transistor in the preliminary charging period of FIG. 4 .

During the preliminary charging period Tprecharge, the initialization reference voltage control signal SPRE maintains an on level and the reference voltage control signal Vref is switched to an on-level state, so unlike the initialization reference voltage Vref(a), it is variable It is in a state in which the reference voltage Vref(b) can be transferred to the rear end.

Since the sensing control signal SENSE is temporarily switched to the off level, the sensing transistor T1 is turned off. Accordingly, as shown, the variable reference voltage Vref(b) is charged in the line capacitor Csen connected to the sensing line SL. The variable reference voltage Vref(b) is higher than the reference voltage Vref(a) provided to initialize the driving transistor DT during the initialization period Tinit and is lower than the sensing target voltage Vsen.

7 is an exemplary diagram illustrating operations of a sub-pixel and a sensing transistor in the sensing period of FIG. 4 .

During the sensing period Tsense, the sensing control signal SENSE, which was temporarily switched to the off level, is switched back to the on level, so that the sensing transistor T1 is turned on. Meanwhile, since the reference voltage control signal SPRE is switched to the off level, the reference voltage control switch SPRE is turned off, and thus sensing between the driving transistor DT operating in a source follower mode and the organic light emitting diode. The voltage of the node N2 is sensed by the line capacitor Csen connected to the sensing line SL. Accordingly, the driving characteristic of the driving transistor is sensed.

8 is an exemplary diagram illustrating operations of a sub-pixel and a sensing transistor in the sampling period of FIG. 4 .

During the sampling period Tsam, the sensing transistor T1 is turned off while the sensing control signal SENSE is switched to an off level. At this time, since the sampling signal SAM is switched to the on level, the sampling switch SAM is turned on. The voltage charged in the line capacitor Csen is converted into a digital signal by the analog-to-digital converter ADC connected to the sensing line SL and transmitted to the data driver 120 .

9 is a flowchart illustrating a process of a sensing method of an organic light emitting display device according to the present invention.

As shown, an initialization step of applying a sensing data voltage to the gate node of the driving transistor DT and turning on the sensing transistor T1 to supply an initialization voltage to the source node of the driving transistor DT carry out (S901).

Next, when the initialization step is completed, the sensing transistor DT is turned off, and the voltage applied to the sensing transistor DT is varied to pre-charge the line capacitor Csen ( S902 ).

The sensing transistor T1 is turned on again to charge the line capacitor Csen connected to the sensing line SL (S903).

The sensing transistor T1 is turned off again, and the voltage stored in the line capacitor Csen is output as the sensing voltage (S904).

FIG. 10 is a signal waveform diagram of a sensing voltage Vsen in an organic light emitting diode display according to the present invention, and FIG. 11 is an enlarged view of portion “A” of FIG. 10 .

The threshold voltage sensing method according to the present invention may reach a target voltage within a short time by pre-charging the line capacitor Csen through preliminary charging. Therefore, as shown in the enlarged view of FIG. 11, the voltage Vsen (V1) charged in the line capacitor Csen according to the general sensing method reaches 10 ms after the sensing mode starts. It can reach 4.18V. According to the sensing method according to the present invention, the voltage Vsen (V2) charged in the line capacitor Csen may reach a target voltage of 4.18V when it reaches 8.86 ms after the sensing mode starts.

The effect of the present invention may represent a performance improvement of 11.1% as shown in [Table 1] below.

target voltage

Sensing Time
traditional method
4.18

10.0 ms
new method
4.18

8.86 ms
Performance
100%

111. One %

As described above, in the sensing method of the organic light emitting diode display according to the present invention, the sensing time of the threshold voltage can be reduced by pre-charging the line capacitor of the sensing line prior to the sensing of the driving transistor, and the production time is also reduced to produce a product. It may have the effect of improving the yield.

Although the above has been described with reference to preferred embodiments of the present invention, those skilled in the art can variously modify and change the present invention within the scope without departing from the spirit and scope of the present invention as set forth in the claims below. You will understand that it can be done.

100: organic light emitting display device 110: display panel
120: data driver 130: gate driver
140: timing control

Claims (6)

A display panel comprising: a display panel including an organic light emitting device, a plurality of sub-pixels each having a driving transistor controlling the amount of light emitted from the organic light emitting device, and a sensing transistor, and a sensing line connected to any one of the sub-pixels;
In the sensing mode for sensing the driving characteristic of the driving transistor, after applying an initialization voltage to the source node of the driving transistor to initialize the driving transistor, and before sensing the driving characteristic of the driving transistor, it is applied to the line capacitor of the sensing line. and a data driver for pre-charging the line capacitor of the sensing line by supplying a reference voltage varied for a predetermined time,
The variable reference voltage is higher than the initialization voltage and lower than the sensing target voltage. delete delete An organic light emitting display device including an organic light emitting diode, a driving transistor for controlling the amount of light emitted from the organic light emitting diode, and a plurality of sub-pixels each having a sensing transistor, and a sensing line connected to one of the sensing transistors among the sub-pixels In the sensing method of
An initialization step of supplying an initialization voltage to a source node of the driving transistor by turning on the sensing transistor:
pre-charging the line capacitor of the sensing line by turning off the sensing transistor and supplying a reference voltage varying for a predetermined time to the line capacitor of the sensing line;
charging a voltage in a line capacitor of the sensing line by turning on the sensing transistor again; and
and a sampling step of turning off the sensing transistor again to output the voltage stored in the line capacitor as a sensing voltage,
The variable reference voltage is higher than the initialization voltage and lower than the sensing target voltage. delete 5. The method of claim 4,
In the initialization step, a sensing data voltage is applied to the gate node of the driving transistor,
The sensing data voltage applied to the gate node of the driving transistor is maintained in the pre-charging step.

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