KR101577907B1 - Method For Sensing Threshold Voltage Change Value Of Organic Light Emitting Display - Google Patents

Method For Sensing Threshold Voltage Change Value Of Organic Light Emitting Display Download PDF

Info

Publication number
KR101577907B1
KR101577907B1 KR1020140115972A KR20140115972A KR101577907B1 KR 101577907 B1 KR101577907 B1 KR 101577907B1 KR 1020140115972 A KR1020140115972 A KR 1020140115972A KR 20140115972 A KR20140115972 A KR 20140115972A KR 101577907 B1 KR101577907 B1 KR 101577907B1
Authority
KR
South Korea
Prior art keywords
sensing
tft
voltage
driving tft
threshold voltage
Prior art date
Application number
KR1020140115972A
Other languages
Korean (ko)
Inventor
김태궁
윤진한
Original Assignee
엘지디스플레이 주식회사
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by 엘지디스플레이 주식회사 filed Critical 엘지디스플레이 주식회사
Priority to KR1020140115972A priority Critical patent/KR101577907B1/en
Application granted granted Critical
Publication of KR101577907B1 publication Critical patent/KR101577907B1/en

Links

Images

Classifications

    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
    • G09G3/3225—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix
    • G09G3/3233—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix with pixel circuitry controlling the current through the light-emitting element
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
    • G09G3/3275—Details of drivers for data electrodes

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Control Of El Displays (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)

Abstract

A threshold voltage change value sensing method of an organic light emitting display device including a plurality of pixels each having an OLED and a driving TFT controlling the amount of light emission of the OLED is disclosed. This threshold voltage change value sensing method significantly reduces the time required for sensing including the programming step, the mobility compensation step, the sensing step, and the sampling step. Accordingly, the present invention enables sensing in the vertical blank period during real-time driving, thereby further improving the compensation performance.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for sensing a threshold voltage change value of an organic light emitting display,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to an organic light emitting display, and more particularly, to a threshold voltage change value sensing method for an organic light emitting display device for compensating a variation in electrical characteristics of a driving device.

The active matrix type organic light emitting display device includes an organic light emitting diode (OLED) which emits light by itself, has a high response speed, and has a high luminous efficiency, luminance, and viewing angle.

The organic light emitting diode (OLED) includes an anode electrode, a cathode electrode, and organic compound layers (HIL, HTL, EML, ETL, EIL) formed therebetween. The organic compound layer includes a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and an electron injection layer EIL). When a driving voltage is applied to the anode electrode and the cathode electrode, holes passing through the HTL and electrons passing through the ETL are transferred to the EML to form excitons, Thereby generating visible light.

The organic light emitting display device arranges the pixels each including the OLED in a matrix form and adjusts the brightness of the pixels according to the gradation of the video data. Each of the pixels includes a driving TFT (Thin Film Transistor) for controlling a driving current flowing in the OLED. The electrical characteristics of the driving TFT, such as threshold voltage, mobility, etc., may vary from pixel to pixel depending on process conditions, driving environment, and the like. Such an electric characteristic deviation of the driving TFT causes a luminance deviation between the pixels. In order to solve this problem, there has been known a technique of sensing characteristic parameters (threshold voltage, mobility) of driving TFTs from each pixel and correcting the image data based on the sensing result.

In this prior art, in order to sense a change in the threshold voltage (Vth) of the drive TFT (DT), the drive TFT (DT) is operated in a source follower manner as shown in Fig. 1, The source node voltage Vs of the driving TFT DT is set to the sensing voltage Vsen at the time ta when the gate-source voltage Vgs of the driving TFT DT reaches the saturation state by the current, . It takes a long time until the gate-source voltage Vgs of the driving TFT DT reaches the threshold voltage Vth of the driving TFT DT. Therefore, in the prior art, it is impossible to sense a change in the threshold voltage (Vth) of the driving TFT (DT) during real time driving.

Accordingly, it is an object of the present invention to provide a threshold voltage change value sensing method of an organic light emitting display capable of reducing a time required for sensing a threshold voltage change value of a driving TFT.

In order to achieve the above object, a threshold voltage change value sensing method of an organic light emitting display including a plurality of pixels each having an OLED and a driving TFT controlling the amount of light emission of the OLED, includes the steps of programming, mobility compensation, , And a sampling step.

The programming step applies a sensing data voltage to the gate node of the driving TFT and applies a reference voltage to the source node of the driving TFT to program the gate-source voltage (Vgs) of the driving TFT to the first level. The mobility compensating step holds the sensing data voltage at the gate node of the driving TFT and changes the Vgs of the driving TFT to a second level lower than the first level by floating the source node of the driving TFT, To compensate for the change in mobility. In the sensing step, a pixel current is supplied to the drive TFT in accordance with the second level of Vgs while the gate node of the drive TFT is floating, and the source node voltage of the drive TFT increased by the pixel current is sensed. The sampling step samples the source node voltage of the driving TFT to a sensing voltage for deriving a threshold voltage change value of the driving TFT.

A method of sensing a threshold voltage change value of an organic light emitting display device includes the steps of: compensating a mobility change of the drive TFT and sensing a source node voltage of the drive TFT, And a source node initialization step of initializing the source node of the drive TFT while applying the reference voltage again to the source node of the TFT to maintain the Vgs of the second level.

A method of sensing a threshold voltage change value of an organic light emitting display device includes calculating a change value of the sensing voltage by comparing the sensing voltage with a preset reference sensing value and using the change value of the sensing voltage as a read address, And reading the threshold voltage change value of the driving TFT.

The sensing step and the sampling step are performed in a linear section of the TFT in which Vgs of the drive TFT is larger than the threshold voltage of the drive TFT.

Wherein the programming step, the mobility compensation step, the source node initialization step, the sensing step, and the sampling step are performed in a vertical blanking period; The vertical blanking period indicates a period of time during which the writing of data for image display is not performed between the active periods for image display.

 Since the present invention performs sensing and sampling at an arbitrary point in time in the TFT linear section after internally compensating the mobility change internally, the time required to sense the threshold voltage change value of the driving TFT can be drastically reduced .

Accordingly, the present invention enables sensing in the vertical blank period during real-time driving, thereby further improving the compensation performance.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a diagram showing a conventional technique for sensing a threshold voltage change value of a driving TFT in a source follower manner. Fig.
BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]
3 is a view showing a configuration example of a pixel array and a data driver IC;
4 is a circuit diagram showing a detailed configuration of a pixel and a sensing unit according to an embodiment of the present invention;
5 is a waveform diagram sequentially illustrating a threshold voltage change value sensing process of a driving TFT according to an embodiment of the present invention.
6 is a view showing that a threshold voltage change value of a driving TFT appears as a curve slope difference in a TFT linear section;
7 is a flowchart illustrating a threshold voltage change value sensing method of a driving TFT according to an embodiment of the present invention.
8 is a view showing an active section and a vertical blank section;
9 is a view showing a sensing principle of the present invention for sensing a threshold voltage change value of a driving TFT;
10 is a view showing that the time required to sense the threshold voltage change value of the driving TFT in the present invention is reduced compared with the conventional technology.

2 illustrates an organic light emitting display according to an embodiment of the present invention. 3 shows a configuration example of a pixel array and a data driver IC.

2 and 3, an OLED display according to an exemplary embodiment of the present invention includes a display panel 10, a timing controller 11, a data driving circuit 12, a gate driving circuit 13, 16).

A plurality of data lines and sensing lines 14A and 14B and a plurality of gate lines 15 are intersected with each other in the display panel 10 and the pixels P are arranged in a matrix form in each intersection area. The gate lines 15 include a plurality of first gate lines 15A to which a scan control signal SCAN is sequentially supplied and a plurality of first gate lines 15A to which a sensing control signal SEN is sequentially supplied And second gate lines 15B.

Each pixel P is connected to any one of the data lines 14A, one of the sensing lines 14B and one of the first gate lines 15A, the second gate lines 15B, Or the like. Each pixel P is connected to the data line 14A in response to a scan control signal SCAN input through the first gate line 15A and a sensing control signal SEN) to the sensing line 14B.

Each of the pixels P is supplied with a high potential drive voltage EVDD and a low potential drive voltage EVSS from a power supply not shown. The pixel P of the present invention may include an OLED and a driving TFT for driving the OLED. The driving TFT may be implemented as a p-type or an n-type. Further, the semiconductor layer of the driving TFT may include amorphous silicon, polysilicon, or an oxide.

Each of the pixels P may operate differently at the time of normal driving for the display image implementation and at the sensing operation for sensing the threshold voltage change value. The sensing operation of the present invention may be performed for a predetermined time during the power-on process or for a predetermined time during the power-off process. In particular, the sensing drive of the present invention can reduce the time required for sensing the threshold voltage change value of the driving TFT by a method described later to a great extent as compared with the related art. Therefore, during the real time driving, It is possible to sense the change in the threshold voltage Vth of the transistor DT.

Sensing operation may be performed by one operation of the data driving circuit 12 and the gate driving circuit 13 under the control of the timing controller 11. [

The data driving circuit 12 includes at least one data driver IC (Integrated Circuit) (SDIC). The data driver IC SDIC includes a plurality of digital-to-analog converters (hereinafter referred to as DACs) 121 connected to each data line 14A, a plurality of sensing units 122 connected to each sensing line 14B, A mux portion 123 for selectively connecting the sensing units 122 to an analog-to-digital converter (ADC), and a selection control signal is generated to sequentially turn on the switches SS1 to SSk of the mux portion 123 A shift register 124 may be provided.

The DAC generates a data voltage for sensing under the control of the timing controller 11 during sensing operation and supplies the generated data voltage to the data lines 14A. On the other hand, the DAC can generate the data voltage for image display under the control of the timing controller 11 during normal driving and supply it to the data lines 14A.

Each of the sensing units SU # 1 to SU # k may be connected to the sensing line 14B on a one-to-one basis. Each of the sensing units SU # 1 to # k can supply the reference voltage to the sensing line 14B under the control of the timing controller 11 or supply the sensing voltage charged in the sensing line 14B to the ADC.

The ADC converts the sensing voltage selectively input through the mux 123 to a digital sensing value SD and transmits the digital sensing value SD to the timing controller 11.

The gate drive circuit 13 generates a scan control signal in accordance with the sensing drive and the normal drive under the control of the timing controller 11 and then supplies the scan control signal to the first gate lines 15A in a row sequential manner. The gate drive circuit 13 generates a sensing control signal in accordance with the sensing drive and the normal drive under the control of the timing controller 11, and then supplies the sensing control signal to the second gate lines 15B in a row sequential manner.

The timing controller 11 controls the operation of the data driving circuit 12 based on timing signals such as a vertical synchronizing signal Vsync, a horizontal synchronizing signal Hsync, a dot clock signal DCLK and a data enable signal DE A data control signal DDC for controlling the timing and a gate control signal GDC for controlling the operation timing of the gate drive circuit 13 are generated. The timing controller 11 separates the normal driving and the sensing driving based on a predetermined reference signal (driving power enable signal, vertical synchronizing signal, data enable signal, etc.), and outputs the data control signal DDC and the gate The control signal GDC can be generated. In addition, the timing controller 11 includes related switching control signals CON (including PRE and SAM in Fig. 4) to operate the internal switches of the sensing units SU # 1 to # k in accordance with the normal driving and the sensing driving, Lt; / RTI >

The timing controller 11 can transmit the first compensation data corresponding to the sensing data voltage to the data driving circuit 12 during the sensing operation. Here, the first compensation data reflects a compensation value capable of compensating for a threshold voltage change of the driving TFT sensed in the immediately preceding sensing period. The timing controller 11 can transmit the second compensation data RGB corresponding to the image display data voltage to the data driving circuit 12 during normal driving. Here, the second compensation data (RGB) reflects a compensation value capable of compensating for a threshold voltage change of the driving TFT sensed in the immediately preceding sensing period.

The timing controller 11 derives the threshold voltage change value of the driving TFT based on the digital sensing voltage Vsen transmitted from the data driving circuit 12 at the time of sensing driving and outputs the compensation value stored in the memory 16 as And can be appropriately updated on the basis of the derived threshold voltage change value.

4 shows a detailed configuration of a pixel and a sensing unit according to an embodiment of the present invention. 5 is a waveform diagram sequentially illustrating the threshold voltage change value sensing process of the driving TFT according to the embodiment of the present invention. 6 shows that the threshold voltage change value of the driving TFT appears as a curve slope difference in the TFT linear section.

4, the pixel P of the present invention includes an OLED, a driving TFT (Thin Film Transistor) DT, a storage capacitor Cst, a first switch TFT ST1, and a second switch TFT ST2 .

The OLED includes an anode electrode connected to the source node Ns, a cathode electrode connected to the input terminal of the low potential driving voltage EVSS, and an organic compound layer positioned between the anode electrode and the cathode electrode.

The driving TFT DT controls the amount of current input to the OLED according to the gate-source voltage Vgs. The driving TFT DT has a gate electrode connected to the gate node Ng, a drain electrode connected to the input terminal of the high potential driving voltage EVDD, and a source electrode connected to the source node Ns. The storage capacitor Cst is connected between the gate node Ng and the source node Ns to maintain the gate-source voltage Vgs of the driver TFT DT. The first switch TFT (ST1) applies a sensing data voltage (Vdata) on the data line (14A) to the gate node (Ng) in response to the scan control signal (SCAN). The first switch TFT ST1 has a gate electrode connected to the first gate line 15A, a drain electrode connected to the data line 14A, and a source electrode connected to the gate node Ng. The second switch TFT (ST2) switches the electrical connection between the source node Ns and the sensing line 14B in response to the sensing control signal SEN. The second switch TFT ST2 has a gate electrode connected to the second gate line 15B, a drain electrode connected to the sensing line 14B, and a source electrode connected to the source node Ns.

The sensing unit SU of the present invention may include a reference voltage control switch SW1, a sampling switch SW2, and a sample and hold unit S / H.

The reference voltage control switch SW1 is switched according to the reference voltage control signal PRE to connect the input terminal of the reference voltage Vref to the sensing line 14B. The sampling switch SW2 is switched in accordance with the sampling control signal SAM to connect the sensing line 14B and the sample and hold section S / H. The sample and hold section S / H outputs the source node voltage Vs of the driving TFT DT stored in the line capacitor LCa of the sensing line 14B to the sensing voltage Vsen (Vs) when the sampling switch SW2 is turned on. ), And then transfers it to the ADC. Here, the line capacitor LCa can be replaced with a parasitic capacitor existing in the sensing line 14B.

5 and 6 together with an exemplary configuration of the organic light emitting diode display, the threshold voltage change value sensing process of the OLED display according to the exemplary embodiment of the present invention will be sequentially described below.

The threshold voltage change value sensing process of the present invention may include a programming period T1, a mobility compensation period T2, a sensing period T4, and a sampling period T5 as shown in FIG. The threshold voltage change value sensing process of the present invention may further include a source node initialization period T3 to increase the accuracy of sensing. 5, "T0" can be omitted as a sensing line initializing period for initializing the sensing line 14B to the reference voltage Vref in advance of the programming period T1.

In the programming period T1, both the scan control signal SCAN, the sensing control signal SEN, and the reference voltage control signal PRE are input at the ON level. In the programming period T1, the first switch TFT ST1 is turned on to apply the sensing data voltage Vdata to the gate node Ng of the drive TFT DT, and the second switch TFT ST2 and the reference The voltage control switch SW1 is turned on and the reference voltage Vref is applied to the source node Ns of the driving TFT DT. As a result, the gate-source voltage Vgs of the driving TFT DT is programmed to the first level LV1.

In the mobility compensation period T2, the scan control signal SCAN and the reference voltage control signal PRE are maintained at the ON level, while the sensing control signal SEN is inverted to the OFF level. In the mobility compensation period T2, the first switch TFT ST1 is turned on so that the gate node Ng of the drive TFT DT is held at the sensing data voltage Vdata, and the second switch TFT ST2, The source node Ns of the driving TFT DT is floated. The pixel current flows in the drive TFT DT by the gate-source voltage Vgs of the programmed first level LV1 and the source node voltage Vs of the drive TFT DT rises due to the pixel current . As a result, the gate-source voltage Vgs of the driving TFT DT is changed to the second level LV2, which is lower than the first level LV1 and higher than the threshold voltage of the driving TFT DT, The source-to-source voltage Vgs is lowered by the increase of the gate-source voltage Vs, so that the shift of the drive TFT DT is automatically compensated.

In the source node initialization period T3, the scan control signal SCAN is inverted to the off level, the sensing control signal SEN is inverted to the on level, and the reference voltage control signal PRE is maintained at the on level. The first switch TFT ST1 is turned off to float the gate node Ng of the drive TFT DT and the second switch TFT ST2 and the reference voltage control switch SW1 are turned on, The reference voltage Vref is applied again to the source node Ns of the driving TFT DT. As a result, the source node Ns of the driving TFT DT is initialized to the reference voltage Vref in a state in which the gate-source voltage Vgs of the driving TFT DT is maintained at the second level LV2 . The source node Ns of the driving TFT DT is thus initialized to the reference voltage Vref in order to increase the accuracy of sensing by making the starting voltage of the sensing period T4 equal.

In the sensing period T4, the scan control signal SCAN is maintained at the OFF level, the sensing control signal SEN is maintained at the ON level, and the reference voltage control signal PRE is inverted to the OFF level. The first switch TFT ST1 is turned off so that the gate node Ng of the drive TFT DT is kept in a floating state and the reference voltage control switch SW1 is turned off to turn on the drive TFT The reference voltage Vref applied to the source node Ns of the transistors DT is released. In this state, the pixel current flows in the drive TFT DT by the gate-source voltage Vgs of the second level LV2, and the source node voltage Vs of the drive TFT DT becomes the pixel current . The source node voltage Vs of the driving TFT DT is stored in the line capacitor LCa of the sensing line 14B through the turned-on second switch TFT ST2.

In the sampling period T5, the sensing control signal SEN is inverted to the off level and the sampling control signal SAM is input to the on level. In the sampling period T5, the second switch TFT ST2 is turned off to release the electrical connection between the source node Ns of the drive TFT DT and the sensing line 14B. The sampling control switch SW2 is turned on and the sensing line 14B and the sample and hold portion S / H are connected to each other to thereby control the source node voltage of the driving TFT DT charged in the sensing line 14B Vs are sampled to the sensing voltage Vsen for deriving the threshold voltage change value of the driving TFT DT.

The sensing voltage Vsen is converted into a digital value via the ADC and then transmitted to the timing controller 11. [ The timing controller 11 calculates a change value Vsen of the sensing voltage by comparing the sensing voltage Vsen with a preset reference sensing value Vsen [REF], and outputs the change value Vsen of the sensing voltage as a lead The threshold voltage change value (Vth) of the driver TFT (DT) can be read from the look-up table.

The present invention provides a mobility compensation period T2 before the sensing and sampling periods T4 and T5 to automatically compensate for the mobility change of the driving TFT DT internally before sensing so that the sensing voltage Vsen is driven So that only the change in the threshold voltage of the TFT DT is included. According to the present invention, the difference of the sensing voltage Vsen is represented by the difference of the threshold voltage Vth, and the larger the variation value Vsen of the sensing voltage is, the larger the threshold voltage variation value Vth is. The reason for this is as follows. If the threshold voltage (Vth) characteristics are different even when the mobility characteristics are the same, the curve slopes are different from each other in the TFT linear section in which Vgs is smaller than Vth as shown in FIG. 6, And the voltage value of the TFT linear section is sensed and sampled to reduce the voltage.

Since the present invention internally compensates the mobility change internally, high-speed sensing in the TFT linear section is possible. However, when the high-speed sensing is performed without compensating for the mobility change, the sensing voltage Vsen includes the threshold voltage change as well as the mobility variation, Since the influence is larger, it is impossible to obtain an accurate threshold voltage change value.

7 is a flowchart illustrating a threshold voltage change value sensing method of a driving TFT according to an embodiment of the present invention. Figure 8 shows the active period and the vertical blanking period.

Referring to FIG. 7, since a threshold voltage change value is sensed through high-speed sensing in a TFT linear section, a series of processes for deriving a threshold voltage change value, that is, programming, mobility compensation, And sampling may be performed in the vertical blanking period. That is, according to the present invention, it is possible to sense the threshold voltage change of the driving TFT DT during real-time driving without additionally adding a predetermined time during the power-on process or a predetermined time during the power-off process, have.

Here, as shown in Fig. 8, the vertical blanking period indicates a period of time during which the writing of data for image display is not performed between the active periods for image display. During the vertical blank period, the data enable signal DE continues to be held at the low logic level (L). When the data enable signal DE is at the low logic level (L), the writing of data is stopped.

9 shows the sensing principle of the present invention for sensing a threshold voltage change value of a driving TFT. 10 shows that the time required for sensing the threshold voltage change value of the driving TFT in the present invention is reduced compared with the conventional technique.

The prior art shifts the threshold voltage of the driving TFT to the source follower mode (causing the programmed pixel current to flow to the driving TFT while the gate node is fixed and the source node is floated to converge Vgs to Vth by raising the potential of the source node) 9, the present invention is characterized in that the threshold voltage variation of the driving TFT is changed in the constant current mode method (by flowing the programmed pixel current to the driving TFT in a state in which both the gate node and the source node are floating, Node and source node potential simultaneously). 9,? T represents the time required for sensing, C represents the line capacitance of the sensing line, I represents the programmed pixel current, and? V represents the sensing voltage change value.

In the prior art, in order to detect the source node voltage Vs of the driving TFT DT as the sensing voltage Vsen, the time when the gate-source voltage Vgs of the driving TFT DT reaches the saturation state (ta), it took a long time to sense it and it was impossible to sense in the vertical blank period.

However, as clearly shown in FIG. 10, since the Vgs can be sensed at a predetermined time point (ahead of tb, ta) of the linear section larger than Vth, the time required for sensing is drastically reduced So that sensing in the vertical blank period is enabled.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

10: Display panel 11: Timing controller
12: data driving circuit 13: gate driving circuit
14A: Data line 14B: Sensing line
15: gate line

Claims (6)

A threshold voltage change value sensing method of an organic light emitting display including a plurality of pixels each having an OLED and a driving TFT for controlling an amount of light emission of the OLED,
A programming step of applying a sensing data voltage to a gate node of the driving TFT and applying a reference voltage to a source node of the driving TFT to program a gate-source voltage (Vgs) of the driving TFT to a first level;
Holding the sensing data voltage at the gate node of the driving TFT and floating the source node of the driving TFT to change Vgs of the driving TFT to a second level lower than the first level and higher than the threshold voltage of the driving TFT A mobility compensating step of compensating for a change in mobility of the driving TFT;
The method comprising the steps of: flowing a pixel current to the drive TFT in accordance with Vgs of the second level in a floating state of a gate node of the drive TFT; and before the Vgs of the drive TFT is saturated with a threshold voltage, Sensing a node voltage; And
And a sampling step of sampling the source node voltage of the driving TFT with a sensing voltage for deriving a threshold voltage change value of the driving TFT. The method according to claim 1,
Between the step of compensating the mobility variation of the drive TFT and the step of sensing the source node voltage of the drive TFT,
Further comprising a source node initialization step of floating the gate node of the drive TFT and applying the reference voltage again to the source node of the drive TFT to initialize the source node of the drive TFT while maintaining Vgs of the second level Wherein the threshold voltage change value sensing method comprises the steps of: The method according to claim 1,
Calculating a change value of the sensing voltage by comparing the sensing voltage with a preset reference sensing value and reading the threshold voltage change value of the driving TFT from the lookup table using the change value of the sensing voltage as a lead address, Wherein the threshold voltage change value sensing method comprises the steps of: The method according to claim 1,
The sensing step and the sampling step may comprise:
Wherein a Vgs of the driving TFT is larger than a threshold voltage of the driving TFT and is performed in a linear section of the TFT. 3. The method of claim 2,
Each of the pixels being switched in accordance with a scan control signal to connect a data line to which the data voltage is applied and a gate node of the drive TFT; and a second switch TFT, which is switched according to a sensing control signal, And a storage capacitor connected between the gate node and the source node of the drive TFT,
The sensing unit may include a reference voltage control switch that is switched according to a reference voltage control signal to connect the input terminal of the reference voltage and the sensing line, a sampling switching unit that switches according to a sampling control signal to connect the sensing line and the sample- When a control switch is included,
Wherein the scan control signal is applied at an ON level only in a programming period in which the programming is performed and in a mobility compensation period in which the mobility compensation is performed,
The sensing control signal is applied at an ON level only in the programming period, the source node initialization period in which the source node initialization step is performed, and the sensing period in which the sensing is performed,
Wherein the reference voltage control signal is applied at an ON level only in the programming period, the mobility compensation period, and the source node initialization period,
Wherein the sampling control signal is applied at an on level within a sampling interval during which the sampling is performed. 3. The method of claim 2,
Wherein the programming step, the mobility compensation step, the source node initialization step, the sensing step, and the sampling step are performed in a vertical blanking period;
Wherein the vertical blanking period indicates a period of time during which no data for image display is written, which is located between active periods for displaying an image.
KR1020140115972A 2014-09-02 2014-09-02 Method For Sensing Threshold Voltage Change Value Of Organic Light Emitting Display KR101577907B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
KR1020140115972A KR101577907B1 (en) 2014-09-02 2014-09-02 Method For Sensing Threshold Voltage Change Value Of Organic Light Emitting Display

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
KR1020140115972A KR101577907B1 (en) 2014-09-02 2014-09-02 Method For Sensing Threshold Voltage Change Value Of Organic Light Emitting Display

Publications (1)

Publication Number Publication Date
KR101577907B1 true KR101577907B1 (en) 2015-12-16

Family

ID=55080741

Family Applications (1)

Application Number Title Priority Date Filing Date
KR1020140115972A KR101577907B1 (en) 2014-09-02 2014-09-02 Method For Sensing Threshold Voltage Change Value Of Organic Light Emitting Display

Country Status (1)

Country Link
KR (1) KR101577907B1 (en)

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106373512A (en) * 2016-11-02 2017-02-01 深圳市华星光电技术有限公司 OLED-based sensing circuit and sensing method
CN106782333A (en) * 2017-02-23 2017-05-31 京东方科技集团股份有限公司 The compensation method of OLED pixel and compensation device, display device
KR20170078979A (en) * 2015-12-29 2017-07-10 엘지디스플레이 주식회사 Driving Method Of Organic Light Emitting Display
CN106991969A (en) * 2017-06-09 2017-07-28 京东方科技集团股份有限公司 Display panel, the compensation circuit of pixel and compensation method
WO2019006957A1 (en) * 2017-07-04 2019-01-10 Boe Technology Group Co., Ltd. Oled pixel circuit, and driving method thereof, and display apparatus
US10504405B2 (en) 2016-08-17 2019-12-10 Lg Display Co., Ltd. Display device including reference voltage supply
US10593261B2 (en) 2016-10-25 2020-03-17 Lg Display Co., Ltd. Display device and driving method thereof
CN111429853A (en) * 2020-04-28 2020-07-17 深圳市华星光电半导体显示技术有限公司 Backlight module and display device
WO2021227155A1 (en) * 2020-05-14 2021-11-18 深圳市华星光电半导体显示技术有限公司 Display picture compensation method and apparatus, electronic device, and storage medium
CN116097345A (en) * 2020-08-05 2023-05-09 乐金显示有限公司 Display device and driving method thereof

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20080002226A (en) * 2006-06-30 2008-01-04 엘지.필립스 엘시디 주식회사 El display device
KR20120043302A (en) * 2010-10-26 2012-05-04 엘지디스플레이 주식회사 Organic light emitting diode display device and method for driving the same
KR20140071734A (en) * 2012-12-04 2014-06-12 엘지디스플레이 주식회사 Organic light emitting display device and method for driving theteof
KR20140078419A (en) * 2012-12-17 2014-06-25 엘지디스플레이 주식회사 Organic Light Emitting Display

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20080002226A (en) * 2006-06-30 2008-01-04 엘지.필립스 엘시디 주식회사 El display device
KR20120043302A (en) * 2010-10-26 2012-05-04 엘지디스플레이 주식회사 Organic light emitting diode display device and method for driving the same
KR20140071734A (en) * 2012-12-04 2014-06-12 엘지디스플레이 주식회사 Organic light emitting display device and method for driving theteof
KR20140078419A (en) * 2012-12-17 2014-06-25 엘지디스플레이 주식회사 Organic Light Emitting Display

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR102374752B1 (en) 2015-12-29 2022-03-17 엘지디스플레이 주식회사 Driving Method Of Organic Light Emitting Display
KR20170078979A (en) * 2015-12-29 2017-07-10 엘지디스플레이 주식회사 Driving Method Of Organic Light Emitting Display
US10504405B2 (en) 2016-08-17 2019-12-10 Lg Display Co., Ltd. Display device including reference voltage supply
US10593261B2 (en) 2016-10-25 2020-03-17 Lg Display Co., Ltd. Display device and driving method thereof
CN106373512A (en) * 2016-11-02 2017-02-01 深圳市华星光电技术有限公司 OLED-based sensing circuit and sensing method
CN106373512B (en) * 2016-11-02 2018-05-11 深圳市华星光电技术有限公司 A kind of sensing circuit and method for sensing based on OLED
US10706788B2 (en) 2017-02-23 2020-07-07 Boe Technology Group Co., Ltd. Compensation method and compensation apparatus for OLED pixel and display apparatus
WO2018153032A1 (en) * 2017-02-23 2018-08-30 京东方科技集团股份有限公司 Oled pixel compensation method and apparatus, and display device
CN106782333A (en) * 2017-02-23 2017-05-31 京东方科技集团股份有限公司 The compensation method of OLED pixel and compensation device, display device
EP3637400A4 (en) * 2017-06-09 2021-03-03 BOE Technology Group Co., Ltd. Display panel, pixel compensation circuit and compensation method
CN106991969A (en) * 2017-06-09 2017-07-28 京东方科技集团股份有限公司 Display panel, the compensation circuit of pixel and compensation method
US10762844B2 (en) 2017-06-09 2020-09-01 Boe Technology Group., Ltd. Pixel driving circuit and method for driving the same, display panel and compensation
WO2018223702A1 (en) * 2017-06-09 2018-12-13 京东方科技集团股份有限公司 Display panel, pixel compensation circuit and compensation method
WO2019006957A1 (en) * 2017-07-04 2019-01-10 Boe Technology Group Co., Ltd. Oled pixel circuit, and driving method thereof, and display apparatus
US11114027B2 (en) 2017-07-04 2021-09-07 Boe Technology Group Co., Ltd. OLED pixel circuit, and driving method thereof, and a display apparatus
CN111429853A (en) * 2020-04-28 2020-07-17 深圳市华星光电半导体显示技术有限公司 Backlight module and display device
WO2021217731A1 (en) * 2020-04-28 2021-11-04 深圳市华星光电半导体显示技术有限公司 Backlight module and display device
US11475855B2 (en) 2020-04-28 2022-10-18 Shenzhen China Star Optoelectronics Semiconductor Display Technology Co., Ltd. Backlight module and display device
WO2021227155A1 (en) * 2020-05-14 2021-11-18 深圳市华星光电半导体显示技术有限公司 Display picture compensation method and apparatus, electronic device, and storage medium
CN116097345A (en) * 2020-08-05 2023-05-09 乐金显示有限公司 Display device and driving method thereof

Similar Documents

Publication Publication Date Title
KR102301325B1 (en) Device And Method For Sensing Threshold Voltage Of Driving TFT included in Organic Light Emitting Display
KR101577907B1 (en) Method For Sensing Threshold Voltage Change Value Of Organic Light Emitting Display
TWI639990B (en) Organic light emitting diode display and compensation method of driving characteristics thereof
TWI660337B (en) Electrolulminescent display device and driving method of the same
KR101577909B1 (en) Degradation Sensing Method of Organic Light Emitting Display
KR102633409B1 (en) Electro Luminance Display Device And Sensing Method For Electrical Characteristic Of The Same
KR102081132B1 (en) Organic Light Emitting Display
KR102075920B1 (en) Organic Light Emitting Display And Threshold Voltage Compensation Method Thereof
EP2960894B1 (en) Organic light emitting display for compensating for variations in electrical characteristics of driving element
EP2704131B1 (en) Organic light emitting display and driving method thereof
KR102578715B1 (en) Organic light emitting diode display
KR20150076033A (en) Organic Light Emitting Display and Image Quality Compensation Method Of The Same
KR102348765B1 (en) Degradation Sensing Method For Emitting Device Of Organic Light Emitting Display
KR102408901B1 (en) Organic Light Emitting Display
KR102462834B1 (en) Method for sensing degradation of organic light emitting diode
KR102324660B1 (en) Method For Sensing Threshold Voltage Of Driving TFT included in Organic Light Emitting Display
KR101973752B1 (en) Organic light emitting display device
KR20150114080A (en) Organic Light Emitting Display And Driving Method Thereof
KR102642014B1 (en) Organic Light Emitting Display And Driving Method Of The Same
JP2022104556A (en) Electroluminescent display device
KR20180062523A (en) Organic Light Emitting Display
KR101678276B1 (en) Organic Light Emitting Display
KR20180057285A (en) Driver Integrated Circuit For External Compensation And Display Device Including The Same And Data Calibration Method of The Display Device
KR20220017752A (en) Electroluminescence Display Device
KR102526610B1 (en) Memory Control Device And Method And Organic Light Emitting Display Device Including The Same

Legal Events

Date Code Title Description
E701 Decision to grant or registration of patent right
GRNT Written decision to grant
FPAY Annual fee payment

Payment date: 20181114

Year of fee payment: 4

FPAY Annual fee payment

Payment date: 20191113

Year of fee payment: 5