KR102135934B1 - Organic Light Emitting Display And Driving Method Thereof - Google Patents

Abstract

The present invention displays an image including an organic light-emitting diode and a driving TFT, respectively, and a plurality of pixels for compensating the threshold voltage and electron mobility of the driving TFT are formed according to a source follower internal compensation method, and the pixels are used to form a plurality of pixels. A display panel formed of pixel lines, and divided into a plurality of display blocks along the data scan direction by the pixel lines grouped by a predetermined number; A gate driving circuit for driving the gate signal supply lines formed on the display panel; A data driving circuit for driving the data signal supply lines formed on the display panel; And controlling the operation of the gate driving circuit and the data driving circuit to sequentially compensate the threshold voltage and electron mobility of the driving TFT in units of display blocks. And a timing controller which sequentially compensates the electron mobility of the driving TFT in the pixel line unit in the same display block after compensating for the threshold voltage at the same time.

Description

Organic Light Emitting Display and Driving Method Thereof

The present invention relates to an active matrix type organic light emitting display device and a driving method thereof.

The active matrix type organic light emitting display device includes an organic light emitting diode (hereinafter referred to as “OLED”) that emits light by itself, and has a fast response speed, high light emission efficiency, high brightness, and a wide viewing angle.

The self-luminous device, OLED, includes an anode electrode and 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 (Electron Injection layer, EIL). When a driving voltage is applied to the anode electrode and the cathode electrode, holes passing through the hole transport layer (HTL) and electrons passing through the electron transport layer (ETL) are moved to the emission layer (EML) to form excitons, and as a result, the emission layer (EML) Visible light is generated.

The organic light emitting display device arranges pixels including OLEDs in a matrix form and adjusts the luminance of pixels according to the gradation of video data. Each of the pixels includes a driving thin film transistor (TFT) to control the driving current flowing through the OLED. However, in the organic light emitting display device, there is a problem that a desired gradation cannot be realized due to deviations in the electrical characteristics (threshold voltage, electron mobility) of the driving TFTs between pixels due to process variations, temporal changes, and the like.

In order to solve this, an internal compensation method that compensates for variations in the electrical characteristics (threshold voltage, mobility) of the driving TFT, and an external compensation method that compensates outside the pixel are known.

The external compensation method senses the deviation of the electrical characteristics of the driving TFT for each pixel and corrects the input data according to the sensed value.It takes a lot of time for sensing, making real-time compensation difficult during driving, and separately related to sensing and data correction. Circuit components (sensing circuit, memory, correction circuit, etc.) are additionally derived, resulting in high manufacturing costs.

The internal compensation method is to set the voltage between the gate and source of the driving TFT regardless of the characteristic deviation in order to compensate in real time for the deviation of the electrical characteristics of the driving TFT during driving, and does not require a separate circuit component as in the external compensation method, but a pixel. The disadvantage is that the structure is complex and the aperture ratio is low.

In order to simplify the pixel structure in the internal compensation method, a technique of setting a voltage between gates and sources of a driving TFT by a source follower method has been proposed. The source follower internal compensation method adopts the principle of raising the source potential toward the gate potential in a state where the gate potential of the driving TFT is kept constant in order to compensate for variations in the electrical characteristics of the driving TFT.

In the source follower internal compensation method, both threshold voltage compensation and pixel data write & electronic mobility compensation must be performed during a predetermined period (eg, one horizontal period) allocated to each pixel line. However, in the case of targeting an amorphous silicon-based or oxide semiconductor-based TFT having low mobility, the threshold voltage cannot be sufficiently compensated within the predetermined period, making it difficult to implement a source follower internal compensation scheme. Because, to compensate for the threshold voltage, the source potential of the driving TFT rises due to the drain-to-source current of the driving TFT. When targeting a low mobility TFT, the source potential of the driving TFT is slow because the current between the drain and source is small. This is because it rises and as a result, the source potential does not reach a desired level (ie, gate potential-threshold voltage) during the predetermined period. When the threshold voltage compensation is terminated in a state in which the source potential of the driving TFT has not risen to a desired level, compensation performance deteriorates.

Since one horizontal period for driving one pixel line is one frame period/number of pixel lines (resolution), as the number of pixel lines increases or one frame period decreases, one horizontal period becomes shorter, and as a result, compensation performance as described above. The degree of degradation is intensified as the resolution of the display panel increases or the frame frequency indicating the number of frames per second increases.

Accordingly, an object of the present invention is to provide an organic light emitting display device capable of sufficiently increasing the compensation performance by sufficiently securing a threshold voltage compensation period when compensating for the deviation of the electrical characteristics of the driving TFT by using the source follower internal compensation method.

In order to achieve the above object, an organic light emitting display device according to an embodiment of the present invention displays an image including an organic light emitting diode and a driving TFT, respectively, and threshold voltage and electron mobility of the driving TFT according to a source follower internal compensation method. A display panel in which a plurality of pixels compensating for are formed, a plurality of pixel lines are formed by the pixels, and divided into a plurality of display blocks along a data scan direction by the pixel lines grouped by a predetermined number; A gate driving circuit for driving the gate signal supply lines formed on the display panel; A data driving circuit for driving the data signal supply lines formed on the display panel; And controlling the operation of the gate driving circuit and the data driving circuit, sequentially compensating the threshold voltage and electron mobility of the driving TFT in units of display blocks, and targeting all pixel lines belonging to the same display block. And a timing controller which sequentially compensates the threshold voltage at the same time, and sequentially compensates the electron mobility of the driving TFT in the same display block in units of pixel lines.

In the present invention, when compensating for the deviation of the electrical characteristics of the driving TFT by using the source follower internal compensation method, the threshold voltage and electron mobility of the driving TFT are sequentially compensated in units of display blocks, but all pixel lines belonging to the same display block are targeted. After simultaneously compensating the threshold voltage of the driving TFT, by sequentially compensating the electron mobility of the driving TFT in the same display block in units of pixel lines, a sufficient compensation period can be secured by sufficiently securing a threshold voltage compensation period within one frame period. have.

1 is a view showing an organic light emitting display device according to an exemplary embodiment of the present invention.
FIG. 2 is a view showing a pixel array formed on the display panel of FIG. 1.
FIG. 3 is a view showing a driving method of the present invention for sufficiently securing a threshold voltage compensation period when compensating for deviation in electrical characteristics of a driving TFT according to a source follower internal compensation method.
4 and 6 are views showing a driving method in which the compensation of the electrical characteristics of the driving TFT is compensated by the method of FIG. 3, but a compensation operation is performed non-overlapping between neighboring display blocks.
5 and 7 are views showing a driving method in which the compensation of the electrical characteristics of the driving TFT is compensated by the method of FIG. 3, but a compensation operation is performed overlapping between adjacent display blocks.
8 is a view showing one equivalent circuit of a pixel according to the present invention.
FIG. 9 is a data pixel and gate signal for driving pixels of some pixel lines belonging to two neighboring display blocks when targeting the pixel as shown in FIG. 8 and a specific pixel line within one frame period. A diagram showing the gate potential and source potential changes of a Korean driving TFT.
10A to 10D are views sequentially showing an operation state of the pixel of FIG. 8 included in a specific pixel line.
11 is a view showing that a floating period varies for each pixel line in the same display block.
12 is a view showing that the source potential of the driving TFT increases due to leakage current during the floating period.
13 is a view showing a method for solving a problem caused by a deviation of a floating period for each pixel line.
14 and 15 are diagrams showing one method for solving a problem caused by a deviation of a floating period for each pixel line.
16 and 18 are diagrams showing one method for improving compensation performance by excluding the effect of the previous stage pixel line.
17 and 19 are views showing another method for improving compensation performance by excluding the effect of the previous stage pixel line.
20 is a view showing an example in which the threshold voltage compensation rate decreases due to the influence of parasitic capacitance.
21 and 22 are diagrams showing one method for preventing a decrease in the threshold voltage compensation rate.
FIG. 23 is a view showing a driving waveform in which the methods of FIGS. 13 and 16 are applied in combination.
FIG. 24 is a view showing a driving waveform in which the methods of FIGS. 13, 17, and 21 are applied in combination.
25 is a view showing another equivalent circuit of pixels according to the present invention.
FIG. 26 is a data pixel and gate signal for driving pixels of some pixel lines belonging to two neighboring display blocks when targeting the same pixel as in FIG. 25, and a specific pixel line within one frame period. A diagram showing the gate potential and source potential changes of a Korean driving TFT.
FIG. 27 is a diagram illustrating a method for solving a problem caused by a variation in a floating period for each pixel line when targeting the pixel as shown in FIG. 25.
28 is a view showing one method for additionally preventing a decrease in the threshold voltage compensation rate based on the method presented in FIG. 27;

Hereinafter, preferred embodiments of the present invention will be described with reference to FIGS. 1 to 28.

1 shows an organic light emitting display device according to an exemplary embodiment of the present invention, and FIG. 2 shows a pixel array formed on the display panel of FIG. 1.

1 and 2, an organic light emitting display device according to an exemplary embodiment of the present invention includes a display panel 10, a data driving circuit 12, a gate driving circuit 13, and a timing controller 11. .

A plurality of data signal supply lines 14 and a plurality of gate signal supply lines 16 are intersected on the display panel 10, and pixels PIX are arranged in a matrix form for each intersection area. Each of the pixels PIX includes an organic light emitting diode and a driving TFT, and compensates a threshold voltage and electron mobility of the driving TFT according to a source follower internal compensation method, and the gate-source voltage of the driving TFT set during the compensation. Is maintained for about 1 frame period to indicate a desired gradation. The pixel PIX of the present invention may be any structure as long as the source follower internal compensation scheme can be applied. Each pixel PIX may include at least one switch TFT that is switched to control the gate potential of the driving TFT. In each pixel PIX, the source potential of the driving TFT may be controlled through the switching of the switch TFT, or in some cases, by the swing of the high potential pixel driving voltage. Switch TFTs of each pixel PIX are switched by a gate signal applied from the gate signal supply lines 16. Each pixel PIX may be connected to any one of one to three gate signal supply lines according to its internal configuration, and may be further connected to more gate signal supply lines. Each pixel PIX may be supplied with a high potential pixel driving voltage EVDD and a low potential pixel driving voltage EVSS from a power generator (not shown).

A pixel array as shown in FIG. 2 is formed on the display panel 10 by pixels PIX arranged in a matrix form. The pixel array is divided into a plurality of display blocks BLK1 to BLKj along a data scan direction (for example, a vertical direction), and each display block may include a plurality of pixel lines L#1 to L#n. have. Here, the pixel line means a set of pixels PIX arranged on the same horizontal line and simultaneously receiving pixel data. The number of pixel lines L#1 to L#n included in each display block may be set to an appropriate number to ensure a sufficient threshold voltage compensation period.

The data driving circuit 12 drives the data signal supply lines 14 under the control of the timing controller 11. The data driving circuit 12 generates a data voltage corresponding to the pixel data DATA according to the data timing control signal DDC applied from the timing controller 11 and supplies it to the data signal supply lines 14. The data voltage refers to a gradation voltage for image display, and in some cases, it may be applied in a multi-step form including an gradation voltage for image display and an offset voltage and/or a precharge voltage.

The gate driving circuit 13 drives the gate signal supply lines 15 under the control of the timing controller 11. The gate driving circuit 13 generates gate signals according to the gate timing control signal GDC from the timing controller 11 to provide gate signal supply lines 15 allocated to each of the pixel lines L#1 to L#n. ). The gate signal supplied to the gate signal supply lines 15 of one pixel line includes a gate potential control gate signal (WS1 in FIG. 8, WS1 and WS3 in FIG. 25) used to control the gate potential of the driving TFT, It may include a gate signal for controlling the source potential (WS2 in FIG. 8, WS2 in FIG. 25) used to control the source potential of the driving TFT. The gate driving circuit 13 may be directly formed on the display panel 10 according to a gate-driver in panel (GIP) method.

The timing controller 11 operates the data driving circuit 12 based on timing signals such as a vertical sync signal Vsync, a horizontal sync signal Hsync, a dot clock signal DCLK, and a data enable signal DE. A data timing control signal (DDC) for controlling timing and a gate timing control signal (GDC) for controlling the operation timing of the gate driving circuit 13 are generated. Further, the timing controller 11 appropriately processes pixel data DATA applied from an external video source (not shown) and supplies it to the data driving circuit 12.

The timing controller 11 controls the operation of the data driving circuit 12 and the gate driving circuit 13 to sequentially compensate the threshold voltage and electron mobility of the driving TFT in units of display blocks, but all belong to the same display block. After compensating for the threshold voltages of the driving TFTs for the pixel lines L#1 to L#n at the same time, by sequentially compensating the electron mobility of the driving TFTs in the same display block in units of pixel lines, one frame period The threshold voltage compensation period is sufficiently secured to improve compensation performance. Unlike the prior art, the present invention allocates the time allocated to the threshold voltage compensation for each display block at the same time to simultaneously compensate for the threshold voltage in one display block, and then moves the electron mobility through data writing according to the line sequential method in the display block. Perform compensation. Here, the time allocated to the threshold voltage compensation (block compensation time) may be determined according to the number of pixel lines belonging to one display block. The block compensation time may be set to an appropriate size in consideration of both the threshold voltage compensation performance and the floating deviation problem to be described later in FIGS. 11 and 12.

3 shows a driving method of the present invention for sufficiently securing a threshold voltage compensation period when compensating for deviations in electrical characteristics of a driving TFT according to a source follower internal compensation method.

The present invention divides the display panel 10 into a plurality of display blocks BLK1 to BLKj each including a plurality of pixel lines L#1 to L#n. (S10)

Subsequently, the present invention sequentially compensates the threshold voltage and electron mobility of the driving TFT in units of display blocks, but threshold voltages of the driving TFTs for all pixel lines L#1 to L#n belonging to the same display block. Rewards simultaneously (S20).

Subsequently, the present invention sequentially compensates the electron mobility of the driving TFT in the same display block in units of pixel lines (S30).

Subsequently, the present invention applies the driving current determined by the voltage between the gate and source of the driving TFT set during compensation to the organic light emitting diodes of each pixel PIX to emit the organic light emitting diodes to realize image gradation. (S40 )

4 and 6 show a driving method in which the compensation of the electrical characteristics of the driving TFT is compensated by the method of FIG. 3, but the compensation operation is performed non-overlapping between neighboring display blocks.

4 and 6, the display blocks BLK1 to BLKj may perform compensation operations non-overlapping with each other.

The non-overlapping compensation operation is explained as follows.

The present invention simultaneously compensates the threshold voltages of the driving TFTs for the pixel lines L#1 to L#n of the first display block BLK1, and then in the pixel line unit in the first display block BLK1. The electron mobility of the driving TFT is sequentially compensated.

Subsequently, the present invention simultaneously compensates the threshold voltage of the driving TFT for the pixel lines L#1 to L#n of the second display block BLK2, and then the pixel line in the second display block BLK2 The electron mobility of the driving TFT is sequentially compensated in units.

In this way, the present invention compensates the threshold voltage and electron mobility of the driving TFT up to the jth display block BLKj.

In FIG. 6, in each display block, a period during which the threshold voltage of the driving TFT is simultaneously compensated is indicated as “D1”, which is the shortest of the floating periods for each pixel line indicating a period from the compensation of the threshold voltage to immediately before writing of pixel data. This is labeled "D2". Since the non-overlapping compensation operation is performed, “D1” of the lower display block is temporally located after writing of pixel data sequentially after “D2” in the neighboring upper display block.

5 and 7 show a driving method in which the compensation of the electrical characteristics of the driving TFT is compensated by the method of FIG. 3, but a compensation operation is performed overlapping between adjacent display blocks.

5 and 7, the display blocks BLK1 to BLKj may perform compensation operations overlapping each other.

The overlapping compensation operation is explained as follows.

The present invention simultaneously compensates the threshold voltage of the driving TFT for the pixel lines L#1 to L#n of the first display block BLK1, and then the pixel lines L of the second display block BLK2 The threshold voltage of the driving TFT is simultaneously compensated for #1 to L#n).

Subsequently, the present invention sequentially compensates the electron mobility in units of pixel lines in the first display block BLK1 in which the threshold voltage of the driving TFT is simultaneously compensated, and then the second display block in which the threshold voltage of the driving TFT is simultaneously compensated ( BLK2) sequentially compensates the electron mobility of the driving TFT in units of pixel lines.

In this way, the present invention compensates the threshold voltage and electron mobility of the driving TFT up to the jth display block BLKj.

In FIG. 7, in each display block, a period during which the threshold voltage of the driving TFT is simultaneously compensated is indicated as “D1”, and the shortest of the floating periods for each pixel line indicating a period from the compensation of the threshold voltage to immediately before writing of pixel data. This is labeled "D2". Since the overlapping compensation operation is performed, “D1” of the lower display block may be temporally positioned to overlap with “D2” of the neighboring upper display block.

8 shows an equivalent circuit of a pixel according to the present invention.

Referring to FIG. 8, the pixel PIX of the present invention includes an organic light emitting diode (OLED), a driving TFT (DT), a storage capacitor (Cst), a first switch TFT (ST1), and a second switch TFT (ST2). It can contain. The TFTs constituting the pixel PIX may be anything as long as they can operate in a source follower internal compensation method. The semiconductor layer constituting the TFT may include amorphous silicon, polysilicon, or oxide.

The organic light emitting diode OLED includes an anode electrode connected to the source node N2, a cathode electrode connected to the low potential pixel driving voltage terminal EVSS, and an organic compound layer positioned between the anode electrode and the cathode electrode.

The driving TFT DT controls the driving current Ioled flowing through the organic light emitting diode OLED according to the gate-source voltage Vgs. The driving TFT DT includes a gate electrode connected to the gate node N1, a drain electrode connected to the high potential pixel driving voltage terminal EVDD, and a source electrode connected to the source node N2.

The storage capacitor Cst is connected between the gate node N1 and the source node N2.

The first switch TFT ST1 is switched according to the gate potential control gate signal WS1 to control the gate potential (the potential of the gate node N1) of the driving TFT DT. The first switch TFT ST1 includes a gate electrode connected to the first gate signal supply line 15A, a drain electrode connected to the data signal supply line 14, and a source electrode connected to the gate node N1. .

The second switch TFT ST2 is switched according to the source potential control gate signal WS2 to control the source potential (the source node N2 potential) of the driving TFT DT. The gate electrode of the second switch TFT (ST2) is connected to the second gate signal supply line (15B), the drain electrode of the second switch TFT (ST2) is connected to the source node (N2), the second switch TFT (ST2 The source electrode of) is connected to the input terminal of the initialization voltage Vinit. Here, the initialization voltage Vinit may be supplied from the data driving circuit 12 or may be supplied from a separate power supply circuit (not shown).

FIG. 9 is a data pixel and gate signal for driving pixels of some pixel lines belonging to two neighboring display blocks when targeting the pixel as shown in FIG. 8 and a specific pixel line within one frame period. It shows the change of gate potential and source potential of the Korean driving TFT. In addition, FIGS. 10A to 10D sequentially show an operating state of the pixel of FIG. 8 included in a specific pixel line.

Referring to FIG. 9, some driving signals for neighboring i-th display blocks BLKi and j-th display blocks BLKj are shown. Referring to the i-th display block BLKi, gate signals WS1 i(n-2) for gate potential control for three pixel lines L#n-2,L#n-1,L#n ), WS1 i(n-1), WS1 i(n)) are applied in the form of a multi-pulse including a first pulse P1 and a second pulse P2, respectively, and three pixel lines L#n Source potential control gate signals (WS2 i(n-2), WS2 i(n-1), WS2 i(n)) for -2,L#n-1,L#n) are each in the form of a single pulse. Is authorized. The first pulses P1 of the gate potential control gate signals WS1 i(n-2), WS1 i(n-1), and WS1 i(n) are simultaneously applied to each other, and the source potential control gate signals WS2 i(n-2), WS2 i(n-1), and WS2 i(n)) are applied simultaneously to each other. On the other hand, the second pulses P2 of the gate signals WS1 i(n-2), WS1 i(n-1), and WS1 i(n) for gate potential control are sequentially applied in a line sequential manner.

In this case, the data signal supply line is offset to the first pulses P1 of the gate potential control gate signals WS1 i(n-2), WS1 i(n-1), and WS1 i(n). The voltage Vofs is applied, and data is sequentially corresponding to the second pulses P2 of the gate signals WS1 i(n-2), WS1 i(n-1), and WS1 i(n) for gate potential control. The gradation voltage (Vdata) for image display is applied to the signal supply line.

Referring to FIGS. 10A to 10D along with FIG. 9, an operation state of the pixel PIX of FIG. 8 included in the n-th pixel line L#n is sequentially described as follows.

The pixel driving of the present invention proceeds in the order of the initialization period TP1, the threshold voltage compensation period TP2, the electron mobility compensation period TP3, and the light emission period TP4 as shown in FIG. 9.

In the initialization period TP1 of FIG. 10A, the first switch TFT ST1 is switched on according to the first pulse P1 of the gate signal WS1 for gate potential control to apply the offset voltage Vofs to the gate node N1. The second switch TFT ST2 is switched on according to the source potential control gate signal WS2 to apply an initialization voltage Vinit to the source node N2. Here, the offset voltage Vofs is set higher than the threshold voltage compared to the initialization voltage Vinit. Therefore, the driving TFT DT is turned on because the voltage between the gate and the source is higher than the threshold voltage.

Subsequently, the gate potential VN1 of the driving TFT DT is maintained at the offset voltage Vofs by the first switch TFT ST1 maintained in the on-switching state during the threshold voltage compensation period TP2 of FIG. 10B. At this time, the second switch TFT ST2 is switched off according to the gate signal WS2 for source potential control, and as a result, the source potential VN2 of the driving TFT DT is the current flowing between the drain-source of the driving TFT DT. It gradually increases from the initialization voltage Vinit by (Ids), but rises until the voltage between the gate and source of the driving TFT DT becomes the threshold voltage Vth. The threshold voltage Vth of the driving TFT DT thus compensated is stored in the storage capacitor Cst. According to the present invention, the threshold voltage compensation period TP2 can be sufficiently secured within one frame period through simultaneous compensation for each block, thereby improving the accuracy of compensation for the threshold voltage.

Subsequently, in the electron mobility compensation period TP3 of FIG. 10C, after a predetermined floating period, the first switch TFT ST1 is switched on according to the second pulse P2 of the gate potential control gate signal WS1. The gradation voltage Vdata for image display is applied to the gate node N1 to increase the gate potential VN1 of the driving TFT DT. Then, the source potential VN2 of the driving TFT DT is also increased according to the characteristics of the electron mobility of the driving TFT DT. As a result, the storage capacitor Cst has a grayscale voltage Vdata and a threshold voltage Vth for image display. The voltage (Vdata+Vth-ㅿVμ) minus the voltage change amount (ㅿVμ) according to the electron mobility characteristic is stored. Through this, the electron mobility of the driving TFT DT is compensated.

Subsequently, in the light emission period TP4 of FIG. 10D, both the first switch TFT ST1 and the second switch TFT ST2 are switched off, and the driving TFT DT is a storage capacitor (in the electron mobility compensation period TP3) Operated by the voltage level (Vdata + Vth-ㅿ Vμ) stored in Cst, the driving current (Ioled) compensated for the threshold voltage (Vth) and electron mobility (μ) is applied to the organic light emitting diode (OLED).

11 shows that the floating period varies for each pixel line in the same display block. And, Fig. 12 shows that the source potential of the driving TFT increases due to the leakage current during the floating period.

For each pixel line, a floating period exists between a period in which the threshold voltage of the driving TFT is compensated and a period in which the electron mobility of the driving TFT is compensated. Here, the floating period means a period in which both the gate node and the source node of the driving TFT are maintained in a floating state.

However, in the present invention, after the threshold voltages of the driving TFTs are simultaneously compensated for pixel lines belonging to the same display block, the electron mobility of the driving TFTs in the same display block is sequentially compensated in units of pixel lines. The floating period for each line, that is, the period from the threshold voltage compensation until immediately before writing the pixel data is changed.

FIG. 11 shows that the longer the floating period is, the longer the pixel data writes are for the four pixel lines L#n-3, L#n-2, L#n-1, L#n. It is done. 11, gate potential control gate signals WS1 i(n-3), WS1 i(n-2), WS1 i(n-1), and WS1 i(n) and source potential control gate signals WS2 i(n-3), WS2 i(n-2), WS2 i(n-1), and WS2 i(n)) maintain a low level in the floating period of the corresponding pixel line. The floating period is the shortest in the pixel line with the fastest compensation order for the electron mobility of the driving TFT and the longest in the pixel line with the lowest compensation order for the electron mobility of the driving TFT. That is, the floating period is the shortest as FP1 in the pixel line L#n-3 and the longest as FP4 in the pixel line L#n.

12, the source potential VN2 of the driving TFT DT may rise (a rise from A to B) due to the leakage current during the floating period, so if the floating period varies for each pixel line, a threshold corresponding to the deviation The gate-source voltage Vgs of the driving TFT DT set during the voltage compensation period may be changed. In this case, the accuracy of compensation may be deteriorated, and the present invention proposes an additional method to solve this.

13 shows one method for solving a problem caused by a deviation of a floating period for each pixel line.

Referring to FIG. 13, according to the present invention, a black system is used to minimize the difference between the gate-source voltages of the driving TFTs set through threshold voltage compensation between pixel lines in the same display block due to differences in floating periods for each line. The quiet data voltage Vblack can be applied.

Specifically, the present invention overlaps the floating period, sets the black writing period TP5, and applies the black gradation data voltage Vblack to the gate of the driving TFT within the black writing period TP5 to gate the driving TFT- The leakage current flowing through the driving TFT is completely blocked by lowering the source-to-source voltage Vgs much lower than the threshold voltage (Vth, for example, "0V") of the driving TFT. Through this, the present invention suppresses the rise of the source potential VN2 of the driving TFT DT during the floating period, and the gate-source voltage Vgs of the driving TFT DT set in the threshold voltage compensation period TP2 ) Can be prevented from being distorted in the floating period.

14 and 15 show another method for solving the problem caused by the deviation of the floating period for each pixel line.

14 and 15, the present invention minimizes the difference between the gate-source voltages of the driving TFTs set through threshold voltage compensation between pixel lines in the same display block due to the difference in the floating period for each pixel line. In order to do this, the threshold voltage compensation period may be different in units of pixel lines.

Specifically, the present invention sets the period CP in which the threshold voltage of the driving TFT is compensated in the same display block to be increased in proportion to the length of the floating period FP, as shown in FIG. 14, so that the deviation of the floating period FP Can be reduced. That is, the present invention shortens the period (CP) during which the threshold voltage of the driving TFT is compensated for in the pixel line (L#n-3) in which the compensation order for the electron mobility of the driving TFT is fastest, while the electron movement of the driving TFT is shortened. The compensation order for the diagram may be the longest in the pixel line L#n, which is the slowest. The period during which the threshold voltage of the driving TFT is compensated is the shortest as CP1 in the pixel line L#n-3 and the longest as CP4 in the pixel line L#n.

The present invention controls the pulse width of the first pulse P1 with respect to the gate potential control gate signal WS1 for each pixel line in order to adjust the threshold voltage compensation period CP, so that the threshold voltage compensation end point (t01, t02) ,t03,t04).

When the pulse width of the first pulse P1 with respect to the gate potential control gate signal WS1 for each pixel line is controlled as shown in FIG. 15, the deviation of Vgs due to the difference in the floating period is greatly reduced compared to the case where it is not so. do.

On the other hand, in order to accurately compensate the electron mobility in the current stage pixel line and express the desired gradation, it is necessary to prevent the Vgs of the current stage pixel line from being set differently by the gradation voltage for image display supplied to the previous stage pixel line. . The present invention proposes the following additional methods to implement this.

16 and 18 show one method for improving compensation performance by excluding the effect of the previous stage pixel line.

Referring to FIGS. 16 and 18, the present invention is to apply a predetermined level of pre-charge voltage (V) before applying the gradation voltage (Vdata) for image display within the electron mobility compensation period to exclude the effect of the previous stage pixel line. Vpre).

That is, the present invention sets the pulse width of the second pulse P2 of the gate signal WS1 for the gate potential control corresponding to the electron mobility compensation period to approximately 1 horizontal period (1HT), and the second pulse P2 Correspondingly, the data voltage can be applied in two steps including a predetermined level of the precharge voltage Vpre and the image display gradation voltage Vdata. If the pre-charge voltage Vpre is applied prior to the supply of the image display gradation voltage Vdata, even if the gradation voltage Vdata for image display changes significantly in the neighboring pixel lines, the driving TFT corresponding to the current stage pixel line The voltage between the gate and the source (Vgs) is distorted, and the degree of setting is greatly reduced.

17 and 19 show another method for improving compensation performance by excluding the effect of the previous stage pixel line.

17 and 19, the present invention narrows the pulse width of the second pulse P2 of the gate signal WS1 for gate potential control corresponding to the electron mobility compensation period to exclude the influence of the previous stage pixel line. All.

That is, in the present invention, the gradation voltage (Vdata) for image display is applied as one step data voltage to the gate of the driving TFT within a period in which the electron mobility of the driving TFT is compensated, and the second of the gate signal (WS1) for gate potential control is applied. The pulse P2 is applied while the gradation voltage Vdata for image display is being output from the data driving circuit, but the pulse width corresponding to 1/2 or less of the output time OT of the gradation voltage Vdata for image display is applied. You can have it. By doing this, it is possible to obtain an effect similar to the application of the precharge voltage Vpre prior to the supply of the gradation voltage Vdata for image display described above.

20 shows an example in which the threshold voltage compensation rate is reduced due to the influence of parasitic capacitance. 21 and 22 show one method for preventing a decrease in the threshold voltage compensation rate.

A lot of parasitic capacitance is generated in the display panel by signal lines and pixel electrodes overlapping each other with an insulating layer interposed therebetween. This parasitic capacitance causes unwanted side effects, a typical example of which is lowering the threshold voltage compensation rate.

In the change of the source potential VN2 of the driving TFT in Fig. 20, it is assumed that the dotted line has a threshold voltage shift amount of 1 V, and the solid line has a threshold voltage shift amount of 0 V. When the compensation rate difference between the two threshold voltages is determined to be “ㅿVs@t1” at the end point t1 of the threshold voltage compensation period TP2, in principle, the difference value must be maintained until the light emission period TP4, but in practice Is leaked under the influence of parasitic capacitance and is reduced to the original value. That is, "ㅿVgs@t2" corresponding to the voltage difference between the gate and the source at a specific time point t2 within the light emission period TP4 is a predetermined loss amount than "ㅿVs@t1", which is a difference in compensation rate of the threshold voltage. Vh(Loss)".

Accordingly, in order to overcome a decrease in the threshold voltage compensation rate, the present invention is the first pulse P1 of the gate potential control gate signal WS1 as shown in FIG. 21 with the floating section TP2-2 for additional compensation interposed therebetween. By dividing into -1 pulses P1-1 and 1-2 pulses P1-2, the pulse width of the gate potential control gate signal WS1 corresponding to the threshold voltage compensation period TP2-1 is reduced and added. Secure the floating section for compensation (TP2-2).

The present invention increases the threshold voltage compensation rate difference “ㅿVs@t1” by the predetermined amount of loss “ㅿVh(Loss)” through the floating section for additional compensation (TP2-2) secured in advance, at the time t2 The voltage difference between the gate and the source at "#Vgs@t2" is maintained at "#Vs@t1", which is the difference in the compensation rate of the threshold voltage at the time t1.

In other words, it is assumed that the threshold voltage of the driving TFT is first compensated by the first-first pulse P1-1, and the threshold voltage of the driving TFT is second-compensated in the floating period TP2-2 for additional compensation. Can. Meanwhile, the 1-2th pulse P1-2 is generated to correspond to the black writing period TP5 to which the black gradation data voltage Vblack is applied to the gate of the driving TFT.

In FIG. 22, a gate signal for controlling a plurality of gate potentials, including a floating section (TP2-2) for additional compensation, for a k-1 block, a k block, and a k+1 block composed of three pixel lines, respectively. (WS1) is shown.

23 shows a driving waveform in which the methods of FIGS. 13 and 16 are applied in combination.

23, the black writing period TP5 is overlapped with the floating period to solve the problem caused by the deviation of the floating period for each pixel line, and the driving TFT is within the black writing period TP5. The data voltage (Vblack) for gradation may be applied to the gate. In addition, the present invention can apply the pre-charge voltage Vpre before supplying the gradation voltage Vdata for image display in order to exclude the influence of the previous stage pixel line.

24 shows a driving waveform in which the methods of FIGS. 13, 17, and 21 are applied in combination.

24, the black writing period TP5 is overlapped with the floating period to solve the problem caused by the deviation of the floating period for each pixel line, and the driving TFT is within the black writing period TP5. The data voltage (Vblack) for gradation may be applied to the gate. In addition, the present invention can narrow the pulse width of the second pulse P2 of the gate signal WS1 for gate potential control corresponding to the electron mobility compensation period in order to exclude the influence of the previous stage pixel line. In addition, the present invention is to overcome the lowering of the compensation rate of the threshold voltage, the first pulse P1 of the gate potential control gate signal WS1 with the floating section TP2-2 for additional compensation interposed therebetween 1-1 By dividing into pulses P1-1 and 1-2 pulses P1-2, the pulse width of the gate potential control gate signal WS1 corresponding to the threshold voltage compensation period TP2-1 is reduced, and additional compensation is provided. The floating section TP2-2 can be secured.

25 shows another equivalent circuit of a pixel according to the present invention. FIG. 26 is a data pixel and gate signal for driving pixels of some pixel lines belonging to two neighboring display blocks when targeting the pixel as shown in FIG. 25 and a specific pixel line within one frame period. It shows the change of gate potential and source potential of the Korean driving TFT.

The pixel PIX of FIG. 25 differs only in that it further includes a separate third switch TFT ST3 that is switched to supply the offset voltage Vofs, as compared with that described with reference to FIG. 8. Is the same as In order to drive the pixel of FIG. 25, a gate signal WS3 for controlling the gate potential is further required to drive the third switch TFT ST3. The third switch TFT ST3 is switched according to the gate potential control gate signal WS3 to control the gate potential (the potential of the gate node N1) of the driving TFT DT. The third switch TFT ST3 includes a gate electrode connected to the third gate signal supply line 15C, a drain electrode connected to the input terminal of the offset voltage Vofs, and a source electrode connected to the gate node N1. . Here, the offset voltage Vofs in FIG. 25 may be applied from the data driving circuit 12 as in FIG. 8, but may be applied from a separate power supply circuit.

The operation of the pixel PIX in FIG. 25 is substantially the same as described in FIG. 8, and a description thereof will be omitted.

FIG. 27 shows a method for solving a problem caused by a deviation of a floating period for each pixel line when targeting the pixel as shown in FIG. 25. And, FIG. 28 shows one method for additionally preventing a decrease in the threshold voltage compensation rate based on the method presented in FIG. 27.

FIG. 27 applies a data voltage for black gradation to minimize the difference between the gate-source voltages of the driving TFTs set through threshold voltage compensation between pixel lines in the same display block due to the difference in the floating period for each pixel line. By doing, it has substantially the same effect as described above. 28 further reduces the pulse width of the gate signal corresponding to the threshold voltage compensation period to secure a floating section for additional compensation, and has substantially the same effect as described above. Besides, in the case of targeting the pixel PIX of FIG. 25, it is needless to say that various additional compensation schemes described with reference to FIGS. 11 to 24 may be similarly applied.

As described above, the present invention sequentially compensates the threshold voltage and electron mobility of the driving TFT in units of display blocks when compensating for the deviation of the electrical characteristics of the driving TFT by using the source follower internal compensation method, all of which belong to the same display block. After simultaneously compensating the threshold voltage of the driving TFT for the pixel lines, the electron mobility of the driving TFT is sequentially compensated in units of pixels in the same display block, thereby sufficiently securing a threshold voltage compensation period within one frame period. Compensation performance can be improved.

Through the above description, those skilled in the art will appreciate that various changes and modifications are possible without departing from the technical idea of the present 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 determined by the scope of the claims.

10: display panel 11: timing controller
12: data driving circuit 13: gate driving circuit
14: data signal supply lines 15: gate signal supply lines

Claims (26)

An organic light emitting diode and a driving TFT are respectively displayed to display an image, and a plurality of pixels are formed to compensate for the threshold voltage and electron mobility of the driving TFT according to a source follower internal compensation method, and the pixel lines are formed by the pixels. A display panel in which a plurality of display blocks are divided along the data scan direction by the pixel lines grouped by a predetermined number;
A gate driving circuit for driving the gate signal supply lines formed on the display panel;
A data driving circuit for driving the data signal supply lines formed on the display panel; And
By controlling the operation of the gate driving circuit and the data driving circuit, the threshold voltage and electron mobility of the driving TFT are sequentially compensated in units of display blocks, but the threshold of the driving TFT is targeted for all pixel lines belonging to the same display block. An organic light emitting display device comprising a timing controller which compensates voltages simultaneously and sequentially compensates the electron mobility of the driving TFT in the same display block in units of pixel lines. According to claim 1,
The display blocks include a first display block and a second display block that are arranged adjacent to each other and are sequentially and non-overlappingly compensated;
The timing controller,
After the threshold voltage of the driving TFT is simultaneously compensated for the first display block, the electron mobility of the driving TFT is sequentially compensated in units of pixel lines in the first display block, and then
An organic light emitting display device for simultaneously compensating the threshold voltage of the driving TFT for the second display block, and sequentially compensating the electron mobility of the driving TFT in the pixel line unit in the second display block. According to claim 1,
The display blocks include a first display block and a second display block that are arranged adjacent to each other and are sequentially and overlapped to be compensated;
The timing controller,
After simultaneously compensating for the threshold voltage of the driving TFT for the first display block, simultaneously compensating for the threshold voltage of the driving TFT for the second display block, and then
An organic light emitting display device that sequentially compensates the electron mobility of the driving TFT in the pixel line unit in the first display block, and then sequentially compensates the electron mobility of the driving TFT in the pixel line unit in the second display block. . According to claim 1,
For each pixel line of the display blocks, a floating period exists between a period in which the threshold voltage of the driving TFT is compensated and a period in which the electron mobility of the driving TFT is compensated,
The floating period is different for each pixel line in the same display block, but the pixel line having the shortest compensation order for the electron mobility of the driving TFT is the shortest and the pixel line having the lowest compensation order for the electron mobility of the driving TFT. Longest organic light-emitting display. The method of claim 3 or 4,
The period of simultaneously compensating the threshold voltage of the driving TFT for the second display block is the organic light emitting display device overlapping the shortest floating period of the first display block. The method of claim 4,
Due to the difference in the floating period, between the pixel lines in the same display block, the difference between the gate-source voltage of the driving TFT set through threshold voltage compensation is minimized,
The timing controller overlaps the floating period, sets a black writing period, and applies a black gradation data voltage to the gate of the driving TFT within the black writing period to apply the gate-source voltage of the driving TFT to the driving TFT. An organic light emitting display device that blocks leakage current flowing through the driving TFT by lowering it than a threshold voltage. The method of claim 4,
Due to the difference in the floating period, between the pixel lines in the same display block, the difference between the gate-source voltage of the driving TFT set through threshold voltage compensation is minimized,
The timing controller sets a period during which the threshold voltage of the driving TFT is compensated in the same display block to be increased for each pixel line in proportion to the floating period, so that a period during which the threshold voltage of the driving TFT is compensated for the driving TFT The organic light emitting display device having the longest compensation order for the electron mobility of the driver TFT, while the longest compensation order for the electron mobility of the driving TFT is shortest. The method of claim 4,
The timing controller controls the gate potential of the driving TFT through a gate signal applied in a multi-pulse form including a first pulse and a second pulse;
The period during which the threshold voltage of the driving TFT is compensated is determined according to the first pulse of the gate signal, and the period during which the electron mobility of the driving TFT is compensated is determined according to the second pulse of the gate signal. . The method of claim 8,
The timing controller controls organic light emission to control the gate of the driving TFT so that a two-step data voltage including a pre-charge voltage and a gradation voltage for image display is applied to the gate of the driving TFT within a period in which the electron mobility of the driving TFT is compensated. Display device. The method of claim 8,
The timing controller controls the gradation voltage for image display to be applied as one step data voltage to the gate of the driving TFT within a period in which the electron mobility of the driving TFT is compensated;
The second pulse of the gate signal is applied while the gradation voltage for image display is being output from the data driving circuit, and the organic light emission has a pulse width corresponding to 1/2 or less of the output time of the gradation voltage for image display. Display device. The method of claim 10,
The timing controller controls the first pulse of the gate signal to be divided into a 1-1 pulse and a 1-2 pulse with a floating period for additional compensation interposed therebetween;
An organic light emitting display device in which the threshold voltage of the driving TFT is first compensated by the first-first pulse, and the threshold voltage of the driving TFT is secondary compensated in the floating period for additional compensation. The method of claim 11,
The 1-2 pulses are applied within a black writing period overlapping with the floating period,
An organic light emitting display device to which a data voltage for black gradation is applied to the gate of the driving TFT by the first-2 pulse. According to claim 1,
Each of the pixels,
The organic light emitting diode;
It includes a gate electrode connected to a gate node, a source electrode connected to a source node, and a drain electrode connected to an input terminal of a high potential pixel driving voltage, and controls the driving current flowing through the organic light emitting diode according to the voltage between the gate and the source. The driving TFT;
A storage capacitor connected between the gate node and the source node;
A gate electrode connected to a first gate signal supply line to which a gate signal for gate potential control is supplied, a drain electrode connected to a data signal supply line to which a data signal is supplied, and a source electrode connected to the gate node, wherein the gate A first switch TFT switched according to a potential control gate signal to control the potential of the gate node; And
A gate electrode connected to a second gate signal supply line to which a gate signal for source potential control is supplied, a drain electrode connected to an input terminal of an initialization voltage, and a source electrode connected to the source node, the gate signal for source potential control And a second switch TFT that is switched accordingly to control the potential of the source node. The method of claim 13,
Each of the pixels,
A gate electrode connected to a third gate signal supply line to which an additional gate potential control gate signal is supplied, a drain electrode connected to an input terminal of an offset voltage, and a source electrode connected to the gate node, wherein the gate for controlling the additional gate potential is And a third switch TFT that is switched according to a signal to control the potential of the gate node. An organic light emitting diode and a driving TFT are respectively displayed to display an image, and a plurality of pixels are formed to compensate for the threshold voltage and electron mobility of the driving TFT according to a source follower internal compensation method, and the pixel lines are formed by the pixels. In the driving method of the organic light emitting display device having a display panel made of them, a gate driving circuit for driving the gate signal supply lines formed on the display panel, and a data driving circuit for driving the data signal supply lines formed on the display panel,
Dividing a display panel into a plurality of display blocks along a data scan direction by the pixel lines grouped by a predetermined number; And
By controlling the operation of the gate driving circuit and the data driving circuit, the threshold voltage and electron mobility of the driving TFT are sequentially compensated in units of display blocks, but the threshold of the driving TFT is targeted for all pixel lines belonging to the same display block. And simultaneously compensating for voltage and sequentially compensating electron mobility of the driving TFT in the same display block in units of pixel lines. The method of claim 15,
The display blocks include a first display block and a second display block that are arranged adjacent to each other and are sequentially and non-overlappingly compensated;
Compensating the threshold voltage and electron mobility of the driving TFT,
After the threshold voltage of the driving TFT is simultaneously compensated for the first display block, the electron mobility of the driving TFT is sequentially compensated in units of pixel lines in the first display block, and then
A method of driving an organic light emitting display device that simultaneously compensates a threshold voltage of the driving TFT for the second display block, and then sequentially compensates the electron mobility of the driving TFT in the pixel line unit in the second display block. The method of claim 15,
The display blocks include a first display block and a second display block that are arranged adjacent to each other and are sequentially and overlapped to be compensated;
Compensating the threshold voltage and electron mobility of the driving TFT,
After simultaneously compensating for the threshold voltage of the driving TFT for the first display block, simultaneously compensating for the threshold voltage of the driving TFT for the second display block, and then
An organic light emitting display device that sequentially compensates the electron mobility of the driving TFT in the pixel line unit in the first display block, and then sequentially compensates the electron mobility of the driving TFT in the pixel line unit in the second display block. How to drive. The method of claim 15,
For each pixel line of the display blocks, a floating period exists between a period in which the threshold voltage of the driving TFT is compensated and a period in which the electron mobility of the driving TFT is compensated,
The floating period is different for each pixel line in the same display block, but the pixel line having the shortest compensation order for the electron mobility of the driving TFT is the shortest and the pixel line having the lowest compensation order for the electron mobility of the driving TFT. The longest organic light emitting display driving method. The method of claim 17,
The method for simultaneously compensating for the threshold voltage of the driving TFT for the second display block is overlapped with the shortest floating period of the first display block. The method of claim 18,
Due to the difference in the floating period, between the pixel lines in the same display block, the difference between the gate-source voltage of the driving TFT set through threshold voltage compensation is minimized,
Compensating the threshold voltage and electron mobility of the driving TFT overlaps the floating period, sets a black writing period, and applies a black gradation data voltage to the gate of the driving TFT within the black writing period. A method of driving an organic light emitting display device that blocks leakage current flowing through the driving TFT by lowering a gate-source voltage of the driving TFT below a threshold voltage of the driving TFT. The method of claim 18,
Due to the difference in the floating period, between the pixel lines in the same display block, the difference between the gate-source voltage of the driving TFT set through threshold voltage compensation is minimized,
Compensating for the threshold voltage and electron mobility of the driving TFT is set such that a period during which the threshold voltage of the driving TFT is compensated in the same display block is increased for each pixel line in proportion to the floating period, so that the driving TFT The period in which the threshold voltage is compensated is shortest in the pixel line having the fastest compensation order for the electron mobility of the driving TFT, while it is the longest in the pixel line having the longest compensation order for the electron mobility of the driving TFT. Method of driving a light emitting display device. The method of claim 18,
In the step of compensating the threshold voltage and electron mobility of the driving TFT, the gate potential of the driving TFT is controlled by a gate signal applied in a multi-pulse form including a first pulse and a second pulse;
The period during which the threshold voltage of the driving TFT is compensated is determined according to the first pulse of the gate signal, and the period during which the electron mobility of the driving TFT is compensated is determined according to the second pulse of the gate signal. How to drive. The method of claim 22,
In the step of compensating the threshold voltage and electron mobility of the driving TFT, the gate of the driving TFT during the period during which the electron mobility of the driving TFT is compensated includes a predetermined level of pre-charge voltage and gradation voltage for image display. Method of driving an organic light emitting display device to which a step data voltage is applied. The method of claim 22,
In the step of compensating the threshold voltage and electron mobility of the driving TFT, a gray level voltage for image display is applied as a one-step data voltage to the gate of the driving TFT during the period during which the electron mobility of the driving TFT is compensated;
The second pulse of the gate signal is applied while the gradation voltage for image display is being output from the data driving circuit, and the organic light emission has a pulse width corresponding to 1/2 or less of the output time of the gradation voltage for image display. Method of driving the display device. The method of claim 24,
In the step of compensating the threshold voltage and electron mobility of the driving TFT, the first pulse of the gate signal is divided into a 1-1 pulse and a 1-2 pulse with an additional compensation floating period therebetween;
A method of driving an organic light emitting display device in which a threshold voltage of the driving TFT is first compensated by the first-first pulse, and a threshold voltage of the driving TFT is secondary-compensated in the floating period for additional compensation. The method of claim 25,
The 1-2 pulses are applied within a black writing period overlapping with the floating period,
A method of driving an organic light emitting display device to which a data voltage for black gradation is applied to a gate of the driving TFT by the 1-2th pulse.

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