KR102348764B1 - Organic light emitting display and driving method thereof - Google Patents

Abstract

The present invention relates to an organic light emitting diode display capable of improving image quality and a driving method thereof. In the organic light emitting display device according to the present invention, a display panel is divided into a plurality of display blocks, and scan lines included in each display block The first scan signal of the first high state is sequentially supplied to the , and after a stabilization period of the same time for each scan line, the first scan signal of the second high state is sequentially supplied.

Description

Organic light emitting display device and driving method thereof

The present invention relates to an organic light emitting display device and a driving method thereof, and more particularly, to an organic light emitting display device capable of improving image quality and a driving method thereof.

An image display device that implements various information on a screen is a key technology in the information and communication era, and is developing in the direction of thinner, lighter, portable and high-performance. Accordingly, as a flat panel display capable of reducing the weight and volume, which are disadvantages of a cathode ray tube (CRT), an organic light emitting display device that displays an image by controlling the emission amount of an organic light emitting layer is in the spotlight.

In an organic light emitting diode display, a plurality of sub-pixels are arranged in a matrix to display an image. Here, each sub-pixel includes an organic light emitting diode and a pixel driving circuit including at least a switching thin film transistor (TFT) for independently driving the organic light emitting diode, a storage capacitor, and a driving TFT.

The conventional organic light emitting diode display has a problem in that, even when the same data voltage is supplied to each sub-pixel, a luminance deviation occurs due to a threshold voltage deviation of a driving TFT included in each sub-pixel. To solve this problem, the organic light emitting diode display uses an internal compensation method of compensating for a deviation in threshold voltage of each organic light emitting diode pixel through a compensation circuit formed inside each pixel driving circuit.

In this internal compensation method, a scan signal is simultaneously supplied to each scan line during a compensation period, whereas a scan signal is sequentially supplied to each scan line during a data input period. Accordingly, a time difference between the scan signal supplied during the compensation period and the scan signal supplied to the scan line during the data input period is formed differently for each scan line, so that the compensation value of the threshold voltage is changed. To prevent this, black data is supplied to each sub-pixel between the compensation section and the data input section.

Accordingly, since the conventional organic light emitting diode display supplies black data to each sub-pixel, there is a problem in that the compensation period and the light emission period are reduced by the black data supply period, thereby degrading image quality.

SUMMARY OF THE INVENTION The present invention is to solve the above problems, and the present invention provides an organic light emitting diode display capable of improving image quality and a driving method thereof.

In order to achieve the above object, in an organic light emitting diode display according to the present invention, a display panel is divided into a plurality of display blocks, and a first scan signal of a first high state is sequentially supplied to scan lines included in each display block. Then, after a stabilization period of the same time for each scan line, the first scan signal of the second high state is sequentially supplied.

Since the stabilization section from the compensation section to the data input section of one frame is equally applied to the organic light emitting diode display according to the present invention, the same compensation condition is applied to all sub-pixels, so that the black data input section can be removed. By removing the black data input section, the compensation section time can be further secured. Also, in the present invention, the time difference between the first scan signal supplied during the data input period of the current frame and the first scan signal input during the compensation period of the next frame is equally applied to each scan line. Accordingly, in the present invention, since the light emission period of each horizontal line is the same, it is possible to prevent the luminance deviation for each horizontal line and the luminance deviation between the display blocks from occurring.

1 is a circuit diagram illustrating each sub-pixel of an organic light emitting diode display according to the present invention.
FIG. 2 is a diagram for explaining a driving waveform of each sub-pixel shown in FIG. 1 .
3 is a block diagram illustrating an organic light emitting diode display including sub-pixels illustrated in FIG. 1 .
FIG. 4 is a block diagram illustrating the timing control unit shown in FIG. 3 in detail.
5 is a diagram for explaining a driving method of an organic light emitting diode display according to the present invention.
FIG. 6 is a diagram for explaining a driving waveform of the organic light emitting diode display of FIG. 5 .

Hereinafter, an embodiment according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a circuit diagram illustrating each sub-pixel of an organic light emitting diode display according to the present invention.

1 , each sub-pixel includes a first switching transistor Tr_S1, a second switching transistor Tr_S2 serving as an internal compensation circuit, a driving transistor Tr_D, a storage capacitor Cst, and an organic light emitting diode OLED. be prepared Meanwhile, since the configuration of each sub-pixel is very diverse, the structure of FIG. 1 is only a specific example and is not limited thereto.

The organic light emitting diode OLED operates to emit light according to a driving current formed by the driving transistor Tr_D.

The first switching transistor Tr_S1 supplies the reference voltage Vref supplied through the data line DL to the first node n1 in response to the first scan signal supplied through the scan line SL to the first The node n1 is initialized to the reference voltage Vref. Also, the first switching transistor Tr_S1 is switched so that the data signal supplied through the data line DL is stored as a data voltage in the storage capacitor Cst in response to the first scan signal supplied through the scan line SL. It works.

The driving transistor Tr_D operates so that a driving current flows between the high potential line VDD and the low potential line VSS according to the data voltage stored in the storage capacitor Cst.

The second switching transistor Tr_S2 supplies the initialization voltage VINI supplied to the initialization line IL to the source electrode of the driving transistor Tr_D in response to the second scan signal supplied through the sensing control line SEL. .

As shown in FIG. 2, each sub-pixel includes a compensation period T1, a data input period T2 for applying the data voltage Vdata to the data line DL, and an organic light emitting diode (OLED) during one frame period Fn, as shown in FIG. The driving current is divided into an emission period T3 that compensates the driving current applied to the OLED regardless of the threshold voltage and is driven.

The compensation period T1 includes an initialization period Ti for initializing the first and second nodes n1 and n2 to a specific voltage and a sensing period Ts for sensing the threshold voltage of the driving transistor Tr_D.

In the initialization period Ti, the first scan signal in the first high state is supplied to the scan line SL, and the second scan signal in the high state is supplied to the sensing control line SEL. Accordingly, the first switching transistor Tr_S1 is turned on in response to the first scan signal in the first high state, and the second switching transistor Tr_S2 is turned on in response to the second scan signal in the high state.

The reference voltage Vref from the data line DL is supplied to the first node n1, that is, the gate electrode of the driving transistor Tr_D through the turned-on first switching transistor Tr_S1, and the turned-on second switching transistor The initialization voltage VINI from the sensing control line SEL is supplied to the second node n2, that is, the source electrode of the driving transistor Tr_D through (Tr_S2). Accordingly, during the initialization period Ti, the source electrode of the driving transistor Tr_D is initialized to the initialization voltage VINI. In this case, the difference voltage between the reference voltage Vref supplied through the data line and the initialization voltage VINI is stored in the storage capacitor Cst.

In the sensing period Ts, the first scan signal supplied to the scan line SL maintains the first high state, and the second scan signal of the low state is supplied to the sensing control line SEL. Accordingly, in response to the first scan signal in the high state, the first switching transistor Tr_S1 maintains a turned-on state, and in response to the second scan signal in the low state, the second switching transistor Tr_S2 is turned off.

The first node n1, that is, the gate electrode of the driving transistor Tr_D, maintains the reference voltage Vref through the turned-on first switching transistor Tr_S1, and is initialized through the turned-off second switching transistor Tr_S2 Line IL is floating.

Accordingly, the driving transistor Tr_D is turned off when the current flows in the direction of the source terminal while the drain terminal is floated with the high potential voltage VDD, and the voltage of the source becomes “Vref-Vth”. Here, Vth represents the threshold voltage of the driving transistor Tr_D. At this time, the voltage between the gate and the source of the driving TFT Tr_D is stored in the storage capacitor Cst, and sensing of the threshold voltage Vth of the driving TFT Tr_D is completed.

In the data input period T2 , the first scan signal in the second high state is supplied to the scan line SL, and the second scan signal in the low state is supplied to the sensing line SEL. Accordingly, the first switching transistor Tr_S1 is turned on in response to the first scan signal in the second high state, and the second switching transistor Tr_S2 is turned off in response to the second scan signal in the low state.

The data voltage Vdata from the data line DL is supplied to the first node n1, that is, the gate electrode of the driving transistor Tr_D through the turned-on first switching transistor Tr_S1. At this time, since the second node n2 is separated from the first node n1 by the driving transistor Tr_D in the turned-off state, the potential in the sensing period Ts is almost maintained as it is.

In the light emission period T3 , the driving transistor Tr_D is turned on by the data voltage Vdata transferred to the first node n1 . The turned-on driving transistor Tr_D generates a driving current according to the data signal supplied thereto, and the organic light emitting diode OLED emits light by the driving current.

Meanwhile, before the data input period T2, after a stabilization period Δt for a predetermined time in which the first and second switching transistors Tr_S1 and Tr_S2 are turned off, the first switching transistor Tr_S1 is turned on to provide a data voltage A data input period T2 in which (Vdata) is supplied to the first node n1 may be executed.

As shown in FIG. 3 , the organic light emitting display panel 102 having such sub-pixels is driven by a panel driver including a data driver 104 , a scan driver 106 , and a timing controller 108 .

The light emitting display panel 102 includes a plurality of sub-pixels arranged in a matrix form. As illustrated in FIG. 1 , each sub-pixel P includes first and second switching transistors Tr_S1 and Tr_S2 , a driving transistor Tr_D, a storage capacitor Cst, and an organic light emitting diode OLED.

The light emitting display panel 102 is divided into first to Nth (here, N is a natural number greater than 1) display blocks DB1 to DBN in units of i (here, i is a natural number greater than 1) horizontal lines. .

The timing controller 108 includes a control signal generator 110 , a memory controller 112 , and a memory 114 as shown in FIG. 4 .

The control signal generator 110 generates a scan control signal SCS and a data control signal DCS for controlling driving timings of the scan driver 106 and the data driver 104, respectively, based on a synchronization signal input from the outside. do. The generated scan control signal SCS is supplied to the scan driver 106 , and the data control signal DCS is supplied to the data driver 104 . In particular, the control signal generating unit 110 generates a scan control signal SCS that allows the first and second scan signals of each display block DB to be sequentially driven in units of horizontal lines to the scan driver 106 . supply

The memory controller 112 controls the reading RD and the writing WR of the block memory BM included in the memory 114 . The memory control unit 112 causes the image data for each display block DB to be stored in the block memory BM, and the image data for each display block DB stored in the block memory BM is transferred to the data driver 104 . to be output as

The memory 114 includes N block memories BM for storing data of one frame so as to correspond to the light emitting display panel 102 driven by being divided into N display blocks DB. Each block memory BM stores pixel data corresponding to each display block DB. In this case, a line memory or a frame memory may be used instead of the block memory BM. Also, the memory 114 may include a smaller number of block memories BM than the number of display blocks DB. In this case, each block memory BM operates by alternately reading RD and writing WD. The memory 114 outputs image data for each display block stored in the block memory BM to the data driver 104 under the control of the memory controller 112 .

The data driver 104 converts the digital pixel data into an analog data voltage using the data control signal DCS and the gamma voltage from the timing controller 110 , and converts the converted analog data voltage into a data line ( DL).

The scan driver 106 transmits a high state first scan signal to the scan lines SL formed in each display block DB of the light emitting display panel 102 in response to the scan control signal SCS from the timing controller 108 . is sequentially supplied, and a high state second scan signal is sequentially supplied to the sensing control line SEL. In particular, the scan driver 106 controls the first scan signal supplied to each scan line SL to have first and second high state times. In this case, the first high state time corresponds to the compensation period T1 as shown in FIG. 2 , and the second high state time shorter than the first high state time corresponds to the data input period T2 .

As shown in FIG. 5, in the organic light emitting display device, the light emitting display panel is divided into a plurality of display blocks each including i horizontal lines, and a compensation period T1 and a data input period T2 are performed in units of each display block. and the light emission period T3 are sequentially driven.

For example, in the present invention, a case in which the light emitting display panel is divided into two display blocks DB1 and DB2 each including three horizontal lines will be described with reference to FIG. 6 .

The first scan signal in the first high state is applied to the scan lines SL1 , SL2 and SL3 of the sub-pixels from the first horizontal line to the third horizontal line included in the first display block DB1 , and the sensing control line SEL1 , SEL2, SEL3) are sequentially supplied with the second scan signal in the high state. Accordingly, the sub-pixels included in the first display block DB1 are sequentially initialized (Ti) in units of horizontal lines, and the threshold voltages are sequentially compensated (Ts). Then, the first scan signal in the second high state is sequentially supplied to the scan lines SL1 , SL2 , and SL3 of the sub-pixels from the first horizontal line to the third horizontal line included in the first display block DB1 . do. Accordingly, the data voltage is sequentially supplied ( T2 ) to each sub-pixel included in the first display block DB1 . In response to data supplied to each sub-pixel included in the first display block DB1 , the organic light emitting diode of each sub-pixel sequentially emits light T3 in units of horizontal lines. Meanwhile, the time difference between the first scan signal in the second high state supplied during the data input period of the current frame Fn and the first scan signal input during the compensation period of the next frame Fn+1 is each scan line SL ) is the same for each. Accordingly, the emission period T3 of each sub-pixel included in each display block DB becomes the same.

Then, the first scan signal in the first high state is applied to the scan lines SL4 , SL5 , and SL6 of the sub-pixels from the fourth horizontal line to the sixth horizontal line included in the second display block DB2 , for sensing control. A second scan signal in a high state is sequentially supplied to the lines SEL4, SEL5, and SEL6. Accordingly, the sub-pixels included in the second display block DB2 are sequentially initialized (Ti) in units of horizontal lines, and the threshold voltages are sequentially compensated (Ts). In this case, the first scan signal and the second scan signal in the first high state of the second display block DB2 have different times so as not to overlap the first scan signal in the second high state of the first display block DB1 . is supplied to That is, after the first scan signal of the second high state is supplied to the last horizontal line of the first display block, the first scan signal of the first high state is supplied to the first horizontal line of the second display block.

Then, the first scan signal in the second high state is sequentially supplied to the scan lines SL4 , SL5 , and SL6 of the sub-pixels from the fourth horizontal line to the sixth horizontal line included in the second display block DB2 . do. Accordingly, the data voltage is sequentially supplied ( T2 ) to each sub-pixel included in the second display block DB2 . In response to the data voltage supplied to each sub-pixel included in the second display block DB2 , the organic light emitting diode of each sub-pixel sequentially emits light T3 in units of horizontal lines.

As described above, in the present invention, since the compensation section T1 and the data input section T2 between adjacent display blocks do not overlap, the scan signals supplied to the compensation section T1 and the data input section T2 between adjacent display blocks overlap each other. It is possible to prevent abnormal currents such as overcurrents from occurring.

In addition, in the present invention, since the stabilization period Δt from the compensation period T1 to the data input period T2 of one frame is equally applied, the same compensation condition is applied to all sub-pixels to reduce the black data input period. can be removed By removing the black data input section, the compensation section time can be further secured.

In addition, in the present invention, the time difference between the first scan signal supplied during the data input period of the current frame and the first scan signal input during the compensation period of the next frame is equally applied to each scan line. Accordingly, in the present invention, the light emission period of each horizontal line becomes the same. In particular, the emission period of the sub-pixel of the last horizontal line of the i-th display block is equal to the emission period of the sub-pixel of the first horizontal line of the i+1-th display block. Accordingly, it is possible to prevent a luminance deviation for each horizontal line and a luminance deviation between each display block from occurring.

The above description is merely illustrative of the present invention, and various modifications may be made by those of ordinary skill in the art to which the present invention pertains without departing from the technical spirit of the present invention. Therefore, the embodiments disclosed in the specification of the present invention do not limit the present invention. The scope of the present invention should be construed by the following claims, and all technologies within the scope equivalent thereto should be construed as being included in the scope of the present invention.

104: data driver 106: scan driver
108: timing controller 102: light emitting display panel

Claims (6)

a display panel divided into a plurality of display blocks, each display block including a plurality of sub-pixels;
A first scan signal of a first high state is sequentially supplied to scan lines included in each display block during a compensation period of one frame, and scan lines included in each display block during a data input period of one frame and a scan driver sequentially supplying a first scan signal of a second high state to the
A stabilization period of the same time is positioned between the first scan signal of the first high state and the first scan signal of the second high state supplied to each scan line;
During the stabilization period, the first switching transistor included in the plurality of sub-pixels is turned off. The method of claim 1,
The scan driver includes the first scan signal of the second high state supplied to the data input section of the i-th display block (where i is a natural number) among the plurality of display blocks, and the i+1-th display block. An organic light emitting diode display for supplying the first scan signal of the first high state supplied to the compensation period at different times. 3. The method of claim 2,
After the first scan signal of the second high state is supplied to the last horizontal line of the i-th display block, the scan driver generates the first high-state signal on the first horizontal line of the i+1th display block. An organic light emitting diode display for supplying a first scan signal. The method of claim 1,
The scan driver supplies a first scan signal in a low state to scan lines of each display block and a second scan signal in a low state to sensing control lines during the stabilization period. A method of driving an organic light emitting diode display including a display panel divided into a plurality of display blocks and including a plurality of sub-pixels for each display block, the method comprising:
sequentially supplying a first scan signal of a first high state to scan lines included in each of the display blocks during a compensation period of one frame;
sequentially supplying a first scan signal of a second high state to scan lines included in each of the display blocks during the data input period of the one frame;
supplying a data signal to the data lines included in each of the display blocks in response to the first scan signal of the second high state;
and sequentially emitting light from the organic light emitting diodes of the respective display blocks,
A stabilization period of the same time is positioned between the first scan signal of the first high state and the first scan signal of the second high state supplied to each scan line;
During the stabilization period, the first switching transistor included in the plurality of sub-pixels is turned off. 6. The method of claim 5,
After the first scan signal of the second high state is supplied to the last horizontal line of the i-th display block (here, i is a natural number) among the plurality of display blocks, the first horizontal line of the i+1-th display block A method of driving an organic light emitting diode display for supplying the first scan signal of the first high state to a line.

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