KR102059806B1 - Pixel, display device comprising the same and driving method thereof - Google Patents

Abstract

According to an exemplary embodiment, a display device includes a first capacitor connected between a data line and a first node, a switching transistor connecting a first node and a second node, and a second node connected between a second node and a third node. 2 capacitor, a driving transistor connected to a gate electrode at a third node to control a driving current flowing from the first power supply voltage to the organic light emitting diode, a reference voltage transistor transferring a reference voltage to the first node, and a gate electrode connected to the sensing line And a pixel current detection unit configured to detect a pixel current flowing through the organic light emitting diode by the test signal when the plurality of pixels including the sensing transistors respectively supplying the test signal to the organic light emitting diode are turned on.

Description

Pixel, display device including same and driving method thereof {PIXEL, DISPLAY DEVICE COMPRISING THE SAME AND DRIVING METHOD THEREOF}

The present invention relates to a pixel, a display device including the same, and a driving method thereof, and more particularly, to a pixel including an organic light emitting diode, an active matrix display device including the same, and a driving method thereof.

The organic light emitting diode display uses an organic light emitting diode (OLDE) whose luminance is controlled by a current or a voltage. The organic light emitting diode includes an anode layer and a cathode layer forming an electric field, and an organic light emitting material emitting light by the electric field.

Typically, OLEDs are classified into passive matrix OLEDs (PMOLEDs) and active matrix OLEDs (AMOLEDs) according to a method of driving an organic light emitting diode.

Among them, active matrix OLEDs which are selected and lit for each unit pixel in terms of resolution, contrast, and operation speed have become mainstream. One frame of the active matrix display device includes a scanning period for writing image data and a light emitting period for emitting light according to the written image data.

However, in the organic light emitting diode display, characteristics such as an operating voltage (Vth) and mobility of a driving transistor occur in each pixel due to a process deviation, and the like, and a luminance deviation and an afterimage between pixels occur due to deterioration of the organic light emitting diode. Will occur.

The present invention has been proposed to meet the above-mentioned necessity, and to provide a pixel capable of measuring a pixel current of each pixel to compensate for luminance deviation between pixels, a display device including the same, and a driving method thereof. do.

Technical problems to be achieved in the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above will be clearly understood by those skilled in the art from the following description. Could be.

In order to achieve the above object, a display device according to an exemplary embodiment includes a first capacitor connected between a data line and a first node, a switching transistor connecting a first node and a second node, a second node, and a third node. A second capacitor connected between the nodes, a gate transistor connected to the third node to control a driving current flowing from the first power supply voltage to the organic light emitting diode, a reference voltage transistor transferring a reference voltage to the first node, and sensing A pixel current that detects a pixel current flowing through the organic light emitting diode by the test signal when a plurality of pixels and a sensing transistor each including a sensing transistor for supplying a test signal to the organic light emitting diode are turned on. It includes a detection unit.

When the organic light emitting diode emits light by the driving current in the plurality of pixels, the switching transistor is turned off, the reference voltage transistor is turned on to transfer the reference voltage to the first node, and the gate-on voltage corresponding to each of the plurality of pixels. The data voltage corresponding to the scan signal of may be supplied to the first capacitor.

Each of the plurality of pixels may further include an initialization transistor that is turned on by the initialization signal of the gate-on voltage to transfer the first power supply voltage to the second node.

Each of the plurality of pixels may further include a compensation transistor that is turned on by a compensation control signal of a gate-on voltage to connect the gate electrode of the driving transistor and the anode electrode of the organic light emitting diode.

The sensing transistor may be connected to the data line and supply a test signal applied to the data line to the organic light emitting diode.

The sensing transistor may be connected to a pixel current output line separated from the data line, and may supply a test signal applied to the pixel current output line to the organic light emitting diode.

The pixel current detector may detect the pixel current of the pixel in which light emission is terminated connected to at least one sensing line.

According to an exemplary embodiment, a display device driving method includes a first capacitor connected between a data line and a first node, a switching transistor connecting a first node and a second node, and a connection between a second node and a third node. A second capacitor, a gate electrode connected to the third node to control a driving current flowing from the first power supply voltage to the organic light emitting diode, and turned on by a compensation control signal of the gate-on voltage; A plurality of compensation transistors each comprising a compensation transistor connecting the anode electrode of the organic light emitting diode, a reference voltage transistor transferring a reference voltage to the first node, and a sensing transistor connected to the sense line and supplying a test signal to the organic light emitting diode. A driving method of a display device including a pixel, the compensation transistor When supplying a control signal, and the sensing transistor is turned on, and a sensing step of detecting a pixel current flowing in the organic light emitting diode by the test signal.

In an exemplary embodiment, a pixel includes a first capacitor including one electrode connected to a data line and another electrode connected to a first node, a gate electrode, one electrode connected to a first node, and a second node. A switching transistor including the other electrode, a second capacitor including one electrode connected to the second node and the other electrode connected to the third node, a gate electrode connected to the third node, and one connected to the first power supply voltage. A driving transistor comprising a electrode and a second electrode connected to an anode electrode of the organic light emitting diode, a reference voltage transistor including a gate electrode, one electrode connected to a reference voltage, and the other electrode connected to a first node, and connected to a sensing line A sensing transistor comprising a gate electrode, one electrode connected to the data line, and the other electrode connected to the anode electrode of the organic light emitting diode Including, but according to the sense signal supplied to the sense line, when the sensing transistor is turned on, applies a test signal applied to the data line.

According to another exemplary embodiment, a pixel includes a first capacitor including one electrode connected to a data line and another electrode connected to a first node, a gate electrode, one electrode connected to a first node, and a second node. A switching transistor including the other electrode, a second capacitor including one electrode connected to the second node and the other electrode connected to the third node, a gate electrode connected to the third node, and one connected to the first power supply voltage. A driving transistor comprising a electrode and a second electrode connected to an anode electrode of the organic light emitting diode, a reference voltage transistor including a gate electrode, one electrode connected to a reference voltage, and the other electrode connected to a first node, and connected to a sensing line Sensing including a gate electrode, one electrode connected to the pixel current output line, and the other electrode connected to the anode of the organic light emitting diode Comprising: a register, in accordance with the detection signal supplied to the sense line, when the sensing transistor is turned on to apply the test signal applied to the pixel current output line.

The effects of the pixel, the display device including the same, and a driving method thereof according to the present invention will be described below.

According to at least one of the embodiments of the present invention, the pixel current flowing through the organic light emitting diode can be measured.

According to at least one of the embodiments of the present disclosure, the pixel current may be measured simultaneously with the image display.

Effects obtained in the present invention are not limited to the above-mentioned effects, and other effects not mentioned above may be clearly understood by those skilled in the art from the following description. will be.

1 is a block diagram illustrating a display device according to an exemplary embodiment.
2 is a diagram illustrating a driving method of a display device according to an exemplary embodiment.
3 is a circuit diagram illustrating a pixel according to a first exemplary embodiment of the present invention.
4 is a timing diagram illustrating a method of driving a display device when the display device according to an exemplary embodiment emits light.
5 is a timing diagram illustrating a method of driving a display device when detecting a pixel current of the display device according to an exemplary embodiment.
6 is a timing diagram illustrating a display device driving method when light emission and pixel current sensing of a display device according to an exemplary embodiment are performed within one frame period.
7 is an exemplary view schematically illustrating a light emission or pixel current detection driving sequence of a display device according to an exemplary embodiment.
8 is a circuit diagram illustrating a pixel according to a second exemplary embodiment of the present invention.
9 is a circuit diagram illustrating a pixel according to a third exemplary embodiment of the present invention.
10 is a circuit diagram illustrating a pixel according to a fourth exemplary embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In addition, in various embodiments, components having the same configuration will be representatively described in the first embodiment using the same reference numerals, and in other embodiments, only the configuration different from the first embodiment will be described.

In order to clearly describe the present invention, parts irrelevant to the description are omitted, and like reference numerals designate like elements throughout the specification.

Throughout the specification, when a part is "connected" to another part, it includes not only "directly connected" but also "electrically connected" with another element in between. . In addition, when a part is said to "include" a certain component, this means that it may further include other components, except to exclude other components unless otherwise stated.

1 is a block diagram illustrating a display device according to an exemplary embodiment.

Referring to FIG. 1, the display device includes a display unit 10, a scan driver 20, a data driver 30, a signal controller 40, a power voltage supply unit 50, a compensation control signal unit 70, and an initialization signal unit. 80, a relay signal unit 90, a sensing driver 100, and a pixel current detector 110.

The display unit 10 is a display panel including a plurality of pixels connected to corresponding scan lines among the plurality of scan lines S1 to Sn and corresponding data lines among the plurality of data lines D1 to Dm. Each of the plurality of pixels displays an image corresponding to an image data signal transmitted to the corresponding pixel.

Each of the plurality of pixels included in the display unit 10 is connected to the plurality of scan lines S1 to Sn and the plurality of data lines D1 to Dm and arranged in a substantially matrix form. The plurality of scanning lines S1 to Sn extend substantially in the row direction and are substantially parallel to each other. The plurality of data lines D1 to Dm extend substantially in the column direction and are substantially parallel to each other. Each of the plurality of pixels of the display unit 10 receives a power supply voltage from the power supply voltage supply unit 50, and receives a first driving voltage ELVDD and a second driving voltage ELVSS.

The scan driver 20 is connected to the display unit 10 through the plurality of scan lines S1 to Sn. The scan driver 20 generates a plurality of scan signals capable of activating each pixel of the display unit 10 according to the scan control signal CONT2, and transmits the plurality of scan signals to corresponding scan lines among the plurality of scan lines S1 to Sn.

The scan control signal CONT2 is an operation control signal of the scan driver 20 generated and transmitted by the signal controller 40. The scan control signal CONT2 may include a scan start signal, a clock signal, and the like. The scan start signal is a signal that generates the first scan signal for displaying an image of one frame. The clock signal is a synchronization signal for sequentially applying scan signals to the plurality of scan lines S1 to Sn.

The scan driver 20 generates a plurality of scan signals S [1] to S [n] according to the second driving control signal CONT2. The scan driver 20 may sequentially apply scan signals S [1] to S [n] having gate-on voltages to the plurality of scan lines.

The data driver 30 is connected to each pixel of the display unit 10 through a plurality of data lines D1 to Dm. The data driver 30 receives the image data signal DATA and transmits the image data signal DATA to a corresponding data line among the plurality of data lines D1 to Dm according to the data control signal CONT1.

The data control signal CONT1 is an operation control signal of the data driver 30 generated and transmitted by the signal controller 40.

The data driver 30 selects a gray voltage corresponding to the image data signal DATA and transfers the gray voltage to the plurality of data lines D1 to Dm as data signals.

The data driver 30 samples and holds the input image data signal DATA according to the first driving control signal CONT1, and supplies a plurality of data signals data [1] to each of the plurality of data lines D1 to Dm. pass ~ data [m]). The data driver 30 may include the data signals data [1] ˜ having a predetermined voltage range in the plurality of data lines D 1 ˜ D m in response to the scan signals S [1] ˜ S [n] of the gate-on voltage. data [m]) is applied.

The signal controller 40 receives an input control signal for controlling the image information ImS inputted from the outside and the display thereof. The image information ImS includes luminance information of each pixel of the display unit 10, and the luminance may be divided into a predetermined number, for example, 1024, 256, or 64 gray levels.

Meanwhile, examples of the input control signal transmitted to the signal controller 40 include a vertical sync signal Vsync, a horizontal sync signal Hsync, a main clock MCLK, and a data enable signal DE.

The signal controller 40 may control the first to seventh driving control signals CONT1, CONT2, CONT3, and CONT4 according to the image signal ImS, the horizontal synchronization signal Hsync, the vertical synchronization signal Vsync, and the main clock signal MCLK. , CONT5, CONT6, and CONT7) and the image data signal DATA are generated.

The signal controller 40 appropriately processes the image display signal ImS based on the input image display signal ImS and the input control signal in accordance with operating conditions of the display unit 10 and the data driver 30. In detail, the signal controller 40 may generate an image data signal DATA through an image processing process such as gamma correction and luminance compensation on the image display signal ImS.

For example, the signal controller 40 generates a data control signal CONT1 for controlling the operation of the data driver 30, and transmits the data control signal CONT1 to the data driver 30 together with the image data signal DATA that has been processed. To pass. In addition, the signal controller 40 transmits a scan control signal CONT2 for controlling the operation of the scan driver 20 to the scan driver 20.

In addition, the signal controller 40 may control the driving of the power voltage supply unit 50. The power supply voltage supply unit 50 may supply a power supply voltage for driving each pixel of the display unit 10.

For example, the signal controller 40 may transmit the driving signal CONT3 to the power voltage supply unit 50 to drive the power voltage supply unit 50.

Next, the power supply voltage supply unit 50 is connected to a plurality of power lines, and provides a first power supply voltage ELVDD, a second power supply voltage ELVSS, and a reference voltage Vref to the plurality of power supply lines.

The power supply voltage supply unit 50 may adjust voltage levels of the first power supply voltage ELVDD, the second power supply voltage ELVSS, and the reference voltage Vref according to the third driving control signal CONT3. The first power supply voltage ELVDD and the second power supply voltage ELVSS supply driving voltages required for pixel operation.

The display unit 10 is a display area including a plurality of pixels 60. The display unit 10 includes a plurality of scan lines S1 to Sn extending substantially in the row direction and substantially parallel to each other, a plurality of data lines D1 to Dm extending substantially in the column direction and substantially parallel to each other, and a plurality of power sources. A line, a plurality of compensation control lines, a plurality of initialization lines, a plurality of relay lines, and a plurality of sense lines Sense 1 to Sense m are formed to be connected to the plurality of pixels. The plurality of pixels is arranged approximately in the form of a matrix.

The compensation control signal unit 70 is connected to a plurality of compensation control lines and generates a compensation control signal GC according to the fourth driving control signal CONT4.

The initialization signal unit 80 is connected to the plurality of initialization lines and generates an initialization signal GS according to the fifth driving control signal CONT5.

The relay signal unit 90 is connected to a plurality of relay lines and generates a relay signal GW according to the sixth driving control signal CONT6.

The sensing driver 100 is connected to a plurality of sensing lines and generates sensing signals Sense [1] to Sense [m] according to the seventh driving control signal CONT7.

The pixel current detector 110 may be connected to data lines connected to the pixels to measure pixel currents of each of the plurality of pixels. The pixel current detector 110 may detect a voltage corresponding to the pixel current or the pixel current of each of the plurality of pixels for calculating the optimal driving voltage.

Here, the timing of extracting the degradation information of the organic light emitting diodes of the pixels by the sensing driver 100 and the pixel current detector 110 is not particularly limited, but is performed whenever power is applied to the organic light emitting display, or is initially displayed. The device can be performed before shipping to the product. In addition, although the sensing driver 100 may be automatically operated periodically, the sensing driver 100 may be arbitrarily set by the user.

Next, a driving method of the display device according to an exemplary embodiment will be described with reference to FIG. 2.

2 is a diagram illustrating a driving method of a display device according to an exemplary embodiment.

Referring to FIG. 2, one frame period during which one image is displayed on the display unit 10 includes a reset period 1 of an organic light emitting diode of a pixel, an initialization period 2 of initializing a driving voltage of the organic light emitting diode, and A compensation period 3 for compensating the threshold voltage of the driving transistor, a scan period 4 in which data is written into each of the plurality of pixels, a light emission period 5 in which the plurality of pixels emits light corresponding to the written data, and a plurality of pixels The bias period 6 for improving the response waveform of the. The bias period 6 may be omitted depending on the driving method of the display device.

In time, the scanning period 4 and the light emission period 5 overlap each other. In the light emitting period 5 of the current frame, the pixel emits light in accordance with the data written in the scanning period 4 of the immediately preceding frame. The pixel emits light in the light emission period 5 of the next frame in accordance with the data written in the pixel in the scanning period 4 of the current frame.

For example, assume that the period T1 includes the scanning period 4 and the light emission period 5 of the Nth frame. The data written in the pixels in the scanning period 4 of the period T1 is the data of the Nth frame, and the pixels in the light emitting period 5 of the period T1 are the N− written in the scanning period 4 of the N−1th frame. The light is emitted in accordance with the data of the first frame.

The period T2 includes the scanning period 4 and the light emission period 5 of the N + 1th frame. Data written in the pixels in the scanning period 4 of the period T2 is data of the N + 1th frame, and in the light emitting period 5 of the period T2, the pixels are in the scanning period 4 of the Nth frame, that is, in the period T1. Light is emitted in accordance with the data of the written Nth frame.

The period T3 includes the scanning period 4 and the light emission period 5 of the N + 2th frame. The data written in the pixels in the scanning period 4 of the period T3 is data of the N + 2th frame, and the pixels in the light emitting period 5 of the period T3 are the scanning period 4 of the N + 1th frame, that is, the period. Light is emitted in accordance with the data of the N + 1th frame written in T2.

The period T4 includes the scanning period 4 and the light emission period 5 of the N + 3th frame. Data written in the pixels in the scanning period 4 of the period T4 is data of the N + 3th frame, and in the light emitting period 5 of the period T4, the pixels are in the scanning period 4 of the N + 2th frame, that is, the period. Light is emitted in accordance with the data of the N + 2th frame written in T3.

A pixel structure in which data of the current frame is written in the scanning period 4 and emits light in accordance with the data of the immediately preceding frame in the light emitting period 5 which is a period overlapping with the scanning period 4 will be described with reference to FIG.

3 is a circuit diagram illustrating a pixel according to a first exemplary embodiment of the present invention.

Referring to FIG. 3, a pixel includes a switching transistor Tw, a driving transistor Td, a compensation transistor Tc, an initialization transistor Tsus, a reference voltage transistor Ts, a sensing transistor Tsen, and a first capacitor Chold. ), A second capacitor Cst, and an organic light emitting diode OLED.

The switching transistor Tw includes a gate electrode to which the relay signal GW is applied, one electrode connected to the first node NC, and the other electrode connected to the second node ND. The switching transistor Tw is turned on by the relay signal GW of the gate-on voltage to connect the first node NC and the second node ND.

The driving transistor Td includes a gate electrode connected to the third node NG, one electrode connected to the first power voltage ELVDD, and the other electrode connected to the fourth node NA. The driving transistor Td is turned on and off by the voltage of the third node NG to control the driving current supplied to the organic light emitting diode OLED.

The compensation transistor Tc includes a gate electrode to which the compensation control signal GC is applied, one electrode connected to the third node NG, and the other electrode connected to the fourth node NA. The compensation transistor Tc is turned on by the compensation control signal GC of the gate-on voltage to connect the gate electrode and the other electrode of the driving transistor Td.

The initialization transistor Tsus includes a gate electrode to which the initialization signal GS is applied, one electrode connected to the first power voltage ELVDD, and the other electrode connected to the second node ND. The initialization transistor Tsus is turned on by the initialization signal GS of the gate-on voltage to transfer the first power voltage ELVDD to the second node ND.

The reference voltage transistor Ts includes a gate electrode connected to the scan line, one electrode connected to the reference voltage Vref, and the other electrode connected to the first node NC. The reference voltage transistor Ts is turned on by the scan signal S [i] of the gate-on voltage to transfer the reference voltage Vref to the first node NC (1 ≦ i ≦ n).

The sensing transistor Tsen includes a gate electrode connected to the sensing line, one electrode connected to the fourth node NA, and the other electrode connected to the data line Dj. The sensing transistor Tsen is turned on by the sensing signal Sense [i] of the gate-on voltage to connect the anode electrode of the organic light emitting diode OLED to the data line Dj.

The first capacitor Chold includes one electrode connected to the data line Dj and the other electrode connected to the first node NC (1 ≦ j ≦ m).

The second capacitor Cst includes one electrode connected to the second node ND and the other electrode connected to the third node NG.

The organic light emitting diode OLED includes an anode electrode connected to the fourth node NA and a cathode electrode connected to the second power supply voltage ELVSS. The organic light emitting diode OLED may emit light of one of the primary colors. Examples of the primary colors may include three primary colors of red, green, and blue, and a desired color may be displayed by spatial or temporal sum of these three primary colors.

The switching transistor Tw, the driving transistor Td, the compensation transistor Tc, the initialization transistor Tsus, the reference voltage transistor Ts, and the sensing transistor Tsen may be p-channel field effect transistors. In this case, the gate-on voltage for turning on the switching transistor Tw, the driving transistor Td, the compensation transistor Tc, the initialization transistor Tsus, the reference voltage transistor Ts, and the sensing transistor Tsen is a low level voltage. The gate off voltage to turn off is a high level voltage.

Although a p-channel field effect transistor is shown here, at least any one of a switching transistor Tw, a driving transistor Td, a compensation transistor Tc, an initialization transistor Tsus, a reference voltage transistor Ts, and a sensing transistor Tsen. One may be an n-channel field effect transistor. In this case, the gate-on voltage for turning on the n-channel field effect transistor is a high level voltage, and the gate-off voltage for turning off the n-channel field effect transistor is a low level voltage.

The switching transistor Tw, the driving transistor Td, the compensation transistor Tc, the initialization transistor Tsus, the reference voltage transistor Ts, and the sensing transistor Tsen are amorphous silicon thin film transistors (amorphous-Si TFT), low temperature poly One of a low temperature poly-silicon (LTPS) thin film transistor and an oxide TFT may be provided. The oxide TFT may include oxides such as amorphous indium-galium-zinc-oxide (IGZO), zinc-oxide (ZnO), and titanium oxide (TiO) as an active layer.

Next, a driving method of the display device according to an exemplary embodiment of the present invention will be described with reference to FIGS. 4 to 6.

4 is a timing diagram illustrating a method of driving a display device when the display device according to an exemplary embodiment emits light.

As described above with reference to FIG. 2, each of the reset period IN1, the initialization period IN2, the compensation period IN3, the scanning period IN4, the light emission period IN5, and the bias period IN6 for one frame. First power supply voltage ELVDD, second power supply voltage ELVSS, scan signals S [1] to S [n], compensation control signal GC, relay signal GW, initialization signal GS, and data The signals data [1] to data [m] fluctuate.

In the reset period IN1, the initialization signal GS is applied to the low level voltage and the initialization transistor Tsus is turned on.

At time t11 of the reset period IN1, the first power supply voltage ELVDD changes to a low level voltage, and the first power supply voltage ELVDD of the low level voltage is turned on through the turned-on initialization transistor Tsus. ND).

The voltage of the second node ND becomes a low level voltage, and the voltage of the third node NG is lowered by the coupling by the second capacitor Cst. The voltage of the third node NG becomes a voltage low enough to turn on the driving transistor Td. A current flows from the fourth node NA to the first power voltage ELVDD through the driving transistor Td, thereby lowering the voltage of the fourth node NA.

At the time t12 of the reset period IN1, the compensation control signal GC is applied at a low level voltage and the compensation transistor Tc is turned on. As the compensation transistor Tc is turned on, the third node NG and the fourth node NA are connected, and the voltages of the third node NG and the fourth node NA are the first power voltage ELVDD. The voltage is at a level similar to the low level voltage of. That is, the voltage of the third node NG and the anode voltage of the organic light emitting diode OLED are reset to the low level voltage.

Next, at the time t13 of the initialization period IN2, the first power supply voltage ELVDD changes to a high level voltage. At this time, the compensation transistor Tc is turned on by the compensation control signal GC applied to the low level voltage to diode-connect the driving transistor Td. The voltage of the third node NG becomes ELVDD + Vth.

Here, ELVDD refers to the high level voltage of the first power supply voltage ELVDD, and Vth refers to the threshold voltage of the driving transistor Td. At this time, the initialization signal GS is applied at a low level voltage and the initialization transistor Tsus is turned on. The high level voltage of the first power supply voltage ELVDD is transferred to the second node ND through the turned-on initialization transistor Tsus, and the voltage of the second node ND becomes ELVDD.

Next, at the time t14 of the compensation period IN3, the relay signal GW is applied as the low level voltage, and the initialization signal GS is applied as the high level voltage. As the initialization signal GS is applied to the high level voltage, the initialization transistor Tsus is turned off.

As the relay signal GW is applied to the low level voltage, the switching transistor Tw is turned on and the first node NC and the second node ND are connected. At this time, the data signal data [j] is applied to the sustain voltage Vsus.

The voltage stored in the first capacitor Chold is Vref-Vdata as the voltage stored in the first capacitor Chold in the scan period IN4 of the previous frame of the current frame. Description of this will be described later in the description of the scanning period IN4. Here, Vdata means a voltage of the data signals data [1] to data [m].

As the switching transistor Tw is turned on while the sustain voltage Vsus is applied to the data line Dj, the voltage of the second node ND is changed by the voltage stored in the first capacitor Chold. The voltage Vd of the second node ND is changed as in Equation 1 below.

Where Vd is the voltage of the second node ND, Cth is the capacitance of the second capacitor Cst, Cst is the capacitance of the first capacitor Chold, Cpara is the parasitic capacitance of the driving transistor Td, and Coled is the organic light emission. The parasitic capacitance of the diode OLED.

As the switching transistor Tw is turned on, the voltage Vref-data + Vsus should be transmitted to the second node ND, but the parasitic capacitor Coled of the organic light emitting diode OLED and the parasitic capacitor of the driving transistor Td Since Cpara and the second capacitor Cst are connected in series and the first capacitor Chold is connected thereto, the voltage Vd of the second node ND is applied as shown in Equation 1 below.

At this time, the voltage of the third node NG is continuously applied to ELVDD + Vth, and the voltage of (ELVDD + Vth) -Vd is stored in the second capacitor Cst. That is, since the data voltage of the previous frame is reflected in the voltage Vd of the second node, the voltage reflecting the data voltage of the previous frame is stored in the second capacitor Cst.

At the time t15 of the compensation period IN3, the compensation control signal GC and the relay signal GW are applied at the high level voltage, and the initialization signal GS is applied at the low level voltage. The switching transistor Tw and the compensation transistor Tc are turned off. The initialization transistor Tsus is turned on by the initialization signal GS, and the first power supply voltage ELVDD of the high level voltage is transmitted to the second node ND. As the voltage of the second node ND is changed to ELVDD, the voltage Vg of the third node NG is changed as shown in Equation 2 due to the coupling by the second capacitor Cst.

Here, Vg is the voltage of the third node NG, Cth is the capacitance of the second capacitor Cst, and Cpara is the parasitic capacitance of the driving transistor Td.

In the light emission period 5, the first power supply voltage ELVDD maintains a high level voltage, and the second power supply voltage ELVSS fluctuates to a low level voltage. As the second power supply voltage ELVSS changes to a low level voltage, a current flows through the driving transistor Td to the organic light emitting diode OLED. The driving current I_OLED flowing to the organic light emitting diode OLED is represented by Equation 3 below.

Here, k is a parameter determined according to the characteristics of the driving transistor Td. The organic light emitting diode OLED emits light with a brightness corresponding to the driving current I_OLED. That is, the organic light emitting diode OLED emits light with a brightness corresponding to the data voltage data regardless of the threshold voltage Vth of the driving transistor Td. When the light emission period 5 ends, the second power supply voltage ELVSS is changed to a high level voltage.

In the scan period IN4, the plurality of scan signals S [1] to S [n] are sequentially applied at a low level voltage to turn on the reference voltage transistor Ts, and the plurality of scan signals S [1]. A plurality of data signals data [1] to data [m] are applied in correspondence with]] to S [n].

At this time, the relay signal GW is applied at a high level voltage, and the switching transistor Tw is turned off. When the reference voltage transistor Ts is turned on, the reference voltage Vref is transferred to the first node NC. When the data voltage data is transferred to the data line Dj while the reference voltage Vref is transmitted to the first node NC, the Vref-data voltage is stored in the first capacitor Chold.

After the Vref-data voltage is stored in the first capacitor Chold, when the reference voltage transistor Ts is turned off, the first node NC is in a floating state, and thereafter, even if the voltage of the data line Dj changes, The Vref-data voltage stored in the capacitor Chold is maintained. The Vref-data voltage stored in the first capacitor Chold is used in the light emission period IN5 of the next frame.

In the bias period IN6, the first power supply voltage ELVDD and the second power supply voltage ELVSS are applied at the high level voltage, and the compensation control signal GC is applied at the low level voltage. The compensation transistor Tc is turned on by the compensation control signal GC, and the third node NG and the fourth node NA are connected to each other so that the voltages of the third node NG and the fourth node NA are reduced. Reset to a specific voltage. That is, the gate, source, and drain voltages of the driving transistor Td are applied at specific voltages, and the response waveform of the pixel can be improved. The bias period IN6 can be omitted.

As described above, the proposed pixel can simultaneously secure data writing and light emission, so that the data writing time can be sufficiently secured, which is suitable for large size and high resolution display panels, and the use of two capacitors ensures sufficient aperture ratio.

Since the proposed pixel is driven based on the data line and the reference voltage Vref at the time of data writing, even if the first power supply voltage ELVDD is changed according to the light emission driving, the correct pixel signal is accurate to the first capacitor Chold. Can be entered.

5 is a timing diagram illustrating a method of driving a display device when detecting a pixel current of the display device according to an exemplary embodiment.

At time t21 of the sensing period IN7, the first power supply voltage ELVDD is changed to a low level voltage. At a time t22, the second power supply voltage ELVSS is changed to a low level voltage.

At time t23, the compensation control signal GC is applied at a low level voltage. Then, the compensation transistor Tc is turned on by the compensation control signal GC to diode-connect the driving transistor Td.

At the time t24, the initialization signal GS is applied to the high level voltage. As the initialization signal GS is applied to the high level voltage, the initialization transistor Tsus is turned off.

Next, at time t25, the plurality of sensing signals Sense [1] to Sense [n] are sequentially applied at low level voltages to turn on the sensing transistor Tsen, and the plurality of sensing signals Sense [1]. A plurality of test signals test [1] to test [m] are applied corresponding to Sense [n]).

Then, a voltage corresponding to the test signal is applied to the fourth node NA, and the pixel current is applied to the organic light emitting diode OLED according to the test signal voltages of the both ends of the organic light emitting diode OLED and the second power supply voltage ELVSS. Is generated.

In this case, the pixel current detector 110 detects the pixel current flowing through the data line. On the other hand, since the driving transistor Td is diode-connected, the current flowing from the fourth node NA to the driving transistor Td is very small compared to the pixel current.

When the pixel current is detected once, the display device may change the voltage of the test signal applied for each data line to detect the pixel current of the organic light emitting diode OLED. Alternatively, when detecting a plurality of circuits of the pixel current, the display device may detect the pixel current of the organic light emitting diode OLED by changing the voltage of the test signal every time.

6 is a timing diagram illustrating a display device driving method when light emission and pixel current sensing of a display device according to an exemplary embodiment are performed within one frame period.

As described above with reference to FIG. 4, the display device may sense the pixel current only for some pixels during the second period INS after the light emission is terminated during the first period IND.

When the first period IND ends, the first power supply voltage ELVDD and the second power supply voltage ELVSS are changed to a low level voltage.

The compensation control signal GC is applied at a low level voltage. Then, the compensation transistor Tc is turned on by the compensation control signal GC to diode-connect the driving transistor Td.

Next, the initialization signal GS is applied at a high level voltage. As the initialization signal GS is applied to the high level voltage, the initialization transistor Tsus is turned off.

The plurality of sensing signals Sense [i] to Sense [i + q] corresponding to some pixels are sequentially applied at a low level voltage to turn on the sensing transistor Tsen. Then, a plurality of test signals test [1] to test [m] are applied corresponding to the plurality of sensing signals Sense [i] to Sense [i + q].

Then, a voltage corresponding to the test signal is applied to the fourth node NA, and the pixel current is applied to the organic light emitting diode OLED according to the test signal voltages of the both ends of the organic light emitting diode OLED and the second power supply voltage ELVSS. Is generated. The pixel current detector 110 detects a pixel current corresponding to some pixels flowing in the data line.

Hereinafter, a driving sequence of the display device will be described with reference to FIG. 7.

7 is an exemplary view schematically illustrating a light emission or pixel current detection driving sequence of a display device according to an exemplary embodiment.

As shown in FIG. 7A, after turning on, the display device may apply 7V as a test signal to detect the pixel current. Next, the display device may apply 5V as a test signal to detect the pixel current.

Subsequently, the display device may be driven to display an image on the display unit 10 by using pixel current corresponding to each test signal voltage.

Alternatively, as shown in FIG. 7B, after being turned on, the display device may apply 7V as a test signal to detect the pixel current. Next, the display device may apply 5V as a test signal to detect the pixel current.

Subsequently, the display device is driven to display an image on the display unit 10 using pixel currents corresponding to the respective test signal voltages, but as illustrated in FIG. 6, the pixel current may be partially detected for some pixels. . In this case, an image of the next frame may be displayed by appropriately using the partially detected pixel current.

Alternatively, as shown in FIG. 7C, after being turned on, the display device may display an image on the display unit 10, but partially detect the pixel current for some pixels. In this case, the display device may display an image of a next frame by appropriately using the partially detected pixel current.

Alternatively, as shown in FIG. 7 (d), after being turned on, the display device displays an image on the display unit 10, and applies 7 V as a test signal before turning off to detect the pixel current, thereby detecting the test signal. 5V can be applied to detect the pixel current.

Thereafter, when the display device is turned on, an image may be displayed by appropriately using the pixel current detected before the turn-off.

Alternatively, as shown in FIG. 7E, after being turned on, the display device may display an image on the display unit 10, but partially detect the pixel current for some pixels. When the pixel current detection is completed for all the pixels, the display device may display an image of the next frame using the detected pixel current as appropriate.

8 is a circuit diagram illustrating a pixel according to a second exemplary embodiment of the present invention.

Referring to FIG. 8, a pixel includes a switching transistor Tw, a driving transistor Td, a compensation transistor Tc, an initialization transistor Tsus, a reference voltage transistor Ts, a sensing transistor Tsen, and a first capacitor Chold. ), A second capacitor Cst, and an organic light emitting diode OLED.

In the embodiment of FIG. 3, the pixel current of the pixel is measured using the data lines D1 to Dm. However, the embodiment of FIG. 8 further includes a pixel current output line separated from the data line and connected to the pixel. The voltage can be supplied and the pixel current of the pixel can be measured.

In this case, the sensing transistor Tsen includes a gate electrode connected to the sensing line, one electrode connected to the fourth node NA, and the other electrode connected to the pixel current output line. The sensing transistor Tsen is turned on by the sensing signal Sense [i] of the gate-on voltage to connect the anode electrode of the organic light emitting diode OLED to the pixel current output line.

In an exemplary embodiment in which the data line and the pixel current output line are separated, a plurality of pixel current output lines connecting the pixel current detector 110 and each of the plurality of pixels must be added separately from the data lines D1 to Dm. will be.

The other components of the pixel of FIG. 8 are the same as those of FIG. 3, and the driving method of the display device including the pixel of FIG. 8 is the same as the driving method described with reference to FIGS.

9 is a circuit diagram illustrating a pixel according to a third exemplary embodiment of the present invention.

Referring to FIG. 9, a pixel includes a switching transistor Tw, a driving transistor Td, a compensation transistor Tc, an initialization transistor Tsus, a reference voltage transistor Ts, a sensing transistor Tsen, and a first capacitor Chold. ), A second capacitor Cst, and an organic light emitting diode OLED.

Unlike the pixel of FIG. 3, the reference voltage transistor Ts includes a gate electrode connected to the scan line, one electrode connected to the data line Dj, and the other electrode connected to the first node NC. The reference voltage transistor Ts is turned on by the scan signal S [i] of the gate-on voltage to transfer the data voltage to the first node NC (1 ≦ i ≦ n, 1 ≦ j ≦ m).

The first capacitor Chold includes one electrode connected to the reference voltage Vref and the other electrode connected to the first node NC.

Other components of the pixel are the same as those of FIG. 3, and the driving method of the display device including the pixel of FIG. 9 is the same as the driving method described with reference to FIGS. 4 to 6, and thus a detailed description thereof will be omitted.

10 is a circuit diagram illustrating a pixel according to a fourth exemplary embodiment of the present invention.

Referring to FIG. 10, a pixel includes a switching transistor Tw, a driving transistor Td, a compensation transistor Tc, an initialization transistor Tsus, a reference voltage transistor Ts, a sensing transistor Tsen, and a first capacitor Chold. ), A second capacitor Cst, and an organic light emitting diode OLED.

Unlike the pixel of FIG. 8, the reference voltage transistor Ts includes a gate electrode connected to the scan line, one electrode connected to the data line Dj, and the other electrode connected to the first node NC. The reference voltage transistor Ts is turned on by the scan signal S [i] of the gate-on voltage to transfer the data voltage to the first node NC (1 ≦ i ≦ n, 1 ≦ j ≦ m).

The first capacitor Chold includes one electrode connected to the reference voltage Vref and the other electrode connected to the first node NC.

Other components of the pixel are the same as those of FIG. 8, and the driving method of the display device including the pixel of FIG. 10 is the same as the driving method described with reference to FIGS. 4 to 6, and thus a detailed description thereof will be omitted.

DETAILED DESCRIPTION OF THE INVENTION The detailed description of the invention and the drawings so far referred to are merely illustrative of the invention, which is used only for the purpose of illustrating the invention and is used to limit the scope of the invention as defined in the meaning or claims. It is not. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

10: display unit 20: scan driver
30: data driver 40: signal controller
50: power supply voltage supply unit 60: pixel
70: compensation control signal unit 80: initialization signal unit
90: relay signal unit 100: sensing driver
110: pixel current detector

Claims (15)

A first capacitor connected between a data line and a first node, a switching transistor connecting the first node and a second node, a second capacitor connected between the second node and a third node, a gate to the third node A driving transistor connected to an electrode to control a driving current flowing from the first power supply voltage to the organic light emitting diode, a reference voltage transistor transferring a reference voltage to the first node, and a gate electrode connected to a sensing line, and a test signal is generated. A plurality of pixels each including a sensing transistor supplied to a light emitting diode; And
A pixel current detector configured to detect a pixel current flowing through the organic light emitting diode by the test signal when the sensing transistor is turned on;
Display device comprising a. According to claim 1,
When the organic light emitting diode emits light by the driving current in the plurality of pixels, the switching transistor is turned off, the reference voltage transistor is turned on, and the reference voltage is transmitted to the first node. And a data voltage corresponding to a scan signal of a gate-on voltage corresponding to each pixel is supplied to the first capacitor. According to claim 1,
Each of the plurality of pixels,
And an initialization transistor that is turned on by an initialization signal of a gate-on voltage to transfer a first power supply voltage to the second node. According to claim 1,
Each of the plurality of pixels,
And a compensation transistor that is turned on by a compensation control signal of a gate-on voltage to connect the gate electrode of the driving transistor and the anode electrode of the organic light emitting diode. According to claim 1,
And the sensing transistor is connected to the data line and supplies the test signal applied to the data line to the organic light emitting diode. According to claim 1,
And the sensing transistor is connected to a pixel current output line separated from the data line, and supplies the test signal applied to the pixel current output line to the organic light emitting diode. The method of claim 2,
And the pixel current detector detects the pixel current of the pixel on which light emission is terminated, connected to at least one sensing line. A first capacitor connected between a data line and a first node, a switching transistor connecting the first node and a second node, a second capacitor connected between the second node and a third node, a gate to the third node A driving transistor is connected to the electrode to control a driving current flowing from the first power supply voltage to the organic light emitting diode, and is turned on by a compensation control signal of a gate-on voltage to connect the gate electrode of the driving transistor to the anode electrode of the organic light emitting diode. And a plurality of pixels each including a compensation transistor configured to include a compensation transistor, a reference voltage transistor for transmitting a reference voltage to the first node, and a gate electrode connected to a sensing line, and a sensing transistor for supplying a test signal to the organic light emitting diode. In the driving method of the device,
Supplying the compensation control signal to the compensation transistor; And
Sensing the pixel current flowing through the organic light emitting diode by the test signal when the sensing transistor is turned on;
Display device driving method comprising a. The method of claim 8,
In the scanning period of the first frame, the switching transistor is turned off, the reference voltage transistor is turned on, the reference voltage is transmitted to the first node, and a data voltage applied to the data line is stored in the first capacitor. An injection step; And
A light emitting step of emitting light from the organic light emitting diode according to a driving current flowing through the driving transistor by a voltage stored in the second capacitor in a light emitting period of the first frame;
More,
The voltage stored in the second capacitor is in accordance with the voltage stored in the first capacitor in the scan period of the frame immediately before the first frame,
The light emitting step of each of the plurality of pixels is performed simultaneously, and the scanning step and the light emitting step overlap in time. The method of claim 9,
The injection step,
And applying an initialization signal of a gate-on voltage to a gate electrode of an initialization transistor that transfers a first power supply voltage to the second node. The method of claim 10,
The injection step,
Applying a scan signal of a gate-on voltage to a gate electrode of the reference voltage transistor; And
And applying a data voltage corresponding to the scan signal of the gate-on voltage to the data line and storing the data voltage in the first capacitor. The method of claim 11, wherein
The injection step,
Applying a compensation control signal of a gate-off voltage to a gate electrode of a compensation transistor connecting the gate electrode of the driving transistor and the anode electrode of the organic light emitting diode; And
And applying a compensation control signal of the gate off voltage to a gate electrode of the switching transistor. The method of claim 12,
The sensing step,
And detecting the pixel current of a pixel connected to at least one sensing line after the light emission step is completed. A first capacitor including one electrode connected to the data line and the other electrode connected to the first node;
A switching transistor including a gate electrode, one electrode connected to the first node, and the other electrode connected to the second node;
A second capacitor including one electrode connected to the second node and the other electrode connected to a third node;
A driving transistor including a gate electrode connected to the third node, one electrode connected to a first power supply voltage, and another electrode connected to an anode electrode of the organic light emitting diode;
A reference voltage transistor comprising a gate electrode, one electrode connected to a reference voltage, and the other electrode connected to the first node; And
A sensing transistor including a gate electrode connected to a sense line, one electrode connected to the data line, and another electrode connected to the anode electrode of the organic light emitting diode;
Including,
And a test signal applied to the data line when the sensing transistor is turned on according to a sensing signal supplied to the sensing line. A first capacitor including one electrode connected to the data line and the other electrode connected to the first node;
A switching transistor including a gate electrode, one electrode connected to the first node, and the other electrode connected to the second node;
A second capacitor including one electrode connected to the second node and the other electrode connected to a third node;
A driving transistor including a gate electrode connected to the third node, one electrode connected to a first power supply voltage, and the other electrode connected to an anode electrode of the organic light emitting diode;
A reference voltage transistor comprising a gate electrode, one electrode connected to a reference voltage, and the other electrode connected to the first node; And
A sensing transistor including a gate electrode connected to a sense line, one electrode connected to a pixel current output line, and another electrode connected to the anode electrode of the organic light emitting diode;
Including,
And a test signal applied to the pixel current output line when the sensing transistor is turned on according to a sense signal supplied to the sense line.

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