KR100740135B1 - An organic light emitting display with sensor, an driving method of the organic light emitting display - Google Patents

Abstract

An OLED device and a driving method thereof are provided to simplify structure of an organic light emitting diode by selectively using the organic light emitting diode as a light emitting element or a light receiving element. An OLED(Organic Light Emitting Display) device includes plural data lines(Data[m]), plural scan lines(Scan[n]), and plural pixel circuits. The data lines supply a data voltage representing an image signal. The scan lines supply a scan signal. The pixel circuits include plural pixels defined by the data and scan lines. One or more of the pixel circuits include an organic light emitting diode(OLED), a driving transistor(Md), and a sensing capacitor. The organic light emitting diode emits light corresponding to an applied current amount. The driving transistor supplies a current to the organic light emitting diode corresponding to the data voltage. The sensing capacitor is connected between the anode and cathode of the organic light emitting diode.

Description

Sensor combined organic display and driving method {AN ORGANIC LIGHT EMITTING DISPLAY WITH SENSOR, AN DRIVING METHOD OF THE ORGANIC LIGHT EMITTING DISPLAY}

1 illustrates a general organic light emitting diode.

2 is a conceptual diagram of a pixel circuit according to an exemplary embodiment of the present invention.

3 is a pixel circuit diagram according to an embodiment of the present invention.

4 is a timing diagram applied to the pixel circuit of FIG. 3.

5 is a diagram illustrating an organic light emitting display device according to an exemplary embodiment of the present invention.

6 is a view showing a sensing unit according to an embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention 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 and a driving method thereof.

Recently, display devices are also required to be lighter and thinner in accordance with the light weight and thickness of personal computers and televisions, and according to such requirements, liquid crystal displays (LCDs) and organic light emitting diodes are used instead of cathode ray tubes (CRTs). Flat panel displays, such as organic light emitting display (PDP), plasma display panel (PDP), field emission display (FED), and the like, have been developed.

These flat panel display devices sequentially select a horizontal scanning line and apply a necessary image signal voltage to each pixel connected to the selected scanning line through a vertical data line to display an image.

Devices that can not only display functions but also input functions by adding a touch panel to such display devices are also used. In these devices, a transparent touch panel is attached to the front of the display device to perform an input function.

Recently, a panel has been developed in which a sensor (light-receiving element) for detecting light is separately added to a pixel of a liquid crystal display device so as to function as a touch panel as well as a display device.

However, such a liquid crystal display having a combined sensor requires a sensor for detecting light in a separate process, which makes the process complicated and expensive.

In addition, the conventional display device for combined use of the sensor has a problem in that the light emitting area is reduced by the area of the light sensing element because the light emitting area and the light sensing area are separated.

 The present invention has been made to solve such a problem, and to provide a combined display device with a simple process and low cost. In addition, the present invention is to provide a combined display device without reducing the light emitting area.

An organic light emitting display device according to an aspect of the present invention for achieving the above object is

A plurality of data lines for transmitting data voltages representing image signals;

A plurality of scan lines for transmitting scan signals;

A plurality of pixel circuits each formed in the plurality of pixels defined by the plurality of data lines and the plurality of scanning lines,

At least one pixel circuit of the plurality of pixel circuits

An organic light emitting diode for emitting light corresponding to the amount of current applied;

A driving transistor supplying a current to the organic electroluminescent device in response to the data voltage; And

And a sensing capacitor connected between the anode and the cathode of the organic light emitting diode.

On the other hand, the organic light emitting display device according to another aspect of the present invention

A plurality of data lines for transmitting data voltages representing image signals;

A plurality of scan lines for transmitting scan signals;

A plurality of pixel circuits each formed in the plurality of pixels defined by the plurality of data lines and the plurality of scanning lines,

At least one pixel circuit of the plurality of pixel circuits

An organic light emitting diode which emits light corresponding to the amount of forward current applied in the first operating mode and flows in a reverse current corresponding to the intensity of the ambient light in the second operating mode;

A switching transistor for switching a data voltage applied to the data line in response to a scan signal applied to the scan line;

A driving transistor supplying a forward current to the organic light emitting diode in response to the data voltage input to the gate through the switching transistor;

A holding capacitor for maintaining a data voltage applied to a gate of the driving transistor for a predetermined time; And

And a sensing capacitor connected between the anode and the cathode of the organic light emitting diode.

On the other hand, the driving method of the organic light emitting display device according to an aspect of the present invention

A plurality of matrix lines having a plurality of data lines, a plurality of scan lines intersecting the plurality of data lines, and a driving transistor formed in a region defined by the plurality of data lines and the plurality of scan lines, each of which supplies a current to an organic light emitting diode A driving method of an organic light emitting display device comprising a pixel of

(a) supplying a driving current in a first direction corresponding to an image signal to the organic light emitting diode by the driving transistor to emit light corresponding to the driving current;

(b) turning on the driving transistor to bias the organic light emitting diode to a reverse voltage and charging the biased voltage to a capacitor connected in parallel to the organic light emitting diode; And

(c) turning off the driving transistor to discharge the voltage charged in the capacitor to cause the organic light emitting diode to flow a current in a second direction corresponding to the intensity of ambient light.

Meanwhile, a method of driving an organic light emitting display device according to another feature of the present invention is

A driving method of an organic light emitting display device including a plurality of pixel circuits each including an organic light emitting diode,

(a) forward biasing the organic light emitting diode;

(b) supplying a forward current corresponding to an image signal to the forward biased organic light emitting diode to emit light corresponding to the driving current;

(c) biasing the organic light emitting diode in a reverse direction;

(d) flowing a reverse current corresponding to the intensity of ambient light to the organic light emitting diode to vary the voltage between the cathode and the anode of the organic light emitting diode; And

(e) detecting the intensity of ambient light based on the voltage variation between the cathode and the anode of the organic light emitting diode.

Meanwhile, a method of driving an organic light emitting display device according to another aspect of the present invention is

A driving method of an organic light emitting display device having a plurality of organic light emitting diodes each including a first organic light emitting diode and a second organic light emitting diode,

(a) forward biasing the first organic light emitting diode;

(b) supplying a forward current corresponding to an image signal to the first biased organic light emitting diode to emit light corresponding to the driving current;

(c) biasing the second organic light emitting diode in a reverse direction;

(d) flowing a current in a reverse direction corresponding to the intensity of ambient light to the second organic light emitting diode to vary the voltage between the cathode and the anode of the second organic light emitting diode; And

(e) detecting the intensity of ambient light based on the voltage variation between the cathode and the anode of the second organic light emitting diode.

DETAILED DESCRIPTION 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 the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is "connected" to another part, this 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, which means that it may further include other components, except to exclude other components unless otherwise stated.

Hereinafter, with reference to the accompanying drawings will be described an embodiment of the present invention;

In general, an organic light emitting display device is a display device that electrically emits light by electrically exciting an organic light emitting diode (hereinafter, referred to as OLED) which is a fluorescent organic compound. As shown in FIG. 1, the organic light emitting diode has a structure of an anode (ITO), an organic thin film, and a cathode layer (Metal). The organic thin film has a multi-layer structure including an emission layer (EML), an electron transport layer (ETL), and a hole transport layer (HTL) in order to improve the emission efficiency by improving the balance between electrons and holes. It also includes a separate electron injection layer (EIL: Electron Injecting Layer) and hole injection layer (HIL: Hole Injecting Layer).

When such an organic light emitting diode flows a current in a forward direction, light corresponding to the flowing current emits light. As described above, the organic light emitting display device is a device for displaying a desired image by emitting light corresponding to the image signal by flowing a current corresponding to the image signal to the organic light emitting diode.

On the other hand, the organic light emitting diode has a property of changing the voltage-current characteristics of the organic light emitting diode according to the intensity of ambient light when a reverse voltage is applied. Therefore, the intensity of ambient light may be sensed by using a change in voltage and current characteristics according to the intensity of ambient light.

According to the present invention, the organic light emitting diode emits light corresponding to the current flowing when a forward voltage is applied (as a display element), and when the reverse voltage is applied, it corresponds to the intensity of ambient light. By using the property in which the voltage-current characteristic changes (the property as a sensor), a display device for both sensors is provided.

2 is a diagram conceptually illustrating a pixel circuit of an organic light emitting diode display according to an exemplary embodiment of the present invention.

As shown in FIG. 2, a pixel circuit according to an exemplary embodiment of the present invention includes an organic light emitting diode OLED, a sensing capacitor Cs, and a driving transistor Md.

The anode and the cathode of the organic light emitting diode are respectively connected to the drain of the first power supply voltage VDD and the driving transistor Md, and the sensing capacitor Cs is connected between the cathode and the anode of the organic light emitting diode OLED. A gate (not shown) corresponding to the image signal is applied to the gate of the driving transistor Md, and a source of the driving transistor is connected to the second power supply voltage VSS. At this time, the second power supply voltage VSS is set to a different value according to an operation mode as described later.

Next, the operation of the pixel circuit shown in FIG. 2 will be described.

According to an embodiment of the present invention, the pixel circuit operates in two operation modes, namely, display mode (light emitting mode) and sensing mode (light receiving mode).

First, the operation of the display mode will be described. This display mode corresponds to an operation mode of a general organic light emitting display device.

In the display mode, the second power supply voltage VSS is first set to a value lower than the first power supply voltage VDD. Then, a voltage corresponding to the image signal is applied to the gate of the driving transistor Md, and a current corresponding to the voltage applied to the gate from the drain of the driving transistor Md to the source (that is, the voltage corresponding to the image signal) flows. do. Therefore, the same forward current Ifor as the current flowing through the driving transistor Md flows through the organic light emitting diode, and light of intensity corresponding to the current emits light.

As shown in FIG. 2, it can be seen that in the display mode, the anode voltage N2 of the organic light emitting diode OLED is higher than the cathode voltage N1. (Ie, forward voltage is applied)

Next, the operation of the sensing mode according to an embodiment of the present invention will be described.

In the sensing mode, the second power supply voltage VSS is set to a higher value than the first power supply voltage VDD. Then, the driving transistor Md is turned on so that the cathode voltage N1 of the organic light emitting diode OLED is changed to the second power supply voltage VSS. Therefore, the anode voltage N2 of the organic light emitting diode OLED is set lower than the cathode voltage N1 (that is, a reverse voltage is applied to the organic light emitting diode). The second power supply voltage VSS is applied to the sensing capacitor Cs. ) And a charge corresponding to the product of the difference between the first power supply voltage VDD (VSS-VDD) and the capacitance C are charged. After that, when the driving transistor Md is turned off, the charge charged in the capacitor Cst flows to the reverse current Irev of the organic light emitting diode. At this time, the reverse current (Irev) of the organic light emitting diode changes its value according to the intensity of the ambient light, it is possible to detect the intensity of the ambient light by measuring the voltage value of the cathode voltage of the organic light emitting diode or both ends of the capacitor (Cs). .

3 and 4, the operation of the pixel circuit and the pixel circuit according to the embodiment of the present invention will be described.

3 is a diagram illustrating a pixel circuit according to an exemplary embodiment of the present invention, and FIG. 4 is a timing diagram for driving the pixel circuit of FIG. 3.

As shown in FIG. 3, a pixel circuit according to an exemplary embodiment of the present invention includes an organic light emitting diode (OELD), a switching transistor (Ms), a driving transistor (Md), transistors (M1, M2), a holding capacitor (Cst), And a sensing capacitor Cs.

The switching transistor Ms has a source connected to the data line Data [m], a gate connected to the scan line Scan [n], and responding to the selection signal Vg applied from the scan line Scan [n]. Are turned on, and a data voltage corresponding to an image signal applied to the data line Data [m] is transferred to the driving transistor Md. The driving transistor Md has a gate connected to a source of the switching transistor Ms, a source connected to a second power line supplying a second power supply voltage VSS, and a drain of the driving transistor Md having a cathode of the organic light emitting diode OLED ( N1).

The organic light emitting diode OELD is connected to a first power line to which an anode supplies a first power voltage VDD.

The sustain capacitor Cst is connected to the first power supply line and the source of the switching transistor Ms (gate of the driving transistor Md) N3 and maintains the voltage applied through the switching transistor Ms for one frame.

The sensing capacitor Cs is connected between the anode N2 and the cathode N1 of the organic light emitting diode OLED.

The transistor M1 has a gate connected to the cathode N1 of the organic light emitting diode and a drain connected to the first power line, and the transistor M2 has a drain connected to the source of the transistor M1 and a select signal line S at the gate. (Sel) is connected and the source is connected to Read. The transistors M1 and M2 amplify the voltage of the node N1 in the sensing mode and supply the voltage to the outside through a read line.

3 and 4, the operation of the pixel circuit according to the embodiment of the present invention will be described.

First, the operation of the display mode will be described. As shown in Fig. 4, in the display mode, the transistor M2 is kept off. (I.e., the selection voltage applied to the selection signal line S-Sel maintains the low level (grounding voltage).) And the second power supply voltage VSS is lower than the first power supply voltage VDD (Vsh_l, for example). Ground voltage). Operation of the other display modes is almost the same as that of the general organic light emitting display device.

 As shown in FIG. 3, when the transistor Ms is turned on by the scan signal Vg applied to the gate of the switching transistor Ms, the data voltage Vdata is driven through the data line Data [m]. It is applied to the gate N3 of Md. The voltage applied to the gate M3 of the driving transistor Md is maintained for one frame by the first capacitor Cst.

The driving transistor Md causes a current corresponding to the data voltage Vdata applied to the gate N3 to flow, and a current equal to the current flowing through the transistor Mb is generated at the first power supply voltage VDD. 2 Light flows through the organic light emitting diode (OELD) in the direction of the power supply voltage (VSS).

In such a display mode, an organic light emitting diode is used as a light emitting element.

After receiving control signal from outside or set time, it operates as sensing mode.

As illustrated in FIG. 4, in the sensing mode, the second power supply voltage VSS is set to a value Vss_h higher than the first power supply voltage VDD. Subsequently, when the transistor Ms is turned on by the scan signal Vg applied to the gate of the switching transistor Ms, a high data voltage Vdata is applied to the driving transistor Md through the data line Data [m]. It is applied to the gate N3 to turn on the driving transistor Md. As a result, the cathode voltage N1 of the organic light emitting diode OLED is changed to the second power supply voltage VSS higher than the first power supply voltage VDD so that the organic light emitting diode OLED is biased to the reverse voltage, and the sensing capacitor The charge corresponding to the product of the capacitance (C) and the voltage corresponding to the difference (VSS-VDD) between the second power supply voltage (VSS) and the first power supply voltage (VDD) are charged to (Cs).

Thereafter, while the scan signal Vg is applied to the scan line Scan [n], a low level data voltage Vdata is applied through the data line Data [m] to turn off the driving transistor Mb. Let's do it. Then, the charge charged in the capacitor Cst is discharged to the first power line through the organic light emitting diode. That is, the reverse current flows through the organic light emitting diode. At this time, the reverse current of the organic light emitting diode is changed depending on the intensity of the ambient light. Accordingly, the voltage of the node 1 varies according to the intensity of ambient light. That is, as shown in FIG. 4, when the intensity of ambient light is relatively small light 1 (for example, when a pixel is pressed by a finger when used as a touch panel), the discharged voltage is small (that is, the reverse current value is decreased). Small, so that the voltage at node 1 is relatively large and the intensity of ambient light is relatively large (e.g., when the pixel is not pressed by a finger when used as a touch panel). , The reverse current value becomes large, so that the voltage at node 1 is relatively small.

Subsequently, when the selection voltage is applied to the selection signal line S-Sel and the transistor M2 is turned on, the voltage amplified by the transistor M1 is supplied to the read line Read and transferred to an external circuit (not shown). .

At this time, the external circuit integrates the output current flowing by the selection of the transistor M2 and reads it as a voltage as shown in FIG. Therefore, according to the embodiment of the present invention it is possible to detect the intensity of light through the amount of voltage accumulated by the external circuit.

In such a sensing mode, an organic light emitting diode is used as a light receiving element.

As described above, according to the exemplary embodiment of the present invention, since the organic light emitting diode (light emitting device) may serve as a light receiving device, there is an advantage in that the structure is simplified without having to make a separate light receiving device.

Further, in the embodiment of the present invention, since one organic light emitting diode can be selectively used as a light emitting element and a light receiving element according to an operation mode, it is to provide a display device for a sensor without reducing the light emitting area.

Next, an organic light emitting display device according to an exemplary embodiment of the present invention will be described.

5 is a diagram illustrating an organic light emitting display device according to an exemplary embodiment of the present invention.

As shown in FIG. 5, an organic light emitting display device according to an exemplary embodiment of the present invention includes an organic light emitting display panel 100, a scan driver 200, a data driver 300, a controller 400, and a sensor 500. ) And a power supply voltage supply unit 600.

The organic light emitting display panel 100 includes a plurality of data lines D1, D2, D3,..., Dy that transmit data voltages indicating image signals, and scan lines S1, S2, which transmit scan signals sequentially. S3, ..., Sz), and pixel circuits 110 formed on a plurality of pixels defined by the plurality of data lines and the plurality of scan lines, respectively. At this time, all the pixel circuits or one or more pixel circuits are formed of the same circuit as the pixel circuit shown in FIG.

The controller 400 controls the light emitting display device according to the exemplary embodiment of the present invention to the display mode or the sensing mode by a mode selection signal input from the outside or input from the microcomputer.

First, when the mode selection signal is the display mode, the controller 400 receives the image signal RGB and the synchronization signals Vsync and Hsync input from the outside, and outputs the control signal and the image signal to the data driver 300. The control driver and the scan signal are output to the scan driver 200.

In addition, when the mode selection signal is the sensing mode, the controller 400 transmits a control signal necessary for the operation of the sensing mode to the data driver 300, the scan driver 200, the sensing unit 500, and the power voltage supply unit 600. Output

The data driver 300 applies a data voltage representing an image signal to the plurality of data lines in the display mode, and sequentially applies a scan signal to the plurality of scan lines in the scan driver 200 display mode. Meanwhile, in the sensing mode, the data driver 300 applies the waveform shown in FIG. 4 to the data line corresponding to the pixel circuit shown in FIG. 3, and the scan driver 200 corresponds to the pixel circuit shown in FIG. 3. The waveform shown in FIG. 4 is applied to the scanning line.

The sensing unit 500 detects the cathode voltage or the voltage at both ends of the organic light emitting diode by applying the selection signal to the signal selection line in the sensing mode, and detects the intensity of the external light based on the detected voltage.

The power supply voltage supply unit 600 supplies the first power supply voltage and the second power supply voltage to the first power supply line and the second power supply line shown in FIG. 3, respectively. In this case, the power supply voltage supplying unit 600 supplies a second power supply voltage lower than the first power supply voltage to the second power supply line in the display mode, but supplies a second power supply voltage higher than the first power supply voltage in the sensing mode to the second power supply. Feed the line.

6 is a view illustrating in detail the sensing unit 500 according to an embodiment of the present invention.

As shown in FIG. 6, the sensing unit 500 includes a voltage accumulator 510, a photodetector 520, and a lookup table 530.

The voltage accumulator 510 accumulates the value obtained by reading the voltage of the cathode of the light emitting diode of the pixel circuit shown in FIG. 3, and detects the accumulated waveform shown in FIG.

The lookup table 530 stores the intensity of the ambient light and the value of the accumulated voltage corresponding thereto as a table. At this time, the light intensity and the value of the accumulated voltage corresponding thereto are determined by the type of the organic light emitting diode, the gain of the transistor, and the like, and thus are the data previously known to those skilled in the art as experimental values.

The light detector 520 inquires the lookup table 530 of the accumulated voltage value output from the voltage accumulator 510 to detect the intensity of the ambient light and transmits the value to the controller.

As mentioned above, although the Example of this invention was described, this invention is not limited only to the above-mentioned Example, A various other deformation | transformation and a change are possible.

For example, in the exemplary embodiment of the present invention illustrated in FIG. 3, one organic light emitting diode is selectively used as a light emitting element or a light receiving element (that is, the display device is used as a display mode or a sensing mode by dividing in time). By spatially dividing, some organic light emitting diodes may be used for light emitting devices only, and the remaining organic light emitting diodes may be used for light receiving devices only. As described above, even when the organic light emitting diode is used separately for the light receiving element and the light emitting element, the light emitting diode can be formed in the same process, so that the manufacturing process can be simplified.

In addition, although the pixel circuit shown in FIG. 3 has been described as an example based on the pixel circuit of the organic light emitting display device having the simplest structure, the pixel circuit shown in FIG. 3 may be applied to other types of pixel circuits, for example, a current driven pixel circuit. Can be.

In addition, although the pixel circuit shown in FIG. 3 was described using the NMOS transistor as an example, it is also possible to use a PMOS transistor or to mix NMOS and a PMOS transistor.

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

As described above, according to the present invention, since the organic light emitting diode can serve as a light receiving element, there is no need to make a separate light receiving element, thereby simplifying the structure.

Further, according to the present invention, since one organic light emitting diode can be selectively used as a light emitting element and a light receiving element according to an operation mode, it is possible to provide a combined display device without reducing the light emitting area.

Claims (20)

A plurality of data lines for transmitting data voltages representing image signals; A plurality of scan lines for transmitting scan signals; A plurality of pixel circuits each formed in the plurality of pixels defined by the plurality of data lines and the plurality of scanning lines, At least one pixel circuit of the plurality of pixel circuits An organic light emitting diode for emitting light corresponding to the amount of current applied; A driving transistor supplying a current to the organic electroluminescent device in response to the data voltage; And And a sensing capacitor connected between the anode and the cathode of the organic light emitting diode. The method of claim 1, And the organic light emitting display device is selectively operated in a display mode and a sensing mode. The method of claim 2, And, in the display mode, the organic light emitting diode emits light corresponding to a current in a forward direction supplied by the driving transistor. The method of claim 2, In the sensing mode, the sensing capacitor is charged to the first voltage, And a first voltage charged in the sensing capacitor is discharged to flow in a reverse current of the organic light emitting diode corresponding to the intensity of ambient light. The method according to any one of claims 2 to 4, An anode and a cathode of the organic light emitting diode are respectively connected to a first power supply voltage and a first terminal of the driving transistor, and a second terminal of the driving transistor is connected to a second power supply voltage, The first power supply voltage is set higher than the second power supply voltage in the display mode, and the first power supply voltage is set lower than the second power supply voltage in the sensing mode. The method of claim 5, In the sensing mode, The driving transistor is turned on to charge the sensing capacitor with a voltage corresponding to a difference between the second power supply voltage and the first power supply voltage, And the driving transistor is turned off so that a voltage charged in the sensing capacitor is discharged and flows in a reverse current of the organic light emitting diode corresponding to the intensity of ambient light. A plurality of data lines for transmitting data voltages representing image signals; A plurality of scan lines for transmitting scan signals; A plurality of pixel circuits each formed in the plurality of pixels defined by the plurality of data lines and the plurality of scanning lines, At least one pixel circuit of the plurality of pixel circuits An organic light emitting diode which emits light corresponding to the amount of forward current applied in the first operating mode and flows in a reverse current corresponding to the intensity of the ambient light in the second operating mode; A switching transistor for switching a data voltage applied to the data line in response to a scan signal applied to the scan line; A driving transistor supplying a forward current to the organic light emitting diode in response to the data voltage input to the gate through the switching transistor; A holding capacitor for maintaining a data voltage applied to a gate of the driving transistor for a predetermined time; And And a sensing capacitor connected between the anode and the cathode of the organic light emitting diode. The method of claim 7, wherein The organic light emitting display device is characterized in that the first operation mode and the second operation mode is driven by time division. The method of claim 7, wherein In the second operation mode The driving transistor is turned on and the sensing capacitor is charged with a first voltage, and the driving transistor is turned off and the first voltage charged in the sensing capacitor is discharged to flow in a reverse current of the organic light emitting diode. Light emitting display device. The method according to any one of claims 7 to 9, An anode and a cathode of the organic light emitting diode are respectively connected to a first power line supplying a first power supply voltage and a drain of the driving transistor, and a source of the driving transistor is connected to a second power supply line supplying a second power supply voltage. , The first power supply voltage is set higher than the second power supply voltage in the first operation mode, and the first power supply voltage is set lower than the second power supply voltage in the second operation mode. Device. The method of claim 10, A gate is connected to the selection signal line and a source is connected to the readout line to detect a voltage of the cathode of the organic light emitting diode in response to the selection signal supplied to the selection signal line, and further provides a first transistor to supply the readout line An organic light emitting display device comprising. The method of claim 11, And a second transistor having a gate connected to the cathode of the organic light emitting diode, a drain connected to the first power line, and a source connected to the gate of the first transistor. The method of claim 10, A data driver for applying a data voltage representing an image signal to the plurality of data lines in the first operation mode; A scan driver which sequentially applies a scan signal to the plurality of scan lines in the first operation mode; A power supply voltage supply unit supplying a first power supply voltage and a second power supply voltage to the first power supply line and the second power supply line, respectively; A sensing unit which detects a cathode voltage of the organic light emitting diode in the second operation mode and detects the intensity of external light based on the detected voltage; And a controller configured to control an operation of the first operation mode or the second operation mode based on a mode selection signal. The method of claim 13, The sensing unit  A voltage accumulator configured to accumulate a value obtained by reading a voltage of a cathode of the organic light emitting diode;  A look-up table storing a value of ambient light intensity and a corresponding accumulated voltage; And And a light detector for inquiring the accumulated voltage value output from the voltage accumulator to the lookup table to detect an intensity of ambient light and to transmit the detected value to the controller. A plurality of matrix lines having a plurality of data lines, a plurality of scan lines intersecting the plurality of data lines, and a driving transistor formed in a region defined by the plurality of data lines and the plurality of scan lines, each of which supplies a current to an organic light emitting diode In the driving method of an organic light emitting display device comprising a pixel, (a) supplying a driving current in a first direction corresponding to an image signal to the organic light emitting diode by the driving transistor to emit light corresponding to the driving current; (b) turning on the driving transistor to bias the organic light emitting diode to a reverse voltage and charging the biased voltage to a capacitor connected in parallel to the organic light emitting diode; And (c) turning off the driving transistor to discharge the voltage charged in the capacitor to cause the organic light emitting diode to flow a current in a second direction corresponding to the intensity of ambient light. Driving method. The method of claim 15, An anode and a cathode of the organic light emitting diode are respectively connected to a first power line supplying a first power supply voltage and a drain of the driving transistor, and a source of the driving transistor is connected to a second power supply line supplying a second power supply voltage. , In the step (a), the first power supply voltage is set higher than the second power supply voltage, And in the step (b), the first power supply voltage is set lower than the second power supply voltage. The method according to claim 15 or 16, (d) amplifying and accumulating the voltage of the cathode of the organic light emitting diode after step (c) (e) detecting the intensity of ambient light based on the accumulated voltage. A driving method of an organic light emitting display device including a plurality of pixel circuits each including an organic light emitting diode, (a) forward biasing the organic light emitting diode; (b) supplying a forward current corresponding to an image signal to the forward biased organic light emitting diode to emit light corresponding to the driving current; (c) biasing the organic light emitting diode in a reverse direction; (d) flowing a reverse current corresponding to the intensity of ambient light to the organic light emitting diode to vary the voltage between the cathode and the anode of the organic light emitting diode; And (e) detecting the intensity of ambient light based on a voltage variation between the cathode and the anode of the organic light emitting diode. A driving method of an organic light emitting display device having a plurality of organic light emitting diodes each including a first organic light emitting diode and a second organic light emitting diode, (a) forward biasing the first organic light emitting diode; (b) supplying a forward current corresponding to an image signal to the first biased organic light emitting diode to emit light corresponding to the driving current; (c) biasing the second organic light emitting diode in a reverse direction; (d) flowing a reverse current corresponding to the intensity of ambient light to the second organic light emitting diode to vary the voltage between the cathode and the anode of the second organic light emitting diode; And (e) detecting the intensity of ambient light based on a voltage variation between the cathode and the anode of the second organic light emitting diode. The method of claim 19, And the first light emitting diode operates only as a light emitting element, and the second light emitting diode operates only as a light receiving element.

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