KR20110078435A - Organic light emitting display device and driving method thereof - Google Patents

Abstract

PURPOSE: An organic electroluminescent display device and a driving method thereof are provided to prevent the reduction of a driving current due to a threshold voltage shift. CONSTITUTION: A sensor circuit unit(SNP) includes a first capacitor(Cst1) which stores a reference voltage in response to a sensing signal and a second capacitor(Cst2) which applies higher voltage than a threshold voltage of a driving transistor. A first switching transistor(S1) stores data signal in the first capacitor and a third capacitor in response to a scan signal as a data voltage. A second switching transistor(S2) controls high potential voltage supply time to the driving transistor in response to a light emitting signal.

Description

Organic Light Emitting Display Device and Driving Method

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

The organic light emitting display device used in the organic light emitting display device is a self-light emitting device having a light emitting layer formed between two electrodes. In the organic light emitting display device, electrons and holes are injected into the light emitting layer from an electron injection electrode and a hole injection electrode, respectively, and an exciton in which the injected electrons and holes combine is excited. The device emits light when it falls from the ground state to the ground state.

An organic light emitting display device using an organic light emitting display device includes a top emission type, a bottom emission type, and a dual emission type according to a direction in which light is emitted. According to this, it is divided into passive matrix type and active matrix type.

When the scan signal, the data signal, and the power are supplied to the plurality of subpixels arranged in a matrix form, the organic light emitting display device may display an image by emitting light of the selected subpixel.

Since the threshold voltage of the transistor shifts, the organic light emitting display device has a problem in that the driving current decreases with time and the life of the device is reduced.

SUMMARY OF THE INVENTION The present invention for solving the above problems of the background art is to provide an organic light emitting display device which can prevent the reduction of the driving current caused by the threshold voltage shift, improve the longevity of the device and improve the display quality. In addition, the present invention is to provide an organic light emitting display device that can be configured to clear the previous data voltage and to accurately sense the threshold voltage at least two times to prevent the opening area degradation accompanying the threshold voltage compensation circuit design.

According to the aforementioned problem solving means, the present invention provides a sensor including a second capacitor configured to store a reference voltage in a first capacitor and apply a voltage higher than a threshold voltage of a driving transistor in response to a sensing signal supplied in at least two circuits. Circuit section; A first switching transistor configured to store the data signal as a data voltage in the first capacitor and the third capacitor in response to the scan signal; And a second switching transistor configured to adjust a time period during which a high potential voltage is supplied to the driving transistor in response to a light emitting signal.

The first sensing signal supplied among the sensing signals may be a signal for clearing the previous data voltage, and the second sensing signal supplied second may be a signal for sensing the threshold voltage of the driving transistor.

The sensor circuit unit may include a first transistor that stores a reference voltage in the first capacitor in response to the sensing signal, and a second transistor that stores the threshold voltage of the driving transistor in the second capacitor in response to the sensing signal. .

The time at which the sensing signal is supplied may be earlier than the time at which the scan signal is supplied.

In the first transistor, a gate electrode is connected to a sensor wiring to which a sensing signal is supplied, a first electrode is connected to a reference voltage wiring to which a reference voltage is supplied, a second electrode is connected to a first node, and a second transistor is connected to a sensor wiring. Data in which the gate electrode is connected, the first electrode is connected to the second node, the second electrode is connected to the third node, and the first switching transistor is connected to the scan wiring to which the scan signal is supplied, the gate electrode is connected, and the data signal is supplied. The first electrode is connected to the wiring, the second electrode is connected to the first node, and the second switching transistor is connected to the signal wiring to which the light emitting signal is supplied, and the first electrode to the high potential power wiring to which the high potential voltage is supplied. The electrode is connected, the second electrode is connected to the third node, one end of the first capacitor is connected to the first node and the other end is connected to the reference voltage wiring, and the second capacitor is connected to the gay of the second transistor. One end is connected to the electrode and is connected to the other end to the third node, a third capacitor may be end connected to a first node coupled to the other end to the second node.

The driving transistor has a low potential power supply wiring in which a gate electrode is connected to a second node, a first electrode is connected to a third node, a second electrode is connected to an anode electrode of an organic light emitting diode, and the organic light emitting diode is supplied with a low potential voltage. The cathode electrode can be connected to the.

The ratio of the turn off time and the turn on time of the second switching transistor may be 1/9 to 9/1 in one frame period.

The capacitance of the second capacitor may have a capacity of 2 to 5 times that of the parasitic capacitor formed between the gate electrode and the second node of the second transistor.

The capacity of the second capacitor may be 0.4pF to 2.5pF.

In another aspect, the present invention, by using a first transistor that is divided into at least two times in response to the sensing signal supplied to the second capacitor using a second transistor that stores the reference voltage in the first capacitor and responds to the sensing signal equally A sensing step of applying a voltage higher than a threshold voltage of the driving transistor to the capacitor and storing a low reference voltage for sensing the threshold voltage of the driving transistor in the first capacitor and the third capacitor; A data voltage storing step of storing the data signal as a data voltage in the first capacitor and the third capacitor by using the first switching transistor in response to the scan signal; And a light emitting step of controlling a time when a high potential voltage is supplied to the driving transistor by using the second switching transistor in response to the light emitting signal.

The ratio of the turn off time and the turn on time of the second switching transistor may be 1/9 to 9/1 in one frame period.

The present invention has the effect of providing an organic light emitting display device which can prevent the reduction of the driving current due to the shift of the threshold voltage, achieve the long life of the device and improve the display quality. In addition, the present invention has the effect of providing an organic light emitting display device that can be configured to clear the previous data voltage and to accurately sense the threshold voltage at least two times to prevent the opening area degradation accompanying the threshold voltage compensation circuit design have.

Hereinafter, with reference to the accompanying drawings, the specific content for the practice of the present invention will be described.

1 is a schematic block diagram of an organic light emitting display device according to an embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of a subpixel.

As illustrated in FIG. 1, an organic light emitting display device according to an exemplary embodiment of the present invention includes a data driving unit DRV, a scan driving unit SDRV, a power supply unit PWR, and a display panel PNL.

The data driver DDRV samples, latches, and converts a digital data signal supplied from the timing driver in response to a data timing control signal supplied from an external driver, for example, and converts the data into data of a parallel data system. The data driving unit DVV converts a digital data signal into a gamma reference voltage and converts the data signal into an analog data signal. The data driver DDRV supplies the data signal converted through the data line DATA to the subpixel SP included in the display panel PNL.

The scan driver SDRV adjusts the level of the signal to the swing width of the gate driving voltage at which the transistors of the sub-pixel SP included in the display panel PNL can operate in response to a gate timing control signal supplied from an external device, for example, the timing driver. The scan signals are generated sequentially while shifting. The scan driver SDRV supplies the scan signal generated through the scan wiring SCAN to the subpixel SP included in the display panel PNL. In addition, the scan driver SDRV may supply the sensing signal and the light emission signal to the subpixel SP included in the display panel PNL through the sensor wiring SENSE and the signal wiring EM. The sensing signal and the emission signal may be generated by a control driver formed separately from the scan driver SDRV. In this case, the sensing signal and the light emission signal are supplied to the sub-pixel SP included in the display panel PNL through the sensor wiring SENSE and the signal wiring EM connected to the control driver.

The power supply unit PWR generates a high potential voltage, a low potential voltage, a reference voltage, and the like based on the power voltage supplied from the outside, and then generates the high potential power wiring (VDD), the low potential power wiring (VSS), and the reference voltage wiring ( REF) and the like to the subpixels SP. Here, the reference voltage supplied through the reference voltage wiring REF may be a voltage having a level between the high potential voltage and the low potential voltage or a level lower than this. The power supply unit PWR may supply power not only to the subpixel SP but also to the data driver DDRV or the scan driver SDRV.

The display panel PNL includes subpixels SP arranged in a matrix. The subpixel SP included in the display panel PNL includes a sensor circuit SNP as shown in FIG. 2. The sensor circuit SNP stores the reference voltage supplied through the reference voltage line REF in the first capacitor Cst1 and the third capacitor Cst3 in response to the sensing signal divided into at least two circuits, and drives the driving transistor ( A reference voltage higher than the threshold voltage of the driving transistor DR is stored in the second capacitor Cst2 for sensing the threshold voltage of the DR. To this end, the sensor circuit SNP may have a first transistor T1 that stores the reference voltage in the first capacitor Cst1 in response to the sensing signal and a threshold voltage higher than the threshold voltage of the driving transistor DR in response to the sensing signal. The second transistor T2 stores the voltage in the second capacitor Cst2. In addition, the subpixel SP includes the first switching transistor S1, the second switching transistor S2, the third capacitor Cst3, the driving transistor DR, and the organic light emitting diode D as shown in FIG. 2. The first switching transistor S1 transmits the data signal supplied through the data line DATA to the first capacitor Cst1 and the third capacitor Cst3 in response to the scan signal supplied through the scan line SCAN. Save as. The second switching transistor S2 supplies a high potential voltage in response to the light emission signal supplied through the signal line EM so that the organic light emitting diode D emits light by the driving current generated from the driving transistor DR.

Hereinafter, the configuration of a subpixel according to an embodiment of the present invention will be described in more detail.

3 is a detailed circuit diagram illustrating a subpixel according to an exemplary embodiment of the present invention.

As shown in FIG. 3, a subpixel according to an embodiment of the present invention includes a sensor circuit unit SNP, a first switching transistor S1, a second switching transistor S2, a third capacitor Cst3, and a driving transistor. (DR) and organic light emitting diode (D).

The sensor circuit SNP includes a first transistor T1, a second transistor T2, a first capacitor Cst1, and a second capacitor Cst2. Elements included in the sensor circuit unit SNP are connected as follows. In the first transistor T1, a gate electrode is connected to the sensor wiring SENSE to which the sensing signal Sense is supplied, and a first electrode is connected to the reference voltage wiring REF to which the reference voltage Ref is supplied. The second electrode is connected to the node n1. In the second transistor T2, a gate electrode is connected to the sensor wiring SENSE, a first electrode is connected to the second node n2, and a second electrode is connected to the third node n3. One end of the first capacitor Cst1 is connected to the first node n1 and the other end thereof is connected to the reference voltage wiring REF. One end of the second capacitor Cst2 is connected to the gate electrode of the second transistor T2, and the other end thereof is connected to the third node n3.

The first switching transistor S1, the second switching transistor S2, the third capacitor Cst3, the driving transistor DR, and the organic light emitting diode D are connected as follows. In the first switching transistor S1, a gate electrode is connected to the scan line SCAN to which the scan signal Scan is supplied, and a first electrode is connected to the data line DATA to which the data signal Data is supplied. The second electrode is connected to (n1). In the second switching transistor S2, the gate electrode is connected to the signal line EM to which the light emission signal Em is supplied, and the first electrode is connected to the high potential power line VDD to which the high potential voltage Vdd is supplied. The second electrode is connected to the third node n3. One end of the third capacitor Cst3 is connected to the first node n1 and the other end thereof is connected to the second node n2. In the driving transistor DR, a gate electrode is connected to the second node n2, a first electrode is connected to the third node n3, and a second electrode is connected to the anode electrode of the organic light emitting diode D. In the organic light emitting diode D, an anode electrode is connected to the second electrode of the driving transistor DR, and a cathode electrode is connected to the low potential power wiring VSS to which the low potential voltage Vss is supplied.

The elements included in the subpixel SP according to the exemplary embodiment of the present invention serve as follows. The first transistor T1 serves to set the initial reference voltage Ref on the capacitors Cst1 and Cst3. The second transistor T2 serves as a switch for sensing the threshold voltage of the driving transistor DR. The first switching transistor S1 transfers a data signal supplied through the data line DATA to the first capacitor Cst1 and the third capacitor Cst3. The second switching transistor S2 controls the light emitting period of the organic light emitting diode D. The driving transistor DR generates a driving current corresponding to the data voltage stored in the third capacitor Cst3 and emits the organic light emitting diode D by using the driving current. The first capacitor Cst1 stores the data signal Data as a data voltage and forms a reference voltage Ref on the third capacitor Cst3. The second capacitor Cst2 serves as a coupling capacitor of the second transistor T2 such that the drain electrode of the driving transistor DR is formed to be above a predetermined voltage for sensing the threshold voltage of the driving transistor DR. That is, the second capacitor Cst2 serves to prevent the problem that the threshold voltage of the driving transistor DR is unstable. The third capacitor Cst3 stores the threshold voltage of the driving transistor DR and supplies a driving current corresponding to the sum of the threshold voltage and the data voltage to the gate electrode of the driving transistor DR.

Meanwhile, in the exemplary embodiment of the present invention, the transistors S1, S2, T1, T2, and DR included in the subpixel SP are formed as N-types, but they may be formed as P-types or the like. . In an embodiment of the present invention, the first electrode and the second electrode are used to describe the connection relationship between the transistors S1, S2, T1, T2, and DR included in the subpixel SP. And a drain electrode and may be changed to a drain electrode and a source electrode according to a connection relationship.

Hereinafter, the operation of the subpixel according to an embodiment of the present invention will be described in more detail.

4 is a driving waveform diagram of a subpixel.

As shown in FIG. 3 and FIG. 4, the subpixel according to an embodiment of the present invention operates as a sensing and data voltage storage section, a light emitting section and a non-light emitting section. The time at which the sensing signal Sense_n is supplied is earlier than the time at which the scan signal Scan_n is supplied. The sensing signal Sense is dividedly supplied at least two times during one frame. Therefore, the sensing signal Sense may be supplied twice, three times, N times, etc. as necessary.

When the sensing signal Sense_n is supplied (a logic high divided into two circuits) by being divided into at least two circuits through the sensing wiring SENSE, the first transistor T1 is turned on in response to the sensing voltage. The reference voltage Ref supplied through REF is stored in the first capacitor Cst1 and the third capacitor Cst3 by the first transistor T1. In addition, the second transistor T2 is also turned on in response to the sensing signal Sense_n which is divided into two circuits and switches the gate electrode and the drain electrode of the driving transistor DR to a diode connection state. The threshold voltage of the transistor DR is stored in the third capacitor Cst3 by the second transistor T2. Here, the first sensing signal Sen1 serves to clear the data voltage stored in the subpixel during the previous frame, and the second sensing signal Sen2 serves to accurately sense the threshold voltage of the driving transistor DR. The widths of the first sensing signal Sen1 and the second sensing signal Sen2 may be the same or different. When the widths of the first sensing signal Sen1 and the second sensing signal Sen2 are different from each other, the width of the first sensing signal Sen1 may be longer than the width of the second sensing signal Sen2.

When the scan signal Scan_n is supplied (logic high) through the scan wiring SCAN, the first switching transistor S1 is turned on in response thereto. (Data voltage storage step) In this case, the first switching transistor S1 is supplied through the data wiring DATA. The data signal Data is stored as a data voltage in the first capacitor Cst1 and the third capacitor Cst3. Accordingly, the third capacitor Cst3 finally stores the data voltage in which the data voltage is converged on the first capacitor Cst1 and the threshold voltage of the driving transistor DR stored in the third capacitor Cst3 is converged.

When the emission signal Em_n is supplied (logic high) and the scan signal Scan_n is blocked (logic low) through the signal line EM, the second switching transistor S2 is turned on in response thereto. The high potential voltage Vdd supplied through the first power line VDD is supplied to the driving transistor DR for a time when the second switching transistor S2 is turned on. Accordingly, the driving transistor DR supplies the driving current corresponding to the data voltage stored in the third capacitor Cst3 to the organic light emitting diode D for as long as the second switching transistor S2 is turned on. (D) correspondingly emits light.

In the same manner as described above, after the Nth subpixel operates in the order of sensing, data voltage storage, light emitting, and non-light emitting, the N + 1th subpixel is configured as described above (Sense_n + 1). , Scan_N + 1 and Em_n + 1) operate in the order of sensing and data voltage storage section, light emitting section and non-light emitting section.

Hereinafter, the sensing section and the non-light emitting section will be described in more detail with reference to a simulation waveform diagram.

5 is a simulation waveform diagram of a subpixel according to an embodiment of the present invention.

3 and 5, in the embodiment, the light emitting section is set to 60% and the non-light emitting section is operated to 40% within one frame, and the boundary between the light emitting section and the non-emitting section is defined by the light emitting signal (Em_n). It can be seen that it is defined by). The ratio between the light emitting section and the non-light emitting section may be varied by the light emitting signal Em_n supplied to the second switching transistor S2. In an embodiment, the ratio of the turn-off time and the turn-on time of the second switching transistor S2 may be operated from 1/9 to 9/1 within one frame period. When the ratio of the turn-off time and the turn-on time of the second switching transistor S2 is 1/9, a negative data insertion (NDI) effect of supplying a negative voltage to the transistors included in the subpixel for a relatively short time can be obtained. Will be. If the ratio of the turn-off time and the turn-on time of the second switching transistor S2 is 9/1, NDI can be performed while preventing the flicker.

In the embodiment, it can be seen that the sensing section is made after the non-light emitting section (otherwise, before the light emitting section). Referring to the enlarged drawing of the sensing section, the peak voltage waveforms of the nodes n1 to n3 are shown. Referring to the time point at which the sensing signal Sense_n changes from logic low to logic high, it can be seen that the voltage of the first node n1 converges to the reference voltage Ref of the first transistor T1. The voltage of the third node n3 rises to a high voltage level under the influence of the second capacitor Cst2, which is a coupling capacitor, and then turns to the threshold voltage level of the driving transistor DR by turning on the second transistor T2. It can be seen that it converges. In addition, the voltage of the second node n2 slightly rises in the positive direction under the influence of the parasitic capacitor Cgs of the second transistor T2, and is then equal to the third node n3 by the turn-on of the second transistor T2. It can be seen that the convergence to the threshold voltage level of the driving transistor DR. As the voltages of the nodes n1 to n3 converge as described above, the data voltage corresponding to the threshold voltage of the driving transistor DR is stored in the third capacitor Cst3.

Meanwhile, in the embodiment, the capacitance of the second capacitor Cst2 may be generally 2 to 5 times the capacitance of the capacitor Cgs formed between the gate electrode of the second transistor T2 and the second node n2. When the capacitance of the second capacitor Cst2 is 2 to 5 times the capacitance of the capacitor Cgs described above, the sensing voltage may be set in consideration of the threshold voltage of the driving transistor DR. For example, when the capacitance of the capacitor Cgs is 0.2pF to 0.5pF, the capacitance of the second capacitor Cst2 may be selected to be 0.4pF to 2.5pF.

Hereinafter, the difference of the opening area according to the layout of the unit pixel between an Example and a comparative example is demonstrated.

6 is a layout comparison diagram of a unit pixel constructed by an embodiment of the present invention and a unit pixel constructed by a comparative example.

As shown in FIG. 6, the opening areas of the unit pixels SP1 to SP3 of the embodiment (b) are red and green sub-pixels when compared to the structure of the unit pixels SP1 to SP3 of the 7T1C of the conventional (a). (SP1, SP2) was about 22% wider, and the blue subpixel SP3 was about 32% wider. According to this, it is expected that the number of pixels per inch (ppi) will be lower in the large screen design in the future, so that the opening area can be configured larger.

In addition, in the embodiment, the area of the parasitic capacitor (the area of the drain region and the gate region) formed in the second transistor T2 may be adjusted to form a coupling capacitor, which is the second capacitor Cst2, to further increase the opening area. there was. In addition, the unit pixels SP1 to SP3 of the embodiment (b) may be formed (or added) to a size that the second capacitor Cst2 can accommodate, even when the threshold voltage of the driving transistor DR is shifted to black. By minimizing the luminance at), a contrast ratio could be obtained. In addition, the unit pixels SP1 to SP3 of the embodiment (b) may be designed to sense the corresponding threshold voltage of the driving transistor DR.

The present invention has the effect of providing an organic light emitting display device which can prevent the reduction of the driving current due to the shift of the threshold voltage, achieve the long life of the device and at the same time improve the display quality. In addition, the present invention has the effect of providing an organic light emitting display device that can be configured to clear the previous data voltage and to accurately sense the threshold voltage at least two times to prevent the opening area degradation accompanying the threshold voltage compensation circuit design have. In addition, the present invention has an effect of providing an organic light emitting display device that can improve the problem caused by the shift in the threshold voltage generated when the device based on the amorphous silicon transistor.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be practiced. Therefore, the embodiments described above are to be understood as illustrative and not restrictive in all aspects. In addition, the scope of the present invention is shown by the claims below, rather than the above detailed description. Also, it is to be construed that all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts are included in the scope of the present invention.

1 is a schematic block diagram of an organic light emitting display device according to an embodiment of the present invention;

2 is a schematic configuration diagram of a subpixel;

3 is a detailed circuit diagram illustrating a subpixel according to an embodiment of the present invention.

4 is a drive waveform diagram of a subpixel;

5 is a simulation waveform diagram of a subpixel according to an embodiment of the present invention.

6 is a layout comparison diagram of unit pixels constructed by an embodiment of the present invention and unit pixels constructed by a comparative example.

<Explanation of symbols on main parts of the drawings>

DDRV: Data driver SDRV: Scan driver

PWR: Power Supply PNL: Display Panel

T1: first transistor T2: second transistor

S1: first switching transistor S2: second switching transistor

DR: driving transistor D: organic light emitting diode

SNP: sensor circuit

Claims (12)

A sensor circuit unit including a second capacitor configured to store a reference voltage in the first capacitor in response to a sensing signal divided into at least two circuits and to apply a voltage higher than a threshold voltage of the driving transistor; A first switching transistor configured to store a data signal as a data voltage in the first capacitor and the third capacitor in response to a scan signal; And And a second switching transistor configured to adjust a time period during which a high potential voltage is supplied to the driving transistor in response to a light emission signal. The method of claim 1, The first sensing signal supplied among the sensing signals is a signal for clearing a previous data voltage, and the second sensing signal supplied second is a signal for sensing the threshold voltage of the driving transistor. Display. The method of claim 1, The sensor circuit unit, A first transistor configured to store a low reference voltage for sensing the threshold voltage of the driving transistor in the first capacitor in response to the sensing signal; And a second transistor configured to store the threshold voltage of the driving transistor in the third capacitor in response to the sensing signal. The method of claim 1, The time that the sensing signal is supplied, The organic light emitting display device is characterized in that it is ahead of the time that the scan signal is supplied. The method of claim 3, In the first transistor, a gate electrode is connected to a sensor wiring to which the sensing signal is supplied, a first electrode is connected to a reference voltage wiring to which the reference voltage is supplied, and a second electrode is connected to the first node. The second transistor has a gate electrode connected to the sensor wiring, a first electrode connected to a second node, and a second electrode connected to a third node. In the first switching transistor, a gate electrode is connected to a scan line to which the scan signal is supplied, a first electrode is connected to a data line to which the data signal is supplied, and a second electrode is connected to the first node. In the second switching transistor, a gate electrode is connected to a signal line to which the light emission signal is supplied, a first electrode is connected to a high potential power line to which the high potential voltage is supplied, and a second electrode is connected to the third node. One end of the first capacitor is connected to the first node and the other end is connected to the reference voltage wiring. The second capacitor has one end connected to a gate electrode of the second transistor and the other end connected to the third node. The third capacitor is an organic light emitting display device, characterized in that one end is connected to the first node and the other end is connected to the second node. The method of claim 5, In the driving transistor, a gate electrode is connected to the second node, a first electrode is connected to the third node, and a second electrode is connected to an anode electrode of the organic light emitting diode. And the cathode is connected to a low potential power line to which a low potential voltage is supplied. The method of claim 5, The ratio of turn off time and turn on time of the second switching transistor is An organic light emitting display device, characterized in that 1/9 to 9/1 within one frame section. The method of claim 5, The capacitance of the second capacitor has a capacity of 2 to 5 times the capacitance of the capacitor formed between the gate electrode and the second node of the second transistor. The method of claim 1, The capacity of the second capacitor, An organic light emitting display device, characterized in that 0.4pF ~ 2.5pF. The threshold voltage of the driving transistor is stored in the second capacitor using the second transistor that stores the reference voltage in the first capacitor using the first transistor that is divided into at least two times and responds to the supplied sensing signal. A sensing step of applying a higher voltage and storing a low reference voltage for the threshold voltage sensing of the driving transistor in the first capacitor and the third capacitor; A data voltage storing step of storing a data signal as a data voltage in the first capacitor and the third capacitor by using a first switching transistor in response to a scan signal; And And a light emitting step of controlling a time when a high potential voltage is supplied to the driving transistor by using a second switching transistor in response to a light emitting signal. The method of claim 10, The first sensing signal supplied among the sensing signals is a signal for clearing a previous data voltage, and the second sensing signal supplied second is a signal for sensing the threshold voltage of the driving transistor. Method of driving display device. The method of claim 10, The ratio of turn off time and turn on time of the second switching transistor is A method of driving an organic light emitting display device, characterized in that 1/9 to 9/1 within one frame section.

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