KR20080079364A - Driving circuit of organic light emitting diode, display device comprising thereof and driving method thereof - Google Patents

Abstract

An OLED(Organic Light Emitting Diode) driving circuit, a display apparatus including the same, and a method for driving the same are provided to maintain uniformity of gray scales by changing generation time of a second scan signal during a predetermined time. An OLED(Organic Light Emitting Diode) driving circuit includes a first switch(102), a storing unit(103), an OLED(105), and a second switch(104). The first switch, connected with a data line(100) and a scan line(101), outputs a data signal according to a data signal of the data line and a scan signal of the scan line. The storing unit electrically connected with the first switch stores the data signal outputted from the first switch. The OLED is electrically connected with a power supply unit(106). The second switch connects electrically the OLED and a reference voltage according to the data signal stored in the storing unit.

Description

Organic light emitting diode driving circuit, display device including the same, and driving method therefor {DRIVING CIRCUIT OF ORGANIC LIGHT EMITTING DIODE, DISPLAY DEVICE COMPRISING THEREOF AND DRIVING METHOD THEREOF}

1 is a view showing an organic light emitting diode driving circuit according to an embodiment of the present invention.

2 is a driving timing diagram of an organic light emitting diode driving circuit according to an embodiment of the present invention.

3 illustrates an organic light emitting diode driving circuit according to another embodiment of the present invention.

4 is a driving timing diagram of an organic light emitting diode driving circuit according to another embodiment of the present invention.

(A) to (b) of Figure 5 is the first electrode and the third electrode between the current to the second electrode a second voltage (V _{2 electrodes)} of the _switch is also ideal relationship (I _{1 between the third electrode).}

6 is a conceptual diagram of a display device including an organic light emitting diode driving circuit according to an embodiment of the present invention.

***** Description of the symbols for the main parts of the drawings *****

100: data line

101: scanline

102: first switch

103: storage unit

104: second switch

105: organic light emitting device

Organic light emitting diode (OLED) displays are suitable for realizing thin, low-power display devices because they do not use backlight as well as features of wide viewing angle, high contrast, and fast response. In addition, it is expected to have a wide range of applications because it can be manufactured on a flexible substrate, and can be based on a solution process, which significantly reduces the production cost compared to a liquid crystal display (LCD). Is attracting attention as a next-generation flat panel display that is expected.

The organic light emitting diode display is composed of a self-luminous device driven by a current. An OLED device is formed when an exciton formed by combining electrons and holes injected from a cathode and an anode in an organic layer located between a pair of electrodes falls from an excited state to a ground state. It emits light by energy difference. The luminance of the organic light emitting diode is controlled by the voltage or current applied to the anode and the cathode. In general, the organic light emitting diode device exhibits stable light output characteristics when driven in the constant current mode. Therefore, unlike a liquid crystal display device driven by voltage, a specific pixel structure for driving a current is required.

In order to realize a large area display using an organic light emitting diode, which is a current driving light emitting device, and to increase the life of a single device, an active matrix driving method becomes essential. In the active matrix type driving method, a pixel is stored for each pixel, and a specific pixel in one frame stores a potential for a selected time, and the selected pixel is stored at a specific brightness even during an unselected time of the frame. This is how you keep it. Using such an active matrix driving method, in a display made of a light emitting device such as an organic light emitting diode, the average brightness of the screen can be maintained without excessive load on a single pixel.

In order to realize an active matrix type display, a pixel switching element is necessary. Until now, a thin film transistor (TFT) has been applied as an active matrix switching element of a liquid crystal display (LCD). In general, an amorphous silicon film or a poly silicon film is used to form a current channel of a thin film transistor. In both cases, a relatively low field effect mobility is compared with that of a crystal silicon film. Because of its mobility, the current driving capability of the thin film transistor is inferior. In addition, there is a variation in the field mobility (electron mobility) between the thin film transistors constituting the pixel to maintain the gray-scale uniformity across the screen is a problem facing the current technology.

In order to solve this problem, a thin film transistor driving circuit has been newly proposed. However, in order to overcome the physical limitations of the silicon film of the thin film transistor, the circuit becomes complicated and the aperture ratio of the display increases as the area of the driving circuit becomes wider. Decrease is a problem.

In addition, thin film transistors using silicon-based materials require high temperature processes in order to have sufficient field effect mobility. Therefore, it is difficult to form a thin film transistor of a level suitable for driving an organic light emitting device with a flexible plastic substrate of low cost.

In order to solve this problem, the present invention provides an organic light emitting diode driving circuit having a high aperture ratio and maintaining a gray scale uniformity on a plastic substrate using a conductive switching element, a display device including the same and a driving thereof It is a technical task to provide a method.

The organic light emitting diode driving circuit according to an embodiment of the present invention for achieving the technical problem is electrically connected to the data line and the scan line, the organic light emitting diode driving circuit to the data signal input to the data line and the scan signal input to the scan line A first switch for outputting the data signal, a storage unit electrically connected to the first switch to store the data signal output from the first switch, an organic light emitting element electrically connected to a power supply unit, and the storage unit And a second switch electrically connecting the organic light emitting element and a reference voltage according to the data signal stored in the unit.

The first switch may include a first electrode electrically connected to the data line, a second electrode electrically connected to the scan line and spaced apart from the first electrode, and electrically connected to the storage unit. The third electrode spaced apart from the second electrode and one end may be electrically connected to the first electrode and the other end may include a conductive structure electrically connected to the third electrode according to the difference between the data signal and the scan signal. have.

Here, a dimple may be formed at the other end of the conductive structure.

The mechanical switch may be a micro electro mechanical system (MEMS) switch or a nano elector mechanical system (NEMS) switch.

Here, the second switch is a first electrode electrically connected to the reference voltage, a second electrode electrically connected to the storage unit and spaced apart from the first electrode, and electrically connected to the organic light emitting diode and the first electrode. And a third electrode spaced apart from a second electrode, and a conductive structure having one end electrically connected to the first electrode and the other end electrically connected to the third electrode according to a difference between the reference voltage and the data signal. have.

Here, a dimple may be formed at the other end of the conductive structure.

The mechanical switch may be a micro electro mechanical system (MEMS) switch or a nano elector mechanical system (NEMS) switch.

The first switch or the second switch may be a MOS transistor, a thin film transistor, or an organic field effect transistor (OFET).

The storage unit may include a first terminal electrically connected to the first switch and a second terminal electrically connected to the second switch, and store the data signal.

Here, the storage unit may include one or more capacitors.

Here, at least two second switches may be connected in parallel between the reference voltage and the organic light emitting diode.

Here, the second switch is connected in parallel to two or more, it is preferable that the length of the conductive structure is different from each other.

According to another aspect of the present invention, there is provided a method of driving an organic light emitting diode driving circuit, in which the first switch and the second switch are turned on, and in a state where the second switch is kept on, the first switch is turned off. And the second switch is turned off while the first switch is kept off.

The turning on of the first switch and the second switch may include inputting a first data signal V _data to the _data line and inputting a first scan signal V _scan to the scan line. Preferably, the absolute value of the potential difference between the first data signal V _data and the first scan signal V _scan is equal to or greater than the pull-in voltage V _PI1 of the first switch.

Here, in the state where the first switch is maintained off, the turning off of the second switch may include inputting a second data signal V _ground to the data line and a second scan signal to the scan line. V _reset ), wherein the absolute value of the potential difference between the second data signal V _ground and the second scan signal V _reset is equal to or greater than the pull-in voltage V _PI1 of the first switch. Do.

The method may further include inputting data signals having two or more different sizes to the data line.

Another embodiment of the present invention is a display device including an organic light emitting diode driving circuit according to an embodiment of the present invention.

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

1 is a view showing an organic light emitting diode driving circuit according to an embodiment of the present invention.

As shown in FIG. 1, an organic light emitting diode driving circuit according to an embodiment of the present invention is electrically connected to the data line 100 and the scan line 101 and scanned with a data signal input to the data line 100. The first switch 102 for outputting the data signal in accordance with the scan signal input to the line 101, the storage unit electrically connected to the first switch 102 to store the data signal output from the first switch 102 (103), the organic light emitting element 105 electrically connected to the power supply unit 106 and the agent for electrically connecting the organic light emitting element 105 and the reference voltage 107 in accordance with the data signal stored in the storage 103 Two switches 104.

In the organic light emitting diode driving circuit according to an embodiment of the present invention, the first switch 102 and the second switch 104 are implemented as a mechanical switch including a first electrode, a second electrode, a third electrode, and a conductive structure. However, the present invention is not limited thereto, and any one of the first switch 102 and the second switch 104 is implemented as a mechanical switch, and the other is a MOS transistor, a thin film transistor, or an organic field effect transistor. (Organic Field Effect Transistor, OFET) can be implemented. In addition, both the first switch 102 and the second switch 104 may be implemented with a MOS transistor, a thin film transistor, or an organic field effect transistor.

The first switch 102 is electrically connected to the first electrode electrically connected to the data line 100, the scan electrode 101, the second electrode spaced apart from the first electrode, and the storage 103. A mechanical switch including a third electrode spaced apart from the first electrode and the second electrode, and a conductive structure having one end electrically connected to the first electrode and the other end electrically connected to the third electrode according to a difference between the data signal and the scan signal. Can be. Here, the difference between the data signal and the scan signal means a pull-in voltage of the first switch 102. The pull-in voltage may be defined as a voltage difference between the first electrode and the second electrode required for electrically connecting the first electrode and the third electrode of the first switch 102, which is a mechanical switch.

The other end of the conductive structure may be a dimple of a protruding shape. The structure in which the dimple is formed in the conductive structure is representative of the cantilever and prevents the stiction that may occur during the mechanical switch manufacturing process, and also has the effect of lowering the pull-in voltage (V _PI ).

The storage unit 103 may have a first terminal as an input terminal and a second terminal as an output terminal. The first terminal may be connected to the third electrode of the first switch 102, and the second terminal may be connected to the second electrode of the second switch 104. In this configuration, when the first switch 102 is turned on, the data signal applied to the data line 100 can be transmitted from the first terminal to the second terminal, and then the first switch 102 is Even when turned off, the data signal of the second terminal can be maintained as it is. In general, the storage unit having the above functions while the first terminal and the second terminal are separated may include a dynamic random access memory (DRAM) or a static random access memory (SRAM). Here, the first terminal, which is an input terminal, and the second terminal, which is an output terminal, may be connected to each other to be implemented as one terminal. As a representative example, as illustrated in FIG. 1, the storage unit 103 may be implemented with one capacitor. That is, one end of the storage unit 103 implemented as one capacitor is connected between the first switch 102 and the second switch 104, and the other end is electrically connected to the reference voltage 107, so that the first When the switch 102 is turned on, the data signal input to the data line 100 may be stored. Even after the first switch 104 is turned off, the previously stored data signal may be maintained as it is.

The second switch 104 is a first electrode electrically connected to the reference voltage 107, a third electrode electrically connected between the third electrode of the first switch 102 and the storage 103 and spaced apart from the first electrode. The second electrode, the third electrode electrically connected to the organic light emitting element 105 and spaced apart from the first electrode and the second electrode, and the first end is electrically connected to the first electrode, and the other end is the difference between the reference voltage 107 and the data signal. The mechanical switch may include a conductive structure electrically connected to the third electrode. Here, the difference between the reference voltage 107 and the data signal means a pull-in voltage of the second switch 104. The pull-in voltage may be defined as a voltage difference between the first electrode and the second electrode required for electrically connecting the first electrode and the third electrode of the second switch 104, which is a mechanical switch.

The other end of the conductive structure may be a dimple of a protruding shape.

The organic light emitting element 105 is electrically connected between the third electrode of the second switch 104 and the power supply 106, and when the second switch 104 is turned on, the first electrode of the second switch 104 is turned on. Light is emitted in response to a difference between the reference voltage 107 formed across the organic light emitting element 105 and the power voltage supplied from the power supply unit 106 by the reference potential connected to the current. However, the present invention is not limited thereto, and any element may emit light by an input power signal (drive voltage or drive current).

2 is a driving timing diagram of an organic light emitting diode driving circuit according to an embodiment of the present invention. More specifically, it is a timing diagram showing a specific driving method for expressing gray scale by using a pulse width modulation (PWM) method using an organic light emitting diode driving circuit according to an embodiment of the present invention.

In a driving method of operating an organic light emitting diode driving circuit according to an embodiment of the present invention, the first switch 102 and the second switch 104 are turned on, and the second switch 104 is kept on. The first switch 102 is turned off, and the second switch 104 is turned off while the first switch 102 remains off.

<Step 1 in which the first switch 102 and the second switch 104 are turned on>

The data line 100 and the scan line 101 maintain a stand by potential when an image signal is not input. In order to select a specific pixel of the display by inputting an image signal, an arbitrary first data signal V _data different from the standby potential is input to the data line 100, and the first line is input to the scan line 101. Input the scan signal (V _scan ). Here, the absolute value of the potential difference between the first data signal V _data and the first scan signal V _scan is equal to or greater than the pull-in voltage V _PI1 of the first switch 102. The first scan signal V _scan having a different sign from the data signal V _data is input. As a result, since the potential difference between the first electrode and the second electrode of the first switch 102 becomes equal to or greater than the pull-in voltage V _PI1 of the first switch, the electrostatic force of the first switch 102 The conductive structure is moved toward the third electrode, and mechanical contact between the first electrode and the third electrode is made. That is, the first switch 102 is turned on during the T1 time.

At the same time, the first data signal V _data1 of the data line 100 is output to the second electrode of the storage unit 103 and the second switch 104, and is input to the second electrode of the second switch 104. The absolute value of the potential difference between the potential of the first data signal V _data and the reference voltage 107 electrically connected to the first electrode of the second switch 104 is greater than or equal to the pull-in voltage V _PI2 of the second switch 104. In this case, the second switch 104 is also turned on during the time T1, and the organic light emitting element 105 emits light by a power signal (driving voltage or driving current) provided from the power supply unit 106.

<Step 1 in which the first switch 102 is turned off while the second switch 104 is kept on.>

While selecting pixels other than the selected pixel, the first scan signal V _scan of the scan line 101 of the selected pixel is returned to the standby potential, and the first data signal V _data of the data line 100 is also in the standby potential. Return to. As a result, since the potential difference between the first electrode and the second electrode of the first switch 102 does not maintain the pull-in voltage V _PI1 or more, the conductive structure contacted to the third electrode is spaced apart from the third electrode. That is, the first switch 102 is turned off.

And, both ends of the potential (V _CAP) of the capacitor first data signal storage unit 103 by the potential of (V _data) to be stored in the storage unit 103 is maintained at the potential of the first data signal (V _data) . Accordingly, the second switch 104 is maintained in an on state, and the organic light emitting element 105 emits light by a power signal (drive voltage or drive current) provided from the power supply unit 106 during the T3 time.

 <Step in which second switch 104 is turned off while first switch 102 remains off>

In order to express gray scale by PWM (Pulse Width Modulation) method, the organic light emitting device 105 emitting light at a suitable time should be turned off. That is, the second switch 104 needs to be turned off. To this end, the second data signal V _ground is input to the data line 100, and the second scan signal V _reset , which is a reset signal, is input to the scan line 101. Here, the second data signal V _ground may be a signal corresponding to a ground potential, or a negative or positive potential signal having an appropriate value may be input. In addition, a second scan signal (V _reset) and a second data signal (V _ground) the second data signal (V _ground) the absolute value of the potential difference is such that the pull-in voltage (V _PI1) over the first switch 102 of the Each of the second scan signals V _reset is input. Here, it is preferable that the second scan signal V _reset is a signal having a potential larger than that of the second data signal V _ground . As a result, the first data signal V _data1 stored in the storage unit 103 is discharged, whereby the absolute value of the potential difference between the first electrode and the second electrode of the second switch 104 is reduced. It falls below the pull-in voltage V _PI2 and the second switch 104 is turned off. Therefore, the organic light emitting diode 105 does not receive the driving voltage or the driving current from the power supply 106 during the T4 time and thus does not emit light.

As a result, the organic light emitting diode driving circuit according to an embodiment of the present invention can change the timing of the generation of the second scan signal V _reset for a limited time, thereby freeing the ratio of T3 and T4. And uniformity of gray scale can be maintained. In addition, a micro electro mechanical system (MEMS) switch is generally made of a uniform conductive material, and it is sufficient to have a length and width of several tens of micrometers to satisfy a high aperture ratio on a pixel. Can be.

3 is a diagram illustrating an organic light emitting diode driving circuit according to another exemplary embodiment of the present invention.

As shown in FIG. 3, an organic light emitting diode driving circuit according to another embodiment of the present invention is compared with an organic light emitting diode driving circuit according to an embodiment of the present invention shown in FIG. 1, and at least two second switches. 304 is electrically connected between the organic light emitting element 305 and the reference voltage 307 in parallel. More specifically, the first electrodes of the second switches 304 are electrically connected to the reference voltage 307, and the second electrode is electrically connected between the first switch 302 and the storage unit 303. The three electrodes are electrically connected to the organic light emitting element 305. Here, the lengths of the conductive structures of the second switches 304 are different from each other.

Accordingly, the organic light emitting diode driving circuit according to another embodiment of the present invention may include two or more second switches including data signals having different potential values input to the data line 300 and conductive structures having different lengths. 304, gray scales may be expressed by an AM (Amplitude Modulation) method.

4 is a driving timing diagram of an organic light emitting diode driving circuit according to another embodiment of the present invention. More specifically, it is a timing diagram showing a specific driving method for expressing gray scale by an AM (Amplitude Modulation) method using an organic light emitting diode driving circuit according to another embodiment of the present invention. 5A to 5B are ideal relationship diagrams of the current between the first electrode and the third electrode (between I _{1-3 electrodes} ) with respect to the second electrode voltage (V _{2 electrode} ) of the second switch.

In order to express gray scale by an AM (Amplitude Modulation) method, a voltage (V _{2 electrode} ) applied to the second electrode of the second switch 304 and the current I ₁ flowing between the first electrode and the third electrode (I _1). Any one can be used as _long as the relation _{between the -3 electrodes} has the characteristics as shown in Figs. 5A to 5B. In particular, in Figure 4 will be described in detail below using a mechanical second switch 304 having the same characteristics as in Figure 5 (a).

First, the first scan signal (V _scan) to the first tone input the first data signal (V _data1) corresponding with, and the scan line 301 to the data line 300 to represent the first gray level in the selected pixel Enter. Here, the first scan signal V _scan is a data signal V _datamax having a potential equal to or larger than the largest data signal V _{data n} among the n data signals V _data1 to V _datan to be input to the data line 300. ) Is a signal obtained by subtracting the pull-in voltage V _PI1 of the first switch 302. The first data signal V _data1 and the first scan signal V _SCAN are preferably signals having different signs. As a result, the first switch 302 and the second switch 304a are turned on. The potential of the first data signal V _data1 input to the data line 300 is stored in a capacitor which is a storage unit 303, so that the second switch 304a may be turned off even if the first switch 302 is later turned off. Can remain on. Accordingly, a first specific current (low current) for determining the brightness of the organic light emitting element 305 flows through the second switch 304a to express the first gray level in the selected pixel.

Next, in order to change the selected pixel from the first gray level to the second gray level, the second data signal V _data2 corresponding to the second gray level is input to the data line 300, and the first scan is input to the scan line 301. Input the signal (V _scan ). As a result, the first and second switches 304a and 305b are turned on. In addition, since the potential of the second data signal V _data2 applied to the data line 300 is stored in the capacitor of the storage unit 303, the second switch 304a, even if the first switch 302 is later turned off. 304b) may remain on. Therefore, a second specific current (high current) for determining the brightness of the organic light emitting element 305 flows through the second switches 304a and 304b to change the selected pixel from the first gray level to the second gray level. I can express it.

In the same principle, the gray level of the selected pixel may be variously changed according to various data signals input to the data line 300.

In order to express gray scale by an AM (Amplitude Modulation) method, the organic light emitting diode 305 that emits light at a suitable time should be turned off. That is, the second switch 304 should be turned off. The method of turning off the second switch 304 is a second method for expressing gray scale in a pulse width modulation (PWM) method of the method of driving an organic light emitting diode driving circuit according to an embodiment of the present invention. Since the driving principle is the same as the method of turning off the switch 104, the description thereof will be omitted.

6 is a conceptual diagram of a display device including an organic light emitting diode driving circuit according to an embodiment of the present invention.

As shown in FIG. 6, a display device according to another embodiment of the present invention includes an organic light emitting diode driving circuit 602 according to an embodiment of the present invention.

According to another exemplary embodiment, a display apparatus includes a plurality of data lines 600, a plurality of scan lines 600 and a plurality of data lines 600 that intersect the plurality of data lines 600. A plurality of organic light emitting diode driving circuits 602 are formed in a region where the plurality of scan lines 601 intersect.

As described above, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without changing the technical spirit or essential features. Therefore, the exemplary embodiments described above are to be understood as illustrative and not restrictive in all respects, and the scope of the present invention is indicated by the following claims rather than the detailed description, and the meaning and scope of the claims and All changes or modifications derived from the equivalent concept should be interpreted as being included in the scope of the present invention.

As described in detail above, according to the present invention, an active matrix organic light emitting diode driving circuit which maintains a constant gray scale uniformity of a display on a flexible plastic substrate and has a high aperture ratio, It is possible to provide a display device and a driving method thereof.

Claims (17)

A first switch electrically connected to a data line and a scan line and outputting the data signal according to a data signal input to the data line and a scan signal input to the scan line; A storage unit electrically connected to the first switch and storing the data signal output from the first switch; An organic light emitting device electrically connected to a power supply unit; And A second switch electrically connecting the organic light emitting element and a reference voltage according to the data signal stored in the storage unit; Organic light emitting diode driving circuit comprising a. The method of claim 1, The first switch, A first electrode electrically connected to the data line; A second electrode electrically connected to the scan line and spaced apart from the first electrode; A third electrode electrically connected to the storage unit and spaced apart from the first electrode and the second electrode; And One end is electrically connected to the first electrode, and the other end is electrically connected to the third electrode according to the difference between the data signal and the scan signal. Mechanical switch comprising a organic light emitting diode drive circuit. The method of claim 2, An organic light emitting diode driving circuit having a dimple formed at the other end of the conductive structure. The method of claim 2, The mechanical switch, An organic light emitting diode drive circuit, which is a Micro Electro Mechanical System (MEMS) switch or a Nano Elector Mechanical System (NEMS) switch. The method of claim 1, The second switch, A first electrode electrically connected to the reference voltage; A second electrode electrically connected to the storage and spaced apart from the first electrode; A third electrode electrically connected to the organic light emitting device and spaced apart from the first electrode and the second electrode; And One end is electrically connected to the first electrode, and the other end is electrically connected to the third electrode according to the difference between the reference voltage and the data signal. Mechanical switch comprising a organic light emitting diode drive circuit. The method of claim 5, An organic light emitting diode driving circuit having a dimple formed at the other end of the conductive structure. The method of claim 5, The mechanical switch, An organic light emitting diode drive circuit, which is a Micro Electro Mechanical System (MEMS) switch or a Nano Elector Mechanical System (NEMS) switch. The method of claim 1, The first switch or the second switch, An organic light emitting diode driving circuit which is a MOS transistor, a thin film transistor, or an organic field effect transistor (OFET). The method of claim 1, The storage unit, A first terminal electrically connected to the first switch; And A second terminal electrically connected to the second switch And an organic light emitting diode driving circuit capable of storing the data signal. The method of claim 1, The storage unit, An organic light emitting diode driving circuit comprising one or more capacitors. The method of claim 1, At least two second switches are connected in parallel between the reference voltage and the organic light emitting element. The method of claim 5, The second switch is The organic light emitting diode driving circuit of two or more connected in parallel, the length of the conductive structure is different. In the driving method for operating the organic light emitting diode driving circuit according to claim 1, Turning on the first switch and the second switch; The first switch is turned off while the second switch is kept on; And The second switch is turned off while the first switch remains off A driving method of an organic light emitting diode driving circuit comprising a. The method of claim 13, The step of turning on the first switch and the second switch, Inputting a first data signal (V _data ) to the data line; And Inputting a first scan signal V _scan to the scan line Wherein the absolute value of the potential difference between the first data signal (V _data ) and the first scan signal (V _scan ) is equal to or greater than the pull-in voltage (V _PI1 ) of the first switch. . The method of claim 14, And inputting data signals having two or more different magnitudes into the data line. The method of claim 13, In the state where the first switch is maintained off, the second switch is turned off, Inputting a second data signal V _ground to the data line; And Inputting a second scan signal V _reset to the scan line; A method of driving an organic light emitting diode driving circuit comprising: a absolute value of a potential difference between the second data signal (V _ground ) and the second scan signal (V _reset ) is equal to or greater than the pull-in voltage (V _PI1 ) of the first switch. . A display device comprising the organic light emitting diode driving circuit according to claim 1.

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