KR20150064545A - Organic light emitting diode display device and method for driving the same - Google Patents

Abstract

An organic light emitting diode display device according to an embodiment of the present invention comprises: a first transistor applying data voltage of reference voltage to a source electrode and supplying the data voltage or the reference voltage to a first node depending on scan signals; a driving transistor connecting a gate electrode to the first node, the source electrode to a second node, and a drain electrode to a fourth node; a first capacitor connected between the first and second nodes and storing threshold voltage of the driving transistor; a second transistor supplying high conductive power voltage applied to a third node connected to the source electrode to the second node depending on light emitting control signals; and an organic light emitting diode connecting the anode to the fourth node and applying the high conductive power voltage or low conductive power voltage to the cathode.

Description

Technical Field [0001] The present invention relates to an organic light emitting diode (OLED) display device,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device, and more particularly, to an organic light emitting diode display device and a driving method thereof.

As the information society has developed, the demand for the display field has increased in various forms. In response to this demand, various flat panel display devices having characteristics such as thinning, light weight, and power consumption reduction have been developed. For example, A liquid crystal display device, a plasma display panel device, and an organic light emitting diode display device have been studied.

In particular, an organic light emitting diode display device, which has been actively studied in recent years, can display an image by displaying a different gray scale by applying a data voltage (Vdata) of various sizes to each pixel.

To this end, each pixel includes an organic light emitting diode and a driving transistor, which are current control elements, and one or more capacitors. In particular, the current flowing through the organic light emitting diode is controlled by the driving transistor, the threshold voltage deviation of the driving transistor, and the amount of current flowing through the organic light emitting diode vary depending on various parameters, thereby causing uneven brightness of the screen.

However, the threshold voltage deviation of the driving transistor occurs due to the characteristics of the driving transistor being changed according to manufacturing process parameters of the driving transistor. To solve this problem, a plurality of transistors and capacitors Lt; RTI ID = 0.0 > a < / RTI >

On the other hand, as consumer expectations for large area displays increase, the need for large area organic light emitting diode display devices is increasing. To this end, the compensation circuitry needs to reduce the number of transistors, capacitors, and wires in addition to compensating for threshold voltage deviation for large areas.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an organic light emitting diode display device and a method of driving the same that are capable of compensating for a threshold voltage deviation and a high potential power supply voltage deviation.

According to an aspect of the present invention, there is provided an organic light emitting diode display device including a source electrode to which a data voltage or a reference voltage is applied, and supplies the data voltage or the reference voltage to a first node according to a scan signal A first transistor; A driving transistor having a gate electrode connected to the first node, a source electrode connected to the second node, and a drain electrode connected to the fourth node; A first capacitor coupled between the first node and the second node, the first capacitor storing a threshold voltage of the driving transistor; A second transistor for supplying a high potential power supply voltage applied to a third node connected to the source electrode to the second node according to a light emission control signal; And an organic light emitting diode having an anode electrode connected to the fourth node and a high potential power supply voltage or a low potential power supply voltage applied to the cathode electrode.

According to another aspect of the present invention, there is provided a method of driving an organic light emitting diode (OLED) display device, including a first transistor, a second transistor, a driving transistor, first and second capacitors, and an organic light emitting diode A source electrode of the driving transistor, a source electrode of the driving transistor, and a source electrode of the driving transistor are connected to each other through a first node, a drain electrode of the first transistor, a gate electrode of the driving transistor, A drain electrode of the second transistor and the other end of the first capacitor are connected to each other, a source electrode of the second transistor and the other end of the second capacitor are connected through a third node, The drain electrode of the driving transistor and the anode electrode of the organic light emitting diode are connected, and the first and second While the transistor is turned on, and further comprising: a reference voltage to the source electrode of the first transistor is, initializing the voltage of the first node with the reference voltage; Storing a threshold voltage of the driving transistor in the first capacitor while the first transistor is turned on and the second transistor is turned off; Supplying a data voltage to the source electrode of the first transistor while the first transistor is turned on and the second transistor is turned off and supplying the data voltage to the first node; And emitting the organic light emitting diode according to the data voltage and the reference voltage while the first transistor is turned off and the second transistor is turned on.

According to the embodiments of the present invention, the deviation of the threshold voltage and the deviation of the high-potential power supply voltage due to the IR drop according to the operating state of the driving transistor are compensated to thereby maintain the current flowing through the organic light- There is an effect that can be done.

FIG. 1 is a schematic view illustrating a configuration of an organic light emitting diode display according to embodiments of the present invention; FIG.
FIG. 2 schematically shows an equivalent circuit of the subpixel shown in FIG. 1; FIG.
3 is a timing diagram according to one embodiment of the control signals supplied to the equivalent circuit shown in FIG. 2;
Figure 4 illustrates the timing diagram shown in Figure 3;
FIGS. 5A through 5E are views for explaining a method of driving an organic light emitting diode display according to embodiments of the present invention; FIGS. And
FIG. 6 and FIG. 7 are experimental data for explaining a threshold voltage deviation and a change in current according to a change in a high-potential power supply voltage of an organic light emitting diode display according to embodiments of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a schematic view illustrating a configuration of an organic light emitting diode display according to embodiments of the present invention. Referring to FIG.

1, an organic light emitting diode display 100 according to embodiments of the present invention includes a panel 110, a timing controller 120, a scan driver 130, and a data driver 140 .

The panel 110 includes sub-pixels SP arranged in a matrix form. The subpixels SP included in the panel are supplied with a scan signal supplied from the scan driver 130 through the plurality of scan lines SL1 to SLm and a plurality of data lines DL1 to DLn from the data driver 140, And emits light according to a data signal supplied through the data lines. In addition, the subpixels SP can be controlled to emit light by not only a scan signal and a data signal but also a light emission control signal supplied from a scan driver 130 through a plurality of light emission control lines (not shown).

To this end, an organic light emitting diode and a plurality of transistors and capacitors for driving the organic light emitting diode are formed in one subpixel. The detailed configuration of the sub-pixel SP will be described in detail with reference to FIG.

The timing control unit 120 receives a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a data enable signal DE, a clock signal CLK, and a video signal from the outside. In addition, the timing controller 120 generates image data (R, G, B) in digital form by arranging image signals inputted from the outside in frame units.

For example, the timing controller 120 controls the scan driver 130 and the scan driver 130 using timing signals such as a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a data enable signal DE, and a clock signal CLK. And controls the operation timing of the data driver 140.

To this end, the timing controller 120 generates a gate control signal GCS for controlling the operation timing of the scan driver 130 and a data control signal DCS for controlling the operation timing of the data driver 140.

The scan driver 130 generates a scan signal Scan so that the transistors included in the subpixels SP included in the panel 100 can operate according to the gate control signal GCS supplied from the timing controller 120 And supplies the generated scan signal Scan to the panel 100 through the scan lines SL. The scan driver 120 generates a light emission control signal Em as a kind of a scan signal and supplies the generated light emission control signal Em to the panel 100 through emission control lines (not shown). Hereinafter, a scan signal applied through the nth scan line among the scan lines is assumed as Scan [n].

The data driver 140 generates data signals R, G and B and data control signals DCS supplied from the timing controller 120 and outputs the generated data signals to the data lines DL. To the panel (110).

Hereinafter, the detailed configuration of subpixels will be described in detail with reference to FIGS. 1 and 2. FIG.

FIG. 2 is a schematic view showing an equivalent circuit of the sub-pixel shown in FIG.

2, each sub-pixel SP includes first and second transistors T1 and T2, a driving transistor Tdr, first and second capacitors C1 and C2, and an organic light emitting diode OLED ).

The first and second transistors T1 and T2 and the driving transistor Tdr are PMOS type transistors as shown in FIG. 2. Alternatively, the NMOS transistors may be PMOS type transistors, The transistor for turning on the transistor has the opposite polarity to the voltage for turning on the transistor of the NMOS type.

A data voltage Vdata or a reference voltage Ref is applied to the source electrode of the first transistor T1 and a scan signal Scan [n] is applied to the gate electrode of the first transistor T1. The drain electrode is connected to the first node N1 To the gate electrode of the driving transistor Tdr. Here, it is assumed that the scan signal " Scan [n] " is the n-th scan signal applied through the n-th scan line of the plurality of scan lines.

For example, the data voltage Vdata or the reference voltage Ref is applied to the source electrode of the first transistor T1 through the data line DL, and the first transistor T1 is connected to the scan line SL The operation can be controlled according to the supplied scan signal Scan [n].

Accordingly, the first transistor Tl may be turned on according to the scan signal Scan, and may supply the data voltage Vdata or the reference voltage Ref to the first node N1 every frame. For example, the reference voltage Ref may be a direct-current voltage of a predetermined magnitude, and the data voltage Vdata may be a different continuous voltage per one horizontal period (1H).

Meanwhile, when the reference voltage Ref is applied to the first node N1, the first transistor T1 applies the first node N1 voltage, which is connected to the gate electrode of the driving transistor Tdr, to the reference voltage Ref ).

Next, the high-level power supply voltage VDD is applied to the third node N3 connected to the source electrode of the second transistor T2, the emission control signal Em [n] is applied to the gate electrode, The electrode is connected to the source electrode of the driving transistor Tdr through the second node N2.

For example, when the high voltage source VDD is applied to the third node N3 and the second transistor T2 is turned on according to the emission control signal Em [n] supplied through the emission control line The third node N3 and the second node N2 may be connected to each other and the high potential power supply voltage VDD may be applied to the second node N2. Accordingly, the second transistor T2 may perform a function of initializing the second node N2 connected to the source electrode of the driving transistor to the high potential power supply voltage VDD.

Next, the first capacitor C1 is connected between the first node N1 and the second node N2.

For example, the first capacitor C1 serves to sense the threshold voltage Vth of the driving transistor Tdr. Specifically, the threshold voltage of the driving transistor may be stored in the first capacitor C1 .

Next, the second capacitor C2 is connected between the third node N3 and the second node N2 to which the high-potential power supply voltage VDD is applied.

For example, when the second transistor T2 is turned off by the emission control signal Em [n] and the third node N3 and the second node N2 are disconnected, the second capacitor C2 may be continuously applied to the third node N3 connected to one end thereof.

Next, the gate electrode of the driving transistor Tdr is connected to the first node N1, the source electrode thereof is connected to the second node N2, and the drain electrode is connected to the organic light emitting diode OLED ").

On the other hand, the amount of current flowing through the organic light emitting diode OLED to be described later is the sum (Vsg + Vth) of the voltage Vsg between the source electrode and the gate electrode of the driving transistor Tdr and the threshold voltage Vth of the driving transistor Tdr, And can be finally determined by the compensation circuit by the data voltage Vdata and the reference voltage Ref.

Therefore, since the amount of current flowing in the organic light emitting diode OLED is proportional to the size of the data voltage Vdata, the organic light emitting diode display according to the embodiments of the present invention can display data voltages (Vdata) is applied to display an image by displaying different gradations.

Next, the anode electrode of the organic light emitting diode OLED is connected to the fourth node N4, and a low potential power supply voltage VSS or a high potential power supply voltage VDD is applied to the cathode electrode.

Hereinafter, the operation of each subpixel included in the organic light emitting diode display according to embodiments of the present invention will be described in detail with reference to FIG. 3 and FIGS. 5A to 5E.

FIG. 3 is a timing diagram according to one embodiment of the control signals supplied to the equivalent circuit shown in FIG. 2, and FIGS. 5A to 5E illustrate a method of driving the organic light emitting diode display according to embodiments of the present invention FIG.

3, the organic light emitting diode display according to embodiments of the present invention is divided into a scan period and an emission period. The scan period is an initial period (t1), a sensing period (t2), a sampling period (t3), and a holding period (t4).

5A to 5E, the high-potential power-supply voltage VDD applied to the third node N3 is divided by the IR drop generated due to the wiring resistance applied to the high-potential power-supply voltage It is assumed that the high-potential power supply voltages VDD1, VDD2, VDD3, VDD4, and VDD5 during the respective periods have different values.

During the initialization period t1, a low level scan signal Scan [n] and a light emission control signal Em [n] are applied as shown in FIG. 3, The reference voltage Ref is applied through the data line and the low potential power supply voltage VSS is applied to the cathode electrode of the organic light emitting diode OLED.

5A, the first transistor T1 is turned on by the low level scan signal Scan [n] and the second transistor T2 is turned on by the low level emission control signal Em [n] [n]).

In addition, since the first transistor T1 is turned on, the reference voltage Ref applied to the source electrode of the first transistor T1 through the data line is supplied to the first node N1, Is initialized to the reference voltage Ref. Since the second transistor T2 is turned on, the high-level power supply voltage VDD1 applied to the third node N3, which is the source electrode of the second transistor T2, is connected to the source electrode of the driving transistor Tdr And is supplied to the second node N2. Thus, the voltage of the second node N2 is initialized to the high potential supply voltage VDD1.

For example, during the initialization period t1, although the current flows through the organic light emitting diode OLED, since the initialization period t1 is a very short period corresponding to one horizontal period (1H), the organic light emitting diode OLED The light emitted is not recognized by the viewer's eyes. However, the voltage at the first node N1 connected to the gate electrode of the driving transistor Tdr may be initialized to the reference voltage Ref.

The voltage of the first node N1 connected to the gate electrode of the driving transistor Tdr becomes equal to the reference voltage Ref which is a constant DC voltage during the initialization period t1 because the first transistor T1 is turned on Is initialized.

Next, during a sensing period t2, a low level scan signal Scan [n] and a high level emission control signal Em [n] are applied as shown in FIG. 3, The reference voltage Ref is applied to the source electrode of the transistor T1 through the data line and the low potential power supply voltage VSS is applied to the cathode electrode of the organic light emitting diode OLED.

5B, the first transistor T1 is turned on by the low level scan signal Scan [n], the second transistor T2 is turned on by the high level emission control signal Em [n]).

As the first transistor T1 maintains the turn-on state, the reference voltage Ref applied to the source electrode of the first transistor T1 through the data line is supplied to the first node N1, One node voltage maintains the reference voltage (Ref). Since the second transistor T2 is turned off and the direct connection between the second node N2 and the third node N3 is cut off, the high-potential power supply voltage VDD2 is supplied to the first node To the third node N3.

For example, during the sensing period t2. The first node voltage maintains the reference voltage Ref but the direct connection between the second node N2 and the third node N3 is cut off as the second transistor T2 is turned off, the voltages stored in the first and second capacitors C1 and C2 are discharged while the voltage of the second node N2 is higher than the voltage of the second node N2, (VDD1).

As a result, during the sensing period t2, the voltage of the second node N2 gradually decreases to a voltage lower than the high potential power supply voltage VDD1, and the voltage of the first node N1 connected to the gate electrode of the driving transistor Tdr To a voltage Ref + | Vth | which is larger than the absolute value | Vth | of the threshold voltage Vth of the driving transistor Tdr, which is the reference voltage Ref. Therefore, at the time when the sensing period t2 is completed, the threshold voltage of the driving transistor is stored in the first capacitor C1.

This is because the drive transistor Tdr is connected in the source follower manner and therefore the voltage at the second node N2 which is the source electrode of the drive transistor Tdr is reduced and the drive transistor Tdr is driven until the drive transistor Tdr is turned off (Ref + | Vth |) which is larger than the reference voltage Ref which is the gate electrode voltage of the transistor Tdr by the absolute value of the driving transistor threshold voltage Vth (| Vth |).

Therefore, during the sensing period t2, the first capacitor C1 functions to sense the threshold voltage Vth of the driving transistor.

Next, during the sampling period t3, the scan signal Scan [n] of the low level and the first and second emission control signals Em [n], H the data voltage Vdata [n] is applied to the source electrode of the first transistor T1 through the data line and the high potential power supply voltage VDD [n] is applied to the cathode electrode of the organic light emitting diode OLED Is applied.

5C, the first transistor T1 is turned on by the low level scan signal Scan [n], and the second transistor T2 is turned on by the high level emission control signal Em [n] [n]).

Also, as the first transistor T1 is turned on, the data voltage Vdata [n] applied to the source electrode of the first transistor T1 through the data line is supplied to the first node N1. Since the second transistor T2 maintains the turn-off state, the high-level power supply voltage VDD3 is continuously supplied to the third node N3, which is one end of the second capacitor C2. Also, as the high potential power supply voltage VDD is applied to the cathode electrode of the organic light emitting diode, the light emission of the organic light emitting diode OLED is turned off.

For example, during the sensing period t2, the reference voltage Ref is supplied to the first node N1, which is one end of the first capacitor C1, and is supplied to the first node N1 during the sampling period t3. As the data voltage Vdata [n] is supplied, the voltage at the second node N2, which is the other end of the first capacitor C1, also changes. However, the voltage stored across the first capacitor Cl remains constant Since the first and second capacitors are connected in series, the voltage of the second node N2 is determined by the ratio of the capacitances c1 and c2 of the first and second capacitors.

Specifically, the second node voltage is a sum of the second node voltage Ref + | Vth | and the first node voltage change amount Vdata [n] - Ref during the sensing period t2 and the capacitance of the first and second capacitors (Ref + | Vth | c2) by the ratio (c1 / (c1 + c2) + {c1 / (c1 + c2)} (Vdata [n] - Ref)

Therefore, the first capacitor is connected to both ends of the (C1) capacitor by a combination of "Vdata [n] - [Ref + | Vth | + {c1 / (c1 + c2)} (Vdata [n] - Ref)]. In other words, the voltage VC1 stored at both ends of the first capacitor C1 becomes {c2 / (c1 + c2)} (Vdata [n] - Ref) - | Vth |

This is because when the current Ioled flowing through the organic light emitting diode OLED is a peak because the ratio of the capacitances of the first capacitor and the second capacitor affects the current Ioled flowing in the organic light emitting diode OLED to be described later A larger data voltage is required than in the case where the capacitance ratio is not influenced, so that the resolution of the current Ioled flowing in the organic light emitting diode according to the data voltage can be improved.

As a result, during the sampling period t3, the first capacitor serves to sample the data voltage required for the organic light emitting diode OLED to emit light during the light emission period t5.

During the holding period t4, the high level scan signal Scan [n] is applied and the emission control signal Em [n], which changes from high level to low level, The nth data voltage Vdata [n] is applied to the source electrode of the first transistor Tl through the data line, and the nth data voltage Vdata [n] is applied to the source electrode of the first transistor Tl through the data line. (Vdata [n + 1], Vdata [n + 2], ..., Vdata [m]) and the reference voltage Ref are successively applied.

5D, the first transistor T1 is turned off by the high level scan signal Scan [n], and the second transistor T2 is turned off from the high level to the low level The control signal Em [n] changes from the turn-off state to the turn-on state.

The data voltages Vdata [n + 1], Vdata [n + 2], ..., Vdata [m] after the nth data voltage Vdata [n] May be applied until it changes from a high level to a low level.

This is because the data voltage information stored in the first capacitor C1 during the sampling period t3 until the second transistor T2 is turned on while the high level scan signal Scan [n] is turned off It must be kept constant.

Also, the organic light emitting diode OLED can be maintained in the OFF state as the voltage Vc of the cathode electrode of the organic light emitting diode maintains the high potential power supply voltage VDD during the holding period t3.

Accordingly, the organic light emitting diode included in the organic light emitting diode display according to embodiments of the present invention does not start emitting light after sampling of each scan line is completed every frame, but sampling of all scan lines is sequentially completed The holding period is maintained until the sampling of all the scan lines is completed and then the light emission starts at once.

In other words, a more detailed description will be given with reference to FIG. 4, in which all the scan lines are started to emit light at a time after completing the scan.

FIG. 4 illustrates the timing diagram of FIG. 3. Assuming that the number of scan lines of the organic light emitting diode display device according to the embodiments of the present invention is m, the first, second, Scan [1], Scan [2], Scan [n] and Scan [m] are applied as scan signals to the nth and mth scan lines, and the first data voltage Vdata [ ) To the m-th data voltage Vdata [m].

Here, during a scan period in which data voltages are applied, an initial period t1, a sensing period t2, a sampling period t3, and a holding period t4).

Therefore, the second transistor included in each sub-pixel is maintained in a turned-off state by all the emission control signals Em until sampling of the corresponding data voltage is completed for each scan line, and the cathode voltage of the organic light emitting diode The organic light emitting diode can emit light during the holding period t3 as the voltage Vc is maintained at the high potential power supply voltage VDD.

Thereafter, the second transistor included in each sub-pixel is turned on by all of the emission control signals Em [1] to Em [m], and finally the cathode electrode voltage Vc of the organic light emitting diode becomes low The organic light emitting diode (OLED) of the subpixel connected to each scan line starts light emission while changing to the power supply voltage.

During a light emission period t5, a high level scan signal Scan [n] and a low level emission control signal Em [n] are applied as shown in FIG. 3, The reference voltage Ref is applied to the source electrode of the transistor T1 through the data line and the low potential power supply voltage VSS is applied to the cathode electrode of the organic light emitting diode OLED.

5E, the first transistor T1 is turned off by the high level scan signal Scan [n], and the second transistor T2 is turned off by the low level emission control signal Em [n]) and the reference voltage Ref is applied to the source electrode of the first transistor T1 through the data line. However, since the first transistor is turned off by the scan signal of the high level, It has no effect on the voltage. The second transistor T2 is turned on so that the high potential power supply voltage VDD5 is directly supplied to the third node N3 and the low potential power supply voltage VSS is applied to the cathode electrode of the organic light emitting diode OLED The light emission of the organic light emitting diode OLED starts.

Therefore, the current Ioled flowing through the organic light emitting diode OLED can be determined by the current flowing in the driving transistor Tdr, and the current flowing through the driving transistor is the voltage Vgs between the gate electrode and the source electrode of the driving transistor, Is determined by the threshold voltage (Vth) of the transistor, and can be defined by the following Equation (1). On the other hand, the voltage at the first node N1, which is the gate electrode of the driving transistor Tdr, becomes "VDD5 + {c2 / (c1 + c2 )} (Vdata [n] - Ref) - | Vth |.

Here, " K " is a value determined by the structure and physical characteristics of the driving transistor Tdr as a proportional constant, and is a value obtained by dividing the mobility of the driving transistor Tdr and the channel width W of the driving transistor Tdr W / L " of the channel length L). In addition, when the transistors included in the organic light emitting diode display device are PMOS type transistors, the threshold voltage of the driving transistor has a negative value. On the other hand, the threshold voltage Vth of the driving transistor Tdr does not always have a constant value, but a deviation may occur depending on the operation state of the driving transistor Tdr.

In other words, according to Equation 1, the organic light emitting diode display according to the embodiments of the present invention is characterized in that the current Ioled flowing through the organic light emitting diode OLED during the light emission period t4 is equal to the threshold voltage (Vth), and can be determined only by the difference between the data voltage (Vdata) and the reference voltage (Ref). In addition, the organic light emitting diode display according to embodiments of the present invention is not affected by the high-potential power supply voltage due to the IR drop caused by the wiring resistance applied to the high-potential power supply voltage.

Therefore, the organic light emitting diode display according to embodiments of the present invention compensates for the deviation of the threshold voltage and the deviation of the high-potential power supply voltage due to the IR drop according to the operation state of the driving transistor, So that deterioration in image quality can be prevented.

Further, the organic light emitting diode display device according to the embodiments of the present invention can be adapted to a large area because the number of transistors and capacitors constituting the compensation circuit is small.

The current Ioled flowing through the organic light emitting diode OLED has been described above as being not affected by the threshold voltage Vth and the high potential supply voltage VDD of the driving transistor Tdr, Let's take a look at this.

FIGS. 6 and 7 are experimental data for explaining a threshold voltage deviation and a change in current according to a change in a high-potential power supply voltage of an organic light emitting diode display device according to embodiments of the present invention.

6, the high-level power supply voltage VDD is 12V, the high-level scan signal and the emission control signal are 12V, the low level scan signal and the emission control signal are -5V, the reference voltage Ref, Is experimental data based on the data voltage and the threshold voltage deviation of the driving transistor based on 8V.

6, the magnitude of the current Ioled flowing through the organic light emitting diode OLED varies according to the change of the data voltage Vdata, but it is within the range of -0.5V to 0.5V for the same data voltage Vdata Is not greatly changed according to the deviation (dVth) of the threshold voltage (Vth).

7, the high level scan signal and the emission control signal are 12V, the low level scan signal and the emission control signal are -5V, the reference voltage Ref is 8V, the data voltage is 0V, the c1 / c2 is experimental data according to the change of the high potential power supply voltage (VDD) with reference to 2.

As shown in FIG. 7, it can be seen that the magnitude of the current Ioled flowing through the organic light emitting diode (OLED) does not largely change with the change of the high-potential power supply voltage VDD between 11V and 13V.

It will be understood by those skilled in the art that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof.

It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. The scope of the present invention is defined by the appended claims rather than the detailed description and all changes or modifications derived from the meaning and scope of the claims and their equivalents are to be construed as being included within the scope of the present invention do.

T1, T2: first and second transistors C1, C2: first and second capacitors C1,
Tdr: driving transistor OLED: organic light emitting diode
VDD: High-potential power supply voltage VSS: Low-potential power supply voltage
Ref: Reference voltage

Claims (14)

A first transistor to which a data voltage or a reference voltage is applied to a source electrode and supplies the data voltage or the reference voltage to a first node according to a scan signal;
A driving transistor having a gate electrode connected to the first node, a source electrode connected to the second node, and a drain electrode connected to the fourth node;
A first capacitor coupled between the first node and the second node, the first capacitor storing a threshold voltage of the driving transistor;
A second transistor for supplying a high potential power supply voltage applied to a third node connected to the source electrode to the second node according to a light emission control signal; And
And an organic light emitting diode having an anode electrode connected to the fourth node and a high potential power supply voltage or a low potential power supply voltage applied to the cathode electrode.
The method according to claim 1,
The first transistor is turned on by the scan signal applied through the scan line,
And the second transistor is turned on by the emission control signal applied through the emission control line. The method according to claim 1,
And a second capacitor connected between the second node and the third node.
The method according to claim 1,
When the reference voltage is applied to the source electrode of the first transistor, the low potential power supply voltage is applied to the cathode electrode of the organic light emitting diode, and when the first and second transistors are turned on,
Wherein the reference voltage is supplied to the first node and the high potential power supply voltage is supplied to the second node.
The method according to claim 1,
The reference voltage is applied to the source electrode of the first transistor, the low potential power supply voltage is applied to the cathode electrode of the organic light emitting diode, the first transistor is turned on, and the second transistor is turned off,
Wherein the reference voltage is supplied to the first node, and the second node voltage is reduced to a voltage smaller than the high potential power supply voltage.
6. The method of claim 5,
Wherein the second node voltage is reduced to a sum of the reference voltage and an absolute value of a threshold voltage of the driving transistor.
The method according to claim 1,
The data voltage is applied to the source electrode of the first transistor, the high potential power supply voltage is applied to the cathode electrode of the organic light emitting diode, and when the first transistor is turned on and the second transistor is turned off,
Wherein the data voltage is supplied to the first node, and light emission of the organic light emitting diode is turned off.
The method according to claim 1,
The reference voltage is applied to the source electrode of the first transistor, the low potential power supply voltage is applied to the cathode electrode of the organic light emitting diode, the first transistor is turned off, and when the second transistor is turned on,
Wherein the organic light emitting diode emits light according to the data voltage and the reference voltage.
A method of driving an organic light emitting diode display device including first to second transistors, a driving transistor, first and second capacitors, and an organic light emitting diode,
A drain electrode of the first transistor, a gate electrode of the driving transistor, and one end of the first capacitor are connected through a first node, and a source electrode of the driving transistor, one end of the second capacitor, The source electrode of the second transistor and the other end of the second capacitor are connected through a third node, the drain electrode of the second transistor and the other end of the first capacitor are connected to each other, Electrode and an anode electrode of the organic light emitting diode are connected,
Initializing a voltage of the first node to the reference voltage while a reference voltage is applied to a source electrode of the first transistor while the first and second transistors are turned on;
Storing a threshold voltage of the driving transistor in the first capacitor while the first transistor is turned on and the second transistor is turned off;
Supplying a data voltage to the source electrode of the first transistor while the first transistor is turned on and the second transistor is turned off and supplying the data voltage to the first node; And
Wherein the organic light emitting diode emits light according to the data voltage and the reference voltage while the first transistor is turned off and the second transistor is turned on.
10. The method of claim 9,
And a high-potential power supply voltage is applied to the third node.
11. The method of claim 10,
Wherein the initializing comprises:
And initializing the second node voltage to the high potential power supply voltage.
11. The method of claim 10,
Wherein the step of storing the threshold voltage comprises:
Wherein the first transistor supplies the reference voltage to the first node and the second node voltage decreases to a voltage less than the high potential power supply voltage.
10. The method of claim 9,
Wherein the step of supplying the data voltage comprises:
And supplying a high potential power supply voltage to the cathode electrode of the organic light emitting diode.
10. The method of claim 9,
The first transistor is turned on by a scan signal applied through a scan line,
And the second transistor is turned on by a light emission control signal applied through a light emission control line.

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