KR20100054001A - Display device and driving method thereof - Google Patents

Abstract

PURPOSE: A display device and a driving method thereof are provided to secure the reliability of a pixel circuit by using a p-channel electric field effect transistor as a driving transistor. CONSTITUTION: A display device comprises an emitting device(LD). A first capacitor(Cst1) is connected between a first contact point and a second contact point. A driving transistor(Qd) comprises an input terminal, an output terminal, and a control terminal. The second capacitor(Cst2) is connected to the input terminal and the first contact point of the driving transistor. The first switching transistor(Qs1) is connected between a data voltage or a maintaining voltage and the first contact point. The second switching transistor(Qs2) is connected to the input terminal of the driving transistor and driving voltage. The third switching transistor(Qs3) is connected between the output terminal of the driving transistor and the second contact point.

Description

Display device and driving method thereof {DISPLAY DEVICE AND DRIVING METHOD THEREOF}

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

The pixel of the organic light emitting diode display includes an organic light emitting element, a thin film transistor (TFT), and a capacitor driving the organic light emitting element.

The thin film transistor is classified into a polysilicon thin film transistor and an amorphous silicon thin film transistor according to the type of the active layer.

Amorphous silicon can be deposited at a low temperature to form a thin film, and is mainly used in a semiconductor layer of a switching element of a display device mainly using glass having a low melting point as a substrate. However, the amorphous silicon thin film transistor has a difficulty in large area of the display device due to low electron mobility. In addition, as the amorphous silicon thin film transistor continuously applies a DC voltage to the control terminal, the threshold voltage may be changed and degraded. This is a major factor in shortening the lifespan of the organic light emitting display device.

Therefore, there is a demand for the application of polycrystalline silicon thin film transistors having high electron mobility, good high frequency operation characteristics, and low leakage current. However, the polycrystalline silicon thin film transistor is not easily manufactured so that the characteristics of the semiconductor included in the thin film transistor are uniform in the display device in the process of manufacturing the active layer from polycrystalline silicon. Therefore, deviations occur in the threshold voltage and the field effect mobility of the driving transistors, thereby reducing the screen uniformity.

The technical problem to be solved by the present invention is to compensate for the variation in the field effect mobility of the inter-pixel driving transistor as well as the non-uniformity of the threshold voltage of the inter-pixel driving transistor in the organic light emitting diode display and to secure the electrical reliability of the pixel circuit.

According to an exemplary embodiment, a display device includes a light emitting device, a driving transistor having a first capacitor connected between a first contact point and a second contact point, an input terminal, an output terminal, and a control terminal connected to the second contact point. A second capacitor connected to an input terminal of the driving transistor and the first contact point, a first switching transistor connected between the data voltage or sustain voltage and the first contact point, a driving voltage and an input terminal of the driving transistor; And a second switching transistor connected between the second switching transistor and a third switching transistor connected between the second contact point and the output terminal of the driving transistor.

The first to third switching transistors may be p-channel field effect transistors.

The first to third switching transistors may operate in response to different scan signals.

The display device may further include a fourth switching transistor connected between the output terminal of the driving transistor and the light emitting device.

The second switching transistor operates in response to a first scan signal, the first switching transistor operates in response to a second scan signal, and the third and fourth switching transistors operate in response to a third scan signal. Can be.

The first, second and fourth switching transistors may be p-channel field effect transistors, and the third switching transistor may be n-channel field effect transistors.

The display device may further include a fifth switching transistor connected between the first contact point and the sustain voltage.

The second switching transistor operates in response to a first scan signal, the first, third and fourth switching transistors operate in response to a second scan signal, and the fifth switching transistor responds to a third scan signal. Can be operated.

The first, third and fifth switching transistors may be n-channel field effect transistors, and the second and fourth switching transistors may be p-channel field effect transistors.

The display device may further include a fifth switching transistor connected between the second contact point and the reset voltage.

The second switching transistor operates in response to a first scan signal, the first and fourth switching transistors operate in response to a second scan signal, and the third and fifth switching transistors respond to a third scan signal. Can be operated.

The first switching transistor may be an n-channel field effect transistor, and the second to fifth switching transistors may be a p-channel field effect transistor.

The display device may further include a fifth switching transistor connected between the first contact point and the sustain voltage.

The second switching transistor operates in response to a first scan signal, the first, third and fourth switching transistors operate in response to a second scan signal, and the fifth switching transistor responds to a third scan signal. Can be operated.

The first and third switching transistors may be n-channel field effect transistors, and the second, fourth and fifth switching transistors may be p-channel field effect transistors.

The display device may further include a fifth switching transistor connected between the second contact point and the reset voltage.

The second switching transistor operates in response to a first scan signal, the first switching transistor operates in response to a second scan signal, the fifth switching transistor operates in response to a third scan signal, and The third and fourth switching transistors may operate in response to the fourth scan signal.

The first, second, fourth and fifth switching transistors may be p-channel field effect transistors, and the third switching transistor may be n-channel field effect transistors.

The second switching transistor operates in response to a first scan signal, the first and fourth switching transistors operate in response to a second scan signal, and the third switching transistor operates in response to a third scan signal. Can be.

The first switching transistor may be an n-channel field effect transistor, and the second to fourth switching transistors may be a p-channel field effect transistor.

The driving transistor may be a p-channel field effect transistor.

A driving method of a display device according to another exemplary embodiment of the present invention includes a light emitting device, a first capacitor connected between first and second contacts, an input terminal, an output terminal, and a control terminal connected to the second contact. A driving method of a display device including a driving transistor, and a second capacitor connected between an input terminal of the driving transistor and the first contact point, the driving method comprising: connecting a control terminal and an output terminal of the driving transistor, and driving voltage and the Connecting an input terminal of a driving transistor, connecting a data voltage to the first contact point, connecting a sustain voltage to the first contact point, and connecting the light emitting element to an output terminal of the driving transistor; Disconnecting an input terminal of the driving voltage from the input terminal of the driving transistor; Disconnecting the voltage and then connecting the driving voltage to the input terminal of the driving transistor.

In an operation of disconnecting an input terminal of the driving transistor from the driving voltage, the first contact may be connected to the sustain voltage.

When the control terminal and the output terminal of the driving transistor are connected, the control terminal and the output terminal of the driving transistor may be connected with a reset voltage.

The technical problem to be achieved by the present invention can compensate for the variation in the field effect mobility of the inter-pixel driving transistor as well as the non-uniformity of the threshold voltage of the inter-pixel driving transistor in the organic light emitting diode display. In addition, by using the p-channel field effect transistor as the driving transistor, the electrical reliability of the pixel circuit can be ensured.

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

First, an organic light emitting diode display according to an exemplary embodiment will be described with reference to FIGS. 1 and 2.

1 is a block diagram of an organic light emitting diode display according to an exemplary embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of one pixel in the organic light emitting diode display according to an exemplary embodiment of the present invention.

Referring to FIG. 1, an organic light emitting diode display according to an exemplary embodiment includes a display panel 300, a scan driver 400, a data driver 500, and a signal controller 600.

The display panel 300 includes a plurality of signal lines (not shown), a plurality of voltage lines (not shown), and a plurality of pixels PX connected to them and arranged in a substantially matrix form.

The signal line includes a plurality of scan signal lines (not shown) for transmitting a scan signal, and a plurality of data lines (not shown) for transferring a data signal. The scan signal lines extend approximately in the row direction and are substantially parallel to each other, and the data lines extend approximately in the column direction and are substantially parallel to each other.

The voltage line includes a driving voltage line (not shown) for transmitting a driving voltage and a sustain voltage line (not shown) for transmitting a sustain voltage.

As illustrated in FIG. 2, each pixel PX includes an organic light emitting element LD, a driving transistor Qd, a first capacitor Cst1, a second capacitor Cst2, first, second, third, and third pixels. And fourth and fifth switching transistors Qs1, Qs2, Qs3, Qs4, and Qs5.

The driving transistor Qd has an output terminal, an input terminal and a control terminal. The control terminal of the driving transistor Qd is connected to the first capacitor Cst1 at the contact point N2, the input terminal is connected to the driving voltage Vdd, and the output terminal is connected to the second and third switching transistor Qs2. , Qs3).

One end of the first capacitor Cst1 is connected to the driving transistor Qd at the contact point N2, and the other end thereof is the first switching transistor Qs1, the fifth switching transistor Qs5, and at the contact point N1. It is connected to the second capacitor Cst2.

One end of the second capacitor Cst2 is connected to the first capacitor Cst1, the first and fifth switching transistors Qs1 and Qs5 at the contact point N1, and the other end thereof is connected to the second switching transistor Qs2. It is.

The first switching transistor Qs1 operates in response to the second scan signal Vgbi and is connected between the contact point N1 and the input voltage Vd.

The second switching transistor Qs2 operates in response to the first scan signal Vgai and is connected between the driving voltage Vdd and the input terminal of the driving transistor Qd.

The third switching transistor Qs3 operates in response to the second scan signal Vgbi and is connected between the contact point N2 and the output terminal of the driving transistor Qd.

The fourth switching transistor Qs4 operates in response to the second scan signal Vgbi and is connected between the output terminal of the driving transistor Qd and the organic light emitting element LD.

The fifth switching transistor Qs5 operates in response to the third scan signal Vgbi and is connected between the contact point N1 and the sustain voltage Vsus.

The first, third and fifth switching transistors Qs1, Qs3 and Qs5 are n-channel field effect transistors, and the second and fourth switching transistors Qs2 and Qs4 and driving transistors Qd are p-channel field effect transistors. Transistor. Examples of field effect transistors include thin film transistors (TFTs), which may include polycrystalline silicon or amorphous silicon. Channel types of the switching transistors Qs1 to Q5 and the driving transistor Qd may be reversed, and in this case, the waveforms of the signals driving them may also be reversed.

The anode and the cathode of the organic light emitting element LD are connected to the output terminal of the fourth switching transistor Qs4 and the common voltage Vss, respectively. The organic light-emitting device (LD) is a fourth switch through the transistor (Qs4), and displays an image by emitting light with different intensity depending on the magnitude of the current (I _LD) for supplying a driving transistor (Qd), a current (I _LD) The magnitude of V depends on the magnitude of the voltage between the control terminal and the output terminal of the driving transistor Qd.

Referring back to FIG. 1, the scan driver 400 is connected to the scan signal line of the display panel 300 and applies a plurality of scan signals formed by a combination of a high voltage Von and a low voltage Voff to the scan signal line, respectively.

The high voltage Von may conduct the first, third, and fifth switching transistors Qs1, Qs3, and Qs5 or block the second, fourth, and fourth switching transistors Qs2 and Qs4. The low voltage Voff may block the first, third and fifth switching transistors Qs1, Qs3 and Qs5, or may conduct the second and fourth switching transistors Qs2 and Qs4. As the low voltage Voff, the sustain voltage Vsus blocks the first, third and fifth switching transistors Qs1, Qs3, and Qs5, or blocks the second and fourth switching transistors Qs2 and Qs4. It can be turned on. The sustain voltage Vsus is applied through the sustain voltage line, and the drive voltage Vdd may be applied through the drive voltage line.

The data driver 500 is connected to the data line of the display panel 300 and applies a data voltage Vdat representing the image signal to the data line.

The signal controller 600 controls operations of the scan driver 400, the data driver 500, and the like.

Each of the driving devices 400, 500, and 600 may be mounted directly on the display panel 300 in the form of at least one integrated circuit chip, or mounted on a flexible printed circuit film (not shown). The display panel 300 may be attached to the display panel 300 in the form of a tape carrier package or mounted on a separate printed circuit board (not shown). Alternatively, the driving devices 400, 500, and 600 may be integrated in the display panel 300 together with signal lines and transistors Qs 1-Qs 5 and Qd. In addition, the driving devices 400, 500, and 600 may be integrated into a single chip, in which case at least one of them or at least one circuit element constituting them may be outside the single chip.

Next, the display operation of the OLED display will be described in detail with reference to FIGS. 3 to 7 along with FIGS. 1 and 2.

3 is an example of a waveform diagram illustrating driving signals applied to a row of pixels in an organic light emitting diode display according to an exemplary embodiment of the present invention, and FIGS. 4 to 7 are one pixel in each section shown in FIG. 3. Is an equivalent circuit diagram of.

The signal controller 600 receives an input image signal Din and an input control signal ICON for controlling the display thereof from an external graphic controller (not shown). The input image signal Din contains luminance information of each pixel PX, and the luminance is a fixed number, for example, 1024 (= 2 ¹⁰ ), 256 (= 2 ⁸ ), or 64 (= 2 ⁶ ). It has two grays. Examples of the input control signal ICON include a vertical sync signal, a horizontal sync signal, a main clock signal, and a data enable signal.

The signal controller 600 properly processes the input image signal Din according to the operating conditions of the display panel 300 based on the input image signal Din and the input control signal ICON, and controls the scan control signal CONT1 and the data. To generate a signal CONT2 and the like. The signal controller 600 sends the scan control signal CONT1 to the scan driver 400, and the data control signal CONT2 and the output image signal Dout are sent to the data driver 500.

The scan control signal CONT1 may include a scanning start signal STV for instructing the scan start of the high voltage Von to the scan signal line and at least one clock signal for controlling the output period of the high voltage Von; An output enable signal (OE) or the like that limits the duration of the high voltage Von.

The data control signal CONT2 is a horizontal synchronization start signal indicating the start of transmission of the digital image signal Dout for one row of pixels PX, and a load signal and a data clock signal HCLK for applying an analog data voltage to the data line. And the like.

The scan driver 400 changes the scan signals Vgai, Vgbi, and Vgci applied to the scan signal line to high voltage Von or low voltage Voff according to the scan control signal CONT1 from the signal controller 600.

According to the data control signal CONT2 from the signal controller 600, the data driver 500 receives the digital output image signal Dout for the pixels PX in each row, and outputs the output image signal Dout. After converting to an analog data voltage Vdat, it is applied to a data line. As shown in FIG. 3, the data driver 500 outputs a data voltage Vdat for one pixel PX during one horizontal period 1H.

The following description focuses on a specific pixel row, for example, the i-th row.

Referring to FIG. 3, the scan driver 400 maintains the first scan signal Vgai at a low voltage Voff according to the scan control signal CONT1 from the signal controller 600, and the second scan signal Vgbi. Is changed from the low voltage Voff to the high voltage Von, and the third scan signal Vgci is maintained at the low voltage Voff.

Then, as shown in FIG. 4, the first and third switching transistors Qs1 and Qs3 are turned on, the second switching transistor Qs2 is kept in the turned on state, and the fourth switching transistor Qs4 is shut off. The fifth switching transistor Qs5 maintains a blocked state, which is referred to as a first period Ta1.

Then, the control terminal and the output terminal of the driving transistor Qd are connected, and the driving transistor Qd is diode connected. Then, the driving transistor Qd flows the output current I _LD which is controlled by the voltage difference Vgs between the control terminal and the input terminal of the driving transistor Qd, and the output current I _LD is the driving transistor Qd. The voltage Vgs between the control terminal and the input terminal of is flowed until it is equal to the threshold voltage Vth of the driving transistor Qd. Therefore, the voltage V _N2 of the contact point N2 converges to the following voltage value.

[Equation 1]

V _N2 = Vdd + Vth

Since the data voltage Vdat is applied to the contact point N1, the charging voltage Vcst1 charged in the first capacitor Cst1 is as follows.

&Quot; (2) "

Vcst1 = Vdd + Vth-Vdat

At this time, since the output terminal of the driving transistor Qd is not connected to the organic light emitting element LD, the organic light emitting element LD does not emit light.

Thereafter, the scan driver 400 maintains the first scan signal Vgai at the low voltage Voff and the second scan signal Vgbi at the high voltage Von according to the scan control signal CONT1 from the signal controller 600. ) Is changed to the low voltage Voff, and the third scan signal Vgci is changed from the low voltage Voff to the high voltage Von.

Then, as shown in FIG. 5, the first, fourth, and fifth switching transistors Qs1, Qs4, and Qs5 are turned on, the second switching transistor Qs2 remains in a turned on state, and the third switching transistor Qs3 is turned on. ) Is blocked, which is referred to as a second section Ta2.

In the second period Ta2, the contact N1 is connected to the sustain voltage Vsus, and the voltage V _N2 of the contact N2 changes as follows.

&Quot; (3) "

V _N2 = Vdd + Vth-Vdat + Vsus

In the second section Ta2, since the output terminal of the driving transistor Qd and the organic light emitting element LD are connected, the output current I _LD of the driving transistor Qd is supplied to the organic light emitting element LD, The light emitting device LD displays an image by emitting light at different intensities according to the magnitude of the output current I _LD . At this time, the output current I _LD of the driving transistor Qd is expressed as follows.

[Equation 4]

I _LD = 1/2 x μ x Ci x W / L x (Vgs-Vth) ²

= 1/2 x μ x Ci x W / L x (V _N2 -Vdd-Vth) ²

= 1/2 x μ x Ci x W / L x (Vdd + Vth-Vdat + Vsus-Vdd-Vth) ²

= 1/2 x μ x Ci x W / L x (Vdat-Vsus) ²

Where μ is the field effect mobility, Ci is the capacitance of the gate insulating layer, W is the channel width of the driving transistor Qd, and L is the channel length of the driving transistor Qd.

According to Equation 4, the output current I _LD in the light emission period T3 is determined only by the data voltage Vdat and the fixed sustain voltage Vsus. Therefore, the output current I _LD is not affected by the threshold voltage Vth of the driving transistor Qd.

Thereafter, the scan driver 400 changes the first scan signal Vgai from the low voltage Voff to the high voltage Von according to the scan control signal CONT1 from the signal controller 600, and then the second scan signal Vgbi. Is maintained at the low voltage Voff, and the third scan signal Vgci is changed from the high voltage Von to the low voltage Voff.

Then, as illustrated in FIG. 6, the first and third switching transistors Qs1 and Qs3 remain blocked, the second and fifth switching transistors Qs2 and Qs5 are blocked, and the fourth switching transistor Qs4. ) Is in a conductive state, and is referred to as a third section Ta3.

Since the connection between the input terminal of the driving transistor Qd and the driving voltage Vdd is disconnected in the third section Ta3, the voltage difference Vgs between the control terminal and the input terminal of the driving transistor Qd also decreases to some extent. Before the input terminal of the driving transistor Qd and the driving voltage Vdd are disconnected, the voltage difference Vgs between the control terminal and the input terminal of the driving transistor is represented by Equation 4 below, and the input terminal of the driving transistor Qd is: The voltage difference Vgs between the control terminal and the input terminal of the driving transistor after disconnection from the driving voltage Vdd is expressed by Equation 5 below.

[Equation 5]

V _N2 = Vsus-Vdat + Vtht

&Quot; (6) "

V _N2 = Vsus-Vdat + Vtht-ΔV

ΔV represents a decrease in the voltage difference Vgs between the control terminal and the input terminal of the driving transistor after the connection between the input terminal of the driving transistor Qd and the driving voltage Vdd is disconnected.

At this time, the output current I _LD of the driving transistor Qd is supplied to the organic light emitting element LD, and the organic light emitting element LD emits light of which the intensity varies depending on the size of the output current I _LD . Display. At this time, the output current I _LD of the driving transistor Qd is expressed as follows.

[Equation 7]

I _LD = 1/2 x μ x Ci x W / L x (Vgs-Vth) ²

= 1/2 x μ x Ci x W / L x (Vsus-Vdat + Vtht-ΔV-Vth) ²

= 1/2 x μ x Ci x W / L x (Vsus-Vdat-ΔV) ²

On the other hand, when the field effect mobility μ of the driving transistor Qd increases, a large amount of current also flows, so that the decrease ΔV of the voltage difference Vgs between the control terminal and the input terminal of the driving transistor Qd also increases. That is, since the field effect mobility μ of the driving transistor Qd and the decrease ΔV of the voltage difference Vgs between the control terminal and the input terminal of the driving transistor Qd are proportional to each other, the driving transistor is expressed by Equation 7 below. The output current I _LD of Qd is not affected by the field effect mobility μ.

Thereafter, the scan driver 400 converts the first scan signal Vgai from the high voltage Von to the low voltage Voff according to the scan control signal CONT1 from the signal controller 600, and the second and third scan signals. Maintain (Vgbi, Vgci) at low voltage (Voff).

Then, as shown in FIG. 7, the first, third and fifth switching transistors Qs1, Qs3 and Qs5 remain blocked, the second switching transistor Qs2 is turned on, and the fourth switching transistor Qs4. ) Is in a conductive state, and is referred to as a fourth section Ta4.

In the fourth section Ta4, the organic light emitting element LD emits light and displays an image according to the output current I _LD of the driving transistor Qd determined in the third section Ta3. At this time, the contact point N1 is connected to the driving voltage Vdd which is a constant constant voltage with the second capacitor Cst2 interposed therebetween. That is, since the second capacitor Cst2 is not electrically floating, the output current I _LD of the driving transistor Qd is kept constant at the value of Equation 7 in the fourth section Ta4. Can be.

The fourth section Ta4 lasts until the first section Ta1 of the pixel PX of the i-th row is started again in the next frame, and each section Ta1 described above with respect to the pixel PX of the next row is also started. Repeat the same operation in Ta4). In this manner, the control of the sections Ta1 to Ta4 is performed in order for all the scan signal lines in order to display the corresponding image on all the pixels PX.

As described above, according to the exemplary embodiment of the present invention, not only the threshold voltage Vth between the driving transistors Qd but also the field effect mobility μ may be varied, or only the threshold voltage Vth of each driving transistor Qd. In addition, even if the magnitude of the field effect mobility μ changes with time, the display device may display a uniform image.

An organic light emitting diode display according to another exemplary embodiment of the present invention will now be described in detail with reference to FIGS. 8 through 14.

8 is a circuit diagram of one pixel of an organic light emitting diode display according to another exemplary embodiment of the present invention, and FIG. 9 is a driving signal applied to one row of pixels in the organic light emitting diode display according to an exemplary embodiment of the present invention. 10 and 11 are equivalent circuit diagrams of one pixel according to a driving state of the OLED display of FIG. 8.

Referring to FIG. 8, each pixel PX of the organic light emitting diode display according to another exemplary embodiment of the present invention is the organic light emitting diode LD, the driving transistor Qd, and the first capacitor as in the organic light emitting diode display of FIG. 2. Cst1, a second capacitor Cst2, and first, second, third, fourth, and fifth switching transistors Qs1-Qs5.

However, in the organic light emitting diode display of FIG. 8, unlike the organic light emitting diode display of FIG. 2, the fifth switching transistor Qs5 is connected between the contact point N2 and the reset voltage Vreset. The reset voltage Vreset is a sufficiently low voltage and is smaller than the sum of the driving voltage Vdd and the threshold voltage Vth of the driving transistor Qd. In addition, the third switching transistor Qs3 operates in response to the fourth scan signal Vgdi different from the second scan signal Vgbi that controls the first and fourth switching transistors Qs1 and Qs4. The first switching transistor Qs1 is connected between the input voltage Vd and the contact point N1, and the input voltage Vd includes the sustain voltage Vsus and the data voltage Vdat.

Also, unlike the OLED display of FIG. 2, the third and fifth switching transistors Qs3 and Qs5 are p-channel field effect transistors.

The operation of the organic light emitting diode display of FIG. 8 will now be described in detail with focus on a specific pixel row, for example, the i-th row.

Referring to FIG. 9, the scan driver 400 maintains the first scan signal Vgai at a low voltage Voff according to the scan control signal CONT1 from the signal controller 600, and the second scan signal Vgbi. Is changed from the low voltage Voff to the high voltage Von, the third scan signal Vgci is changed from the high voltage Von to the low voltage Voff, and the fourth scan signal Vgdi is changed from the high voltage Von to the low voltage Voff. Change to

Then, as shown in FIG. 10, the first and third switching transistors Qs1 and Qs3 are turned on, the second switching transistor Qs2 is maintained in the connected state, and the fourth and fifth switching transistors Qs4 and Qs5 are maintained. ) Is blocked, which is referred to as a first section Tb1.

Then, the output terminal of the driving transistor Qd is connected to the contact point N2 connected to the control terminal, and a reset voltage Vreset voltage is applied to the contact point N2. Then, the output terminal and the control terminal of the driving transistor Qd are sufficiently low.

Thereafter, the scan driver 400 maintains the first scan signal Vgai at a low voltage Voff and the second scan signal Vgbi at a high voltage according to the scan control signal CONT1 from the signal controller 600. Von), the third scan signal Vgci is changed from the low voltage Voff to the high voltage Von, and the fourth scan signal Vgdi is kept at the low voltage Voff, which is referred to as a second period Tb2. do.

In the second period Tb2, as illustrated in FIG. 4, the driving transistor Qd is diode-connected, the driving transistor Qd flows the output current I _LD , and the output current I _LD is the driving transistor Qd. The voltage Vgs between the control terminal and the input terminal of is flowed until it is equal to the threshold voltage Vth of the driving transistor Qd. At this time, the voltage (V _N2 ) of the contact (N2) is the same as Equation 1 described above. Since the data voltage Vdat is applied to the contact point N1 in the second section Tb2, the charging voltage Vcst1 charged in the first capacitor Cst1 is represented by Equation 2 described above. At this time, the organic light emitting element LD does not emit light.

Thereafter, the scan driver 400 maintains the first scan signal Vgai at a low voltage Voff according to the scan control signal CONT1 from the signal controller 600, and maintains the second scan signal Vgbi at a high voltage ( Von), the third scan signal Vgci is maintained at the high voltage Von, and the fourth scan signal Vgdi is changed from the low voltage Voff to the high voltage Von.

Then, as shown in FIG. 11, the first switching transistor Qs1 is turned on, the second switching transistor Qs2 remains in the turned on state, the third switching transistor Qs3 is cut off, and the fourth and fifth The switching transistors Qs4 and Qs5 maintain a blocked state, which is referred to as a third period Tb3.

In the third period Tb3, since the input voltage Vd is the sustain voltage Vsus, the sustain voltage Vsus is applied to the contact point N1. Therefore, the voltage V _N2 of the contact N2 is equal to the above-described equation (3).

The output current I _LD of the driving transistor Qd in the third period Tb3 is expressed as shown in Equation 4 described above.

According to Equation 4, the output current I _LD is determined only by the data voltage Vdat and the fixed sustain voltage Vsus. Therefore, the output current I _LD is not affected by the threshold voltage Vth of the driving transistor Qd.

Thereafter, the scan driver 400 changes the first scan signal Vgai from the low voltage Voff to the high voltage Von according to the scan control signal CONT1 from the signal controller 600, and then the second scan signal Vgbi. Is changed from the high voltage Von to the low voltage Voff, the third scan signal Vgci is maintained at the high voltage Von, and the fourth scan signal Vgdi is kept at the high voltage Von.

Then, as shown in FIG. 6, the first and second switching transistors Qs1 and Qs2 are blocked, the third and fifth switching transistors Qs3 and Qs5 remain blocked, and the fourth switching transistor. Qs4 is turned on, and this is referred to as a fourth section Tb4.

Since the connection between the input terminal of the driving transistor Qd and the driving voltage Vdd is disconnected in the fourth section Tb4, the voltage difference Vgs between the control terminal and the input terminal of the driving transistor Qd is also reduced to some extent. After the connection between the input terminal of the driving transistor Qd and the driving voltage Vdd is disconnected, the voltage difference Vgs between the control terminal and the input terminal of the driving transistor is represented by Equation 6 described above.

At this time, the output current I _LD of the driving transistor Qd is supplied to the organic light emitting element LD, and the organic light emitting element LD emits light of which the intensity varies depending on the size of the output current I _LD . Display. At this time, the driving transistor Qd is the same as that of [Equation 7]. According to Equation 7, since the field effect mobility μ of the driving transistor Qd and the decrease ΔV of the voltage difference Vgs between the control terminal and the input terminal of the driving transistor Qd are proportional to each other, By 6, the output current I _LD of the driving transistor Qd is not affected by the field effect mobility μ.

Thereafter, the scan driver 400 changes the first scan signal Vgai from the high voltage Von to the low voltage Voff according to the scan control signal CONT1 from the signal controller 600, and then the second scan signal Vgbi. Is maintained at the low voltage Voff, and the third and fourth scan signals Vgci and Vgdi are held at the high voltage Von.

Then, as shown in FIG. 7, the first, third, and fifth switching transistors Qs1, Qs3, and Qs5 remain blocked, the second switching transistor Qs2 is turned on, and the fourth switching transistor. Qs4 remains in a conductive state, which is referred to as a fifth section Tb5.

In the fifth section Tb5, the organic light emitting element LD emits light and displays an image according to the output current I _LD of the driving transistor Qd determined in the third section Ta3.

As described above, the organic light emitting diode display of FIG. 8 has a threshold voltage of the driving transistor Qd by resetting the output terminal and the control terminal of the driving transistor Qd to the reset voltage Vreset in advance as compared to the organic light emitting diode display of FIG. 2. Shorten the compensation time of Vth) and allow accurate compensation.

Next, an organic light emitting diode display according to another exemplary embodiment of the present invention will be described in detail with reference to FIGS. 12 and 13.

12 is a circuit diagram of one pixel of an organic light emitting diode display according to another exemplary embodiment of the present invention, and FIG. 13 illustrates a driving signal applied to one row of pixels in an organic light emitting diode display according to another exemplary embodiment of the present invention. An example of a waveform diagram

Referring to FIG. 12, each pixel PX of the organic light emitting diode display according to another exemplary embodiment of the present invention may correspond to each pixel PX of the organic light emitting diode display according to another exemplary embodiment of the present invention. Like the device, the organic light emitting element LD, the driving transistor Qd, the first capacitor Cst1, the second capacitor Cst2, the first, second, third, fourth and fifth switching transistors Qs1-Qs5. ).

However, in the organic light emitting diode display of FIG. 12, unlike the organic light emitting diode display of FIG. 2, the fifth switching transistor Qs5 is a p-channel field effect transistor.

The organic light emitting diode display of FIG. 12 is driven according to the waveform of FIG. 13. Referring to the waveform of FIG. 13, the waveform of the third scan signal Vgci controlling the fifth switching transistor Qs5 is different from that of FIG. 3.

An organic light emitting diode display according to another exemplary embodiment will now be described in detail with reference to FIGS. 14 and 15.

FIG. 14 is a circuit diagram of one pixel of an organic light emitting diode display according to another exemplary embodiment. FIG. 15 illustrates a driving signal applied to one row of pixels in the organic light emitting diode display according to another exemplary embodiment. An example of a waveform diagram

Referring to FIG. 14, each pixel PX of the organic light emitting diode display according to another exemplary embodiment of the present invention may correspond to each pixel PX of the organic light emitting diode display according to another exemplary embodiment of the present invention. Like the device, the organic light emitting element LD, the driving transistor Qd, the first capacitor Cst1, the second capacitor Cst2, and the first, second, third and fourth switching transistors Qs1-Qs4 are included. do.

However, unlike the organic light emitting diode display of FIG. 2, the organic light emitting diode display of FIG. 14 does not include the fifth switching transistor Qs5, and the first switching transistor Qs1 is a p-channel field effect transistor.

The organic light emitting diode display of FIG. 14 is driven according to the waveform diagram of FIG. 15. Referring to FIG. 15, since the input voltage Vd includes the data voltage Vdat and the sustain voltage Vsus, the sustain voltage Vsus may be applied to the pixel even without the fifth switching transistor Qs5.

Now, an organic light emitting diode display according to another exemplary embodiment will be described in detail with reference to FIGS. 16 and 17.

16 is a circuit diagram of one pixel of an organic light emitting diode display according to another exemplary embodiment of the present invention, and FIG. 17 illustrates a driving signal applied to one row of pixels in the organic light emitting diode display according to another exemplary embodiment of the present invention. An example of a waveform diagram

Referring to FIG. 16, each pixel PX of the organic light emitting diode display according to another exemplary embodiment of the present invention may correspond to each pixel PX of the organic light emitting diode display according to another exemplary embodiment of the present invention. Like the device, the organic light emitting element LD, the driving transistor Qd, the first capacitor Cst1, the second capacitor Cst2, the first, second, third, fourth and fifth switching transistors Qs1-Qs5. ).

However, unlike the OLED display of FIG. 8, unlike the OLED display of FIG. 8, the first switching transistor Qs1 is a p-channel field effect transistor, and the third switching transistor Qs3 is an n-channel field effect transistor. .

The OLED display of FIG. 16 is driven according to the waveform diagram of FIG. 17.

An organic light emitting diode display according to another exemplary embodiment will now be described in detail with reference to FIGS. 18 and 19.

FIG. 18 is a circuit diagram of one pixel of an organic light emitting diode display according to another exemplary embodiment. FIG. 19 illustrates a driving signal applied to one row of pixels in the organic light emitting diode display according to another exemplary embodiment. An example of a waveform diagram

Referring to FIG. 18, each pixel PX of the organic light emitting diode display according to another exemplary embodiment of the present invention is the organic light emitting diode LD, the driving transistor Qd, and the first capacitor as in the organic light emitting diode display of FIG. 14. Cst1, a second capacitor Cst2, and first, second, third, and fourth switching transistors Qs1-Qs4.

However, unlike the organic light emitting diode display of FIG. 14, the first switching transistor Qs1 is an n-channel field effect transistor, and the third switching transistor Qs3 is a p-channel field effect transistor.

The OLED display of FIG. 18 is driven according to the waveform diagram of FIG. 19.

Now, an organic light emitting diode display according to another exemplary embodiment will be described in detail with reference to FIGS. 20 and 21.

20 is a circuit diagram of one pixel of an organic light emitting diode display according to another exemplary embodiment of the present invention, and FIG. 21 illustrates a driving signal applied to one row of pixels in an organic light emitting diode display according to another exemplary embodiment of the present invention. It is an example of the waveform diagram shown

Referring to FIG. 20, each pixel PX of the organic light emitting diode display according to another exemplary embodiment of the present invention is the organic light emitting diode LD, the driving transistor Qd, and the first capacitor as in the organic light emitting diode display of FIG. 14. Cst1, a second capacitor Cst2, and first, second, and third switching transistors Qs1-Qs3.

However, unlike the organic light emitting diode display of FIG. 14, the organic light emitting diode display of FIG. 20 does not include the fourth switching transistor Qs4, and the third switching transistor Qs3 is a p-channel field effect transistor.

The OLED display of FIG. 20 is driven according to the waveform diagram of FIG. 21.

The OLED display of FIG. 20 has a pixel structure in which the number of switching transistors is minimized.

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

1 is a block diagram of an organic light emitting diode display according to an exemplary embodiment of the present invention.

2 is an equivalent circuit diagram of one pixel in an organic light emitting diode display according to an exemplary embodiment of the present invention.

3 is an example of a waveform diagram illustrating driving signals applied to one row of pixels in an organic light emitting diode display according to an exemplary embodiment.

4 to 7 are equivalent circuit diagrams of one pixel in each section shown in FIG. 3.

8 is a circuit diagram of one pixel of an organic light emitting diode display according to another exemplary embodiment of the present invention.

9 is an example of a waveform diagram illustrating a driving signal applied to one row of pixels in an organic light emitting diode display according to an exemplary embodiment of the present invention.

10 and 11 are equivalent circuit diagrams of pixels according to driving states of the organic light emitting diode display illustrated in FIG. 8.

12 is a circuit diagram of one pixel of an organic light emitting diode display according to another exemplary embodiment of the present invention.

FIG. 13 is an example of a waveform diagram illustrating driving signals applied to one row of pixels in an organic light emitting diode display according to an exemplary embodiment.

14 is a circuit diagram of one pixel of an organic light emitting diode display according to another exemplary embodiment of the present invention.

FIG. 15 is an example of a waveform diagram illustrating driving signals applied to one row of pixels in the OLED display of FIG. 14.

16 is a circuit diagram of one pixel of an organic light emitting diode display according to another exemplary embodiment of the present invention.

FIG. 17 is an example of waveform diagram illustrating driving signals applied to one row of pixels in the OLED display of FIG. 16.

18 is a circuit diagram of one pixel of an organic light emitting diode display according to another exemplary embodiment of the present invention.

FIG. 19 is an example of a waveform diagram illustrating driving signals applied to one row of pixels in the organic light emitting diode display of FIG. 18.

20 is a circuit diagram of one pixel of an organic light emitting diode display according to another exemplary embodiment of the present invention.

FIG. 21 is an example of waveform diagram illustrating a driving signal applied to one row of pixels in the OLED display of FIG. 20.

<Description of the symbols for the main parts of the drawings>

300: display panel 400: scan driver

500: data driver

600: signal control unit CONT1: scanning control signal

CONT2: data control signal Cst1, Cst2: capacitor

Din: input video signal Dout: output video signal

ICON: input control signal I _LD : output current of drive transistor

LD: organic light emitting element N1, N2: contact

OE: output limit signal PX: pixel

Qd: driving transistor Qs1 to Qs5: switching transistor

Vdat: Data Voltage Vdd: Driving Voltage

Vsus: holding voltage Vss: common voltage

Claims (24)

Light emitting element, A first capacitor connected between the first contact and the second contact, A driving transistor having an input terminal, an output terminal, and a control terminal connected to the second contact point, A second capacitor connected to the input terminal of the driving transistor and the first contact point; A first switching transistor connected between a data voltage or a sustain voltage and the first contact point; A second switching transistor connected to a driving voltage and an input terminal of the driving transistor, and A third switching transistor connected between the second contact point and an output terminal of the driving transistor Display device comprising a. In claim 1, And the first to third switching transistors are p-channel field effect transistors. In claim 2, The first to third switching transistors operate in response to different scan signals. In claim 1, And a fourth switching transistor connected between the output terminal of the driving transistor and the light emitting element. In claim 4, The second switching transistor operates in response to a first scan signal, the first switching transistor operates in response to a second scan signal, and the third and fourth switching transistors operate in response to a third scan signal. Display device. In claim 5, And the first, second and fourth switching transistors are p-channel field effect transistors, and the third switching transistors are n-channel field effect transistors. In claim 4, And a fifth switching transistor connected between the first contact point and the sustain voltage. In claim 7, The second switching transistor operates in response to a first scan signal, the first, third and fourth switching transistors operate in response to a second scan signal, and the fifth switching transistor responds to a third scan signal. Display device that operates by. In claim 8, And the first, third and fifth switching transistors are n-channel field effect transistors, and the second and fourth switching transistors are p-channel field effect transistors. In claim 4, And a fifth switching transistor connected between the second contact point and a reset voltage. In claim 10, The second switching transistor operates in response to a first scan signal, the first and fourth switching transistors operate in response to a second scan signal, and the third and fifth switching transistors respond to a third scan signal. Display device that operates by. In claim 11, The first switching transistor is an n-channel field effect transistor, and the second to fifth switching transistors are p-channel field effect transistors. In claim 4, And a fifth switching transistor connected between the first contact point and the sustain voltage. The method of claim 13, The second switching transistor operates in response to a first scan signal, the first, third and fourth switching transistors operate in response to a second scan signal, and the fifth switching transistor responds to a third scan signal. Display device that operates by. The method of claim 14, And the first and third switching transistors are n-channel field effect transistors, and the second, fourth and fifth switching transistors are p-channel field effect transistors. In claim 4, And a fifth switching transistor connected between the second contact point and a reset voltage. The method of claim 16, The second switching transistor operates in response to a first scan signal, the first switching transistor operates in response to a second scan signal, the fifth switching transistor operates in response to a third scan signal, and And the third and fourth switching transistors operate in response to the fourth scan signal. The method of claim 17, And the first, second, fourth and fifth switching transistors are p-channel field effect transistors, and the third switching transistors are n-channel field effect transistors. In claim 4, The second switching transistor operates in response to a first scan signal, the first and fourth switching transistors operate in response to a second scan signal, and the third switching transistor operates in response to a third scan signal. Display device. The method of claim 19, The first switching transistor is an n-channel field effect transistor, and the second to fourth switching transistors are p-channel field effect transistors. In claim 1, And the driving transistor is a p-channel field effect transistor. A driving transistor having a light emitting element, a first capacitor connected between the first and second contacts, an input terminal, an output terminal, and a control terminal connected to the second contact point, and an input terminal and the first terminal of the driving transistor; A driving method of a display device including a second capacitor connected between a contact point, Connecting a control terminal and an output terminal of the driving transistor, connecting a driving voltage and an input terminal of the driving transistor, and connecting a data voltage to the first contact point; Connecting a sustain voltage to the first contact and connecting the light emitting device to an output terminal of the driving transistor; Disconnecting an input terminal of the driving transistor from the driving voltage; Disconnecting an input terminal of the driving transistor from the driving voltage and then connecting the input terminal of the driving transistor to the driving voltage again; Method of driving a display device comprising a. The method of claim 22, And disconnecting the driving voltage from the input terminal of the driving transistor and connecting the first contact to the sustain voltage. The method of claim 23, And connecting a control terminal and an output terminal of the driving transistor with a reset voltage when connecting the control terminal and the output terminal of the driving transistor.

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