KR100658271B1 - Pixel and organic light emitting display using the same - Google Patents

Abstract

A pixel and an organic light emitting display using the same are provided to improve aperture ratio, to improve driving speed, and to minimize power consumption by not forming a capacitor in each pixel. A pixel of an organic light emitting display for driving one frame by dividing the frame into plural frames includes an OLED(Organic Light Emitting Diode); a first transistor(M1) connected to a data line(Dm) and a scan line(Sn) and turned on when a scan signal is supplied to the scan line, to transmit a data signal supplied to the data line to a first node(N1); an inverter unit(44) connected between the first node and the OLED to control the emission state of the OLED correspondingly to the data signal; and a second transistor(M2) connected between the first node and a reset line(Rn) and turned on when a reset signal is supplied to the reset line, to change the OLED into a non-emission state.

Description

Pixel and Organic Light Emitting Display Using the same

1 is a circuit diagram illustrating a pixel of a conventional organic light emitting display device.

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

3 illustrates a frame of an organic light emitting diode display according to an exemplary embodiment of the present invention.

4 is a waveform diagram illustrating a driving waveform supplied during a sub frame period included in one frame.

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

FIG. 6 is a diagram illustrating an example of the inverter illustrated in FIG. 5.

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

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

2,42,46 pixel circuit 4,40 pixel

10: scan driver 20: data driver

30: pixel portion 50: timing controller

44,48: inverter section

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pixel and an organic light emitting display using the same, and more particularly, to a pixel capable of high-speed driving and improving an aperture ratio and an organic light emitting display using the same.

Recently, various flat panel displays have been developed to reduce weight and volume, which are disadvantages of cathode ray tubes. The flat panel display includes a liquid crystal display, a field emission display, a plasma display panel, and an organic light emitting display.

Among flat panel displays, an organic light emitting display displays an image using organic light emitting diodes (OLEDs) that generate light by recombination of electrons and holes. Such an organic light emitting diode display has advantages in that it has a fast response speed and is driven with low power consumption.

1 is a circuit diagram illustrating a pixel of a conventional organic light emitting display device.

Referring to FIG. 1, a pixel 4 of a conventional organic light emitting display device is connected to an organic light emitting diode OLED, a data line Dm, and a scan line Sn to control the organic light emitting diode OLED. The circuit 2 is provided.

The anode electrode of the organic light emitting diode OLED is connected to the pixel circuit 2, and the cathode electrode is connected to the second power source ELVSS. Such an organic light emitting diode (OLED) generates light having a predetermined brightness in response to a current supplied from the pixel circuit 2.

The pixel circuit 2 controls the amount of current supplied to the organic light emitting diode OLED corresponding to the data signal supplied to the data line Dm when the scan signal is supplied to the scan line Sn. To this end, the pixel circuit 2 includes a second transistor M2 connected between the first power supply ELVDD and the organic light emitting diode OLED, the second transistor M2, the data line Dm, and the scan line Sn. And a storage capacitor C connected between the gate electrode and the first electrode of the second transistor M2.

The gate electrode of the first transistor M1 is connected to the scan line Sn, and the first electrode is connected to the data line Dm. The second electrode of the first transistor M1 is connected to one terminal of the storage capacitor C. Here, the first electrode is set to any one of a source electrode and a drain electrode, and the second electrode is set to an electrode different from the first electrode. For example, when the first electrode is set as the source electrode, the second electrode is set as the drain electrode. The first transistor M1 connected to the scan line Sn and the data line Dm is turned on when a scan signal is supplied from the scan line Sn to receive a data signal supplied from the data line Dm. Supply to (C). In this case, the storage capacitor C charges a voltage corresponding to the data signal.

The gate electrode of the second transistor M2 is connected to one terminal of the storage capacitor C, and the first electrode is connected to the other terminal of the storage capacitor C and the first power supply ELVDD. The second electrode of the second transistor M2 is connected to the anode electrode of the organic light emitting diode OLED. The second transistor M2 controls the amount of current flowing from the first power source ELVDD to the organic light emitting diode OLED in response to the voltage value stored in the storage capacitor C. In this case, the organic light emitting diode OLED generates light corresponding to the amount of current supplied from the second transistor M2.

However, since the pixels of the conventional organic light emitting display display the gray scale using the voltage stored in the storage capacitor C, it is difficult to accurately express the desired gray scale. (Analog driving) In fact, the storage capacitor C Since a plurality of gray scales must be expressed by using a constant voltage which can be stored in the R, it is difficult to accurately represent the brightness difference between adjacent gray scales.

In addition, each of the pixels of the organic light emitting diode display includes a storage capacitor C to store a predetermined voltage. Here, the storage capacitor C is formed in a wide area in order to store a predetermined voltage in each pixel 4, thereby causing a problem that the aperture ratio is lowered. In addition, when the storage capacitor C is used in each of the pixels, a predetermined time is consumed for the charge / discharge operation of the storage capacitor C, thereby causing a problem in that the driving speed is lowered. In addition, when the storage capacitor (C) is used in each of the pixels, high power consumption is consumed by the charge / discharge of the storage capacitor (C).

Accordingly, an object of the present invention is to provide a pixel and an organic light emitting display using the same to enable high-speed driving and to improve an aperture ratio.

In order to achieve the above object, the first side of the present invention is a first node connected to the organic light emitting diode, the data line and the scan line and turned on when the scan signal is supplied to the scan line and supplied to the data line. A first transistor for transmitting to the first transistor, an inverter unit connected between the first node and the organic light emitting diode and controlling whether the organic light emitting diode emits light in response to the data signal, and between the first node and the reset line. And a second transistor for turning on when the reset signal is supplied to the reset line and for switching the organic light emitting diode to a non-light emitting state.

Preferably, the inverter unit inverts the signal of the first node to supply to the organic light emitting diode and a first inverter for inverting the output signal of the first inverter to supply to the input terminal of the first inverter Two inverters are provided. The second transistor is turned on when the reset signal is supplied to supply a voltage corresponding to a logic value of "1" to the first node. The second inverter includes at least one transistor, and a channel width of the first transistor is set to be wider than a channel width of a transistor constituting the second inverter.

The second aspect of the present invention sequentially supplies the scanning signal during the syringe period included in each of the plurality of subframes included in one frame, and sequentially supplies the reset signal to the reset lines during the reset period included in each of the subframes. A scan drive unit for performing; A data driver for supplying a data signal to data lines during the syringe; Provided is an organic light emitting display device including pixels that receive the data signal during the syringe period and emit or do not emit light for a predetermined time and are switched to the non-emission state during the reset period.

Preferably, a predetermined gray level is expressed during the one frame period by using the sum of the times at which the pixels emit light during the sub frame period. The scan signal supplied to the i (i is a natural number) scan line is supplied after the reset signal is supplied to the i-th reset line.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 2 to 7 which can be easily implemented by those skilled in the art.

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

Referring to FIG. 2, an organic light emitting diode display according to an exemplary embodiment of the present invention includes a plurality of pixels 40 connected to scan lines S1 to Sn, reset lines R1 to Rn, and data lines D1 to Dm. ), A scan driver 10 for driving the scan lines S1 to Sn and reset lines R1 to Rn, and a data driver for driving the data lines D1 to Dm. 20 and a timing controller 50 for controlling the scan driver 10 and the data driver 20.

The timing controller 50 generates a data drive control signal DCS and a scan drive control signal SCS in response to the synchronization signals supplied from the outside. The data drive control signal DCS generated by the timing controller 50 is supplied to the data driver 20, and the scan drive control signal SCS is supplied to the scan driver 10. The timing controller 50 supplies the data Data supplied from the outside to the data driver 20.

The data driver 20 supplies a data signal to the data lines D1 to Dm for each of a plurality of sub frame periods included in one frame. Here, the data signal is divided into a first data signal that can emit light of the pixel 40 and a second data signal that does not emit light of the pixel 40. That is, the data driver 20 supplies the first data signal or the second data signal to the data lines D1 to Dm for controlling whether the pixel 40 emits light in each sub frame period.

The scan driver 10 sequentially supplies a scan signal to the scan lines S1 to Sn in each sub frame period. When the scan signals are sequentially supplied to the scan lines S1 to Sn, the pixels 40 are sequentially selected for each line, and the selected pixels 40 are the first data signal or the second supplied from the data lines D1 to Dm. The data signal is supplied. The scan driver 10 sequentially supplies reset signals to the reset lines R1 to Rn after the pixels 40 emit light for a predetermined time in each subframe. The pixels 40 supplied with the reset signal are switched to the non-emission state regardless of the previous state.

The pixel unit 30 receives the first power source ELVDD and the second power source ELVSS from the outside and supplies the same to the pixels 40. Each of the pixels 40 supplied with the first power source ELVDD and the second power source ELVSS receives a data signal (a first data signal or a second data signal) when a scan signal is supplied, and the supplied data signal. Corresponding to the light emission or non-light emission during each sub frame period. When the reset signal is supplied, the pixels 40 are converted to the non-light emitting state by using the voltage of the first power source ELVDD (or the second power source ELVSS).

3 is a view schematically showing one frame of the present invention. 4 is a waveform diagram showing a driving waveform supplied during a sub frame period.

3 and 4, one frame 1F of the present invention is driven by being divided into a plurality of subframes SF1 to SF8. (Digital driving) Here, each subframe SF1 to SF8 is a scan signal. The driving period is divided into a light emitting period in which the pixels 40 supplied with the first data signal are emitted and a reset period in which the pixels 40 are switched to a non-light emitting state.

The scan signal is sequentially supplied to the scan lines S1 to Sn during the interval between the syringes. The first data signal or the second data signal is supplied to the data lines D1 to Dm. That is, during the syringe period, the pixels 40 are supplied with the first data signal or the second data signal.

During the light emitting period, each of the pixels 40 emits light or not emits light while maintaining the first data signal or the second data signal supplied during the syringe period. That is, the pixels 40 supplied with the first data signal during the syringe period are set to the light emitting state during the corresponding sub frame period, and the pixels 40 supplied with the second data signal are in the non-emitting state during the corresponding sub frame period. Is set to.

Here, the light emission periods are set differently in each of the subframes SF1 to SF8. For example, when the image is to be displayed with 256 gray levels, eight subfields SF1 to SF8 are divided into one frame as shown in FIG. 3. In each of the eight subfields SF1 to SF8, the emission period is increased at a rate of 2 ⁿ (n = 0,1,2,3,4,5,6,7). That is, in the present invention, an image having a predetermined gray level is displayed by controlling whether light is emitted from the pixels 40 in each subframe. On the other hand, one frame shown in Figure 3 is an example for expressing the present invention is not limited thereto. For example, one frame may be divided into ten or more subframes, and the light emission period of each subframe may be variously set by a designer.

The reset signal is sequentially supplied to the reset lines R1 to Rn during the reset period. In practice, the reset signal is supplied to the pixels 40 after the pixels 40 emit light for a predetermined time in each subframe. For example, the reset signal supplied to the i-th reset line Ri may be supplied immediately before the scan signal is supplied to the i-th scan line Si. When the reset signals are sequentially supplied to the reset lines R1 to Rn during the reset period, the pixels 40 are sequentially switched to the non-light emitting state.

5 is a diagram illustrating a pixel according to a first embodiment of the present invention.

Referring to FIG. 5, the pixel according to the first exemplary embodiment of the present invention is connected to the organic light emitting diode OLED, the data line Dm, the reset line Rn, and the scan line Sn, and the organic light emitting diode OLED. And a pixel circuit 42 for controlling.

The anode electrode of the organic light emitting diode OLED is connected to the pixel circuit 42, and the cathode electrode is connected to the second power source ELVSS. The organic light emitting diode OLED is controlled to emit light in response to the data signal supplied to the pixel circuit 42.

The pixel circuit 42 controls whether the organic light emitting diode OLED emits light in response to the data signal supplied to the data line Dm when the scan signal is supplied to the scan line Sn. When the reset signal is supplied to the reset line Rn, the pixel circuit 42 receives the first power source ELVDD to switch the organic light emitting diode OLED to the non-light emitting state.

To this end, the pixel circuit 42 includes a first transistor M1 connected to the data line Dm, the scan line Sn, and the first node N1, the first power source ELVDD, the reset line Rn, and the like. A second transistor M2 connected to the first node N1 and an inverter unit 44 connected between the first node N1 and the organic light emitting diode OLED are provided.

The gate electrode of the first transistor M1 is connected to the scan line Sn, and the first electrode is connected to the data line Dm. The second electrode of the first transistor M1 is connected to the first node N1. When the scan signal is supplied to the scan line Sn, the first transistor M1 is turned on to supply the data signal supplied from the data line Dm to the first node N1.

The inverter unit 44 controls whether the organic light emitting diode OLED emits light while maintaining the data signal supplied to the first node N1 for a sub frame period. To this end, the inverter unit 44 inverts the data signal supplied to the first node N1 and supplies the first inverter IN1 and the output voltage of the first inverter IN1 to supply the organic light emitting diode OLED. The second inverter (IN2) for feeding back to the input terminal. Here, the first inverter IN1 and the second inverter IN2 may be implemented in various forms. For example, each of the first inverter IN1 and the second inverter IN2 may be implemented with two transistors as shown in FIG. 6.

Meanwhile, when the second inverter IN2 is implemented with two transistors, each channel width is smaller than the channel width of the first transistor M1. As such, when the channel width of the first transistor M1 is formed to be wider than that of the transistor of the second inverter IN2, the voltage value of the first node N1 may be easily changed in response to the data signal.

The gate electrode of the second transistor M2 is connected to the reset line Rn, and the first electrode is connected to the first power source ELVDD. The second electrode of the second transistor M2 is connected to the first node N1. The second transistor M2 is turned on when the reset signal is supplied to the reset line Rn to supply the voltage of the first power source ELVDD to the first node N1.

Referring to the operation of the pixel 40 in detail, first, the scan signal is supplied to the scan line Sn to turn on the first transistor M1. When the first transistor M1 is turned on, the first data signal (logic of "0") or the second data signal (logic of "1") supplied to the data line Dm is transferred to the first node N1. Supplied.

At this time, the inverter unit 44 controls whether the organic light emitting diode OLED emits light while maintaining the first data signal or the second data signal supplied to the first node N1 for the corresponding sub frame period. For example, if the first data signal is supplied to the first node N1, the first inverter IN1 inverts the first data signal and supplies a logic voltage of “1” to the anode electrode of the organic light emitting diode OLED. do. Then, the organic light emitting diode OLED emits light during the corresponding sub frame period. If the second data signal is supplied to the first node N1, the first inverter IN2 inverts the second data signal and supplies a logic voltage of “0” to the anode electrode of the organic light emitting diode OLED. Then, the organic light emitting diode OLED is not emitted during the corresponding sub frame period. Meanwhile, the second inverter IN2 feeds back the output (ie, the logic voltage) of the first inverter IN1 to the input of the first inverter IN1 so that the logic voltage corresponding to the data signal is maintained for the sub frame period. .

Thereafter, the reset signal is supplied to the reset line Rn to turn on the second transistor M2. When the second transistor M2 is turned on, the first power source ELVDD: a logic voltage of "1" is supplied to the first node N1. When the voltage of the first power supply ELVDD is supplied to the first node N1, the first inverter IN1 inverts the voltage of the first power supply ELVDD (a logic voltage of “0”) to form the organic light emitting diode OLED. ), And the organic light emitting diode (OLED) is switched to the non-light emitting state. Here, when each of the pixels 40 is switched to the non-emission state when the reset signal is supplied, the pixels 40 may be stably driven. In addition, gray levels may be implemented in various ways by controlling the timing of supply of the reset signal.

As described above, in the present invention, a gray level is expressed by dividing one frame into a plurality of subframes and controlling whether pixels 40 emit light during the subframe period. When the gray level is expressed using whether the pixels 40 emit light, the desired gray level may be accurately represented. In the present invention, the capacitors are not included in the pixels 40. As such, when no capacitor is included in each of the pixels 40, the aperture ratio of the pixels 40 may be improved. In fact, even if the inverters IN1 and IN2 included in the inverter unit 44 are implemented with four transistors as shown in FIG. 6, the mounting area is set narrower than that of the capacitors.

In addition, since the capacitor is not used in the present invention, additional time is not consumed for charging / discharging, and thus high-speed driving is possible. In the present invention, since a capacitor is not used, power consumption can be minimized.

7 is a diagram illustrating a pixel according to a second exemplary embodiment of the present invention.

Referring to FIG. 7, the pixel according to the second exemplary embodiment of the present invention is connected to the organic light emitting diode OLED, the data line Dm, the reset line Rn, and the scan line Sn, and the organic light emitting diode OLED. And a pixel circuit 46 for controlling.

The anode electrode of the organic light emitting diode OLED is connected to the pixel circuit 46, and the cathode electrode is connected to the second power source ELVSS. The organic light emitting diode OLED is controlled to emit light in response to the data signal supplied to the pixel circuit 46.

The pixel circuit 46 controls whether the organic light emitting diode OLED emits light in response to the data signal supplied to the data line Dm when the scan signal is supplied to the scan line Sn. When the reset signal is supplied to the reset line Rn, the pixel circuit 46 receives the second power source ELVSS to switch the organic light emitting diode OLED to the non-light emitting state.

To this end, the pixel circuit 46 includes a first transistor M1 connected to the data line Dm, the scan line Sn, and the first node N1, the second power source ELVSS, the reset line Rn, and the like. A second transistor M2 connected to the first node N1 and an inverter unit 48 connected between the first node N1 and the organic light emitting diode OLED are provided.

The gate electrode of the first transistor M1 is connected to the scan line Sn, and the first electrode is connected to the data line Dm. The second electrode of the first transistor M1 is connected to the first node N1. When the scan signal is supplied to the scan line Sn, the first transistor M1 is turned on to supply the data signal supplied from the data line Dm to the first node N1.

The inverter unit 48 controls whether the organic light emitting diode OLED emits light while maintaining the data signal supplied to the first node N1 for a sub frame period. To this end, the inverter unit 48 may include a first inverter IN1 and a second inverter IN2 and a second inverter IN2 connected in series between the first node N1 and the organic light emitting diode OLED. And a third transistor M3 connected between the output terminal and the input terminal of the first inverter IN1.

The first inverter IN1 and the second inverter IN2 are connected in series between the first node N1 and the organic light emitting diode OLED so as to correspond to a data signal applied to the first node N1. Controls whether or not OLED is emitted. The third transistor M3 is turned off when the scan signal is supplied to the scan line Sn, and is turned on for another period so that the output voltage of the second inverter IN2 is input to the input terminal of the first inverter IN1. To supply.

The gate electrode of the second transistor M2 is connected to the reset line Rn, and the first electrode is connected to the second power source ELVSS. The second electrode of the second transistor M2 is connected to the first node N1. The second transistor M2 is turned on when the reset signal is supplied to the reset line Rn to supply the voltage of the second power source ELVSS to the first node N1.

Referring to the operation of the pixel 40 in detail, first, the scan signal is supplied to the scan line Sn to turn on the first transistor M1. When the first transistor M1 is turned on, the first data signal (logic of “1”) or the second data signal (logic of “0”) is supplied to the first node N1.

At this time, the inverter unit 48 controls the emission of the organic light emitting diode OLED while maintaining the first data signal or the second data signal supplied to the first node N1 for the corresponding sub frame period. For example, when the first data signal is supplied to the first node N1, the first inverter IN1 and the second inverter IN2 invert the first data signal twice to convert the logic voltage of “1” to the organic light emitting diode. It is supplied to the anode electrode of (OLED). Then, the organic light emitting diode OLED emits light during the corresponding sub frame period. If the second data signal is supplied to the first node N1, the first inverter IN1 and the second inverter IN2 invert the second data signal twice so as to convert the logic voltage of “0” into the organic light emitting diode OLED. It is supplied to the anode electrode of). Then, the organic light emitting diode OLED is not emitted during the corresponding sub frame period. Meanwhile, the third transistor M3 feeds back the output of the second inverter IN2 to the input of the first inverter IN1 so that the logic voltage corresponding to the data signal is maintained for the sub frame period.

Thereafter, the reset signal is supplied to the reset line Rn to turn on the second transistor M2. When the second transistor M2 is turned on, the second power supply ELVSS: a logic voltage of "0" is supplied to the first node N1. When the voltage of the second power supply ELVSS is supplied to the first node N1, the first inverter IN1 and the second inverter IN2 invert the voltage of the second power supply ELVSS twice (a logic voltage of “0”). The organic light emitting diode OLED is supplied to the organic light emitting diode OLED, and the organic light emitting diode OLED is converted into a non-light emitting state. Here, when each of the pixels 40 is switched to the non-emission state when the reset signal is supplied, the pixels 40 may be stably driven. In addition, gray levels may be implemented in various ways by controlling the timing of supply of the reset signal.

The above detailed description and drawings are merely exemplary of the present invention, but are used only for the purpose of illustrating the present invention and are not intended to limit the scope of the present invention as defined in the meaning or claims. Accordingly, those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical protection scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

As described above, according to the pixel and the organic light emitting display using the same according to the embodiment of the present invention, since the capacitor is not formed in each pixel, the aperture ratio can be improved. In addition, since a capacitor is not formed in each of the pixels, the driving speed can be improved and power consumption can be minimized. In the present invention, the gray scale expression power can be improved because the gray scale is expressed using the light emission time.

Claims (10)

In a pixel of an organic light emitting display device that drives one frame by dividing the frame into a plurality of frames, Organic light emitting diodes, A first transistor connected to the data line and the scan line, the first transistor being turned on when the scan signal is supplied to the scan line, and transferring the data signal supplied to the data line to the first node; An inverter unit connected between the first node and the organic light emitting diode to control whether the organic light emitting diode emits light in response to the data signal; And a second transistor connected between the first node and a reset line and turned on when a reset signal is supplied to the reset line to switch the organic light emitting diode to a non-light emitting state. The method of claim 1, The inverter unit A first inverter for inverting and supplying the signal of the first node to the organic light emitting diode; And a second inverter for inverting the output signal of the first inverter and supplying the input signal to the input terminal of the first inverter. The method of claim 2, And the second transistor is turned on when the reset signal is supplied to supply a voltage corresponding to a logic value of "1" to the first node. The method of claim 2, The second inverter includes at least one transistor, and the channel width of the first transistor is set to be wider than the channel width of the transistor constituting the second inverter. The method of claim 1, The inverter unit A first inverter and a second inverter connected in series between the first node and the organic light emitting diode; And a third transistor connected between the output terminal of the second inverter and the input terminal of the first inverter. The method of claim 5, And the third transistor is turned off when the scan signal is supplied, and is turned on for another period. The method of claim 5, And the second transistor is turned on when the reset signal is supplied to supply a voltage corresponding to a logic value of "0" to the first node. A scan driver for sequentially supplying scanning signals during the syringe periods included in each of the plurality of subframes included in one frame, and sequentially supplying the reset signals to reset lines during the reset period included in each of the subframes; A data driver for supplying a data signal to data lines during the syringe; And light emitting or non-emitting light for a predetermined time while the data signal is supplied between the syringes, and the pixels are converted into non-emission light during the reset period. The method of claim 8, And a predetermined gray level during the one frame period by using the sum of the times at which the pixels emit light during the sub frame period. The method of claim 8, and a scan signal supplied to an i (i is a natural number) scan line is supplied after a reset signal is supplied to an i th reset line.

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