KR100667085B1 - Organic electroluminescent display device of commonly using source voltage - Google Patents

Abstract

An organic EL display device using a common source voltage is provided to minimize the variation of a driving current by offsetting the variation of a source voltage by the variation of an image data signal. An organic EL display device includes a voltage supply unit(100), a reference voltage generator(120), a data driver(140), and a panel(160). The voltage supply unit generates an internal source voltage from an external voltage level. The reference voltage generator generates plural reference voltages by using the internal source voltage. The data driver receives the reference voltages and generates an analog image data signal according to received digital image data. The panel receives the internal source voltage and displays an image corresponding to the image data signal. The internal source voltage is used both as an input voltage of the reference voltage generator and a positive source voltage for the pixels in the panel.

Description

Organic Electroluminescent Display Device of commonly using Source Voltage}

1 is a block diagram illustrating an organic light emitting display device according to the prior art.

2 is a block diagram illustrating an organic light emitting display device using a power supply driving circuit according to a first embodiment of the present invention.

3 is a circuit diagram illustrating a pixel circuit configuring a panel unit according to a preferred embodiment of the present invention.

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

Explanation of symbols on the main parts of the drawings

100, 200: power supply unit 120, 220: reference voltage generation unit

140, 260: data driver 160, 280: panel

240: gamma correction unit

The present invention relates to an organic light emitting display device, and more particularly, to a power supply used for a panel of an organic light emitting display device and a power supply used for a data driver.

The organic light emitting device is a display device using an organic light emitting device that is a self-luminous device. In particular, an active matrix type organic light emitting display device includes a driving circuit for each pixel. That is, the organic light emitting diode may implement red, green, and blue colors, and each pixel includes a separate driving circuit for generating a corresponding color with a predetermined luminance.

1 is a block diagram illustrating an organic light emitting display device according to the prior art. Referring to FIG. 1, the organic light emitting display device includes a panel unit 10, a scan driver 20, a data driver 30, and a power supply unit 40.

The panel unit 10 includes a plurality of pixels P11 to Pnm, and the plurality of pixels P11 to Pnm are formed in an area where the data line and the scan line cross each other. In addition, each pixel has an organic light emitting diode that is a self-luminous device, and a driving circuit for driving the organic light emitting diode is provided inside the pixel. The driving circuit provided in the pixel includes a capacitor for storing analog image data applied through a data line and a plurality of transistors for controlling reception of the analog image data.

The scan driver 20 supplies a scan signal to the panel unit 10. The scan signal is supplied to the panel unit 10 through the scan lines. That is, the scan lines are formed through the panel 10 in the same direction.

The data driver 30 supplies an image data signal, which is an analog signal, to the panel unit 10. The image data signal is transmitted through a plurality of data lines that electrically connect the panel unit 10 and the data driver 30.

The power supply unit 40 supplies power to the plurality of pixels P11 to Pnm provided in the panel unit 10. In particular, since the pixel has a driving circuit, a positive power supply voltage and a negative power supply voltage must be supplied to the respective pixels.

The luminance of light emitted from a pixel included in the panel unit 10 is determined according to a positive power supply voltage and a level of an image data signal applied to the pixel. In addition, in FIG. 1, since the power supply unit 40 forms a positive power supply voltage and a negative power supply voltage through a separate process, the level of the power supply voltage supplied from the power supply unit 40 is generated from the data driver 30. It has a value independent of the level of the image data signal.

In the case where the area of the panel becomes large, particularly, a positive power supply voltage must supply power required for the light emitting operation of the organic light emitting element to a plurality of pixels, so that the level reduction in the panel is problematic. That is, the voltage drop in a line to which a positive power supply voltage is applied tends to increase as the area of the panel increases. When the positive power supply voltage drops, the organic light emitting diode does not have a brightness corresponding to the applied analog image data.

An object of the present invention to solve the above problems is to provide an organic light emitting device using a power supply driving circuit that can vary in proportion to the power supply voltage of the pixel and the analog image data applied to the pixel.

The present invention for achieving the above object, the power supply for converting the voltage level received from the outside to generate an internal power supply voltage; A reference voltage generator for forming a plurality of reference voltages using the internal power supply voltage; A data driver for receiving the plurality of reference voltages and generating an image data signal that is an analog signal according to the received digital image data; And a panel unit configured to receive the internal power supply voltage and to display an image corresponding to the image data signal through a plurality of pixels, wherein the internal power supply voltage is equal to an input voltage of the reference voltage generator and the amount of pixels of the panel unit. Provided is an organic light emitting display device, which is used as a power supply voltage.

In addition, the above object of the present invention, the power supply for converting the voltage level received from the outside to generate an internal power supply voltage; A reference voltage generator for forming a plurality of reference voltages using the internal power supply voltage; A gamma correction unit for receiving the plurality of reference voltages and performing gamma correction for each of red, green, and blue; A data driver for receiving gamma correction voltages from the gamma correction unit and generating an image data signal that is an analog signal according to the received digital image data; And a panel unit configured to receive the internal power supply voltage and to display an image corresponding to the image data signal through a plurality of pixels, wherein the internal power supply voltage is an input voltage of the reference voltage generator and an amount of pixels of the panel unit. It can also be achieved through the provision of an organic light emitting device, characterized in that used as the power supply voltage of.

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

First embodiment

2 is a block diagram illustrating an organic light emitting display device using a power supply driving circuit according to a first embodiment of the present invention.

Referring to FIG. 2, the organic light emitting display device includes a power supply unit 100, a reference voltage generator 120, a data driver 140, and a panel unit 160.

The power supply unit 100 receives a voltage applied from an external power source and converts the received voltage level to generate an internal power supply voltage. Preferably, the power supply unit 100 uses a DC-DC converter. The DC-DC converter boosts or steps down the input voltage in the form of DC to form an internal power supply voltage having a predetermined level. The level of the internal power supply voltage formed is about 4.5V to 5.5V. The internal power voltage generated by the power supply unit 100 is supplied to the reference voltage generator 120 and the panel unit 160.

The reference voltage generator 120 receives an internal power supply voltage supplied from the power supply unit 100 and uses it as a positive reference voltage, and receives a power supply voltage applied from the outside and uses it as a negative reference voltage. In addition, the reference voltage generator extracts a reference voltage at a node between the resistors using a plurality of resistors connected in series with each other. The reference voltages extracted by the reference voltage generator 120 may include the red reference voltages REFR1, 2, 3, ..., the blue reference voltages REFB1, 2, 3, ..., and the green reference voltages REFG1, 2, 3 , ... The red reference voltages REFR1, 2, 3, ... are used to convert the red image data RDATA input in the digital form from the data driver 140 into an analog signal. In addition, the blue reference voltages REFB1, 2, 3,... Are used to convert the blue image data BDATA input in the digital form from the data driver 140 into an analog signal, and the green reference voltages REFG1, 2, 3, ... are used to convert the green image data GDATA input in the digital form from the data driver 140 into an analog signal.

The data driver 140 receives the red, blue, and green image data RDATA, GDATA, and BDATA in digital form, and inputs the red, green, and blue reference voltages REFR1,..., REGG1,..., REREF1. Use to form an image data signal which is an analog signal. That is, the red image data RDATA, which is a digital signal, is converted into an analog red data signal DR using the red reference voltages REFR1, .... The converted red data signal DR is supplied to the panel unit 160.

Also, the green image data GDATA, which is a digital signal, is converted into an analog form of the green data signal DG using the green reference voltages REFG1, 2,... It is converted into a blue data signal DB in analog form by using. The converted green data signal DG and the blue data signal DB are supplied to the panel unit 160.

In addition, an internal power supply voltage generated by the power supply unit 100 is applied to the panel unit 160. The internal power supply voltage applied to the panel unit 160 is supplied to each pixel, and the internal power supply voltage supplied to each pixel supplies a driving current required for the light emission operation of the organic light emitting diode provided in the pixel. That is, the internal power supply voltage supplied to the pixel is used as a positive power supply voltage in the pixel.

Therefore, the internal power supply voltage is used to form an image data signal in an analog form, and is used as a positive power supply voltage inside the pixel. Therefore, even if there is a variation in the level of the image data signal due to a change in the internal power supply voltage, the positive power supply voltage in the pixel also has a variation, so that the luminance is substantially the same as the brightness when the change in the internal power supply voltage does not occur. Can be obtained.

3 is a circuit diagram illustrating a pixel circuit configuring a panel unit according to a preferred embodiment of the present invention.

Referring to FIG. 3, the pixel circuit has six transistors, a capacitor C, and an organic light emitting diode OLED. In addition, the pixel circuit is supplied with a positive power supply voltage ELVDD and a negative power supply voltage ELVSS, and the pixel circuit is provided with an image signal D [m], a previous scan signal S [n-1], a current scan signal S [n], and The emission control signal E [n] is applied.

First, the first transistor T1 is connected between the data line 170 to which the image data signal D [m] is supplied and the first node N1. In addition, the current scan signal S [n] is applied to the gate terminal of the first transistor T1. Accordingly, the first transistor T1 performs an on / off operation according to the current scan signal S [n].

The second transistor T2 is connected between the first node N1 and the second node N2. The voltage of the third node N3 is applied to the gate terminal of the second transistor T2.

The third transistor T3 is connected between the second node N2 and the third node N3. The current scan signal S [n] is applied to the gate terminal of the third transistor T3. That is, the current scan signal S [n] is commonly applied to the gate terminal of the first transistor T1 and the gate terminal of the third transistor T3. For example, when the third transistor T3 is turned on, the second transistor T2 has a diode connected structure.

The fourth transistor T4 is connected between the first node N1 and the positive power supply voltage ELVDD. The emission control signal E [n] is applied to the gate terminal of the fourth transistor T4. Therefore, the fourth transistor T4 performs an on / off operation according to the emission control signal E [n].

The fifth transistor T5 is connected between the previous scan signal S [n-1] and the third node N3. In addition, since the gate terminal of the fifth transistor T5 is connected to the drain terminal, it has a diode connected structure.

The sixth transistor T6 is connected between the second node N2 and the organic light emitting diode OLED. The emission control signal E [n] is applied to the gate terminal of the sixth transistor T6. The emission control signal E [n] is commonly applied to the gate terminal of the fourth transistor T4 and the gate terminal of the sixth transistor T6.

The organic light emitting diode OLED is connected between the sixth transistor T6 and the negative power supply voltage ELVSS. The organic light emitting diode OLED emits light with a luminance corresponding to the driving current Idr generated in the second transistor T2.

Capacitor C is connected between positive supply voltage ELVDD and third node N3. The capacitor C stores the image data signal D [m] applied through the data line 170.

First, when the previous scan signal S [n-1] is activated at a low level, only the fifth transistor T5 is turned on. The low level previous scan signal S [n-1] is applied to one terminal of the capacitor C through the turned-on fifth transistor T5, and the capacitor C is initialized.

When the current scan signal S [n] is activated at a low level and the previous scan signal S [n-1] is changed to a high level, the fifth transistor T5 is turned off, and the first transistor T1 and the third transistor T3 are turned on. do. The image data signal D [m] is applied to the first node N1 through the turned-on first transistor T1. In addition, the second transistor T2 is diode-connected by the turned-on third transistor T3. Therefore, if the threshold voltage of the second transistor T2 is called Vth2 and its absolute value is | Vth2 |, the voltage V3 at the third node N3 is given by the following equation (1).

Capacitor C stores positive supply voltage ELVDD and third node voltage V3. Therefore, the voltage difference stored across the capacitor C becomes ELVDD-D [m] + | Vth2 |.

Subsequently, when the light emission control signal E [n] is activated at the low level and the current scan signal S [n] is changed to the high level, the transistors T1 and T3 are turned off and the transistors T4 and T6 are turned on. The positive power supply voltage ELVDD is applied to the first node N1 by the turned-on fourth transistor T4, and the driving current Idr generated in the second transistor T2 flows through the sixth transistor T6 to the organic light emitting diode OLED. The driving current Idr depends on the voltage difference between the source and the gate of the second transistor T2. That is, the driving current Idr is based on Equation 2 below.

If a change occurs in the level of ELVDD, it can be seen that the driving current Idr also changes. In addition, since Idr is proportional to the square of ELVDD, it can be seen that the variation is greater than the level variation of ELVDD. In the present invention, the internal power supply voltage is used as the positive power supply voltage ELVDD, and the internal power supply voltage is used to form the image data signal D [m]. Accordingly, it can be seen that when the positive power supply voltage ELVDD changes, the level of the image data signal D [m] also changes in proportion to the change amount. That is, when the positive power supply voltage has a change amount of? 1, the video signal has a change amount of? 2. The driving current Idr in the case where the positive power supply voltage has a variation amount is given by the following expression (3).

If the internal power supply voltage is not used as a positive power supply voltage, even if a voltage variation occurs in the positive power supply voltage, the level of the video data signal D [m] does not change. That is, a problem arises in that the driving current Idr varies greatly due to the change in the positive power supply voltage. Therefore, when the internal power supply voltage is used as the positive power supply voltage ELVDD and the internal power supply voltage is used to form the image data signal D [m], the variation of the positive power supply voltage or the image data signal D [m] Fluctuations in driving current can be minimized.

Second embodiment

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

Referring to FIG. 4, the organic light emitting diode display according to the present exemplary embodiment includes a power supply unit 200, a reference voltage generator 220, a gamma correction unit 240, a data driver 260, and a panel unit 280. .

The power supply 200 receives a voltage applied from an external power source and converts the received voltage level to generate an internal power supply voltage. Preferably, the power supply 200 uses a DC-DC converter. The DC-DC converter boosts or steps down the input voltage in the form of DC to form an internal power supply voltage having a predetermined level. The level of the internal power supply voltage formed is about 4.5V to 5.5V. The internal power voltage generated by the power supply unit is supplied to the reference voltage generator 220 and the panel unit 280.

The reference voltage generator 220 includes a red reference voltage generator 222, a green reference voltage generator 224, and a blue reference voltage generator 226. Each of the red, green, and blue reference voltage generators 222, 224, and 226 receives an internal power supply voltage supplied from the power supply unit 200, uses it as a positive reference voltage, and receives a power supply voltage applied from the outside, thereby receiving a negative reference voltage. Use as. In addition, each of the red, green, and blue reference voltage generators 222, 224, and 226 extracts a reference voltage at a node between the resistors using a plurality of resistors connected in series with each other.

For example, the red reference voltage generator 222 has a plurality of series resistors and generates reference voltages suitable for the red image. That is, the reference voltages extracted by the red, green, and blue reference voltage generators 222, 224, and 226 may be red reference voltages REFR1, 2, 3,..., Green reference voltages REFG1, 2, 3,. Voltages REFB1,2,3, ... Each of the red, green, and blue reference voltages is input to the gamma correction unit 240.

The gamma corrector 240 includes a red gamma corrector 242, a green gamma corrector 244, and a blue gamma corrector 246. The red reference voltages REFR1,2,3, ... generated by the red reference voltage generator 222 are input to the red gamma correction unit 242, and the green reference voltages REFG1,2,3, ... The green gamma correction unit 244 is input, and the blue reference voltages REFB1, 2, 3,... Are input to the blue gamma correction unit 246. Since the electrical characteristics of the plurality of red, blue, and green pixels constituting the panel unit 280 are different from each other by color, gamma correction is also different from each other. Accordingly, the red gamma correction unit 242 generates red gamma reference voltages γREFR1, 2, 3,... And the green gamma correction unit 244 generates green gamma reference voltages γREFG1, 2, 3,. And the blue gamma correction unit 246 generates the blue gamma reference voltages γREFB1, 2, 3,. The red gamma reference voltages γREFR1, 2, 3,..., The green gamma reference voltages γREFG1, 2, 3,... And the blue gamma reference voltages γREFB1, 2, 3,. ) Is entered.

The red gamma reference voltages γREFR1, 2, 3,... Convert the red image data RDATA input in the digital form from the data driver 260 into an analog signal and supply the red data signal DR supplied to the panel unit 280. Used to form In addition, the green gamma reference voltages γREFG1, 2, 3,... Are used to convert the green image data GDATA input in the digital form from the data driver 260 into the green data signal DG, which is an analog signal. Further, the blue gamma reference voltages γREFB1, 2, 3,... Are used to convert the blue image data BDATA input in the digital form from the data driver 260 into a blue data signal DB which is an analog signal. Therefore, the organic light emitting display device using the reference voltages subjected to gamma correction can overcome the nonlinearity of the pixel and obtain linearity.

The red, green, and blue data signals DR, DG, and DB converted by the data driver 260 are supplied to the panel unit 280. The panel unit 280 includes a plurality of pixels and emits light with luminance corresponding to the red, green, and blue data signals DR, DG, and DB received through the data line. The panel unit 280 displays an image by a predetermined light emission operation.

In addition, an internal power supply voltage generated by the power supply unit 200 is applied to the panel unit 280. The internal power supply voltage applied to the panel unit 280 is supplied to each pixel, and the internal power supply voltage supplied to each pixel supplies a driving current required for the light emission operation of the organic light emitting diode provided in the pixel. That is, the internal power supply voltage supplied to the pixel is used as a positive power supply voltage in the pixel.

Therefore, the internal power supply voltage is used to form an image data signal in an analog form, and is used as a positive power supply voltage inside the pixel. Therefore, even if there is a change in the level of the video signal due to a change in the internal power supply voltage, the positive power supply voltage inside the pixel also has a fluctuation, so that it is substantially the same as the brightness when the change in the internal power supply voltage does not occur. You can get it.

For example, the pixel circuit of FIG. 4 disclosed in the first embodiment is also used as the pixel circuit in this embodiment. That is, when the positive power supply voltage ELVDD changes, it can be seen that the level of the image data signal D [m] also changes in proportion to the change amount. That is, when the positive power supply voltage has a change amount of? 1, the video signal has a change amount of? 2. Since the change amount Δ1 of the positive power supply voltage and the change amount Δ2 of the video signal cancel each other as shown in Equation 2, the amount of change in the driving current Idr is minimized even if the positive power supply voltage or the level of the video signal changes.

If the internal power supply voltage is not used as a positive power supply voltage, even if a voltage variation occurs in the positive power supply voltage, the level of the video data signal D [m] does not change. That is, a problem arises in that the driving current Idr varies greatly due to the change in the positive power supply voltage. Therefore, when the internal power supply voltage is used as the positive power supply voltage ELVDD and the internal power supply voltage is used to form the image data signal D [m], the variation of the positive power supply voltage or the image data signal D [m] Fluctuations in driving current can be minimized.

According to the present invention as described above, the internal power supply voltage generated by the power supply unit can be used to generate an image data signal, and can be used as a positive power supply voltage for driving each pixel of the panel unit. The variation of the positive power supply voltage in the panel portion causes the variation of the image data signal, and the two variations act as factors that cancel each other out to form the driving current. Therefore, the variation of the driving current of the pixel due to the variation of the positive power supply voltage or the image data signal can be minimized.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Claims (7)

A power supply for converting a voltage level received from the outside to generate an internal power supply voltage; A reference voltage generator for forming a plurality of reference voltages using the internal power supply voltage; A data driver for receiving the plurality of reference voltages and generating an image data signal that is an analog signal according to the received digital image data; A panel unit configured to receive the internal power supply voltage and display an image corresponding to the image data signal through a plurality of pixels; And the internal power supply voltage is used as an input voltage of the reference voltage generation unit and a positive power supply voltage of pixels of the panel unit. The organic light emitting device of claim 1, wherein the internal power supply voltage is 4.5V to 5.5V. The organic light emitting device of claim 2, wherein the change amount of the image data signal is proportional to the change amount of the internal power supply voltage. A power supply for converting a voltage level received from the outside to generate an internal power supply voltage; A reference voltage generator for forming a plurality of reference voltages using the internal power supply voltage; A gamma correction unit for receiving the plurality of reference voltages and performing gamma correction for each of red, green, and blue; A data driver for receiving gamma correction voltages from the gamma correction unit and generating an image data signal that is an analog signal according to the received digital image data; And A panel unit configured to receive the internal power supply voltage and display an image corresponding to the image data signal through a plurality of pixels; And the internal power supply voltage is used as an input voltage of the reference voltage generation unit and a positive power supply voltage of pixels of the panel unit. The organic light emitting device of claim 4, wherein the internal power supply voltage is 4.5V to 5.5V. The organic light emitting device of claim 5, wherein the change amount of the image data signal is proportional to the change amount of the internal power supply voltage. The method of claim 6, wherein each pixel of the pixel portion, A first transistor connected between the data line and the first node and configured to perform an on / off operation according to a current scan signal; A second transistor connected between the first node and a second node and configured to generate a driving current according to a voltage of a third node; A third transistor connected between the second node and the third node and configured to perform an on / off operation according to the current scan signal; A fourth transistor connected between the first node and the positive power supply voltage and configured to perform an on / off operation according to an emission control signal; A fifth transistor connected to the third node, having a diode connected structure, and receiving a previous scan signal; A sixth transistor connected to the second node and configured to receive the driving current generated from the second transistor according to a light emission control signal; A capacitor coupled between said positive power supply voltage and said third node, for storing said image data signal transmitted from said data line; And And an organic light emitting device connected between the sixth transistor and a negative power supply voltage and configured to perform a light emitting operation according to a driving current transmitted from the sixth transistor.

Images