KR100796480B1 - Driving IC of an active matrix Electroluminesence Device - Google Patents

Abstract

The present invention relates to a driving circuit of an AMELD including a sink current control unit driven by an n-bit image digital input signal, wherein a plurality of reference current sources are arbitrarily combined by a control signal of a plurality of switching elements to provide a reference current of a specific level. A reference current output unit for outputting a; and a sink current control unit for adjusting the level of the sink (sink) current for each RGB in response to a specific reference current output from the reference current output unit.

AMELD, driving circuit

Description

Driving circuit of active matrix electroluminescent device {Driving IC of an active matrix Electroluminesence Device}

1 is a block diagram of a general data driving circuit.

2 is a driving circuit diagram according to a first embodiment of the present invention.

3 is a driving circuit diagram according to a second embodiment of the present invention.

4 is a driving circuit diagram according to a third embodiment of the present invention.

5 is a driving circuit diagram according to a fourth embodiment of the present invention.

6 is a driving circuit diagram according to a fifth embodiment of the present invention.

7 is a driving circuit diagram according to a sixth embodiment of the present invention.

8 is a driving circuit diagram according to a seventh embodiment of the present invention.

9 is a driving circuit diagram according to an eighth embodiment of the present invention.

10 is a driving circuit diagram according to a ninth embodiment of the present invention.

11 is a driving circuit diagram according to a tenth embodiment of the present invention.

* Explanation of symbols on the main parts of the drawings

I1, I2, .., In: reference current source D1, D2, .., Dn: digital input signal

V1, V2: first and second voltage terminals R1, R2: first and second resistors

S1: current disconnect switch Isink: sink current                 

T1, T2: first and second transistors

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit of a display element, and more particularly to a driving circuit of an active matrix electroluminescent device (AMELD) capable of driving with a digital signal.

The AMELD is a light emitting device using electroluminescence, and is divided into a screen display unit and a driving circuit unit formed by attaching electrodes on both sides of a plate-shaped light emitting layer in a matrix form. With its features, thin, light and good color, it is attracting attention as a next-generation flat panel display device according to the enlargement of the screen.

On the other hand, the display device has a few intermediate states between the white and the black state to display a large amount of information, such as color display, to obtain this method of controlling the intensity of the voltage applied to the liquid crystal and the strength of the current How to adjust the.

The method of controlling the intensity of the voltage is to adjust the gradation based on the characteristic that the degree of light transmission is different according to the intensity of the voltage, and adjust the voltage applied from the outside to change the brightness of the screen according to the data voltage. Extract as a parameter for the threshold voltage of.                         

Here, the threshold voltage refers to a voltage at a point where a change in transmittance starts to occur in earnest when the voltage is first applied, and when the threshold voltage is large, the voltage to be applied to the liquid crystal is also increased. In the end, it also increases power consumption.

In addition, since the transmittance with respect to the intensity of the voltage exhibits a proportional curve, it is difficult to adjust the voltage according to the transmittance.

On the other hand, the transmittance of the current intensity is proportional to linear, so the method of controlling the current is much more accurate and easier than the method of adjusting the voltage.

Since the driving circuit of the AMELD according to the prior art is similar to the driving circuit of a general liquid crystal display device, the driving circuit of the liquid crystal display device (hereinafter referred to as LCD) will be described below.

In LCD, an image is displayed by artificially adjusting the degree of light passing through the liquid crystal. As a means of such adjustment, a voltage is mainly used. In general, the transmittance of the liquid crystal changes with a constant relationship depending on the magnitude of the voltage applied across the liquid crystal, that is, the intensity of the electric field passing through the liquid crystal.

To summarize the process of color representation, the amount of light passing through the color filter is controlled by using a liquid crystal, and the voltage required to operate the liquid crystal is output from a source driver IC and supplied through a thin film transistor in a pixel. In this way, the voltage supplied to the liquid crystal changes the transmittance of the liquid crystal. In this case, the number of colors that can be expressed is determined by how many steps the liquid crystal can be controlled. That is, when the liquid crystal is completely opened, it becomes white, and when it is completely closed, it becomes black. When the halftones are combined, various colors are expressed.

SUMMARY OF THE INVENTION An object of the present invention is to provide an AMELD driving circuit which can be integrated into a current driving IC and configured to adjust an output current value for each RGB channel by receiving an n-bit digital signal.

The driving circuit of the active matrix ELD of the present invention for achieving the above object is a reference current output unit for outputting the reference current of a specific level by arbitrarily combining a plurality of reference current sources by a control signal of a plurality of switching elements, and It is characterized in that it comprises a sink current control unit for adjusting the level of the sink (sink) for each RGB in response to a specific reference current output from the reference current output unit.

Hereinafter, the driving circuit of the AMELD according to an embodiment of the present invention with reference to the accompanying drawings in detail as follows.

1 is a configuration diagram of a general data driving circuit.

Referring to FIG. 1, a data driving circuit will be described. A shift register unit may temporarily store a digital signal of RGB input externally by a data clock, and may be received from the shift register unit. A latch unit for latching an RGB digital signal by a control signal, and a digital-to-analog converter for converting an RGB latched digital signal D1 to Dn from the latch unit into an analog signal of RGB. Analog Converter, hereinafter referred to as DAC).                     

At this time, the DAC unit is composed of a plurality of current DAC, each current DAC is a control signal of a plurality of switching elements, that is, the reference current source (I1 ~ In) from the reference block (Reference Block), that is, the digital signal of the RGB ( By outputting a current of a specific level in any combination by D1 to Dn), a specific sink current is sent to a data line connected to each pixel.

Hereinafter, an embodiment of the present invention for the current DAC will be described.

First embodiment

2 is a driving circuit diagram according to a first embodiment of the present invention.

The driving circuit of the AMELD according to the first embodiment of the present invention outputs a reference current of a specific level by arbitrarily combining a plurality of reference current sources I1, I2, ..., In. And a sink current adjuster (II) that receives the reference current output from the reference current output unit and adjusts the level of the sink current.

At this time, the reference current output unit I is supplied with different levels of currents I1, I2, ..., In to the input terminals, and the output terminals thereof are commonly connected to control signals D1, D2,... , Dn) is composed of a plurality of switching elements whose output level is determined.

Here, the switching element is a thin film transistor.

The sink current adjusting unit II includes first and second voltage terminals V1 and V2 and a plurality of transistors forming a current mirror type. The transistor includes a first transistor T1 connected between an output terminal of the reference current output unit I and a first voltage terminal V1, and a second transistor connected to a second voltage terminal V2 and a data line. T2), and the gate of the first transistor T1 and the gate of the second transistor T2 are commonly connected to the reference current output terminal.

In the digital driving circuit, the first voltage terminal V1 is a fixed value, which is mainly used as the ground voltage, but may also be referred to as a positive voltage or a negative voltage. In addition, the second voltage terminal V2 applies a specific voltage value of a different level for each RGB. When the voltage level is adjusted in this way, the level of sink current is increased or decreased so that the data line D / L: A specific voltage level is delivered.

Here, the level of reference currents I1, I2, ... In-1, In can be arbitrarily set. The simplest example is to give a binary weight. In other words, In = 2 In-1 =... = 2 ^n-2 I ₂ = 2 ^n-1 I _{1 ′} Calculate the level of the current that satisfies the equation. In addition, the reference current can be determined by a method called gamma correction.

D1, D2, ..., Dn are digital input signals constituting n bits converted in correspondence with the input analog signals.

Third embodiment

4 is a driving circuit diagram according to a third embodiment of the present invention.

The AMELD driving circuit diagram according to the third embodiment of the present invention also includes a reference current output section I and a sink current control section II.

The reference current output unit I is supplied with different levels of currents I1, I2, ..., In to the input terminals, and the output terminals thereof are commonly connected to control signals D1, D2, .., Dn. It consists of a plurality of switching elements whose output level is determined by.

Here, the switching element is a thin film transistor.

The sink current controller II may include a first transistor T1 and a first resistor R1 connected in series between a first voltage terminal, an output terminal of the reference current output unit, and the first voltage terminal V1. And a second transistor connected between the first voltage terminal V1 and the data line D / L, and the gates of the first transistor and the second transistor are commonly connected to the reference current output terminal.

In more detail, the levels of the reference current sources I1, I2, ..., In are selectively controlled and combined by the plurality of control signals, that is, the digital input signals D1, D2, ..., Dn. The reference current of the specific level output to the reference current output unit is input to the gates of the first and second transistors to control the voltage applied from the first voltage terminal to adjust the sink current value flowing from the data line. In this case, the voltage applied from the first voltage terminal is fixed to any one of a ground voltage, a positive voltage, and a negative voltage.

Then, the first resistor is a variable resistor so that a different level voltage is applied to each RGB to drive each RGB channel.

That is, since the output sink current value of each color can be adjusted by one reference current of the same specific level output from the reference current output unit I, the AMELD driving circuit can be integrated.                     

In the above, the level of the reference current source is arbitrarily set, for example, In = 2 In-1 =. = 2 ^n-2 I ₂ = 2 ^n-1 I _{1 ′} .

Fifth Embodiment

6 is a driving circuit diagram according to a fifth embodiment of the present invention.

As shown in FIG. 6, the AMELD according to an embodiment of the present invention outputs a reference current output unit I for outputting a reference level of a specific level by arbitrarily combining a plurality of reference current sources and the reference current output unit I. It consists of a sink current control unit (II) for receiving the reference current to adjust the level of the sink current.

The reference current output unit I is supplied with reference levels I1, I2, ..., In of different levels to input terminals, and the output terminals thereof are commonly connected to control signals D1, D2, .., Dn. It is composed of a plurality of switching elements whose output level is determined by).

At this time, the switching element is a thin film transistor.

The sink current controller II is a first voltage terminal V1, a second resistor R2, a first connected between the output terminal of the reference current output unit I and the first voltage terminal V1. A current mirror structure includes a second transistor T2 connected in series with a transistor T1 and the second resistor R2 and connected between a data line and the first voltage terminal V1. However, the gates of the first transistor T1 and the second transistor T2 are commonly connected to the output terminal of the reference current output unit.

In this case, the second resistor R2 is directly connected to the first voltage terminal V1. The second resistor R2 fixes the first voltage terminal V1 to a predetermined voltage and changes the resistance value for each RGB. Use to adjust the output sink current for each RGB channel.

In the reference current output unit I, n reference current sources are selected or deselected by n-bit control signals D1, D2,..., Dn, and are integrated and output from the reference current output unit. You can express the desired halftone between and B.

For example, using a 6-bit driver circuit can produce 64 gradations. For monitors requiring full color, more than 16 million colors can be achieved when 256 gradations are achieved.

Seventh embodiment

8 is a driving circuit diagram according to a seventh embodiment of the present invention.

As shown in FIG. 8, the AMELD according to an embodiment of the present invention includes a reference current output unit I for outputting a reference level of a specific level and a sink current control unit II for adjusting the level of a sink current. It consists of.

The reference current output unit I is supplied with reference levels I1, I2, ..., In of different levels to the input terminals, and the output terminals thereof are commonly connected to each other so that the n-bit control signals D1, D2,. Dn) consists of n switching elements whose reference currents are combined to determine a specific output level.

At this time, the switching element is a thin film transistor.

The sink current adjusting unit II includes a first voltage terminal V1, first and second transistors T1 and T2, an output terminal of the reference current output unit I, and the first voltage terminal V1. ) Is composed of first and third transistors T1 and T3 connected in series between the first and third transistors T1 and T3 and second and fourth transistors T2 and T4 connected in series between the first voltage terminal V1 and the data line. The gates of the third transistor and the fourth transistor are commonly connected to the output terminal of the reference current output unit I, and the gate of the first transistor and the gate of the second transistor are controlled to have a constant voltage from the outside. Commonly connected to voltage Vbias.

The Vbias is usually 3.3 volts.

The first voltage terminal is a voltage that is externally controlled and applied to adjust the level of the sink current output for each RGB.

9th embodiment

10 is a driving circuit diagram according to a ninth embodiment of the present invention.

As shown in FIG. 10, the AMELD according to the embodiment of the present invention includes a reference current output unit I and a sink current adjusting unit that receives a reference current output from the reference current output unit and adjusts the level of the sink current ( II).

The reference current output unit I is supplied with n reference currents I1, I2, ..., In of different levels to input terminals, and the output terminals thereof are commonly connected to control signals D1, D2, .. , Dn) is composed of n switching elements in which the reference current is combined to determine an output level.

At this time, the switching element is a thin film transistor.

The sink current controller II may include a first voltage terminal V1, a first transistor T1 connected to a data line, an output terminal of the reference current output unit I, and the first voltage terminal V1. A second transistor T2 connected to the first transistor; and a first and third transistors T1 and T3 connected in series between the first voltage terminal V1 and the data line, and the third transistor T3. The gate of the second transistor T2 is commonly connected to the drain of the first transistor T1, and the gate of the first transistor T1 is connected to the output terminal of the reference current output unit I.

In the above structure, the sink current value for each RGB can be adjusted only by applying different voltages for each RGB to the first voltage terminal under the same digital input signal, thereby enabling integration into a current driving IC.

In the second, fourth, sixth, and eighth embodiments, as shown in FIGS. 3, 5, 7, and 9, the reference current output stage I and the first transistor T1 in the first, third, fifth, and seventh embodiments are illustrated. Further configures a current disconnect switch (S1) between the input terminal of. In addition, as shown in FIG. 11, the tenth embodiment further includes a current interrupt switch S1 between the reference current output terminal I and the input terminal of the second transistor T2 in the ninth embodiment.

The current cutoff switch S1 is configured to electrically separate the reference current output unit I and the sink current control unit II. In order to prevent current consumption by reducing noise generated when the switching element is turned on or off by the control signals D2, ..., Dn.

However, in the present invention, the switching noise generated when the switching element S1 is turned on or off by an n-bit digital input signal, that is, a control signal, is small and thus may be ignored. The structure in which the switching element is ignored is described in Embodiments 1, 3, 5, 7, and 9.

The driving circuit of the AMELD according to the present invention as described above has the following effects.

First, since each RGB can be driven by the same digital input signal, it can be integrated into a current driver IC.

Second, since the noise generated when the digital input signal is turned on or off is small, a structure in which a switching element introduced to reduce switching noise is eliminated is possible.

Claims (25)

A reference current output unit for arbitrarily combining a plurality of reference current sources by a control signal of a plurality of switching elements to output a reference level of a specific level, and receiving a specific reference current output from the reference current output unit for each RGB sink The driving circuit of the AMELD, characterized in that consisting of a sink current control unit for adjusting the level of the current. delete The driving circuit of claim 1, wherein the control signal is a digital input signal converted corresponding to an input video analog signal. The driving circuit of claim 1, wherein the reference current sources are arbitrarily set by one of a binary weight method and a gamma correction method. The driving circuit of AMELD, wherein the switching element is a thin film transistor. The display device of claim 1, wherein the sink current controller comprises a first voltage terminal, a second voltage terminal, a first transistor connected between an output terminal of the reference current output unit and the first voltage terminal, and between the second voltage terminal and the D / L. And a first transistor connected to the second transistor, wherein the first and second transistors have a current mirror structure and are commonly controlled by an output terminal of the reference current output unit. The driving circuit of claim 6, wherein the first voltage terminal is fixed at an arbitrary voltage, and the second voltage terminal applies a specific voltage from RGB to the outside to adjust the level of sink current for each RGB. 7. The driving circuit of AMELD according to claim 6, wherein a current interrupt switch is further configured between the reference current output terminal and the first transistor. The display device of claim 1, wherein the sink current controller comprises: a first transistor connected in series with the first resistor between a first voltage terminal, a first resistor, an output terminal of the reference current output unit, and the first voltage terminal; A first transistor connected between a voltage terminal and a D / L, and the first and second transistors have a current mirror structure and are commonly controlled by an output terminal of the reference current output unit. . 10. The driving circuit of claim 9, wherein the first resistor is a variable resistor connected between the first voltage terminal and the first transistor, the resistance of which is changed for each RGB under a specific reference current. 10. The drive circuit according to claim 9, wherein the first voltage terminal is fixed at a constant voltage value. 10. The driving circuit of claim 9, wherein a current interrupt switch is further configured between the reference current output terminal and the first transistor. The display device of claim 1, wherein the sink current controller comprises a first voltage terminal, a second resistor, a first transistor connected between the output terminal of the reference current output unit and the first voltage terminal, and the first voltage terminal and the D / L. And a second transistor connected in series with the second resistor, wherein the first and second transistors have a current mirror structure and are commonly controlled at an output terminal of the reference current output unit. The driving circuit of claim 13, wherein the first voltage terminal is fixed at a constant voltage value. The driving circuit of claim 13, wherein the second resistor is a variable resistor connected between the first voltage terminal and the second transistor and whose resistance is changed for each RGB under a specific reference current. The driving circuit of claim 13, wherein a current interrupt switch is further configured between the reference current output terminal and the first transistor. The display device of claim 1, wherein the sink current controller comprises: a first transistor connected in series with a first transistor between a first voltage terminal, first and second transistors, an output terminal of the reference current output unit, and the first voltage terminal; And a fourth transistor connected in series with the second transistor between the first voltage terminal and the D / L, wherein the third and fourth transistors have a current mirror structure and are commonly controlled at the output terminal of the reference current output unit. AMELD drive circuit. 18. The driving circuit of claim 17, wherein the gate of the first transistor and the gate of the second transistor are commonly connected to Vbias. 18. The AMELD driving circuit of claim 17, wherein the first voltage terminal is a voltage that is externally controlled to apply a sink current for each RGB. 19. The driving circuit of AMELD according to claim 18, wherein the Vbias is a voltage applied from the outside constantly. 18. The drive circuit according to claim 17, wherein a current interrupt switch is further configured between the reference current output terminal and the first transistor. The display device of claim 1, wherein the sink current controller comprises a first voltage terminal, a first transistor, a second transistor connected between an output terminal of the reference current output unit, and the first voltage terminal, and between the first voltage terminal and the D / L. Is composed of a third transistor connected in series with the first transistor, wherein the second and third transistors have a current mirror structure and are commonly controlled by an output value of a drain of the first transistor. Driving circuit. The driving circuit of claim 22, wherein the gate of the first transistor is connected to an output terminal of a reference current output unit. 23. The driving circuit of claim 22, wherein the first voltage terminal applies a specific voltage from the outside for each RGB. 23. The drive circuit of claim 22, wherein a current interrupt switch is further configured between the reference current output terminal and the second transistor.

Images