KR100844768B1 - Driving circuit and organic electro luminescence display therof - Google Patents

Abstract

SUMMARY OF THE INVENTION An object of the present invention is to precharge a data line to prevent voltage fluctuation due to coupling with adjacent data lines and to reduce the precharge time to reduce the precharge error of the data line and an organic light emitting display using the same. To provide a device.

The present invention provides an organic light emitting display device including a pixel portion, a data driver, and a scan driver, wherein the data driver comprises: a switch unit for selecting a first reference voltage and a second reference voltage in response to a data signal; A precharge voltage generation unit configured to receive the first reference voltage and the second reference voltage in response to a signal and divide the first reference voltage and the second reference voltage to generate a precharge voltage; A gray voltage generator that receives and distributes the first reference voltage and the second reference voltage to generate a gray voltage, and a precharge switch for selectively transferring one of the precharge voltage and the gray voltage to a data line An organic light emitting display device comprising a portion is provided.

Description

Driving circuit and organic light emitting display device using the same {DRIVING CIRCUIT AND ORGANIC ELECTRO LUMINESCENCE DISPLAY THEROF}

1 is a structural diagram showing a structure of an organic light emitting display device according to an exemplary embodiment of the present invention.

2 is a circuit diagram illustrating a resistor unit generating a gray voltage in a general D / A converter.

3 is a structural diagram illustrating a data driver employed in the organic light emitting display device shown in FIG. 2.

4 is a structural diagram showing a structure of a D / A converter according to the present invention.

FIG. 5 is a circuit diagram illustrating an example of a pixel employed in the organic light emitting display device illustrated in FIG. 2.

*** Explanation of symbols on main parts of drawings ***

200: data driver 210: shift register

220: sampling latch 230: holding latch

240: level shifter 250: D / A converter

260: output unit

The present invention relates to a driving circuit and an organic light emitting display device using the same. More specifically, the driving circuit for reducing the gradation error by preventing the voltage drop generated in the analog switch to improve the linearity and the same An organic light emitting display device is used.

 In a flat panel display, a plurality of pixels are arranged on a substrate to form a display area, and a scan line and a data line are connected to each pixel to selectively apply a data signal to the pixel for display.

The flat panel display is classified into a passive matrix type light emitting display device and an active matrix type light emitting display device according to the driving method of a pixel, and is selected and lit for each unit pixel in view of resolution, contrast, and operation speed. Matrix type is the mainstream.

Such a flat panel display device is used as a display device such as a personal information terminal such as a personal computer, a mobile phone, a PDA, or a monitor for various information devices, and includes an LCD using a liquid crystal panel, an organic light emitting display device using an organic light emitting display device, PDPs using plasma panels are known.

Recently, various light emitting display devices having a smaller weight and volume than the cathode ray tube have been developed. In particular, organic electroluminescent display devices having excellent luminous efficiency, brightness, viewing angle, and fast response speed have been attracting attention.

1 is a structural diagram illustrating a structure of a general organic light emitting display device. Referring to FIG. 1, the organic light emitting display device includes a pixel unit 100, a data driver 200, and a scan driver 300.

The pixel unit 100 includes a plurality of data lines D1, D2... Dm-1, Dm and a plurality of scanning lines S1, S2 ... Sn-1, Sn, and a plurality of data lines D1. And a plurality of pixels formed in a region defined by D2 ... Dm-1, Dm and a plurality of scan lines S1, S2 ... Sn-1, Sn. The pixel 101 includes a pixel circuit and an organic light emitting display device, and a data signal and a plurality of scan lines S1 and S2 transmitted through a plurality of data lines D1, D2, ... Dm-1, Dm in the pixel circuit. The pixel current flowing through the pixel is generated by the scan signal transmitted through Sn-1 and Sn so as to flow to the organic light emitting diode.

The data driver 200 is connected to the plurality of data lines D1, D2 ... Dm-1, Dm, and generates a data signal to sequentially convert the data signals of one row into the plurality of data lines D1, D2 .. To .Dm-1, Dm). In addition, the data driver 200 includes a D / A converter to generate a gray voltage obtained by converting a digital signal into an analog signal and transmit the gray voltage to the data lines D1, D2, Dm-1, and Dm.

The scan driver 300 is connected to the plurality of scan lines S1, S2 ... Sn-1, Sn, and generates a scan signal and transmits the scan signal to the plurality of scan lines S1, S2 ... Sn-1, Sn. A specific row is selected by the scan signal, and a data signal is transmitted to the pixel 101 positioned in the selected row, so that a current corresponding to the data signal is generated in the pixel.

FIG. 2 is a circuit diagram illustrating a resistor unit generating a gray voltage in a D / A converter employed in the data driver of the organic light emitting display device shown in FIG. 1. Referring to FIG. 2, it is assumed that the resistor unit generates eight gray voltages. Eight resistors are connected in series to generate eight gradation voltages, and a first reference voltage of high voltage and a second reference voltage of low voltage are transmitted to both ends of the series connected resistors. The voltage divided by the eight resistors becomes the gray scale voltage.

The gray voltage generated in the D / A converter configured as described above is transmitted to the plurality of data lines, and gray voltages having different magnitudes are transmitted. In this case, the coupling between adjacent data lines causes a difference in the gray voltages transmitted to the data lines, thereby preventing the desired luminance from being obtained.

Accordingly, the present invention was created to solve the problems of the prior art, and an object of the present invention is to precharge the data line to prevent voltage fluctuation due to coupling with adjacent data lines and to reduce the time required to precharge the data. The present invention provides a driving circuit and an organic light emitting display device using the same to reduce the precharge error of a line.

A first aspect of the present invention for achieving the above object is an organic light emitting display device including a pixel portion, a data driver and a scan driver, wherein the data driver is a first reference voltage and a second in response to a data signal. A switch unit for selecting a reference voltage; A precharge voltage generation unit configured to receive the first reference voltage and the second reference voltage in response to the data signal, and to divide the first reference voltage and the second reference voltage to generate a precharge voltage; A gray voltage generator configured to receive and distribute the first reference voltage and the second reference voltage in response to the data signal to generate a gray voltage; And a precharge switch unit configured to selectively transfer one of the precharge voltage and the gray scale voltage to a data line.
A second aspect of the present invention for achieving the above object, the switch unit for selecting the first reference voltage and the second reference voltage in response to the data signal; A precharge voltage generation unit configured to receive the first reference voltage and the second reference voltage in response to the data signal, and to divide the first reference voltage and the second reference voltage to generate a precharge voltage; A gray voltage generator configured to receive and distribute the first reference voltage and the second reference voltage in response to the data signal to generate a gray voltage; And a precharge switch unit for selectively transferring one of the precharge voltage and the gray voltage to a data line.
According to a third aspect of the present invention, a first reference voltage and a second reference voltage are selected using upper bits of a data signal, and the first reference voltage is selected using lower bits of the data signal. Dividing the second reference voltage to generate a precharge voltage and transmitting the precharge voltage to a data line; and generating a gray scale voltage by dividing the first reference voltage and the second reference voltage by using a lower bit of the data signal. The present invention provides a method of driving an organic light emitting display device, the method including transmitting the data line.

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Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

3 is a structural diagram showing a data driver employed in the organic light emitting display device according to the present invention. Referring to FIG. 3, the data driver 200 includes a shift register 210, a sampling latch 220, a holding latch 230, a level shifter 240, a D / A converter 250, and an output unit 260. ).

The shift register 210 includes a plurality of flip flops, and controls the sampling latch 220 in response to the clock signal CLK and the synchronization signal Hsync. The sampling latch 220 sequentially receives one row of data signals according to the control signal of the shift register 210 and outputs them in parallel. The method of receiving sequentially and outputting in parallel is called SIPO (Serial In Parallel Out). The holding latch 230 receives the signals in parallel and outputs the signals in parallel again. Input in parallel and output in parallel are called PIPO (Parallel In Parallel Out). The level shifter 240 transfers the signal output from the holding latch 230 to the operating voltage of the system and transfers the level to the D / A converter 250. The D / A converter 250 transfers a signal transmitted as a digital signal as an analog signal, selects a corresponding gray voltage, and transfers it to the output unit 260, and the output unit 260 amplifies the gray voltage and transmits it to the data line. do.

4 is a structural diagram showing a structure of a D / A converter according to the present invention. Referring to FIG. 4, the D / A converter 250 may include a first decoder 251, a first switch unit 252, a second decoder 253, a precharge voltage generator 254, and a gray voltage generator. The unit 255 includes a second switch unit 256 and a mux circuit unit 257.
The first decoder 251 uses a signal of the upper 3 bits of the data signal to generate a first selection signal of 8 bits. In addition, the first switch unit 252 is composed of a total of 16 transistors, each of which is connected to the output terminal of the first decoder 251. The connection relationship of the first switch unit 252 is as follows. The first transistor is connected to v9, the second transistor to v8, the third transistor to v8 and the fourth to v7. In this way, the 15th transistor is connected to v1 and the 16th transistor is connected to v0. In addition, two transistors are connected to each output terminal of the first decoder 251 so that gates of the first transistor and the second transistor are connected to the first output terminal of the first decoder 251, and gates of the third transistor and the fourth transistor are connected to each other. 1 is connected to the second output of the decoder 251. In addition, the gates of the remaining transistors are connected as described above, so that the gates of the two transistors are connected to the respective output terminals of the first decoder 251 so that 16 transistors correspond to the first selection signal of the first decoder 251. To perform the on-off operation. Accordingly, the first switch unit 252 selects and outputs a first reference voltage and a second reference voltage among a plurality of voltages in response to the first selection signal of the first decoder 251.
The second decoder 253 generates a second selection signal by using the lower 3 bit signal of the data signal and transmits the second selection signal to the precharge voltage generator 254 and the voltage gray generator 255. In the precharge voltage generation unit 254, eight resistors are arranged in series, and transistors are formed between the resistors to control ON / OFF in response to the second selection signal. A first switch SW1 and a second switch SW2 are formed at both ends of the precharge voltage generation unit 254 to correspond to a switching operation of the first switch SW1 and the second switch SW2. And a second reference voltage. The precharge voltage generation unit 254 divides the first reference voltage and the second reference voltage by a resistor connected in series to generate eight precharge voltages, and the transistors perform an on / off operation by the second selection signal. To transfer one of the eight precharge voltages to the data line. The first switch SW1 and the second switch SW2 operate in response to the precharge signal.
In the gray voltage generator 255, eight resistors are arranged in series, and transistors are formed between the resistors to control on / off in response to a second selection signal. The gray voltage generator 255 divides the first reference voltage and the second reference voltage by a resistor connected in series to generate eight gray voltages, and the transistors perform the on / off operation by the second selection signal. One of the gray voltages is transferred to the data line.
At this time, since the precharge voltage and the gray voltage use the same first reference voltage and the second reference voltage, the speed at which the gray voltage is transferred to the data line after precharging can be accelerated.
The second switch unit 256 is a means for selectively transferring one of the precharge voltage generated by the precharge voltage generator 254 and the gray voltage generated by the gray voltage generator 255 to the data line. In response to the operations of the first switch SW1 and the second switch SW2 of the precharge voltage generation unit 254. When the first switch SW1 and the second switch SW2 of the precharge voltage generation unit 254 are turned on to generate the precharge voltage, the second switch unit 256 generates a precharge voltage. The signal of the output terminal is transmitted to the data line, and the output terminal of the gray voltage generator 255 is turned off so that the gray voltage is not transmitted to the data line. When the first switch SW1 and the second switch SW2 of the precharge voltage generation unit 254 are turned off, the output terminal of the precharge voltage generation unit 254 is turned off so that the precharge voltage is applied to the data line. The signal of the output terminal of the gray voltage generator 255 is transmitted to the data line.
The mux circuit unit 257 sequentially transmits the gradation voltages to the plurality of data lines, thereby reducing the size of the data driver by reducing the number of output terminals of the data driver compared to the number of data lines. The mux circuit unit 257 sequentially transfers the precharge voltage or the gray voltage to the data line through a separate control switch.

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5 is a circuit diagram illustrating an example of a pixel employed in an organic light emitting display device. Referring to FIG. 5, a pixel is connected to a data line Dm, a scan line Sn, and a pixel power line ELVdd, and includes a first transistor M1, a second transistor M2, a capacitor Cst, and an organic light source. An electroluminescent element (OLED).

The first transistor M1 has a source connected to the pixel power line ELVdd, a drain connected to a source of the third transistor M3, and a gate connected to the first node N. The second transistor M2 has a source connected to the data line Dm, a drain connected to the first node N1, and a gate connected to the scan line Sn. The capacitor Cst is connected between the first node N1 and the pixel power line ELVdd to maintain a voltage between the first node N1 and the pixel power line ELVdd for a predetermined time. The organic light emitting diode OLED includes an anode electrode, a cathode electrode, and a light emitting layer, and the anode electrode is connected to the drain of the first transistor M1, and the cathode electrode is connected to the low potential power source ELVSS so that the first transistor M1 is connected. When a current flows from the organic light emitting diode (OLED) anode electrode to the cathode electrode in response to the voltage applied to the gate, the light is emitted from the light emitting layer and the brightness is adjusted according to the amount of current.

According to the D / A converter and the organic light emitting display device using the same according to the present invention, the precharge voltage is set to a voltage between the first reference voltage and the second reference voltage to increase the speed of precharging so that the signal characteristics are good. To lose.

While preferred embodiments of the present invention have been described using specific terms, such descriptions are for illustrative purposes only and it is understood that various changes and modifications may be made without departing from the spirit and scope of the following claims. You must lose.

Claims (11)

An organic light emitting display device comprising a pixel portion, a data driver, and a scan driver, The data driver, A switch unit which selects a first reference voltage and a second reference voltage in response to a data signal; A precharge voltage generation unit configured to receive the first reference voltage and the second reference voltage in response to the data signal, and to divide the first reference voltage and the second reference voltage to generate a precharge voltage; A gray voltage generator configured to receive and distribute the first reference voltage and the second reference voltage in response to the data signal to generate a gray voltage; And And a precharge switch unit configured to selectively transfer one of the precharge voltage and the gray voltage to a data line. The method of claim 1, An organic light emitting display for transmitting the first reference voltage and the second reference voltage to the precharge voltage generation unit when a first switch and a second switch are formed at both ends of the precharge voltage generation unit to perform precharge. Device. The method of claim 1, The precharge switch unit includes a first precharge switch in an off state in a precharge section and a second precharge switch in an off state in a gray voltage transfer section. The method of claim 1, And the first reference voltage and the second reference voltage are selected using upper bits of the data signal, and the precharge voltage and the gray voltage are selected using lower bits of the data signal. The method of claim 1 An organic light emitting display device having a mux circuit connected to the precharge switch unit so that a plurality of data lines are connected to one precharge switch unit. A switch unit which selects a first reference voltage and a second reference voltage in response to a data signal; A precharge voltage generation unit configured to receive the first reference voltage and the second reference voltage in response to the data signal, and to divide the first reference voltage and the second reference voltage to generate a precharge voltage; A gray voltage generator configured to receive and distribute the first reference voltage and the second reference voltage in response to the data signal to generate a gray voltage; And And a precharge switch unit configured to selectively transfer one of the precharge voltage and the gray voltage to a data line. The method of claim 6, And a first switch and a second switch formed at both ends of the precharge voltage generator to transfer the first reference voltage and the second reference voltage to the precharge voltage generator when the first switch and the second switch are precharged. The method of claim 6, The precharge switch unit includes a first precharge switch in an off state in a precharge section and a second precharge switch in an off state in a gray voltage transfer section. The method of claim 6, And the first reference voltage and the second reference voltage are selected using upper bits of the data signal, and the precharge voltage and the gray voltage are selected using lower bits of the data signal. The method of claim 6 And a mux circuit is connected to the precharge switch to connect a plurality of data lines to one precharge switch. Selecting a first reference voltage and a second reference voltage using upper bits of the data signal; Dividing the first reference voltage and the second reference voltage by using a lower bit of the data signal to generate a precharge voltage and transferring the precharge voltage to a data line; And And dividing the first reference voltage and the second reference voltage by using a lower bit of the data signal to generate a gray voltage and transferring the gray voltage to the data line.

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