KR100793579B1 - 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 unit, a data driver, and a scan driver, wherein the data driver comprises: a first switch unit selecting a first reference voltage in response to a data signal; A second switch unit selecting a second reference voltage in response to the data signal; A gray voltage generator configured to receive and distribute the first reference voltage and the second reference voltage to generate a gray voltage; A third switch unit which selects and outputs a gray voltage generated by the gray voltage generator in response to the data signal; And a precharge circuit configured to receive the selected first reference voltage and the selected second reference voltage to generate an intermediate voltage between the first reference voltage and the second reference voltage to precharge the data line. To provide.

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: buffer 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 a organic light emitting display device including a pixel portion, a pixel portion, a data driver and a scan driver, wherein the data driver is a first reference voltage in response to a data signal. And a switch unit for selecting a second reference voltage, and receiving the first reference voltage and the second reference voltage in response to the data signal, and distributing the first reference voltage and the second reference voltage to generate a precharge voltage. A precharge voltage generation unit configured to receive and distribute the first reference voltage and the second reference voltage in response to the data signal to generate a gray scale voltage, and one of the precharge voltage and the gray voltage. An organic light emitting display device including a precharge switch unit for selectively transferring a voltage to a data line is provided.

According to a second aspect of the present invention, a first switch unit selecting a first reference voltage and a second reference voltage in response to a data signal, and receives the first reference voltage and the second reference voltage A resistor for dividing to generate a gray voltage, a second switch unit for selecting and outputting a gray voltage generated in the resistor according to the data signal, and receiving the selected first reference voltage and the selected second reference voltage; The present invention provides a driving circuit including a precharge circuit which generates an intermediate voltage between a first reference voltage and the second reference voltage and precharges 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. And generating a gray voltage by dividing the second reference voltage, precharging a data line using a voltage between the first reference voltage and the second reference voltage as a precharge voltage, and generating the gray voltage. The present invention provides a method of driving an organic light emitting display device, the method including transmitting the data line.

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 a buffer 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 buffer unit 260. The buffer unit 260 amplifies the gray voltage and transfers 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 includes a first decoder 251, a switching unit 252, a second decoder 253, a precharge voltage generation unit 254, a gray voltage generation unit 255, The precharge switch unit 256 and the second precharge switch 255b, the third precharge switch unit 256 and the resistors Ra and Rb are included.

The first calculating unit 251 uses a signal of the upper three bits of the data signal to generate eight signals. In addition, the first switching unit 252 is composed of a total of 16 transistors, each of which is connected to the output terminal of the first operation unit 251 by two. The connection relationship of the first switching 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 operation unit 251 so that gates of the first transistor and the second transistor are connected to the first output terminal of the first operation unit 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 operation unit 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 calculator 251 so that 16 transistors correspond to the output signal of the first calculator 251. The on-off operation is performed.

The second calculator 253 generates a signal using the lower 3 bit signal of the data signal and transmits the signal to the voltage gray scale generator 254. The voltage gradation generation unit 254 has eight resistors connected in series, and receives the first reference voltage and the second reference voltage selected by the first switching unit 252 at both ends thereof, and the eight reference resistors provide the first reference voltage and the second reference voltage. Two reference voltages are divided into eight voltages. The eight resistors may have the same size or different sizes. At this time, the gray voltage generator 254 forms a transistor between each resistor, and selects one of eight voltages as a gray voltage by the switching operation of the transistor and outputs the gray voltage. The switching operation of the transistor is determined by the second calculator 253.

The gray voltage generated by the gray voltage generator 254 is transferred to the data line. The data line is precharged to the precharge signal and then the gray voltage is transferred to the data line. Prevent voltage fluctuations caused by coupling. In the precharge signal transmitted to the data line, a voltage between the first gray voltage and the second gray voltage is transmitted, and the precharge signal is formed by the precharge circuit. The precharge circuit is formed of a first precharge switch 255a, a second precharge switch 255b, a third precharge switch 256 and resistors Ra and Rb, and the first precharge switch 255a The first reference voltage is switched, and the second precharge switch 255b switches the second reference voltage. In addition, the third precharge switch 256 switches the gray voltage, and the resistors Ra and Rb divide the first reference voltage and the second reference voltage as resistors and transmit the divided reference voltages to the data lines. The first precharge switch 255a and the second precharge switch 255b perform the same operation, and the third precharge switch 256 performs the first precharge switch 255a and the second precharge switch 255b. Is turned off when is turned on, and turned on when the first precharge switch 255a and the second precharge switch 255b are turned off, and the gray scale voltage is applied to the data line when the precharge signal is transmitted to the data line. It is prevented from being transmitted to and transfers the gradation voltage to the data line after being precharged. The resistors Ra and Rb divide the first reference voltage and the second reference voltage by two resistors so that the precharge voltage has a voltage between the first reference voltage and the second reference voltage so that the precharge voltage is reduced. 2 Let it precharge faster than the reference voltage. In addition, the first, second and third precharge switches 255a, 255b, and 256 receive and operate separate precharge signals.

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 (12)

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, The precharge voltage generation unit selectively distributes the switch to receive the first reference voltage and the second reference voltage, and the precharge voltage generating a plurality of precharge voltages by distributing the first reference voltage and the second reference voltage. And a second switch unit configured to select one of a distribution unit and one of the plurality of precharge voltages and transmit the selected voltage to the data line. The method of claim 2, And the switch is formed at both ends of the precharge voltage divider to transfer the first reference voltage and the second reference voltage to the precharge voltage divider when precharged. The method of claim 1, The gray voltage generator selects one gray voltage among the gray voltage voltage divider and the plurality of gray voltages to receive and distribute the first reference voltage and the second reference voltage to generate the plurality of gray voltages. An organic light emitting display device comprising a third switch unit for transmitting. 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 first switch unit selecting a first reference voltage and a second reference voltage in response to the data signal; A resistor configured to receive and distribute the first reference voltage and the second reference voltage to generate a gray scale voltage; A second switch unit which selects and outputs a gray voltage generated by the resistor in response to the data signal; And And a precharge circuit configured to receive the selected first reference voltage and the selected second reference voltage to generate an intermediate voltage between the first reference voltage and the second reference voltage to precharge the data line. The method of claim 8, The precharge circuit includes a selector configured to select one of the first reference voltage and the second reference voltage, and a transfer unit configured to transfer one of the first reference voltage and the second reference voltage. The method of claim 8, And the precharge circuit precharges the data line using a voltage obtained by dividing the first reference voltage and the second reference voltage. Selecting a first reference voltage and a second reference voltage using upper bits of the data signal; 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; Precharging a data line using a voltage between the first reference voltage and the second reference voltage as a precharge voltage; And And transmitting the generated gray voltage to the data line. The method of claim 11, And the precharge voltage is generated by dividing the first reference voltage and the second reference voltage by using a resistor.

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