KR20050018287A - Driving IC of Liquid Crystal Display - Google Patents

Abstract

PURPOSE: A circuit for driving the liquid crystal display device is provided to implement the accurate gray level voltage to the liquid crystal panel as well as to make the thickness of the module of the liquid crystal device thin. CONSTITUTION: A circuit for driving the liquid crystal display device includes a timing controller, a source driver(360), a gate driver, a liquid crystal panel and a power unit. The power unit is provided with a DC/DC converting unit, a delay circuit(350) and a power supplying unit(330). The DC/DC converting unit outputs the gray voltage inputted into the source driver and the supply voltage of the source driver. The delay circuit outputs the supplying voltage of the source driver inputted from the DC/DC converting unit and the gray level voltage to the source driver sequentially. And, the power supplying unit supplies the power to the DC/DC converting unit.

Description

Driving circuit for liquid crystal display device {Driving IC of Liquid Crystal Display}

The present invention relates to a driving circuit of a liquid crystal display device, and more particularly, to configure a driving voltage of a source drive IC to be stably supplied through a DC / DC converter. The purpose of the present invention is to achieve stabilization of input power in liquid crystal display devices.

TFT-LCD (Thin Film Transistor-Liquid Crystal Display) is a display device used for character graphic display devices such as notebooks and monitors, and has an average power consumption of 30 to 40% compared to conventional CRT (Cathode Lay Tube). It is also an information display device that the heat generation amount is small and the market scale is gradually increasing.

In general, a liquid crystal display device is configured such that one thin film transistor corresponds to one liquid crystal cell, and a thin film transistor type liquid crystal display device having a predetermined number of cells has a high contrast ratio, and is used for gray scale display or copper screen display. It is suitable and is particularly in the spotlight among various kinds of liquid crystal display devices because of its advantages of easy full colorization. In addition, it can be applied to fields such as high-definition television (HD TV: High Definition Television) because it can be large-capacity without compromising image quality.

Such a liquid crystal display device is a device that displays a desired image by individually supplying data signals according to image information to liquid crystal cells arranged in a matrix form, and adjusting light transmittance of the liquid crystal cells.

Therefore, the liquid crystal display device includes a liquid crystal panel in which liquid crystal cells forming a pixel unit are arranged in an active matrix form, and a drive circuit for driving the liquid crystal cells.

In this case, the liquid crystal panel includes a color filter substrate on which a color filter is formed and a TFT array substrate on which a thin film transistor (TFT) is formed are separated by a spacer to sealant. It adheres by using and the liquid crystal is inject | poured into the space | interval space between board | substrates.

Common electrodes and pixel electrodes are formed on opposite inner surfaces of the color filter substrate and the thin film transistor array substrate to apply an electric field to the liquid crystal layer. In this case, the pixel electrode is formed for each liquid crystal cell on the thin film transistor array substrate, while the common electrode is integrally formed on the entire surface of the color filter substrate. Therefore, by controlling the voltage applied to the pixel electrode in a state where a voltage is applied to the common electrode, it is possible to individually control the light transmittance of the liquid crystal cells.

Further, on the thin film transistor array substrate of the liquid crystal panel, a plurality of data lines for transmitting the data signal RGB data supplied from the source driver unit to the liquid crystal cells, and a scan signal supplied from the gate driver unit are transferred to the liquid crystal cells. The plurality of gate lines are orthogonal to each other, and liquid crystal cells are defined at each intersection of these data lines and the gate lines.

In this case, the gate drive unit sequentially supplies scan signals to the plurality of gate lines, so that the liquid crystal cells arranged in a matrix form are sequentially selected one by one, and the selected one line of liquid crystal cells is provided from the source driver unit. The data signal is supplied.

In order to control the voltage applied to the pixel electrode for each liquid crystal cell, a thin film transistor used as a switching element is formed in each liquid crystal cell, and the liquid crystal cells supplied with the scan signal to the gate electrode of the thin film transistor through the gate line. In this case, a conductive channel is formed between the source / drain electrodes of the thin film transistor, wherein a data signal supplied to the source electrode of the thin film transistor through the data line is supplied to the pixel electrode through the drain electrode of the thin film transistor. The light transmittance of the cell is controlled.

1 is a block diagram schematically illustrating a driving circuit of the above-described general liquid crystal display device.

As shown in FIG. 1, the driving circuit of the liquid crystal display device includes a driving system 100, an interface 110, a timing controller 120, a power supply 130, and a DC / DC converter. A DC / DC converter: 140, a source drive IC 150, a gate drive IC 160, and a liquid crystal panel 170 are provided.

The interface unit 110 applies R (Red), G (Green), and B (Blue) signals, which are image data signals input from the driving system 100, to the liquid crystal panel.

The timing controller 120 receives various data signals from the interface unit 110 and generates various control signals and data to stably drive the liquid crystal panel.

The source driver 150 converts the data signal from the timing controller 120 into an analog signal and applies a voltage to each data line of the liquid crystal panel 170.

The gate driver 160 receives a display control signal received from the timing controller 120 and applies a pulse voltage to each gate line.

The power supply unit 130 receives power from the driving system 100 and applies power required for each unit.

The DC / DC converter 140 generates various voltages used in the liquid crystal module, for example, Vdd, Vgon, Vgoff, and Vref, by using the input voltage Vin received from the power supply 130. Here, the Vdd voltage is a supply voltage of the source drive unit 150, the Vref voltage is a reference voltage required for the digital-to-analog conversion of the source drive unit 150, and the Vgon voltage is used to drive the liquid crystal panel. The voltage turns on the thin film transistor, and the Vgoff voltage is a voltage turning off the thin film transistor.

In general, a driving voltage sequence specification for driving a source driver of a liquid crystal display is as follows. When the power of the liquid crystal display is turned on, a logic supply voltage (VL voltage) is input from a input voltage Vin to a logic circuit in the timing controller 120. Then, a control signal (Control Signal) is input from the timing controller 120 to the source drive unit 150. The Vdd voltage of the source drive unit is input to the source drive unit 150.

Thereafter, the Vref voltage is input to the source driver 150 from the DC / DC converter 140.

On the contrary, when the power of the liquid crystal display is turned off, the power is turned off in the order of Vref voltage, Vdd voltage, control signal, and VL voltage.

However, unlike the above-mentioned driving voltage sequence specification, the driving voltage sequence of the source drive unit of the liquid crystal display which is actually implemented is as follows. Hereinafter, it demonstrates based on FIG. 2 is a block diagram illustrating a driving voltage of a source driver of a general liquid crystal display.

Referring to FIG. 2, when the power of the liquid crystal display is turned on, the VL voltage is input from the input voltage Vin to the logic circuit of the timing controller 120. In addition, a control signal is input from the timing controller 120 to the source driver 160. In addition, the Vdd voltage and the Vref voltage are simultaneously input to the source drive unit 160 by the DC / DC converter 140 receiving the branched power from the power supply unit 130.

That is, unlike the driving voltage sequence specification of the source drive unit in which the Vdd voltage and the Vref voltage are sequentially input, the Vdd voltage and the Vref voltage are simultaneously input in an actual circuit. Therefore, since the Vref voltage is input before the source drive unit 160 stabilizes with the Vdd voltage, accurate gray scale voltage is difficult to be implemented in the liquid crystal panel.

In addition, since the load in the liquid crystal display increases due to the high resolution and the enlargement of the liquid crystal panel, a power source having a large current driving capability is required. Therefore, in the case of the DC / DC converter having a large current driving capability, the size of the package is large and the production cost increases.

SUMMARY OF THE INVENTION In view of the above, an object of the present invention is to realize an accurate gray scale voltage in a liquid crystal panel than a driving circuit of a general liquid crystal display device, and to optimize the driving circuit of a liquid crystal display device having a thinner module and a lower production cost. To provide.

In order to achieve the above object of the present invention, the driving circuit of the liquid crystal display according to an embodiment of the present invention includes a timing controller for outputting RGB data and control signals to implement a predetermined screen; A source driver for inputting the RGB data, the control signals and the gray voltage to output a source signal; A gate driver configured to output a gate signal by applying the control signals and a gate turn on / turn off voltage; A liquid crystal panel displaying a predetermined screen by the source signal and the gate signal; And a power supply unit receiving an input voltage from the outside and applying predetermined voltages to the timing controller, the source drive unit, and the gate drive unit, respectively.

The power supply unit may include a DC / DC converter for outputting a gray voltage entering the source drive unit and a supply voltage of the source drive unit; A delay circuit unit sequentially outputting a supply voltage and a gray level voltage input from the DC / DC converter to the source drive unit; And a power supply unit supplying power to the DC / DC converter.

Preferably, the DC / DC converter includes a first DC / DC converter for outputting a gray voltage and a second DC / DC converter for outputting a supply voltage of a source driver.

The delay circuit unit may output a gray voltage after outputting a supply voltage of the source drive unit.

Preferably, the delay circuit unit is configured of a delay circuit including a capacitor.

Hereinafter, preferred embodiments of the present invention will be introduced in order to enable those skilled in the art to more easily implement the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to FIG. 3 is a block diagram schematically illustrating a driving circuit of a liquid crystal display according to an exemplary embodiment of the present invention.

As shown in FIG. 3, the driving circuit of the liquid crystal display device includes a driving system 300, an interface 310, a timing controller 320, a power supply 330, and a DC / DC converter. A DC / DC converter 340, a delay circuit unit 350, a source drive IC 360, a gate drive IC 370, and a liquid crystal panel 380 are included.

At this time, the overall configuration of the liquid crystal display device according to an embodiment of the present invention is the same as the driving circuit of the conventional liquid crystal display device, the description of the following configuration is omitted, and receives the input voltage from the outside and the timing controller 320 and the A power supply unit 400 that applies a predetermined voltage to the source drive unit 360 and the gate drive unit 370 will be described. In particular, the DC / DC converter providing the supply voltage and the gray voltage of the source driver 360 will be described in detail.

First, as shown in FIG. 3, the power supply unit 400 according to an embodiment of the present invention includes a power supply unit 330, a DC / DC converter 340, and a delay circuit unit 350.

The power supply unit 330 receives power from the driving system 300 and applies power required for each unit. The power supply unit 330 outputs a logic supply voltage (VL voltage) from an input voltage Vin to a logic circuit in the timing controller 320.

The DC / DC converter 340 generates various voltages used in the liquid crystal module, for example, Vdd, Vgon, Vgoff, and Vref, by using the input voltage Vin applied from the power supply 330. Here, the Vdd voltage is a supply voltage of the source drive unit 360, the Vref voltage is a reference voltage required for the digital-to-analog converter of the source drive unit 360, and the Vgon voltage is used to drive the liquid crystal panel. The voltage turns on the thin film transistor, and the Vgoff voltage is a voltage turning off the thin film transistor.

The delay circuit 350 receives the Vref voltage and the Vdd voltage from the DC / DC converter 340 and sequentially outputs the Vref voltage and the Vdd voltage to the source driver 360.

In more detail, FIG. 4 is a block diagram illustrating driving voltages of a source driver of a liquid crystal display according to an exemplary embodiment of the present invention.

As shown in FIG. 4, the first DC / DC converter 410 and the second DC / DC converter 420 receive an input voltage Vin from the power supply unit 330. The first DC / DC converter 410 outputs the supply voltage Vdd of the source drive unit 360 from the input power source Vin. The second DC / DC converter 420 outputs a reference voltage Vref required for the digital / analog converter D / A converter of the source drive unit 360 from the input power source Vin.

As described above, when the DC / DC converter 340 for supplying power to the source drive unit 360 is separated into first and second DC / DC converters for outputting a Vref voltage and a Vdd voltage, respectively, one DC / DC converter is used. The current driving capability of each of the first and second DC / DC converters 410 and 420 may be smaller than that of the converter 340. In addition, in the case of the second DC / DC converter 420, the Vref voltage output from the second DC / DC converter 410 acts as a voltage source for forming the gray level of each RGB data. In the case of the first DC / DC converter 410, an appropriate integrated circuit may be selected in consideration of the load of the liquid crystal panel, and thus, a driving circuit optimized for the size and power consumption may be formed.

The delay circuit 350 prevents the Vdd voltage output from the first DC / DC converter 410 and the Vref voltage output from the second DC / DC converter 420 from being simultaneously applied to the source driver 360. do. That is, by the delay circuit unit 350, the Vdd voltage is first applied to the source drive unit 360 to stabilize the source drive unit 360, and then the Vref voltage is applied to implement the accurate gray level voltage in the liquid crystal panel. .

The delay circuit unit 350 is preferably composed of a delay circuit including a capacitor (capacitor).

5 is a circuit diagram illustrating a delay circuit unit 350 according to an exemplary embodiment of the present invention.

As shown in FIG. 5, the Vdd voltage output from the first DC / DC converter 410 is directly input to the source driver 360. In this case, the Vref voltage output from the second DC / DC converter 420 may be sourced after a predetermined time when a predetermined charge is charged in the capacitor C connected to the first DC / DC converter 410. It is input to the drive unit 360.

That is, when the Vdd voltage is output from the first DC / DC converter 410, charge is started to be charged in the capacitor C by the distribution ratios of the resistors R1 and R2. In the state where there is no charge in the capacitor C initially, the transistors Q1 and Q2 are turned off, and since the current does not flow through the resistors R3 and R4, the transistor Q3 is also turned off. In this case, the Vref voltage output from the second DC / DC converter 420 is not input to the source driver 360.

When a predetermined time passes and the charge is charged in the capacitor C and the voltage applied between the capacitor C reaches a voltage at which the transistors Q1 and Q2 can be turned on, current flows in the resistors R3 and R4. Accordingly, the transistor Q3 is turned on by the voltage difference across the resistor R3, and the Vref voltage output from the second DC / DC converter 420 is input to the source driver 360.

Therefore, after a predetermined time passes after the Vdd voltage is output to the first DC / DC converter 410, when a voltage capable of turning on the transistors Q1, Q2, and Q3 is applied across the capacitor C, the second DC is applied. The Vref voltage output from the / DC converter 420 is input to the source driver 360. That is, a delay occurs between the Vdd voltage and the Vref voltage.

In an embodiment of the present invention, the delay circuit unit 350 has been described using a Darlington circuit 430. However, the application of the present invention includes all delay circuits such as resistors and capacitors or transistors and capacitors. to be.

As mentioned above, although the present invention has been described with reference to preferred embodiments, the present invention is not limited to the above embodiments, and various modifications may be made by those skilled in the art within the scope of the technical idea of the present invention.

As described above, according to the driving circuit of the liquid crystal display device, an accurate driving voltage of the liquid crystal panel can be realized, the module thickness of the liquid crystal display device is thin, and the production cost is low. Can be provided.

1 is a block diagram schematically illustrating a driving circuit of a general liquid crystal display device.

2 is a block diagram illustrating a driving voltage of a source driver of a general liquid crystal display.

3 is a block diagram schematically illustrating a driving circuit of a liquid crystal display according to an exemplary embodiment of the present invention.

4 is a block diagram illustrating driving voltages of a source driver of a liquid crystal display according to an exemplary embodiment of the present invention.

(Explanation of symbols for the main parts of the drawing)

300: drive system 310: interface unit

320: timing controller 330: power supply

340: DC / DC converter 350: delay circuit

360: source drive unit 370: gate drive unit

380: liquid crystal panel

Claims (4)

A timing controller configured to output RGB data and control signals to implement a predetermined screen; A source driver for inputting the RGB data, the control signals and the gray voltage to output a source signal; A gate driver configured to output a gate signal by applying the control signals and a gate turn on / turn off voltage; A liquid crystal panel displaying a predetermined screen by the source signal and the gate signal; And a power supply unit receiving an input voltage from an external source and applying predetermined voltages to the timing controller, the source drive unit, and the gate drive unit, respectively. The power supply unit A DC / DC converter for outputting a gray voltage entering the source drive unit and a supply voltage of the source drive unit; A delay circuit unit sequentially outputting a supply voltage and a gray level voltage input from the DC / DC converter to the source drive unit; And a power supply unit supplying power to the DC / DC converter. The method of claim 1, And the DC / DC converter comprises a first DC / DC converter for outputting a gradation voltage and a second DC / DC converter for outputting a supply voltage of a source drive unit. The method of claim 2, And the delay circuit unit outputs a gray voltage after outputting a supply voltage of the source driver unit. The method of claim 3, wherein And the delay circuit unit comprises a delay circuit including a capacitor.