KR101609377B1 - Liquid crystal display device - Google Patents

Abstract

A liquid crystal display device comprising: a liquid crystal panel including a gate wiring and a data wiring crossing each other; and a switching transistor connected to the gate wiring and the data wiring; A backlight for supplying light to the liquid crystal panel; A gate driving circuit for outputting a gate high voltage for turning on the switching transistor to the gate wiring; An inverter receiving an inverter driving voltage and outputting a voltage for driving the backlight; And a control PCB on which a timing controller is mounted and which transfers the inverter driving voltage transmitted from the inverter to the gate driving circuit, wherein the inverter driving voltage transmitted to the gate driving circuit is a voltage A display device is provided.

Description

[0001] Liquid crystal display device [0002]

The present invention relates to a liquid crystal display device.

2. Description of the Related Art [0002] With the development of an information society, demands for a display device for displaying images have been increasing in various forms. Recently, a liquid crystal display (LCD), a plasma display panel (PDP) Various flat display devices such as an organic electroluminescent display device (OELD) have been utilized.

Of these flat panel display devices, liquid crystal display devices have recently been widely used because they have advantages of miniaturization, light weight, thinness, and low power driving.

As a liquid crystal display device, an active matrix type liquid crystal display device in which switching transistors are formed in each of pixels arranged in a matrix form is widely used.

In such an active matrix type liquid crystal display device, when a gate wiring is scanned, a gate pulse having a gate high voltage is applied and the switching transistor is turned on. In synchronism with this, the data voltage is transmitted through the data line and applied to the corresponding pixel. Accordingly, the data voltage is applied to the pixel electrode of the pixel, and the corresponding light is emitted.

For such driving, the liquid crystal display device receives the necessary power from the power supply circuit. For example, the power supply circuit generates power supply voltages (VDD and VCC), a gate low voltage (VGL) and a gate high voltage (VGH) and supplies them to the driving circuit of the liquid crystal display device. Such a power supply circuit is mounted on a printed circuit board (PCB).

Here, the gate high voltage VGH is generated through the charge pump circuit of the power supply circuit. The charge pump circuit used to generate the gate high voltage VGH in this way is called a positive charge pump circuit.

1 is a circuit diagram showing a conventional charge pump circuit of a power supply circuit. Referring to FIG. 1, in generating a gate high voltage (VGH), the charge pump circuit requires approximately 20 components, including transistors. Further, a separate switching signal for controlling the switching operation of the transistor is required.

As such, the chargeable charge pump circuit requires a large number of components, which reduces the space efficiency of the PCB on which the power supply circuit is mounted and increases the complexity of the circuit pattern. Further, as many parts are used, the manufacturing cost is increased. Further, electromagnetic interference (EMI) increases due to the switching signal of the transistor.

The present invention has a problem to provide a liquid crystal display device capable of improving space efficiency, manufacturing cost, and EMI of a PCB on which a power supply circuit is mounted.

According to an aspect of the present invention, there is provided a liquid crystal display comprising: a liquid crystal panel including a gate wiring and a data wiring crossing each other; and a switching transistor connected to the gate wiring and the data wiring; A backlight for supplying light to the liquid crystal panel; A gate driving circuit for outputting a gate high voltage for turning on the switching transistor to the gate wiring; An inverter receiving an inverter driving voltage and outputting a voltage for driving the backlight; And a control PCB on which a timing controller is mounted and which transfers the inverter driving voltage transmitted from the inverter to the gate driving circuit, wherein the inverter driving voltage transmitted to the gate driving circuit is a voltage A display device is provided.

Here, the inverter includes: a first connector receiving the inverter driving voltage; A second connector for outputting the input inverter driving voltage; And a transfer wiring for transferring the inverter driving voltage from the first connector to the second connector, wherein the control PCB includes a third connector receiving the inverter driving voltage output from the second connector via a cable can do.

And a power supply circuit mounted on the control PCB and generating a gate low voltage for turning on and off the switching transistor.

The liquid crystal display further comprises a source driving circuit for outputting a data voltage to the data line, the power supply circuit comprising: a charge pump for generating the gate-low voltage; And a boost converter and a buck converter that respectively generate first and second power supply voltages for driving the source driving circuit.

The liquid crystal display further includes a bottom case positioned on a rear surface of the liquid crystal panel, and the control PCB and the inverter may be positioned on the bottom surface of the bottom case.

In the present invention, the inverter driving voltage can be directly used as the gate high voltage. That is, since the inverter driving voltage has a voltage value enough to turn on the switching transistor of the pixel, the inverter driving voltage can be directly used as the gate high voltage.

Accordingly, the power supply circuit does not need to have a separate charge pump, i.e., a positive charge pump, for generating a gate high voltage. As a result, it is possible to reduce the cost of a large number of parts constituting the chargeable charge pump, thereby reducing manufacturing costs for the liquid crystal display device.

In addition, the area occupied by the power supply circuit is reduced, thereby increasing the space efficiency of the control PCB and reducing the complexity of the circuit pattern.

In addition, the transistor used for the positive charge pump is not required, and the EMI due to the switching operation of the transistor can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a block diagram schematically showing a liquid crystal display device according to an embodiment of the present invention, FIG. 3 is an equivalent circuit diagram schematically showing a pixel of a liquid crystal panel according to an embodiment of the present invention, Fig. 2 is a block diagram schematically showing a power supply circuit according to an embodiment of the present invention.

As shown in the figure, the liquid crystal display 100 according to the embodiment of the present invention includes a liquid crystal panel 200, a driving circuit, and a backlight 500. The driving circuit may include a timing controller 310, a gate driving circuit 320, a source driving circuit 330, a power supply circuit 400, and an inverter 450.

The liquid crystal panel 200 includes two substrates facing each other, for example, an array substrate and an opposite substrate, and a liquid crystal layer positioned between these two substrates.

A plurality of gate lines GL extending in the first direction and a plurality of data lines DL extending in the second direction intersect with each other on the array substrate of the liquid crystal panel 200 to form a matrix A plurality of arranged pixels P are defined.

Referring to FIG. 3, each pixel P is formed with a switching transistor T connected to a gate line and data lines GL and DL. The switching transistor T is connected to the pixel electrode. On the other hand, a common electrode is formed corresponding to the pixel electrode, and an electric field is formed between the pixel electrode and the common electrode to drive the liquid crystal. The pixel electrode, the common electrode, and the liquid crystal located between these electrodes constitute a liquid crystal capacitor Clc. Each pixel P further includes a storage capacitor Cst, which serves to store the data voltage applied to the pixel electrode until the next frame.

The timing controller 310 receives control signals and image data Data from an external system such as a TV system or a video card.

The timing controller 310 generates a gate control signal GCS for controlling the gate driving circuit 320 and a source control signal SCS for controlling the source driving circuit 330 using the input control signal do.

The gate drive circuit 320 can sequentially apply gate pulses to the plurality of gate lines GL in response to the gate control signal GCS supplied from the timing controller 310. [ For example, a plurality of gate lines GL are sequentially selected for each frame, and a gate pulse is output to the selected gate line GL. By the gate high voltage VGH of the gate pulse, the switching transistor T located in the corresponding row line is turned on. On the other hand, the gate line voltage VGL is supplied to the gate line GL until the scan of the next frame, so that the switching transistor T maintains the turn-off state.

The source driving circuit 330 supplies the data voltage to the plurality of data lines DL in response to the source control signal SCS supplied from the timing controller 310. [ For example, for the input gamma reference voltages, it is divided through a voltage divider circuit to generate gradation voltages. Such gradation voltages correspond to the respective gradations that the image data Data can have. For example, when the image data Data is n-bit, ²ⁿ gradations (i.e., 0th to ^2n- 1th gradations) may be represented, and thus ²ⁿ gradation voltages are generated Will be.

Therefore, the source driver circuit 330 outputs the gradation voltage corresponding to the gradation of the input image data (Data) as the data voltage to the data line DL. Such a data voltage is output in synchronization with the scan of the gate line GL, and is input to the corresponding pixel P located in the scanned row line.

The backlight 500 serves to supply light to the liquid crystal panel 200. As the backlight 500, a cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL), a light emitting diode (LED), or the like may be used.

The power supply circuit 400 generates a driving voltage for driving elements of the liquid crystal display 100 such as power supply voltages VDD and VCC and a gate low voltage VGL as a power supply element . Here, the power supply voltages VDD and VCC are referred to as first and second power supply voltages (VDD and VCC) for convenience of explanation.

For example, the first and second power supply voltages VDD and VCC may be supplied to the source driver circuit 330 and used as a driving voltage for driving the source driver circuit 330. [ Then, the gate-low voltage VGL is supplied to the gate drive circuit 320. [

4, the power supply circuit 400 includes a boost converter 410 and a buck converter 410. The boost converter 410 generates the drive voltages VDD, VCC, and VGL as described above, A converter 420, and a charge pump 430.

Here, the boost converter 410 boosts or boosts the input voltage VIN to generate the first power supply voltage VDD. Meanwhile, the buck converter 420 bucks up or downs the input voltage VIN to generate the second power supply voltage VCC. Such a charge pump operation is performed through the switching operation of the transistor and the current charging / discharging operation of the inductor in the boost converter 410 and the buck converter 420, respectively, although not shown.

On the other hand, the charge pump 430 reduces the input voltage VIN to generate the gate low voltage VGL. As such, the charge pump 430 is a charge pump used to step down the input voltage VIN, and corresponds to a negative charge pump. Such a boost operation and a buck operation are performed through the switching operation of the transistor and the charge charging / discharging operation of the capacitor in the charge pump 430 although not shown.

As described above, the power supply circuit 400 generates the first and second power supply voltages VDD and VCC and the gate-low voltage VGL. Meanwhile, in generating the driving voltages VDD, VCC, and VGL, the power supply circuit 400 may be controlled by, for example, a pulse width modulation (PWM) method. In the PWM method, the switching operation of the transistor provided in the power supply circuit 400 is controlled by using the PWM signal.

On the other hand, in the embodiment of the present invention, as another driving voltage, the gate high voltage VGH is supplied through the inverter 450. For example, the inverter drive voltage VINV input for driving the inverter 450 is used as the gate high voltage VGH. On the other hand, the inverter 450 generates the backlight driving voltage VB using the inverter driving voltage VINV. The backlight driving voltage VB is supplied to the backlight 500 so that the backlight 500 emits light to supply the liquid crystal panel 200 with light.

5 and 6, a method of using the inverter driving voltage VINV as the gate high voltage VGH will be described in more detail.

FIG. 5 is a rear view of a liquid crystal display module according to an embodiment of the present invention. FIG. 6 is a plan view of a liquid crystal display according to an embodiment of the present invention. FIG. 2 is a view schematically showing an example of the connection relationship of FIG.

5, an inverter 450, a timing controller 310, and a power supply circuit 400 are mounted on a rear surface of a bottom surface of a bottom case 610 of a liquid crystal display module LCM PCB (CPCB) can be located. Here, the PCB (CPCB) on which the timing controller 310 and the power supply circuit 400 are mounted is referred to as a control PCB (CPCB) for convenience of explanation.

The inverter 450 may be provided with, for example, first and second connectors CN1 and CN2. Here, the first connector CN1 corresponds to a configuration for receiving various signals for driving the inverter 450 from the outside. To this end, the first connector CN1 may be provided with a plurality of input pins PIN1. An inverter driving voltage VINV for driving the inverter 450 is inputted through at least one of the plurality of input pins PIN1. For convenience of explanation, the input pin PIN1_V to which the inverter drive voltage VINV is input is referred to as a drive voltage input pin PIN1_V.

The driving voltage input pin PIN1_V is connected to the second connector CN2 through the connection wiring PL patterned to the inverter 450. [ Accordingly, the inverter drive voltage VINV is transmitted to the second connector CN2 through the connection wiring PL.

The second connector CN2 may be provided with at least one output pin PIN2. The control PCB CPCB may be provided with a third connector CN3, for example. The third connector CN3 may include at least one input pin PIN3. Here, each of the output pins PIN2 of the second connector CN2 may correspond to each of the input pins PIN3 of the third connector CN3.

The second and third connectors CN2 and CN3 can be electrically connected to each other through the cable CL. Therefore, the inverter drive voltage VINV transmitted from the first connector CN1 to the second connector CN2 can be transmitted to the third connector CN3 via the cable CL.

The inverter drive voltage VINV transmitted to the control PCB CPCB via the third connector CN3 is transferred from the control PCB CPCB to the gate drive circuit 320 as the gate high voltage VGH. The gate drive circuit 320 outputs the input gate high voltage VGH to the corresponding gate line GL at the time of scanning the gate line GL, T) is turned on.

In this regard, FIG. 6 will be further described with reference to FIG. Referring to FIG. 6, the liquid crystal panel 200 includes an array substrate 210 and a counter substrate 220 which are bonded to each other with a liquid crystal layer interposed therebetween.

The array substrate 210 of the liquid crystal panel 200 is connected to the source PCB SPCB via a flexible film such as a tape carrier package (TCP) film (TCPS) .

Here, a source IC (S-IC) is mounted on the source TCP film (TCPS). The source IC (S-IC) corresponds to a component constituting the source driver circuit 330. The source PCB (SPCB), for example, receives various signals output from the control PCB (CPBC), and performs signal processing when necessary. The signal output through the source PCB (SPCB) is transferred to the source IC (S-IC). Here, the source PCB (SPCB) can be connected to the control PCB (CPCB) via a cable, for example, a flexible flat cable (FFC).

On the other hand, the array substrate 210 can be connected to a flexible film, for example, a gate TCP film (TCPG) along the other edge. A gate IC (G-IC) is mounted on the gate TCP film (TCPG). The gate IC (G-IC) corresponds to the constituent elements constituting the gate drive circuit 320.

Here, the signals necessary for driving the gate IC (G-IC) can be transmitted through the wiring pattern of the source TCP film (TCPS) closest to the gate IC (G-IC). For example, the gate low voltage VGL generated through the power supply circuit 400 and the gate high voltage VGH using the inverter driving voltage VINV are output from the control PCB CPCB and are supplied to the source PCB SPCB, The source TCP film (TCPS), the wiring formed on the array substrate 210, and the gate TCP (TCPG), in this order, to the gate IC (G-IC). In such a case, the gate IC (G-IC) outputs the gate high voltage (VGH) to the scanned gate line (GL) and the gate low voltage (VGL) .

On the other hand, the configuration of the above-described driving circuits is an example, and may be configured in various other ways as needed. For example, a gate PCB may be provided, and in such a case, the gate PCB may be connected to the liquid crystal panel 200 through a gate TCP film (TCPG). A gate drive circuit including at least a part of the functions of the gate IC (G-IC) may be formed directly on the array substrate 210 of the liquid crystal panel 200, which is a so-called GIP (gate in panel) It is called.

On the other hand, the source TCP film (TCPS) and the gate TCP film (TCPG) can be appropriately folded along the side of the support main (not shown) of the liquid crystal display module (LCM), for example, during the modularization process. Thereby, the source PCB (SPCB) can also be positioned on the side of the support main. Thus, the control PCB CPCB can be positioned on the back surface of the bottom case 610. [

Here, the support main is a constitution of a liquid crystal display device module (LCM), and has a rectangular frame shape that covers the edges of a liquid crystal panel 200, a backlight unit 500 and a backlight unit (not shown) do. The liquid crystal display device module LCM may include a top case (not shown), which is located on the front side of the liquid crystal display module LCM, 200 to be displayed externally. The support main body, the bottom case 610 and the top case are coupled to each other to complete the liquid crystal display module LCM.

As described above, in the embodiment of the present invention, the inverter driving voltage VINV can be directly used as the gate high voltage VGH. That is, the inverter drive voltage VINV has a voltage value enough to turn on the switching transistor T of the pixel P, and the inverter drive voltage VINV is set to the gate high voltage VGH You can use it directly.

Accordingly, the power supply circuit 400 does not need to have a separate charge pump or a positive charge pump for generating the gate high voltage VGH. As a result, the cost for a large number of parts constituting the chargeable charge pump can be reduced. For example, a component charge of about $ 0.3 is required for a positive charge pump, which reduces the cost of such components. Accordingly, it is possible to reduce manufacturing costs for the liquid crystal display device.

In addition, the area occupied by the power supply circuit is reduced, thereby increasing the space efficiency of the control PCB and reducing the complexity of the circuit pattern.

In addition, the transistor used for the positive charge pump is not required, and the EMI due to the switching operation of the transistor can be improved.

7 is a graph showing waveforms of gate pulses when the inverter driving voltage is used as a gate high voltage according to an embodiment of the present invention. In Fig. 7, what is indicated in green is a gate start pulse signal which is one of the gate control signals (GCS in Fig. 2). Here, the gate start pulse corresponds to a signal indicating the first row line of the screen. 7, yellow indicates a gate clock signal having a gate pulse according to an embodiment of the present invention.

Referring to FIG. 7, it can be seen that a gate pulse can be normally generated even if a gate high voltage, that is, an inverter driving voltage is used. That is, the gate high voltage according to the embodiment of the present invention has a voltage value substantially equal to the gate high voltage generated using the conventional positive charge pump, so that a normal gate pulse can be generated. Thus, in accordance with the embodiment of the present invention, the switching transistor of the pixel can be normally switched.

The embodiment of the present invention described above is an example of the present invention, and variations are possible within the spirit of the present invention. Accordingly, the invention includes modifications of the invention within the scope of the appended claims and equivalents thereof.

1 is a circuit diagram showing a conventional charge pump circuit of a power supply circuit.

2 is a block diagram schematically illustrating a liquid crystal display device according to an embodiment of the present invention.

3 is an equivalent circuit diagram schematically illustrating a pixel of a liquid crystal panel according to an embodiment of the present invention.

4 is a block diagram schematically illustrating a power supply circuit according to an embodiment of the present invention;

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a liquid crystal display device, and more particularly,

6 is a view schematically showing an example of a connection relationship between a driving circuit and a liquid crystal panel in a liquid crystal display according to an embodiment of the present invention.

FIG. 7 is a graph showing a waveform of a gate pulse when an inverter driving voltage is used as a gate high voltage according to an embodiment of the present invention; FIG.

Description of the Related Art

450: inverter 610: bottom case

LCM: Liquid Crystal Display Module

CPCB: Control PCB

CN1 to CN3: first to third connectors

PL: transmission wiring

CL: Cable

VINV: Inverter drive voltage

VGH: Gate high voltage

PIN1: Inverter input pin

PIN2: Inverter output pin

PIN3: Control PCB input pin

PIN1_V: Inverter drive voltage input pin

Claims (5)

A liquid crystal panel including a gate wiring and a data wiring crossing each other, and a switching transistor connected to the gate wiring and the data wiring; A backlight for supplying light to the liquid crystal panel; A gate driving circuit for outputting a gate high voltage for turning on the switching transistor to the gate wiring; An inverter receiving an inverter driving voltage and outputting a voltage for driving the backlight; And a control PCB on which a timing controller is mounted and which transfers the inverter driving voltage transmitted from the inverter to the gate driving circuit, The inverter drive voltage transmitted to the gate drive circuit is used as the gate high voltage Liquid crystal display device. The method according to claim 1, The inverter includes: a first connector receiving the inverter driving voltage; A second connector for outputting the input inverter driving voltage; And a transfer wiring for transferring the inverter drive voltage from the first connector to the second connector, The control PCB includes a third connector receiving the inverter driving voltage output from the second connector through a cable Liquid crystal display device. The method according to claim 1, And a power circuit mounted on the control PCB to generate a gate low voltage that turns on the switching transistor Liquid crystal display device. The method of claim 3, The liquid crystal display further comprises a source driving circuit for outputting a data voltage to the data line, The power supply circuit comprising: a charge pump for generating the gate low voltage; And a boost converter and a buck converter that respectively generate first and second power supply voltages for driving the source driver circuit Liquid crystal display device. The method according to claim 1, The liquid crystal display device may further include a bottom case positioned on a rear surface of the liquid crystal panel, The control PCB and the inverter are disposed on the bottom surface of the bottom case Liquid crystal display device.

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