KR20090034212A - Apparatus and method for driving backlight of liquid crystal display device - Google Patents

Apparatus and method for driving backlight of liquid crystal display device Download PDF

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Publication number
KR20090034212A
KR20090034212A KR1020070099476A KR20070099476A KR20090034212A KR 20090034212 A KR20090034212 A KR 20090034212A KR 1020070099476 A KR1020070099476 A KR 1020070099476A KR 20070099476 A KR20070099476 A KR 20070099476A KR 20090034212 A KR20090034212 A KR 20090034212A
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KR
South Korea
Prior art keywords
pulse width
voltage
inverter
supplied
width modulation
Prior art date
Application number
KR1020070099476A
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Korean (ko)
Inventor
박동서
이정환
Original Assignee
엘지디스플레이 주식회사
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Priority to KR1020070099476A priority Critical patent/KR20090034212A/en
Publication of KR20090034212A publication Critical patent/KR20090034212A/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/13306—Circuit arrangements or driving methods for the control of single liquid crystal cells
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source

Abstract

The present invention relates to a technology for integrally implementing the functions of an internal synchronous inverter and an external synchronous inverter as one inverter in a backlight unit of a liquid crystal display. The present invention includes a pulse width modulation signal selection control unit which checks whether a pulse width modulation signal or a DC voltage is supplied to an inverter from the outside and controls them to be selectively transmitted to an external pulse width modulation unit or an internal pulse width modulation unit; An internal pulse width modulator selected by the pulse width modulated signal selection controller and configured to generate a pulse width modulated signal from a DC voltage supplied from the outside and a triangle wave generated internally and supply the pulse width modulated signal to an inverter integrated device; It is selected by the pulse width modulation signal selection control unit, and is achieved by an external pulse width modulation unit for transmitting the pulse width modulation signal supplied from the outside to the inverter integrated device.

Description

Backlight driving device and method for liquid crystal display device {APPARATUS AND METHOD FOR DRIVING BACKLIGHT OF LIQUID CRYSTAL DISPLAY DEVICE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight driving technology of a liquid crystal display device, and more particularly, to a backlight driving device and a method of a liquid crystal display device capable of integrally implementing an internal synchronous inverter and an external synchronous inverter.

Recently, with the development of information technology (IT), the importance of the display as a visual information transmission medium is further emphasized, and in order to secure competitiveness in the future, low power consumption, thinness, light weight, and high quality are required.

A liquid crystal display (LCD), which is a typical display device of a flat panel display device, is an apparatus for displaying an image using optical anisotropy of liquid crystal, and has advantages such as thin, small size, low power consumption, and high quality.

Such a liquid crystal display device is a display device in which image information is individually supplied to pixels arranged in a matrix, and a desired image is displayed by adjusting light transmittance of the pixels. Accordingly, the liquid crystal display includes a liquid crystal panel in which pixels, which are the smallest unit for implementing an image, are arranged in an active matrix form, and a driving unit for driving the liquid crystal panel. Since the LCD does not emit light by itself, a backlight unit is provided to supply light to the LCD.

1 is a block diagram showing a basic configuration of a backlight driving apparatus according to the prior art, as shown therein, an inverter integrated element 11A for converting a DC voltage into an AC voltage using a switching element such as a transistor; The transformer 11B is configured to boost the AC voltage input from the inverter integrated element 11A and supply the boosted voltage to the backlight lamp 12.

The inverter integrated element 11A converts the power terminal voltage Vcc, which is a DC voltage, into an AC voltage by using a switching element (for example, a FET) switched by the pulse width modulation signal PWM.

The transformer 11B converts the converted AC voltage into an AC voltage of a required high voltage and outputs the same to the lamp 12.

Accordingly, the lamp 12 is turned on by the high voltage AC voltage input from the transformer 11B to illuminate the backlight on the liquid crystal panel.

Substantially, the inverter 11 and the lamp 12 as described above are provided in plurality in accordance with the illuminance of the backlight required in the liquid crystal panel of the liquid crystal display device. However, FIG. 1 illustrates one inverter 11 and a lamp 12 as a basic structure.

In general, in the liquid crystal display, an external control mode in which a pulse width modulation signal supplied from the outside is applied to an inverter integrated device as it is, and a triangular wave generated internally by receiving a DC voltage from the outside are used. There is an internal control mode in which the pulse width modulated signal is generated and applied to the inverter integrated device as compared with the above.

Therefore, in the conventional liquid crystal display device, each inverter is provided corresponding to the two control modes, and one inverter is selected and used according to the demand of the buyer.

As described above, in the backlight driving apparatus of the conventional liquid crystal display device, each inverter is provided corresponding to both the external control mode and the internal control mode for the pulse width modulated signal, and one of the inverters is selected according to the needs of the buyer. As a result, since the inverter is used repeatedly, the cost is increased.

Accordingly, an object of the present invention is to drive a switching element using the pulse width modulated signal when a pulse width modulated signal is directly applied to the dimming terminal from the outside in one inverter, and when a DC voltage is applied to the dimming terminal. Compared to the internal triangular wave to generate a pulse width modulated signal according to the drive to drive the switching element, to implement the internal synchronous inverter and the external synchronous inverter integrally.

In order to achieve the above object, the present invention provides a pulse width modulation signal for checking whether a pulse width modulation signal or a DC voltage is supplied to an inverter from the outside and controlling them to be selectively input to an external pulse width modulation part or an internal pulse width modulation part. A selection controller; An internal pulse width modulator selected by the pulse width modulated signal selection controller to generate a pulse width modulated signal from a DC voltage supplied from the outside and an internally generated triangular wave and supply the pulse width modulated signal to an inverter integrated device; And an external pulse width modulator which is selected by the pulse width modulated signal selection control unit and supplies a pulse width modulated signal supplied from the outside to the inverter integrated device.

Another object of the present invention to achieve the above object, the process of checking whether the pulse width modulation signal used in the inverter is supplied from the outside; If it is determined that the pulse width modulation signal is supplied from the outside, driving the switching element of the inverter integrated device with the pulse width modulation signal; If it is determined that the pulse width modulated signal is not supplied from the outside, generating a pulse width modulated signal by using a DC voltage supplied from the outside and an internally generated triangular wave to drive the switching element of the inverter integrated device. Characterized in that made.

The present invention checks whether the pulse width modulation signal is supplied from the outside or the DC voltage is supplied. When the pulse width modulation signal is supplied, the switching element of the inverter integrated device is driven using the pulse width modulation signal. When supplied, the pulse width modulated signal is generated using the DC voltage and the triangular wave generated internally, and the switching element of the inverter integrated device is driven using the DC voltage and the internally generated triangular wave. It is not necessary to have a plurality of inverters corresponding to all, so that the cost can be reduced.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a block diagram showing an embodiment of a backlight driving apparatus of a liquid crystal display according to the present invention. As shown therein, an external control mode in which a pulse width modulation signal required by an inverter 21 is supplied from the outside is shown. A pulse width modulation signal selection control unit 21A which checks whether the internal control mode is internally recognized or internally generated and supplied, and selects one of the internal and external pulse width modulation units 21B and 21C according to the checking result; When selected by the pulse width modulation signal selection control unit 21A, a pulse width modulation signal PWM is generated by using a DC voltage supplied from the outside and a triangular wave generated therein, and transmitted to the inverter integrated device 21D. An internal pulse width modulator 21B; An external pulse width modulator (21C) for transmitting a pulse width modulated signal (PWM) supplied from the outside to the inverter integrated device (21D) when selected by the pulse width modulated signal selection control unit (21A); Inverter integrated device 21D for converting a DC voltage into an AC voltage by driving a switching device using the pulse width modulation signal PWM supplied from the internal pulse width modulator 21B or the external pulse width modulator 21C. Wow; The transformer 22 was configured to boost the AC voltage supplied from the inverter integrated element 21D and supply it to a backlight lamp (not shown).

The pulse width modulated signal selection control unit 21A uses a voltage of a specific pin of a connector for a flexible flat cable (FFC) cable (FFC) used to synchronize the synchronization of the vertical synchronization signal between the inverter and the timing controller. A transistor Q1 that is turned on or off to disable or enable the internal pulse width modulator 21B; A transistor (Q2) which is turned on or off according to the voltage of the specific pin to block or supply a power terminal voltage (5.1V_DIM) of a predetermined level to the base side of the transistor (Q3); The transistor Q3 mutes the output signal of the external pulse width modulator 21C when turned on by the power terminal voltage 5.1V_DIM of the predetermined level.

The internal pulse width modulator 21B generates a pulse width modulated signal PWM by using a DC voltage supplied through the dimming terminal DIM and a triangle wave generated therein, or generates a pulse width modulated signal PWM. The DC voltage may be directly transmitted to the inverter integrated device 21D without being generated.

When the DC voltage is supplied from the internal pulse width modulator 21B, the inverter integrated device 21D is configured to generate a pulse width modulated signal PWM using the DC voltage and a triangular wave generated therein. Can be.

FIG. 4 is a control flowchart illustrating an embodiment of a backlight driving method of a liquid crystal display according to the present invention. As shown therein, a process of checking whether an FFC cable is connected between an inverter and a timing controller (S1.S2); If it is determined that the FFC cable is not connected, driving the switching element of the inverter integrated element with a pulse width modulation signal supplied from the outside (S3, S6); When it is determined that the FFC cable is connected, a pulse width modulated signal is generated by using a DC voltage supplied from the outside and a triangular wave generated therein to drive the switching element of the inverter integrated device (S4-S6).

Referring to Figure 3 attached to the operation of the present invention configured as described above in detail as follows.

In general, a mode for adjusting the brightness of a backlight in a liquid crystal display device includes an external control mode in which a pulse width modulation signal supplied from an external device is directly applied to an inverter integrated device, and a triangular wave generated internally by receiving a DC voltage from an external device. Compared with the internal control mode, a pulse width modulated signal is generated and applied to the inverter integrated device. The external control mode and the internal control mode is determined according to the buyer's request.

The pulse width modulation signal selection controller 21A checks whether the current brightness control mode is selected as the external control mode or the internal control mode, and according to the check result, the internal pulse width modulator 21B and the external One of the pulse width modulators 21C is selected.

The pulse width modulation signal selection control unit 21A may determine various methods of determining the brightness adjustment mode of the current backlight. In the embodiment of the present invention, the external adjustment mode is installed at one side of the inverter 21. Considering that the inverter 21 and the timing controller (not shown) are connected through the connector CNT and the cable, the determination is made based on the voltage of the specific pin of the connector CNT.

That is, in the internal control mode, the inverter 21 and the timing controller are connected to each other via the FFC cable to match the synchronization of the vertical synchronization signal Vsync between the timing controller and the inverter 21. At this time, the ground terminal of the cable ( GND) is connected to the first pin P1, which is an option pin of the connector CNT, and causes the pulse width modulation signal selection control unit 21A to currently select the backlight based on the voltage of the first pin P1. To determine the brightness control mode of (S1, S2).

3 shows a pin map of the FFC cable, in which a third pin P3 is used to synchronize the synchronization of the vertical synchronization signal Vsync between the timing controller and the inverter 21 as described above. The first pin P1 is an option pin and is used to determine the brightness control mode of the currently selected backlight as described above.

Therefore, when the brightness control mode of the backlight is adopted as the external control mode, the first pin of the connector (CNT) is disconnected because the cable for connection with the timing controller is disconnected from the connector (CNT) provided on one side of the inverter (21). P1 is in a floating state.

As a result, the power supply terminal voltage 5.1V_DIM is supplied to the bases of the transistors Q1 and Q2 via the resistors R1 and then through the resistors R2 and R3, respectively, so that they are all turned on.

Accordingly, the output voltage of the internal pulse width modulator 21B is muted to the ground terminal through the transistor Q1. Thus, the output signal of the internal pulse width modulator 21B is invalidated.

At this time, since the transistor Q2 is turned on, the power supply terminal voltage 5.1V_DIM is muted through the resistor R4 to the ground terminal through the transistor Q2. As a result, the base voltage of the transistor Q3 becomes low potential, so that the transistor Q3 is turned on. Accordingly, the transistor Q3 has no influence on the external pulse width modulator 21C.

Therefore, the external pulse width modulator 21C receives the pulse width modulated signal PWM supplied from the outside through the dimming terminal DIM, removes or shapes the noise component, and delivers the noise component to the inverter integrated device 21D. (S3)

Thus, the inverter integrated device 21D drives a switching device such as a power transistor by using a pulse width modulated signal PWM input from the external pulse width modulator 21C to convert a DC voltage into an AC voltage. (S6)

The generated AC voltage is converted into a high voltage AC voltage by the transformer 22, and then supplied to the backlight lamp to light the lamp. The backlight is irradiated onto the liquid crystal panel by the lighting of the lamp.

However, when the brightness control mode of the backlight is adopted as the internal control mode, the inverter 21 is connected to the timing controller through the connector (CNT) and the FFC cable, wherein the first of the connector (CNT) Pin P1 is connected to the ground terminal of the FFC cable.

As a result, the power supply terminal voltage 5.1V_DIM is muted to the ground terminal through the first pin P1 of the connector CNT after the resistor R1.

As a result, the base voltages of the transistors Q1 and Q2 become low potential, so that the transistors Q1 and Q2 are both turned off. Accordingly, the power supply terminal voltage 5.1V_DIM is supplied to the base of the transistor Q3 through the resistor R4, and the transistor Q3 is turned on.

Thus, since the output signal of the external pulse width modulator 21C is muted through the transistor Q3, the output signal of the external pulse width modulator 21C is invalidated.

However, since the transistor Q1 is turned off as described above, the transistor Q1 does not affect the internal pulse width modulator 21B.

Accordingly, the internal pulse width modulator 21B receives a DC voltage supplied from the outside through the dimming terminal DIM, and receives the pulse width modulated signal PWM using the DC voltage and the triangular wave generated therein. It generates and transfers to the inverter integrated device 21D. (S4, S5)

In this case, the inverter integrated device 21D drives a switching device such as a power transistor by using a pulse width modulated signal PWM input from the internal pulse width modulator 21B to convert a DC voltage into an AC voltage. (S6)

The generated AC voltage is converted into a high voltage AC voltage by the transformer 22, and then supplied to the backlight lamp to light the lamp. The backlight is irradiated onto the liquid crystal panel by the lighting of the lamp.

For reference, the output terminal side of the external pulse width modulator 21C is connected to the output terminal side of the internal pulse width modulator 21B through a diode D1, and the connection point of the external pulse width modulator 21C is connected. The input terminal DUTY is connected to prevent the output signal of the internal pulse width modulator 21B from affecting the external pulse width modulator 21C.

In the above description, the internal pulse width modulator 21B generates a pulse width modulated signal PWM using the DC voltage and the triangular wave generated therein, and supplies the same to the inverter integrated device 21D. In another embodiment, the internal pulse width modulator 21B may appropriately process the DC voltage supplied from the outside through the dimming terminal DIM and supply the DC voltage to the inverter integrated device 21D.

In this case, the inverter integrated device 21D directly generates the pulse width modulated signal PWM using the DC voltage supplied from the internal pulse width modulator 21B and the triangular wave generated therein.

In this case, the inverter integrated device 21D drives a switching device such as a power transistor by using the pulse width modulated signal PWM generated as described above to convert the DC voltage into an AC voltage. The alternating voltage generated in this way is converted into a high-voltage alternating voltage by the transformer 22, and then supplied to the backlight lamp to light the lamp. The backlight is irradiated onto the liquid crystal panel by the lighting of the lamp.

1 is a block diagram showing a basic configuration of a backlight driving apparatus according to the prior art.

2 is a block diagram of a backlight driving device of a liquid crystal display device according to the present invention;

Figure 3 is a schematic diagram showing the pins of the FFC cable applied to the present invention.

4 is a control flowchart of a backlight driving method of a liquid crystal display according to the present invention;

*** Description of the symbols for the main parts of the drawings ***

21: Inverter 21A: pulse width modulation signal selection control unit

21B: Internal pulse width modulator 21C: External pulse width modulator

21D: Inverter Integrated Device 22: Transformer

Claims (8)

A pulse width modulation signal selection control unit which checks whether a pulse width modulation signal or a DC voltage is supplied to the inverter from the outside and controls them to be selectively transmitted to an external pulse width modulation unit or an internal pulse width modulation unit; An internal pulse width modulator selected by the pulse width modulated signal selection controller and configured to generate a pulse width modulated signal from a DC voltage supplied from the outside and a triangle wave generated internally and supply the pulse width modulated signal to an inverter integrated device;  And an external pulse width modulator selected by the pulse width modulated signal selection controller to transmit the pulse width modulated signal supplied from the outside to the inverter integrated device. The pulse width modulation signal selection control unit according to claim 1, wherein the pulse width modulation signal selection control unit detects a connection state of the FFC cable used to synchronize the synchronization of the vertical synchronization signal between the inverter and the timing controller and based on the detection result, The backlight driving device of the liquid crystal display device, characterized in that configured to check whether the DC voltage is supplied. The pulse width modulation signal selection control unit of claim 1, wherein A transistor Q1 that is turned on or off by a voltage of a specific pin of the CFC connector FNT, which is used for synchronizing the vertical synchronization signal between the inverter and the timing controller, to disable or enable the internal pulse width modulator. )Wow; A transistor (Q2) which is turned on or off in accordance with the voltage of the specific pin to block or supply a power terminal voltage (5.1V_DIM) to the base side of the transistor (Q3); And a transistor (Q3) for muting the output signal of the external pulse width modulator (21C) when turned on by the power terminal voltage (5.1V_DIM). 4. The backlight driving apparatus of claim 3, wherein the specific pin is a pin connected to the ground pin of the FFC cable. The backlight driving apparatus of claim 1, wherein the internal pulse width modulation unit is configured to transmit a DC voltage supplied from the outside to the inverter integrated device without generating a pulse width modulation signal (PWM). The inverter integrated device of claim 1, wherein the inverter integrated device is configured to generate a pulse width modulated signal PWM by using the DC voltage and an internally generated triangular wave when a DC voltage is supplied from the internal pulse width modulator. Backlight drive device of the liquid crystal display device. A first step of checking whether a pulse width modulation signal or a DC voltage is supplied to the inverter from the outside; A second step of driving the switching element of the inverter integrated element with the pulse width modulated signal if it is determined that the pulse width modulated signal is supplied; And if it is determined that the DC voltage is supplied, generating a pulse width modulated signal using the DC voltage and the triangular wave generated inside the inverter to drive the switching element of the inverter integrated device. Backlight driving method of the liquid crystal display device. 8. The method of claim 7, wherein the first process detects the connection state of the FFC cable used to synchronize the synchronization of the vertical synchronization signal between the inverter and the timing controller, and determines whether the pulse width modulated signal is supplied based on the detection result. And determining whether the supply is performed.
KR1020070099476A 2007-10-02 2007-10-02 Apparatus and method for driving backlight of liquid crystal display device KR20090034212A (en)

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