KR20110080044A - Method for driving the backlight unit and display apparatus thereof - Google Patents

Method for driving the backlight unit and display apparatus thereof Download PDF

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Publication number
KR20110080044A
KR20110080044A KR1020100000196A KR20100000196A KR20110080044A KR 20110080044 A KR20110080044 A KR 20110080044A KR 1020100000196 A KR1020100000196 A KR 1020100000196A KR 20100000196 A KR20100000196 A KR 20100000196A KR 20110080044 A KR20110080044 A KR 20110080044A
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KR
South Korea
Prior art keywords
driving signal
driving
signal
backlight unit
change
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KR1020100000196A
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Korean (ko)
Inventor
이은식
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엘지전자 주식회사
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Priority to KR1020100000196A priority Critical patent/KR20110080044A/en
Publication of KR20110080044A publication Critical patent/KR20110080044A/en

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0038—Circuits for comparing several input signals and for indicating the result of this comparison, e.g. equal, different, greater, smaller (comparing pulses or pulse trains according to amplitude)
    • 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
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G02F1/133602—Direct backlight
    • G02F1/133603—Direct backlight with LEDs
    • 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
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1335—Structural association of cells with optical devices, e.g. polarisers or reflectors
    • G02F1/1336—Illuminating devices
    • G02F1/133602—Direct backlight
    • G02F1/133608—Direct backlight including particular frames or supporting means
    • 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
    • G09G3/3413—Details of control of colour illumination sources
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B14/00—Transmission systems not characterised by the medium used for transmission
    • H04B14/02—Transmission systems not characterised by the medium used for transmission characterised by the use of pulse modulation
    • H04B14/026—Transmission systems not characterised by the medium used for transmission characterised by the use of pulse modulation using pulse time characteristics modulation, e.g. width, position, interval
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0247—Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2340/00—Aspects of display data processing
    • G09G2340/16—Determination of a pixel data signal depending on the signal applied in the previous frame

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  • Physics & Mathematics (AREA)
  • Nonlinear Science (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Mathematical Physics (AREA)
  • Chemical & Material Sciences (AREA)
  • Optics & Photonics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Theoretical Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Planar Illumination Modules (AREA)

Abstract

PURPOSE: A method for driving a backlight unit and a display device thereof are provided to prevent a flicker phenomenon which occurs when a mode or resolution is converted. CONSTITUTION: An image signal is inputted to a display device(S101). If the image signal is inputted, the display device compares an image signal inputted at current time with an image signal inputted at previous time(S102). The display device determines whether a current mode is converted or the resolution of an input image signal is changed(S103). If the mode is converted or the resolution of the input image signal is changed, a driving signal made of a PWM frequency is generated and supplied(S104).

Description

Method for driving the backlight unit and a display device using the same

The present invention relates to a backlight unit and a display device including the same, and more particularly, to a method of driving the backlight unit.

As the information society develops, the demand for display devices is increasing in various forms, and in recent years, liquid crystal display devices (LCDs), plasma display panels (PDPs), electro luminescent displays (ELDs), and vacuum fluorescents (VFDs) have been developed. Various display devices such as displays have been studied and used.

Among them, the liquid crystal panel of the LCD includes a liquid crystal layer and a TFT substrate and a color filter substrate facing each other with the liquid crystal layer interposed therebetween, and have no self-luminous power to display an image using light provided from the backlight unit. can do.

An object of the present invention is to provide a method of driving a backlight unit capable of improving the image quality of a display image and a display apparatus using the same.

The technical problems to be achieved in the proposed embodiment are not limited to the technical problems mentioned above, and other technical problems not mentioned above are clear to those skilled in the art to which the proposed embodiments belong from the following description. Can be understood.

A driving method of a backlight unit according to an exemplary embodiment of the present invention includes supplying a first driving signal for driving the backlight unit based on a brightness level of an image signal input at the present time; Comparing the video signal input at the present time and the video signal input at a previous time to determine whether a change in the video signal occurs; Supplying a second driving signal that compensates for the supplied first driving signal when a change occurs in the video signal; And driving the backlight unit based on the compensated second driving signal.

In addition, the display device according to an embodiment of the present invention includes a plurality of optical assembly including a light source and a light guide plate for emitting a side incident light from the light source to the upper side; And a light source driver configured to drive light sources included in the plurality of optical assemblies based on the image signal, wherein the light source driver corresponds to a brightness level of the image signal according to a change of state of an input image signal. The light source may be driven using any one of a driving signal and a second driving signal that compensates for the first driving signal.

According to an embodiment of the present invention, in the display device using the LED backlight, there is an effect of preventing the flicker phenomenon that may occur when a change occurs in an input signal such as mode switching or resolution switching. .

1 is an exploded perspective view showing the overall configuration of a display device.
2 is a cross-sectional view showing an embodiment of a display module configuration.
3 is a plan view showing a first embodiment of the configuration of the backlight unit.
4 is a cross-sectional view of the backlight unit according to the II ′ diagram of FIG. 1.
5 is a perspective view of FIG. 4.
6 to 8 are perspective views showing each part of the optical assembly according to the embodiment.
9 is a block diagram illustrating a configuration of a display apparatus according to an exemplary embodiment of the present invention.
10 is a flowchart illustrating a step-by-step method of driving a backlight unit according to an exemplary embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings as follows. Hereinafter, the embodiments may be modified in various forms, and the technical scope of the embodiments is not limited to the embodiments described below. The embodiments are provided to more clearly explain to those skilled in the art. Accordingly, the shape and size of elements in the drawings may be exaggerated for clarity.

1 is an exploded perspective view showing the overall configuration of a display device.

Referring to FIG. 1, the display apparatus 1 includes a display module 200, a front cover 300 and a back cover 400 surrounding the display module 200, and a display cover 200 with the front cover 300. And / or a fixing member 500 for fixing to the back cover 400.

One side of the fixing member 500 is fixed to the front cover 300 by a fastening member such as a screw, etc., and the other side supports the display module 200 with respect to the front cover 300 to display the front cover 300. Module 200 may be fixed.

In this embodiment, the fixing member 500 is described as being formed in a plate shape extending in one direction as an example, but the separate fixing member 500 is not provided, and the display module 200 is provided by the fastening member. It is also possible that the configuration fixed to the front cover 300 or the back cover 400 is possible.

2 is a cross-sectional view of an embodiment of a display module configuration, and illustrates a cross-sectional configuration of the display module 200 cut along the line A-A of FIG. 1.

Referring to FIG. 2, the display module 200 may form a display panel 210 on which an image is displayed, a backlight unit 100 that provides light to the display panel 210, and a lower exterior of the display module 200. A bottom cover 110, a panel supporter 240 supporting the display panel 210 from below, and a top cover 230 supporting the display panel 210 from above and forming an edge of the display module 200. .

The bottom cover 110 may be formed in a box shape having an upper surface open to accommodate the backlight unit 100.

One side of the bottom cover 110 may be fixed to one side of the top cover 230. For example, a fastening member such as a screw penetrates the side surface of the display module 200, that is, the side where the bottom cover 110 and the top cover 230 overlap each other, and thus the bottom cover 110 and the top cover 230 may be separated. Can be fixed

Although not shown in detail, the display panel 210 includes, for example, a lower substrate 211 and an upper substrate 222 and a liquid crystal layer interposed between the two substrates so as to maintain a uniform cell gap facing each other. can do. A plurality of gate lines and a plurality of data lines intersecting the plurality of gate lines may be formed on the lower substrate 211, and a thin film transistor (TFT) may be formed at an intersection of the gate lines and the data lines. have.

Meanwhile, color filters may be formed on the upper substrate 212, but the structure of the display panel 210 is not limited thereto, and the display panel 210 may have various structures. For example, the lower substrate 211 may include not only a thin film transistor but also a color filter. In addition, the display panel 210 may be formed in various shapes according to a method of driving the liquid crystal layer.

In addition, a gate driving printed circuit board (PCB) for supplying a scan signal to a gate line and a data driving printed circuit board (PCB) for supplying a data signal to a data line are provided at an edge of the display panel 210. ) May be provided. A polarizing film (not shown) may be disposed on at least one of the top and bottom of the display panel 210.

An optical sheet 220 may be disposed between the display panel 210 and the backlight unit 100, and the optical sheet 220 may be removed, but is not limited thereto. The optical sheet 220 may include a diffusion sheet (not shown) or a prism sheet (not shown).

The diffusion sheet evenly spreads the light emitted from the light guide plate, and the diffused light may be focused onto the display panel by the prism sheet. Here, the prism sheet may be selectively configured using a horizontal or / and vertical prism sheet, one or more roughness reinforcing films, and the like. Type or number of optical sheets 220 may be added or deleted within the technical scope of the embodiment, but is not limited thereto.

Meanwhile, the backlight unit 100 may include a plurality of optical assemblies 10 forming a plurality of divided driving regions. In addition, the display panel 210 has a plurality of divided regions corresponding to the respective optical assemblies 10, and the optical assemblies 10 of the display panel 210 are configured according to gray peak values or color coordinate signals of the divided regions. You can adjust the brightness.

The shape or structure of the display panel 210, the backlight unit 100, or the optical assembly 10 included in the backlight unit 100 illustrated in FIG. 2 is an embodiment according to the present invention, and the present invention is not limited thereto. .

3 is a plan view illustrating a first embodiment of the configuration of the backlight unit 100 and briefly illustrates a configuration of the backlight unit 100 viewed from the front.

Referring to FIG. 3, a plurality of optical assemblies 10 included in the backlight unit 100 may be arranged in a matrix form with N and M (N, M being one or more natural numbers) in the x and y axis directions, respectively. Can be.

According to an embodiment of the present disclosure, the optical assemblies 10 may be disposed to overlap a predetermined area with each other. That is, the optical assembly 10 may define the first area A and the second area B on a plane, and the first area A may include the light source 13, the first part 15b, and the side cover. 4 (see FIG. 4), and the second region B may emit light received from the first region to the front side. The first region A may be disposed under the second region B of the optical assembly 10 disposed nearby.

The plurality of optical assemblies 10 may be arranged such that the first regions A overlap each other and are not observed in a plane. However, the first regions A of the optical assemblies 10 disposed at one edge of the backlight unit 100 may be exposed on a plane without overlapping. The second regions B may be provided in close proximity to the front / rear boundary and the left / right boundary.

Each optical assembly 10 is driven in an edge type backlight method, and each optical assembly 10 again acts as a light source to form a backlight unit by arranging a plurality of optical assemblies 10 in a direct type backlight mode. can do. Therefore, the problem that the light emitting diodes are observed as a hot spot on the screen can be solved, and the thickness of the light guide plate can be reduced and the number of optical films can be reduced, thereby making the backlight unit slim.

For example, in the backlight unit 100 of FIG. 1, nine optical assemblies M1 to M9 may be arranged in a 3 × 3 arrangement.

Each optical assembly 10 may be manufactured as an independent assembly, and may be disposed in close proximity to form a modular backlight unit. Such a modular backlight unit may provide light to the display panel as a backlight means.

The backlight unit 100 according to the embodiment may be driven in a whole driving method or a partial driving method such as local dimming or impulsive. The driving method of the light emitting diode 11 may be variously changed according to a circuit design, but is not limited thereto. As a result, the color contrast ratio is increased and the image of the bright and dark portions on the screen can be clearly expressed, thereby improving the image quality.

That is, the backlight unit 100 is operated by being divided into a plurality of divided driving regions, and the luminance of the divided driving region is related to the luminance of the image signal so that the black portion of the image decreases the brightness and the bright portion increases the brightness. By doing so, the contrast ratio and the sharpness can be improved.

When the backlight unit 100 is driven by a local dimming method, the display panel has a plurality of divided regions corresponding to the optical assemblies, and according to the optical assembly according to the peak value or the color coordinate signal of the gray level of the divided regions. You can adjust the brightness.

For example, only the optical assembly M5 can be driven independently and diverged.

The backlight unit 100 according to the embodiment reduces the power consumption by applying a partial driving method, thereby reducing the cost.

In addition, the backlight unit 100 according to the embodiment may simplify the process of manufacturing the backlight unit 100 by assembling the optical assemblies 10 and may improve productivity by minimizing a loss that may occur during the assembly process. have. In addition, it is possible to reduce the occurrence of defects due to the light guide plate scratch, etc. that may occur in the assembly process of the backlight unit 100, and to improve the optical mura, thereby improving process reliability and improving quality.

The backlight unit 100 according to the embodiment has an effect that can be applied to backlight units of various sizes by standardizing the optical assembly 10 to mass production.

When a failure occurs in any one of the optical assemblies 10 of the backlight unit 100 according to the embodiment, it is not necessary to replace the entire backlight unit 100, so only a defective optical assembly needs to be replaced. The cost of replacing parts is reduced.

The optical assembly 10 and the backlight unit 100 having the same according to the embodiment have a strong and durable effect against impact or environmental changes from the outside.

Since the optical assemblies 10 of the backlight unit 100 according to the exemplary embodiment are arranged with a part of the adjacent optical assemblies 10 overlapping each other, it is possible to improve the generation of bright or dark lines at the boundary of the optical assemblies 10 and to ensure uniformity of light. Has the possible effect.

The backlight unit 100 according to the embodiment may be easily applied to a large display panel. In addition, the embodiment has an advantageous effect in slimming the backlight unit and the display module.

In FIG. 3, the light source and the light guide plate constitute one optical assembly 10 and the plurality of optical assemblies 10 constitute the backlight unit 100. It is not limited.

That is, the present invention does not include the light guide plate but may be applied to a method of providing light to the display panel 210 using a plurality of light sources disposed under the display panel 210, in which case the backlight unit 100 The plurality of light sources included in may be divided into a plurality of regions as shown in FIG. 3, for example, M1 to M9.

4 is a cross-sectional view of the backlight unit of FIG. 1 taken along line II ′ of FIG. 1, and FIG. 5 is a perspective view of FIG. 4. 6 to 8 are perspective views illustrating respective parts of the optical assembly according to the embodiment.

4 to 6, the optical assembly 10 according to the embodiment includes a light source 13, a light guide plate 15, and a reflective member 17, and a side cover for fixing the light source 13 and the light guide plate 15. And 20. The side cover 20 provides a fixed position with respect to the bottom cover 110, and includes a first side cover 21 and a second side cover 22.

The light guide plate 15 includes a first part 15b and a second part 15a. In addition, the second part 15a may be formed of four side surfaces, a top surface on which the surface light source is generated, and a bottom surface facing the top surface.

The first part 15b may be formed to protrude in a horizontal direction along a lower side of one of the side surfaces of the second part 15a. Here, the first part 15b may be referred to as a light incident part through which light is incident from the light source 13, and the second part 15a emits light upward to substantially provide light to the display panel 210. It may be referred to as a light emitting unit.

A scattering pattern (not shown) may be formed on the top or bottom surface of the light guide plate 15. The scattering pattern has a predetermined pattern and diffuses the incident light to improve light uniformity on the entire surface of the light guide plate 15.

As shown in FIG. 4, the lower part of the light guide plate 15 may be formed to be inclined at a predetermined angle from one side adjacent to the first part 15b to the other end opposite to the first part 15b. The thickness of the two parts 15a may become thinner and thinner.

The lower surface of the light guide plate 15 may be provided with a reflective member 17. The reflective member 17 allows the light incident to the side through the first part 15b to be guided inside the light guide plate 15 to be reflected by the reflective member 17 and then emitted to the upper surface. In addition, the reflective member 17 may serve to block interference by light generated from another optical assembly 10 disposed in an overlapping manner.

The first part 15b may have a structure protruding along the lower side of the light guide plate 15, and may include a protrusion 30 protruding from the upper surface to a predetermined height a.

The protrusions 30 may be formed in at least two locations in the x-axis direction on the upper surface of the first part 15b. The protrusion 30 may have various shapes, for example, a shape similar to a cuboid. The protrusion 30 can be prevented from shaking the light guide plate 15 along the x-axis and the y-axis by engaging the first side cover 21.

On the other hand, some of the corners (30a) of the corners of the projection 30 is formed to be round to prevent the crack (crack) generated on the projection by the impact applied to the projection 30 by the movement of the light guide plate (15).

The projection 30 may have a height a of 0.3 to 0.6 mm from the top surface of the first part 15b, the width b on the x axis is 2 to 5 mm, and the width c on the y axis is It may be 1-3mm.

In addition, the protrusion 30 may be disposed between adjacent light emitting diodes 11 and may be formed to be close to the light incident surface 16 on the upper surface of the first part 15b. Therefore, it is possible to prevent the light generated from the light emitting diodes 11 from generating optical interference due to the projection 30 integrally formed with the light guide plate 15.

The positional relationship between the light emitting diodes 11, the protrusions 30 formed on the upper surface of the first part 15b of the light guide plate 15, and the size of the protrusions 30 are not limited thereto. It can have a variety of positional relationships.

The light guide plate 15 may be made of a transparent material, and may include, for example, one of an acrylic resin series such as polymethyl metaacrylate (PMMA), polyethylene terephthlate (PET), polycarbonate (PC), and polyethylene naphthalate (PEN) resin. have. The light guide plate 15 may be formed by an extrusion molding method.

4 and 7, the light source 13 may include at least one light emitting diode 11 and a module substrate 12 on which the light emitting diode 11 is mounted.

The light emitting diodes 11 may be arranged on the module substrate 12 in the x-axis direction and disposed to be adjacent to the light incident surface 16 of the first part 15b.

The module substrate 12 is made of a metal core PCB, FR-4 PCB, a general PCB, a flexible substrate, etc., can be variously changed within the technical scope of the embodiment.

A thermal pad (not shown) may be disposed under the module substrate 12. The heat dissipation member may be formed between the module substrate 12 and the second side cover 22.

The light emitting diode 11 may be a side light emitting type, and the light emitting diode 11 may be a colored LED or a white LED emitting at least one of colors such as red, blue, and green. In addition, the colored LED may include at least one of a red LED, a blue LED, and a green LED, and the arrangement and emission light of the light emitting diode 11 may be changed within the technical scope of the embodiment.

Light generated by the light emitting diodes 11 is incident sideways to the first part 15b. Light incident from the light emitting diodes 11 may be mixed in the light guide plate 15 including the first part 15b.

Light incident from the light emitting diodes 11 is guided in the first part 15b and is incident to the second part 15a. Light incident on the second part 15a is reflected by the reflecting member 17 on the lower surface and emitted to the upper surface. In this case, since light is scattered and diffused by the scattering pattern formed on the lower surface of the light guide plate 15, light uniformity may be improved.

The light emitting diodes 11 may be disposed on the module substrate 12 at predetermined intervals. The light emitting diode 11 may be disposed in an oblique direction with respect to the protrusion 30 in order to minimize the optical effect of the protrusion 30 formed on the light guide plate 15. Thus, the spacing of the light emitting diodes 11 around the protrusion 30 may be wider than the spacing of other light emitting diodes 11.

The light emitting diodes 11 may be provided to secure a space for coupling the first side cover 21 and the second side cover 22 and to minimize an optical effect that may be generated by the light guide plate 15 being pressed by the coupling force. The spacing of some of the light emitting diodes 11 may be wider than the spacing of other light emitting diodes 11.

For example, if the first spacing d of the adjacent light emitting diodes 11 is about 10 mm, the second spacing e of the light emitting diodes 11 near the position where a space for coupling is provided may be about 13 mm. .

Light generated by the light emitting diodes 11 may be mixed in the light guide plate 15 including the first part 15b and uniformly provided to the second part 15a.

4 and 8, the side cover 20 is formed to surround the light source 13 and a part of the light guide plate 15. For example, the side cover 20 may include a first side cover 21 disposed above the light source 13 and the first part 15b and a second side cover disposed below the first part 15b. 22). Meanwhile, the side cover 20 may be made of plastic or metal material.

The first side cover 21 is formed to face the upper surface of the first part 15b. The first side cover 21 may be bent in a downward direction (z-axis line) to face the light incident surface 16 on the upper surface of the first part 15b.

The second side cover 22 is formed to face the lower surface of the first part 15b. The second side cover 22 may be bent in an upward direction (z-axis line) to face the light incident surface 16 on the lower surface of the first part 15b. A part 22a of the second side cover 22 may be formed to be inclined along the lower surface of the light guide plate 15, that is, the inclined surface, and the light source 13 may be accommodated in the second side cover 22.

The first side cover 21 and the second side cover 22 are fastened to each other by the first fixing member 51 so that the light source 13 and the light guide plate 15 are not shaken by an external impact, particularly in the z-axis direction. Make sure that shaking is prevented.

The second side cover 22 may support the inclined surface of the light guide plate 15 to maintain the alignment of the light guide plate 15 and the light source 13 firmly and protect from external impact.

In the first side cover 21, a first hole 41 may be formed at a position corresponding to the protrusion 30 of the first part 15b, and the first hole 41 may be caught by the protrusion 30. It may be formed larger than the projection (30). Meanwhile, a circumference of the first hole 41 may be spaced apart from a predetermined edge of the fitted protrusion 30 by the predetermined space, and the space is expanded by the light guide plate 15 due to a change in external environment, for example, a sudden temperature rise. It may be a margin for preventing deformation of the light guide plate 15. In this case, another portion of the protrusion 30 may contact the circumference of the first hole 41 to strengthen the fixing force.

At least one second hole 42 may be further formed in the first side cover 21. At least one third hole 43 may be formed in the second side cover 21 at a position corresponding to the second hole 42.

The second and third holes 42 and 43 are disposed in a straight line in the z-axis direction, and the first fixing member 51 is inserted to firmly fix the first side cover 21 and the second side cover 22. can do. In order to secure a fixing force, at least two pairs of second and third holes 42 and 43 may be formed in one optical assembly 10. The second hole 42 and the third hole 43 may be formed at any position of the first side cover 21 and the second side cover 22, respectively.

In the first side cover 21, the second hole 42 may be disposed in a straight line with the first hole 41 in the y-axis direction. In this case, the coupling force between the light guide plate 15 and the first side cover 21 by the protrusion 30 of the first hole 41 and the light guide plate 15, the second and third holes 42 and 43, and the first fixing The first side cover 21 and the second side cover 22 may be more firmly fixed by the coupling force between the first side cover 21 and the second side cover 22 by the member 51. Of course, the positions of the holes and the protrusions are not limited thereto, and any position may be used as long as the position of the holes and the protrusions may provide a coupling force between the light guide plate 15 and the side cover 20.

That is, the second hole and the third hole are formed in the side portion overlapping the first side cover 21 and the second side cover 22, respectively, it will be said that the configuration in which the fixing member is inserted in the y-axis direction is also possible.

Meanwhile, a fourth hole through which the second fixing member 52 (see FIG. 7) for fixing the optical assembly 10 to the bottom cover 110 passes through the first side cover 21 and the second side cover 22. 44 and the fifth hole 45 may be further formed.

The remaining portion of the optical assembly 10 except for the second part 15a of the light guide plate 15 is a first area that substantially does not provide light to the display panel, and includes the first hole 41 and the second hole 42. And the width of the first region may be further reduced by the arrangement relationship of the third holes 43.

For example, the case where the second hole 42 and the third hole 43 are disposed between the light emitting diodes 11 may reduce the width of the first area than the case where the second hole 42 and the third hole 43 are disposed behind the light emitting diodes 11. have.

Here, the shape of the first hole 41, the second hole 42, and the third hole 43 formed in the side cover 20 of the optical assembly 10 may be various, and is limited to the illustrated form. It is not.

The first fixing member 51 may be a screw or a fixing pin, but is not limited thereto. When the first fixing member 51 is a screw, peaks and valleys may be formed on the inner surfaces of the second and third holes 42 and 43 along the screw line. As a result, the first fixing member 51 is inserted into the second hole 42 and the third hole 43 and rotated to clamp and fix the light guide plate 15 and the light source 13 sandwiched therebetween.

In order to secure the pitch of the peaks formed on the inner surfaces of the second hole 42 and the third hole 43, the first and second side covers 21 and 22 may include the second hole 42 and the third hole 43. The thickness of the periphery may be thicker than other parts, or a separate member may be used.

The backlight unit 100 manufactured as described above may be accommodated in a box-shaped bottom cover having an upper surface opened.

9 is a block diagram illustrating a configuration of a display apparatus according to an exemplary embodiment of the present invention.

Referring to FIG. 9, a display apparatus according to an exemplary embodiment of the present invention includes a display panel 210, a backlight unit 100, a panel driver 250, and a memory unit 270, and the backlight unit 100 The light source driver 260 may be included.

The display panel 210 may be provided in a rectangular shape corresponding to the backlight unit 100 illustrated in FIG. 3, and the image signal may be scanned frame by frame in an extension direction of the short side. The display panel 210 may display an image at 60, 120, or 180 frames per second, and as the number of frames per second increases, the scan period T of the frame is shortened.

The panel driver 250 receives various control signals and image signals from the outside, generates a driving signal for driving the display panel 210, and supplies the driving signal to the display panel 210. For example, the panel driver 250 may include a gate driver (not shown) connected to the gate line of the display panel 210, a data driver (not shown), a timing controller (not shown) controlling them, and the like. have.

The panel driver 250 may output image information corresponding to the image signal to the light source driver 260 so that the luminance of the light sources included in the backlight unit 100 is controlled in response to the input image signal. In addition, the panel driver 250 may provide the light source driver 260 with information about a scan period in which a frame is displayed on the display panel 210.

Here, the image information is a data signal that divides the input image signal according to the optical assembly included in the backlight unit 100 and indicates a brightness level of the corresponding region for each of the divided regions.

The light source driver 260 drives light sources included in the backlight unit 100 according to the input scan period T so that light is emitted from the light sources in synchronization with the display of the image on the display panel 210. Can be controlled. Here, the scan period may correspond to the Vsync frequency of the input image signal.

As illustrated in FIG. 3, the backlight unit 100 may include a plurality of optical assemblies 10 that are separately driven by including light sources, and the plurality of optical assemblies 10 form a plurality of lines. It can be arranged in the form of a matrix.

In addition, the light source included in the optical assembly 10 may include a plurality of point light sources, for example, light emitting diodes (LEDs), and a plurality of point light sources included in one optical assembly 10. They can be turned on or off at the same time. Meanwhile, according to another exemplary embodiment of the present disclosure, the plurality of point light sources included in one optical assembly 10 may be divided into a plurality of blocks, and may be driven by being turned on or off at the same time for each of the divided blocks. have.

In this case, the light source driver 260 outputs a driving signal for controlling the brightness of the light sources provided in each divided area based on the transmitted image information. In this case, the driving signal is a pulse width modulation (PWM) frequency, and PWM frequencies having different dutys may be provided to the light sources based on the image information. In addition, the PWM frequency is driven in synchronization with the synchronization signal of the video signal.

The light source driver 260 checks whether the received image signal is changed before providing the driving signal to the light sources. That is, it is determined whether the image signal received at the previous point in time and the image signal received at the present point in time are the same image signal, and the light source is based on a first driving signal corresponding to the image information according to a comparison result of the image signals. Determine whether to drive them.

That is, the light source driver 260 determines whether a mode change event occurs and whether a change occurs in the image signal received at the previous time point and the image signal received at the present time point. In addition, the light source driver 260 determines whether the resolution of the video signal received at the previous time is different from the resolution of the video signal received at the current time.

The light source driver 260 drives the light sources based on the first driving signal if no change occurs in the video signal.

However, if a change occurs in the video signal, the light source driver 260 drives the light sources based on a second drive signal that compensates for the first drive signal.

Hereinafter, the difference between the first driving signal and the second driving signal will be described.

The first driving signal is a PWM frequency generated based on the image information. Here, the PWM frequency of the first driving signal has a specific duty according to the brightness level of the video signal.

The second driving signal is set as a default, and the PWM frequency of the second driving signal has a duty having only an on period.

That is, when the input image signal changes, the period of the synchronization signal also changes, and when the synchronization signal changes suddenly, the PWM frequency does not normally respond to the sudden change of the synchronization signal, causing flicker on the screen. Done. In other words, there is a transient period in which the duty of the Vsync frequency and the PWM frequency is shaken when the mode is switched or the resolution is changed, and the flicker phenomenon is caused by a combination of the frequency and the PWM duty shake of the Vsync.

Therefore, when the input image signal is changed as described above, the light source driver 260 uses the second driving signal having a PWM frequency having only on duty instead of the first driving signal generated based on the image information. Drive the light sources.

That is, when the light sources are driven by the second driving signal, since the duty of the PWM frequency is always high regardless of the change of Vsync, the flicker phenomenon caused by the sudden change of Vsync can be prevented.

According to an exemplary embodiment of the present invention, a flicker phenomenon that may occur when a change in an input signal such as mode switching or resolution switching occurs in a display device using an LED backlight may be prevented in advance.

10 is a flowchart illustrating a step-by-step method of driving a backlight unit according to an exemplary embodiment of the present invention.

Referring to FIG. 10, an image signal is input to the display apparatus (step 101). The input video signal may be any one of a terrestrial broadcast signal, a cable broadcast signal, a satellite broadcast signal, and an external input signal provided through an external device.

When the video signal is input, the display apparatus compares the video signal input at the present time and the video signal input at the previous time (step 102). Here, the comparing process is a process of checking whether the two video signals are video signals having the same format or video signals having different formats.

According to the comparison, the display apparatus determines whether a current mode change event has occurred or whether a change has occurred in the resolution of the input image signal (step 103).

If the mode change event occurs or the resolution of the input video signal is changed, a driving signal having a PWM frequency having only on duty is generated, and the generated driving signal is supplied (step 104).

If the resolution of the input video signal is not only changed, but the resolution of the input video signal is not changed, that is, if the video signal input at the previous time and the video signal input at the present time are the same synchronization signal, the current time point. In operation 105, a driving signal having a PWM frequency corresponding to the brightness level of the image signal input to the image signal is generated and the generated driving signal is supplied.

In operation 106, the light sources are driven based on the driving signal supplied according to the input image signal.

The present invention has been described above with reference to preferred embodiments thereof, which are merely examples and are not intended to limit the present invention. Those skilled in the art to which the present invention pertains do not depart from the essential characteristics of the present invention. It will be appreciated that various modifications and applications are not possible that are not illustrated above. For example, each component shown in detail in the embodiment of the present invention may be modified. And differences relating to such modifications and applications will have to be construed as being included in the scope of the invention defined in the appended claims.

100: backlight unit
200: display module 300: front cover
400: back cover 500: fixing member

Claims (14)

Supplying a first driving signal for driving the backlight unit based on a brightness level of an image signal input at this time;
Comparing the video signal input at the present time and the video signal input at a previous time to determine whether a change in the video signal occurs;
Supplying a second driving signal that compensates for the supplied first driving signal when a change occurs in the video signal; And,
And driving the backlight unit based on the compensated second driving signal. The method of claim 1,
The change of the video signal corresponds to a change in resolution. The method of claim 1,
And the change of the image signal corresponds to an input mode change. The method of claim 1,
The driving signal is a pulse width modulation (PWM) frequency,
The first driving signal and the second driving signal has a different duty (duty), characterized in that the driving method of the backlight unit. The method of claim 4, wherein
The on duty width of the second driving signal is greater than the on duty width of the first driving signal. The method of claim 4, wherein
And the second driving signal is a PWM frequency in which only an on period exists. The method of claim 1,
And the second driving signal is supplied only to a change section of the video signal. A plurality of optical assemblies including a light source and a light guide plate for emitting side incident light from the light source;
And a light source driver for driving light sources provided in the plurality of optical assemblies based on the image signal.
The light source driver drives the light sources by using one of a first driving signal corresponding to a brightness level of the image signal and a second driving signal compensating the first driving signal according to a change in the state of an input image signal. Display device. The method of claim 8,
And the state change corresponds to at least one of a resolution change and a mode change. The method of claim 8,
The light source driver drives the light sources based on the second driving signal when a state change occurs in the image signal received at the previous time and the image signal received at the present time. 1. The display apparatus of claim 1, wherein the light sources are driven based on a driving signal. The method of claim 8,
The driving signal is a pulse width modulation (PWM) frequency,
The first driving signal and the second driving signal has a different duty (duty), characterized in that the driving method of the backlight unit. 12. The method of claim 11,
The on duty width of the second driving signal is greater than the on duty width of the first driving signal. 12. The method of claim 11,
And the second driving signal is a PWM frequency in which only an on period exists. The method of claim 10,
And the light source driving unit drives the light sources using the second driving signal only in a section in which a state change of the image signal occurs.
KR1020100000196A 2010-01-04 2010-01-04 Method for driving the backlight unit and display apparatus thereof KR20110080044A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10217420B2 (en) 2015-01-29 2019-02-26 Samsung Display Co., Ltd. Display apparatus and method of controlling luminance thereof

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10217420B2 (en) 2015-01-29 2019-02-26 Samsung Display Co., Ltd. Display apparatus and method of controlling luminance thereof

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