KR20080088065A

KR20080088065A - Light emitting device and display using the light emitting device, the driving method of the light emitting device, and the method of the display

Info

Publication number: KR20080088065A
Application number: KR1020070030427A
Authority: KR
Inventors: 조덕구
Original assignee: 삼성에스디아이 주식회사
Priority date: 2007-03-28
Filing date: 2007-03-28
Publication date: 2008-10-02

Abstract

The present invention provides a display device which is advantageous in increasing the dynamic contrast ratio of the screen, preventing damage due to heat generation and temperature variation, and lowering power consumption. A panel assembly including a plurality of gate lines for transmitting a plurality of gate signals, a plurality of data lines for transmitting a plurality of data signals, and a plurality of pixels defined by a plurality of gate lines and a plurality of data lines, and a plurality of scans A plurality of scan lines for transmitting signals, a plurality of column lines for transmitting a plurality of light emitting data signals, a plurality of backlight unit pixels defined by a plurality of scan lines and a plurality of column lines, and an anode electrode to which an anode voltage is applied And a first current flowing through the anode electrode, and when the first current is maintained for more than a reference current for a first period of time, the voltage applied to the plurality of scan signals is reduced, and the voltage applied to the plurality of scan signals. If the first current remains above the reference current for a first period even after reducing the voltage, the anode voltage is reduced and the power is turned off. It includes a back light unit that program.

Description

LIGHT EMITTING DEVICE AND DISPLAY USING THE LIGHT EMITTING DEVICE, THE DRIVING METHOD OF THE LIGHT EMITTING DEVICE, AND THE METHOD OF THE DISPLAY}

1 is an exploded perspective view of a liquid crystal display according to a first embodiment of the present invention.

FIG. 2 is a partially cutaway perspective view of the liquid crystal panel assembly shown in FIG. 1.

3 is a partially cutaway perspective view of the backlight unit according to the first embodiment of the present invention.

4 is a partial cross-sectional view of the fourth substrate and the electron emission unit illustrated in FIG. 3.

5 is a partial plan view of an electron emission unit of a backlight unit according to a second embodiment of the present invention.

6 is a partially cutaway perspective view of a backlight unit according to a third exemplary embodiment of the present invention.

7 is a block diagram illustrating a display device according to a third exemplary embodiment of the present invention.

8 is a flowchart illustrating a process of determining an abnormal current flowing in a backlight unit using an anode current according to a third embodiment of the present invention.

The present invention relates to a display device, and more particularly, to a display device including a backlight unit that operates in synchronization with a display image.

A liquid crystal display device, which is a type of flat panel display device, is a display device that realizes a predetermined image by varying light transmittance for each pixel by using dielectric anisotropy of a liquid crystal whose twist angle changes according to an applied voltage. Such a liquid crystal display device has advantages such as light weight, thickness, and low power consumption compared to a cathode ray tube, which is a typical image display device.

The liquid crystal display basically includes a liquid crystal panel assembly and a backlight unit positioned behind the liquid crystal panel assembly to provide light to the liquid crystal panel assembly.

When the liquid crystal panel assembly is composed of an active liquid crystal panel assembly, the liquid crystal panel assembly includes a pair of transparent substrates, a liquid crystal layer positioned between the transparent substrates, a polarizing plate disposed on the outer surfaces of the transparent substrates, and either transparent A color filter that provides red, green, and blue colors to the common electrode provided on the inner surface of the substrate, the pixel electrodes and switching elements provided on the inner surface of the other transparent substrate, and the three sub-pixels constituting one pixel. And the like.

The liquid crystal panel assembly receives light emitted from the backlight unit and transmits or blocks the light by the action of the liquid crystal layer to realize a predetermined image.

The backlight unit may be classified according to the type of light source, and one of them is known as a cold cathode fluorescent lamp (CCFL). Since the CCFL is a line light source, the light generated by the CCFL can be evenly dispersed toward the liquid crystal panel assembly through the optical members such as the diffusion sheet, the diffusion plate, and the prism sheet.

However, in the CCFL method, since light generated in the CCFL passes through the optical member, significant light loss occurs. In general, in the CCFL type liquid crystal display, the light passing through the liquid crystal panel assembly is known to correspond to about 3 to 5% of the CCFL generated light. In addition, the CCFL type backlight unit consumes a large portion of the total power consumption of the liquid crystal display due to large power consumption, and it is difficult to apply to a large liquid crystal display device having a size of 30 inches or more because of the large area of the CCFL structure.

As a conventional backlight unit, a light emitting diode (LED) method is known. A plurality of LEDs are usually provided as a point light source, and are combined with optical members such as a reflective sheet, a light guide plate, a diffusion sheet, a diffusion plate, and a prism sheet to constitute a backlight unit. This LED method has the advantages of fast response speed and excellent color reproducibility, but has a disadvantage of high price and large thickness.

As such, the conventional backlight unit has its own problems depending on the type of light source. In addition, since the conventional backlight unit is always turned on at a constant brightness when the liquid crystal display is driven, it is difficult to meet the image quality improvement required for the liquid crystal display.

For example, when the liquid crystal panel assembly displays an arbitrary screen including a bright portion and a dark portion in accordance with an image signal, the liquid crystal panel pixels displaying a portion of the liquid crystal panel pixels and a dark portion displaying the bright portion Providing light of different intensities in the field can produce a screen with excellent dynamic contrast.

In addition, a heat generation problem occurs in the front substrate of the backlight unit including the anode electrode. At this time, the generated heat may cause the temperature variation of the glass (glass) included in the front substrate may cause damage to the glass (glass) in serious cases, and may damage the backlight unit.

Accordingly, the present invention is to solve the above problems, by using the anode current flowing through the anode electrode to detect the abnormal current flowing in the front substrate of the backlight unit to prevent damage to the backlight unit, to drive more stably A light emitting device, a display device using the same, a method of driving a light emitting device, and a method of driving a display device are provided.

According to an aspect of the present invention, a display device includes a plurality of gate lines for transmitting a plurality of gate signals, a plurality of data lines for transmitting a plurality of data signals, and a plurality of gate lines and the plurality of gate lines. A panel assembly including a plurality of pixels defined by a data line, a plurality of scan lines transferring a plurality of scan signals, a plurality of column lines transferring a plurality of light emitting data signals, the plurality of scan lines and the plurality of scan lines A plurality of backlight unit pixels defined by the column lines, and an anode electrode to which an anode voltage is applied, sensing a first current flowing through the anode electrode, wherein the first current is greater than or equal to a reference current for a first period of time; If so, the voltage applied to the plurality of scan signals is decreased, and the voltage applied to the plurality of scan signals is reduced. And a backlight unit to turn off the power supply while reducing the anode voltage if the first current is maintained for more than the reference current for a first period after the voltage is reduced. The first backlight unit pixel of the plurality of backlight unit pixels corresponds to the plurality of pixels of the panel assembly, and emits light at a luminance corresponding to the highest gray level among the plurality of pixels. The backlight unit senses the abnormal current of the backlight unit by sensing the first current in a predetermined period unit. The reference current is a threshold current compared with the first current to determine an abnormal current that may occur in the front substrate of the backlight unit.

According to another aspect of the present invention, a light emitting device includes a plurality of scan lines for transmitting a plurality of scan signals, a plurality of column lines for transmitting a plurality of light emission data signals, the plurality of scan lines, and a plurality of column lines. And a plurality of backlight unit pixels, and an anode electrode to which an anode voltage is applied, and sensing a first current flowing through the anode electrode, and maintaining the first current at a first period longer than a reference current. When the first current is maintained for more than the reference current for a first period after reducing the voltage applied to the scan signal and the voltage applied to the plurality of scan signals, the anode voltage is reduced and the power is turned off. It includes a backlight unit. The backlight unit senses the abnormal current of the backlight unit by sensing the first current by a predetermined period unit. In this case, the first current is an anode current generated in the anode electrode by electrons emitted according to the voltage difference between each of the plurality of scan signals and the plurality of light emitting data signals.

According to still another aspect of the present invention, there is provided a method of driving a display device, the method comprising: a panel assembly displaying an image, and a backlight unit configured to supply a backlight to the panel assembly and include a plurality of scan lines and a plurality of column lines. A method of driving a display device, the method comprising: (a) sensing a first current and comparing it with a reference current; and (b) in step a), if the first current is greater than or equal to the reference current, Determining whether the first current is maintained for more than the reference current for a first period, and (c) in step b), when the first current is maintained for more than the reference current for a first period of time, a voltage applied to the plurality of scan lines (D) sensing the first current and comparing it with the reference current; and (e) in step d), if the first current is greater than or equal to the reference current, Determining whether the first current is maintained for more than a reference current for a first period, and (f) in step e), if the first current is maintained for more than the reference current for a first period of time, reducing the anode voltage and turning off the power supply. Steps. In this case, the panel assembly includes a plurality of pixels, the backlight unit includes a plurality of backlight unit pixels, and a first backlight unit pixel among the plurality of backlight unit pixels is a plurality of pixels of the panel assembly. And emit light at a luminance corresponding to the highest gray level among the plurality of pixels.

A method of driving a light emitting device according to another aspect of the present invention, comprising: (a) sensing a first current and comparing it with a reference current; and (b) in the step a), if the first current is equal to or greater than the reference current Determining whether the first current is maintained for more than the reference current for a first period, and (c) in step b), if the first current is maintained for more than the reference current for a first period of time; Reducing the voltage applied to the scan line, (d) sensing the first current and comparing it with the reference current, and (e) step d), if the first current is greater than or equal to the reference current, Determining whether a first current is maintained above the reference current for a first period, and (f) in step e), if the first current is maintained above the reference current for a first period of time, reducing the anode voltage Power on Ping.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention. Like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is "connected" to another part, this includes not only the "directly connected" but also the "electrically connected" between other elements in between. In addition, when a part is said to "include" a certain component, this means that it may further include other components, except to exclude other components unless otherwise stated.

Referring to the drawings, the liquid crystal display device 100 of the present embodiment has a liquid crystal panel assembly 10 having arbitrary pixels along the row direction and the column direction, and smaller than the liquid crystal panel assembly 10 along the row direction and the column direction. And a backlight unit 40 having a number of pixels and positioned behind the liquid crystal panel assembly 10 to provide light to the liquid crystal panel assembly 10.

Here, the row direction may be defined as one direction of the liquid crystal display 100, for example, a horizontal direction of the screen implemented by the liquid crystal panel assembly 10 (for example, the x-axis direction in the drawing), and the column direction may be defined as the liquid crystal display. Another direction of 100 may be defined as, for example, a vertical direction (for example, y-axis direction in the drawing) of the screen implemented by the liquid crystal panel assembly 10.

The number of pixels of the liquid crystal panel assembly 10 and the number of pixels of the backlight unit 40 in the row direction are referred to as M and M ', respectively, and the number of pixels and the backlight unit of the liquid crystal panel assembly 10 in the column direction ( When the number of pixels 40 is N and N ', respectively, the resolution of the liquid crystal panel assembly 10 may be expressed as M x N, and the resolution of the backlight unit 40 may be expressed as M' x N '.

In the present exemplary embodiment, M and N representing the number of pixels of the liquid crystal panel assembly 10 may be defined as integers of 240 or more, respectively, and M 'and N' representing the number of pixels of the backlight unit 40 are 2 to 99, respectively. Can be defined as any one of the integers. The backlight unit 40 includes a self-luminous display panel having a resolution of M 'x N'.

Thus, one pixel of the backlight unit 40 is positioned corresponding to two or more pixels of the liquid crystal panel assembly 10. In addition, the pixels of the backlight unit 40 are individually controlled on / off and light emission intensity by driving electrodes arranged in a matrix form, for example, scan electrodes and data electrodes positioned in directions perpendicular to each other.

In this embodiment, one pixel of the backlight unit 40 is formed of a field emission array (FEA) type electron emission device.

The FEA type electron emission device includes a scan electrode and a data electrode, an electron emission part and a fluorescent layer electrically connected to any one of the scan electrode and the data electrode. The electron emission part may be made of a material having a low work function or a high aspect ratio, for example, a carbon-based material or a nanometer (nm) size material.

The FEA type electron emitting device forms an electric field around the electron emitting part by using the voltage difference between the scan electrode and the data electrode to emit electrons therefrom, and excites the fluorescent layer with the emitted electrons to display visible light having an intensity corresponding to the electron beam emission amount. Release.

Referring to the drawings, the liquid crystal panel assembly 10 includes a transparent first substrate 12 and a second substrate 14 disposed opposite to each other, and a liquid crystal injected between the first substrate 12 and the second substrate 14. A layer 16, a common electrode 18 located on an inner surface of the first substrate 12, pixel electrodes 20 and switching elements 22 located on an inner surface of the second substrate 14. do. Sealing members (not shown) are positioned at edges of the first substrate 12 and the second substrate 14.

The first substrate 12 is the front substrate of the liquid crystal panel assembly 10, and the second substrate 14 is the rear substrate of the liquid crystal panel assembly 10. On the outer surface of the first substrate 12 and the second substrate 14, a pair of polarizing plates 24, 26 whose polarization axes are perpendicular to each other are positioned. The inner surface of the first substrate 12 on which the common electrode 18 is positioned and the inner surface of the second substrate 14 on which the pixel electrodes 20 and the switching elements 22 are positioned are covered with the alignment layer 28. All.

On the inner surface of the second substrate 14, a plurality of gate lines 30 for transmitting a gate signal (also referred to as a "scan signal") and a plurality of data lines 32 for transmitting a data signal are formed. The gate lines 30 are located next to each other along the row direction, and the data lines 32 are located next to each other along the column direction.

One pixel electrode 20 is positioned for each sub-pixel, and each sub-pixel includes a switching element 22 connected to the gate line 30 and a data line 32, and a liquid crystal connected to the switching element 22. Capacitor Clc (not shown) and sustain capacitor Cst (not shown) are formed. Holding capacitor Cst can be omitted as needed.

The switching element 22 may be formed of a thin film transistor, the control terminal and the input terminal of which are connected to the gate line 30 and the data line 32, respectively, and the output terminal of which is connected to the liquid crystal capacitor Clc.

The color filter 34 is disposed between the first substrate 12 and the common electrode 18. The color filter 34 is composed of red, green, and blue filters corresponding to one sub-pixel, and three sub-pixels in which three filters of red, green, and blue are located constitute one pixel.

When the thin film transistor, which is the switching element 22, is turned on in the liquid crystal panel assembly 10 having the above-described configuration, an electric field is formed between the pixel electrode 20 and the common electrode 18. The twist angle of the liquid crystal molecules positioned in the liquid crystal layer 16 is changed by this electric field to control a light transmission amount for each sub-pixel, thereby implementing a predetermined color image.

A first embodiment of the backlight unit will be described with reference to FIGS. 3 and 4, and a second embodiment of the backlight unit will be described with reference to FIG. 5. In each embodiment, the backlight unit consists of an FEA type electron emission display panel including FEA type electron emission elements.

3 is a partial cutaway perspective view of a backlight unit according to a first exemplary embodiment of the present invention, and FIG. 4 is a partial cross-sectional view of the fourth substrate and the electron emission unit illustrated in FIG. 3.

Referring to the drawings, the backlight unit 40 includes a third substrate 42 and a fourth substrate 44 which are disposed to face each other at a predetermined interval. The sealing member 46 is disposed at the edge of the third substrate 42 and the fourth substrate 44 to bond the two substrates, and the internal space is evacuated with a vacuum of approximately 10-6 Torr, so that the third substrate 42 The fourth substrate 44 and the sealing member 46 constitute a vacuum container.

The third substrate 42 becomes the front substrate of the backlight unit 40 facing the liquid crystal panel assembly, and the fourth substrate 44 becomes the rear substrate of the backlight unit 40. One surface of the fourth substrate 44 facing the third substrate 42 is provided with an electron emission unit 48 for electron emission, and one surface of the third substrate 42 facing the fourth substrate 44 is a light emitting unit. 50 is provided.

First, the electron emission unit 48 will be described. The electron emission unit 48 may include the cathode electrodes 52 formed in a stripe pattern along one direction of the fourth substrate 44 and the insulating layer 54. The gate electrodes 56 are formed in a stripe pattern along a direction orthogonal to the cathode electrode 52, and the electron emission units 58 electrically connected to the cathode electrode 52.

The gate electrodes 56 may be arranged side by side in the row direction of the fourth substrate 44, and may function as scan electrodes by applying a scan driving voltage. The cathode electrodes 52 may be arranged side by side in the column direction of the fourth substrate 44, and may function as a data electrode by receiving a data driving voltage.

Electron emitters 58 are formed in the cathode electrode 52 at each intersection of the cathode electrode 52 and the gate electrode 56. Openings 541 and 561 corresponding to the electron emission portions 58 are formed in the insulating layer 54 and the gate electrodes 56 to expose the electron emission portions 58 on the fourth substrate 44. In this embodiment, the intersection area of the cathode electrode 52 and the gate electrode 56 corresponds to one pixel area of the backlight unit 40.

The electron emission unit 58 is made of materials that emit electrons when an electric field is applied in a vacuum, such as a carbon-based material or a nanometer (nm) size material. The electron emission unit 58 may include, for example, carbon nanotubes, graphite, graphite nanofibers, diamonds, diamond-like carbons, C60, silicon nanowires, or a combination thereof, and may be screen printed or directly grown. , Chemical vapor deposition or sputtering, and the like.

On the other hand, the electron emission portion may be formed of a tip structure having a pointed tip mainly made of molybdenum (Mo) or silicon (Si).

Next, the light emitting unit 50 provided on the third substrate 42 includes a fluorescent layer 60 and an anode electrode 62 positioned on one surface of the fluorescent layer 60. The fluorescent layer 60 may be formed of a white fluorescent layer or a combination of red, green, and blue fluorescent layers. In the figure, the first case is illustrated.

The white fluorescent layer may be formed on the entirety of the third substrate 42 or may be divided and positioned in a predetermined pattern so that one white fluorescent layer is positioned in each pixel area. The red, green, and blue fluorescent layers may be divided and positioned in a predetermined pattern in one pixel area.

The anode electrode 62 may be formed of a metal film such as aluminum (Al) covering the surface of the fluorescent layer 60. The anode electrode 62 is an acceleration electrode for attracting an electron beam, and is applied with a high voltage (a positive DC voltage of approximately several thousand volts) to maintain the fluorescent layer 60 in a high potential state, and among the visible light emitted from the fluorescent layer 60. The visible light emitted toward the fourth substrate 44 is reflected toward the third substrate 42 to increase the brightness of the screen.

In the above-described configuration, the FEA type electron emission device includes a cathode electrode 52, a gate electrode 56, electron emission portions 58, and a corresponding fluorescent layer 60 constituting one pixel.

In the above configuration, when a predetermined driving voltage is applied to the cathode electrodes 52 and the gate electrodes 56, an electric field is formed around the electron emission section 58 in the pixel region in which the voltage difference between the two electrodes is greater than or equal to the threshold. Electrons are emitted. The emitted electrons are attracted by the high voltage applied to the anode electrode 62 and collide with the corresponding fluorescent layer 60 to emit light. The emission intensity of the pixel-specific fluorescent layer 60 corresponds to the electron beam emission amount of the pixel.

5 is a partial plan view of the electron emission unit 48 'of the backlight unit according to the second embodiment of the present invention.

Referring to the drawings, in this embodiment, two or more intersection regions of the cathode electrode 52 'and the gate electrode 56' are combined to form one pixel region A. Referring to FIG. In this case, when two or more cathode electrodes 52 'and two or more gate electrodes 56' are combined to form one pixel region A, the two or more cathode electrodes 52 'are formed. Electrically connected to each other to receive the same driving voltage, two or more gate electrodes 56 'are also electrically connected to each other to receive the same driving voltage.

To this end, the two or more cathode electrodes 52 ′ and the two or more gate electrodes 56 ′ extend to the edge of the fourth substrate to form a connection member such as a flexible printed circuit board (FPCB). Ends (not shown) may be connected to each other.

In the drawing, as an example, nine crossing regions where three cathode electrodes 52 'and three gate electrodes 56' intersect form one pixel region A is illustrated.

In both the back light unit of the first embodiment and the back light unit of the second embodiment, the compression force applied to the vacuum container is supported between the third substrate 42 and the fourth substrate 44 and the distance between the two substrates is maintained. Spacers 64 (see Fig. 4) are arranged to keep the constant. The spacers 64 are preferably located outside the pixel area, not in the center of the pixel area.

In addition, if necessary, the third substrate 42 itself, which is the front substrate, may have a light diffusing function to function as a diffusion plate, and as shown in FIG. 6 according to the third embodiment of the present invention. A diffuser plate 66 having a light diffusing function may be positioned on an outer surface of the third substrate 42 facing the light emitting diode.

As described above, the liquid crystal display 100 of the present exemplary embodiment uses a kind of low resolution display panel having a smaller number of pixels than the liquid crystal panel assembly 10 as the backlight unit 40. The backlight unit 40 is driven through a passive matrix method using scan electrodes and data electrodes, and provides light of different intensities to pixels of the liquid crystal panel assembly 10 corresponding to each pixel. .

The following table tests the display quality, the manufacturing cost of the driving circuit portion, the ease of manufacture, etc. while changing the number of pixels of the backlight unit 40 for the liquid crystal panel assembly 10 having an arbitrary resolution, and is derived according to the result. The optimal number of pixels of the backlight unit 40 for each resolution of the liquid crystal panel assembly 10 is shown.

Based on the above results, it can be seen that (liquid crystal panel assembly pixel number) / (backlight unit pixel number) is preferably in the range of 240 to 5,852. If the value exceeds 5,852, the effect of improving the dynamic contrast ratio by the backlight unit is insufficient, and if the value is less than 240, the manufacturing and driving of the backlight unit becomes difficult, thereby increasing the manufacturing cost.

In addition, in the present embodiment, one pixel of the backlight unit 40 may be formed to have a size of 2 to 50 mm along the row direction and / or the column direction. If the pixel size in the row direction and / or column direction is less than 2 mm, the backlight unit 40 has a considerable number of pixels, which makes it difficult to process the circuit signal, and the pixel size in the row direction and / or column direction On the contrary, if the amount exceeds 50 mm, the backlight unit 40 has a too small number of pixels, and the image quality improvement effect of the backlight unit 40 is insufficient.

As described above, the liquid crystal display device 100 according to the present embodiment uses the backlight unit 40 having the above-described configuration, and thus, a conventional cold cathode fluorescent lamp (hereinafter referred to as 'CCFL') and a light emitting diode (hereinafter referred to as 'LED'). Compared with the backlight unit of the type, it has the following advantages.

Since the backlight unit 40 of the present embodiment is a surface light source, it does not require a plurality of optical members used for the CCFL type backlight unit and the LED type backlight unit. Therefore, in the backlight unit 40 of the present embodiment, almost no light loss occurs while passing through the optical member, and the light unit 40 does not have to emit light of excessive intensity in consideration of the light loss. Efficiency can be obtained.

In addition, the backlight unit 40 of the present embodiment has a lower power consumption than the CCFL type back light unit, and can reduce the cost by not using the optical member. Low cost In addition, the backlight unit 40 of the present embodiment can be easily applied to a large liquid crystal display device of 30 inches or more because it is easy to enlarge the size.

7 is a block diagram illustrating a display device according to a third exemplary embodiment of the present invention. The display device according to the exemplary embodiment of the present invention is a light receiving element and includes a liquid crystal panel assembly using the liquid crystal element. However, the present invention is not limited thereto.

As shown in FIG. 7, the display device according to the third exemplary embodiment of the present invention includes a liquid crystal panel assembly 10, a gate driver 102 and a data driver 104 connected to the liquid crystal panel assembly 10, and data. The gray voltage generator 106 connected to the driver 104, the backlight unit 40 ′, and a signal controller 108 controlling them are included.

The liquid crystal panel assembly 10 includes a plurality of signal lines G1 -Gn and D1-Dm as viewed in an equivalent circuit, and a plurality of pixels PX connected to the signal lines and arranged in a substantially matrix form. do. The signal lines G1 -Gn and D1 -Dm may include a plurality of gate lines G1 -Gn that transfer gate signals (also referred to as "scan signals"), and a plurality of data lines D1 -Dm that transfer data signals. Include.

Connected to each pixel PX, for example, the i-th (i = 1,2, ... n) gate line Gi and the j-th (j = 1,2, ... m) data line Dj The pixel 11 includes a switching element Q connected to signal lines Gi and Dj, a liquid crystal capacitor Clc, and a storage capacitor Cst connected thereto. Holding capacitor Cst can be omitted as needed.

The switching element Q is a three-terminal element such as a thin film transistor provided on a lower substrate (not shown), the control terminal of which is connected to the gate line Gi, and the input terminal of which is connected to the data line Dj. The output terminal is connected to the liquid crystal capacitor Clc and the storage capacitor Cst.

The gray voltage generator 106 generates two sets of gray voltages (or a set of reference gray voltages) related to the transmittance of the pixel PX. One of the two sets has a positive value for the common voltage Vcom, and the other set has a negative value.

The gate driver 102 is connected to the gate lines G1 -Gn of the liquid crystal panel assembly 10 to receive a gate signal formed of a combination of the gate on voltage Von and the gate off voltage Voff. To apply.

The data driver 104 is connected to the data lines D1-Dm of the liquid crystal panel assembly 10, selects a gray voltage from the gray voltage generator 106, and uses the data driver 104 as a data signal to the data lines D1-Dm. Is authorized. However, when the gray voltage generator 106 provides only a predetermined number of reference gray voltages instead of providing all of the voltages for all grays, the data driver 104 divides the reference gray voltages and thus the gray voltages for all grays. Generate and select the data signal from it.

The signal controller 108 controls the gate driver 102, the data driver 104, the backlight unit controller 110, and the like. The signal controller 108 receives an input image signal R, G, B and an input control signal for controlling the display thereof from an external graphic controller (not shown).

The input image signals R, G, and B contain luminance information of each pixel PX, and luminance has a predetermined number, for example, 1024 (= 2 ¹⁰ ), 256 (= 2 ⁸ ), or 64 ( = 2 ⁶ ) Gray scale. Examples of the input control signal include a vertical sync signal Vsync, a horizontal sync signal Hsync, a main clock MCLK, and a data enable signal DE.

The signal controller 108 appropriately processes the input image signals R, G, and B based on the input image signals R, G, and B and the input control signals according to the operating conditions of the liquid crystal panel assembly 10, and controls the gate. After generating the signal CONT1 and the data control signal CONT2, the gate control signal CONT1 is sent to the gate driver 102, and the data control signal CONT2 and the processed image signal DATA are transferred to the data driver 104). In addition, the signal controller 108 transmits the gate control signal CONT1, the data control signal CONT2, and the processed image signal DATA to the backlight unit controller 110.

The backlight unit 40 ′ includes an anode electrode 62, a backlight unit controller 110, a column driver 112, a scan driver 114, a display unit 116, and an anode driver 120. As illustrated in FIG. 7, the scan driver 114 is connected to the plurality of scan lines S1 -Sp, and each scan line serves as a gate electrode 56 of FIG. 6 of the backlight unit pixel EPX. Do this. In addition, the column driver 112 is connected to a plurality of column lines C1-Cq, and each column line serves as a cathode electrode (52 of FIG. 6) of the backlight unit pixel EPX, and emits electrons. It is connected to the part (58 in Fig. 3).

The anode electrode 62 is included in the front substrate of the backlight unit 40 'and is connected to the anode line AL and the sensing line SL. The anode electrode 62 receives an anode voltage according to the anode control signal AS transmitted to the anode driver 120. At this time, the anode voltage is applied to the anode electrode 62 through the anode line AL and is a high voltage as an acceleration electrode for attracting the emitted electron beam. In addition, when electrons are emitted according to the voltage difference applied to the cathode electrode 52 (FIG. 6) and the gate electrode 56 56 in FIG. 6, the anode current 62 is caused by the electrons attracted to the high voltage to the anode electrode 62. FIG. ) Is generated. The anode current Ia according to the embodiment of the present invention is generated in response to electrons emitted according to a predetermined voltage applied to the cathode electrode 52 (FIG. 6) and the gate electrode 56 (FIG. 6). Therefore, if the anode current Ia is kept above the reference current for the first period, by reducing the voltage applied to the gate electrode (56 in Fig. 6), which may occur in the front substrate of the backlight unit 40 ' The heat generation problem and the damage problem of the backlight unit 40 'can be prevented. Here, the reference current is a threshold current compared with the anode current Ia to determine an abnormal current that may occur in the front substrate including the anode electrode 62, and may have a different value according to a user's setting. In addition, the first period is a predetermined time during which the anode current Ia is maintained above the reference current, and may have a different value according to the user's setting. In addition, the abnormal current may cause a heat generation problem and a temperature deviation to the front substrate including the anode electrode 62, and is an abnormal current applied to prevent the backlight unit 40 ′ from being stably driven.

The anode driver 120 receives the anode control signal AS from the backlight unit controller 110 and applies an anode voltage to the anode electrode 62 according to the signal AS. In addition, the anode driver 120 generates an anode current generated by the anode electrode 62 while electrons are emitted according to a predetermined voltage applied to the cathode electrode 52 (FIG. 6) and the gate electrode 56 (FIG. 6). Ia) is sensed using the sensing line SL. Then, the anode driver 120 transmits the anode current Ia to the backlight unit controller 110. The sensing of the anode current Ia according to the embodiment of the present invention is performed in units of a predetermined period, and the period may have a different value according to the user's setting. In this case, the anode driver 120 converts the measured anode current Ia into digital data and transmits the converted digital data to the backlight unit controller 110. However, the present invention is not limited to this.

The scan driver 114 is connected to the plurality of scan lines S1 -Sp, and each backlight unit pixel EPX is connected to the plurality of liquid crystal pixels EX corresponding to the scan unit control signal CS. A plurality of scan signals are transmitted to synchronously emit light.

The column driver 112 is connected to a plurality of column lines C1-Cq, and each backlight unit pixel EPX corresponds to a plurality of liquid crystals according to the emission control signal CC and the emission signal CLS. Control to emit light corresponding to the gray scale of the pixel EX. The column driver 112 generates a plurality of emission data signals according to the emission signal CLS and transmits the plurality of emission data signals to the plurality of column lines C1-Cq according to the emission control signal CC. That is, the backlight pixel EPX is synchronized with the image displayed on the plurality of liquid crystal pixels EX corresponding to one backlight unit pixel EPX so as to emit light with a predetermined gray scale.

The display unit 116 includes a plurality of scan lines S1 -Sp for transmitting a scan signal, a plurality of column lines C1-Cq for transmitting a light emission data signal, and a plurality of backlight unit pixels EPX. Each of the plurality of backlight unit pixels EPX is positioned in a region defined by the scan lines S1 -Sp and the column lines C1 -Cq intersecting the scan lines. The scan lines S1-Sp are connected to the scan driver 114, and the column lines C1 -Cq are connected to the column driver 112. The scan driver 114 and the column driver 112 are connected to the backlight unit controller 110 to operate according to the control signal of the backlight unit controller 110.

The backlight unit controller 110 detects the highest gray level among the plurality of pixels PX corresponding to one pixel EPX of the backlight unit, and the plurality of pixels corresponding to the detected gray level. The gray level of the backlight unit pixel EPX is determined. In addition, the backlight unit controller 110 converts the data into digital data and transmits the converted digital data to the column driver 112, and the digital data is included in the emission signal CLS. In addition, the backlight unit controller 110 generates a scan driving control signal CS using the gate control signal CONT1 and transmits the scan driving control signal CS to the scan driver 114. In addition, the backlight unit controller 110 generates the emission control signal CC using the data control signal CONT2, and transmits the generated emission control signal CC to the column driver 112.

In addition, the backlight unit controller 110 receives the sensed anode current Ia while electrons are emitted according to the voltage difference applied to the cathode electrode 52 (FIG. 6) and the gate electrodes 56 (FIG. 6). . At this time, the anode current Ia is measured in a predetermined period and transferred to the backlight unit controller 110. Then, the backlight unit controller 110 compares the anode current Ia with the reference current. As a result of the comparison, when the anode current Ia is greater than the reference current, the backlight unit controller 110 determines whether the anode current Ia is maintained for a first period in a state larger than the reference current. At this time, when the anode current Ia is maintained for a first period in a state larger than the reference current, the backlight unit controller 110 detects the first abnormal abnormal current, and reduces the anode current Ia to decrease the gate electrode The voltage applied to 56 in FIG. 6 is reduced. The backlight unit controller 110 according to an exemplary embodiment of the present invention reduces the voltage applied to the gate electrode 56 of FIG. 6, thereby applying the voltage applied to the cathode electrode 52 and the gate electrodes 56. You can reduce the car. As a result, the anode current Ia can be reduced by reducing the amount of electrons emitted correspondingly. The backlight unit controller 110 reduces the voltage applied to the gate electrode 56 of FIG. 6 and compares the sensed anode current Ia with a reference current. In this case, when the anode current Ia is greater than the reference current, the backlight unit controller 110 determines whether the anode current Ia is maintained for a first period in a state greater than the reference current. As a result of determination, when the anode current Ia is maintained for a first period in a state larger than the reference current, the backlight unit controller 110 detects a second abnormal current and an abnormal current flows in the backlight unit 40 '. Judging by it. According to an embodiment of the present invention, if the anode current Ia is maintained for more than a reference current for a first period even after the voltage applied to the gate electrode 56 of FIG. 6 is reduced, the anode substrate 62 includes A heat generation problem may occur, thereby causing a temperature variation of the front substrate, which may cause damage to the backlight unit 40 '. Therefore, the backlight unit controller 110 controls the anode driver 120 so that the anode voltage delivered to the anode electrode 62 is gradually reduced, thereby ensuring stability of the backlight unit 40 ', and at the same time, By turning off the other power supply, damage to the backlight unit 40 'due to an abnormal current is prevented.

8 is a flowchart illustrating a process of determining an abnormal current flowing in the backlight unit 40 'by using the anode current Ia according to the third embodiment of the present invention.

First, the anode driver 120 senses the anode current Ia and transmits it to the backlight unit controller 110 (S100).

The backlight unit controller 110 compares the anode current Ia with a reference current (S200).

As a result of the comparison in operation S200, when the anode current Ia is smaller than the reference current, the backlight unit controller 110 determines that an abnormal current does not flow in the backlight unit 40 ′ and performs the process again from operation S100. As a result of the comparison in operation S200, when the anode current Ia is greater than the reference current, the backlight unit controller 110 determines whether the anode current Ia is maintained for more than a reference current for a first period of time (S300).

As a result of the comparison in operation S300, when the anode current Ia is not maintained for more than the reference current for the first period, the backlight unit controller 110 determines that an abnormal current does not flow in the backlight unit 40 ′, and in operation S100. To start again. As a result of the comparison in operation S300, when the anode current Ia is maintained for more than a reference current for the first period, the backlight unit controller 110 reduces the voltage applied to the gate electrode 56 of FIG. 6 (S400).

The anode driver 120 senses the anode current Ia and transmits it to the backlight unit controller 110 (S500).

The backlight unit controller 110 compares the anode current Ia with a reference current (S600).

As a result of the comparison in operation S600, when the anode current Ia is smaller than the reference current, the backlight unit controller 110 determines that an abnormal current does not flow in the backlight unit 40 ′ and performs again from operation S100. As a result of the comparison in operation S600, when the anode current Ia is greater than the reference current, the backlight unit controller 110 determines whether the anode current Ia is maintained for more than the reference current for the first period (S700).

As a result of the comparison in operation S700, when the anode current Ia is not maintained for more than the reference current for the first period, the backlight unit controller 110 determines that an abnormal current does not flow in the backlight unit 40 ′, and in operation S100. To start again. As a result of the comparison in operation S700, when the anode current Ia is maintained for more than a reference current for the first period, the backlight unit controller 110 gradually decreases the voltage delivered to the anode electrode 62, and at the same time, another power source. Turn off (S800).

As such, when the anode current Ia is maintained for more than the reference current for the first period, damage caused by the abnormal current of the backlight unit 40 'is reduced by reducing the voltage applied to the gate electrode 56 of FIG. It can prevent and can stably drive the backlight unit 40 '.

The embodiment using a display device using a liquid crystal panel assembly has been described so far, but the present invention is not limited thereto. As a display device other than self-luminous, it is applicable to both display devices that receive images from a backlight unit and display an image.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications and changes can be made within the scope of the claims and the detailed description of the invention and the accompanying drawings. Naturally, it belongs to the range of.

The light emitting device, the display device using the same, a method of driving the light emitting device, and a method of driving the display device according to the features of the present invention may determine whether abnormal current flows through the backlight unit using the anode current. In this case, when an abnormal current is detected in the backlight unit, the voltage applied to the gate electrode may be reduced to prevent damage due to heat generation and temperature deviation caused by the abnormal current, thereby stably driving the backlight unit. .

Claims

A panel assembly including a plurality of gate lines for transmitting a plurality of gate signals, a plurality of data lines for transmitting a plurality of data signals, and a plurality of pixels defined by the plurality of gate lines and the plurality of data lines, and

A plurality of scan lines transferring a plurality of scan signals, a plurality of column lines transferring a plurality of light emitting data signals, a plurality of backlight unit pixels defined by the plurality of scan lines and the plurality of column lines, and an anode voltage It includes an anode electrode is applied,

When the first current flowing through the anode is sensed and the first current is maintained for more than a reference current for a first period of time, a voltage applied to the plurality of scan signals is decreased, and a voltage applied to the plurality of scan signals. And a backlight unit to reduce the anode voltage and to turn off the power when the first current is maintained for more than the reference current for a first period even after the decrease.

The method of claim 1,

And a first backlight unit pixel of the plurality of backlight unit pixels corresponds to a plurality of pixels of the panel assembly, and emits light with luminance corresponding to the highest gray level among the plurality of pixels.

The method of claim 2,

The backlight unit,

The display device to sense the abnormal current of the backlight unit by sensing the first current in a predetermined period unit.

The method of claim 3,

The reference current is,

And a threshold current compared to the first current to determine an abnormal current that may occur in the front substrate of the backlight unit.

When the first current flowing through the anode is sensed and the first current is maintained for more than a reference current for a first period of time, a voltage applied to the plurality of scan signals is decreased, and a voltage applied to the plurality of scan signals. And a backlight unit which reduces the anode voltage and turns off the power when the first current is maintained for more than the reference current for the first period even after reducing the voltage.

The method of claim 5,

The backlight unit,

The light emitting device to sense the abnormal current of the backlight unit by sensing the first current in a predetermined period unit.

The method of claim 6,

The first current is,

And an anode current generated in the anode electrode by electrons emitted according to the voltage difference between each of the plurality of scan signals and the plurality of light emitting data signals.

A method of driving a display device comprising a panel assembly for displaying an image, and a backlight unit for supplying a backlight to the panel assembly and including a plurality of scan lines and a plurality of column lines.

(a) sensing the first current and comparing it with the reference current;

(b) in step a), if the first current is greater than or equal to the reference current, determining whether the first current is maintained for greater than or equal to the reference current for a first period of time;

(c) in step b), if the first current is maintained for more than the reference current for a first period of time, reducing the voltage applied to the plurality of scan lines,

(d) sensing the first current and comparing it with the reference current;

(e) in step d), if the first current is greater than or equal to the reference current, determining whether the first current is maintained for greater than or equal to the reference current for a first period of time, and

and (f) in step e), if the first current is maintained for more than the reference current for a first period, reducing the anode voltage and turning off the power.

The method of claim 8,

The panel assembly includes a plurality of pixels, the backlight unit includes a plurality of backlight unit pixels,

The first backlight unit pixel of the plurality of backlight unit pixels corresponds to a plurality of pixels of the panel assembly, and emits light at a luminance corresponding to the highest gray level among the plurality of pixels.

(a) sensing the first current and comparing it with the reference current;

(d) sensing the first current and comparing it with the reference current;