KR20080024825A - Backlight unit and liquid crystal display comprising the same - Google Patents

Abstract

A backlight unit and a liquid crystal display having the same are provided to solve a problem that the number of LEDs(Light Emitting Diodes) increases as the size of a display device increases. A plurality of scan lines(210) extends in the first direction. A plurality of power supply lines(230) extends in the second direction, crossing the scan lines. Light source sets(240) are provided at each crossing of the scan lines and the power supply lines and arranged in a matrix form. A power supply unit(250) is connected with the power supply line and provides drive power based on a video signal to the light source sets. Switching elements(211) are connected with the scan lines. A scan line driver(220) sequentially turns on the switching elements at a certain period. The power supply unit supplies the driver power to the power supply lines in synchronization with the switching elements which are sequentially turned on.

Description

BACKLIGHT UNIT AND LIQUID CRYSTAL DISPLAY COMPRISING THE SAME}

1 is a control block diagram of a liquid crystal display according to a first embodiment of the present invention;

2A is a schematic diagram of a light source set according to a first embodiment of the present invention,

2B is a view for explaining the charging of the light source set according to the first embodiment of the present invention,

3 is a graph illustrating waveforms of a driving power source according to a first embodiment of the present invention;

4 is a control block diagram of a backlight unit according to a second embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

100: liquid crystal panel 110: liquid crystal panel driver

200: backlight unit 210: scanning line

220: scan line driver 230: power supply line

240: light source set 250, 270: power supply

260: light source control unit

The present invention relates to a backlight unit and a liquid crystal display including the same, and more particularly, to a backlight unit including a point light source and a liquid crystal display including the same.

Recently, a flat panel display such as a liquid crystal display (LCD), a plasma display panel (PDP), or an organic light emitting diode (OLED) has been developed in place of the conventional CRT.

Among them, the liquid crystal display includes a thin film transistor substrate, a color filter substrate, and a liquid crystal panel in which liquid crystal is injected between both substrates. Since the liquid crystal panel is a non-light emitting device, a backlight unit for supplying light is disposed on the rear surface of the thin film transistor substrate. Light transmitted from the backlight unit is adjusted according to the arrangement of liquid crystals.

Recently, a lamp as a line light source and a light emitting diode as a point light source are widely used as a backlight unit, and local dimming for partially controlling the light of the backlight is realized according to a consumer's preference.

The light emitting diode is usually driven by a regulator or a PWM IC. The number of light emitting diodes used for increasing the size of the display device and expressing the fine gray scales is increasing. The backlight unit has to be provided with a plurality of power driving parts in proportion thereto. An increase in the power driver causes a cost increase and increases the driving burden of the backlight unit due to the control of a plurality of drivers.

Accordingly, an object of the present invention is to provide a backlight unit and a liquid crystal display including the same, which reduce manufacturing costs and are easy to drive.

The object is, according to the present invention, a plurality of scanning lines extending in the first direction; A plurality of power supply lines extending in a second direction crossing the scan lines; A light source set provided at an intersection point of the scan line and the power supply line and arranged in a matrix; It is connected to the power supply line, and is achieved by a backlight unit including a power supply for supplying a driving power based on the image signal to the light source set.

A switching element connected to the scan line; The apparatus may further include a scan line driver configured to sequentially turn on the switching device at a predetermined cycle.

Preferably, the power supply unit supplies driving power to the power supply line in synchronization with the switching elements that are sequentially turned on.

The power supply unit includes a sampling and holding unit for shifting and storing the input driving power for each power supply line; It may include a power amplifier for amplifying the driving power output from the sampling and holding unit.

A digital signal related to an image signal is input to the power supply unit, and the power supply unit includes a storage unit which stores the input digital signal for each power supply line; A DA converter converting the stored digital signal into an analog driving power source; It may include a power amplifier for amplifying the converted analog coin source.

Preferably, the power amplifier amplifies the input signal by about 450 to 550 times.

The light source set includes a light emitting diode connected in parallel to the power supply line, a capacitor connected in parallel to the light emitting diode, and a resistor connected in series to the light emitting diode, wherein the capacitor and the resistor It is connected to the scan line.

On the other hand, the above object is, according to the present invention, a liquid crystal panel for displaying a video signal; A plurality of scan lines extending in a first direction; A plurality of power supply lines extending in a second direction crossing the scan lines; A light source set provided at an intersection point of the scan line and the power supply line and arranged in a matrix; It may also be achieved by a liquid crystal display device connected to the power supply line and including a backlight unit including a power supply unit supplying driving power based on an image signal to the light source set.

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

In various embodiments, like reference numerals refer to like elements, and like reference numerals refer to like elements in the first embodiment and may be omitted in other embodiments.

1 is a control block diagram of a liquid crystal display according to a first embodiment of the present invention, FIG. 2A is a schematic diagram of a light source set, and FIG. 2B is a view for explaining charging of a light source set according to a first embodiment of the present invention. 3 is a graph showing waveforms of a driving power source according to a first embodiment of the present invention. A first embodiment of the present invention will be described with reference to FIGS.

As shown, the liquid crystal display according to the present exemplary embodiment includes a liquid crystal panel 100, a liquid crystal panel driver 110 for driving the liquid crystal panel, and a backlight unit 200.

The liquid crystal panel 100 has a rectangular shape and an image is displayed by a data signal and a gate signal applied by the liquid crystal panel driver 110. The liquid crystal panel 100 includes a thin film transistor substrate on which a thin film transistor (not shown) is formed, a color filter substrate provided to face the thin film transistor substrate, and a liquid crystal layer formed between both substrates. The thin film transistor substrate is provided with a gate line for transmitting a scan signal and a data line for transmitting a data signal. In addition, a pixel electrode, which is connected to a thin film transistor and implements an image, is formed in a pixel region defined as an intersection region of a gate line and a data line.

The liquid crystal panel driver 110 applies a data signal corresponding to a gate signal and an image signal to the liquid crystal panel 100 according to an image signal and a signal control signal input from the outside. The liquid crystal panel driver 110 includes an analog voltage generator for generating a gate signal and various analog signals, a gate driver, a data driver, and a timing controller for controlling them. The liquid crystal panel driver 110 provides information about the image signal to the light source controller 260 which will be described later.

The backlight unit 200 includes a scan line 210, a scan line driver 220 connected to the scan line 210, a power supply line 230 intersecting with the scan line 210, and a scan line 210. And a light source set 240 formed at an intersection point of the power supply line 230, a power supply unit 250 supplying driving power to the light source set 240, and a light source control unit 260 controlling them.

The scan line 210 extends in the first direction and is connected to the scan line driver 220, and a switching element 211 is connected between the scan line driver 220 and the scan line 210. The scan line driver 220 sequentially turns on the switching element 211. When the switching element 211 is turned on, driving power is applied to the light source set 240 connected to one scan line 210. That is, the driving power is applied line by line to the light source set 240 line by line by the scan line 210. The scan line driver 220 receives a control signal for the turn-on timing of the switching device from the light source controller 260. Typically, 60 frames are formed in the liquid crystal panel 100 per second. Since the driving power applied to the light source set 240 is determined according to the information gray level information of the image signal, the switching element 211 connected to one scan line 210 is turned on 60 times per second. Alternatively, the switching element 211 may be turned on in synchronization with a plurality of frames instead of one frame.

The power supply line 230 extends in a second direction crossing the scan line driver 220 like a data line of the liquid crystal panel 100 to transfer driving power to the light source set 240.

The light source set 240 is connected to the intersection of the scan line 210 and the power supply line 230 and receives a driving voltage in line units by turning on the switching element 211. As shown in FIG. 2A, the light source set 240 is connected in parallel to a light emitting diode 241 which is a point light source, a resistor R 242 connected in series to the light emitting diode 241, and a light emitting diode 241. It consists of a capacitor (C) 243 connected. The resistor 242 and the capacitor 243 are connected to the scan line 210.

When the driving power I is input to the light source set 240, the driving power I is transmitted to the capacitor 243 and the light emitting diode 241, and the capacitor 243 charges the driving power I. In this case, the resistor 242 connected to the light emitting diode 241 prevents overcurrent from flowing through the light emitting diode 241. The driving power I is supplied while the switching element 211 is turned on. When the switching element 211 is turned off, the supply of the driving power I is stopped and the resistor 242 and the capacitor 243 are connected to the ground terminal. Connected. When the switching element 211 is turned off, the light emitting diode 241, the resistor 242, and the capacitor 243 form a closed circuit, and the charging power source II charged in the capacitor 243 is transferred to the light emitting diode 241. Discharge slowly.

As shown in FIG. 2B, when the switching element 211 is turned on, the driving power I is applied to the light source set 240 as one pulse (a). (b) shows the driving power supplied to the light emitting diode 241. First, the driving power supplied to the light emitting diode 241 is driven by the input driving power I. When the switching element 211 is turned off, the capacitor 243 is discharged from the capacitor 243. It is driven by the charging power source II. That is, at first, a large driving power source I is temporarily stored in the capacitor 243, and then the light emitting diode 241 is driven for one frame with a gradually low charging power source II, so that the power supply does not need to be continuously supplied.

In the related art, since driving circuit units had to be connected to individual light emitting diodes, there was an increase in manufacturing cost and difficulty in driving circuits. In the case of the light source set 240 according to the present embodiment, power consumption is reduced because the driving power does not need to be continuously supplied, and the driving circuit unit is separately provided because the light source set 240 is arranged for each line. Since it is not necessary to reduce the manufacturing cost, there is an advantage that it is easy to drive.

The power supply unit 250 is provided in plural and individually connected to the power supply line 230, and supplies driving power based on the image signal to the light source set 240. The power supply unit 250 substantially drives a plurality of sampling and holding units 251 for shifting and storing the input driving power for each power supply line and the driving power output from the sampling and holding unit 251. And a power amplifier 253 which amplifies the power.

In this embodiment, the driving power input to the power supply unit 250 is an analog signal and its strength is small so that it is amplified to be input to the light source set 240. The driving power input to the power supply unit 250 is a value set based on the gray level of the image signal. That is, a large driving power is applied to the light source set 240 facing the portion where the bright image is displayed, while a low driving power is applied to the light source set 240 facing the portion where the dark image is displayed. The brightness of the light emitted from 240 is adjusted differently.

The sampling and holding unit 251 converts and stores the driving power input in series according to the control signal applied from the light source control unit 260 into parallel driving power per row. The sampling and holding unit 251 captures driving power corresponding to the power supply line 230 by the enable signal applied from the light source control unit 260, and holds the driving power captured by the disable signal. The driving power is shifted to the adjacent sampling and holding unit 251. When the process is completed in all the sampling and holding units 251, the driving power corresponding to one line is simultaneously driven by the driving power output signal such as the horizontal synchronization signal. The output is 253. The sampling and holding unit 251 includes a sampling circuit including a plurality of capacitors and switching elements.

The power amplifier 253 amplifies the driving power output from the sampling and holding unit 251 and supplies it to the light source set 240. The power amplifier 253 may be provided as a regulator for adjusting the level of the input power, and amplify the level of the input power by about 450 to 550 times. Since the brightness of the light emitting diode 241 constituting the light source set 240 is adjusted by the magnitude of the current, the power amplifier 253 preferably amplifies the current value of the input power. The power amplifier 253 outputs the driving power to the light source set 240 at a time for each line in response to the driving power output signal ((5) of FIG. 3) output from the light source controller 260.

The light source controller 260 receives an image signal and a vertical synchronization signal from the liquid crystal panel driver 110, and outputs a control signal for controlling the scan line driver 220 and the power supply 250. As described above, the light source controller 260 outputs a control signal to the scan line driver 220 so that the scan line 210 can be turned on in synchronization with the vertical synchronization signal applied to the liquid crystal panel 100, and the sampling hold. A sampling hold enable signal for shifting the driving power input to the unit 251 is output, and the driving power output signal is applied to the power amplifier 253.

3 is a graph illustrating output waveforms of the sampling and holding unit 251 and the power amplifier unit 253. (1) shows an arbitrary drive power input, and (1) is amplified as (6) in the future. (2), (3), and (4) show that the sampling and holding unit 251 captures the corresponding driving power according to the sampling and holding enable signal output from the light source control unit 260. Each driving power is sequentially captured by the sampling and holding unit 251, and then is held for a predetermined time and simultaneously outputted to a line of light source sets 240 by a driving power output signal as shown in (5). The initial driving power supplied to the light source set 240 is amplified by the power amplifier 253 and output as shown in (6).

4 is a control block diagram of a backlight unit according to a second embodiment of the present invention.

As shown, the backlight unit according to the present embodiment is configured similarly to the first embodiment except for the power supply unit 270.

The power supply unit 270 receives a digital signal related to a driving power and includes a DA converter 273 to process the digital signal. The power supply unit 270 further includes a storage unit 271 for storing the input digital signal for each power supply line 230.

The DA converter 273 generates and outputs an analog drive power of a predetermined level based on the digital signal input from the storage 271. The analog driving power output from the DA converter 273 is amplified by the power amplifier 275 and then transferred to the light source set 240.

The power amplifier 275 is a component that may be selectively provided according to the capacity and processing capacity of the DA converter 273.

 According to this embodiment, there is an advantage that the driving power can be easily and quickly supplied to the backlight unit 200 by processing the input digital signal.

Although some embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that modifications may be made to the embodiment without departing from the spirit or spirit of the invention. . It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

As described above, according to the present invention, there is provided a backlight unit having a low manufacturing cost and easy driving, and a liquid crystal display including the same.

Claims (12)

A plurality of scan lines extending in a first direction; A plurality of power supply lines extending in a second direction crossing the scan lines; A light source set provided at an intersection point of the scan line and the power supply line and arranged in a matrix; And a power supply unit connected to the power supply line to supply driving power based on an image signal to the light source set. The method of claim 1, A switching element connected to the scan line; And a scan line driver configured to sequentially turn on the switching element at a predetermined cycle. The method of claim 2, And the power supply unit supplies driving power to the power supply line in synchronization with the switching elements sequentially turned on. The method of claim 1, The power supply unit, A sampling and holding unit for shifting and storing the input driving power for each power supply line; And a power amplifier configured to amplify the driving power output from the sampling and holding unit. According to claim 1, A digital signal related to an image signal is input to the power supply unit, The power supply unit, A storage unit for storing the input digital signal for each power supply line; A DA converter converting the stored digital signal into an analog driving power source; And a power amplifier configured to amplify the converted analog driving power. The method according to claim 4 or 5, And the power amplifier amplifies the input signal by about 450 to 550 times. The method of claim 6, The light source set includes a light emitting diode connected in parallel to the power supply line, a capacitor connected in parallel to the light emitting diode, and a resistor connected in series to the light emitting diode, And the capacitor and the resistor are connected to the scan line. A liquid crystal panel displaying an image signal; A plurality of scan lines extending in a first direction; A plurality of power supply lines extending in a second direction crossing the scan lines; A light source set provided at an intersection point of the scan line and the power supply line and arranged in a matrix; And a backlight unit connected to the power supply line, the backlight unit including a power supply unit supplying driving power based on an image signal to the light source set. The method of claim 8, The backlight unit further includes a switching element connected to the scan line, and a scan line driver for sequentially turning on the switching element at a predetermined cycle. And the power supply unit supplies driving power to the power supply line in synchronization with the switching elements sequentially turned on. The method of claim 8, The power supply unit, A sampling and holding unit for shifting and storing the input driving power for each power supply line; And a power amplifier for amplifying the driving power output from the sampling and holding unit. The method of claim 8, A digital signal related to an image signal is input to the power supply unit, The power supply unit, A storage unit for storing the input digital signal for each power supply line; A DA converter converting the stored digital signal into an analog driving power source; And a power amplifier for amplifying the converted analog driving power. The method according to claim 10 or 11, wherein The light source set includes a light emitting diode connected in parallel to the power supply line, a capacitor connected in parallel to the light emitting diode, and a resistor connected in series to the light emitting diode, And the capacitor and the resistor are connected to the scan line.

Images