KR20110064124A - Backlight unit and liquid crystal display device using the same - Google Patents

Abstract

PURPOSE: A backlight unit and liquid display device using the same are provided to improve a hot spot expressing a specific area with an efficiency improvement and a cost reducing effect of a light source. CONSTITUTION: A liquid display device includes a liquid crystal panel and a backlight unit(BLU). The backlight unit includes a compensation unit which is located between a light source unit and a plurality of light source. The compensation unit is a load with the same resistance component with the light source included in the plurality of light source. The compensation includes a resistor with the same resistance component with the light source. The backlight unit includes a plurality of light source unit. The compensation unit includes at least one light source unit among the plurality of light source unit.

Description

Backlight unit and liquid crystal display device using the same

The present invention relates to a backlight unit and a liquid crystal display device using the same.

With the development of information technology, the market for a display device, which is a connection medium between a user and information, is growing. Accordingly, flat panel displays (FPDs), such as liquid crystal displays (LCDs), organic light emitting diodes (OLEDs), and plasma display panels (PDPs), may be used. Usage is increasing. Among them, liquid crystal displays capable of realizing high resolution and being capable of miniaturization as well as large scale are widely used.

The liquid crystal display device includes a liquid crystal layer positioned between a transistor substrate on which a thin film transistor, a storage capacitor, a pixel electrode, and the like are formed, and a color filter substrate on which a color filter and a black matrix are formed. The LCD displays an image by emitting light incident from the backlight unit by adjusting an arrangement direction of the liquid crystal layer to an electric field applied to a pixel electrode and a common electrode formed on a transistor substrate or a color filter substrate.

Some of the liquid crystal display devices use a backlight unit using a plurality of light source units. The backlight unit using a plurality of light source units arranged as described above is arranged in a plurality of light source units to prepare for defects such as non-emission. However, the conventional backlight unit having such a configuration requires the same number of light sources for each light source unit in order to improve the brightness and display quality of the liquid crystal display device. Improvement is needed.

The present invention for solving the problems of the above-described background, by configuring the number of light sources included in the backlight unit to satisfy the brightness and specifications (Spec) and to prevent unnecessary insertion of light sources to improve the efficiency of the light source and reduce the cost In addition, the present invention provides a backlight unit capable of improving a hot spot appearing in a specific area and a liquid crystal display using the same.

The present invention as a problem solving means described above, the liquid crystal panel; And a backlight unit that provides light to the liquid crystal panel and includes a light source unit including a plurality of light sources arranged in series and a compensation unit positioned between the plurality of light sources.

The compensator may be a load having the same resistance component as the light sources included in the plurality of light sources.

The compensator may include a resistor having the same resistance component as the light sources included in the plurality of light sources.

The backlight unit may include a plurality of light source units connected in parallel.

The compensator may be included in at least one light source unit among the plurality of light source units.

One terminal of the plurality of light source units may be connected in common, and the other terminal of the plurality of light source units may correspond to the number of the light source units.

One terminal of the plurality of light source units may be adjacent to a power supply unit for supplying power to the plurality of light source units, and the other terminal of the plurality of light source units may be adjacent to a driving element for driving the plurality of light source units.

The plurality of light sources may include light emitting diodes.

In another aspect, the present invention, the power supply; A driving element controlling the power output from the power supply unit; A plurality of light sources connected in parallel with a plurality of light sources arranged in series between the power supply unit and the driving element; And a compensation unit positioned between the plurality of light sources.

The compensator may be a load having the same resistance component as the light sources included in the plurality of light sources.

According to the present invention, a desired number of light sources included in the backlight unit can be configured to satisfy brightness and specifications, and to prevent unnecessary light source insertion, thereby improving the efficiency and cost of light sources and improving hot spots appearing in specific areas. There is an effect of providing a backlight unit and a liquid crystal display device using the same.

Hereinafter, with reference to the accompanying drawings, the specific content for the practice of the present invention will be described.

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention, FIG. 2 is a block diagram of a gate driver, and FIG. 3 is a block diagram of a data driver.

As shown in FIG. 1, the liquid crystal display according to the exemplary embodiment may include a timing driver TCN, a liquid crystal panel PNL, a gate driver SDRV, a data driver DRV, and a backlight unit BLU. And a backlight unit driver BDRV and a power supply PWR.

The timing driver TCN receives a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a data enable signal Data Enable, DE, a clock signal CLK, and a data signal DATA from the outside. The timing driver TCN uses the timing signals such as the vertical synchronization signal Vsync, the horizontal synchronization signal Hsync, the data enable signal Data Enable, and the clock signal CLK, and the gate of the data driver DDRN and the gate. The operation timing of the driver SDRV is controlled. Since the timing driver TCN may determine the frame period by counting the data enable signal DE of one horizontal period, the vertical synchronization signal Vsync and the horizontal synchronization signal Hsync supplied from the outside may be omitted. The control signals generated by the timing driver TCN include a gate timing control signal GDC for controlling the operation timing of the gate driver SDRV and a data timing control signal DDC for controlling the operation timing of the data driver DDR. ) May be included. The gate timing control signal GDC includes a gate start pulse (GSP), a gate shift clock (GSC), a gate output enable signal (Gate Output Enable, GOE), and the like. The gate start pulse GSP is supplied to a gate drive integrated circuit (IC) where the first gate signal is generated. The gate shift clock GSC is a clock signal commonly input to gate drive ICs and is a clock signal for shifting the gate start pulse GSP. The gate output enable signal GOE controls the output of the gate drive ICs. The data timing control signal DDC includes a source start pulse (Source, Start Pulse, SSP), a source sampling clock (SSC), a source output enable signal (Source Output Enable, SOE), and the like. The source start pulse SSP controls the data sampling start time of the data driver DDRV. The source sampling clock SSC is a clock signal that controls the sampling operation of data in the data driver DDRV based on the rising or falling edge. The source output enable signal SOE controls the output of the data driver DDRV. Meanwhile, the source start pulse SSP supplied to the data driver DVV may be omitted according to the data transmission method.

The liquid crystal panel PNL includes a liquid crystal layer positioned between the transistor substrate (hereinafter, abbreviated as TFT substrate) and the color filter substrate and includes sub pixels arranged in a matrix form. Data lines, gate lines, TFTs, storage capacitors, and the like are formed on the TFT substrate, and black matrices, color filters, and the like are formed on the color filter substrate. One subpixel SP is defined by the data line DL1 and the gate line SL1 that cross each other. The sub pixel SP includes a TFT driven by a gate signal supplied through the gate line SL1, and a storage capacitor Cst and a storage capacitor Cst that store the data signal supplied through the data line DL1 as a data voltage. Includes a liquid crystal cell Clc that is driven by the data voltage stored therein. The liquid crystal cell Clc is driven by the data voltage supplied to the pixel electrode 1 and the common voltage Vcom supplied to the common electrode 2. The common electrode is formed on the color filter substrate in a vertical electric field driving method such as twisted nematic (TN) mode and vertical alignment (VA) mode, and a horizontal electric field such as IPS (In Plane Switching) mode and FFS (Fringe Field Switching) mode. In the driving method, a pixel electrode is formed on the TFT substrate. The polarizing plate is attached to the TFT substrate and the color filter substrate of the liquid crystal panel PNL, and an alignment layer for setting the pre-tilt angle of the liquid crystal is formed. The liquid crystal mode of the liquid crystal panel PNL may be implemented in any liquid crystal mode as well as the above-described TN mode, VA mode, IPS mode, and FFS mode.

The gate driver SDRV is a swing width of the gate driving voltage at which the transistors of the subpixels SP included in the display panel PNL can operate in response to the gate timing control signal GDC supplied from the timing driver TCN. The gate signal is sequentially generated while shifting the signal level. The gate driver SDRV supplies the gate signals generated through the gate lines SL1 to SLm to the subpixels SP included in the display panel PNL. As shown in FIG. 2, the gate driver SDRV includes gate drive ICs. The gate drive ICs each include a shift register 61, a level shifter 63, and a plurality of AND gates (hereinafter referred to as "AND gates") 62 connected between the shift register 61 and the level shifter 63. And an inverter 64 for inverting the gate output enable signal GOE and the like. The shift register 61 sequentially shifts the gate start pulse GSP according to the gate shift clock GSC using a plurality of D-flip flops connected in a cascade manner. The AND gates 62 generate an output by ANDing the output signal of the shift register 61 and the inverted signal of the gate output enable signal GOE, respectively. The inverter 64 inverts the gate output enable signal GOE and supplies it to the AND gates 62. The level shifter 63 shifts the output voltage swing width of the AND gate 62 to the swing width of the gate voltage at which the transistors included in the display panel PNL can operate. The gate signal output from the level shifter 63 is sequentially supplied to the gate lines SL1 to SLm.

The data driver DDRV samples and latches the data signal DATA supplied from the timing driver TCN in response to the data timing control signal DDC supplied from the timing driver TCN to convert the data signal DATA into data of a parallel data system. . The data driver DDRV converts the data signal DATA into a gamma reference voltage when converting the data into a parallel data system. The data driver DDRV supplies the data signal DATA converted through the data lines DL1 to DLn to the subpixels SP included in the display panel PNL. As shown in FIG. 3, a shift register 51, a data register 52, a first latch 53, a second latch 54, a converter 55, an output circuit 56, and the like are included. The shift register 51 shifts the source sampling clock SSC supplied from the timing driver TCN. The shift register 51 transfers a carry signal CAR to a shift register of a source driver IC of a neighboring next stage. The data register 52 temporarily stores the data signal DATA supplied from the timing driver TCN and supplies it to the first latch 53. The first latch 53 samples and latches a data signal DATA input in series according to a clock sequentially supplied from the shift register 51, and simultaneously outputs the latched data. The second latch 54 latches data supplied from the first latch 53 and then latches data latched in synchronization with the second latch 54 of other source drive ICs in response to the source output enable signal SOE. Output at the same time. The converter 55 converts the data signal DATA input from the second latch 54 into gamma reference voltages GMA1 to GMAn. The data signal DATA output from the output circuit 56 is supplied to the data lines DL1 to DLn in response to the source output enable signal SOE.

The backlight unit BLU provides light to the liquid crystal panel PNL. The backlight unit BLU includes a light source unit including a plurality of light sources and a compensation unit positioned between the plurality of light sources. The light source may be a light emitting diode, but is not limited thereto. The backlight unit BLU may be formed as an edge type including a plurality of light sources, a light guide plate, an optical sheet, or the like, or a direct type including a plurality of light sources, an optical sheet, or the like. The edge type backlight unit BLU has a structure in which a plurality of light sources are arranged in a line (or string) shape so as to face the side of the light guide plate, and a plurality of optical sheets are disposed between the liquid crystal panel PNL and the light guide plate. In contrast, the direct type backlight unit BLU has a structure in which a plurality of optical sheets and the like are disposed under the liquid crystal panel PNL and a plurality of light sources are disposed in a block form.

The backlight unit driver BDRV receives a data signal DATA and a global dimming signal Dim from a timing controller TCN or an external system board, and the lines or blocks of the backlight unit BLU based on the supplied image. The image is analyzed in units of blocks of an image corresponding to the size, and a local dimming value is generated according to the analysis result. The backlight unit driver BDRV generates a control signal in the form of a pulse width modulation signal having a local dimming value of 0% to 100% and drives the backlight unit BLU by using the control signal.

The power supply unit PWR converts AC power supplied from the outside into DC power DC and supplies the same to the backlight unit BLU. The power supply unit PWR may include, but is not limited to, a power conversion unit, a transformer unit, an output control unit, and the like to convert AC power AC into DC power DC. The power conversion unit may be configured as a passive or active switching converter to convert AC power to primary DC power. The transformer unit may be configured as a transformer for transforming the primary DC power output from the power conversion unit into the secondary DC power. The output control unit may be composed of a voltage controlled oscillator (VCO), a feedback circuit, a passive element, and the like to rectify the secondary DC power output from the transformer unit and output it in a stable state.

Hereinafter, a liquid crystal display according to an exemplary embodiment of the present invention will be described in more detail.

4 is a partial block diagram of a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 5 is a partial block diagram of a backlight unit according to an exemplary embodiment of the present invention.

1 to 4, a liquid crystal display according to an exemplary embodiment of the present invention includes a backlight unit BLU for providing light to the liquid crystal panel PNL and a power supply for supplying power to the backlight unit BLU. And a supply unit PWR and a backlight unit driver BDRV.

The backlight unit driver BDRV includes a dimming controller DIM, a driver DIC, and a driving device DR. The dimming controller DIM receives a data signal DATA and a global dimming signal Dim from a timing controller TCN or an external system board, and blocks or blocks the backlight unit BLU based on the supplied image. An image is analyzed in units of blocks of an image corresponding to a star size, and a local dimming value is generated according to the analysis result. The dimming controller DIM supplies a control signal PWM in the form of a pulse width modulation signal having a local dimming value of 0% to 100% to the driver DIC.

The driver DIC outputs the gate signal GT based on the control signal PWM supplied from the dimming controller DIM to drive the driving element DR. The driving unit DIC may receive a feedback signal FB from a node connected between the driving device DR and the passive device Rs to control the current flowing through the driving device DR. Meanwhile, the dimming controller DIM and the driver DIC may be integrated into one unit according to the configuration of the device.

The driving device DR may control the brightness of the backlight unit BLU by controlling the power (for example, current) supplied from the power supply PWR based on the gate signal GT supplied from the driver DIC.

The backlight unit BLU includes a light source unit LS including a plurality of light sources D1 to Dn arranged in series, and a compensation unit CP positioned between the plurality of light sources D1 to Dn. The position of the compensator CP is not limited to that shown, and may be located anywhere within the plurality of light sources D1 to Dn, and may be located at one or more places. In addition, the resistor RP, which is a compensating unit, may be configured in consideration of variations in the voltage characteristics Vf and the current characteristics If of the light source units LS1 to LSn. The compensator CP includes a load having the same resistance component as the light sources included in the plurality of light sources D1 to Dn.

As shown in FIG. 5, the compensator CP may include a resistor RP having the same resistance component as that of the light sources included in the plurality of light sources D1 to Dn. Any device capable of exhibiting the same resistance component as the included light source is not limited thereto.

Hereinafter, another embodiment will be described with an example that the compensator CP is a resistor RP.

6 to 8 are some block diagrams of the backlight unit according to another embodiment of the present invention.

As illustrated in FIGS. 6 to 8, the backlight unit BLU may include a plurality of light source units LS1 to LSn in which a plurality of light sources D1 to Dn arranged in series are connected in parallel. The resistor RP, which is a compensation unit, may be included in the first light source unit LS1, which is one of the plurality of light source units LS1 to LSn, as illustrated in FIG. 6. In addition, the resistor RP, which is a compensation unit, may be included in the second light source unit LS2 and the nth light source unit LSn, which are two of the plurality of light source units LS1 to LSn, as shown in FIG. 7. In addition, the resistor RP, which is a compensation unit, may be included in all of the plurality of light source units LS1 to LSn, that is, the first light source unit LS1, the second light source unit LS2, and the nth light source unit LSn as shown in FIG. 8. . The location of the resistor RP, which is a compensation unit, is not limited to the illustrated one, and may be located anywhere in the plurality of light sources D1 to Dn, and may be located in one or more places. In addition, the resistor RP, which is a compensating unit, may be configured in consideration of variations in the voltage characteristics Vf and the current characteristics If of the light source units LS1 to LSn.

6 to 8, the anode terminal AE, which is one terminal of the plurality of light source units LS1 to LSn, is commonly connected, and the cathode terminals CE1 to CEn, which are the other terminals of the plurality of light source units LS1 to LSn, are connected to each other. It may correspond to the number of light source parts. 6 to 8, the anode terminal AE is adjacent to the power supply unit PWR for supplying power to the plurality of light source units LS1 to LSn, and the cathode terminals CE1 to FIG. The CEn may be adjacent to the driving element DR for driving the plurality of light sources LS1 to LSn. In such a structure, the first light source part LS1, the second light source part LS2, and the n-th light source part LSn may require a corresponding number of driving elements, but is not limited thereto.

Meanwhile, in the present invention, as shown in Table 1, a comparative example consisting of three light source units including eight LEDs and an embodiment consisting of three light source units replacing at least one of the eight LEDs with a resistor were compared.

Light source Number of light sources (Ea) Number of compensators (Ea)
Comparative example
First Light Source 8 0 Second Light Source 8 0 Third Light Source 8 0
Experimental Example 1
First Light Source 8 0 Second Light Source 7 One Third Light Source 7 One
Experimental Example 2
First Light Source 8 0 Second Light Source 6 2 Third Light Source 6 2

As shown in Table 1, in Experimental Example 1, the number of light sources included in the second light source part and the third light source part was 7 and the number of compensation parts was 1, resulting in normal light emission. The number of dogs could be reduced while showing similar or identical luminance. In addition, in Experimental Example 2, the number of light sources included in the second light source part and the third light source part was 6, and the number of compensator parts was 2, which resulted in normal light emission. Brightness could be indicated.

As can be seen in Table 1 above, the present invention can be configured to the desired number of light sources, it can be seen that it is possible to prevent the decrease in efficiency and the price increase due to unnecessary insertion of the light source.

As described above, the present invention configures the number of light sources included in the backlight unit to satisfy the brightness and specification and prevent unnecessary insertion of the light source, thereby improving the efficiency of the light source and reducing the hot spot appearing in a specific area. There is an effect of providing a backlight unit and a liquid crystal display device using the same.

While the present invention has been described in connection with what is presently considered to be practical exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood that the invention may be practiced. Therefore, the embodiments described above are to be understood as illustrative and not restrictive in all aspects. In addition, the scope of the present invention is shown by the claims below, rather than the above detailed description. Also, it is to be construed that all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts are included in the scope of the present invention.

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention.

2 is a block diagram of a gate driver.

3 is a block diagram of a data driver;

4 is a partial block diagram of a liquid crystal display according to an exemplary embodiment of the present invention.

5 is a partial block diagram of a backlight unit according to an embodiment of the present invention.

6 to 8 are some block diagrams of a backlight unit according to another embodiment of the present invention.

<Explanation of symbols on main parts of the drawings>

TCN: timing driver PNL: liquid crystal panel

SDRV: Gate driver DDRV: Data driver

BLU: Backlight Unit BDRV: Backlight Unit Driver

PWR: Power Supply DIM: Dimming Control

DIC: drive unit DR: drive element

Claims (10)

A liquid crystal panel; And And a backlight unit which provides light to the liquid crystal panel and includes a light source unit including a plurality of light sources arranged in series and a compensation unit positioned between the plurality of light sources. The method of claim 1, The compensation unit, And a load having the same resistance component as the light sources included in the plurality of light sources. The method of claim 1, The compensation unit, And a resistor having the same resistance component as that of the light sources included in the plurality of light sources. The method of claim 1, The backlight unit, Liquid crystal display device comprising a plurality of light source unit connected in parallel. 5. The method of claim 4, The compensation unit, And at least one light source unit among the plurality of light source units. 5. The method of claim 4, One terminal of the plurality of light source units is connected in common, and the other terminal of the plurality of light source units corresponds to the number of the plurality of light source units. 5. The method of claim 4, And one terminal of the plurality of light source units is adjacent to a power supply unit for supplying power to the plurality of light source units, and the other terminal of the plurality of light source units is adjacent to a driving element for driving the plurality of light source units. The method of claim 1, The plurality of light sources, Liquid crystal display comprising a light emitting diode. A power supply unit; A driving element controlling the power output from the power supply unit; A plurality of light sources connected in parallel with a plurality of light sources arranged in series between the power supply unit and the driving element; And A backlight unit comprising a compensation unit located between the plurality of light sources. 10. The method of claim 9, The compensation unit, The backlight unit, characterized in that the load having the same resistance component as the light source included in the plurality of light sources.

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