KR20100027895A - Liquid crystal display and control method thereof - Google Patents

Abstract

PURPOSE: A liquid crystal display and a control method thereof are provided to reduce the number of photo-sensor and simplify a control algorithm by compensating a white color coordinate on the CIE1931 color coordinate. CONSTITUTION: A backlight unit of a liquid crystal display includes a backlight(153), a backlight driving unit(152), a light sensing unit(154), and a back light control unit(151). The backlight radiates white light to a liquid crystal panel by including a plurality of R LEDs, G LEDs, and B LEDs. The backlight driving unit drives LEDs by including a R LED driving part(152a), a G LED driving part(152b), and B LED driving part(152c). The light sensing unit senses R color amount information and B color amount information included in the white light.

Description

Liquid Crystal Display And Control Method Thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device and a control method thereof capable of compensating for variations in white color coordinates and luminance variations thereof.

In general, the liquid crystal display (LCD) has a tendency that its application range is gradually getting wider due to features such as light weight, thinness, and low power consumption. In accordance with this trend, liquid crystal displays have been applied to office automation equipment, audio / video equipment, and the like. The liquid crystal display device displays a desired image on a screen by adjusting the amount of light beams transmitted in accordance with an image signal applied to a plurality of control switches arranged in a matrix.

Since the liquid crystal display device is not a self-luminous display device, a backlight unit for generating light in the form of a surface light source is required. Typically, the backlight unit includes a backlight such as a lamp or a light emitting diode (LED). LEDs are compact and can efficiently emit light of vivid color, have excellent characteristics of initial driving characteristics and shock resistance, and are strong in repetition of lighting / lighting off. Therefore, in recent years, many attempts have been made to construct a white light source using LEDs, and in particular, RGB LEDs having monochromatic peak wavelengths are disposed in close proximity, and light generated through them is diffused and mixed to obtain white light. Here, since the peak wavelengths of the RGB LEDs are different from each other, instead of applying the same operating current, a control method of differently applying the operating current and the pulse width modulation (PWM) duty ratio for each RGB LED is mainly used.

Even though the backlight is controlled through this control method, the white color color coordinate is changed due to the change in luminescence intensity and peak wavelength due to the change of time and ambient temperature for each RGB LED due to the characteristics of the RGB LED which is a semiconductor device. In order to solve this problem, the amount of RGB LED generated from the backlight is sensed using a separate R photosensor, G photosensor and B photosensor, and the detected values are compared with previously stored white target color coordinate values and white luminance values. Afterwards, a method of controlling the PWM duty ratio of each RGB LED by the amount of error according to the comparison result has been proposed.

However, the method of compensating for the fluctuation of the white target color coordinate value and the luminance value caused by the change over time and the ambient temperature changes requires both an R photosensor, a G photosensor and a B photosensor for each RGB LED. In addition to increasing the manufacturing cost, the PWM duty ratio must be controlled differently for each of the RGB LEDs based on the sensed optical signals, leading to the complexity of the control algorithm and the size of the control device.

Accordingly, an object of the present invention is to compensate for fluctuations in white target color coordinate values and luminance values caused by changes over time and ambient temperature, while reducing the number of photosensors used for light sensing and simplifying a control algorithm for compensation. The present invention provides a liquid crystal display device and a control method thereof.

In order to achieve the above object, the liquid crystal display device according to the first embodiment of the present invention comprises a liquid crystal panel; A backlight for irradiating white light to the liquid crystal panel including a plurality of R LEDs, a plurality of G LEDs, and a plurality of B LEDs; A backlight driver for driving the LEDs, including an R LED driver, a G LED driver, and a B LED driver; An optical sensing unit configured to sense R color amount information and B color amount information included in the white light; And comparing the sensed R color quantity information and B color quantity information with respective pre-stored R color quantity optimal information and B color quantity optimal information for each temperature, and then calculating a compensation control signal for compensating an error amount according to the comparison. And a backlight control unit for calculating the LED and the B LED and applying the R LED driver and the B LED driver, respectively.

The liquid crystal display further includes a temperature sensor for sensing temperature of the liquid crystal panel or the backlight and generating temperature information.

The backlight controller may include: a target information storage unit configured to store optimal R color amount information and optimal B color amount information for each temperature; A sensing information storage unit for storing the sensed R color quantity information and B color quantity information; After reading the R color quantity optimal information and the B color quantity optimal information for the temperature using the temperature information as a read address, the sensing information storage unit stores the read R color quantity optimal information and the optimal B color quantity optimal information, respectively. Comparing unit for calculating the error amount information due to changes over time and ambient temperature by comparing the R color amount sensing information and B color amount information from the; An algorithm processor configured to calculate a compensation value by executing a built-in algorithm to compensate for a difference value included in the error amount information input; And a control signal generator configured to generate a first compensation control signal for controlling the R LED and a second compensation control signal for controlling the B LED based on the compensation value.

The first compensation control signal is for adjusting at least one of a PWM duty ratio of the R LED and a driving current amplitude of the R LED; The second compensation control signal is for adjusting at least one of the PWM duty ratio of the B LED and the driving current amplitude of the B LED.

The G LED driver drives the G LEDs with at least one of a fixed PWM duty ratio and a fixed driving current amplitude.

According to a second exemplary embodiment of the present invention, a liquid crystal display device includes: a liquid crystal panel; A backlight for irradiating white light to the liquid crystal panel including a plurality of R LEDs, a G fluorescent film, and a plurality of B LEDs; A backlight driver for driving the LEDs, including an R LED driver and a B LED driver; An optical sensing unit configured to sense R color amount information and B color amount information included in the white light; And comparing the sensed R color quantity information and B color quantity information with respective pre-stored R color quantity optimal information and B color quantity optimal information for each temperature, and then calculating a compensation control signal for compensating an error amount according to the comparison. It is provided with a backlight control unit for calculating the LED and the B LED applied to the R LED driver and the B LED driver, respectively.

According to the first embodiment of the present invention, a liquid crystal panel, a backlight including a plurality of R LEDs, a plurality of G LEDs, and a plurality of B LEDs to irradiate the liquid crystal panel with white light, an R LED driver, a G LED driver, and a B A control method of a liquid crystal display device having a backlight driver for driving the LEDs, including an LED driver, includes: sensing R color amount information and B color amount information included in the white light; And comparing the sensed R color quantity information and B color quantity information with respective pre-stored R color quantity optimal information and B color quantity optimal information for each temperature, and then calculating a compensation control signal for compensating an error amount according to the comparison. And calculating the LED and the B LED and applying the R LED driver and the B LED driver, respectively.

According to a second embodiment of the present invention, a liquid crystal panel includes a plurality of R LEDs, a G fluorescent film, and a plurality of B LEDs, and a backlight for irradiating white light to the liquid crystal panel, including an R LED driver and a B LED driver. A control method of a liquid crystal display device having a backlight driver for driving the LEDs,

Sensing R color amount information and B color amount information included in the white light; And

After comparing the sensed R color quantity information and B color quantity information with the pre-stored R color quantity optimal information and B color quantity optimal information for each temperature, a compensation control signal for compensating for the error amount according to the comparison is applied to the R LED. And calculating each of the LEDs and applying them to the R LED driver and the B LED driver, respectively.

According to the present invention, a liquid crystal display and a control method thereof detect only R color and B color among three colors of R, G, and B to correct white color color coordinates on CIE1931 color coordinates, thereby reducing the number of photosensors used for optical sensing. In addition, by simplifying the control algorithm for compensation can greatly contribute to the integration of the control device.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 1 to 9.

1 shows a liquid crystal display according to an embodiment of the present invention.

Referring to FIG. 1, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal panel 11, a data driving circuit 12, a gate driving circuit 13, a timing controller 14, and a backlight unit 15. do.

In the liquid crystal panel 11, a liquid crystal layer is formed between two glass substrates. The liquid crystal panel includes m × n liquid crystal cells Clc arranged in a matrix by a cross structure of m data lines DL and n gate lines GL.

Data lines DL, gate lines GL, TFTs, and a storage capacitor Cst are formed on the lower glass substrate of the liquid crystal panel 11. The liquid crystal cells Clc are connected to the TFT and are driven by an electric field between the pixel electrodes 1 and the common electrode 2. The black matrix, the color filter, and the common electrode 2 are formed on the upper glass substrate of the liquid crystal panel 11. The common electrode 2 is formed on the upper glass substrate in a vertical electric field driving method such as twisted nematic (TN) mode and vertical alignment (VA) mode, and is formed in IPS (In Plane Switching) mode and FFS (Fringe Field Switching) mode. In the same horizontal electric field driving method, the pixel electrode 1 is formed on the lower glass substrate. A polarizing plate is attached to each of the upper glass substrate and the lower glass substrate of the liquid crystal panel 11, and an alignment layer for setting the pre-tilt angle of the liquid crystal is formed.

The data driving circuit 12 refers to the digital video data RGB in response to the data control signal DDC from the timing controller 14 to the gamma reference voltages GMA from the gamma reference voltage generator (not shown). The analog gamma compensation voltage is converted into the analog gamma compensation voltage, and the analog gamma compensation voltage is supplied to the data lines DL of the liquid crystal panel 11 as a data voltage.

The gate driving circuit 13 sequentially supplies scan pulses for selecting the horizontal line of the liquid crystal panel 11 to which the data voltage is supplied to the gate lines GL.

The timing controller 14 receives timing signals such as horizontal and vertical synchronization signals (Hsync, Vsync), data enable signals (Data Enable, DE), and dot clock (DCLK) from a system board (not shown). 12 and control signals GDC and DDC for controlling the operation timing of the gate driving circuit 13. The data timing control signal DDC for controlling the operation timing of the data driving circuit 12 instructs the latch operation of the digital data in the data driving circuit 12 on the basis of the rising or falling edge. A source sampling clock (SSC), a source output enable signal SOE indicating the output of the data driving circuit 12, and a data voltage to be supplied to the liquid crystal cells Clc of the liquid crystal panel 11. And a polarity control signal POL indicating the polarity of the signal. The gate timing control signal GDC for controlling the operation timing of the gate driving circuit 13 is a gate start pulse (GSP) indicating a starting horizontal line at which scanning starts in one vertical period in which one screen is displayed. Is a timing control signal input to the shift register in the gate driving circuit 13 to sequentially shift the gate start pulse GSP. The gate shift clock signal Gate is generated with a pulse width corresponding to the ON period of the TFT. Shift Clock: GSC), and a Gate Output Enable Signal (GOE) indicating the output of the gate driving circuit 13.

In addition, the timing controller 14 realigns the digital video data RGB input from the system board to the data driving circuit 12 in accordance with the resolution of the liquid crystal panel 11.

The backlight unit 15 according to an embodiment irradiates white light to the liquid crystal panel 11 including a plurality of R LEDs, a plurality of G LEDs, and a plurality of B LEDs. The backlight unit 15 senses the light amount of the R LED and the B LED irradiated to the liquid crystal panel 11, compares the sensed value with previously stored white target color coordinate values and white luminance values, and then calculates an error amount according to the comparison result. By controlling the PWM duty ratio and / or driving current amplitude of each of the R LED and the B LED in real time, the color coordinates of the white color due to changes over time and ambient temperature are prevented. In this case, the G LED is driven with a fixed PWM duty ratio and / or a fixed drive current amplitude that is initially set regardless of the change over time and the ambient temperature.

The backlight unit 15 according to another embodiment includes a plurality of R LEDs, a G phosphor film, and a plurality of B LEDs to irradiate white light to the liquid crystal panel 11. The backlight unit 15 senses the light amount of the R LED and the B LED irradiated to the liquid crystal panel 11, compares the sensed value with previously stored white target color coordinate values and white luminance values, and then calculates an error amount according to the comparison result. By controlling the PWM duty ratio and / or drive current amplitude of each of the R LEDs and the B LEDs in real time, the color coordinates of the white color due to changes over time and ambient temperature are prevented. In this case, the G fluorescent film is excited by photon generated from the B LED to generate a green fluorescent color, and only its luminous intensity varies according to the amount of light from the B LED.

As such, the reason why the white color color coordinates can be corrected on the CIE1931 color coordinates by sensing only two colors (R color and B color) while fixing the G color among the three colors R, G, and B is due to changes in time and ambient temperature. This is because the variation is relatively small in G color. This will be described in detail below.

2 is a graph showing a change in dominant wavelength for each color according to ambient temperature, and FIG. 3 is a graph showing a result for changing luminescence (Luminous Intensity) for each color according to ambient temperature.

Referring to FIG. 2, the dominant wavelength variation of each color according to the ambient temperature shows that the R color shows the largest change, while the G color shows the smallest. In addition, referring to FIG. 3, the result of changing the color intensity (Luminous Intensity) according to the ambient temperature, it can be seen that the R color shows the greatest amount of change while the G color shows the smallest amount of change. These results have important implications. That is, if the G color amount can be assumed as a constant, a hint is obtained that the desired color point control is possible even with only the physical amount sensed of the other two colors (R color and B color).

4 is a graph showing a change in chromaticity coordinates with time, and FIG. 5 is a graph showing a change in chromaticity coordinates with changes in ambient temperature.

Referring to FIG. 4, the effect of the change over time on the color coordinates of CIE1931 can be seen that the change in chromaticity coordinates is Δx = 0.0125 and Δy = 0.005 between the initial stage of aging and 30 minutes after aging. Here, Δx largely depends on the amount of change in the R color and B color, while Δy greatly depends on the amount of change in the G color. As can be seen from the fact that the change in Δy is relatively small compared to Δx, the G color contributes little to the change in chromaticity coordinates with time. In addition, referring to FIG. 5, the effect of ambient temperature on the CIE1931 color coordinates can be seen that the change in Δy is relatively small compared to Δx. In particular, it can be seen that the variation in Δy is distributed within only 0.003 at -20 ° C to 25 ° C. As can be seen from this, the G color contributes little to the change in chromaticity coordinates according to the change of ambient temperature.

As described, it was confirmed that Δy of the G dominant axis is relatively small in comparison with other colors. That is, the G color can be assumed to be a constant, and it can be concluded that the white color color coordinate can be corrected even by controlling only the R color and the B color.

6A and 6B show one method of controlling the white color under consideration that the peak wavelength of the G color is constant.

The white color control method considers the peak wavelength of the G color to be constant. Meaning that the peak wavelength of the G color is constant means that the G LED monochromatic light is used but its duty ratio is fixed (first embodiment) or that the G fluorescent film is used and its luminance (Luminous Intensity) is determined by the amount of light from the B LED. It can be interpreted as meaning that it is variable according to (2nd Example).

In the white color control method, when the peak wavelength of the G color is fixed at 525 nm and the driving current of the B LED is changed, the first axis (ax1) connected to the peak wavelength of the G color and the peak wavelength of the B color are connected as shown in FIG. 6A. The white color coordinate point P is located at any point between the two axes ax2. In other words, when the peak wavelengths of the G color and the B color are determined, the position range of the white color coordinate point P is determined, and the white color coordinate point P is positioned on the first and second axes ax1 and ax2. It can be determined only by the drive current level (on time period or amplitude) of the B LED. That is, if the white color coordinate point (P) is located close to the primary color of B by increasing the driving current of the B LED, white light realized through color mixing becomes blueish, while reducing the size of the driving current of the B LED. Positioning the white color coordinate point P close to the primary color of G color results in greenish white light realized through color mixing. The white color coordinate point P thus determined is located on one axis with the third axis ax3 connected to the R peak wavelength as shown in FIG. 6B, and where the white color coordinate point P is placed is a driving current level applied to the R LED. (On time duration or amplitude).

Using the above concept, embodiments of the backlight unit 15 that senses only two colors (R color and B color) among the three colors R, G, and B and corrects the white color color coordinate on the CIE1931 color coordinate will be described as follows. .

First of the backlight unit 15 Example

7 shows a backlight unit 15 according to a first embodiment of the present invention.

Referring to FIG. 7, the backlight unit 15 according to the first embodiment of the present invention includes a backlight controller 151, a backlight driver 152, a backlight 153, a light sensor 154, and a temperature sensor 155. It is provided.

The backlight 153 includes an R LED string 153a having a plurality of R LEDs connected in series, a G LED string 153b having a plurality of G LEDs connected in series, and a B LED string 153c having a plurality of B LEDs connected in series. White light is irradiated to the liquid crystal panel 11 including the.

The backlight driver 152 includes an R LED driver 152a, a G LED driver 152b, and a B LED driver 152c. The R LED driver 152a generates the R LED driving current level (on time period or amplitude) differently according to the change over time and the ambient temperature to drive the R LED string 153a. The B LED driver 152c generates the B LED driving current level (on time period or amplitude) differently according to the change over time and the ambient temperature to drive the B LED string 153c. On the other hand, the G LED driver 152b drives the G LED string 153b with the G LED driving current level (on time period or amplitude) initially set regardless of the change over time and the ambient temperature.

The light sensing unit 154 includes an R photo sensor 154a and a B photo sensor 154c to sense an R color and a B color of white light generated from the backlight 153. The sensed R color amount and B color amount are applied to the backlight controller 151.

The temperature sensor 155 senses the temperature of the backlight 153 or the liquid crystal panel 11 and applies the sensed temperature value to the backlight controller 151. The temperature sensor 155 may be implemented by a known thermistor.

The backlight controller 151 includes a control signal generator 151a, an algorithm processor 151b, a comparator 151c, a target information storage unit 151d, and a sensing information storage unit 151e. The variable R control signal CS_R_variable and the variable B control signal CS_B_variable are adjusted according to the change. In addition, the backlight controller 151 generates a fixed G control signal CS_G_fixed that is maintained at an initial set value regardless of changes over time and ambient temperature.

The target information storage unit 151d stores the optimum R color amount information and the optimal B color amount information for each temperature so as to realize white light having an optimal white target color coordinate value and white luminance value in response to changes over time and ambient temperature. . The optimal R color information and the optimal B color information by temperature are stored in the form of a lookup table in advance through an iterative experiment.

The sensing information storage unit 151e stores the R color amount information and the B color amount information sensed by the light sensing unit 154.

The comparator 151c reads the optimum R color amount information and the optimum B color amount information for the temperature from the target information storage unit 151d using the temperature information Temp from the temperature sensor 155 as the lead address. Then, the comparison unit 151c compares the readout R color quantity optimal information and the optimal B color quantity optimal information with the R color quantity sensing information and the B color quantity information from the sensing information storage unit 151e, respectively. Error information due to temperature change is calculated.

The algorithm processing unit 151b receives the error amount information Error from the comparator 151c, and executes an embedded algorithm to compensate for the difference value included in the error amount information Error, so that each of the R LED and the B LED is performed. Compute the PWM duty value of and / or the drive current amplitude of each of the R LED and B LED.

The control signal generator 151a generates a variable R control signal CS_R_variable based on the PWM duty value and / or drive current amplitude value of the R LED from the algorithm processor 151b. The variable R control signal CS_R_variable is for controlling the PWM duty ratio and / or driving current amplitude of the R LED and is applied to the R LED driver 152a. In addition, the control signal generator 151a generates a variable B control signal CS_B_variable based on the PWM duty value and / or the drive current amplitude value of the B LED from the algorithm processor 151b. The variable B control signal CS_B_variable is for controlling the PWM duty ratio and / or driving current amplitude of the B LED and is applied to the B LED driver 152c. The control signal generator 151a generates a fixed G control signal CS_G_fixed to a predetermined initial value and applies it to the G LED driver 152b.

As described above, the backlight unit 15 according to the first embodiment of the present invention senses only the R color and the B color among the three colors R, G, and B, and corrects the white color color coordinates on the CIE1931 color coordinates, thereby making it possible to use the light. In addition to reducing the number of sensors and simplifying the control algorithm for compensation, it can greatly contribute to the integration of the control device. The backlight unit 15 according to the first exemplary embodiment of the present invention arranges LEDs on the outer side of the liquid crystal panel 11 and injects light from the light source to the entire surface of the liquid crystal panel 11 using a transparent light guide plate. It is applicable to both the edge type system to which it is made, and the direct type system which arrange | positions a light source on the back surface of a liquid crystal panel, and directly illuminates the whole surface of a liquid crystal panel.

Second of the backlight unit 15 Example

8 shows a backlight unit 15 according to a second embodiment of the present invention.

Referring to FIG. 8, the backlight unit 15 according to the second embodiment of the present invention may include a backlight controller 251, a backlight driver 252, a backlight 253, a light sensor 254, and a temperature sensor 255. It is provided.

The backlight 253 includes an R LED string 253a having a plurality of R LEDs connected in series, a B LED string 253c having a plurality of B LEDs connected in series, and a G phosphor film disposed on these 253a, 253c. White light is irradiated onto the liquid crystal panel 11, including the 253b. The G fluorescent film 253b may be formed in a single package together with an LED chip including a plurality of R LEDs and B LEDs, as shown in FIG. 9. The G fluorescent layer 253b is excited by photons generated from the B LEDs to generate green fluorescent color. The luminous intensity is determined according to the amount of light from the B LEDs. In FIG. 9, polyphthalamide (PPA) serves as a support frame for constructing an LED package, and has a reinforced plastic material to increase durability. The lead frame serves as a lead that connects the LED chip to the drive circuit and a frame that fixes the LED package to the electronic circuit board. The plating wire (Au Wire) serves to electrically connect the lead frame and the LED chip, and the adhesive member serves to fix the LED chip to the lead frame. Meanwhile, the G fluorescent film 253b is not formed as a single package together with the LED chip, but is attached to a light guide plate (edge type) surface or a diffusion plate (edge type or direct type) surface separately from the LED chip. Can be formed.

The backlight driver 252 includes an R LED driver 252a and a B LED driver 252c. The R LED driver 252a generates the R LED driving current level (on time period or amplitude) differently according to the change over time and the ambient temperature to drive the R LED string 253a. The B LED driver 252c generates the B LED driving current level (on time period or amplitude) differently according to the change over time and the ambient temperature to drive the B LED string 253c.

The light sensing unit 254 includes an R photo sensor 254a and a B photo sensor 254c to sense an R color and a B color of white light generated from the backlight 253. The sensed R color amount and B color amount are applied to the backlight controller 251.

The temperature sensor 255 senses the temperature of the backlight 253 or the liquid crystal panel 11, and applies the sensed temperature value to the backlight controller 251. The temperature sensor 255 may be implemented by a known thermistor.

The backlight controller 251 includes a control signal generator 251a, an algorithm processor 251b, a comparator 251c, a target information storage unit 251d, and a sensing information storage unit 251e. The variable R control signal CS_R_variable and the variable B control signal CS_B_variable are adjusted according to the change.

The target information storage unit 251 d stores the optimum R color amount information and the optimum B color amount information for each temperature so as to realize white light having an optimal white target color coordinate value and white luminance value in response to changes over time and ambient temperature. . The optimal R color quantity information and the optimal B color quantity information for each temperature are stored in the form of a lookup table in advance through an iterative experiment.

The sensing information storage unit 251e stores the R color amount information and the B color amount information sensed by the light sensing unit 254.

The comparator 251c reads the optimal R color amount information and the optimal B color amount information for the temperature from the target information storage unit 251d using the temperature information Temp from the temperature sensor 255 as the read address. Then, the comparison unit 251c compares the readout R color quantity optimal information and the optimal B color quantity optimal information with the R color quantity sensing information and the B color quantity information from the sensing information storage unit 251e, respectively. Error information due to temperature change is calculated.

The algorithm processing unit 251b receives the error amount information Error from the comparator 251c and executes a built-in algorithm to compensate for the difference value included in the error amount information Error. Compute the PWM duty value of and / or the drive current amplitude of each of the R LED and B LED.

The control signal generator 251a generates a variable R control signal CS_R_variable based on the PWM duty value and / or drive current amplitude value of the R LED from the algorithm processor 251b. The variable R control signal CS_R_variable is for controlling the PWM duty ratio and / or driving current amplitude of the R LED and is applied to the R LED driver 252a. In addition, the control signal generator 251a generates a variable B control signal CS_B_variable based on the PWM duty value and / or the drive current amplitude value of the B LED from the algorithm processor 251b. The variable B control signal CS_B_variable is for controlling the PWM duty ratio and / or driving current amplitude of the B LED and is applied to the B LED driver 252c.

As described above, the backlight unit 15 according to the second embodiment of the present invention senses only the R color and the B color among the three colors R, G, and B, and corrects the white color color coordinates on the CIE1931 color coordinates, thereby making the photo used for light sensing. In addition to reducing the number of sensors and simplifying the control algorithm for compensation, it can greatly contribute to the integration of the control device. The backlight unit 15 according to the second exemplary embodiment of the present invention arranges LEDs on the outer side of the liquid crystal panel 11 and injects light from the light source to the entire surface of the liquid crystal panel 11 using a transparent light guide plate. It can be applied to both an edge type system to make a light source and a direct type method of directly dimming the entire surface of the liquid crystal panel by arranging a light source on the rear surface of the liquid crystal panel.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

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

Figure 2 is a graph showing the change in dominant wavelength (Dominant Wavelength) for each color according to the ambient temperature.

Figure 3 is a graph showing the results of changes in color (Luminous Intensity) according to the ambient temperature.

Figure 4 is a graph showing the change in chromaticity coordinates over time.

5 is a graph showing a change in chromaticity coordinates according to a change in ambient temperature.

6A and 6B show sequentially one method of controlling the white color under consideration that the peak wavelength of the G color is constant.

7 is a block diagram illustrating a backlight unit according to a first embodiment of the present invention.

8 is a block diagram illustrating a backlight unit according to a second exemplary embodiment of the present invention.

9 shows an LED package including a G fluorescent film.

<Description of Symbols for Main Parts of Drawings>

11 liquid crystal panel 12 data driving circuit

13 gate driving circuit 14 timing controller

15: backlight unit 151 251: backlight control unit

152,252: backlight driver 153,253: backlight

154,254: light sensing unit 155,255: temperature sensor

Claims (13)

A liquid crystal panel; A backlight for irradiating white light to the liquid crystal panel including a plurality of R LEDs, a plurality of G LEDs, and a plurality of B LEDs; A backlight driver for driving the LEDs, including an R LED driver, a G LED driver, and a B LED driver; An optical sensing unit configured to sense R color amount information and B color amount information included in the white light; And After comparing the sensed R color quantity information and B color quantity information with the pre-stored R color quantity optimal information and B color quantity optimal information for each temperature, a compensation control signal for compensating for the error amount according to the comparison is applied to the R LED. And a backlight control part calculated for each B LED and applied to the R LED driver and the B LED driver, respectively. The method of claim 1, And a temperature sensor for sensing temperature of the liquid crystal panel or the backlight and generating temperature information. The method of claim 2, The backlight control unit, A target information storage unit for storing optimum R color amount information and optimal B color amount information for each temperature; A sensing information storage unit for storing the sensed R color quantity information and B color quantity information; After reading the R color quantity optimal information and the B color quantity optimal information for the temperature using the temperature information as a read address, the sensing information storage unit stores the read R color quantity optimal information and the optimal B color quantity optimal information, respectively. Comparing unit for calculating the error amount information due to changes over time and ambient temperature by comparing the R color amount sensing information and B color amount information from the; An algorithm processor configured to calculate a compensation value by executing a built-in algorithm to compensate for a difference value included in the error amount information input; And And a control signal generator configured to generate a first compensation control signal for controlling the R LED and a second compensation control signal for controlling the B LED based on the compensation value. The method of claim 3, wherein The first compensation control signal is for adjusting at least one of a PWM duty ratio of the R LED and a driving current amplitude of the R LED; And the second compensation control signal adjusts at least one of a PWM duty ratio of the B LED and a driving current amplitude of the B LED. The method of claim 1, And the G LED driver drives the G LEDs with at least one of a fixed PWM duty ratio and a fixed driving current amplitude. A liquid crystal panel; A backlight for irradiating white light to the liquid crystal panel including a plurality of R LEDs, a G fluorescent film, and a plurality of B LEDs; A backlight driver for driving the LEDs, including an R LED driver and a B LED driver; An optical sensing unit configured to sense R color amount information and B color amount information included in the white light; And After comparing the sensed R color quantity information and B color quantity information with the pre-stored R color quantity optimal information and B color quantity optimal information for each temperature, a compensation control signal for compensating for the error amount according to the comparison is applied to the R LED. And a backlight control part calculated for each B LED and applied to the R LED driver and the B LED driver, respectively. The method of claim 6, And a temperature sensor for sensing temperature of the liquid crystal panel or the backlight and generating temperature information. The method of claim 7, wherein The backlight control unit, A target information storage unit for storing optimum R color amount information and optimal B color amount information for each temperature; A sensing information storage unit for storing the sensed R color quantity information and B color quantity information; After reading the R color quantity optimal information and the B color quantity optimal information for the temperature using the temperature information as a read address, the sensing information storage unit stores the read R color quantity optimal information and the optimal B color quantity optimal information, respectively. Comparing unit for calculating the error amount information due to changes over time and ambient temperature by comparing the R color amount sensing information and B color amount information from the; An algorithm processor configured to calculate a compensation value by executing a built-in algorithm to compensate for a difference value included in the error amount information input; And And a control signal generator configured to generate a first compensation control signal for controlling the R LED and a second compensation control signal for controlling the B LED based on the compensation value. The method of claim 8, The first compensation control signal is for adjusting at least one of a PWM duty ratio of the R LED and a driving current amplitude of the R LED; And a second compensation control signal applied to the B LED driver to adjust at least one of a PWM duty ratio of the B LED and a driving current amplitude of the B LED. Back light irradiating white light to the liquid crystal panel, including a liquid crystal panel, a plurality of R LEDs, a plurality of G LEDs, and a plurality of B LEDs, and driving the LEDs including an R LED driver, a G LED driver, and a B LED driver. In the control method of the liquid crystal display device having a backlight driving unit for Sensing R color amount information and B color amount information included in the white light; And The sensed R color quantity information and B color quantity information are compared with pre-stored R color quantity optimal information and B color quantity optimal information for each temperature, and then a compensation control signal for compensating for the error amount according to the comparison is applied to the R LED. And calculating each of the B LEDs and applying the R LEDs to the R LED driver and the B LED driver, respectively. The method of claim 10, The compensation control signal is, A first compensation control signal for adjusting at least one of a PWM duty ratio of the R LED and a driving current amplitude of the R LED; And And a second compensation control signal for adjusting at least one of a PWM duty ratio of the B LED and a driving current amplitude of the B LED. A backlight for irradiating white light to the liquid crystal panel, including a liquid crystal panel, a plurality of R LEDs, a G fluorescent film, and a plurality of B LEDs, and a backlight driver for driving the LEDs, including an R LED driver and a B LED driver. In the control method of the liquid crystal display device which has, Sensing R color amount information and B color amount information included in the white light; And The sensed R color quantity information and B color quantity information are compared with pre-stored R color quantity optimal information and B color quantity optimal information for each temperature, and then a compensation control signal for compensating for the error amount according to the comparison is applied to the R LED. And calculating each of the B LEDs and applying the R LEDs to the R LED driver and the B LED driver, respectively. The method of claim 12, The compensation control signal is, A first compensation control signal for adjusting at least one of a PWM duty ratio of the R LED and a driving current amplitude of the R LED; And And a second compensation control signal for adjusting at least one of a PWM duty ratio of the B LED and a driving current amplitude of the B LED.

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