KR20020056220A - Apparatus and method for automatic brightness control of liquid crystal display - Google Patents

Abstract

PURPOSE: An apparatus and a method for automatically controlling luminance of a liquid crystal display are provided to automatically adjust duty rate for each image to perform automatic control of luminance of each image and to improve contrast. CONSTITUTION: An apparatus for automatically controlling luminance of a liquid crystal display includes a control signal generator(400) and an inverter(62). The control signal generator receives video data to be displayed on the liquid crystal display and calculates the average gray value of the video data to generate a luminance control signal in proportion to the average gray value. The inverter automatically controls luminance of a back light of the liquid crystal display in response to the luminance control signal outputted from the control signal generator. The control signal generator is a timing controller, a graphic controller or an LCD panel.

Description

Automatic brightness control device and method for liquid crystal display {APPARATUS AND METHOD FOR AUTOMATIC BRIGHTNESS CONTROL OF LIQUID CRYSTAL DISPLAY}

The present invention relates to a liquid crystal display (LCD), and more particularly to an apparatus for automatically adjusting the brightness of a liquid crystal display (LCD).

FIG. 1 is a diagram illustrating a configuration of a general TFT-LCD (Thin Film Transistor Liquid Crystal Display) module 100. Referring to FIG. 1, the LCD module 100 includes an LCD panel 10 in which liquid crystal is injected between two glasses, driving circuits 20 and 30 for driving the LCD panel 10, and A driving unit including a timing controller 40 for generating control signals for controlling these driving circuits, and a chassis structure including a backlight 60. Assemblies consisting of these are commonly referred to as TFT-LCD modules (or LCD modules), which display functions in systems such as notebook computers, televisions, and monitors. It is used as a device in charge of.

The backlight 60 is comprised of the inverter 62, the fluorescent lamp 64, the reflecting plate 66, etc., and produces the planar light with uniform brightness from the fluorescent lamp 64 used as a light source. The lamp 64 is largely classified into a Cold Cathode Fluorenscence Tube (CCFT) and a Hot Cathode Fluorenscence Tube (HCFT), and the reflector 66 serves to change a reflection angle of light. In addition, in response to each pixel signal voltage input from the driving circuits 20 and 30, the LCD panel 10 controls the light transmitted by the white plane light incident from the backlight 60 to the pixel. Is displayed.

FIG. 2 is a block diagram showing a brightness control scheme for the LCD module 100 when the LCD module 100 is used as a display device in a portable computer or a desktop computer. Generally, a portable computer or desktop computer system is driven with a direct current voltage, while the backlight 60 is lit with an alternating voltage. Therefore, the LCD module 100 essentially requires an inverter 62 for converting a DC voltage into an AC voltage as shown in the figure. In addition to the operation of converting such a DC voltage into an AC voltage, the inverter 62, as well known to those skilled in the art, has a dimming circuit therein (not shown). Is provided to perform the function of adjusting the brightness of the lamp (64).

Referring to FIG. 2, when a user inputs a brightness control command through a computer, the computer main body 200 generates a brightness control voltage CTL_V to the inverter 62 to adjust brightness. When the luminance control voltage CTL_V is generated from the computer main body 200, the dimmer circuit provided in the inverter 62 limits the current of the lamp 64 in response to the luminance control voltage CTL_V, thereby backlighting the backlight 60. Adjust the brightness. For example, when the computer is a portable computer, the luminance control voltage CTL_V has a value of 0-3.3V. At this time, when the luminance control voltage CTL_V is 0V, the darkest luminance (black) appears, and when the luminance control voltage CTL_V is 3.3V, the brightest luminance (white) appears.

However, such a brightness control scheme according to the related art, although the data characteristics of each screen (or frame) displayed through the LCD module 100 is different, once the brightness is adjusted once adjusted It has the characteristic of maintaining the brightness as it is. That is, the brightness control scheme according to the prior art has a disadvantage of causing unnecessary power consumption by maintaining uniform brightness even though the screen changes abruptly like the moving picture and the overall contrast varies continuously for each screen. .

Accordingly, an object of the present invention is to solve the above-described problems, and to provide an apparatus and a method capable of automatically adjusting luminance for each screen by automatically adjusting the duty rate for each screen.

Another object of the present invention is to provide an apparatus and method for preventing a collision between luminance adjustment at the request of a user and luminance adjustment for each screen which is automatically performed, and integrating the luminance adjustment methods as appropriate.

Another object of the present invention is to provide an apparatus and method for automatically adjusting brightness which can improve contrast for each screen displayed on the LCD module.

In addition, another object of the present invention is to increase the brightness only if necessary according to the characteristics of the data that each screen has, and in the other case by reducing the brightness, automatic brightness control device that can reduce the power consumption of the LCD module and To provide a method.

1 is a view for showing the configuration of a general LCD module;

2 is a block diagram illustrating a brightness control scheme according to the prior art for an LCD module;

3 is a block diagram showing a backlight brightness control scheme of an LCD module according to a first embodiment of the present invention;

4 is a view for showing the waveform of the luminance control voltage output by the duty controller and the R-C circuit shown in FIG.

FIG. 5 is a diagram illustrating a current and a luminance relationship of a lamp linearly determined according to a luminance control voltage output by the duty controller and the R-C circuit shown in FIG. 3; FIG.

6 is a block diagram showing a backlight brightness control scheme of an LCD module according to a second embodiment of the present invention;

FIG. 7 is a view illustrating a backlight brightness adjustment result and a contrast display result by the LCD module shown in FIG. 6;

8 is a diagram illustrating power consumption according to backlight brightness control by the LCD module shown in FIG. 6;

9 is a block diagram showing a backlight brightness control scheme of an LCD module according to a third embodiment of the present invention;

10 is a block diagram showing a backlight brightness control scheme of an LCD module according to a fourth embodiment of the present invention;

FIG. 11 is a view for showing an output waveform of each of the functional blocks shown in FIG. 10; FIG. And

12 is a flowchart illustrating a method of adjusting luminance of an LCD module according to the present invention.

* Description of the symbols for the main parts of the drawings *

10 LCD panel 20 gate driving circuit

30: source driving circuit 40, 400: timing controller

60: backlight 62: inverter

64: lamp 66: reflector

100: LCD module 200: computer main unit

420: Duty control unit 500: R-C circuit

600: merge circuit 700: level shifter

According to a feature of the present invention for achieving the object of the present invention as described above, a liquid crystal display device having a backlight, accepts the pixels to be displayed on the liquid crystal display device, calculate the average gray value of the pixels to calculate the average Control signal generating means for generating a brightness control signal proportional to the gradation value, and an inverter for automatically adjusting the brightness of the backlight in response to the brightness control signal output from the control signal generating means.

According to a feature of the present invention for achieving the other object of the present invention as described above, a liquid crystal display device having a backlight, accepts the pixels to be displayed on the liquid crystal display device, calculates the average gray value of the pixels First control signal generating means for generating a first brightness control signal proportional to an average gradation value, second control signal generating means for generating a second brightness control signal for adjusting the brightness of the backlight by a user's operation; Third control signal generation means for generating a third brightness adjustment signal in response to the first and second brightness adjustment signals output from the first and second control signal generation means, and in response to the third brightness adjustment signal; Thereby adjusting the brightness of the backlight.

According to yet another aspect of the present invention for achieving the above object of the present invention, the backlight brightness control method of the liquid crystal display device, the step of calculating the gray level of the pixel to be displayed on the liquid crystal display device, Generating a first luminance control signal corresponding to the gray scale value, and adjusting the luminance of the backlight by a third luminance control signal generated in response to the first luminance control signal and a second luminance control signal generated from the computer main body. Adjusting automatically.

(Example)

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 3 to 12.

The novel liquid crystal display device of the present invention automatically adjusts the brightness of the backlight according to the duty rate signal generated in proportion to the gradation value of the pixel to be displayed on the liquid crystal display device.

3 is a block diagram showing a backlight brightness control scheme of the LCD module according to the first embodiment of the present invention when the LCD module is used as a display device in a portable computer or a desktop computer. Referring to FIG. 3, the LCD module according to the present invention calculates an average of gray levels for one screen to be displayed on the LCD module in units of 1H time (horizontal period time) and corresponds to the calculated gray values. The timing controller 400 including the duty controller 420 for generating the duty rate signal DUTY, and the duty rate signal DUTY in units of 1H time generated from the timing controller 400 are framed. And a RC circuit 500 for generating a variable luminance control voltage Vduty whose sum varies in proportion to the gradation value of the screen to be displayed. The inverter 62 connected to the RC circuit 500 limits the current of the lamp 64 through a dimmer circuit (not shown) provided therein in response to the variable luminance control voltage Vduty, thereby providing a backlight. Adjust the brightness. Looking at the detailed operation of the LCD module as follows.

First, the timing controller 400 outputs a pulse wave of a 1H period having a duty rate corresponding to the gradation value of pixel data for 1H time. For example, in a VGA resolution LCD module with 640 horizontal pixels, if all the pixels were black for 1H, 0% is output as high as 0 pixel clocks. If the duty rate signal DUTY is generated and all the pixel values are white for 1H, 100% duty rate signal is output as high as 640 pixel clocks. (DUTY) is generated. If the average value of all the pixels is halftone during the 1H time, a 50% duty rate signal DUTY is generated.

[Table 1] and [Table 2] below show the duty rate as a percentage in the LCD module of VGA resolution having 16 average gray levels of one horizontal line and 640 horizontal pixels, and [Table 1] shows gamma constants. (gamma constant) shows the duty rate when 1, and [Table 2] shows the duty rate when the gamma constant is 2.2, which is widely adopted in current LCD products.

TABLE 1

Gradation 0 One 2 3 4 5 6 7 8 9 10 11 12 13 14 15 DUTY [%] 0 6.7 13.3 20 26.7 33.3 40.0 46.7 53.3 60.0 66.7 73.3 80.0 86.7 93.3 100 Pixel Clock [pcs] 0 43 85 128 171 213 256 299 341 384 427 469 512 555 597 640

TABLE 2

Gradation 0 One 2 3 4 5 6 7 8 9 10 11 12 13 14 15 DUTY [%] 0 0.3 1.2 2.9 5.5 8.9 13.3 18.7 25.1 32.5 41.0 50.5 61.2 73.0 85.9 100 Pixel Clock [pcs] 0 2 8 19 35 57 85 120 161 208 262 323 392 467 550 640

The duty rate shown in Tables 1 and 2 is a percentage of the number of pixels having a high level during the 1H time (horizontal period time), which is a duty rate signal generated from the timing controller 400. DUTY outputs a pulse wave having a high value by a predetermined number of pixel clocks as shown in Tables 1 and 2 according to the gray level of pixel data during 1H time.

In order to generate the duty rate signal DUTY as described above, the duty controller 420 included in the timing controller 400 includes a memory register therein, and the gradation value of the pixel data for 1H time is as follows. Calculate. For example, you can express 16 gradations.

When 4-bit pixel data is input, when the gray scale value for one horizontal line of one frame of data is obtained, the duty controller 420 first erases the memory register every 1H time (horizontal period time). Subsequently, the 4-bit pixel data is received, the input 4-bit pixel data is summed with the value stored in the storage register, and the summed result is stored in the storage register again. At this time, if the pixel data corresponding to the end of one horizontal line is not input (that is, all the pixel data of one horizontal line is not input), the 4-bit pixel until the pixel data corresponding to the end of the horizontal line is input. The above process of accepting the data continuously, adding the input 4-bit pixel data with the value stored in the storage register and storing the summed result in the storage register is repeated. If pixel data corresponding to the end of the horizontal line has been input (that is, all of the pixel data of one horizontal line has been input), the upper 4 bits of the memory register are taken to display the pixels shown in [Table 1] and [Table 2]. A duty rate signal DUTY is generated in a 1H period that outputs a high value by the number of clocks. As described above, the case of 4-bit pixel data representing 16 gray levels has been described as an example, and the above-described basic content of the duty rate adjustment may be similarly applied to 6-bit and 8-bit pixel data.

As described above, when the duty controller 420 generates a duty rate signal DUTY corresponding to the gray scale value of the 1H time unit, the RC circuit 500 generates the duty of the 1H time unit generated from the timing controller 400. The rate signal DUTY is summed over one frame. A more detailed operation of the R-C circuit 500 is as follows.

First, the initial charging voltage of the capacitor C1 is called Vo, and is a signal of a 1H period having an amplitude of Vc having a high duration time T1, that is, a high duty rate signal (D = T1 / Assuming that 1H * 100% is output from the timing controller 400, the variable luminance control voltage Vduty output from the RC circuit 500 every 1H period is defined as shown in Equation 1 below.

[Equation 1]

Vduty = {Vo + (Vc-Vo) × [1-EXP [-T1 / (R × C)]]} × EXP [(T1-1H) / (R × C)]

As such, the variable luminance control voltage Vduty for controlling the backlight luminance has a voltage level proportional to the high period T1 of the duty rate signal DUTY generated from the timing controller 400, and the variable luminance control voltage Vduty. Response time is determined by the RC time constant of the RC circuit 500.

FIG. 4 is a diagram illustrating waveforms of a variable luminance control voltage Vduty output by the duty controller 420 and the R-C circuit 500 shown in FIG. 3. Referring to FIG. 4, the graph denoted by ① represents a variable luminance control voltage (Vduty) waveform at 0-15 gray scale (DUTY is 100%) when the RC time constant is 10 times the 1H time. Denotes the variable waveform of the variable luminance control voltage (Vduty) at halftone (DUTY is 50%) when the RC time constant is 10 times the 1H time. In this case, at 50H, the variable luminance control voltage (Vduty) is in a saturation state, which means that the bit rate of 50H is directly determined by the RC time constant.

FIG. 5 is a diagram illustrating a current and luminance relationship of the lamp 64 linearly determined according to the variable luminance control voltage Vduty output by the duty controller 420 and the RC circuit 500 shown in FIG. 3. to be. Referring to FIG. 5, when the variable luminance control voltage Vduty generated from the RC circuit 500 is used as the input voltage of the backlight inverter 62, the inverter 62 is applied to the input variable luminance control voltage Vduty. The corresponding current is generated, and the brightness of the backlight is determined in proportion to the amount of current. As can be seen from this relationship, the LCD module according to the present invention automatically adjusts the duty rate for one screen to be displayed on the LCD module to generate a variable luminance control voltage (Vduty), and The current of the lamp 64 generated through the inverter 62 is adjusted by the brightness control voltage Vduty, so that the brightness of the backlight is automatically adjusted.

As described above, the LCD module according to the present invention can perform the brightness control function according to the user's request in addition to the automatic brightness adjustment function for each screen, the two brightness control can be appropriately merged without causing a collision with each other. It further includes a merging circuit. The configuration for this is as follows.

6 is a block diagram illustrating a backlight brightness control scheme of an LCD module according to a second embodiment of the present invention when the LCD module is used as a display device in a portable computer or a desktop computer. Referring to the drawings, the configuration of the LCD module shown in FIG. 6 is compared with the configuration of the LCD module shown in FIG. 3, and the duty rate signal DUTY generated from the duty controller 420 included in the timing controller 400 is included. 3 and the merge circuit 600 for generating a variable luminance control voltage Vduty in the RC circuit 500 in response to the luminance control voltage CTL_V generated from the computer main body 200. It has the same configuration as the illustrated LCD module. Therefore, in order to avoid overlapping descriptions, the same reference numerals are used for blocks performing the same function, and a detailed description thereof will be omitted.

The merge circuit 600 is connected to the timing controller 400 through a resistor R3 and is connected to a base for receiving a duty rate signal DUTY in units of 1H and an input terminal of the RC circuit 500. A first transistor T1 having an emitter and a collector for receiving the luminance control voltage from the computer main body 200, wherein the emitter of the transistor T1 has a resistance R2; Connected to ground through Here, the first transistor T1 is composed of an NPN transistor, which is only an example of a circuit configuration, and may also be formed of a circuit element such as an NMOS transistor, an operational amplifier (OP AMP), etc. according to a circuit design method. This is possible.

The transistor T1 constituting the merge circuit 600 receives the duty rate signal DUTY generated from the duty controller 420 and the luminance control voltage CTL_V from the computer main body 200, and the duty rate. When the signal DUTY is at a high level, the signal DUTY serves as a gating circuit for selectively outputting the luminance control voltage CTL_V to the RC circuit 500. The RC circuit 500 receives the luminance control voltage CTL_V selectively output from the merging circuit 600 to charge the capacitor C1 and the variable luminance control voltage Vduty by the voltage charged in the capacitor C1. Will occur). Here, the luminance control voltage CTL_V generated from the computer main body 200 may be arbitrarily set within a predetermined range by a user, and is output through the RC circuit 500 provided in the merge circuit 600. The potential of the variable luminance control voltage Vduty varies depending on the gradation value of the screen to be displayed.

For example, when the luminance control voltage CTL_V of 2V generated from the computer main body 200 is applied to the collector terminal of the first transistor T1, the merging circuit 600 is configured to provide the first transistor T1. The luminance control voltage CTL_V is output to the RC circuit 500 in response to the duty rate signal DUTY applied to the base of the signal. The RC circuit 500 charges the capacitor C1 by the luminance control voltage CTL_V, which is selectively output according to the duty rate signal DUTY, and varies the voltage of 0-2V charged in the capacitor C1. It outputs as brightness control voltage (Vduty). In addition, when the luminance control voltage CTL_V of 1 V generated from the computer main body 200 is applied to the collector terminal of the first transistor T1, the merging circuit 600 may be configured to base the first transistor T1. In response to the level of the duty rate signal DUTY applied thereto, a variable luminance control voltage Vduty between 0-1V is output through the RC circuit 500.

Here, the duty rate signal DUTY applied to the base of the first transistor T1 may be generated by the timing controller 400 as shown in the drawing, but the LCD panel may directly receive and process the pixels, or It may be generated from a graphic controller (not shown) included in the computer main body 200. Therefore, the merge circuit 600 may be mounted on the LCD panel or the computer main body 200 in addition to the inverter 62 circuit board provided in the LCD module.

FIG. 7 is a view illustrating a backlight brightness adjustment result and a contrast display result according to the LCD module illustrated in FIG. 6, and FIG. 8 illustrates power consumption according to the backlight brightness adjustment performed by the LCD module illustrated in FIG. 6. It is a figure for giving.

Referring to FIG. 7, as a result of the backlight brightness adjustment in the LCD module according to the present invention, the brightness in a dark screen such as black is lower than in the prior art, and the brightness in a bright screen such as white It becomes higher than the prior art, it can be seen that the contrast showing the contrast of black and white is significantly higher than the prior art. As a result, the contrast of black and white becomes more prominent, making the screen displayed through the LCD module more vivid.

Subsequently, referring to FIG. 8, the power consumption according to the brightness control in the LCD module according to the present invention is reduced by 2.2 W compared to the prior art. Power consumption in a mosaic pattern representing a typical screen display is reduced by 0.9 W compared to the prior art. As described above, the LCD module according to the present invention can actively adjust the luminance according to the image within the luminance control voltage range determined by the computer main body 200 by adding the merge circuit 600.

As such, the LCD module including the merge circuit 600 configured of the NPN transistor T1 may also be configured as a PNP transistor instead of the NPN transistor T1, and the circuit configuration thereof is shown in FIG. 9.

9 is a block diagram illustrating a backlight brightness control scheme of an LCD module according to a third embodiment of the present invention when the LCD module is used as a display device in a portable computer or a desktop computer. Referring to FIG. 9, the LCD module illustrated in FIG. 9 includes a merge circuit 600 ′ composed of PNP transistors instead of the merge circuit 600 composed of NPN transistors T1 when compared to the LCD module illustrated in FIG. 6. And the resistor R6 is further added to the output terminal of the RC circuit 500 ', and has the same configuration as the LCD module shown in FIG. Therefore, in order to avoid overlapping descriptions, the same reference numerals are used for blocks performing the same function, and a detailed description thereof will be omitted.

The merge circuit 600 ′ is configured to receive an luminance control voltage CTL_V from the computer main body 200 through a resistor R4 and to the timing controller 400 through a resistor R7. A second transistor T2 includes a base connected to receive a duty rate signal DUTY in units of 1H, and a collector connected to ground, and the emitter of the transistor T2 is RC. Is connected to an input of a circuit 500 '.

The transistor T2 constituting the merge circuit 600 ′ receives the duty rate signal DUTY generated from the duty controller 420 and the luminance control voltage CTL_V from the computer main body 200. When the signal DUTY is at a high level, the signal DUTY serves as a gating circuit for selectively outputting the luminance control voltage CTL_V to the RC circuit 500 '. The RC circuit 500 'receives the luminance control voltage CTL_V selectively output from the merging circuit 600', charges the capacitor C2, and varies the luminance adjustment voltage by the voltage charged in the capacitor C2. (Vduty) occurs. Here, the brightness control voltage CTL_V generated from the computer main body 200 may be arbitrarily set within a predetermined range by the user, and the variable brightness control voltage Vduty output through the RC circuit 500 '. The potential varies depending on the gradation value of the screen to be displayed. The resistor R6 connected to the output terminal of the R-C circuit 500 'divides the variable luminance control voltage Vduty output through the R-C circuit 500' by a predetermined ratio.

In the figure, the second transistor T2 is composed of a PNP transistor, which is only an example of a circuit configuration, and may be configured as a circuit element such as a PMOS transistor or an operational amplifier according to a circuit design method.

However, in the case of the LCD module having such a configuration, when the luminance control voltage CTL_V of 0V is applied from the computer main body 200, the base-emitter of the transistor T2 provided in the merging circuit 600 '. The luminance control voltage CTL_V 'of 0 V may not be applied to the RC circuit 500' by the voltage Vbe. Accordingly, a level shifter is added to the circuit as shown in FIG. 10 to remove the influence of the base-emitter voltage Vbe.

FIG. 10 is a block diagram illustrating a backlight brightness control scheme of an LCD module according to a fourth embodiment of the present invention when the LCD module is used as a display device in a portable computer or a desktop computer. Referring to FIG. 10, the LCD module illustrated in FIG. 10 is compared with the LCD module illustrated in FIG. 9 except that a level shifter 700 is added between the timing controller 400 and the merge circuit 600 ′. Has the same configuration as the LCD module shown in FIG. Therefore, in order to avoid overlapping descriptions, the same reference numerals are used for blocks performing the same function, and a detailed description thereof will be omitted.

The level shifter 700 includes an emitter connected to an input terminal of the merge circuit 600 ', a base connected to the timing controller 400 through a resistor R8, and a collector connected to a power supply voltage V _DD . A third transistor T3 of the NPN type, a resistor R9 connected at one end to the emitter, a diode D1 connected between the other end of the resistor R9 and ground, and the other end of the resistor R9; It includes a resistor (R10) connected between the turn-off voltage (Voff) terminal of the transistor.

As such, the level shifter 700 composed of the NPN transistor T3, the diode D1, and the predetermined resistors R9 and R10 includes a ground-diode (D1) -resistance (R9, R10)-thin film transistor. In the current path leading to the turn-off voltage (for example, a voltage of -5V or less), a voltage drop of the diode D1 is generated by the base-emitter voltage Vbe of the third transistor T3, and this value is changed. The emitter terminal and the resistor R9 of the third transistor T3 are provided. As a result, the transistor T2 included in the merge circuit 600 'performs a full swing, and when the 0 V luminance control voltage CTL_V is applied, the 0 V luminance control voltage CTL_V' is RC circuit 500. ') Is applied.

Referring to the operation of the LCD module having the level shifter 700 with reference to the output waveform of each node shown in FIG. 11, the duty rate signal DUTY of 0 to 3V generated from the timing controller 400 is described above. When input to the level shifter 700, when the duty rate signal DUTY is 0V, a level shift voltage Vshift of -0.6V (that is, -Vbe) is output, and the duty rate signal DUTY is 3V (that is, At the power supply voltage level V _DD ), a level shift voltage Vshift of 2.4V, which is 3V-Vbe, is output. That is, the level shifter 700 generates a level shift voltage Vshift of -0.6V (ie, -Vbe) to 2.4V (ie, 3V-Vbe) in response to a duty rate signal DUTY of 0 to 3V. do.

When the level shift voltage Vshift generated as described above is input to the merge circuit 600 'constituted of the PNP transistor T2, the variable luminance control voltage Vduty output from the RC circuit 500' is as follows. . For example, when a level shift voltage (Vshift) of -0.6 V (ie, -Vbe) is input, the potential of the emitter of the PNP transistor T2 becomes -0.6 V (-Vbe) + Vbe to adjust the luminance of 0 V. When the voltage CTL_V 'is applied to the RC circuit 500' and the level shift voltage Vshift of 2.4V is input, the PNP transistor T2 applies the luminance control voltage CTL_V 'of 3V to the RC circuit 500'. Is applied. The emitter voltage CTL_V 'of the PNP transistor T2 (that is, the luminance control voltage generated from the computer main body 200) is charged via the RC circuit 500', and then the variable luminance control voltage ( Vduty). The variable luminance control voltage Vduty is applied to the inverter 62 to adjust the luminance of the backlight. In FIG. 11, parts indicated by hatching on the emitter voltage CTL_V ′ represent the ranges of brightness control voltages that can be adjusted by the user, and the brightness of the backlight is automatically adjusted within the range.

12 is a flowchart illustrating a brightness control method of the LCD module according to the present invention. Referring to FIG. 12, in step S10, the duty controller 420 of the timing controller 400 calculates a gray scale value for each pixel data to be displayed on one screen in one line unit 1H. In operation S12, the duty controller 420 generates a duty rate signal DUTY corresponding to the gray level to the merge circuit 600. Subsequently, in step S14, the merge circuit 600 generates a variable luminance control voltage Vduty in response to the duty rate signal DUTY and the luminance control voltage generated from the computer main body 200, and the inverter 62 The brightness of the backlight is automatically adjusted by receiving the variable luminance control voltage Vduty.

As described above, the LCD module according to the present invention uses the duty rate signal DUTY generated by the duty controller 420 of the timing controller 400 and the luminance control voltage generated from the computer main body 200 by the user's setting. Merging the (CTL_V) automatically adjusts the brightness of the backlight. As a result, as shown in FIG. 7 and FIG. 8, the contrast for each screen displayed on the LCD module can be improved, thereby reducing the power consumption of the LCD module.

In the above, the configuration and operation of the circuit according to the present invention are shown in accordance with the above description and drawings, but this is merely an example, and various changes and modifications are possible without departing from the spirit of the present invention. .

According to the present invention as described above, by adjusting the duty rate for each screen automatically, the brightness adjustment for each screen can be performed automatically.

In addition, it is possible to prevent a collision between the brightness adjustment at the request of the user and the brightness adjustment for each screen which is automatically performed, and merge the brightness adjustment methods as appropriate.

In addition, the contrast of each screen displayed on the LCD module can be improved, and the power consumption of the LCD module can be reduced.

Claims (13)

In a liquid crystal display with a backlight: Control signal generating means for receiving image data to be displayed on said liquid crystal display device, calculating an average gradation value of said image data, and generating a brightness adjustment signal proportional to said average gradation value; And And an inverter for automatically adjusting the brightness of the backlight in response to the brightness control signal output from the control signal generating means. The method of claim 1, And the control signal generating means is any one of a timing controller, a graphic controller, and an LCD panel. In a liquid crystal display with a backlight: First control signal generating means for receiving image data to be displayed on said liquid crystal display device, calculating an average gradation value of said image data, and generating a first luminance control signal proportional to said average gradation value; Second control signal generating means for generating a second brightness control signal for adjusting the brightness of the backlight by a user's operation; Third control signal generation means for generating a third brightness adjustment signal in response to the first and second brightness adjustment signals output from the first and second control signal generation means; And And an inverter for adjusting the brightness of the backlight in response to the third brightness control signal. The method of claim 3, wherein And the first control signal generating means is any one of a timing controller, a graphic controller, and an LCD panel, and the second control signal generating means is a computer. The method of claim 3, wherein The third control signal generating means, A gating circuit for selectively outputting the second luminance control signal generated from the second control signal generating means while the first luminance control signal generated from the first control signal generating means is at a high level; And And an R-C circuit for generating the third luminance control signal by adding a voltage of the second luminance control signal selectively output from the gating circuit. The method of claim 5, The R-C circuit, A resistor connected between the first control signal generating means and the inverter; And a capacitor connected between the resistor and the ground. The method of claim 5, The gating circuit, One end is connected to the first control signal generating means through a first resistor, the other end is connected to the second control signal generating means, and the other end includes a transistor connected to the ground terminal through the second resistor. Automatic brightness control device for the liquid crystal display device. The method of claim 7, wherein And the transistor is one of an N-type transistor and a P-type transistor. The method of claim 7, wherein And the transistor is replaceable with a circuit element such as an operational amplifier. The method of claim 8, The liquid crystal display device, If the transistor is a P-type transistor, by lowering the voltage level of the first luminance control signal output from the first control signal generating means by a predetermined level, further comprising a level shift circuit for causing the transistor to full swing Automatic luminance control device for a liquid crystal display, characterized in that. The method of claim 10, The level shift circuit, A transistor having a current path connected in series between a power supply voltage source and said third control signal generating means, and a control terminal connected to said first control signal generating means; A first resistor connected in series with the current path of the transistor; A diode connected in series between said resistor and said ground; And a second resistor connected in parallel with the diode. The method of claim 3, wherein The variable luminance control voltage, Vduty = {Vo + (Vc-Vo) × [1-EXP [-T1 / (R × C)]]} × EXP [(T1-1H) / (R × C)] is satisfied. Automatic brightness control for the device. In the backlight brightness adjustment method of the liquid crystal display device: Calculating a gray value of image data to be displayed on the liquid crystal display; Generating a first luminance control signal corresponding to the gradation value; And And automatically adjusting the brightness of the backlight by a third brightness control signal generated in response to the first brightness control signal and a second brightness control signal generated from the computer main body. Automatic brightness control method for.