KR101362957B1 - LCD and drive method thereof - Google Patents

Abstract

The present invention provides a liquid crystal display device that can provide an optimum brightness for each user according to the ambient brightness, comprising: a backlight assembly for supplying a driving voltage to irradiate light; And read out the duty ratio corresponding to the current ambient light intensity value from the first lookup table and at the same time read the variable duty ratio corresponding to the current ambient light intensity value from the second lookup table. The driving duty signal having a duty ratio calculated by calculating the read duty ratio and the read variable duty ratio according to a command, and generating the driving voltage having a magnitude proportional to the duty ratio of the driving control signal; It includes an inverter output to the assembly.

LCD, backlight, light, duty ratio

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a liquid crystal display

1 is an equivalent circuit diagram of a pixel formed in a general liquid crystal display device.

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

3 is a configuration diagram of the inverter shown in FIG.

4 is a circuit diagram of the drive driver shown in FIG.

5 and 6 are diagrams illustrating an operation of the driving driver shown in FIG. 4.

FIG. 7 is a signal characteristic diagram of the drive driver shown in FIG. 4; FIG.

Explanation of symbols on the main parts of the drawings

100: liquid crystal display device 110: liquid crystal display panel

120: data driver 130: gate driver

140: gamma reference voltage generator 150: common voltage generator

160: gate driving voltage generator 170: timing controller

180: backlight assembly 190: inverter

191: square wave oscillator 192: integrator

193: comparator 194: first memory

195: Second Memory 196: Light Sensor

197: user input unit 197-1: basic luminance button

197-2: High Brightness Button 197-3: Low Brightness Button

198: drive control unit 199: drive driver

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device and a driving method thereof capable of providing an optimal brightness for each user according to ambient brightness.

The liquid crystal display device displays an image by adjusting a light transmittance of liquid crystal cells according to a video signal, and an active matrix type liquid crystal display device in which a switching element is formed for each liquid crystal cell enables active control of the switching device This is advantageous for video implementation. A thin film transistor (hereinafter referred to as "TFT") is mainly used as a switching element used in such an active matrix type liquid crystal display device as shown in Fig.

1, an active matrix type liquid crystal display device converts digital input data into an analog data voltage on the basis of a gamma reference voltage and supplies the analog data voltage to a data line DL and simultaneously supplies a scan pulse to a gate line GL Thereby filling the liquid crystal cell Clc.

The gate electrode of the TFT is connected to the gate line GL and the source electrode thereof is connected to the data line DL and the drain electrode of the TFT is connected to the pixel electrode of the liquid crystal cell Clc and one electrode of the storage capacitor Cst Respectively.

A common voltage Vcom is supplied to the common electrode of the liquid crystal cell Clc.

The storage capacitor Cst serves to charge the data voltage applied from the data line DL when the TFT is turned on to maintain the voltage of the liquid crystal cell Clc constant.

  When a scan pulse is applied to the gate line GL, the TFT is turned on to form a channel between the source electrode and the drain electrode to apply a voltage on the data line DL to the pixel electrode of the liquid crystal cell Clc Supply. At this time, the liquid crystal molecules of the liquid crystal cell Clc are changed in arrangement by the electric field between the pixel electrode and the common electrode to modulate the incident light.

Conventional liquid crystal display having pixels having such a structure irradiates light to each pixel by using a backlight assembly. However, since the LCD illuminates only light of a constant intensity, it does not provide an optimal brightness for each user according to ambient brightness. Have

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a liquid crystal display device and a driving method thereof capable of providing an optimum brightness for each user according to the ambient brightness.

According to an aspect of the present invention, there is provided a liquid crystal display device including: a backlight assembly configured to emit light by receiving a driving voltage; And read out the duty ratio corresponding to the current ambient light intensity value from the first lookup table and at the same time read the variable duty ratio corresponding to the current ambient light intensity value from the second lookup table. The driving duty signal having a duty ratio calculated by calculating the read duty ratio and the read variable duty ratio according to a command, and generating the driving voltage having a magnitude proportional to the duty ratio of the driving control signal; It includes an inverter output to the assembly.

The inverter may include: a first memory configured to store the predetermined first lookup table in which a plurality of light intensity values and a plurality of duty ratios correspond one-to-one; A second memory configured to store the predetermined second lookup table in which a plurality of light intensity values and a plurality of variable duty ratios are established in one-to-one correspondence; An optical sensor for detecting a light intensity of a current surrounding and outputting a detected light intensity value; The duty ratio corresponding to the sensed light intensity value is read out from the predetermined first lookup table, and at the same time the variable duty ratio corresponding to the sensed light intensity value is read out from the second predetermined lookup table. A driving controller for generating a driving control signal having a duty ratio calculated by calculating the read duty ratio and the read variable duty ratio according to the received luminance control command; And a driving driver for generating the driving voltage having a magnitude proportional to the duty ratio of the driving control signal.

The liquid crystal display of the present invention further includes a user input unit for inputting the brightness control command for indicating the brightness level by the backlight assembly.

The user input unit may include: a basic luminance button for inputting the luminance control command for instructing provision of a basic luminance suitable for a current ambient brightness; A high brightness button for inputting the brightness control command instructing to provide a brightness that is brighter than the basic brightness suitable for the current ambient brightness; And a low luminance button for inputting the luminance control command for instructing provision of luminance darker than the basic luminance suitable for the current ambient brightness.

The driving controller reads the duty ratio set in the first lookup table in response to the light intensity value sensed by the optical sensor when the luminance control command for providing the basic luminance suitable for the current ambient brightness is input. And outputting a drive control signal having the drawn duty ratio to the drive driver.

When the brightness control command is provided to instruct to provide a brightness that is brighter than the basic brightness suitable for the current ambient brightness, the driving controller may adjust the duty ratio set in the first lookup table to correspond to the light intensity value detected by the optical sensor. Reads the variable duty ratio set in the second lookup table corresponding to the light intensity value which is read and simultaneously sensed, and adds the read duty ratio and the variable duty ratio to the drive driver with the added duty ratio. It is characterized by outputting.

When the luminance control command for instructing the provision of a luminance darker than the basic luminance suitable for the current ambient brightness is input, the driving controller controls the duty ratio set in the first lookup table to correspond to the light intensity value detected by the optical sensor. Read out the variable duty ratio set in the second lookup table in correspondence with the light intensity value which is simultaneously read out, and subtract the variable duty ratio read out from the second lookup table from the duty ratio read out from the first lookup table. And outputting a driving control signal having a subtracted duty ratio to the driving driver.

According to an exemplary embodiment of the present invention, a method of driving a liquid crystal display device includes: irradiating light with a driving voltage; Sensing light intensity around the liquid crystal display; According to the input luminance control command, a driving control signal having a duty ratio set to a predetermined first lookup table corresponding to the detected light intensity value is generated or a duty ratio corresponding to the detected light intensity value is set to a first predetermined value. Read duty from the lookup table and at the same time read the variable duty ratio corresponding to the sensed light intensity value from a predetermined second lookup table and has a duty ratio calculated by calculating the read duty ratio and the read variable duty ratio Generating a drive control signal; And outputting the driving voltage having a magnitude proportional to a duty ratio of the generated driving control signal to a backlight assembly.

An inverter of a liquid crystal display according to the present invention comprises: a first memory for storing the predetermined first lookup table in which a plurality of light intensity values and a plurality of duty ratios are set in one-to-one correspondence; A second memory configured to store the predetermined second lookup table in which a plurality of light intensity values and a plurality of variable duty ratios are established in one-to-one correspondence; An optical sensor for detecting a light intensity of a current surrounding and outputting a detected light intensity value; And reading a duty ratio corresponding to the sensed light intensity value from the predetermined first lookup table and simultaneously reading a variable duty ratio corresponding to the sensed light intensity value from the predetermined second lookup table. And a driving controller configured to calculate the read duty ratio and the read variable duty ratio and generate a drive control signal having a calculated duty ratio according to the luminance control command.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

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

Referring to FIG. 2, in the liquid crystal display device 100, a plurality of data lines DL1 to DLm and a plurality of gate lines GL1 to GLn cross each other and a liquid crystal cell Clc is formed at an intersection thereof. A liquid crystal display panel 110 including a thin film transistor (TFT) for driving, a data driver 120 for supplying data to data lines DL1 to DLm of the liquid crystal display panel 110, A gate driver 130 for supplying scan pulses to the gate lines GL1 to GLn of the liquid crystal display panel 110, and a gamma reference voltage generator for generating a gamma reference voltage and supplying the gamma reference voltage to the data driver 120. 140, the common voltage generator 150 for generating the common voltage Vcom and supplying the common voltage to the common electrode of the liquid crystal cell Clc of the liquid crystal display panel 110, the gate high voltage VGH and the gate low voltage. A gate driving voltage generator for generating (VGL) and supplying it to the gate driver 130 ( 160 and a timing controller 170 for controlling the data driver 120 and the gate driver 130.

In addition, the liquid crystal display device 100 of the present invention reads a backlight assembly 180 for irradiating light with an AC driving voltage and a duty ratio corresponding to a current ambient light intensity value from a predetermined first lookup table. At the same time, the duty duty calculated by reading the variable duty ratio corresponding to the current ambient light intensity value from a predetermined second lookup table and then calculating the read duty ratio and the read out variable duty ratio according to the input luminance control command. The inverter 190 generates a drive control signal having a ratio and outputs an AC drive voltage having a magnitude proportional to the duty ratio of the generated drive control signal to the backlight assembly 180.

In the liquid crystal display panel 110, liquid crystal is injected between two glass substrates. On the lower glass substrate of the liquid crystal display panel 110, the data lines DL1 to DLm and the gate lines GL1 to GLn are orthogonal. TFTs are formed at the intersections of the data lines DL1 to DLm and the gate lines GL1 to GLn. The TFT supplies data on the data lines DL1 to DLm to the liquid crystal cell Clc in response to the scan pulse. The gate electrode of the TFT is connected to the gate lines GL1 to GLn, and the source electrode of the TFT is connected to the data lines DL1 to DLm. The drain electrode of the TFT is connected to the pixel electrode of the liquid crystal cell Clc and the storage capacitor Cst.

The TFT is turned on in response to the scan pulse supplied to the gate terminal via the gate line connected to its gate terminal among the gate lines GL1 to GLn. Video data on the data line connected to the drain terminal of the TFT among the turn-on data lines DL1 to DLm of the TFT is supplied to the pixel electrode of the liquid crystal cell Clc.

The data driver 120 supplies data to the data lines DL1 to DLm in response to the data driving control signal DDC supplied from the timing controller 170, and digital video data supplied from the timing controller 170. After sampling and latching the RGB, the liquid crystal cell Clc of the liquid crystal display panel 110 is converted into an analog data voltage capable of expressing gray scale based on the gamma reference voltage supplied from the gamma reference voltage generator 140. Supply to the data lines DL1 to DLm.

The gate driver 130 sequentially generates scan pulses, that is, gate pulses, in response to the gate driving control signal GDC and the gate shift clock GSC supplied from the timing controller 170, thereby providing the gate lines GL1 to GLn. To feed. In this case, the gate driver 130 determines the high level voltage and the low level voltage of the scan pulse according to the gate high voltage VGH and the gate low voltage VGL supplied from the gate driving voltage generator 160.

The gamma reference voltage generating unit 140 generates a positive polarity gamma reference voltage and a negative polarity gamma reference voltage, and outputs the positive polarity gamma reference voltage and the negative polarity reference voltage to the data driver 120.

The common voltage generator 150 receives the high potential power voltage VDD to generate the common voltage Vcom and supplies the common voltage Vcom to the common electrodes of the liquid crystal cells Clc of each pixel of the liquid crystal display panel 110.

The gate driving voltage generator 160 receives the high potential power voltage VDD to generate the gate high voltage VGH and the gate low voltage VGL to supply the gate driver 130 to the gate driver 130. Here, the gate driving voltage generation unit 160 generates a gate high voltage VGH that is greater than or equal to the threshold voltage of the TFTs provided in each pixel of the liquid crystal display panel 110 and generates a gate low voltage that is less than the threshold voltage of the TFT. VGL). The gate high voltage VGH and the gate low voltage VGL generated in this way are used to determine the high level voltage and the low level voltage of the scan pulse generated by the gate driver 130, respectively.

The timing controller 170 supplies digital video data RGB supplied from the system to the data driver 120 and drives data using the horizontal / vertical synchronization signals H and V according to the clock signal CLK. The control signal DDC and the gate driving control signal GDC are generated and supplied to the data driver 120 and the gate driver 130, respectively. Here, the data driving control signal DDC includes a source shift clock SSC, a source start pulse SSP, a polarity control signal POL, a source output enable signal SOE, Includes a gate start pulse GSP and a gate output enable GOE.

The backlight assembly 180 is disposed on the rear surface of the liquid crystal display panel 110 and emits light by an AC driving voltage supplied from the inverter 190 to irradiate light to each pixel of the liquid crystal display panel 110.

The inverter 190 receives a power supply voltage Vs from a power board (not shown) of the system and supplies AC driving voltages having opposite phases to the backlight assembly 180, and a plurality of light intensity values and a plurality of duty ratios are one-to-one. The first lookup table set corresponding to and the second lookup table set in correspondence with a plurality of light intensity values and a plurality of variable duty ratios in one-to-one correspondence are stored.

The inverter 190 senses the light intensity around the liquid crystal display device 100, reads the duty ratio corresponding to the detected light intensity value from the predetermined first lookup table, and simultaneously adjusts the variable duty corresponding to the detected light intensity value. The ratio is read out from the second predetermined lookup table. Then, after generating a driving control signal having a duty ratio calculated by calculating the duty ratio read out and the variable duty ratio read according to the luminance control command input by the user, the magnitude is proportional to the duty ratio of the driving control signal. The AC driving voltage having a is supplied to the backlight assembly 180 in real time.

3 is a configuration diagram of the inverter shown in FIG. 2.

Referring to FIG. 3, the inverter 190 includes a square wave oscillator 191 for oscillating a square wave signal, an integrator 192 for converting a square wave signal oscillated from the square wave oscillator 191 into a triangular wave signal, and an integrator ( Comparator 193 for generating a burst dimming signal according to the comparison result by comparing the triangular wave signal converted by the 192 and the DC voltage.

In addition, the inverter 190 may include a first memory 194 for storing a first lookup table in which a plurality of light intensity values and a plurality of duty ratios are set in one-to-one correspondence, and a plurality of light intensity values and a plurality of variables. A second memory 195 for storing a second lookup table in which duty ratios are set in one-to-one correspondence, an optical sensor 196 that detects a light intensity of a current surrounding and outputs a detected light intensity value, and a backlight assembly 180 A user input unit 197 for inputting a luminance control command for instructing luminance control, and a duty ratio corresponding to the sensed light intensity value from the first lookup table, and at the same time a variable corresponding to the sensed light intensity value After the duty ratio is read from the second lookup table, a driving control signal having a duty ratio calculated by calculating the duty ratio and the read variable duty ratio according to the brightness control command input through the user input unit 197 is generated. Driven And a fisherman 198, and a drive control unit 198 drives the driver 199, which generates an AC driving voltage having a magnitude that is proportional to the duty ratio of the driving signal output from the. Here, the drive control signal is a pulse width modulation signal (PWM).

The square wave oscillator 191 oscillates a square wave signal used for generating the burst dimming signal and outputs the generated square wave signal to the integrator 192.

The integrator 192 converts the square wave signal oscillated from the square wave oscillator 191 into a triangular wave signal and outputs it to the comparator 192.

The comparator 193 receives a triangular wave signal output from the integrator 193 through an inverting input terminal (-), receives a DC voltage of DC 0V to 3.3V through a non-inverting input terminal (+), and receives a burst dimming signal through the output terminal. Output The comparator 193 senses a DC voltage input to the non-inverting input terminal (+) based on the triangular wave signal input to the inverting input terminal (-) and outputs a burst dimming signal to the driving controller 198 through the output terminal. More specifically, the high signal should be output in the section where the triangular wave signal is greater than the DC voltage. However, since the triangular wave signal is input to the inverting input terminal (-), the low signal, which is the inverted signal of the high signal, is output. The low signal should be output in the section smaller than the voltage. However, since the triangular wave signal is input to the inverting input terminal (-), the high signal, which is the inverted signal of the low signal, is output.

A first lookup table is stored in the first memory 194, and a plurality of light intensity values and a plurality of duty ratios are set in one-to-one correspondence with the first lookup table. Here, the plurality of light intensity values set in the first lookup table are ambient light intensity values predicted by the light sensor 196 and are light intensity values detected through experiments, and a plurality of duty values set in the first lookup table are used. The ratios are the duty ratios that have been experimentally detected as the duty ratios of the drive control signals for determining the magnitude of the AC drive voltage to provide the luminance suitable for the current ambient brightness. That is, the first lookup table is set to correspond to the light intensity indicating the current ambient brightness and the duty ratio of the drive control signal to provide the brightness suitable for the current ambient brightness.

A second lookup table is stored in the second memory 195, and a plurality of light intensity values and a plurality of variable duty ratios are set in one-to-one correspondence with the second lookup table. Here, the plurality of light intensity values set in the second lookup table are ambient light intensity values predicted by the light sensor 196 and are the same light intensity values set in the first lookup table. The variable duty ratios set in the second lookup table are values used for calculation with the duty ratios set in the first lookup table, and the variable duty ratios of the second lookup table are displayed when a screen brighter than the luminance suitable for the current ambient brightness is displayed. The ratio is added to the duty ratio of the first lookup table, and conversely, when displaying a screen darker than the luminance suitable for the current ambient brightness, the variable duty ratio of the second lookup table is subtracted from the duty ratio of the first lookup table. That is, the variable duty ratios set in the second lookup table are to satisfy different luminance desires of users who want a bright screen or a dark screen compared to the current ambient brightness.

The optical sensor 196 detects the light intensity representing the brightness around the liquid crystal display 100 in real time and outputs the detected light intensity value to the driving controller 198. Here, the optical sensor 196 converts the detected light intensity value into a voltage that can be recognized by the driving controller 198 and outputs the converted voltage.

The user input unit 197 includes a basic brightness button 197-1, a high brightness button 197-2, and a low brightness button 197-3 for inputting a user command indicating a brightness level by the backlight assembly 180. It is provided. Here, the basic brightness button 197-1, the high brightness button 197-2, and the low brightness button 197-3 are disposed to be exposed to the outside so that the user can press using a body or a tool.

The basic luminance button 197-1 is for inputting a luminance control command for instructing provision of a basic luminance suitable for the current ambient brightness. When the luminance control command for instructing the basic luminance is input, a variable set in the second lookup table is input. The duty ratio is not calculated with the duty ratio set in the first lookup table, and a driving control signal having a duty ratio set in the first lookup table is generated in correspondence with the current ambient light intensity value.

The high brightness button 197-2 is for inputting a brightness control command for instructing provision of brightness that is brighter than the basic brightness suitable for the current ambient brightness. When the brightness control command for instructing this high brightness is input, the high brightness button 197-2 is set in the second lookup table. The variable duty ratio generates a drive control signal having a duty ratio set in the first lookup table and an added duty ratio.

The low luminance button 197-3 is for inputting a luminance control command for instructing provision of a luminance darker than the basic luminance suitable for the current ambient brightness. When the luminance control command for instructing this low luminance is input, the second lookup table is input. The variable duty ratio set at is subtracted from the duty ratio set at the first lookup table, and a driving control signal having the duty ratio subtracted is generated.

The drive control unit 198 supplies a drive control signal having a duty ratio indicated by the burst dimming signal input from the comparator 193 to the drive driver 199, and at the ambient light intensity detected by the optical sensor 196. In proportion, the duty ratio of the driving control signal is adjusted as follows.

When the user presses the basic luminance button 197-1 and inputs a luminance control command for instructing provision of the basic luminance suitable for the current ambient brightness, the driving controller 198 receives the ambient light intensity value detected by the optical sensor 196. Correspondingly, the duty ratio set in the first lookup table is read and the driving control signal having the read duty ratio is output to the driving driver 199.

When the user presses the high brightness button 197-2 and inputs a brightness control command instructing to provide a brightness that is brighter than the basic brightness suitable for the current ambient brightness, the driving control unit 198 receives the ambient light detected by the light sensor 196. The duty ratio set in the first lookup table is read in correspondence with the intensity value, and the variable duty ratio set in the second lookup table is read in correspondence with the detected ambient light intensity value. Subsequently, the driving controller 198 adds the duty ratio and the variable duty ratio read out from the first and second lookup tables, respectively, and outputs a driving control signal having the added duty ratio to the driving driver 199.

When the user presses the low luminance button 197-3 and inputs a luminance control command for instructing to provide a luminance darker than the basic luminance suitable for the current ambient brightness, the driving controller 198 causes the surroundings detected by the optical sensor 196 to be inclined. The duty ratio set in the first lookup table is read in correspondence with the light intensity value, and the variable duty ratio set in the second lookup table is read in correspondence with the detected ambient light intensity value. Subsequently, the driving controller 198 subtracts the variable duty ratio read out from the second lookup table from the duty ratio read out from the first lookup table, and outputs a drive control signal having the duty ratio subtracted from the duty ratio read out to the drive driver 199.

The driving driver 199 generates an AC driving voltage proportional to the duty ratio of the driving control signal output from the driving control unit 198 and supplies it to the backlight assembly 180. Here, when the duty ratio of the driving control signal is increased, the AC driving voltage is increased in proportion to this, so that the luminance by the backlight assembly 180 is increased. On the contrary, when the duty ratio of the driving control signal is decreased, the AC driving voltage (+,-) is proportional to this. This is reduced to lower the brightness by the backlight assembly 180.

On the other hand, in the initial state in which the burst dimming signal is first supplied, the driving control unit 198 supplies a driving control signal having a predetermined initial duty ratio to the driving driver 199.

As described above, the present invention does not provide only the basic luminance suitable for the current ambient brightness, but uses the backlight assembly 180 to emit light or dark brightness that is brighter than the basic luminance suitable for the current ambient brightness according to the user's luminance preference. By providing the optimal brightness for each user according to the ambient brightness.

4 is a circuit diagram of the driving driver shown in FIG. 3.

Referring to FIG. 4, the driving driver 199 may switch first and second DC / AC switching units 199-1 and 199 to output an AC voltage by switching the DC power voltage Vs under the control of the driving controller 198. -2), a first transformer 199-3 for boosting the AC voltage output from the first DC / AC switching unit 199-1 to one end of the backlight assembly 180, and a second DC The AC voltage output from the AC switching unit 199-2 is boosted to supply an AC driving voltage having a phase opposite to that of the AC driving voltage output from the first transformer 199-3 to the other end of the backlight assembly 180. And a second transformer 199-4.

The first DC / AC switching unit 199-1 switches the DC power voltage Vs according to the driving control signal supplied from the driving control unit 198 and outputs an AC voltage to the first transformer 199-3. An AC voltage of +) and an AC voltage of the negative electrode (−) are respectively supplied to the first transformer 199-3 through two signal paths.

The second DC / AC switching unit 199-2 switches the DC power voltage Vs according to the driving control signal supplied from the driving control unit 198, and outputs an AC voltage to the second transformer 199-4. An AC voltage of +) and an AC voltage of the negative electrode (−) are respectively supplied to the second transformer 199-4 through two signal paths. In particular, the first and second DC / AC switching units 199-1 and 199-2 output AC voltages having the same phase.

The first transformer 199-3 boosts an AC voltage input from the first DC / AC switching unit 199-1 through two signal paths and supplies an AC driving voltage to one end of the backlight assembly 180. .

The second transformer 199-4 boosts an AC voltage input from the second DC / AC switching unit 199-2 through two signal paths and supplies the AC driving voltage to the other end of the backlight assembly 180. The AC driving voltage having a phase opposite to that of the AC driving voltage output from the first transformer 199-3 is supplied.

The first DC / AC switching unit 199-1 includes first and second N-MOS PFETs FT1 and FT2 connected in series between a power supply for supplying a DC power supply voltage Vs and ground. And third and fourth N-MOS pets FT3 and FT4 connected in series between a power supply for supplying a DC power supply voltage Vs and ground and symmetrically connected to the first and second N-MOS pets FT1 and FT2. Equipped.

The first NMOS pet FT1 includes a drain to which the DC power supply voltage Vs is applied, a gate to which the driving control signal from the driving control unit 198 is applied, and a source connected to the first output node N1.

The second N-MOS pet FT2 may include a drain commonly connected to a source of the first N-MOS pet FT1 and a first output node N1, a gate to which a driving control signal from the driving control unit 198 is applied, and It consists of a source connected to ground.

The third NMOS pet FT3 includes a drain to which the DC power supply voltage Vs is applied, a gate to which the driving control signal from the driving control unit 198 is applied, and a source connected to the second output node N2.

The fourth N-MOS pet FT4 may include a drain commonly connected to the source of the third N-MOS pet FT3 and the second output node N2, a gate to which the driving control signal from the driving control unit 198 is applied, and It consists of a source connected to ground.

Here, the first and second output nodes N1 and N2 are connected to the input side of the first transformer 199-3, respectively.

The second DC / AC switching unit 199-2 supplies the fifth and sixth NMOS pets FT5 and FT6 connected in series between the power supply for supplying the DC power supply voltage Vs and the ground, and the DC power supply voltage Vs. And the seventh and eighth N-MOS pets FT7 and FT8 connected in series between the power supply and the ground and symmetrically connected to the fifth and sixth N-MOS pets FT5 and FT6.

The fifth NMOS pet FT5 includes a drain to which the DC power supply voltage Vs is applied, a gate to which the driving control signal from the driving control unit 198 is applied, and a source connected to the third output node N3.

The sixth N-MOS pet FT6 may include a drain commonly connected to the source of the fifth N-MOS pet FT5 and the third output node N3, a gate to which a driving control signal from the driving control unit 198 is applied, and It consists of a source connected to ground.

The seventh NMOS pet FT7 includes a drain to which the DC power supply voltage Vs is applied, a gate to which the driving control signal from the driving control unit 198 is applied, and a source connected to the fourth output node N4.

The eighth N-MOS pet FT8 may include a drain commonly connected to the source of the seventh N-MOS pet FT7 and the fourth output node N4, a gate to which the driving control signal from the driving control unit 198 is applied, and It consists of a source connected to ground.

Here, the third and fourth output nodes N3 and N4 are connected to the input side of the second transformer 199-4, respectively.

The first transformer 199-3 includes a primary coil L1 having both ends connected to the first and second output nodes N1 and N2 of the first DC / AC switching unit 199-1, and one side of the first transformer 199-3. A stage is connected to one end of the backlight assembly 180 and the other end is provided with a secondary coil L2 connected to ground.

The second transformer 199-4 has a primary coil L3 connected at both ends thereof to the third and fourth output nodes N3 and N4 of the second DC / AC switching unit 199-2 and one side thereof. A stage is connected to one end of the backlight assembly 180 and the other end has a secondary coil L4 connected to ground.

In particular, the coils L1 and L2 of the first transformer 199-3 and the coils L3 and L4 of the second transformer 199-4 are wound in opposite directions. Accordingly, the AC drive voltage output from the first transformer 199-3 and the AC drive voltage output from the second transformer 199-4 have opposite phases.

An operation process of the driving driver 199 having such a circuit configuration will now be described in detail with reference to FIGS. 5 to 7.

As shown in FIG. 5, the driving controller 198 transmits a high level driving control signal to the gates of the first and fourth N-MOS pets FT1 and FT4 of the first DC / AC switching unit 199-1. When supplied to the gates of the fifth and eighth N-MOS pets FT5 and FT8 of the second DC / AC switching unit 199-2, the first and fourth N-MOS pets FT1 and FT4 and the first and fourth N-MOS pets FT1 and FT4 are respectively supplied. The fifth and eighth NMOS pets FT5 and FT8 are simultaneously turned on.

Accordingly, in the first DC / AC switching unit 199-1, the DC power voltage Vs is switched by the first NMOS pet FT1, and the first transformer 199-3 is supplied through the first output node N1. ), Where the first N-MOS pet (FT1), the first output node (N1), the first side coil (L1) of the first transistor (199-3), the second output node (N2) and the fourth N A path of a signal applied to ground through the MOSFET FT4 is sequentially formed.

In the second DC / AC switching unit 199-2, the DC power supply voltage Vs is switched by the fifth NMOS pet FT5, and the second transformer 199-4 is connected through the third output node N3. In this case, the fifth N-MOS pet (FT5), the third output node (N3), the primary coil (L3), the fourth output node (N4) and the eighth N-MOS of the second transistor (199-4) A path of a signal applied to the ground by sequentially passing through the pet FT8 is formed.

As shown in FIG. 6, the driving control unit 198 transmits a high level driving control signal to the gates of the second and third NMOS pets FT2 and FT3 of the first DC / AC switching unit 199-1. When supplied to the gates of the sixth and seventh N-MOS pets FT6 and FT7 of the second DC / AC switching unit 199-2, the second and third N-MOS pets FT2 and FT3 and the second The sixth and seventh NMOS pets FT6 and FT7 are turned on at the same time.

Accordingly, in the first DC / AC switching unit 199-1, the DC power supply voltage Vs is switched by the third NMOS pet FT3, and the first transformer 199-3 is supplied through the second output node N2. ), Where the third N-MOS pet (FT3), the second output node (N2), the primary coil (L1), the first output node (N1) and the second N-MOS pet of the first transformer 324 A path of a signal that is sequentially passed through FT2 and applied to ground is formed.

In the second DC / AC switching unit 199-2, the DC power supply voltage Vs is switched by the seventh NMOS pet FT7, and the second transformer 199-4 is applied through the fourth output node N4. In this case, the seventh N-MOS pet (FT7), the fourth output node (N4), the primary coil (L3), the third output node (N3) and the sixth N-MOS pet ( A path of a signal that is sequentially passed through FT6) to ground is formed.

As such, the signal paths formed through the first and fourth N-MOS pets FT1 and FT4 and the signal paths formed through the second and third N-MOS pets FT2 and FT3 according to the driving control signal are in opposite directions. As shown in FIG. 7A, the first DC / AC switching unit 199-1 switches the DC power supply voltage Vs in both directions according to the driving control signal, so that the positive electrode (+) and the negative electrode ( AC voltage of-) is supplied to both ends of the primary coil L1 of the first transformer 199-3.

In addition, the signal paths formed through the fifth and eighth N-MOS pets FT5 and FT8 and the signal paths formed through the sixth and seventh N-MOS pets FT6 and FT7 are in opposite directions according to the driving control signal. As shown in FIG. 9B, the second DC / AC switching unit 199-2 switches the DC power supply voltage Vs in both directions according to the driving control signal, so that the positive electrode and the negative electrode are negative. Is supplied to both ends of the primary coil L3 of the second transformer 199-4.

In addition, since the coils L1 and L2 of the first transformer 199-3 and the coils L3 and L4 of the second transformer 199-4 are wound in opposite directions, as shown in FIG. 9. The AC drive voltage (Fig. 9 (A)) output from the first transformer 199-3 and the AC drive voltage (Fig. 9 (B)) output from the second transformer 199-4 have opposite phases.

As described above, the present invention does not provide only basic luminance suitable for the current ambient brightness, but provides brighter or darker brightness using the backlight assembly than the basic luminance suitable for the current ambient brightness according to the user's luminance preference. In addition, it is possible to provide an optimal brightness for each user according to the surrounding brightness.

Although the technical spirit of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above embodiment is for the purpose of description and not of limitation. In addition, it will be understood by those of ordinary skill in the art that various embodiments are possible within the scope of the technical idea of the present invention.

Claims (17)

A backlight assembly receiving a driving voltage to irradiate light; And Read the duty ratio corresponding to the current ambient light intensity value from the first lookup table and at the same time read the variable duty ratio corresponding to the current ambient light intensity value from the second lookup table, and then according to the input luminance control command. An inverter for generating a drive control signal by performing any one of the third to third operations, and outputting a drive voltage having a magnitude proportional to the generated drive control signal to the backlight assembly; In accordance with the first operation, the inverter generates a drive control signal having the read duty ratio; In accordance with the second operation, the inverter adds the read duty ratio and the variable duty ratio and generates a drive control signal having the added duty ratio; And, According to the third operation, the inverter subtracts the variable duty ratio from the read duty ratio and generates a drive control signal having the subtracted duty ratio. The method of claim 1, The inverter, A first memory configured to store the first lookup table in which a plurality of light intensity values and a plurality of duty ratios are established in one-to-one correspondence; A second memory configured to store the second lookup table in which a plurality of light intensity values and a plurality of variable duty ratios are set in one-to-one correspondence; An optical sensor for detecting a light intensity of a current surrounding and outputting a detected light intensity value; After reading the duty ratio corresponding to the sensed light intensity value from the first lookup table and simultaneously reading the variable duty ratio corresponding to the sensed light intensity value from the second lookup table, the input luminance control command A driving controller configured to generate the driving control signal by performing any one of the first to third operations according to the first and third operations; And And a driving driver for generating the driving voltage having a magnitude proportional to a duty ratio of the driving control signal. The method of claim 2, And a user input unit for inputting the brightness control command indicating the brightness level by the backlight assembly. The method of claim 3, wherein Wherein the user input unit comprises: A basic luminance button for inputting the luminance control command for instructing provision of a basic luminance suitable for the current ambient brightness; A high brightness button for inputting the brightness control command instructing to provide a brightness that is brighter than the basic brightness suitable for the current ambient brightness; And And a low luminance button for inputting the luminance control command for instructing provision of luminance lower than the basic luminance suitable for the current ambient brightness. The method of claim 2, When the luminance control command instructing the provision of a basic luminance suitable for the current ambient brightness is input, the driving controller reads the duty ratio set in the first lookup table in response to the light intensity value detected by the optical sensor. And performing the first operation of generating a drive control signal having the duty cycle, and outputting the generated drive control signal to the drive driver. The method of claim 2, When the luminance control command is provided to instruct the provision of a brightness that is brighter than the basic luminance suitable for the current ambient brightness, the driving controller may adjust the duty ratio set in the first lookup table in correspondence with the light intensity value detected by the optical sensor. Reading out the variable duty ratio set in the second lookup table corresponding to the light intensity value detected at the same time, and generating a driving control signal having the added duty ratio by adding the read duty ratio and the variable duty ratio; Performing operation 2 and outputting the generated drive control signal to the drive driver. The method of claim 2, When the luminance control command for providing a luminance lower than a basic luminance suitable for the current ambient brightness is input, the driving controller controls the duty ratio set in the first lookup table to correspond to the light intensity value detected by the optical sensor. Read out the variable duty ratio set in the second lookup table in correspondence with the light intensity value which is simultaneously read out, and subtract the variable duty ratio read out from the second lookup table from the duty ratio read out from the first lookup table. And performing the third operation of generating a drive control signal having a subtracted duty ratio, and outputting the generated drive control signal to the drive driver. Irradiating light with a driving voltage; Sensing light intensity around the liquid crystal display; Read the duty ratio corresponding to the current ambient light intensity value from the first lookup table and at the same time read the variable duty ratio corresponding to the current ambient light intensity value from the second lookup table, and then according to the input luminance control command. A step of generating a drive control signal by performing any one of the third to third operations; And Outputting the driving voltage having a magnitude proportional to the duty ratio of the generated driving control signal to a backlight assembly; According to the first operation, the step A generates a drive control signal having the read duty ratio; According to the second operation, the step A adds the read duty ratio and the variable duty ratio and generates a drive control signal having the added duty ratio; And, According to the third operation, the step A subtracts the variable duty ratio from the read duty ratio, and generates a drive control signal having the subtracted duty ratio. 9. The method of claim 8, In step A, The driving control having a duty ratio read out by reading a duty ratio set in the first lookup table corresponding to the sensed light intensity value when the luminance control command instructing provision of a basic luminance suitable for the current ambient brightness is input. And the first operation of generating a signal is performed. 9. The method of claim 8, In step A, When the luminance control command for providing a brightness higher than the basic luminance suitable for the current ambient brightness is input, the duty ratio set in the first lookup table is read in correspondence with the sensed light intensity value and at the same time the sensed light intensity The second operation of reading out the variable duty ratio set in the second lookup table corresponding to the value and generating the driving control signal having the added duty ratio by adding the read duty ratio and the variable duty ratio is performed. A method of driving a liquid crystal display device. 9. The method of claim 8, In step A, When the luminance control command for instructing the provision of a luminance darker than the basic luminance suitable for the current ambient brightness is input, the duty ratio set in the first lookup table is read in correspondence with the sensed light intensity value and at the same time the sensed light intensity A variable duty ratio read out from the second lookup table by subtracting the variable duty ratio set in the second lookup table corresponding to a value, and subtracting the variable duty ratio read out from the second lookup table from the duty ratio read out from the first lookup table; And the third operation of generating a drive control signal is performed. A first memory configured to store a first lookup table in which a plurality of light intensity values and a plurality of duty ratios are established in one-to-one correspondence; A second memory configured to store a second lookup table in which a plurality of light intensity values and a plurality of variable duty ratios are established in one-to-one correspondence; An optical sensor for detecting a light intensity of a current surrounding and outputting a detected light intensity value; And After reading the duty ratio corresponding to the detected light intensity value from the first lookup table and simultaneously reading the variable duty ratio corresponding to the detected light intensity value from the second lookup table, And a driving controller for performing any one of the first to third operations to generate a driving control signal. In accordance with the first operation, the drive control section generates a drive control signal having the read duty ratio; In accordance with the second operation, the drive control unit adds the read duty ratio and the variable duty ratio and generates a drive control signal having the added duty ratio; And, In accordance with the third operation, the drive control unit subtracts the variable duty ratio from the read duty ratio and generates a drive control signal having the subtracted duty ratio. 13. The method of claim 12, User input unit for inputting the brightness control command indicating the brightness level Inverter of the liquid crystal display device further comprising. 14. The method of claim 13, Wherein the user input unit comprises: A basic luminance button for inputting the luminance control command for instructing provision of a basic luminance suitable for the current ambient brightness; A high brightness button for inputting the brightness control command instructing to provide a brightness that is brighter than the basic brightness suitable for the current ambient brightness; And And a low brightness button for inputting the brightness control command for instructing provision of a brightness darker than a basic brightness suitable for current ambient brightness. 13. The method of claim 12, When the luminance control command instructing the provision of a basic luminance suitable for the current ambient brightness is input, the driving controller reads the duty ratio set in the first lookup table in response to the light intensity value detected by the optical sensor. And the first operation of generating the drive control signal having the duty cycle. 13. The method of claim 12, When the luminance control command is provided to instruct the provision of a brightness that is brighter than the basic luminance suitable for the current ambient brightness, the driving controller may adjust the duty ratio set in the first lookup table in correspondence with the light intensity value detected by the optical sensor. Simultaneously reading the variable duty ratio set in the second lookup table corresponding to the sensed light intensity value, and adding the read duty ratio and the variable duty ratio to generate the drive control signal having the added duty ratio. Inverter of the liquid crystal display, characterized in that for performing the second operation. 13. The method of claim 12, When the luminance control command for providing a luminance lower than a basic luminance suitable for the current ambient brightness is input, the driving controller controls the duty ratio set in the first lookup table to correspond to the light intensity value detected by the optical sensor. Read out the variable duty ratio set in the second lookup table corresponding to the sensed light intensity value at the same time, and subtract the variable duty ratio read out from the second lookup table from the duty ratio read out from the first lookup table. And performing the third operation of generating the driving control signal having the subtracted duty ratio.

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