KR101394931B1 - A liquid crystal display device and a method for driving the same - Google Patents

Abstract

The present invention relates to a liquid crystal display device and a method of driving the same that can prevent an image quality defect due to a leakage current deviation of a photoelectric conversion element and a driving method thereof, ; A current-to-voltage converter converting the photoelectric current from the photoelectric converter into a photo voltage; An analog-digital converter for converting the optical voltage from the current-voltage converter into digital data; A pulse width modulator for converting the duty ratio of the light control signal according to the digital data from the analog-to-digital converter and supplying the converted light to the backlight; And a current-to-voltage conversion circuit for outputting the current-to-voltage conversion signal according to any one of an output from the photoelectric conversion section, an output from the current-to-voltage conversion section, an output from the analog- And a control unit for controlling the output of the negative part.

Liquid crystal display device, photoelectric conversion element, photo sensor, backlight

Description

[0001] The present invention relates to a liquid crystal display device and a method of driving the same,

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device and a method of driving the same that can prevent an image quality defect due to a leakage current deviation of a photoelectric conversion element.

A liquid crystal display (LCD) displays an image by adjusting a light transmittance of liquid crystal cells according to a video signal.

Among these liquid crystal display elements, an active matrix type liquid crystal display element in which a switching element is formed for each liquid crystal cell is capable of actively controlling the switching element, which is advantageous for a moving image. A thin film transistor (hereinafter referred to as "TFT") is mainly used as a switching element used in an active matrix type liquid crystal display element.

Since such a liquid crystal display device uses a liquid crystal which is a non-luminescent material, it necessarily includes a backlight for providing light. A conventional liquid crystal display device includes a backlight control unit for changing the brightness of the backlight in accordance with light from an external environment.

The backlight control unit receives a photocurrent from a sensor, which is a photoelectric conversion element that detects external light and converts it into a photocurrent corresponding to the intensity of the light, and controls the brightness of the backlight according to the magnitude of the photocurrent.

Due to the nature of the photoelectric conversion element, there is a large leakage current deviation among elements of the same type, and therefore, a deviation may occur between liquid crystal display devices of the same product having the same photoelectric conversion element.

Therefore, a step of inspecting the photoelectric conversion element before commercialization of the liquid crystal display device is required. The inspection process may include providing the inspection light having a predetermined roughness to the photoelectric conversion element, and then determining whether the illuminance of the light emitted from the backlight is at a target value, I.e., adjusting the value of the variable resistor.

In this case, since the operator manually adjusts the variable resistor by using the adjustment rod, it takes a long time to work and it is difficult to adjust the variable resistor to an accurate value.

SUMMARY OF THE INVENTION The present invention provides a liquid crystal display device and a method of driving the same that can automatically and accurately correct an internal resistance value of a backlight control unit according to the illuminance of inspection light from the outside It has its purpose.

According to an aspect of the present invention, there is provided a liquid crystal display comprising: a photoelectric conversion unit generating a photo current according to an inspection light from outside; A current-to-voltage converter converting the photoelectric current from the photoelectric converter into a photo voltage; An analog-digital converter for converting the optical voltage from the current-voltage converter into digital data; A pulse width modulator for converting the duty ratio of the light control signal according to the digital data from the analog-to-digital converter and supplying the converted light to the backlight; And a current-to-voltage conversion circuit for outputting the current-to-voltage conversion signal according to any one of an output from the photoelectric conversion section, an output from the current-to-voltage conversion section, an output from the analog- And a control unit for controlling the output of the negative part.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display, including: generating a photo current according to an external inspection light; Converting the photocurrent into a light voltage; Converting the optical voltage into digital data; Converting a duty ratio of a light control signal according to the digital data and supplying the converted light to a backlight; and controlling the light voltage according to one of the light current, the light voltage, the digital data, And a control unit for controlling the control unit.

The liquid crystal display device and the driving method thereof according to the present invention have the following effects.

The liquid crystal display according to the present invention includes a control unit that can automatically correct a resistance value according to inspection light. Therefore, the working time can be reduced and the resistance value can be accurately corrected.

1 is a view illustrating a liquid crystal display device according to an embodiment of the present invention.

1, the liquid crystal display device according to the embodiment of the present invention includes a liquid crystal panel 111 having a display portion 111a and a non-display portion 111b, and a non-display portion 111b of the liquid crystal panel 111 A driver IC (D-IC) (Integrated Circuit) formed on the display unit 111a for supplying various signals from the outside through a flexible printed circuit (FPC) 170 and displaying an image on the display unit 111a, A backlight (not shown) positioned below the liquid crystal panel 111 and providing light to the display portion 111a side of the liquid crystal panel 111 and a backlight And a plurality of photoelectric conversion units 120 for sensing light to generate a photo current.

The liquid crystal panel 111 has a plurality of gate lines GL and a plurality of data lines DL intersecting with each other.

One pixel cell includes a thin film transistor TFT for switching a data signal from a data line DL in response to a scan pulse from a gate line GL and a thin film transistor TFT for receiving a data signal from the thin film transistor TFT A common electrode (not shown) positioned opposite to the pixel electrode, and a light-emitting layer disposed between the pixel electrode and the common electrode to adjust the light transmission amount according to an electric field generated between the two electrodes And a liquid crystal layer (not shown).

A liquid crystal capacitance capacitor Clc having the liquid crystal layer as a dielectric is formed between the common electrode and the pixel electrode, and between the pixel electrode and the front gate line GL overlapping a part of the pixel electrode, (Not shown) is made of a dielectric material is formed.

The driver IC (D-IC) includes a gate driver (not shown) for driving the gate lines GL and a data driver (not shown) for driving the data lines DL.

The gate driver includes a shift register (not shown) for sequentially generating scan pulses in response to a gate control signal from a timing controller (not shown), and a gate driver for driving the swing width of the scan pulse to drive the liquid crystal cell Clc Level shifter (not shown) for shifting the level shifter, and an output buffer (not shown) for buffering and outputting the output from the level shifter. The gate driver supplies a scan pulse to the gate line 46 to turn on the thin film transistors connected to the gate line GL to supply the pixel voltage of the data signal, that is, the analog gamma compensation voltage The pixel cells of one horizontal line are selected. Data signals generated from the data driver are supplied to the pixel cells of one horizontal line selected by being synchronized with the scan pulse.

In addition, the driver IC (D-IC) further includes a backlight control unit (not shown). The backlight control unit receives the photoelectric current from the photoelectric conversion unit 120, The intensity of light in the environment is measured, and the brightness of the backlight is adjusted according to the measured result. For example, the backlight control unit lowers the brightness of the backlight when the surroundings are bright, and increases the brightness of the backlight when the surroundings are dark.

FIG. 2 is a diagram illustrating a backlight controller 200 according to an embodiment of the present invention, and FIG. 3 is a detailed configuration diagram of the current-voltage converter 211 of FIG.

2, the photoelectric conversion unit 120 includes a photoelectric conversion element PTr that senses light from the outside and generates a photocurrent Ic according to the light intensity, .

2, the backlight controller 200 includes a current-voltage converter 211, an analog-to-digital converter (ADC), a pulse width modulator (PWM) A pulse width modulation (PWM), and a control unit 222.

The current-to-voltage conversion unit 211 converts the optical current Ic from the photoelectric conversion unit 120 into a light voltage Vc, (PWM) according to digital light data Dc from the analog-to-digital converter (ADC), converts the light voltage Vc from the light source 211 to digital data, And supplies the converted data to the backlight BL. The control unit 222 receives the photocurrent Ic from the photoelectric conversion unit 120, the light voltage Vc from the current-to-voltage conversion unit 211, And the output of the current-voltage converter 211 is controlled according to any one of the optical data Dc of the pulse width modulation unit PWM and the optical control signal CS_BL from the pulse width modulation unit PWM.

The backlight BL emits brighter light as the duty ratio of the light control signal CS_BL is higher and darker light as the duty ratio of the light control signal CS_BL is lower.

2 and 3, the current-voltage conversion unit 211 includes an operational amplifier (OPA), a resistance unit 230, and a switch SW.

A photoelectric current Ic from the photoelectric conversion unit 120 is input to the inverting terminal of the amplifier OPA and an offset voltage Voffset is input to the non-inverting terminal of the amplifier OPA.

The resistor 230 includes a plurality of resistors R connected in parallel as shown in FIG. 3. One terminal of each resistor R is connected to the inverting terminal (-) of the amplifier OPA, ). The resistors R have different resistance values.

The switch SW electrically connects one terminal of the plurality of resistors R and the output terminal of the amplifier OPA in accordance with a switch control signal CS_SW from the controller 222.

4 is a detailed configuration diagram of the control unit 222 of FIG.

The control unit 222 includes a comparison unit 411, a selection unit 412, a storage unit 413, and a switch control unit 414, as shown in FIG.

The comparator 411 compares a preset reference value with the value of the output from the analog-to-digital converter (ADC) according to the inspection light, and the selector 412 selects the reference value from the comparator 411 The switch control unit 414 selects one of the previously stored correction values according to the comparison result and stores the selected correction value in the storage unit 413. The switch control unit 414 switches the switch SW based on the correction value stored in the storage unit 413 And generates a switch control signal CS_SW for controlling the switch control signal CS_SW.

The selector 412 includes a lookup table 512 and a correction value selector 522.

The lookup table 512 stores a difference value between the output value from the analog-to-digital converter (ADC) and the reference value, and a plurality of correction values corresponding to the difference values. 5 shows the correction values stored in the look-up table 512. As shown in FIG. 5, each digital correction value represents a resistance value of each resistance R. FIG.

The correction value selection unit 522 selects one correction value from the lookup table 512 based on the difference value from the comparison unit 411 and outputs the selected correction value to the storage unit 413 .

The driving method of the liquid crystal display device according to the present invention and the method of correcting the leakage current deviation in the liquid crystal display device having such a structure will now be described.

First, the inspection light having an arbitrary roughness is irradiated to the photoelectric conversion element PTr. Then, the photoelectric conversion element PTr generates a photocurrent Ic corresponding to the intensity of the inspection light, and supplies it to the inverting terminal (-) of the amplifier OPA.

Then, the amplifier OPA converts the photo current Ic from the photoelectric conversion element PTr into the light voltage Vc. At this time, a pre-selected resistor R is provided between the inverting terminal (-) and the output terminal of the amplifier OPA. The pre-selected resistance R has a resistance value selected under the condition that the leakage current of the photoelectric conversion element PTr is within an allowable reference value, and the digital correction value corresponding to the resistance value is stored in the storage section 413 ) Is stored in a default state in advance. The optical voltage Vc output from the amplifier OPA is input to the analog-to-digital converter ADC.

The analog-to-digital converter ADC converts the optical voltage Vc, which is an analog signal, into optical data Dc, which is a digital signal, and supplies the optical data Dc to the pulse width modulator PWM. Then, the pulse width modulation unit PWM adjusts the duty ratio of the light control signal CS_BL according to the magnitude of the optical data Dc. For example, if the value of the optical data Dc is large, bright light is emitted, and if the value of the optical data Dc is small, dark light can be emitted.

On the other hand, the comparator 411 receives the optical data Dc from the analog-to-digital converter (ADC) and compares the optical data Dc with preset reference values. The reference value is a digital value set according to the illuminance of the inspection light.

Hereinafter, the operation of the comparator 411 when a difference between the optical data Dc and the reference value occurs, that is, when the default value of the resistance value is incorrect, will be described.

That is, the comparator 411 calculates the difference between the optical data Dc and the reference value, and supplies the calculated value to the correction value selector 522. The correction value selection unit 522 selects a correction value corresponding to the calculated value from the lookup table 512 and stores the selected correction value in the storage unit 413. [ Accordingly, the correction value stored in the storage unit 413 as a default is replaced with a new correction value. The switch control unit 414 controls the switch SW so that the resistor R having a resistance value corresponding to the new correction value stored in the storage unit 413 is selected.

On the other hand, when there is no difference between the optical data Dc and the reference value (when the calculated value is 0), that is, when the default value of the resistance value is correct, the comparator 411 performs one of the following two operations Can be performed.

First, the comparator 411 calculates a difference between the optical data Dc and the reference value, that is, a value of 0, and supplies the calculated value to the correction value selector 522. The correction value selection unit 522 selects the correction value corresponding to the calculated value, that is, 0, from the look-up table 512, and stores the selected correction value in the storage unit 413. The selected correction value is finally the same as the correction value previously stored in the storage unit 413.

Secondly, the comparator 411 compares the size of the optical data Dc with the reference value, and if there is no difference between the optical data Dc and the reference value, the comparator 411 does not proceed to the next operation. In other words, the comparator 411 does not output any control signal for operating the correction value selector 522. [ Accordingly, the correction value previously stored in the storage unit 413 is maintained. At this time, a separate correction value for 0 need not be stored in the look-up table 512.

The storage unit 413 may be an EEPROM (Electrically Erasable and Programmable Read Only Memory). The storage unit 413 must be supplied with the operating power PO and the write signal WS from the outside, The correction value provided from the value selection unit 522 can be stored. However, if the operating power (PO) and the writing signal (WS) are not supplied, the previously stored correction value is maintained even if the correction value is supplied from the correction value selection unit 522. [

Accordingly, after the correct correction value is stored in the storage unit 413, the operation power source PO and the write signal WS are interrupted so that the correction value is not changed to another value.

In the present invention, the controller 222 typically controls the value of the resistor R using the optical data Dc from the analog-to-digital converter (ADC) The control unit 222 controls the operation of the resistor R using either the light voltage Vc from the current-to-voltage conversion unit 211 or the light control signal CS_BL from the pulse width modulation unit PWM. You can also control the value.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. Will be clear to those who have knowledge of.

1 is a view illustrating a liquid crystal display device according to an embodiment of the present invention.

2 is a diagram illustrating a backlight control unit according to an embodiment of the present invention;

3 is a detailed configuration diagram of the current-voltage conversion unit of FIG.

4 is a detailed configuration diagram of the control unit of FIG.

5 is a view showing correction values stored in a look-up table

Claims (9)

A photoelectric conversion unit for generating a photo current according to an inspection light from the outside; A current-to-voltage converter converting the photoelectric current from the photoelectric converter into a photo voltage; An analog-digital converter for converting the optical voltage from the current-voltage converter into digital data; A pulse width modulator for converting the duty ratio of the light control signal according to the digital data from the analog-to-digital converter and supplying the converted light to the backlight; And And an output of the current-to-voltage conversion unit according to any one of an output from the photoelectric conversion unit, an output from the current-voltage conversion unit, an output from the analog-to-digital conversion unit, And a control unit for controlling the control unit; The current-voltage converter An amplifier receiving the photoelectric current from the photoelectric conversion unit through an inverting terminal and receiving an offset voltage through a non-inverting terminal; A plurality of resistors to which the terminals are connected in common to the inverting terminal; And a switch for electrically connecting the other one of the plurality of resistors to an output terminal of the amplifier according to an output from the control unit. delete The method according to claim 1, Wherein, A comparator for comparing a reference value previously set according to the inspection light with a value of an output from the analog-digital converter; A selection unit for selecting one of the previously stored correction values according to the comparison result from the comparison unit and storing the selected correction value in the storage unit; And And a switch controller for controlling the switch based on the correction value stored in the storage unit. The method of claim 3, Wherein the selection unit comprises: A look-up table storing a difference between an output value from the analog-to-digital converter and the reference value, and a plurality of correction values corresponding to the difference values; And And a correction value selection unit for selecting a correction value from the look-up table based on a difference value from the comparison unit, and storing the selected correction value in the storage unit. The method of claim 3, Wherein the storage unit is an EEPROM (Electrically Erasable and Programmable Read Only Memory). Generating a photo current according to an inspection light from the outside; Converting the photocurrent into a light voltage; Converting the optical voltage into digital data; Converting a duty ratio of a light control signal according to the digital data and supplying the converted light to a backlight; Controlling the optical voltage according to any one of the photocurrent, the optical voltage, the digital data, and the optical control signal; Wherein an amplifier having a plurality of resistors arranged in a bottle between an inverting terminal and an output terminal is used to convert the photocurrent into a light voltage, Inputting a photocurrent to an inverting terminal of the amplifier; Inputting an offset voltage to a non-inverting terminal of the amplifier, Selecting any one of the plurality of resistors according to any one of the photocurrent, the optical voltage, the digital data, and the optical control signal, and electrically connecting the inverted terminal and the output terminal to each other And a driving method of the liquid crystal display device. delete The method according to claim 6, Wherein the step of controlling the optical voltage comprises: Comparing a preset reference value and a value of the digital data according to the inspection light; And Further comprising the step of selecting any one of the resistors and electrically connecting the inverted terminal and the output terminal according to the comparison result. 9. The method of claim 8, Selecting one of the resistors and electrically connecting the inverting terminal and the output terminal according to a result of the comparison, Setting and storing a difference value between the digital data value and the reference value and a plurality of correction values corresponding to the difference value; Selecting a correction value based on the difference value generated according to the comparison result, and storing the selected correction value; And And selecting one of the resistors based on the selected and stored correction value to electrically connect the inversion terminal and the output terminal.

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