KR20080051634A - Image display apparatus and drive method thereof - Google Patents

Abstract

An image display apparatus and a driving method thereof are provided to adjust precisely brightness by supplying selectively gamma reference voltages in proportion to the intensity of the ambient visible rays. An image display apparatus includes first to i-th gamma reference voltage generators(140-1,-,140-i), a gamma controller(160), and a data driver(120). The first to i-th gamma reference voltage generators generate first to i-th gamma reference voltages, respectively. The gamma controller selectively supplies a gamma control signal which instructs the supply of gamma reference voltage to the first to i-th gamma reference voltage generators according to the intensity of the ambient visible rays. The data driver supplies a data voltage corresponding to the level of the selected gamma reference voltage among the first to i-th gamma reference voltages to the display panel. The first to i-th gamma reference voltage generators supply gamma reference voltages to the data driver whenever the gamma control signal is inputted.

Description

Image display apparatus and drive method

1 is an equivalent circuit diagram of pixels of a liquid crystal display device.

2 is an equivalent circuit diagram of pixels of an organic light emitting diode display.

3 is a block diagram of an image display apparatus according to an embodiment of the present invention.

4 is an optical characteristic diagram of an organic light emitting diode.

5 is a photocurrent characteristic diagram of an organic light emitting diode.

6 is a perspective view of an image display device according to an embodiment of the present invention.

7 is an exploded perspective view of an image display device according to an embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

100: image display device 110: display panel

120: data driver 130: gate driver

140-1 to 140-i: first to i-th gamma reference voltage generator

150: timing controller 160: gamma controller

161: organic light emitting diode sensor 162: current / voltage conversion unit

163: A / D converter 164: gamma control unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image display device such as an organic light emitting diode display device and a liquid crystal display device, and more particularly, to an image display device and a driving method thereof capable of accurately adjusting luminance in proportion to the surrounding visible light intensity.

A liquid crystal display device displays an image by adjusting 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 element. This is advantageous for video implementation. As the switching element used in the active matrix liquid crystal display device, a thin film transistor (hereinafter referred to as TFT) is mainly used as shown in FIG. 1.

Referring to FIG. 1, an active matrix type liquid crystal display converts digital input data into an analog data voltage based on a gamma reference voltage and supplies it to the data line DL and simultaneously supplies scan pulses to the gate line GL. The liquid crystal cell Clc is charged.

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

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

The storage capacitor Cst charges a data voltage applied from the data line DL when the TFT is turned on, thereby maintaining a constant voltage of the liquid crystal cell Clc. When the 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 so that the voltage on the data line DL is applied to the pixel electrode of the liquid crystal cell Clc. Supply. At this time, the liquid crystal molecules of the liquid crystal cell Clc modulate the incident light by changing the arrangement by the electric field between the pixel electrode and the common electrode.

A conventional image display apparatus having pixels having such a structure generates a gamma reference voltage for determining a data gray level regardless of ambient light intensity, thereby providing a screen having a constant brightness regardless of ambient brightness. Accordingly, the conventional liquid crystal display device has a problem that the luminance of the screen is relatively low in a dark environment compared to a bright environment.

An organic light-emitting diode ("EL") display device is a self-luminous device that emits a phosphor by recombination of electrons and holes, and uses an inorganic EL and an organic compound using an inorganic compound as the phosphor. It is roughly classified into organic EL. Such EL display devices have many advantages such as low voltage driving, self-luminous, thin film type, wide viewing angle, fast response speed and high contrast, and are expected to be the next generation display devices.

An organic EL display device usually consists of an electron injection layer, an electron transport layer, a light emitting layer, a hole transport layer, and a hole injection layer stacked between a cathode and an anode. In such an organic EL display device, when a predetermined voltage is applied between the anode and the cathode, electrons generated from the cathode move to the light emitting layer through the electron injection layer and the electron transport layer, and holes generated from the anode are transferred to the hole injection layer and the hole transport layer. It moves to the light emitting layer through. Accordingly, the light emitting layer emits light by recombination of electrons and holes supplied from the electron transporting layer and the hole transporting layer.

A circuit configuration of a general organic light emitting diode display device using the organic EL will be described with reference to FIG. 2.

2 is an equivalent circuit diagram of pixels constituting a general organic light emitting diode display.

Referring to FIG. 2, each pixel of the organic light emitting diode display device is turned on by a scan pulse supplied through the gate line GL to switch the data voltage supplied through the data line DL. ) And an organic light emitting diode which is turned on and emits light by a storage capacitor Cst for charging a data voltage supplied through the switch transistor S_TR1, and a driving current supplied from a power terminal to which a high potential power voltage VDD is applied. A diode OLED and a driving transistor D_TR1 for turning on by the data voltage supplied through the switch transistor S_TR1 or the charging voltage of the storage capacitor Cst to drive the organic light emitting diode OLED are provided.

The switch transistor S_TR1 is an NMOS transistor having a gate connected to the gate line GL, a drain connected to the data line DL, and a source connected in common to the storage capacitor Cst and the gate of the driving transistor D_TR1. . The switch transistor S_TR1 is turned on by a scan pulse supplied through the gate line GL to transmit the data voltage supplied through the data line DL to the gates of the storage capacitor Cst and the driving transistor D_TR1. Supply.

One side of the storage capacitor Cst is commonly connected to the gates of the switch transistor S_TR1 and the driving transistor D_TR1, and the other side thereof is connected to ground, and is charged by the data voltage supplied through the switch transistor S_TR1. The storage capacitor Cst has its own charging voltage when the data voltage being supplied through the switch transistor S_TR1 is not applied to the gate of the driving transistor D_TR1, that is, when the gate voltage of the driving transistor D_TR1 is lowered. Is discharged to hold the gate voltage of the driving transistor D_TR1. Accordingly, the driving transistor D_TR1 is turned on by the charging voltage of the storage capacitor Cst during the holding period by the storage capacitor Cst even when the supply of the data voltage supplied through the switch transistor S_TR1 is stopped. do.

The organic light emitting diode OLED has an anode connected to a power supply terminal to which a high potential power supply voltage VDD is applied, and a cathode connected to a drain of the driving transistor D_TR1.

The driving transistor D_TR1 is an NMOS transistor having a source connected to the switch transistor S_TR1, a gate connected to the switch transistor S_TR1, a drain connected to the cathode of the organic light emitting diode OLED, and a source connected to ground. The driving transistor D_TR1 is turned on by the data voltage supplied to the gate through the switch transistor S_TR1 or the charging voltage of the switch transistor S_TR1 supplied to the gate to ground the driving current flowing through the organic light emitting diode OLED. The organic light emitting diode OLED is allowed to emit light by the driving current generated by the high potential power voltage VDD.

A conventional organic light emitting diode display having pixels having such an equivalent circuit generates a gamma reference voltage that determines a data gray level regardless of ambient light intensity, thereby providing a screen having a constant brightness regardless of ambient brightness. do. Accordingly, the conventional organic light emitting diode display has a problem that the luminance of the screen is relatively low in a dark environment compared to a bright environment.

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 gamma reference voltage of a level proportional to the intensity of visible light among the multiple levels of gamma reference voltages for determining the gray level of the data voltage. There is provided an image display apparatus which can be selectively supplied, and a driving method thereof.

SUMMARY OF THE INVENTION An object of the present invention is to provide a video display device and a driving method thereof by selectively supplying a gamma reference voltage of a level proportional to the ambient visible light intensity, thereby accurately adjusting the luminance in proportion to the ambient brightness recognized by the user. have.

The present invention for achieving the above object, the first to i-gamma reference voltage generator for generating the first to i-gamma reference voltage, respectively; A gamma controller configured to alternatively supply a gamma control signal for supplying a gamma reference voltage to the first to i-th gamma reference voltage generators according to ambient visible light intensity; And a data driver configured to supply a data panel having a level corresponding to a level of the gamma reference voltage supplied among the first to i gamma reference voltages to the display panel, wherein the first to ith gamma reference voltage generators Each time the gamma control signal is input, a gamma reference voltage is supplied to the data driver.

The gamma controller may include: an organic light emitting diode sensor configured to generate a visible light sensing current indicating a sensed monitoring light intensity by sensing an ambient visible light intensity; A current / voltage converter for converting the visible light sensing current output from the organic light emitting diode sensor into an analog visible light sensing voltage; An A / D converter for converting the analog visible light sensing voltage converted by the current / voltage converter into a digital visible light sensing voltage; And a gamma control unit for selectively supplying the gamma control signal to the first to i-th gamma reference voltage generators according to the magnitude of the digital visible light detection voltage converted by the A / D converter.

The gamma control unit may include a lookup table in which a digital visible light detection voltage corresponding to the first to i-th gamma reference voltages is constructed one-to-one.

When the digital visible light sensing voltage is input from the A / D converter, the gamma control unit searches the lookup table to find a gamma reference voltage mapped with the input digital visible light sensing voltage, and then instructs the supply of the gamma reference voltage. The gamma control signal may be supplied to any one of the first to i-th gamma reference voltage generators.

The gamma control unit supplies a gamma reference voltage mapped to the digital visible light detection voltage approximating the input digital visible light detection voltage if the gamma reference voltage exactly mapped to the input digital visible light detection voltage is not present in the lookup table. It is characterized by indicating.

A method of driving an image display apparatus according to the present invention may include generating first to i-th gamma reference voltages; Generating a gamma control signal instructing supply of one of the first to i-th gamma reference voltages according to the ambient visible light intensity; Supplying a gamma reference voltage indicated by the gamma control signal to the data driver among the generated first to ith gamma reference voltages; And supplying, to the display panel, the data driver having a level corresponding to the level of the gamma reference voltage supplied according to the gamma control signal.

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

3 is a block diagram of an image display apparatus according to an embodiment of the present invention.

Referring to FIG. 3, in the image display apparatus 100 of the present invention, a plurality of data lines DL1 to DLm and a plurality of gate lines GL1 to GLn cross each other, and are defined by intersections thereof. A display panel 110 having pixels disposed in the display panel, a data driver 120 for supplying a data voltage to the data lines DL1 to DLm of the display panel 110, and a gate line of the display panel 110. Gate driver 130 for supplying scan pulses to the fields GL1 to GLn, and first to i-gamma reference voltage generators 140-1 to 140- for generating the first to i-th gamma reference voltages, respectively. i) and a timing controller 150 for controlling the data driver 120 and the gate driver 130.

In addition, the image display apparatus 100 of the present invention may provide a gamma control signal for supplying a gamma reference voltage to the first to i-th gamma reference voltage generators 140-1 to 140-i according to the visible light intensity of the surroundings. Gamma controller 160 that supplies alternatively).

The display panel 110 is implemented by stacking an upper glass substrate and a lower glass substrate, and in particular, the data lines DL1 to DLm and the gate lines GL1 to GLn are orthogonal to the lower glass substrate. Here, pixels are formed in the cell regions defined by the intersections of the data lines DL1 to DLm and the gate lines GL1 to GLn, and each pixel is driven by a scan pulse supplied through the gate line GL. The gray level of the data supplied through the data line DL is implemented. The gray level of the data supplied to each pixel is a brightness value of the screen, that is, the brightness of the screen is determined by the gray level of the data supplied from the data driver 120. Since the gradation level of this data coincides with the level of the gamma reference voltage alternatively supplied from the first to i-th gamma reference voltages, the brightness of the screen is substantially adjusted by the level of the gamma reference voltage. Accordingly, the present invention intends to adjust the brightness of the screen according to the visible light intensity by supplying the first to i-th gamma reference voltages to the data driver 120 in accordance with the ambient light intensity.

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 150, and digital video data supplied from the timing controller 150. After sampling and latching (RGB), an analog data voltage having a level corresponding to a level of a gamma reference voltage which is alternatively supplied among the first to i-th gamma reference voltages is supplied 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 150, 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 (not shown).

The first to i-gamma reference voltage generators 140-1 to 140-i are programmable gamma elements and generate first to i-gamma reference voltages according to a gamma program set therein, respectively, and are gamma controllers. Each time a gamma control signal is input from the 160, a gamma reference voltage generated by the gamma control signal is supplied to the data driver 120. Here, the first to i-gamma reference voltages have different levels, and for example, the present invention may be implemented such that the levels are increased in order from the first gamma reference voltage to the i-gamma reference voltage.

The timing controller 150 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. 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, and a gate driving control signal GDC. ) Includes a gate start pulse (GSP) and a gate output enable (GOE).

The gamma controller 160 senses the visible light intensity around the organic light emitting diode sensor 161 generating a visible light sensing current indicating the detected light intensity and the visible light output from the organic light emitting diode sensor 161. A current / voltage converter 162 for converting the sensed current into an analog visible light detection voltage, and A for converting the analog visible light sense voltage converted by the current / voltage converter 162 into a digital visible light sense voltage. The first to i-th gamma reference voltage generators 140-1 to 140-i according to the magnitude of the digital visible light detection voltage converted by the / D converter 163 and the A / D converter 163. Gamma control unit 164 to be supplied alternatively).

The organic light emitting diode sensor 161 detects only the intensity of visible light among the surrounding light irradiated onto the image display apparatus 100, for example, ultraviolet light, infrared light, and visible light, and generates a visible light sensing current indicating the detected monitoring light intensity. .

Typically, the organic light emitting diode does not generate ultraviolet rays and infrared rays, as shown in FIG. 4, and emits light in the visible wavelength range, for example, white light, blue light, green light and red light. Occurs. The organic light emitting diode sensor 161 implemented as an organic light emitting diode having such optical characteristics does not detect ultraviolet rays and infrared rays from the surrounding natural light, but detects only light in the visible wavelength range, that is, visible light.

As shown in FIG. 5, the organic light emitting diode sensor 161 having the optical characteristics has a linear photocurrent characteristic compared to the ambient illumination sensed. In FIG. 5, the line segment L1 having a large slope shows photocurrent characteristics with respect to illuminance when a reverse bias of 10 V is applied to the organic light emitting diode sensor 161, and the line segment L2 having a small slope has an organic light emitting diode sensor 161. When the reverse bias of 5V is applied to), it shows the photocurrent characteristics compared to illuminance. That is, FIG. 5 shows that the organic light emitting diode sensor 161 can be used as a sensor because the organic light emitting diode sensor 161 has a characteristic of a linear photocurrent with respect to ambient illumination.

In contrast, a photodiode sensor (not shown) has a characteristic of detecting all ultraviolet light, infrared light and visible light of natural light. Accordingly, when detecting the light intensity of the surroundings irradiated to the image display device 100 by using the photodiode sensor, the photodiode sensor detects all the ultraviolet, infrared and visible light of the surrounding and detected the detected ultraviolet, infrared and visible Generates a voltage proportional to the light intensity.

Humans recognize the same brightness by fluorescent lamps that generate only visible light and the brightness by ultraviolet light, infrared light, and natural light that generate visible light.However, when the fluorescent light and the natural light show the same brightness, the photodiode sensor uses ultraviolet, infrared, and It detects all visible light, making natural light brighter than fluorescent lamps. When the ambient light intensity of the image display apparatus 100 is sensed using a photodiode sensor having such optical characteristics, when the image display apparatus 100 is exposed to natural light, it is recognized to be brighter than the brightness of a fluorescent lamp. Accordingly, when the ambient light intensity is sensed using a photodiode sensor and the level of the gamma reference voltage is selectively supplied according to the detected light intensity, the brightness is adjusted. The photodiode sensor recognizes the brightness brighter than the brightness, and thus has a disadvantage in that the brightness of the screen cannot be accurately adjusted in proportion to the brightness recognized by the user.

In order to solve the disadvantage of the photodiode sensor, the present invention is to detect the ambient light intensity of the image display device 100 using the organic light emitting diode sensor 161 that detects only visible light that affects the user's brightness recognition. Implement Accordingly, the present invention detects only visible light through the organic light emitting diode sensor 161 even when the image display apparatus 100 is exposed to natural light, thereby accurately adjusting the brightness of the screen in proportion to the brightness recognized by the user. .

The current / voltage converter 162 converts the visible light sensing current output from the organic light emitting diode sensor 161 into an analog visible light sensing voltage and outputs it to the A / D converter 163.

The A / D converter 163 converts the analog visible light detection voltage converted by the current / voltage converter 162 into a digital visible light detection voltage and outputs it to the gamma control unit 164.

The gamma control unit 164 transmits the gamma control signal to the first to i-th gamma reference voltage generators 140-1 to 140-i according to the magnitude of the digital visible light detection voltage converted by the A / D converter 163. Alternatively, the gamma reference voltage having a level proportional to the ambient light intensity is supplied to the data driver 120. The gamma controller 164 is configured with a lookup table in which digital visible light detection voltages corresponding to the first to i-th gamma reference voltages are constructed one-to-one. Here, the digital visible light detection voltages set in the predetermined lookup table are increased in proportion to the gamma reference voltages mapped thereto.

When the digital visible light detection voltage is input from the A / D converter 163, the gamma control unit 164 searches a predetermined lookup table to find a gamma reference voltage mapped with the input digital visible light detection voltage, and then calculates the gamma reference voltage. Generates a gamma control signal instructing supply. Here, if there is no gamma reference voltage mapped correctly with the input digital visible light sensing voltage, the gamma control unit 164 instructs the supply of the gamma reference voltage mapped with the digital visible light sensing voltage approximating the input digital visible light sensing voltage. do.

For example, if the gamma reference voltage mapped to the input digital visible light detection voltage is the first gamma reference voltage, the gamma control unit 164 supplies the gamma control signal only to the first gamma reference voltage generator 140-1. The first gamma reference voltage is supplied to the data driver 120. In this case, the data driver 120 supplies the data voltages of the level corresponding to the level of the first gamma reference voltage to the data lines DL1 to DLm.

6 is an exploded perspective view of an image display device according to an exemplary embodiment of the present invention.

Referring to FIG. 6, a display panel 110, an organic light emitting diode sensor 161, and an integrated circuit 620 are mounted on a glass substrate 610.

In the integrated circuit 620, a current / voltage converter 162 and an A / D converter 163 are integrated.

The first to i-gamma reference voltage generators 140-1 to 140-i and the gamma controller 164 are mounted on a printed circuit board (PCB) 630 spaced apart from the glass substrate 610. do.

A flexible printed circuit board (FPCB) 640 is disposed between the display panel 110 and the circuit board 630 to electrically connect the two devices 110 and 630. The FPCB 640 includes data. The driver 120 is mounted.

In the case of combining such circuit elements, a module of an image display apparatus according to the present invention is implemented as shown in FIG. 7.

As described above, according to the present invention, by selectively supplying a gamma reference voltage having a level proportional to the ambient visible light intensity, the luminance can be accurately adjusted in proportion to the ambient brightness recognized by the user.

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

Claims (10)

First to i-th gamma reference voltage generators for generating first to i-th gamma reference voltages, respectively; A gamma controller configured to alternatively supply a gamma control signal for supplying a gamma reference voltage to the first to i-th gamma reference voltage generators according to ambient visible light intensity; And A data driver configured to supply a data voltage having a level corresponding to a level of the gamma reference voltage supplied among the first to i gamma reference voltages to the display panel; And a first gamma reference voltage generator supplying a gamma reference voltage to the data driver whenever the gamma control signal is input. The method of claim 1, The gamma controller, An organic light-emitting diode sensor which detects the visible light intensity of the surroundings and generates a visible light sensing current indicating the detected light intensity; A current / voltage converter for converting the visible light sensing current output from the organic light emitting diode sensor into an analog visible light sensing voltage; An A / D converter for converting the analog visible light sensing voltage converted by the current / voltage converter into a digital visible light sensing voltage; And A gamma control unit for selectively supplying the gamma control signal to the first to i-th gamma reference voltage generators according to the magnitude of the digital visible light detection voltage converted by the A / D converter Image display device comprising a. The method of claim 2, And a lookup table in which the digital visible light sensing voltage corresponding to the first to i-th gamma reference voltages is constructed in the gamma control unit. The method of claim 3, wherein When the digital visible light detection voltage is input from the A / D converter, the gamma control unit searches the lookup table to find a gamma reference voltage mapped with the input digital visible light detection voltage, and then indicates a gamma reference voltage supply. And a control signal is supplied to any one of the first to i-th gamma reference voltage generators. The method of claim 4, wherein The gamma control unit supplies a gamma reference voltage mapped to the digital visible light detection voltage approximating the input digital visible light detection voltage if the gamma reference voltage exactly mapped to the input digital visible light detection voltage is not present in the lookup table. And an image display device for indicating. Generating first to i-th gamma reference voltages; Generating a gamma control signal instructing supply of one of the first to i-th gamma reference voltages according to the ambient visible light intensity; Supplying a gamma reference voltage indicated by the gamma control signal to the data driver among the generated first to ith gamma reference voltages; And Supplying, to the display panel, a data voltage having a level corresponding to the level of the gamma reference voltage supplied according to the gamma control signal; Driving method of an image display device comprising a. The method of claim 6, The generated first to i th gamma reference voltages are alternatively selected by the gamma control signal and supplied to the data driver. The method of claim 6, The gamma control signal generation step, Generating a visible light sensing current indicative of the detected visible light intensity by sensing ambient light intensity; Converting the visible light sensing current into an analog visible light sensing voltage; Converting the analog visible light detection voltage into a digital visible light detection voltage; And Generating the gamma control signal according to the magnitude of the digital visible light detection voltage Driving method of an image display device comprising a. The method of claim 8, In the gamma control signal generation step, And searching a predetermined lookup table to find a gamma reference voltage mapped with the digital visible light detection voltage and generating the gamma control signal instructing the supply of the gamma reference voltage. The method according to any one of claims 6 to 9, In the visible light detection step, A method of driving an image display device, characterized by sensing the intensity of visible light in the vicinity of the organic light emitting diode sensor.

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