KR101451293B1 - Backlight illumination control method, backlight illumination control circuit and display device comprising the backlight illumination control circuit - Google Patents

Abstract

The method of controlling the backlight illuminance according to the present invention is a method of adjusting the backlight illuminance by generating a sinusoidal current signal that does not depend on a temperature change, adjusting a backlight illuminance based on the generated illuminance signal, And generates a light intensity control signal by removing the temperature dependency through the photocurrent signal or the sample light extraction current signal and the sampled timing signal, and adjusts the backlight illuminance through the light intensity control signal.

The backlight illuminance control circuit according to the present invention includes a photocurrent sensing element and a dark current sensing element, and is configured to enable the backlight illuminance adjustment method.

The display device according to the present invention includes a display panel including the backlight illuminance adjusting circuit and a backlight whose illuminance is adjusted by the backlight illuminance adjusting circuit, and the display panel includes a light blocking area formed with an open part, Is exposed to external light through the open portion and the dark current sensing element is configured to be shielded from external light.

When the backlight illuminance control method or the backlight illuminance control circuit according to the present invention is applied to a display device, the fluctuation of the backlight illuminance by the other parameters other than the external illuminance is minimized, and high reliability can be ensured.

Liquid crystal display, backlight, photo sensor, photo sensing, illumination control, calibration

Description

BACKLIGHT ILLUMINATION CONTROL METHOD, BACKLIGHT ILLUMINATION CONTROL CIRCUIT AND DISPLAY DEVICE COMPRISING THE BACKLIGHT ILLUMINATION CONTROL CIRCUIT BACKLIGHT ILLUMINATION CONTROL METHOD, BACKLIGHT ILLUMINATION CONTROL CIRCUIT AND DISPLAY DEVICE COMPRISING THE BACKLIGHT ILLUMINATION CONTROL CIRCUIT BACKLIGHT ILLUMINATION CONTROL METHOD,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device including a backlight illuminance adjusting method, a backlight illuminance adjusting circuit, and a backlight illuminance adjusting circuit, and more particularly, The present invention relates to a backlight illuminance adjusting method for minimizing illuminance fluctuation caused by other variables, a backlight illuminance adjusting circuit, and a backlight illuminance adjusting circuit.

2. Description of the Related Art Recently, a liquid crystal display device has been proposed in which an illuminance of external light is measured through a light sensing unit built in a panel to control light intensity emitted from a backlight module, thereby ensuring optimal display characteristics and minimizing power consumption.

FIG. 1 is a schematic diagram of a conventional backlight illuminance control circuit, and FIGS. 2A, 2B, 3A, and 3B illustrate signal waveforms input to the optical sensor and the optical sensor according to the related art.

1, the backlight illuminance control circuit according to the related art includes an optical sensing unit 410, an amplifier 420, a sampler 430, a signal converter 440 And an arithmetic unit 450. 2A, the optical sensors 411 to 414 may be composed of a photocurrent sensing device QLT and a switching device QSW as shown in FIG. 2A. In this case, (QLT).

Referring to FIGS. 1, 2A, and 2B, the operation of the conventional backlight illuminance adjusting circuit will be briefly described below.

When light is first applied to the channel semiconductor of the photocurrent sensing device (QLT), a part of electrons of the valence band rise to the conduction band and become free electrons. At this time, when the switching element control signal VSW is inputted to the control electrode of the switching element QSW, the channel of the switching element QSW is opened and when the light sensing part output control switch SLO is turned on, Due to the electromotive force, the photocurrent (I (Temp, Lux)) is output as a detection signal.

The amplifier 420 generates the amplified sampled voltage VS in the sampler 430 through the sensing signal transmitted from the optical sensing unit 410. The sampler 430 appropriately extracts the sampled voltage VS according to the sampling timing signal? And outputs it to the signal converter 440.

The signal converter 440 includes a plurality of comparators. The signal converter 440 receives the sampled voltage VS in the analog state extracted from the sampler 430 and converts the sampled voltage into a digital sampled signal SDS. The calculator 450 sequentially receives the four digital sample signals SDS corresponding to the detection signals of the photo-sensing elements 411 to 414 in units of predetermined time units, stores them in a memory device such as a register, (SDS), determines the dominant value as the current external illuminance, and changes the level or state of the brightness control signal (VDim) to the backlight control unit. The backlight control unit adjusts the brightness of the backlight according to the brightness control signal (VDim), thereby ensuring optimal visibility according to the change in external illuminance and reducing power consumption.

However, this prior art does not take into consideration the fact that the output value of the optical sensor fluctuates with the temperature as a variable, and the deviation of the output value of the optical sensor from each product is not taken into consideration. As time passes, There is a problem that a phenomenon in which the output value is changed is not considered.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a backlight illuminance adjusting method, a backlight illuminance illuminance adjusting circuit, and a backlight illuminance adjusting circuit that minimizes variations in backlight illuminance caused by other variables such as external temperature change, product deviation, And a display device.

The backlight illuminance adjusting method according to the present invention is a method for adjusting a backlight illuminance by controlling a backlight illuminance based on a light intensity signal generated based on a light intensity signal that does not depend on a temperature change, After the signal is generated, the light intensity signal is generated by removing the temperature dependency through the photocurrent signal or the photocurrent signal and the sampled timing signal, and the backlight illuminance is adjusted through the generated light intensity signal.

In the case of using a forward light current signal which does not depend on a temperature change, the backlight illuminance adjusting method according to the present invention includes the steps of setting a reference voltage, Generating a sample voltage based on the voltage, generating a roughness adjustment signal based on the sampled voltage, and adjusting the roughness of the backlight using the roughness adjustment signal.

The step of generating the illumination control signal may include generating a digital sample signal by converting the sampled voltage of the analog state, storing the digital sample signal, and outputting a dominant value or an average value The method comprising the steps of: setting the reference voltage; generating the sampled voltage; generating the digital sample signal; and storing the digital sample signal. Is repeated a plurality of times, and the step of generating the illuminance adjustment signal is performed.

In the case of using a photocurrent signal or a pure current signal depending on a temperature change, the method of adjusting the backlight illuminance according to the present invention includes the steps of calibrating a sampling timing signal, setting a reference voltage, setting a photocurrent sensing element and / Generating a sample voltage based on the reference voltage through a photocurrent signal or a positive current signal formed by the device, generating a roughness control signal using the sampled voltage and the sampling timing signal, To adjust the illuminance of the backlight.

The step of generating the illumination control signal may include generating a digital sample signal by converting the sampled voltage of the analog state, storing the digital sample signal, and outputting a dominant value or an average value The method comprising the steps of: setting the reference voltage; generating the sampled voltage; generating the digital sample signal; and storing the digital sample signal. Is repeated a plurality of times, and the step of generating the illuminance adjustment signal is performed.

The step of calibrating the sampling timing signal may include the steps of: setting a reference voltage; generating a calibration voltage based on the reference voltage using a dark current signal formed by the dark current sensing element; Generating a digital calibration signal, generating a coded signal by encoding the digital calibration signal, and generating a sample extraction timing signal corresponding to the coded signal.

Next, the backlight illuminance adjusting circuit according to the present invention may be configured to adjust the illuminance of the backlight through the illuminance adjusting signal generated on the basis of the generated negative light-emitting current signal which does not depend on the temperature change, A photocurrent signal or a photocurrent signal is generated, and then a photocurrent signal or a photocurrent signal and a sampling timing signal are used to generate a roughness adjustment signal from which the temperature dependency is removed, and then the backlight roughness is adjusted through this.

The backlight illuminance control circuit according to the present invention includes a light sensing unit including a photocurrent sensing element and a dark current sensing element and outputting a non-temperature- An amplifier for fixing the voltage of the output terminal of the optical sensing unit and receiving the output signal of the optical sensing unit and amplifying the amplified output signal, a sampler connected to the output terminal of the amplifier for generating and outputting a sampled voltage, And an analog-to-digital converter for receiving and outputting the digital sample signal.

The optical sensing unit may include a photocurrent sensing unit and a dark current sensing unit. The photocurrent sensing unit may include a photocurrent sensing unit and a dark current sensing unit. The photocurrent sensing unit may include a photocurrent sensing unit and a dark current sensing unit. And a plurality of optical sensors.

The backlight illuminance control circuit according to the present invention includes a photocurrent sensing element and a dark current sensing element and is provided with a photocurrent signal, a dark current signal, or a forward light current signal An amplifier for fixing the voltage of the output terminal of the optical sensing unit and receiving an output signal of the optical sensing unit, amplifying the output signal of the optical sensing unit, a sampling unit connected to an output terminal of the amplifier to generate and maintain a calibration voltage or a sampled voltage, And an analog-to-digital converter that receives a calibration voltage or a sampled voltage in the analog state from the sampler and converts it into a digital calibration signal and a digital sample signal, respectively. The analog-to-digital converter includes a first analog-to-digital converter for receiving a calibration voltage in the analog state from the sampler and converting the analog calibration signal into a digital calibration signal, And a second analog-to-digital converter.

The backlight illuminance adjusting circuit may further include a calculator for storing the digital sample signal and generating a predominant value or an average value of the digital sample signal as a luminance adjustment signal. In this case, The photoelectric sensor includes a plurality of photosensors including a photocurrent sensing element and a dark current sensing element.

Further, in the case where it is configured to use a photocurrent or a pure light current signal which is dependent on a temperature change, the backlight luminance adjustment circuit according to the present invention receives an n bit digital calibration signal from the analog- And a counter for receiving the coded signal from the encoder and generating a corresponding sampled timing signal, wherein the sampler can be configured to generate the sampled voltage according to the sampled timing signal .

Next, a display device according to the present invention includes a display panel including the backlight illuminance adjusting circuit and a backlight whose illuminance is adjusted by the backlight illuminance adjusting circuit, and the display panel includes a light shielding area formed with an open portion, The sensing element is configured to be exposed to external light through the open portion and the dark current sensing element to be shielded from external light.

When the backlight illuminance adjusting method or the backlight illuminance adjusting circuit according to the present invention is applied to a display device, fluctuation of the backlight illuminance by the parameters other than the external illuminance is minimized, and high reliability can be ensured.

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

FIG. 4 is a graph showing photocurrent (I (Temp, Lux), dark current (I (Temp)), and photocurrent (I (Temp)) based on three values of Vgs for a thin film transistor type photo- (Lux) obtained by subtracting the dark current (I (Temp)) from the dark current (I (Lux)). This graph is based on an external illumination of 10000 Lux.

Referring to the graph, it can be seen that both the photocurrent (I (Temp, Lux)) and the dark current (I (Temp)) increase as the temperature increases. However, the net photocurrent (I (Lux)) obtained by subtracting the dark current (I (Temp)) from the photocurrent (I (Temp, Lux) In the case of Vgs = 0V, the net photocurrent (I (Lux)) is kept almost constant irrespective of the temperature change, and Vgs = 15V, the net photocurrent (I (Lux)) decreases with increasing temperature. Therefore, it can be seen that the external illuminance can be measured with a relatively large error even when there is a temperature change by using the pure photocurrent I (Lux) after setting Vgs to 0V. However, when Vgs is set to 0 V, the magnitude of the net photocurrent (I (Lux)) is only -11 order, and there is a high probability that the error will increase in the process of signal amplification and the like thereafter. In addition, the magnitude of the forward current (I (Lux)) depends on the individual photosensor deviation, and the size of the photosensor can be varied by the deterioration of the optical sensor channel portion over time. It is necessary to consider a method to eliminate the deviation of individual photosensors and the time dependence. If higher Vgs is used, the dependence of temperature on the photocurrent (I (Lux)) will depend on the result. Calibration can be done in the following way: First, the dark current (I (Temp)) is subtracted from the influence of the external illuminance and the temperature is measured. (Lux) accumulation amount accumulated during the standardized cumulative time, and then generates a roughness adjustment signal based on the measurement result. Since the standardized cumulative time is applied every time, it is possible to minimize the error in adjusting the illuminance according to other variables such as temperature, product deviation, and time, rather than the external illuminance change. It is not necessary to measure the external illuminance by using the forward light current (I (Lux)) and the external illuminance can be measured using the photocurrent (I (Temp, Lux)).

FIG. 5A illustrates a configuration of an optical sensor according to an exemplary embodiment of the present invention, and FIG. 5B illustrates a signal waveform input to a gate electrode of a sensing element included in the optical sensor of FIG. 5A.

The optical sensor of this embodiment is composed of a photocurrent sensing element QLT, a dark current sensing element QT and a switching element Qsw. The photocurrent sensing device QLT, the dark current sensing device QT and the switching device Qsw may be thin film transistors having a semiconductor channel region made of amorphous silicon or poly crystalline silicon, Region has a characteristic in which the number of carriers varies depending on the amount of light and the temperature flowing into the channel region.

The input voltage VI is applied to the drain electrode of the photocurrent sensing device QLT, the photocurrent sensing device control signal VLT is applied to the gate electrode, and the source electrode is connected to the drain electrode of the switching device Qsw. The switching element control signal Vsw is applied to the gate electrode of the switching element Qsw and the source electrode thereof is connected to the drain electrode of the dark sensor output terminal S_OUT and the dark current sensing element QT via the first node N1. The dark current sensing element control signal VT is applied to the gate electrode of the dark current sensing element QT and the source electrode is connected to the fixed end.

On the other hand, the light blocking region such as the black matrix includes the open portion X above the channel region of the photocurrent sensing device QLT, so that the number of carriers generated in the channel region of the photocurrent sensing device QLT is equal to the number of carriers Including the influence by the < / RTI > On the other hand, since the upper portion of the channel region of the dark current sensing element QT is covered by the black matrix, the number of carriers generated in the channel region of the dark current sensing element QT does not include the influence of external light but includes only the influence by its own temperature . 5B, in a state where a constant input voltage VI is applied to the drain electrode of the photocurrent sensing device QLT, the gate electrode of the photocurrent sensing device QLT and the gate electrode of the dark current sensing device QT When a constant photocurrent sensing element control signal VLT and a dark current sensing element control signal VT are applied to the gate electrode of the switching element Qsw and a high level switching element control signal Vsw is input to the gate electrode of the switching element Qsw, A photocurrent I (Temp, Lux) including the influence of the external light incident on the channel region of the photodiode and the influence of the channel region self temperature of the photocurrent sensing element QLT flows in the direction of the first node N1, A dark current I (Temp) including the influence of the channel region self-temperature of the dark current sensing element QT flows between one node N1 and the fixed node. Therefore, if the photocurrent sensing element QLT and the dark current sensing element QT are designed to be the same and the drain electrode and the source voltage Vds of the thin film transistor and the gate voltage and the source voltage Vgs are designed to be the same, ) Is the photocurrent (I (Lux)) which removes the influence of the channel region self-temperature of the photocurrent sensing device (QLT) at the photocurrent (I (Temp, Lux)).

FIG. 6A illustrates a configuration of an optical sensor according to another embodiment of the present invention, and FIG. 6B illustrates a signal waveform input to the optical sensor of FIG. 6A.

5A, the switching element QSW is removed and the source electrode of the photocurrent sensing element QLT is connected to the output terminal S_OUT and the dark current sensing element QT through the first node N1, To the drain electrode of the transistor. 5A and FIG. 5B, a pulse-type switching element control signal VSW is applied to the switching element QSW while a constant photocurrent sensing element control signal VLT and a dark current sensing element control signal VT are applied, To generate a direct output signal through the pulse-type photocurrent sensing device control signal VLT and the dark current sensing device control signal VT as shown in FIG. 6B without applying an output signal.

FIG. 7A is a schematic plan view of a display device to which a backlight intensity control circuit according to the present invention is applied, and FIG. 7B shows a state in which the display device of FIG. 7A actually displays a screen.

The present embodiment is a case in which the backlight illuminance adjusting circuit according to the present invention is applied to a so-called section display type display device in which the display area is divided into the fixed display area A and the general display area B.

The optical sensor included in the backlight illuminance control circuit according to the present invention may be formed of a thin film transistor having a channel region formed of apolar or silicon or polysilicon and formed simultaneously on a substrate through a liquid crystal display manufacturing process, Is preferably formed under the light blocking region 100 or the reflective electrode RE independent of the display. On the other hand, the remaining part of the backlight intensity control circuit may be embedded in the driving integrated circuit 200 or the like. Of course, the entire backlight illuminance adjusting circuit may be formed on the light blocking area 100 of the substrate or may be entirely embedded in the driving integrated circuit 200. [

The light shielding region 100 or the reflective electrode RE includes an open portion (not shown), and the photocurrent sensing element QLT is exposed through an open portion and the dark current sensing element QT is not exposed . In the case of the section display as in this embodiment, it is preferable to form the optical sensor under the reflective electrode RE located in the fixed display area A in particular. Since the fixed display area A generally displays time, volume, mode, battery remaining amount, etc., it does not require a high resolution. Therefore, the pixel is designed much larger than the normal display area B. In addition, the fixed display area A is generally configured to include a reflection area in a pixel so that the user can check at any time without any special operation. Therefore, it is advantageous from a design standpoint that a backlight illuminance adjusting circuit is formed below the reflective electrode located in the fixed display area A. [

Meanwhile, when the method and circuit for controlling backlit light intensity according to the present invention are applied to a display device of a transmission mode, it is advantageous from the viewpoint of visibility that the backlight illuminance increases as the external illuminance increases, It is preferable from the viewpoint of visibility and power consumption that the backlight illuminance is lowered as the illuminance increases.

FIG. 8 illustrates an overall configuration of a backlight illumination control circuit according to an embodiment of the present invention.

The backlight illuminance control circuit of this embodiment mainly includes a light sensing part 310, an amplifier 320, a sampler 330, an analog-to-digital converter (ADC) 340, 350 and a counter 360.

The optical sensing unit 310 of the present embodiment is a case where a plurality of optical sensors of FIG. 6A are connected in parallel.

It is needless to say that a plurality of optical sensors of FIG. 5A may be connected in parallel.

The optical sensing unit output control switch SLO may be added to the output terminal of the optical sensing unit 310, but the control signals VLT and VT of the optical sensor may be appropriately adjusted. The optical sensing unit 310 selectively outputs the photocurrent I (Temp, Lux), the dark current I (Temp), or the positive light current I (Lux) to the amplifier 320.

An output signal of the optical sensing unit 310 is input to a first input terminal of the amplifier 320 and a reference voltage VREF is input to a second input terminal of the amplifier 320. An output terminal of the amplifier 320 is connected to an input control switch SSI). The amplifier 320 amplifies the weak output signal transmitted from the optical sensing unit 310 and generates the amplified sampled voltage VS or the corrected voltage VCAL in the sampler 330. Meanwhile, the amplifier 320 of the present embodiment includes a reset switch SR for resetting the sampled voltage VS of the sampler 330 or the calibration voltage VCAL to the reference voltage VREF.

The sampler 330 includes a capacitor CS whose one end is connected to the output terminal of the amplifier 320 and the other end is connected to the fixed voltage terminal, a sampler input control switch SSI for controlling the input, And a sample-group output control switch (SSO). The capacitor receives the output signal of the amplifier 320 and generates and maintains the sampled voltage VS or the calibrated voltage VCAL and inputs and outputs are controlled through the sample input and output control switches SSI and SSO . The sampler 330 generates a sampled voltage (VS) or a calibration voltage (VCAL) in the analog state and transmits the sampled voltage (VS) or the calibration voltage (VCAL) to the analog-to-digital converter (340).

The analog-to-digital converter 340 receives the sampled voltage VS or the calibrated voltage VCAL in the analog state and converts it into a digital sample signal SDS and a digital calibration signal SDCAL, respectively. The converted digital sample signal SDS is transmitted to the backlight control unit via the output control switch SOC and the converted digital calibration signal SDCAL is transmitted to the encoder 350 via the output control switch SOC. The analog-to-digital converter 340 of the present invention may be configured by combining a plurality of comparators, and various other known analog-to-digital converters may be applied.

The encoder 350 receives the n-bit digital calibration signal SDCAL from the analog-to-digital converter 340 and generates an m-bit coded signal SE for generating a sampled timing signal? . It is needless to say that various known types of encoders 350 may be applied to the present invention.

The counter 360 receives the encoded signal SE from the encoder 350 and generates a sample extraction timing signal τ and determines the turn on time of the sample unit input control switch SSI according to the sampling timing signal τ do. It will be appreciated that various known types of counter 360 may be applied to the present invention.

The sampled voltage VS and the calibration voltage VCAL of the sampler 330 are input to the analog-to-digital converter 340 and the digital sample signal SDS and the digital calibration signal SDCAL, The sampler voltage VS and the calibration voltage VCAL of the sampler 330 are selectively transmitted to the backlight control system or the encoder 350 via the output control switch SOC. It is more preferable that the input to the analog-to-digital converter and the output of each analog-to-digital converter are input to the backlight control system and the encoder, respectively. The specific configuration may be variously changed depending on the precision of the backlight control and the precision of the sampling timing signal. Generally, a size of about several bits is sufficient for the digital sample signal (SDS), and the digital calibration signal (SDCAL) A parallel combination of several comparators is sufficient in the case of an analog-to-digital converter in which the sampled voltage VS is input, since a sufficiently high number of bits is required for precise conversion of the signal tau, For converters, an analog-to-digital converter with sufficient resolution is needed.

Hereinafter, the operation of the backlight illuminance adjusting circuit according to the present embodiment will be described with reference to the input signal waveform diagrams of FIGS. 8 and 9. FIG. Here, VLO, VR, VSI, VSO, VLT, and VT are optical sensing unit output control switches SLO, SR, SSI, SSO, The control signal input to the sensing element QLT and the dark current sensing element QT.

First, the operation during the calibration period will be described. The calibration section is a section that generates a sampling timing signal (τ) for eliminating the temperature dependency, the product deviation, and the time dependency of the final output signal.

First, in the reference voltage setting step, the reset switch SR and the sample unit input control switch SSI are turned on while the optical sensing unit output control switch SLO and the sample unit output control switch SSO are turned off, The sample voltage VS stored in the capacitor 330 is discharged and the reference voltage VREF is stored.

Next, in the calibration voltage extracting step, the photocurrent sensing unit QLT, the specimen group output control switch SSO, and the reset switch SR are turned off while the optical sensing unit output control switch SLO and the specimen input control The switch SSI is turned on and the dark current sensing element control signal VT of the high level is inputted to the dark current sensing element QT to output the reference voltage VREF of the sampler 330 through the output signal of the light sensing part 310. [ Is calibrated to the calibration voltage VCAL. In this case, assuming that the sample unit input control switch (SSI) maintains the turn-on state during the preset calibration voltage extraction period (τ˚) and that the dark current (I (Temp)) flows in the fixed- Is determined according to the following equation.

Next, in the sampling timing signal generating step, the optical sensing unit output control switch (SLO), the reset switch (SR) and the sample unit input control switch (SSI) are both off, and the sample unit output control switch (SSO) And transmits the calibration voltage VCAL to the analog-to-digital converter 340.

The analog-to-digital converter 340 converts the calibration voltage VCAL in an analog state into an n bit digital calibration signal SDCAL and then transmits the signal to an encoder 350 through an output control switch SOC.

The encoder 350 encodes the n bit digital signal into an m bit digital signal according to a predetermined algorithm and transmits the generated encoded signal SE to the counter 360. The correspondence between the n bit digital output signal value of the analog-to-digital converter 340 and the m bit digital output signal value of the encoder 350 depends on the photocurrent I (Temp, Lux), dark current I (Temp) It is possible to optimize by considering experimental data on the change of the forward light current I (Lux), and the encoder 350 can be designed based on this.

The counter 360 receives the encryption signal SE from the encoder 350 and generates a sampling timing signal? Corresponding thereto.

Meanwhile, in order to reduce the error of the sampling timing signal (tau) due to the deviation of the optical sensor or the optical sensor failure, the above-described sample extraction timing signal (tau) extraction process is sequentially performed for each optical sensor connected in parallel, The average value or the dominant value can be determined as the final sampling timing signal?. In this case, a memory and a simple arithmetic circuit for storing a sampling timing signal generated as many as the number of optical sensors are added.

Next, the operation of the circuit in the operation section will be described. The operation period is an interval for sensing the external illuminance and providing the illuminance adjustment signal VDim to the backlight.

The operation of the initial reference voltage setting step is the same as the operation of the reference voltage setting step in the above-described calibration period, and thus description thereof will be omitted.

In the sample voltage generating step, the reset switch SR and the sampler output control switch SSO are cut off, and the optical sensing unit output control switch SLO and the sample unit input control switch SSI are turned on, An element control signal VLT and a dark-sensing element control signal VT are input. At this time, the turn-on period of the sample unit input control switch SSI is determined according to the sampling timing signal? Generated in the above-described calibration period. Assuming that the forward light current I (Lux) generated in the optical sensing unit 310 flows in the direction of the amplifier 320, the sampling voltage VS (VS) stored in the capacitor CS of the sampler 330 through the sampling voltage generating period ) Is determined according to the following equation.

In the case of the illuminance control signal generation step, the sample unit input control switch SSI is turned off and the sample unit output control switch SSO is turned on. Other remaining switches are preferably turned off to minimize power consumption. In this interval, the analog-to-digital converter 340 receives the sampled voltage VS in the analog state from the sampler 330 and generates a digital sampled signal SDS. The generated digital sample voltage VDS is transferred to the operation unit 370 through the control of the digital sample voltage output control switch SOC. This operation is performed in a time division manner for the remaining optical sensors. The operation unit 370 stores the digital sample voltage VDS sequentially transmitted in a memory device such as a resistor, and then the last digital sample voltage VDS is transmitted. And outputs an average value or a dominant value to the backlight control unit VDim. The above procedure is repeated in a time division manner for a plurality of optical sensors in order to take into consideration the deviation due to the optical sensor and the optical sensor failure.

VDim can be separately connected through a low speed serial interface such as Serial Peripheral Interface (SPI) or Internal Integrated Circuit bus (I2C) existing on the driving board. To the backlight control system in the form of a command without an output pin.

Meanwhile, it is preferable that the illuminance adjustment signal (VDim) is converted at appropriate intervals in consideration of the external illuminance change correspondence degree and the power consumption, and the calibration process of the illuminance adjustment circuit may be performed at appropriate intervals It is preferable to carry out the process.

The embodiment of FIG. 8 is a preferred embodiment in the case of adjusting the illuminance by using the temperature dependence of the light-leading current (I (Lux)) signal. It is also possible to use a photocurrent (I (Temp, Lux)) signal instead of a forward light current I (Lux) signal. (I (Lux)) signal by changing the control signal input to the optical sensing unit 310 and the design of the encoder 350 when the photocurrent I (Temp, Lux) The same effect can be obtained.

Meanwhile, when the Vgs value of the sensing element is adjusted to use a positive current (I (Lux)) signal having no temperature dependency, the encoder 350, the counter 360 and the like are not necessary as in the embodiment of FIG. 8, (?) is not required. It is sufficient to use the specified sampling timing signal (tau) without correction.

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 present invention as defined by the following claims. You will understand.

FIG. 1 shows a configuration of a conventional backlight illuminance adjusting circuit.

2A shows a configuration of a conventional optical sensor.

FIG. 2B is a signal waveform diagram input to the optical sensor according to the prior art of FIG. 2A.

Fig. 3A shows another configuration of the optical sensor according to the prior art.

FIG. 3B is a signal waveform diagram input to the optical sensor according to the prior art of FIG. 3A.

FIGS. 4A, 4B, and 4C are graphs showing changes in photocurrent, dark current, and positive light current according to Vgs and temperature of the thin film transistor sensing element.

5A illustrates a configuration of an optical sensor according to an embodiment of the present invention.

5B is a signal waveform diagram input to the optical sensor according to the embodiment of FIG. 5A.

6A shows a configuration of an optical sensor according to another embodiment of the present invention.

6B is a signal waveform diagram input to the optical sensor according to the embodiment of FIG. 6A.

FIG. 7A illustrates an example in which the backlight illuminance control electric circuit according to the present invention is applied to a display device.

Fig. 7B shows an example in which the display device of Fig. 7A displays a screen.

FIG. 8 illustrates an overall configuration of a backlight illumination control circuit according to an embodiment of the present invention.

FIG. 9 is a signal waveform diagram input to the backlight illumination control circuit of FIG. 8. FIG.

              Description of Main Drawings:

310: optical sensing unit 320: amplifier

330: Sample machine

340: Analog-to-digital converter 350:

360: Counter 370: Operator

QLT: Photocurrent sensing device QT: Dark current sensing device

QSW: Switching element

SLO: Optical sensing part output control switch

SR: Reset switch

SSI: specimen input control switch

SSO: Sampling machine output control switch SOC: Output control switch

VREF: Reference voltage VCAL: Calibration voltage

VS: Sample voltage SDCAL: Digital calibration signal

SDS: digital sample signal VDim: illuminance adjustment signal

Claims (18)

Setting a reference voltage; Generating a sampled voltage based on the reference voltage through a positive current signal formed by the photocurrent sensing element and the dark current sensing element; Generating a roughness control signal based on the sampled voltage; And And adjusting the illuminance of the backlight using the illuminance adjustment signal, Wherein the photocurrent sensing element outputs a photocurrent signal based on the influence of external light and its own temperature, The dark current sensing element outputs a dark current signal based on the influence of its own temperature, Wherein the negative current signal removes the dark current signal from the photocurrent signal and does not vary in magnitude with the temperature change. The method of claim 1, The step of generating the illumination control signal includes: Converting the sampled voltage in the analog state to generate a digital sampled signal; Storing the digital sample signal; And Generating a dominant value or an average value of the stored digital sample signals as a luminance adjustment signal, Wherein the step of generating the illuminance adjusting signal after the step of setting the reference voltage, the step of generating the sampled voltage, the step of generating the digital sample signal, and the step of storing the digital sample signal are repeated several times, Adjusting the illumination. Correcting the sampling timing signal; Setting a reference voltage; Generating a sampled voltage based on the reference voltage through a positive current signal formed by the photocurrent sensing element and the dark current sensing element; Generating a luminance adjustment signal using the sampling voltage and the sampling timing signal; And And adjusting the illuminance of the backlight using the illuminance control signal, Wherein the photocurrent sensing element outputs a photocurrent signal based on the influence of external light and its own temperature, The dark current sensing element outputs a dark current signal based on the influence of its own temperature, Wherein the positive current signal is formed by removing the dark current signal from the photocurrent signal. 4. The method of claim 3, The step of generating the illumination control signal includes: Converting the sampled voltage in the analog state to generate a digital sampled signal; Storing the digital sample signal; And Generating a dominant value or an average value of the stored digital sample signals as a luminance adjustment signal, Wherein the step of generating the illuminance adjusting signal after the step of setting the reference voltage, the step of generating the sampled voltage, the step of generating the digital sample signal, and the step of storing the digital sample signal are repeated several times, Adjusting the illumination. 4. The method of claim 3, Wherein the step of calibrating the sampling timing signal comprises: Setting a reference voltage; Generating a calibration voltage based on the reference voltage using a dark current signal formed by the dark current sensing element; Converting the calibration voltage in an analog state to generate a digital calibration signal; Generating a coded signal by encoding the digital calibration signal; And And generating a sampling timing signal corresponding to the coded signal. A light sensing unit including a photocurrent sensing device and a dark current sensing device and outputting a forward light current signal; An amplifier for fixing the voltage of the output terminal of the optical sensing unit and receiving the output signal of the optical sensing unit and amplifying the output signal; A sampling unit connected to an output terminal of the amplifier to generate, maintain and output a sampled voltage; And And an analog-to-digital converter for receiving a sampled voltage in the analog state from the sampler and converting the sampled voltage into a digital sample signal, The photocurrent sensing device and the dark current sensing device are determined in terms of their shape, size, and operating conditions so that the magnitude of the positive photocurrent signal does not fluctuate according to the temperature change, Wherein the photocurrent sensing element outputs a photocurrent signal based on the influence of external light and its own temperature, The dark current sensing element outputs a dark current signal based on the influence of its own temperature, Wherein the photocurrent signal is formed by removing the dark current signal from the photocurrent signal. The method of claim 6, Further comprising a calculator for storing the digital sample signal and generating a predominant value or an average value of the stored digital sample signal as a luminance adjustment signal, Wherein the optical sensing unit includes a plurality of optical sensors including a photocurrent sensing device and a dark current sensing device. An optical sensing unit including a photocurrent sensing device and a dark current sensing device and outputting a photocurrent signal, a dark current signal, or a pure light current signal; An amplifier for fixing the voltage of the output terminal of the optical sensing unit and receiving the output signal of the optical sensing unit and amplifying the output signal; An analyzer connected to an output terminal of the amplifier to generate, maintain, and output a calibration voltage or a sampled voltage; And And an analog-to-digital converter for receiving the calibration voltage in the analog state or the sampled voltage in the analog state from the sampler and converting the sampled voltage into a digital calibration signal and a digital sample signal, Wherein the photocurrent sensing element outputs the photocurrent signal based on the influence of external light and its own temperature, The dark current sensing device outputs the dark current signal based on the influence of its own temperature, Wherein the photocurrent signal is formed by removing the dark current signal from the photocurrent signal. 9. The method of claim 8, Further comprising a calculator for storing the digital sample signal and generating a predominant value or an average value of the stored digital sample signal as a luminance adjustment signal, Wherein the optical sensing unit includes a plurality of optical sensors including the photocurrent sensing device and the dark current sensing device. 9. The method of claim 8, An encoder for receiving the digital calibration signal of n bits from the analog-to-digital converter and converting it into an m bit coded signal and outputting the m calibration signal; And Further comprising a counter for receiving the encoded signal from the encoder and generating a corresponding sampled timing signal, Wherein the sampler generates the sampled voltage according to the sampling timing signal. 9. The method of claim 8, Wherein the analog-to-digital converter comprises: a first analog-to-digital converter for receiving the calibration voltage in the analog state from the sampler and converting the calibration voltage into the digital calibration signal and outputting the calibration signal; And a second analog-to-digital converter for converting the output of the second analog-to-digital converter into a digital value. A display panel including a light blocking area provided with an open part; And And a backlight disposed on a rear surface of the display panel, Wherein the illumination control circuit of any one of claims 6 to 10 is located below the light blocking area and the photocurrent sensing element of the illumination control circuit is exposed to external light through the opening. The method according to claim 6, The photocurrent sensing device includes a first drain electrode to which an input voltage is applied, a first gate electrode to which a photocurrent sensing device control signal is applied, and a first source electrode connected to a first node, Wherein the dark current sensing element includes a second drain electrode connected to the first node, a second gate electrode to which a dark current sense element control signal is applied, and a second source electrode connected to the fixed terminal, Wherein the first node is electrically coupled to the optical sensor output. 14. The apparatus of claim 13, wherein the optical sensing unit further comprises a switching element, The switching element includes a third drain electrode connected to the first source electrode of the photocurrent sensing element, a third gate electrode to which a switching element control signal is applied, and a second gate electrode connected to the photo sensor output terminal and the dark current sensing element And a third source electrode connected to the second drain electrode. 14. The method of claim 13, The photocurrent sensing device and the dark current sensing device are designed identically, Wherein a voltage between the first drain electrode and the first source electrode of the photocurrent sensing device is equal to a voltage between the second drain electrode and the second source electrode of the dark current sensing device, Wherein the voltage between the first gate electrode and the first source electrode of the photocurrent sensing device is the same as the voltage between the second gate electrode and the second source electrode of the dark current sensing device. 9. The method of claim 8, The photocurrent sensing device includes a first drain electrode to which an input voltage is applied, a first gate electrode to which a photocurrent sensing device control signal is applied, and a first source electrode connected to a first node, Wherein the dark current sensing element includes a second drain electrode connected to the first node, a second gate electrode to which a dark current sense element control signal is applied, and a second source electrode connected to the fixed terminal, Wherein the first node is electrically coupled to the optical sensor output. 17. The apparatus of claim 16, wherein the optical sensing unit further comprises a switching element, The switching element includes a third drain electrode connected to the first source electrode of the photocurrent sensing element, a third gate electrode to which a switching element control signal is applied, and a second gate electrode connected to the photo sensor output terminal and the dark current sensing element And a third source electrode connected to the second drain electrode. 17. The method of claim 16, The photocurrent sensing device and the dark current sensing device are designed identically, Wherein a voltage between the first drain electrode and the first source electrode of the photocurrent sensing device is equal to a voltage between the second drain electrode and the second source electrode of the dark current sensing device, Wherein the voltage between the first gate electrode and the first source electrode of the photocurrent sensing device is the same as the voltage between the second gate electrode and the second source electrode of the dark current sensing device.

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