CN1776497A - Backlight device, method of driving backlight and liquid crystal display apparatus - Google Patents
Backlight device, method of driving backlight and liquid crystal display apparatus Download PDFInfo
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- CN1776497A CN1776497A CN 200510123544 CN200510123544A CN1776497A CN 1776497 A CN1776497 A CN 1776497A CN 200510123544 CN200510123544 CN 200510123544 CN 200510123544 A CN200510123544 A CN 200510123544A CN 1776497 A CN1776497 A CN 1776497A
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Abstract
Embodiments of the present invention prevents extension of the time period from powering on a device to convergence of chromaticity of emitted white light on a certain chromaticity, irrespective of the temperature when the device is powered on. A color liquid crystal display apparatus includes a liquid crystal display unit, a backlight employing LEDs of red, green and blue as its light source, a drive unit for driving the LEDs of each color, a temperature sensor for sensing the temperature of the LEDs, and a chromaticity sensor for sensing the chromaticity of white light emitted from the LEDs. The drive unit supplies a current to the LEDs to drive them, and implements feedback control of the amount of current for the LEDs of each color based on a value sensed by the chromaticity sensor so that the white light has a certain chromaticity. Furthermore, upon powering on the backlight, the drive unit retrieves initial current values of the LEDs of each color from a non-volatile memory, and corrects the initial current values according to a value sensed by the temperature sensor to activate the LEDs of each color with the corrected value.
Description
The cross reference of related application
The application is contained in Japanese patent application JP 2004-336572 number that submitted to Jap.P. office on November 19th, 2004 and the theme of the Japanese patent application JP that submits to Jap.P. office August 10 in 2005 2005-232385 number, and its full content is hereby expressly incorporated by reference.
Technical field
The present invention relates to a kind of (backlight) backlight device, a kind of method backlight and a kind of liquid crystal display of driving that is arranged on the back of non-transmission display (non-emissivetransmission display).
Background technology
Backlight as liquid crystal board used cold-cathode fluorescence lamp (CCFL) the type main flow that become backlight of fluorescent tube.Yet, because environmental problem, the demand of no mercury product is constantly increased.In recent years, these demands have caused using the expectation of light emitting diode (LED) replaced C CFL as light source.Particularly, a kind of independent each red, green and blue primary colors LED and primary colors of using is suitable for reaching the balance between color optically through adding the mixture of colours to obtain the method for white light.Therefore, concentrated and be devoted to study to realize this method for the televisor use.
If LED is as light source backlight in use, then have different luminescence efficiencys with blue led owing to red, green, the electric current of supplying to a kind of LED of color must be independent of the electric current of supplying to the LED of other colors.In addition, the semiconductor of LED constitutes different, depends on the color of LED.Therefore, for every kind of color, the voltage that is applied to element is also different with power consumption.In addition, when using LED, consider real cost, LED (for example, disclosing 2001-272938 number) that can not every kind of color of individual drive with reference to Jap.P. as light source backlight.
Use red, green and blue led as in light source backlight this, the light of these colors must come optics synthetic with the ratio of determining, to generate constant white light with definite colourity thus.Therefore, be used for the luminous power (luminous power) of the optical sensor sensing respective color of redness, green and blueness, and regulate the electric current of the LED that imposes on each color by FEEDBACK CONTROL.Therefore, to determine synthetic red, the green and blue ray of ratio, be white light with definite colourity to regulate synthetic light.
Yet if very high to the response speed of such FEEDBACK CONTROL, colourity can change continually and these variations are easy to by User Recognition.In order to overcome the drawback that frequent colourity changes, typically will be provided with very lowly to the response speed of FEEDBACK CONTROL.Therefore, to energising backlight the time, can not expect to regulate by such FEEDBACK CONTROL colourity.
Therefore, at such use LED as in light source backlight, calculate red, green and blue initial current amount (for example, the dutycycle (dutyratio) of width modulation (PWM), and drive the LED of every kind of color after the energising immediately with the initial current amount in advance.For example, before dispatching from the factory, it calculates these initial current amounts according to characteristic backlight.Suitably being provided with of this tittle can be shortened time interval of assembling (converge) extremely definite colourity from the colourity that is energized to the white light that will launch.
If the initial current amount suitably is not set, and therefore very long up to the time interval of assembling to determining colourity, on screen, show in the time of then can occurring beginning pink and subsequently this color little by little near the phenomenon of white.
Summary of the invention
When using LED, used a large amount of LED as light source backlight.Therefore, after energising backlight, there is greatest differences between the temperature of the LED in the temperature at once of LED and the steady state operation (temperature-resistant state).In addition, the optical characteristics of LED has significant change according to temperature.Therefore, the optical characteristics at once of the LED after the energising greatly is different from the optical characteristics of the LED in steady state operation.
Therefore, even be provided to the suitable initial current amount of LED when calculating energising in advance, if the temperature change during energising, the value of being calculated can not be suitable value yet.This temperature variation has hindered and has shortened the time interval of assembling to determining colourity from being energized to.
Consider that above-mentioned situation in the past proposes the present invention, its purpose is to provide a kind of back lighting device, a kind of method backlight and a kind of liquid crystal display of driving, above-mentioned back lighting device adopts LED and the temperature when switching on, and can prevent that the colourity that is energized to white light that will emission from device from assembling to the prolongation in the time interval of determining colourity.
One aspect of the present invention is to provide a kind of back lighting device, and its a plurality of light emitting diodes with at least three kinds of colors are as light source.The light of the synthetic light emitting diode emission from every kind of color of this back lighting device to be producing white light, and the white light that is generated from the back emission of display unit.This back lighting device comprises: temperature sensor is used for the temperature of sensing light source; And driving control device, be used for providing electric current with the driven for emitting lights diode to the light emitting diode of every kind of color.This back lighting device also comprises memory storage, is used to store the initial current amount of the light emitting diode that is used for every kind of color and the correcting value that is used for the initial current amount.Correcting value depends on temperature.Driving control device when back lighting device is switched on based on coming the calculation correction amount by the value of temperature sensor institute sensing.Driving control device is increased to the correcting value that is calculated the initial current amount of the light emitting diode of every kind of color, and activates the light emitting diode of every kind of color with the initial current amount of proofreading and correct.
Another aspect of the present invention is to provide a kind of back lighting device with light emitting diode of redness, green and blueness as light source.This back lighting device will be from the light compositing of the light emitting diode of every kind of color emission generating white light, and the white light that is generated from the back emission of display unit.This back lighting device comprises: chromaticity transducer is used for the colourity of sensing white light; And temperature sensor, be used for the temperature of sensing light source.This back lighting device also comprises driving control device, be used for providing electric current with the driven for emitting lights diode to the light emitting diode of every kind of color, and, make white light have definite colourity according to the FEEDBACK CONTROL of carrying out by the value of chromaticity transducer institute sensing the magnitude of current of the light emitting diode that offers every kind of color.The driving control device fixed flow magnitude of current of blue light emitting diode is excessively also regulated the magnitude of current that flows through red and green light emitting diode, to carry out FEEDBACK CONTROL thus, makes white light have definite colourity.
Another aspect of the present invention is to provide a kind of driving to have the method for a plurality of light emitting diodes of at least three kinds of colors as the back lighting device of light source.This back lighting device will be from the light compositing of the light emitting diode of every kind of color emission generating white light, and the white light that is generated from the back emission of display unit.This method comprises initial current amount of storing the light emitting diode that is used for every kind of color and the step that is used for the correcting value of initial current amount.Correcting value depends on temperature.This method also is included in back lighting device when energising, based on coming the calculation correction amount by the value of the temperature sensor institute sensing that is used for the sensor light source temperature, and the correcting value that is calculated is increased to the initial current amount of the light emitting diode of every kind of color.This method further comprises the light emitting diode that activates every kind of color with the initial current amount of proofreading and correct, and based on value by the chromaticity transducer institute sensing that is used for sensing white light colourity, execution makes white light have definite colourity to the FEEDBACK CONTROL of the magnitude of current of the light emitting diode that offers every kind of color.
Another aspect of the present invention is to provide a kind of driving to have the method for the light emitting diode of redness, green and blueness as the back lighting device of light source.This back lighting device will be from the light compositing of the light emitting diode of every kind of color emission generating white light, and the white light that is generated from the back emission of display unit.This method comprises based on the FEEDBACK CONTROL of being carried out by the value of the chromaticity transducer institute sensing that is used for sensing white light colourity the magnitude of current of the light emitting diode that offers every kind of color, makes white light have the step of definite colourity.The fixed flow magnitude of current of blue light emitting diode is excessively also regulated the magnitude of current that flows through red and green light emitting diode, to carry out FEEDBACK CONTROL thus, makes white light have definite colourity.
Another aspect of the present invention is to provide a kind of liquid crystal display, and it comprises the transparent color LCD panel and has the back lighting device of a plurality of light emitting diodes of at least three kinds of colors as light source.Back lighting device will be from the light compositing of the light emitting diode of every kind of color emission to generate white light.The transparent color LCD panel is by the white light that is generated from transparent color LCD panel back.Back lighting device comprises: temperature sensor is used for the temperature of sensing light source; And chromaticity transducer, be used for the colourity of sensing white light.Back lighting device also comprises: driving control device is used for providing electric current with the driven for emitting lights diode to the light emitting diode of every kind of color; And memory storage, be used to store the initial current amount of the light emitting diode that is used for every kind of color and the correcting value that is used for the initial current amount.Correcting value depends on temperature.Driving control device when back lighting device is switched on based on coming the calculation correction amount by the value of temperature sensor institute sensing.Driving control device is increased to the correcting value that is calculated the initial current amount of the light emitting diode of every kind of color then, and activates the light emitting diode of every kind of color with the initial current amount of proofreading and correct.After this, driving control device makes white light have definite colourity based on the FEEDBACK CONTROL of being carried out by the value of chromaticity transducer institute sensing the magnitude of current of the light emitting diode that offers every kind of color.
Another aspect of the present invention is to provide a kind of liquid crystal display, and it comprises the transparent color LCD panel and has the back lighting device of the light emitting diode of redness, green and blueness as light source.Back lighting device will be from the light compositing of the light emitting diode of every kind of color emission to generate white light.The transparent color LCD panel is by the white light that is generated from transparent color LCD panel back.Back lighting device comprises: chromaticity transducer is used for the colourity of sensing white light; And temperature sensor, be used for the temperature of sensing light source.Back lighting device also comprises: driving control device, be used for providing electric current with the driven for emitting lights diode to the light emitting diode of every kind of color, and, make white light have definite colourity based on the FEEDBACK CONTROL of carrying out by the value of chromaticity transducer institute sensing the magnitude of current of the light emitting diode that offers every kind of color.The driving control device fixed flow magnitude of current of blue light emitting diode is excessively also regulated the magnitude of current that flows through red and green light emitting diode, to carry out FEEDBACK CONTROL thus, makes white light have definite colourity.
These aspects of the present invention can shorten the colourity that is energized to the white light that will be launched from back lighting device to be assembled to the time interval of determining colourity, and the temperature the during energising of not consideration equipment.
Description of drawings
Fig. 1 is a perspective schematic view of using the structure of the color liquid crystal display unit that has back light system in the chromatic liquid crystal display equipment of the present invention;
Fig. 2 represents by the pattern of the light emitting diode with every kind of color, shows by using the synoptic diagram of the unit cell (unitcell) that two red light emitting diodes, two green LEDs and two blue LEDs and six light emitting diodes of arranged in series obtain;
Fig. 3 shows the synoptic diagram of example of the actual connection of the light emitting diode in the light source 21 of back lighting device;
Fig. 4 shows the integrally-built block diagram of chromatic liquid crystal display equipment;
Fig. 5 shows back lighting device, is used for the sensor of back lighting device and the synoptic diagram of cooling fan;
Fig. 6 shows the group of light emitting diode of along continuous straight runs series connection and the synoptic diagram of a plurality of led drive circuits that is used for each group of driven for emitting lights diode;
Fig. 7 is the structured flowchart of led drive circuit;
Fig. 8 is used to make the colourity of white light to assemble the process flow diagram of extremely determining colourity and being stabilized in the control and treatment at this place;
Fig. 9 is the optical characteristics as LED when constant and temperature independent, based on the luminous power of the blue led that obtains, by the synoptic diagram of the ratio (PhtG/PhtB and PhtR/PhtB) of the luminous power of luminous power/chromaticity transducer institute sensing;
Figure 10 is the synoptic diagram of the brightness conduct of each redness (R), green (G) and blue (B) LED element from the function of its wavelength of light emitted;
Figure 11 is from the synoptic diagram of the sensing of chromaticity transducer output as the function of temperature;
Figure 12 is used to obtain to determine the synoptic diagram of the magnitude of current of colourity as the function of temperature; And
Figure 13 is being used for obtaining to determine the magnitude of current of colourity and the synoptic diagram of the difference between the initial current amount when back lighting device is switched on.
Embodiment
Describe embodiments of the invention below with reference to accompanying drawings in detail.
The present invention is applied to chromatic liquid crystal display equipment, and this display device for example has, as shown in Figure 1 the backlight liquid crystal display 1 of structure.
(structure of liquid crystal display)
Liquid crystal display 1 comprises: transparent color LCD panel 10; And back lighting device 20, be arranged at the back of color LCD board 10.
(plate)
Transparent color LCD panel 10 comprises: the TFT substrate 11 that faces with each other, counter electrode (counter electrode) substrate 12; And liquid crystal layer 13, have twisted nematic (TN) liquid crystal in the gap that for example is encapsulated between TFT substrate 11 and the counter electrode substrate 12.On TFT substrate 11, be formed with: the signal wire 14, the sweep trace 15 that become arranged in matrix; Thin film transistor (TFT) 16 is arranged on the point of crossing between signal wire 14 and the sweep trace 15 as on-off element; And pixel electrode 17.Thin film transistor (TFT) 16 sequentially is scanned line 15 and selects, and will be write pixel electrode 17 by the vision signal that signal wire 14 provides.On the inside surface of counter electrode substrate 12, be formed with counter electrode 18 and color filter 19.
In liquid crystal display 1, the transparent color LCD panel 10 with this structure places between two polarizing plates.Liquid crystal display 1 is driven by the active matrix method, and back lighting device 20 is launched white light from the back of color LCD board 10 simultaneously, thereby the panchromatic video of realizing expectation shows.
(backlight)
A large amount of light emitting diode (LED) 3 is arranged in the light source 21 of back lighting device 20.Back lighting device 20 outputs are from the light of LED emission.Be provided with in light source 21: a large amount of LED 3R is used for red-emitting; A large amount of LED 3G is used for transmitting green light; And a large amount of LED 3B, be used to launch blue light.Light source 21 mixes redness, blueness and green light with the generation white light, and white light emission is arrived color LCD board 10.
For example, the arrangement of the LED 3 in the light source 21 of back lighting device 20 is as follows.
Beginning as shown in Figure 2, is arranged two red LED 3R, two green LED 3G and two blue led 3B.Particularly, six LED arranged in series are with component unit unit ( 2G 2R 2B).Then, three unit cells ( 2G 2R 2B) are transversely arranged to constitute intermediate unit unit ( 6G 6R 6B).As shown in Figure 3, intermediate unit unit (6G 6R6B) along continuous straight runs is connected in series.The group of the unit that is connected in series is arranged in vertical direction, to cover whole screen.
This arrangement of LED allows to mix the light from three kinds of colors of red, green and blue led, and therefore allows the well-balanced white light of emission.The arrangement of LED is not limited to Fig. 2 and arrangement shown in Figure 3, as long as but can guarantee well-balanced blend of colors, any arrangement all is available.
(one-piece construction of chromatic liquid crystal display equipment)
Fig. 4 shows the integrally-built example of chromatic liquid crystal display equipment 30.
Chromatic liquid crystal display equipment 30 comprises: power supply unit 31 is used to provide the driving voltage of color LCD board 10 and back lighting device 20; And X driver 32 and Y driver 33, be used to drive color LCD board 10.Chromatic liquid crystal display equipment 30 also comprises: RGB processing unit 35, by input terminal 34 from the outside to its supplying video signal; Video memory 36, control module 37 are connected to RGB processing unit 35; And backlight drive control module 38, be used to control the driving of back lighting device 20.
By 35 pairs of RGB processing units via the vision signals of input terminal 34 inputs carry out signal Processing (such as, colourity is handled).In addition, signal changes into the RGB separation signal that is suitable for driving color LCD board 10 from composite signal, is provided to control module 37 then and is provided to X driver 32 via video memory 36.Control module 37 is controlled X driver 32 and Y driver 33 according to the RGB separation signal in default timing (timing), and therefore use drives color LCD board 10 via the RGB separation signal that video memory 36 is provided to X driver 32, thereby according to RGB separation signal display video.
In addition, as shown in Figure 4 and Figure 5, chromatic liquid crystal display equipment 30 comprises: temperature sensor 41; Luminous power/chromaticity transducer 42; And cooling fan 43, be used to reduce the temperature of back lighting device 20.The temperature of the light source 21 (LED) of temperature sensor 41 sensing back lighting devices 20.Luminous power/chromaticity transducer 42 (42R, 42G, 42B) sensing is from the luminous power or the colourity of the light of each R, the G of the light source 21 (LED) of back lighting device 20 and B.
Value by temperature sensor 41 and 42 sensings of luminous power/chromaticity transducer is provided to backlight drive control module 38.Backlight drive control module 38 is controlled the drive current of the LED that is used to constitute light source 21 based on sensing value.
In addition, backlight drive control module 38 is according to the rotating speed of being controlled cooling fan 43 by 41 sensed temperature values of temperature sensor, thus the temperature of the light source 21 (LED) of control back lighting device 20.
In addition, backlight drive control module 38 inside have nonvolatile memory 38a.Nonvolatile memory 38a is used to store various setting values.
(led drive circuit)
In backlight drive control module 38, be provided with a plurality of led drive circuits 50, be used to drive the light source 21 (LED) of back lighting device 20.
As shown in Figure 6, the LED 3 that serves as same color light source, that arrange in the horizontal direction of back lighting device 20 is electrically connected with being one another in series.For each group in 3 groups of the LED coupled in series in the horizontal direction is provided with separately led drive circuit 50 independently.
Fig. 7 shows the example of the circuit structure of the led drive circuit 50 that is arranged in the backlight drive control module 38.
The dc voltage VIN that power supply 31 shown in DC-DC converter 51 acceptance patterns 4 produces, and change the dc voltage that is received, to produce stable DC output voltage V cc.DC-DC converter 51 produces stable like this output voltage V cc, makes to equal reference voltage (Vref) from the voltage and the electric potential difference between the output voltage V cc of feedback terminal Vf input.Reference voltage (Vref) is provided by reference power supply 59.
The positive pole of LED coupled in series 3 is connected to the lead-out terminal of the output voltage V cc of DC-DC converter 51 by constant resistance device (Rc).The positive pole of LED coupled in series 3 also is connected to the feedback terminal of DC-DC converter 51 by sampling and source electrode that keeps FET 56 and drain electrode.The negative pole of LED coupled in series 3 is by source electrode and the grounded drain of FET 53.
Be input to the grid of FET 53 from the pwm signal of pwm control circuit 54 generations.When pwm signal was ON, FET 53 was opened, and is closed when pwm signal is OFF.Therefore, when pwm signal was ON, FET 53 provided electric current to LED 3, and did not provide electric current when pwm signal is OFF.Particularly, when pwm signal was ON, FET 53 made LED 3 luminous, and it is luminous that LED 3 is stopped.
Keep timing circuit 58 to receive pwm signal and produce holding signal.At the rising edge place of pwm signal, determining that holding signal is OFF in the time interval, and in the other times interval, be ON.
Be input to sampling and the grid that keeps FET 56 from the holding signal that keeps timing circuit 58 outputs.When holding signal was OFF, sampling was opened with keeping FET 56, and is closed when holding signal is ON.
In above-mentioned led drive circuit 50, electric current I LED only flows through LED 3 when the pwm signal that is produced by pwm control circuit 54 is ON.Capacitor 55, sampling and maintenance FET 56 and resistor 57 constitute sampling and holding circuits.When pwm signal was ON, sampling and holding circuit sampling be (that is) magnitude of voltage, an end that is not connected with the lead-out terminal of voltage vcc at constant resistance device 52, and this magnitude of voltage is provided to the feedback terminal of DC-DC converter 51 at the positive pole place of LED 3.Because DC-DC converter 51 makes output voltage V cc stable based on the magnitude of voltage that is input to feedback terminal, the peak value that therefore flows through the electric current I LED of constant resistance device Rc 52 and LED 3 keeps constant.
Therefore, in led drive circuit 50, when the peak value of the electric current I LED that flows through LED 3 keeps constant, carry out pulsed drive according to pwm signal.
In this circuit, regulate the magnitude of current that flows through LED 3 by changing controlling value (PWM).Yet, can regulate the magnitude of current that flows through LED 3 by the reference voltage (Vref) that change is applied to DC-DC converter 51.Alternatively, can use the combination of these changes.
(be used to keep colourity constant control method)
Use description to below to make from the colourity of the white light of back lighting device 20 emissions and assemble to specific colourity and make it stable control method.
During in back lighting device 20 energisings and from back lighting device 20 emission white lights, backlight drive control module 38 is carried out control, make the luminous power ratio between red LED 3R, green LED 3G and the blue led 3B become specific ratio, thus will be from the chroma stability of the white light of back lighting device 20 emission in specific colourity.
Particularly, carry out this control according to process flow diagram shown in Figure 8.
Beginning, in step S1, when back lighting device 20 energisings, the initial current value (PWMR0, PWMG0 and PWMB0) of backlight drive control module 38 retrieve stored in nonvolatile memory 38a uses initial current value separately to activate red LED 3R, green LED 3G and blue led 3B then.
Then, in step S2, the driving that the initial current value that backlight drive control module 38 usefulness are retrieved (PWMR0, PWMG0 and PWMB0) comes the LED3 of every kind of color of initialization.When starting the driving of LED 3, light is launched from back lighting device 20.
Then, in step S3, backlight drive control module 38 is according to the sensing value of luminous power/chromaticity transducer 42 outputs, execution is used for the FEEDBACK CONTROL (PWM dutycycle) of the drive current of redness, green and blue led 3R, 3G and 3B, makes to have definite colourity from the white light (red, green and blue synthetic light) of back lighting device 20 emissions.
Particularly, carry out control and make that PhtR:PhtG:PhtB is constant, wherein PhtR, PhtG and PhtB are respectively the luminous powers by ruddiness, green glow and the blue light of luminous power/chromaticity transducer 42 sensings.
(carrying out the reason of control based on blue light)
When execution is used to keep the constant FEEDBACK CONTROL of colourity, must regulate three kinds of magnitudes of current (flowing through the magnitude of current of redness, green and blue led) simultaneously, this greatly makes to handle and becomes complicated.Therefore, in backlight drive control module 38, the current value that flows through blue led 3B is fixed consistently, and flows through the LED3R of other color (that is, red and green) and the electric current of 3G changes, thereby allows to be used to the adjusting that keeps colourity constant.
Cross the electric current of blueness (B) LED by such fixed flow, can be defined for the parameter in the various calculating of FEEDBACK CONTROL more simply.Particularly, for blue (B) LED, parameter is " 1 " always, and for red (R) and green (G) LED, can use ratio with respect to blueness (B) LED as its parameter.
Therefore, the quantity of pending variable can be reduced to two, this has simplified arithmetic processing significantly.
In offering the magnitude of current of LED, the reason that the magnitude of current that offers blue led 3B is fixing is as described below.
If the optical characteristics of LED is constant and temperature independent, then as shown in Figure 9, also be constant and temperature independent based on ratio (PhtG/PhtB and PhtR/PhtB) by the optical power value of the luminous power of the blue led of 42 sensings of luminous power/chromaticity transducer.
Yet in fact, the optical characteristics of LED has great variation with temperature.
For example, Figure 10 shows the curve map of the brightness conduct of every kind of redness (R), green (G) and blue (B) LED element from the function of its wavelength of light emitted.The curve of Figure 10 shows respectively when the Luminance Distribution of temperature when being 0 ℃, 25 ℃ and 50 ℃.In the curve of Figure 10, institute's wavelength of light emitted is plotted on the X-axle, and luminous output (brightness) is plotted on the Y-axle.
As what can obviously find out from Figure 10, the luminous power of each LED element (by the area of the part that curve surrounded) changes with temperature.In addition, higher temperature moves the wavelength of luminous power curve Chao Genggao.In red (R) LED element, higher temperature makes the wavelength of wavelength (peak wavelength) Chao Genggao corresponding to brightness peak move significantly especially.
Therefore,, do not allow accurate control, unless also consider temperature characterisitic in the FEEDBACK CONTROL that is used for keeping constant chromaticity.
Therefore backlight drive control module 38 is not only controlled based on the execution that the sensing of luminous power/chromaticity transducer 42 is exported, also according to the sensing output execution correction from temperature sensor 41.Thisly considered that temperature controlling makes stable colourity as shown in figure 11 become possibility.
When also so carrying out the timing that relates to temperature,, then can realize stable FEEDBACK CONTROL if carry out treatment for correcting based on the color that varies with temperature the optical power change minimum.On the contrary, vary with temperature the bigger color of optical power change as benchmark if use, then reference value is easy to change with temperature, and this makes and is difficult to realize stable FEEDBACK CONTROL.
With reference to the curve of Figure 10, blue led has the peak value that minimum wavelength moves the minimum change that changes with relative temperature.
Therefore, backlight drive control module 38 is carried out control by the magnitude of current that is fixed for blue led 3B.
(temperature drift during backlight the energising)
Initial current value (PWMR0, PWMG0 and PWMB0) when in addition, backlight drive control module 38 bases are proofreaied and correct the back lighting device energising by 41 sensed temperature of temperature sensor.
Be used to the FEEDBACK CONTROL that keeps colourity constant if carry out, then be used for each LED the magnitude of current (duty of PWM) temperature characterisitic as shown in figure 12.
As shown in figure 13, if limit initial current value (PWMR0, PWMG0 and PWMB0) based on the optimum value that for example when temperature is 65 ℃, obtains, then when temperature was 30 ℃, red and green LED had the difference of pact-20% (Rerr) and-10% (Gerr) respectively with respect to initial value.Because it is constant that the drive current (PWM duty) that is used for blue led is controlled as, so blue led does not have this difference.Therefore, for example, the temperature when back lighting device 20 energisings is 30 ℃, and FEEDBACK CONTROL is necessary for these differences (Rerr and Gerr) and regulates current value, to realize the convergence of colourity.
Yet because these differences are bigger, so the time interval of colourity convergence cost is longer.If the time interval before assembling is longer, the red LED that then has big difference is influential to picture quality, therefore visually can discern from pink color to white (white has target colourity) to gradually change.
In order to address this problem, by considering the temperature (by the value of 41 sensings of temperature sensor) when back lighting device 20 is switched on, backlight drive control module 38 is according to for example following equation 1, proofread and correct from the initial value (PWMR0 and PWMG0) of nonvolatile memory 38a retrieval, and corrected value is offered each LED as drive current.
Equation 1
Wherein,
DrT1＝RerrT1/PWMG0
DgT1＝GerrT1/PWMG0
Each parameter-definition in the equation 1 is as follows:
PWMRt: be the magnitude of current (current value after the correction) of red LED setting
PWMGt: be the magnitude of current (current value after the correction) of green LED setting
T0: the temperature (for example, 65 ℃) when calculating initial current value (PWMR0, PWMG0 and PWMB0)
T1: arbitrary temp
T: by the Current Temperatures of the back lighting device 20 of 41 sensings of temperature sensor.
RerrT1: the current value difference of red LED when temperature is T1 (, from PWMR0, deduct the colourity of working as the light of being launched has been assembled red LED when determining colourity in temperature T 1 the resulting value of current value)
GerrT1: the current value difference of green LED when temperature is T1 (, deduct the colourity of working as the light of being launched has been assembled green LED when determining colourity in temperature T 1 the resulting value of current value from PWMG0)
By proofreading and correct the initial current amount as mentioned above, can make that the magnitude of current that initially applies is more approaching can cluster value, and this can shorten the time interval (be stabilized be the time interval before the white light with definite colourity at the light of being launched) of convergence.
Should be noted that RerrT1 and GerrT1 calculated in advance and be stored among the nonvolatile memory 38a before back lighting device 20 dispatches from the factory.Can calculate RerrT1 and GerrT1 for each back lighting device 20.Alternatively, for example, consider throughput rate, can the theory of storage calculated value.
The above is the preferred embodiments of the present invention only, is not limited to the present invention, and for a person skilled in the art, the present invention can have various changes and variation.Within the spirit and principles in the present invention all, any modification of being done, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (11)
1. back lighting device, a plurality of light emitting diodes with at least three kinds of colors are as light source, the light of the synthetic described light emitting diode emission from every kind of color of described back lighting device to be generating white light, and the described white light that generates from the back emission of display unit, and described back lighting device comprises:
Temperature sensor is used for the temperature of the described light source of sensing;
Driving control device is used for providing electric current to the described light emitting diode of every kind of color, to drive described light emitting diode; And
Memory storage is used to store the initial current amount of the described light emitting diode that is used for every kind of color and the correcting value that is used for described initial current amount, and described correcting value depends on temperature, wherein,
When described back lighting device is switched on, described driving control device is based on calculating described correcting value by the value of described temperature sensor institute sensing, described driving control device is added to the correcting value that is calculated on the described initial current amount of described light emitting diode of every kind of color, and activates the described light emitting diode of every kind of color with the initial current amount of proofreading and correct.
2. back lighting device according to claim 1 further comprises:
Chromaticity transducer, the colourity that is used for the described white light of sensing, wherein, described driving control device makes described white light have definite colourity based on the FEEDBACK CONTROL of being carried out by the value of described chromaticity transducer institute sensing the magnitude of current of the described light emitting diode that offers every kind of color.
3. back lighting device according to claim 2, wherein,
Described light emitting diode as described light source is red, green and blue light emitting diode; And
Described driving control device fixed flow is crossed the magnitude of current of the light emitting diode of described blueness, and regulates the magnitude of current of the light emitting diode that flows through described redness and green, to carry out described FEEDBACK CONTROL thus, makes described white light have definite colourity.
4. back lighting device according to claim 1, wherein, described driving control device is controlled the luminous power of described light emitting diode by pulse width modulation controlled, and described back lighting device is regulated the dutycycle of described pulse width modulation controlled, to regulate the magnitude of current that is provided to described light emitting diode thus.
5. back lighting device, light emitting diode with redness, green and blueness is as light source, the light of the synthetic described light emitting diode emission from every kind of color of described back lighting device to be generating white light, and the described white light that generates from the back emission of display unit, and described back lighting device comprises:
Chromaticity transducer is used for the colourity of the described white light of sensing;
Temperature sensor is used for the temperature of the described light source of sensing; And
Driving control device, be used for providing electric current to drive described light emitting diode to the described light emitting diode of every kind of color, and based on the FEEDBACK CONTROL of carrying out by the value of described chromaticity transducer institute sensing the magnitude of current of the described light emitting diode that offers every kind of color, make described white light have definite colourity, wherein
Described driving control device fixed flow is crossed the magnitude of current of the light emitting diode of described blueness, and regulates the magnitude of current of the light emitting diode that flows through described redness and green, to carry out described FEEDBACK CONTROL thus, makes described white light have definite colourity.
6. method that drives back lighting device, described back lighting device has a plurality of light emitting diodes of at least three kinds of colors as light source, the synthetic light of launching from the described light emitting diode of every kind of color of described back lighting device is to generate white light, and, said method comprising the steps of from the described white light that the emission of the back of display unit generates:
Store the initial current amount of the described light emitting diode that is used for every kind of color and the correcting value that is used for described initial current amount, described correcting value depends on temperature;
When the energising of described back lighting device, based on calculating described correcting value by the value of the temperature sensor institute sensing of the temperature of the described light source of sensing;
The correcting value that is calculated is added on the described initial current amount of described light emitting diode of every kind of color;
Activate the described light emitting diode of every kind of color with the initial current amount of proofreading and correct; And
Based on value by the chromaticity transducer institute sensing of the colourity of the described white light of sensing, carry out FEEDBACK CONTROL to the magnitude of current of the described light emitting diode that offers every kind of color, make described white light have definite colourity.
7. the method for driving back lighting device according to claim 6, the described light emitting diode as described light source in described back lighting device is red, green and blue light emitting diode, wherein,
Fixed flow is crossed the magnitude of current of the light emitting diode of described blueness, and regulates the magnitude of current of the light emitting diode that flows through described redness and green, to carry out described FEEDBACK CONTROL thus, makes described white light have definite colourity.
8. method that drives back lighting device, described back lighting device has the light emitting diode of redness, green and blueness as light source, the synthetic light of launching from the described light emitting diode of every kind of color of described back lighting device is to generate white light, and, said method comprising the steps of from the described white light that the emission of the back of display unit generates:
Based on value by the chromaticity transducer institute sensing of the colourity of the described white light of sensing, carry out FEEDBACK CONTROL to the magnitude of current of the described light emitting diode that offers every kind of color, make described white light have definite colourity, wherein,
Fixed flow is crossed the magnitude of current of the light emitting diode of described blueness, and regulates the magnitude of current of the light emitting diode that flows through described redness and green, to carry out described FEEDBACK CONTROL thus, makes described white light have definite colourity.
9. liquid crystal display, comprise back lighting device and transparent color LCD panel, described back lighting device has a plurality of light emitting diodes of at least three kinds of colors as light source, and the synthetic light of launching from the described light emitting diode of every kind of color is to generate white light, described transparent color LCD panel quilt is from the described white light of the generation at the back of described transparent color LCD panel, and described back lighting device comprises:
Temperature sensor is used for the temperature of the described light source of sensing;
Chromaticity transducer is used for the colourity of the described white light of sensing;
Driving control device is used for providing electric current to drive described light emitting diode to the described light emitting diode of every kind of color; And
Memory storage is used to store the initial current amount of the described light emitting diode that is used for every kind of color and the correcting value that is used for described initial current amount, and described correcting value depends on temperature, wherein:
When described back lighting device is switched on, described driving control device is based on calculating described correcting value by the value of described temperature sensor institute sensing, described driving control device is added to the correcting value that is calculated on the described initial current amount of described light emitting diode of every kind of color, and activates the described light emitting diode of every kind of color with the initial current amount of proofreading and correct; And
Described driving control device makes described white light have definite colourity based on the FEEDBACK CONTROL of being carried out by the value of described chromaticity transducer institute sensing the magnitude of current of the described light emitting diode that offers every kind of color.
10. liquid crystal display according to claim 9, wherein,
Described light emitting diode as described light source is red, green and blue light emitting diode; And
Described driving control device fixed flow is crossed the magnitude of current of the light emitting diode of described blueness, and regulates the magnitude of current of the light emitting diode that flows through described redness and green, to carry out described FEEDBACK CONTROL thus, makes described white light have definite colourity.
11. liquid crystal display, comprise back lighting device and transparent color LCD panel, described back lighting device has the light emitting diode of redness, green and blueness as light source, and the synthetic light of launching from the described light emitting diode of every kind of color is to generate white light, described transparent color LCD panel quilt is from the described white light of the generation at the back of described transparent color LCD panel, and described back lighting device comprises:
Chromaticity transducer is used for the colourity of the described white light of sensing;
Temperature sensor is used for the temperature of the described light source of sensing; And
Driving control device, be used for providing electric current to drive described light emitting diode to the described light emitting diode of every kind of color, and based on the FEEDBACK CONTROL of carrying out by the value of described chromaticity transducer institute sensing the magnitude of current of the described light emitting diode that offers every kind of color, make described white light have definite colourity, wherein
Described driving control device fixed flow is crossed the magnitude of current of the light emitting diode of described blueness, and regulates the magnitude of current of the light emitting diode that flows through described redness and green, to carry out described FEEDBACK CONTROL thus, makes described white light have definite colourity.
Applications Claiming Priority (5)
| Application Number | Priority Date | Filing Date | Title |
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| JP2004336572 | 2004-11-19 | ||
| JP2004-336572 | 2004-11-19 | ||
| JP2004336572 | 2004-11-19 | ||
| JP2005-232385 | 2005-08-10 | ||
| JP2005232385 | 2005-08-10 |
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| CN2008101312024A Division CN101339743B (en) | 2004-11-19 | 2005-11-17 | Backlight device, method of driving backlight device and liquid crystal display apparatus |
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| CN1776497A true CN1776497A (en) | 2006-05-24 |
| CN100419523C CN100419523C (en) | 2008-09-17 |
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| CNB2005101235448A Expired - Fee Related CN100419523C (en) | 2004-11-19 | 2005-11-17 | Backlight device, method of driving backlight and liquid crystal display apparatus |
| CN2008101312024A Expired - Fee Related CN101339743B (en) | 2004-11-19 | 2005-11-17 | Backlight device, method of driving backlight device and liquid crystal display apparatus |
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| CN2008101312024A Expired - Fee Related CN101339743B (en) | 2004-11-19 | 2005-11-17 | Backlight device, method of driving backlight device and liquid crystal display apparatus |
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Also Published As
| Publication number | Publication date |
|---|---|
| JP2010237683A (en) | 2010-10-21 |
| CN101339743A (en) | 2009-01-07 |
| CN100419523C (en) | 2008-09-17 |
| CN101339743B (en) | 2011-02-09 |
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