CN102042530A - Backlight plate provided with tandem LED components, manufacturing method and display provided with backlight plate - Google Patents

Abstract

The invention discloses a backlight plate provided with tandem light emitting diode (LED) components, a manufacturing method of the backlight plate, and a display provided with the backlight plate. The backlight plate comprises a power supply device, the tandem LED components and a liquid crystal module, wherein the power supply device supplies energy to at least two strings of tandem LED components parallel with each other and the liquid crystal module which serves as a backlight source; the tandem LED components consist of enough LEDs connected in series; and the supply voltage needed by each string of the LEDs is close to the multiplication product of the average voltage and the number of the LED, thereby greatly solving the problem of different forward voltage needed by each LED, and reducing the screening cost of the LEDs. The backlight plate further can comprise a light homogenizing device, wherein a front reflecting piece is arranged between a light homogenizing sheet and the tandem LED components; a back reflecting piece is arranged at a position far away from the light homogenizing sheet side; and the two reflecting pieces repeatedly project and homogenize the light emitted by the tandem LED components, thereby achieving the effects of reducing the manufacturing cost and improving the product yield.

Description

The display of backlight, method for making and this backlight of tool of tool serial connection LED assembly

[technical field]

The invention relates to a kind of backlight, especially reduce the LED-backlit plate of screening conditions and cost and display with this backlight by serial connection a large amount of light emitting diodes (hereinafter to be referred as LED) assembly.

[background technology]

The application of LED is gradually wide, is received to main flow by backlight and field of display gradually at present, but is subject to indivedual LED luminance shortage, therefore as shown in Figure 1 common, after number LEDs element 10 serial connections, drive by single dc source 12, as the backlight of for example notebook computer.The great advantage of the technology of this kind serial connection plurality of LEDs is to simplify the drive unit of LED, and can adopt the electrical power that bigger voltage and less current provide is enough to drive plurality of LEDs, and the cost of power supply is less, thereby reaches the purpose of lower cost.

Yet one side display demand size heals and becomes huge, and the backlight of notebook computer dimensions can't be loaded and be illuminated the demand of large size panel at present; Especially indivedual positive drive voltage scopes of the LED that is connected in series must be limited in a certain among a small circle in, otherwise dc source according to the predetermining circuit design, when flowing through this string LED assembly, drive current will produce greatly with original design and change, and cause the big variation of whole string LED assembly aspect brightness.

But in making LED element process, be split into for example a collection of 20,000 LEDs crystal grain from a wafer before this, be encapsulated into the LED element more one by one, in the manufacturing and cutting procedure of wafer, may produce a small amount of individual difference, for avoiding properties of product difference excessive, generally be by a test with LED crystal grain by the gross, and according to its positive drive voltage classify (Bin-Sorting), be about to each LEDs crystal grain under certain fixed drive electric current, screen according to positive drive voltage Vf numerical values recited and the luminosity of crossing over these LED crystal grain the two poles of the earth.The required positive drive voltage deviation average of crystal grain is far away excessively for lighting, and when for example surpassing 50mV, promptly is included into another classification, guarantees that thus the forward voltage of output crystal grain meets a narrower scope interval.And aspect in addition, this kind classification needs to eliminate earlier about about one one-tenth crystal grain usually, and cost increases thereupon.

Subsequently in the encapsulation process of element, also may produce a small amount of individual difference because of worker's difference of all technology, make with a collection of each LED element that dispatches from the factory, as shown in Figure 2, positive drive voltage Vf under identical drive current If (is 20mA as above-mentioned electric current) still is a parameter, and scope may be in the middle of 3.0V～4.0V, and V _fValue probability distribution (Probability Distribution) P (V _f) be the curve of falling the clock among the figure, this probability P (V _f) distribution map is the distribution near a normal function Normal Distribution, its distribution function P (V _f), can write an accepted way of doing sth (1):

$P\left(V_f\right)=\frac{1}{\mathrm{\ΔV}\sqrt{2\mathrm{\π}}}e\frac{-{(V_f-V_{\mathrm{av}})}^2}{2\mathrm{\Δ}{V}^2}-------------------\left(1\right)$

The average forward bias value Vav=3.5V of LED element by the gross wherein, and the standard deviation Δ V distribution Yue Keda 0.2V scope of output element by the gross, that is, three one-tenth many elements being arranged approximately when lighted by drive current, the 3.5V gap of forward bias and mean value surpasses 0.2V.Before the LED by the gross of same technology element dispatches from the factory, all can measure the forward voltage V under same forward current earlier _f, use the function that calculates this batch LED element probability distribution, promptly

V wherein _fRepresent the forward bias of each LED element under forward current Is.

For making properties of product be easy to expection and control, the LED element of making will be classified according to situations such as forward bias, luminosity and the uniformity separately again, and classification is thinner, and nicety of grading requires higher, and the cost of classifying and the cost of collection and treatment are higher.Generally speaking, often with forward bias gap 0.1V be one sub-category, therefore as under the above-mentioned 1V difference, all products need be divided into 10 classifications approximately.Yet forward bias error with 0.1V, generally, can cause about 20% current error, also therefore produce about 20% luminance errors the blue light or the green glow of RGB illuminating module, its amount of variability needs the backlight of high evenness to one, still needs to improve again.

From the above, because when detecting with the 20mA drive current, average positive drive voltage was 3.5V, if do not classify before this batch LED element dispatched from the factory, generally, all needed driving total voltage Vcc can be designed to 35V selecting serial connection for example during the circuit design of 10 white light LEDs elements.But in fact, unless through special screening, otherwise, when component number more after a little while, the forward bias that normal drive current institute actual needs can be provided is the mean value on the deviation theory very easily.Consulting shown in the I-V curve of Fig. 3 typical case LED element, generally is V _fValue is higher, electric current I _fBigger; And electric current I _fWith the relation of luminosity B as shown in Figure 4, after surmounting basic drive current, luminosity increases with the current value substantial linear.In case the positive drive voltage summation of this 10 LEDs element drops on for example 38V greater than theoretical value 35V, then promote with above-mentioned predetermined Vcc=35V, flow through the drive current of whole string LED assembly may rapid drawdown to 12mA, this kind drive condition will make the brightness of whole string LED and original design load difference reach 40%, produce unacceptable luminance shortage problem.

Especially present large LCD display, LED the number that its needed backlight is used is very many, with a LCD TV of 42 o'clock, need white light LEDs (20mA) or 3000 groups of RGB LED of about 3000 to constitute approximately, if the serial connection LED assembly that all is connected in series 30 with every string constitutes, then the entire backlight plate needs 100 strings approximately.Even classify according to aforesaid way, not only be forced to divide into more than ten classes, cause considerable classification, storage management, reach use cost; And in case with the use in parallel of the tandem of difference classification, under the identical condition of driving voltage, more can produce the uneven problem of the luminous number of LED inter-module of respectively going here and there, cause the part tandem result dulller than other tandems, so for large-sized monitor, even must consider that each the LEDs element in each string serial connection LED assembly all belongs to same classification.

At present, another kind of known technology is to utilize a higher DC voltage Vcc to drive as shown in Figure 5, and other provides a current source Is, reaches the scheduled current amount really with the forward current If of this serial connection LED assembly of confirming to flow through.If the Vf distribution when all the LED elements 10 in this LED assembly dispatch from the factory is all at 3.0V～4.0V, then need to be as the criterion with maximum voltage requirement 4V, multiply by needs to drive 30 elements, and provide direct voltage source Vcc more than the 120V, add the pressure drop of calculating current source Is, actual required Vcc is promoted to about 122V approximately again.Utilize current source Is to provide obviously to exceed the electric current I f value of high demand, met expectedly and light to guarantee to be connected in series the LED assembly.Yet utilize the method that following shortcoming is arranged:

1. the power supply service efficiency is lower: can't send the more light of high brightness by corresponding driving LED assembly because surpass the electric energy of actual demand, so when the serial connection LED assembly of classifying according to voltage in actual luminous and the precedent equates, last mode classification will only need consume the electric energy of about the manner 87%;

2. utilize the current source of fixing output current and painstakingly apply the combination of the power supply of high voltage,, go here and there LED, must provide 100 high voltage bearing current source Is in the tool display, thereby manufacturing cost increases hurriedly for correspondence drives 100 according to aforementioned calculating;

3. if constitute backlight with RGB three look crystal grain, then the number of high pressure resistant current source and cost more need to increase 3 times again.

Thereby the invention provides a kind of many serial connection LED assemblies, its number is increased, and control the greatly forward bias when not needing to distinguish the feeding normal drive current of this serial connection number, the degree that still can meet average level, get rid of the demand of accurate classification LED element on the one hand, reduce meaningless classification and management cost; High-tension low current source only must be used in the aspect in addition, do not need painstakingly to select the high-tension current source of controllable current value, further reduce manufacturing cost, especially the light-uniforming technology that the applicant had of can arranging in pairs or groups, make that each intergranular luminosity of respectively going here and there the LED inter-module and being connected in series in the LED assembly is inhomogeneous, can be covered fully and not obvious, reduce the threshold that the LED element is selected in the backlight when making display significantly, to reach the double effects of least cost and the highest power supply service efficiency.

[summary of the invention]

The object of the present invention is to provide a kind of backlight of tool serial connection LED assembly, utilize the LED element serial connection of abundant number, when the tandem after the feasible serial connection is passed into drive current, driving voltage meets in fact by the gross that LED element mean value multiply by granule number, uses the demand of getting rid of the accurate classification of LED.

An of the present invention purpose is to provide a kind of backlight of tool serial connection LED assembly, utilizes the LED element serial connection of abundant number, makes that the required driving voltage of tandem after the serial connection meets expection, uses the demand of getting rid of higher-priced fixed current value current source.

Another object of the present invention is to provide a kind of display of tool serial connection LED assembly, wherein backlight is to utilize the LED element serial connection of abundant number, when the tandem after the feasible serial connection is passed into drive current, driving voltage meets in fact by the gross that LED element mean value multiply by granule number, uses the demand of getting rid of the accurate classification of LED element; And make the required driving voltage of tandem after the serial connection meet expection, use the demand of getting rid of higher-priced fixed current value current source, thereby reduce manufacturing cost significantly.

Another purpose of the present invention is to provide a kind of display of tool serial connection LED assembly, utilize forward and backward two reflector plates, with the luminous homogenize that between the reflecting element of front and back, repeatedly reflects of serial connection LED assembly in the backlight, and only have light the past reflecting element partly to penetrate, make light source by complete homogenising so back and forth, further cover the situation of serial connection LED assembly non-uniform light, thereby allow that LED element screening threshold significantly reduces.

A further object of the present invention is to provide the demand of the accurate classification of a kind of LED of eliminating element, thereby reduces the backlight method for making of the tool serial connection LED assembly of manufacturing cost significantly.

A further object of the present invention is to provide a kind of forward and backward two reflector plates that utilize, and makes the luminous homogenize that repeatedly reflects between the reflecting element of front and back of serial connection LED assembly, is connected in series the backlight method for making of LED assembly with the tool of covering serial connection LED assembly non-uniform light.

The tool of reaching the foregoing invention purpose is connected in series the display of backlight, method for making and this backlight of tool of LED assembly, mainly comprise one group of power supply device, at least two groups are connected in parallel to each other, are subjected to jointly this power supply device activation luminous and comprise a plurality of serial connection LED assembly and one group of liquid crystal module of LED elements of serial connection each other respectively.Wherein this power supply device provides electric power and gives serial connection LED assembly and liquid crystal module, this serial connection LED assembly is the electric power that provided by power supply device, and the number of above-mentioned serial connection LED is to make when this at least two groups serial connection LED assembly is lighted, the whole string activation voltage of any one of this at least two group serial connection LED assembly deducts in this assembly the difference of the number product of LED in the average activation voltage of above-mentioned LED element and this assembly, reaches a prearranged multiple less than the product of above-mentioned LED component number in the SS difference of the indivedual activation voltages of above-mentioned LED element in this assembly and this assembly; By this, the individual difference of above-mentioned LED element influences the influence degree of this activation voltage that this power supply device provides, and is lowered this prearranged multiple.This liquid crystal module is that the power supply that provided by this power supply device makes its display frame, and be subjected to being connected in series the LED assembly in mode backlight as the liquid crystal module group backlight source; And more can arrange in pairs or groups one group of dodging device of this backlight uses, this dodging device mainly comprises an even mating plate, an one front-reflection part and a back reflection spare, be the front-reflection part to be arranged at even mating plate be connected in series the LED inter-module with this at least two group, and back reflection spare is arranged at this at least two group serial connection LED inter-module away from this even mating plate side, wherein this back reflection spare reflectivity is near reflection fully, and the reflectivity of this front-reflection part is to be higher than its penetrance but less than this back reflection spare reflectivity, this dodging device just sees through the different reflectivity of front-reflection part and back reflection spare, the Coefficient of Utilitization of light source that can serial connection LED assembly increases, and reaches the purpose of the homogenising of effective utilization of electric power and light source.

[brief description of drawingsfig]

Fig. 1 lights schematic diagram for known several serial connection LED elements are driven by single dc source;

Fig. 2 is the positive drive voltage V of known LED element under the 20mA drive current _fValue probability distribution figure;

Fig. 3 is the I-V graph of relation of general LED element;

Fig. 4 is lighted by activation for general LED element electric current I _fWith luminosity B graph of relation;

Fig. 5 is the known schematic diagram that utilizes current source Is activation to light serial connection LED, illustrates that institute's voltage vcc that provides need surpass the highest demand voltage of single LEDs and multiply by the LED number that is connected in series;

Fig. 6 has the backlight first preferred embodiment structure square of serial connection LED assembly for the present invention

Figure;

Fig. 7 is the structural representation of Fig. 6 embodiment;

Fig. 8 is among Fig. 6 embodiment, the probability distribution curve map of the total forward bias VfT of used serial connection LED assembly under the 20mA drive current;

Fig. 9 is many group serial connection LED assembly set-up mode schematic diagrames on the backlight of Fig. 6 embodiment;

Figure 10 respectively is connected in series the total forward bias I-V relation curve distribution map of LED assembly under the 20mA drive current for Fig. 6 embodiment's;

Figure 11 is the backlight circuit diagram of Fig. 6 embodiment, illustrates that power supply device is connected in series LED assembly circuit relation with each;

Figure 12 for each group serial connection LED assembly of Figure 11 when applying identical forward voltage Vcc, flow through electric current I and total forward bias V separately _FTThe curve map of relation;

Figure 13 is luminosity and the electric current I V-If graph of relation of Fig. 6 embodiment, and the control model of adjusting backlight brightness is described;

Figure 14 has for the present invention in backlight second preferred embodiment of serial connection LED assembly, and each is connected in series the reflexed serial connection of LED assembly and arranges schematic diagram; And

Figure 15 is the first preferred embodiment structural representation of display of the present invention, and the structural relation of dodging device and backlight is described.

[main element symbol description]

10 LED elements, 12 dc sources, 30 backlight

32 power supply devices 34,34 ' serial connection LED assembly

340,340 ' LED element 36,36 ' liquid crystal module

38 ' dodging device, 382 ' front-reflection sheet

384 ' back reflection sheet, 386 ' even mating plate

[specific embodiment]

Figure 6 shows that the present invention has the calcspar of the backlight structure of serial connection LED assembly, mainly comprises: backlight 30 and liquid crystal module 36; Then comprise the serial connection LED assembly 34 that power supply device 32 and at least two groups are connected in parallel to each other in the backlight 30.

Wherein, power supply device 32 is for example to be used to provide the serial connection LED assembly 34 and liquid crystal module 36 energy that two strings are connected in parallel to each other; And as shown in Figure 7, every group of serial connection LED assembly 34 all comprises a plurality of LED elements 340 of serial connection each other, and each LED element 340 emission side all is provided with in the same direction; 36 of liquid crystal module be to should at least two groups serial connection LED assembly 34 be provided with, and be subjected to above-mentioned serial connection LED assembly 34 and illuminate in mode backlight.

The I-V curve of typical case LED element generally is V _fValue is higher, electric current I _fBigger, wherein for same LEDs element, electric current I _fWith the relation of luminosity B, after surmounting basic drive current, luminosity increases with the current value substantial linear.Yet in processing procedure, various conditions are difference and exerting an influence slightly, even the LED element that same company makes, even same wafer cuts out the packaged element that goes out of LED crystal grain, and every I-V curve is also difference to some extent each other.Therefore, if N the LED element with a collection of manufacturing is cascaded, at forward current I _fUnder total forward bias V of total series connection _f(T)=V _f(1)+V _f(2)+... .V _f(N), consult shown in Figure 8, according to the mathematical theory of Normal Distribution, its series connection after forward bias V _FTProbability distribution function P (V _FT) can be write as:

$P\left(V_{\mathrm{fT}}\right)=\frac{1}{\left(\mathrm{\Δ}{V}_T\right).\sqrt{2\mathrm{\π}}}e\frac{-{(V_{\mathrm{fT}}-V_{\mathrm{avT}})}^2}{2{\left(\mathrm{\Δ}{V}_T\right)}^2}......\left(2\right)$

V wherein _AvT=NxVa...... (3)

$\mathrm{\Δ}{V}_T=\sqrt{N}\×\mathrm{\ΔN}...\left(4\right)$

The LED element of above example is distributed as example, if after 100 LED element series connection, and the total bias voltage V of its forward _FTTheoretical value, by being (V shown in the formula (3) _FT) av=100 * 3.5=350V, and its standard deviation:

Compared to probability distribution figure P (V shown in Figure 2 _f), the average forward bias of indivedual LED elements is 3.5V, standard deviation is 0.2V; Can find the forward bias theoretical value (V of series connection back whole string LED assembly _FT) _Av=350V still multiply by the series element number for the individual elements theoretical value; But the forward bias standard deviation Δ V of series connection back LED assembly relatively, _T=2.0V, obviously the numerical value than due 0.2V * 100 hurriedly subtracts, that is, though the tandem LED assembly that discloses according to the present invention, before manufacturing not earlier through the classification process of LED element, and the distribution proportion obvious constriction of the summation distribution of its forward bias during still than original single.Can be drawn by above formula, if N LEDs element series connection is arranged, its distribution can be reduced into original scope

Doubly, just be connected in series the LED element of 100 non-classified, the forward bias value of tandem assembly can be condensed to 1/10th of original theoretical value and tandem number product.For example first preferred embodiment has the series connection of 400 LEDs elements, then its V _fDistribution can be reduced into original

Even with four times of standard deviations as the boundary line, V _FTMinimum of a value be about 350-(4x2.0)=342V, maximum is about 350+ (4 * 2.0)=358V, the forward bias gap of multi-string LED inter-module at most also only has 358V-342V=16V, still has compared to the deployment conditions of single LEDs element of script non-classified and dwindles; Yet four times of standard deviations mean and all are arranged in this scope more than 99% in all tandem LED assemblies of producing that especially when the series LED component number increased again, the positive bias voltage intensity of whole string LED assembly also can be more obvious.

Utilize above principle, the present invention's second preferred embodiment will be example with the backlight of a LCD TV of 42 o'clock, calculate actual state: at this, the brightness of fixed its backlight is 6000cd/m ², the area of backlight is about 0.54m ², therefore the total brightness of the LED that needs is 3200cd, when the white light LEDs element at forward current I _fUnder=the 20mA, when average every luminosity was 1cd, then a white light LEDs number of these backlight needs was 3200.

The high electric current cost of power supply cost low voltage of considering general high voltage low current is low, so the power supply of a same 400W, if with 5V, the cost of 80A power supply will be far above 1000V, the power supply cost of 0.4A.Because the high pressure low-current power supply is used in the backlight of original C CFL cold-cathode tube in a large number at present.Therefore among the present invention, also the frequency converter (Inverter) with general cold-cathode tube is that power supply illustrates, but the present invention does not limit the use of other power supplys.Therefore CCFL Inverter is a high voltagehigh frequency rate AC power, must add a bridge rectifier and filter capacitor at output and just can become a high-voltage dc power supply and use.Yet other general high-voltage DC power supplies all utilize the DC-DC translation circuit, utilize a low-voltage dc power supply Buck.Converter circuit conversion to use for HVDC.

In this example, it need use 3200 white light LEDs, see through foregoing principle, utilize the more LEDs series connection to use, more can dwindle the range of variation of its total forward bias, thus in this example as shown in Figure 9, select 400 LEDs elements series connection to be example, wherein every string LED assembly has 400 LEDs elements, the light source in the backlight then by ST1, ST2 ... .ST8 etc. 8 string LED assemblies institute is common to be constituted.

If wherein the average forward voltage of each single white light LEDs element (under electric current I f=20mA) is 3.5V, and the forward bias distribution of single LEDs is 3.0V～4.0V, after then the series connection of 400 LEDs is the LED assembly, total forward voltage theoretical value of each assembly demand is 1400V, and the distribution of total forward bias of tandem LED assembly as shown in figure 10, will be limited in in 1390V～1410V.

As shown in figure 11 eight groups are connected in series the fully anodal of LED assemblies 34 ' and receive the power Vcc that voltage is 1400v, it is same and be connected to the resistance R s of one 10 Ω that each is connected in series the earth terminal of LED assembly 34 ', help voltage Vs as returning of operating current IT, and the adjustment Control of Voltage of power Vcc.Because dc source Vcc is chosen to be 1400V, then the possibility distribution is compared to desirable total forward bias value, error is only in 1%, because the forward voltage difference of LED inter-module of respectively going here and there is very little, below will calculate proof, even with eight string serial connection LED assemblies, 34 ' in parallel fully the use, only with single power supply device activation, apply identical voltage vcc to above-mentioned serial connection LED assembly 34 ', it is also extremely limited that each is connected in series LED assembly 34 ' luminous intensity difference each other, can't be observed easily.

Because total forward bias value VT (I)=V1 (I)+V2 (I)+----V400 (I) of each string LED assembly, and the I-V curve of each LED element difference all to some extent, when making drive current fixedly, always forward bias is all variant for every string LED assembly actual.On the contrary, if shared forward voltage Vcc is selected stuck-at-400V, then respectively go here and there the LED assembly total forward bias VT (I) and electric current I relation curve as shown in figure 12.

Wherein, when fixed current was 20mA, total bias voltage was required to be this string LED assembly of 1410V, the forward current I when Vcc=1400V _f, with slightly estimate for

Relatively total bias voltage is this group LED assembly of 1390V during forward current 20mA, the forward current I when Vcc=1400V _fFor

As seen, according to manufacture method of the present invention, even at first step is to be connected in series without the LED element 340 ' of selecting classification in detail fully, when serial connection LED component number is enough big, in second step at least two groups of being formed are connected in series the 34 ' parallel connection of LED assembly, with single group of power Vcc activation, each drive current that is connected in series LED assembly 34 ' all quite near original predetermined desirable drive current If=20mA and total work electric current of the Rs that can determine to flow through still quite near ideal value 160mA (20mA * 8), and the forward current difference that respectively is connected in series between LED assembly 34 ' also is limited in 5%.Further, because the brightness of LED is directly proportional with electric current approximately, therefore respectively be connected in series the mean flow rate difference of LED assembly 34 ' also in 5%.

Further then can adjust Vcc voltage to for example 1300V (3.25V * 400 LEDs) again if will adjust backlight brightness, the forward current If ≈ 15mA of the serial connection LED assembly 34 ' of every string then, utilize luminosity and the electric current I V-If graph of a relation of Figure 13, can find out for 75% when its luminosity B is about aforementioned 20mA.Therefore as long as the voltage swing of modulation Vcc can be controlled the respectively luminosity of the serial connection LED assembly 34 ' of string.Because eight string LED assemblies are under identical forward current drives, forward bias possible error each other is only about 1%; Therefore when in parallel and when applying identical voltage and driving, the forward current errors also will be limited in 5% individually.

Shown in last embodiment, be serially connected with 400 LEDs elements when a string LED assembly is actual, and the forward voltage of crossing over every LEDs element is when being about 3.5V, the head and the tail potential difference of crossing over a string LED assembly will reach 1400V; In case the engineer of design circuit does not look into, mistake will be put in order string LED assembly and be become with the single reflexed " U " the font distribution design, when the two ends spacing is not enough, jump the risk of electricity with promoting the direct short-circuit of LED assembly both end voltage.

Be improving safety, the present invention has backlight second preferred embodiment of serial connection LED assembly, the LED distribution of backlight will be arranged as shown in figure 14, ST1 be arranged at as shown in the figure uppermost component and from top to bottom be provided with in proper order ST2 ... ST8, and with 8 string LED assembly ST1, ST2 ... ST8 arranges for 80 times with every string LED assembly reflexed, makes each reflexed arrange and will only be connected in series 5 LEDs elements.Therefore, between the end of first order and second order, potential difference is 35V only.Utilize the serial connection of the method can reduce voltage difference between each LEDs, guarantee the security of connecting up on the pcb board.

Certainly, as be familiar with present technique field person and can understand easily, though the foregoing description all is to be example with the white light LEDs element, but the LED-backlit plate that utilizes RGB three-color LED element to constitute does not also have can not, only the forward bias voltage may of R, G, B three-color LED element is also inequality, therefore LED element of all kinds must have many string assemblies of one's own, and drives with different voltage according to color separately.For example go up backlight of 42 o'clock in the example, need 3200 groups of R respectively, G, the LED assembly of B constitutes jointly, if and utilize per 400 LEDs elements to be connected into a string monochromatic LED assembly, then every look LED assembly all needs 8 strings, and 8 string LED of same color can utilize same high-voltage DC power supply supply thereby need three different voltage sources, when needs are adjusted its colour temperature, also can utilize and adjust VccR, VccG, the size of three supply voltages of VccB, can adjust red individually, green, the difference supply electric current of Lan Sanse, thereby produce the brightness ratio that needs, to reach required any colour temperature.

Deeply inquire into again because LED element processing procedure difference, though each LEDs element under same current drives, its output light place also may reach ± 20% difference.If reach most economical structure, reduce the demand of category filter, must avoid the beholder to find the interelement luminance difference of this kind LED immediately this kind luminance difference opposite sex homogenising.

Therefore, when disclosed above-mentioned backlight is formed display, the preferred embodiment of this case display as shown in figure 15, be after finishing above-mentioned backlight, in to should one group of dodging device 38 ' being set the backlight place, the dodging device 38 ' of present embodiment comprises the reflecting element that former and later two reflectivity are different, example is interpreted as front-reflection sheet and back reflection sheet 382 ', 384 ' in this example, the reflectivity of back reflection sheet 384 ' is planned to 100% reflection fully, and only front-reflection sheet 382 ' then has the part transmission.Thus, no matter the light that makes LED element 340 ' be sent exposes to front-reflection sheet 382 ' or back reflection sheet 384 ', all roughly be reflected, and constantly between two reflector plates back and forth, just locate to appear at last in front-reflection sheet 382 ', through the homogenize of even mating plate 386 ', finally expose to liquid crystal module 36 ' again.So utilize the part Transflective sheet of floor height reflection, the optical cavity that repeatedly reflects of total reflection sheet formation with the bottom surface increases this serial connection LED assembly 34 ' institute's isolychn homogenising.

Utilize this technology, if with 10% transmission, 90% the reflection partial reflection film (Partial Transmission Films) as front-reflection part material, then can be 10 times of the improving uniformities of LED element according to experimental result.That is to say, though original LED interelement, luminosity reaches ± 20% difference, and through after this structure homogenize, its inhomogeneities is remaining ± 2% at most only; In addition according to the aforementioned analysis of this case, each is connected in series the luminosity difference less than 5% of LED inter-module.By this, the advantage of the LED element of need not classifying is thoroughly performed to ultimate attainment, and the luminosity problem of non-uniform of unclassified LED element is covered the stage of observing to being difficult for.

By above explanation as can be known, utilize plurality of LEDs element series connection, not only can dwindle the forward bias difference of serial connection LED inter-module, thereby the multi-string LED assembly of congenerous can be in parallel and with one group of power drives activation.And the screening threshold of the forward voltage of each LED element, luminance difference can significantly be reduced, thereby manufacturing cost subtracts greatly, and makes very economical backlight.Certainly, serial connection LED number such as ripely can understand easily in this operator, as long as can reach for example 36, can make the product of deviate and LED component population of the more single LEDs element of deviate of total forward bias of serial connection LED assembly reduce by six times, make that for example 12 o'clock panels can adopt for example two groups of low-cost LED of serial connection assemblies parallel connection.

The above person of thought, preferred embodiment only of the present invention, when not limiting scope of the invention process with this, promptly all according to claims scope of the present invention and variation of description of the invention simple equivalent that content is done and modification, all still belong in the scope of patent letter lid of the present invention.

Claims (13)

1. the backlight with serial connection LED assembly is characterized in that, comprising:

One group of power supply device; And

At least two groups are connected in parallel to each other, are subjected to jointly this power supply device activation luminous and comprise a plurality of serial connection LED assemblies of LED elements of serial connection each other respectively, the number of above-mentioned serial connection LED is to make when this at least two groups serial connection LED assembly is lighted, and any one the whole string activation voltage that this at least two group is connected in series the LED assembly deducts in this assembly the difference of the number product of LED in the average activation voltage of above-mentioned LED element and this assembly and reaches a prearranged multiple less than the product of above-mentioned LED component number in the SS difference of the indivedual activation voltages of above-mentioned LED element in this assembly and this assembly; By this, the individual difference of above-mentioned LED element influences the influence degree of this activation voltage that this power supply device provides, and is lowered this prearranged multiple.

2. backlight as claimed in claim 1 is characterized in that, wherein this difference is the sixth less than above-mentioned LED component number product in this standard deviation and this assembly.

3. backlight as claimed in claim 1 is characterized in that, wherein this difference is less than 1/10th of above-mentioned LED component number product in this standard deviation and this assembly.

4. backlight as claimed in claim 1 is characterized in that, wherein the above-mentioned LED element emission side in this at least two groups serial connection LED assembly all is provided with in the same direction.

5. as claim 1,2,3 or 4 described backlight, it is characterized in that, more comprise one group of dodging device.

6. backlight as claimed in claim 5 is characterized in that, wherein this group dodging device comprises:

One even mating plate;

One group is arranged at this even mating plate respectively and is connected in series the front-reflection part of LED inter-module with this at least two group, and is arranged at the back reflection spare of this at least two groups serial connection LED assembly away from this even mating plate side;

Wherein this back reflection spare reflectivity system is near reflection fully, and the reflectivity of this front-reflection part is to be higher than its penetrance but less than this back reflection spare reflectivity.

7. the display with serial connection LED assembly backlight is characterized in that, comprising:

One group of backlight with serial connection LED assembly comprises:

One group of power supply device; And

At least two groups are connected in parallel to each other, are subjected to jointly this power supply device activation luminous and comprise a plurality of serial connection LED assemblies of LED elements of serial connection each other respectively, the number of above-mentioned serial connection LED is to make when this at least two groups serial connection LED assembly is lighted, the activation voltage of this at least two group serial connection LED assembly reduces in this assembly the difference of the number product of LED in the average activation voltage of above-mentioned LED and this assembly, is that the product less than above-mentioned LED number in the SS difference of the individual other activation voltage of above-mentioned LED in this at least two assembly and this assembly reaches a prearranged multiple; By this, to influence the influence degree of this activation voltage that this power supply device provides be according to being lowered this prearranged multiple to the individual difference of above-mentioned LED; And

One group to should at least two groups being connected in series the liquid crystal module that the LED assembly is provided with.

8. display as claimed in claim 7 is characterized in that, wherein the light emission direction of this at least two groups serial connection LED assembly is to be configured to towards this liquid crystal module.

9. display as claimed in claim 7 is characterized in that, wherein this difference is less than 1/10th of above-mentioned LED number product in this standard deviation and this assembly.

10. as claim 7,8 or 9 described displays, it is characterized in that wherein this backlight more comprises one group of dodging device.

11. display as claimed in claim 10 is characterized in that, wherein this group dodging device comprises:

One even mating plate;

One group is arranged at this even mating plate respectively and is connected in series the front-reflection part of LED inter-module with this at least two group, and is arranged at the back reflection spare of this at least two groups serial connection LED assembly away from this even mating plate side;

Wherein this back reflection spare reflectivity system is near reflection fully, and the reflectivity of this front-reflection part is higher than its penetrance but less than this back reflection spare reflectivity.

12. a manufacturing has the method for the backlight of serial connection LED assembly, it is characterized in that, comprises the following steps:

A) planning at least two groups comprise a plurality of serial connection LED assemblies of the LED element of serial connection each other respectively; And

B) provide a power supply device, supply activation in parallel and light this at least two groups serial connection LED assembly;

Wherein, the number of above-mentioned serial connection LED is to make when this at least one group serial connection LED assembly lighted, the whole string activation voltage of any one of this at least two group serial connection LED assembly deducts in this assembly the difference of the number product of LED in the average activation voltage of above-mentioned LED element and this assembly, reaches a prearranged multiple less than the product of above-mentioned LED component number in the SS difference of the indivedual activation voltages of above-mentioned LED element in this assembly and this assembly; By this, the individual difference of above-mentioned LED element influences the influence degree of this activation voltage that this power supply device provides, and is lowered this prearranged multiple.

13. manufacturing as claimed in claim 12 has the method for the backlight of serial connection LED assembly, it is characterized in that more comprise the step c) that one group of dodging device is set, wherein this group dodging device comprises:

One even mating plate;

One group is arranged at this even mating plate respectively and is connected in series the front-reflection part of LED inter-module with this at least two group, and is arranged at the back reflection spare of this at least two groups serial connection LED assembly away from this even mating plate side;

Wherein this back reflection spare reflectivity is near reflection fully, and the reflectivity of this front-reflection part is higher than its penetrance but less than this back reflection spare reflectivity.

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