CN108271293B - A kind of white light LED color temperature control method and system - Google Patents
A kind of white light LED color temperature control method and system Download PDFInfo
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Abstract
The invention discloses a kind of white light LED color temperature control method and systems.The method and system obtain the average driving current formula of the white light LEDs under the first peak value wavelength model and dipulse drive mode of white light LEDs under DC driven mode first；Then the equivalent peak wavelength change amplitude minimal condition of the white light LEDs under the dipulse drive mode is determined according to the first peak value wavelength model and the average driving current formula.Each parameter by controlling the white light LEDs meets the equivalent peak wavelength change amplitude minimal condition, it can control the color temperature change range of the white light LEDs minimum, to make the white light LED color temperature keep stable state, the stability of white light LED color temperature is improved.
Description
Technical field
The present invention relates to technical field of LED illumination, more particularly to a kind of white light LED color temperature control method and system.
Background technique
It is with the semiconductor illumination technique that light emitting diode (Light Emitting Diode, referred to as LED) is core
This century one of emerging high-tech sector most with prospects, LED have compared with the conventional light sources such as incandescent lamp and fluorescent lamp
The advantages that extra long life, fast response time, luminous efficiency are high, pollution-free, environmentally protective.LED light source will be used as a kind of normal light
Source enters illumination market, and lighting quality, commercial viability and the economic value etc. of product are all the factors to be considered carefully.Colour temperature
It is the index for indicating that light source light spectrum quality is most general, therefore requires to become high-power white as the light source color temperature for measuring lighting quality
One of the condition that light LED must satisfy.
White light LEDs are made of blue-light LED chip and YAG fluorescent powder.The blue color spectrum of blue-light LED chip transmitting will excite
YAG fluorescent powder generates yellow spectrum, and by two parts spectrum, (LED chip emits blue color spectrum to the colour temperature of white light LEDs and YAG is glimmering
Light powder generates yellow spectrum) it is determined.Since phosphor emission spectrum and LED chip excitation spectrum are there are close relation, with
LED chip peak wavelength shift will cause fluorescent powder quantum efficiency to change, and the spectral component ratio of each color also changes,
Device load difference current condition leads to white light color offset problem.Under direct current and PWM drive mode, it will all cause illumination system
The colour fluctuation problem of system, correlative study show in RGB White-light LED illumination system, the variation of spectrum amplitude 1%, peak value wave
The offset of long 1nm will all cause significant color change.Although requirement of the distinct device to light source color temperature is different, but if
Compare the reference color temperature of adaptation beyond human eye, illuminates the physiology to people, psychology can all have a negative impact.
There are two types of more commonly dim drive mode: DC driven and PWM drive mode at present.Under DC driven mode
Device light emitting efficiency is high, but the mode light modulation precision is low.PWM dims degree of regulation height under drive mode, but device is luminous
Efficiency is lower, this is because LED component output light flux and loading current are at non-linear relation.It is driven for DC driven and PWM
Deficiency existing for dynamic model formula, proposes a kind of dipulse drive mode in recent years, which can effectively improve lighting system
Luminous efficiency.The color of White-light LED illumination system is in the presence of complicated dynamic rule, however most of research concentrates on directly at present
The color steady-state characteristic of white light LED part under stream or PWM mode, for the color dynamic of mixed white light LED information display system under dipulse
Characteristic and application study still lack correlative study.Therefore the stabilization of white light LED color temperature how is controlled under dipulse drive mode
The technical issues of property is this field urgent need to resolve.
Summary of the invention
The object of the present invention is to provide a kind of white light LED color temperature control method and systems, by changing model to peak wavelength
White light LED color temperature control is realized in the control enclosed, and color temperature change range can be made minimum, improve the stability of white light LED color temperature.
To achieve the above object, the present invention provides following schemes:
A kind of white light LED color temperature control method, which comprises
The first peak value wavelength model of white light LEDs under DC driven mode is determined according to diode Xiao Telai model；
Obtain the average driving current formula of the white light LEDs under dipulse drive mode；
The dipulse drive mode is determined according to the first peak value wavelength model and the average driving current formula
Under the white light LEDs equivalent peak wavelength change amplitude minimal condition；
It keeps stablizing shape according to the colour temperature that the equivalent peak wavelength change amplitude minimal condition controls the white light LEDs
State.
Optionally, the first peak value wave that white light LEDs under DC driven mode are determined according to diode Xiao Telai model
Long model, specifically includes:
The I-E characteristic of the white light LEDs is determined according to diode Xiao Telai model:
Wherein I is electric current, and β is constant relevant to doping concentration and junction area, TjFor junction temperature, e is unit charge, and V is
Voltage, RsFor series resistance, n is ideal factor, and k is Boltzmann constant；
Obtain the relationship between semiconductor PN load voltage and forbidden bandwidth energy:
Eg=Ve-IRse-eΔVel (2)
Wherein EgFor forbidden bandwidth energy, Δ VelFor physical constant；
The formula (1) is substituted into the formula (2), obtains forbidden bandwidth energy theorem:
Wherein V0For barrier voltage；
The peak wavelength and forbidden bandwidth of the white light LEDs are determined according to semiconductor material photon transition energy balance principle
Relationship between energy:
Wherein λpFor peak wavelength, h is Planck's constant, and c is the light velocity, EgFor forbidden bandwidth energy, EDFor alms giver's latent electricity
Sub- energy, EAFor acceptor's bound electron energy, e is unit charge, and ε is dielectric constant, and R is acceptor-donor pair distance, ε0It is true
Empty dielectric constant；
The formula (3) are substituted into the formula (4), obtain the first peak value wavelength model:
Optionally, the average driving current formula for obtaining the white light LEDs under dipulse drive mode, it is specific to wrap
It includes:
Obtain the average driving current formula:
Iave=DIH+(1-D)IL (6)
Wherein IaveFor the average current under the dipulse drive mode, D is duty ratio, IH、ILFor second order electric current.
Optionally, described that double arteries and veins are determined according to the first peak value wavelength model and the average driving current formula
The equivalent peak wavelength change amplitude minimal condition for rushing the white light LEDs under drive mode, specifically includes:
Obtain the junction temperature theoretical expression of the white light LEDs:
Tj=(Rjc+Rhs)*(IV)kh+Ta (7)
Wherein RjcFor device thermal resistance, RhsFor the heat radiator thermal resistance of the white light LEDs, khFor heat-dissipating power coefficient, TaFor
Environment temperature；
The formula (6) are substituted into the formula (7), obtain the knot of the white light LEDs under the dipulse drive mode
Warm expression formula:
Tj=(Rjc+Rhs)[(IH-IL)khVaveD+ILVavekh]+Ta (8)
Wherein VaveFor the average voltage under the dipulse drive mode；
The relationship between the junction temperature and the duty ratio is obtained according to the formula (8):
The peak wavelength, the junction temperature and the duty ratio D are obtained according to the formula (5) and the formula (8)
Between relationship:
The first equivalent peak wavelength model of the white light LEDs is obtained according to the formula (5):
Wherein λ 'pFor equivalent peak wavelength；
The formula (11) are substituted into the formula (5), obtain the pass between the equivalent peak wavelength and the junction temperature
System:
The formula (5), (9), (12) are substituted into the formula (10), obtain the equivalent peak wavelength and the duty
Relationship than between:
dλ'p={ nkTj[ln(IH)-ln(IL)]+nk[ln(IL)-ln(β)-2ln(Tj)-2](Rjc+Rhs)(IH-IL)
khIaveVave}dD (13)
According to the formula (13) obtain the equivalent peak wavelength to the duty ratio derivation be 0 in the case of minimum item
Part expression formula:
(dλ'p)min=nkTj[ln(IH)-ln(IL)]+nk[ln(IL)-ln(β)-2ln(Tj)-2](Rjc+Rhs)(IH-IL)
khIaveVave=0 (14)
The equivalent peak wavelength change of the white light LEDs under the dipulse drive mode is determined according to the formula (14)
Amplitude minimal condition are as follows:
Optionally, the colour temperature that the white light LEDs are controlled according to the equivalent peak wavelength change amplitude minimal condition
Stable state is kept, is specifically included:
Control the average current I of the white light LEDsave, the second order electric current IHAnd IL, the device thermal resistance Rjc, institute
State heat radiator thermal resistance Rhs, the heat-dissipating power coefficient khAnd the average voltage VaveMeet the formula (15), so that institute
The colour temperature for stating white light LEDs keeps stable state.
The invention also discloses a kind of white light LED color temperature control system, the system comprises:
First peak value wavelength model obtains module, white under DC driven mode for being determined according to diode Xiao Telai model
The first peak value wavelength model of light LED；
Average driving current formula obtains module, for obtaining the average drive of the white light LEDs under dipulse drive mode
Streaming current formula；
Equivalent peak wavelength change amplitude minimal condition determining module, for according to the first peak value wavelength model and institute
It states average driving current formula and determines the equivalent peak wavelength change amplitude of the white light LEDs under the dipulse drive mode most
Small condition；
Color temperature control module, for controlling the white light LEDs according to the equivalent peak wavelength change amplitude minimal condition
Colour temperature keep stable state.
Optionally, the first peak value wavelength model obtains module and specifically includes:
Current-voltage characteristic acquiring unit, for determining electric current-electricity of the white light LEDs according to diode Xiao Telai model
Press characteristic:
Wherein I is electric current, and β is constant relevant to doping concentration and junction area, TjFor junction temperature, e is unit charge, and V is
Voltage, RsFor series resistance, n is ideal factor, and k is Boltzmann constant；
Load voltage and forbidden bandwidth energy relationship acquiring unit, it is wide for obtaining semiconductor PN load voltage and forbidden band
Spend the relationship between energy:
Eg=Ve-IRse-eΔVel (2)
Wherein EgFor forbidden bandwidth energy, Δ VelFor physical constant；
Forbidden bandwidth energy theorem unit obtains forbidden bandwidth energy for the formula (1) to be substituted into the formula (2)
Measure formula:
Wherein V0For barrier voltage；
Peak wavelength and forbidden bandwidth energy harvesting unit, for according to semiconductor material photon transition energy balance principle
Determine the relationship between the peak wavelength of the white light LEDs and forbidden bandwidth energy:
Wherein λpFor peak wavelength, h is Planck's constant, and c is the light velocity, EgFor forbidden bandwidth energy, EDFor alms giver's latent electricity
Sub- energy, EAFor acceptor's bound electron energy, e is unit charge, and ε is dielectric constant, and R is acceptor-donor pair distance, ε0It is true
Empty dielectric constant；
First peak value wavelength model acquiring unit obtains described for the formula (3) to be substituted into the formula (4)
One peak wavelength model:
Optionally, the average driving current formula obtains module and specifically includes:
Average driving current formula acquiring unit, for obtaining the average driving current formula:
Iave=DIH+(1-D)IL (6)
Wherein IaveFor the average current under the dipulse drive mode, D is duty ratio, IH、ILFor second order electric current.
Optionally, the equivalent peak wavelength change amplitude minimal condition determining module specifically includes:
Junction temperature theoretical expression acquiring unit, for obtaining the junction temperature theoretical expression of the white light LEDs:
Tj=(Rjc+Rhs)*(IV)kh+Ta (7)
Wherein RjcFor device thermal resistance, RhsFor the heat radiator thermal resistance of the white light LEDs, khFor heat-dissipating power coefficient, TaFor
Environment temperature；
Junction temperature expression formula acquiring unit obtains the dipulse and drives for the formula (6) to be substituted into the formula (7)
The junction temperature expression formula of the white light LEDs under dynamic model formula:
Tj=(Rjc+Rhs)[(IH-IL)khVaveD+ILVavekh]+Ta (8)
Wherein VaveFor the average voltage under the dipulse drive mode；
Junction temperature and duty cycle relationship acquiring unit, for obtaining the junction temperature and the duty ratio according to the formula (8)
Between relationship:
Peak wavelength and junction temperature and duty cycle relationship acquiring unit, for being obtained according to the formula (5) and the formula (8)
Obtain the relationship between the peak wavelength, the junction temperature and the duty ratio D:
First equivalent peak wavelength model acquiring unit, for obtaining the first of the white light LEDs according to the formula (5)
Equivalent peak wavelength model:
Wherein λ 'pFor equivalent peak wavelength；
Equivalent peak wavelength and junction temperature Relation acquisition unit are obtained for the formula (11) to be substituted into the formula (5)
Relationship between the equivalent peak wavelength and the junction temperature:
Equivalent peak wavelength and duty cycle relationship acquiring unit, for the formula (5), (9), (12) to be substituted into the public affairs
Formula (10) obtains the relationship between the equivalent peak wavelength and the duty ratio:
dλ'p={ nkTj[ln(IH)-ln(IL)]+nk[ln(IL)-ln(β)-2ln(Tj)-2](Rjc+Rhs)(IH-IL)
khIaveVave}dD (13)
Minimal condition expression formula acquiring unit, for obtaining the equivalent peak wavelength to described according to the formula (13)
Duty ratio derivation is the minimal condition expression formula in the case of 0:
(dλ'p)min=nkTj[ln(IH)-ln(IL)]+nk[ln(IL)-ln(β)-2ln(Tj)-2](Rjc+Rhs)(IH-IL)
khIaveVave=0 (14)
Equivalent peak wavelength change amplitude minimal condition determination unit, for determining double arteries and veins according to the formula (14)
Rush the equivalent peak wavelength change amplitude minimal condition of the white light LEDs under drive mode are as follows:
Optionally, the color temperature control module specifically includes:
Colour temperature control unit, for controlling the average current I of the white light LEDsave, the second order electric current IHAnd IL、
The device thermal resistance Rjc, the heat radiator thermal resistance Rhs, the heat-dissipating power coefficient khAnd the average voltage VaveMeet institute
Formula (15) are stated, so that the colour temperature of the white light LEDs keeps stable state.
The specific embodiment provided according to the present invention, the invention discloses following technical effects:
The present invention provides a kind of white light LED color temperature control method and system, and the method and system obtain direct current drive first
Under dynamic model formula under the first peak value wavelength model and dipulse drive mode of white light LEDs the white light LEDs average driving current
Formula；Then the dipulse drive mode is determined according to the first peak value wavelength model and the average driving current formula
Under the white light LEDs equivalent peak wavelength change amplitude minimal condition.Each parameter by controlling the white light LEDs meets institute
Equivalent peak wavelength change amplitude minimal condition is stated, that is, can control the color temperature change range of the white light LEDs minimum, to make institute
It states white light LED color temperature and keeps stable state, improve the stability of white light LED color temperature.
Detailed description of the invention
It in order to more clearly explain the embodiment of the invention or the technical proposal in the existing technology, below will be to institute in embodiment
Attached drawing to be used is needed to be briefly described, it should be apparent that, the accompanying drawings in the following description is only some implementations of the invention
Example, for those of ordinary skill in the art, without any creative labor, can also be according to these attached drawings
Obtain other attached drawings.
Fig. 1 is that CREE T5 is fixed on the pass in the case of different heat radiator thermal resistances between white light LEDs peak wavelength and electrical power
It is schematic diagram；
Fig. 2 is that the relationship that CREE T5 is fixed in the case of different heat radiator thermal resistances between white light LED color temperature and electrical power is shown
It is intended to；
Fig. 3 is a kind of method flow diagram of white light LED color temperature control method provided by the invention；
Fig. 4 is the connection schematic diagram of dipulse drive mode and DC driven mode between optically and electrically parameter；
Fig. 5 is the schematic diagram that white light LED color temperature under DC driven mode is controlled by adjusting radiator temperature；
Fig. 6 is the schematic diagram that white light LED color temperature under dipulse drive mode is controlled by adjusting radiator temperature；
Fig. 7 is to control the white light LED color temperature according to equivalent peak wavelength change amplitude minimal condition provided by the invention
Schematic diagram；
Fig. 8 is a kind of structural schematic diagram of white light LED color temperature control system provided by the invention.
Specific embodiment
Following will be combined with the drawings in the embodiments of the present invention, and technical solution in the embodiment of the present invention carries out clear, complete
Site preparation description, it is clear that described embodiments are only a part of the embodiments of the present invention, instead of all the embodiments.It is based on
Embodiment in the present invention, it is obtained by those of ordinary skill in the art without making creative efforts every other
Embodiment shall fall within the protection scope of the present invention.
White light LED color temperature is to be determined by its spatial distribution, and peak wavelength is as one important feature of spatial distribution
Parameter will directly affect spatial distribution.Below by taking the CREE T5 White-light LED chip of sharp (CREE) the company production of section, the U.S. as an example,
In the case where being fixed on different thermal resistance radiators and the different electrical power of load by testing research CREE T5, peak wavelength, color
Relationship between temperature and load electric power.Fig. 1 is that CREE T5 is fixed on white light LEDs peak value wave in the case of different heat radiator thermal resistances
Relation schematic diagram between long and electrical power.It can be seen from figure 1 that when load electric power increases to 2W from 0.5W, peak wavelength from
445nm is reduced to 442nm；When load electric power increases to 8W from 2W, peak wavelength is reduced to 450nm from 442nm.Fig. 2 is
CREE T5 is fixed on the relation schematic diagram in the case of different heat radiator thermal resistances between white light LED color temperature and electrical power.It can from Fig. 2
See, when load electric power increases to 2W from 0.5W, colour temperature is reduced to 6200K from 6700K；When load electric power increases to 8W from 2W
When, colour temperature increases to 7900K from 6200K.And as the heat radiator thermal resistance of white light LEDs increases, peak wavelength and colour temperature are all
Ascendant trend is presented.
Therefore complex chart 1 and Fig. 2 can be seen that peak wavelength variation tendency and colour temperature variation tendency it is almost the same,
There are inner link rules for the two, as long as therefore predicting peak wavelength variation range in the case of different loads radiator, energy
White light LED color temperature variation range in the case of acquisition different loads radiator, so that can also pass through control peak wavelength changes model
Minimum is enclosed, to obtain the situation of white light LED color temperature variation range minimum, white light LED color temperature is made to keep stablizing.
Based on this principle, the present invention proposes a kind of white light LED color temperature control method and system, by becoming to peak wavelength
White light LED color temperature control is realized in the control for changing range, and color temperature change range can be made minimum, improve the stabilization of white light LED color temperature
Property.
In order to make the foregoing objectives, features and advantages of the present invention clearer and more comprehensible, with reference to the accompanying drawing and specific real
Applying mode, the present invention is described in further detail.
Fig. 3 is a kind of method flow diagram of white light LED color temperature control method provided by the invention.Referring to Fig. 3, the present invention is mentioned
A kind of white light LED color temperature control method supplied, specifically includes:
Step 301: obtaining the first peak value wavelength model of white light LEDs under DC driven mode.
Fig. 4 is the connection schematic diagram of dipulse drive mode and DC driven mode between optically and electrically parameter.Ginseng
See Fig. 4, LED component only one function of current always under direct current and PWM drive mode, however under dipulse drive mode
Always there is dynamic second order electric current (Ilow、Ihigh) load on LED component, therefore LED component electric current, temperature, face under dipulse
There are problems that complicated multiple physical field intersects between color, how to construct the face of white light LED part under dipulse drive mode
Color model, and be current key scientific problems urgently to be resolved based on color model control white light LED part color temperature characteristic.This hair
The color model of bright building, i.e. peak wavelength model.By controlling the stability of peak wavelength, reach control white light LED color temperature
Keep stable target.
The first peak value wavelength model that the step 101 obtains white light LEDs under DC driven mode specifically includes:
Consider series resistance effect, according to diode Xiao Telai model, the I-E characteristic of the white light LEDs can table
It is shown as:
Wherein I is electric current, and β is constant relevant to doping concentration and junction area, TjFor junction temperature, e is unit charge, and V is
Voltage, RsFor series resistance, n is ideal factor, and k is Boltzmann constant；
Relationship between semiconductor PN load voltage and forbidden bandwidth energy is as follows:
Eg=Ve-IRse-eΔVel (2)
Wherein EgFor forbidden bandwidth energy, Δ VelFor physical constant；
The formula (1) is substituted into the formula (2), obtains forbidden bandwidth energy theorem:
Wherein V0For barrier voltage；
Based on semiconductor material photon transition energy balance principle, peak wavelength and the forbidden band for obtaining the white light LEDs are wide
Spend the relationship between energy:
Wherein λpFor peak wavelength, h is Planck's constant, and c is the light velocity, EgFor forbidden bandwidth energy, EDFor alms giver's latent electricity
Sub- energy, EAFor acceptor's bound electron energy, e is unit charge, and ε is dielectric constant, and R is acceptor-donor pair distance, ε0It is true
Empty dielectric constant；
The formula (3) are substituted into the formula (4), obtain the first peak value wavelength model:
The formula (5) is the peak wavelength model under DC driven mode, embodies the LED chip under DC drive mode
Peak wavelength λp, junction temperature TjAnd the connection relationship between load current I.The formula (5) is the Quantitative equation of peak wavelength,
Variable is temperature related parametric (junction temperature T in the formula (5)j) and electrical power relevant parameter (electric current I), remaining parameter is device
The physical characteristic parameter of part.According to the formula (5) derived, pass through temperature and electrical power, so that it may calculate the peak
It is worth wavelength Xp。
In order to which Mathematical treatment is convenient, the concept of equivalent peak wavelength is proposed, even:
The formula (11) is the first equivalent peak wavelength model of the white light LEDs, wherein λ 'pFor equivalent peak wave
It is long.According to the formula (11) it is found that the peak wavelength λ of LED chippVariation tendency and equivalent peak wavelength X 'pVariation become
Gesture is exactly the opposite.
The formula (11) are substituted into the formula (5), and to the junction temperature T in the formula (5)jDerivation is carried out, is obtained
Relationship between the equivalent peak wavelength and the junction temperature:
It can get equivalent peak wavelength and temperature sensitivity coefficient by formula described in this (12)Quantitative expression.
By the formula (12) it is found that the white light LEDs are under different electric currents and radiator loading condition, equivalent peak wavelength with
Temperature sensitivity coefficient is the function of variation, and the equivalent peak wavelength and temperature sensitivity coefficientWith load current
I, heat power consumption coefficient kh, LED heat hinder RjcAnd heat radiator thermal resistance RhsIt is directly related.
It can also be obtained by the formula (12) to draw a conclusion:
(a) when white light LEDs are installed on the lesser radiator of thermal resistance, i.e. R in formula (11)hsWhen smaller, the equivalent peak
It is worth wavelength and temperature sensitivity coefficientIt is larger, inversely prroportional relationship is shown as (such as according to equivalent peak wavelength and peak wavelength
Shown in the formula (11)), therefore LED peak wavelength and temperature sensitive coefficientIt is smaller, there is relatively stable temperature characterisitic,
I.e. with temperature change, peak wavelength amplitude of variation is smaller.It is possible thereby to obtain conclusion one:
Under same load current conditions, when white light LEDs are installed on the lesser radiator of thermal resistance, LED peak wavelength
With relatively stable temperature characterisitic, with temperature change, peak wavelength amplitude of variation is smaller.If it is larger that LED is installed on thermal resistance
Radiator, then peak wavelength amplitude of variation is larger with temperature change.
White light LED color temperature under dipulse drive mode being designed for illumination engineer according to the conclusion one, theory is provided
Foundation, such as: if it is intended to adjusting the variation of peak wavelength by temperature controlling instruments, it is biggish white light LEDs can be installed on thermal resistance
Radiator, the peak wavelength of LED and temperature sensitivity coefficient are larger at this time, therefore can be adjusted by small range of temperature, just
Large range of peak wavelength may be implemented and adjust control.
(b) when white light LEDs load current is smaller, i.e., the I in formula (11) is smaller, the equivalent peak wavelength and temperature
Sensitivity coefficientIt is larger, inversely prroportional relationship (such as described formula (11) is shown as according to equivalent peak wavelength and peak wavelength
It is shown), therefore LED peak wavelength and temperature sensitive coefficientIt is smaller, there is relatively stable temperature characterisitic, i.e., as temperature becomes
Change, peak wavelength amplitude of variation is smaller.It is possible thereby to obtain conclusion two:
When white light LEDs are installed on the radiator of fixed thermal resistance, in the smaller situation of white light LEDs load current, peak value
Wavelength has relatively stable temperature characterisitic, i.e., with temperature change, peak wavelength amplitude of variation is smaller.If LED load is electric
Flow it is larger, then peak wavelength amplitude of variation is larger with temperature change.
White light LED color temperature under dipulse drive mode is designed according to the conclusion two or illumination engineer, and reason is provided
By foundation, such as: if it is intended to adjusting the variation of peak wavelength by temperature controlling instruments, white light LEDs can be arranged in the big electricity of load
In the case where stream, the peak wavelength of LED and temperature sensitivity coefficient are larger at this time, therefore can pass through small range of temperature at this time
It adjusts, so that it may realize that large range of peak wavelength adjusts control.
Step 302: obtaining the average driving current formula of the white light LEDs under dipulse drive mode.
It can be seen that according to Fig. 1 and Fig. 2 in different electrical power and thermal resistance (junction temperature), the colour temperature of white light LEDs becomes
Change range is obvious, and as the heat radiator thermal resistance of white light LEDs increases, ascendant trend is all presented in peak wavelength and colour temperature.And double arteries and veins
Drive mode is rushed with 2 current impulse (Ilow、Ihigh) it is carried on LED, if not selecting reasonable (Ilow、Ihigh) range, it will
Apparent colour temperature is caused to fluctuate.Dipulse drive mode passes through switch control second order electric current Ilow、IhighAmplitude and duty ratio,
Change average current Iave, and then realize luminous flux phivAdjusting, have light modulation precision high, it is flexible the features such as.
The average driving current formula of the white light LEDs are as follows:
Iave=DIH+(1-D)IL (6)
Wherein IaveFor the average current under the dipulse drive mode, D is duty ratio；IH、ILIt is for second order electric current, i.e., double
2 pulse current amplitude values under pulsed driving mode.
Load current I in the formula (5) is the DC load current under DC driven mode, is equivalent to dipulse drive
Average current I under dynamic model formulaave, according to Fig. 4 it is also seen that equivalent relation between the two.It therefore can be by the formula (6)
Average driving current formula bring into the formula (5), obtain dipulse drive mode under the second peak wavelength model:
λ'p=e (nV0-ΔVel)+nkTj[ln(DIH+(1-D)IL)-ln(β)-2ln(Tj)] (16)
The formula (16) is the peak wavelength model under dipulse drive mode, is embodied under dipulse drive mode
The equivalent peak wavelength X of LED chip 'p, junction temperature Tj, duty ratio D and second order electric current IH、ILBetween connection relationship.The public affairs
Formula (16) is equivalent peak wavelength and second order electric current IH、ILBetween quantitative expression, junction temperature T can be passed throughj, duty ratio D, two
Rank electric current IH、ILAnd several physical constants can calculate equivalent peak wavelength, so as to change model by control peak wavelength
It encloses to adjust color temperature change range.
Step 303: the dipulse is determined according to the first peak value wavelength model and the average driving current formula
The equivalent peak wavelength change amplitude minimal condition of the white light LEDs under drive mode.
Obtain the junction temperature theoretical expression of the white light LEDs:
Tj=(Rjc+Rhs)*(IV)kh+Ta (7)
Wherein RjcFor device thermal resistance, RhsFor the heat radiator thermal resistance of the white light LEDs, khFor heat-dissipating power coefficient, TaFor
Environment temperature；
The formula (6) are substituted into the formula (7), obtain the knot of the white light LEDs under the dipulse drive mode
Warm expression formula:
Tj=(Rjc+Rhs)[(IH-IL)khVaveD+ILVavekh]+Ta (8)
Wherein VaveFor the average voltage under the dipulse drive mode；
The formula (8) is the quantitative expression of junction temperature of white LED under dipulse drive mode, can pass through device thermal resistance
Rjc, heat radiator thermal resistance Rhs, duty ratio D, second order electric current IH、ILAnd heat power consumption coefficient khJunction temperature can be calculated.It is only accurate
The size for predicting the junction temperature under different operating loading condition, can accurately just control peak wavelength, and then adjust colour temperature and become
Change range.
The junction temperature T of the white light LEDs under dipulse drive mode is obtained according to the formula (8)jBetween duty ratio D
Relationship:
The peak wavelength of the white light LEDs under dipulse drive mode is obtained according to the formula (5) and the formula (8)
λpWith junction temperature Tj, relationship between duty ratio D:
The formula (5), (9), (12) are substituted into the formula (10), can get the white light under dipulse drive mode
The equivalent peak wavelength X of LED 'pWith the relationship between duty ratio D:
dλ'p={ nkTj[ln(IH)-ln(IL)]+nk[ln(IL)-ln(β)-2ln(Tj)-2](Rjc+Rhs)(IH-IL)
khIaveVave}dD (13)
The formula (13) is the quantitative expression of equivalent peak wavelength and duty ratio sensitivity coefficient.Pass through the formula
(13) it is found that white light LEDs are under different electric currents and radiator loading condition, equivalent peak wavelength and duty ratio sensitivity coefficient
It is the function of variation.Would know which parameter has equivalent peak wavelength and duty ratio sensitivity coefficient by the function influences
Effect.For example, when white light LEDs are installed on the lesser radiator of thermal resistance, i.e. R in formula (13)hsWhen smaller, the equivalent peak
Wavelength and duty ratio sensitivity coefficientIt is smaller, inversely prroportional relationship is shown as (such as according to equivalent peak wavelength and peak wavelength
Shown in formula (11)), LED peak wavelength and duty ratio sensitivity coefficient under dipulse drive mode at this timeIt is larger, white light LEDs
With more unstable duty ratio characteristics, i.e., with change in duty cycle, peak wavelength amplitude of variation is larger.According to this knot
By, white light LED color temperature under dipulse drive mode can be designed for illumination engineer, and theoretical foundation is provided, such as: if it is intended to
The variation of peak wavelength is adjusted by adjusting duty ratio, white light LEDs can be installed on to the lesser radiator of thermal resistance, at this time LED
Peak wavelength and duty ratio sensitivity coefficient it is larger, therefore small range of duty cycle adjustment can be passed through, so that it may realize compared with
Large-scale peak wavelength adjusts control.
It can get White-light LED chip under various operating conditions, under dipulse drive mode according to the formula (13)
Equivalent peak wavelength X 'pThe smallest condition of amplitude of variation are as follows:
(dλ'p)min=nkTj[ln(IH)-ln(IL)]+nk[ln(IL)-ln(β)-2ln(Tj)-2](Rjc+Rhs)(IH-IL)
khIaveVave=0 (14)
The formula (14) be the formula (13) in the equivalent peak wavelength X 'pIt is 0 to the duty ratio derivation
In the case of minimal condition expression formula.Equivalent peak wavelength and duty ratio sensitivity coefficient (d λ 'p)minIt is 0, expression is accounted in difference
In the case of sky ratio, equivalent peak wavelength keeps stable state, and there is no any variations.I.e. white light LEDs load electric current and
When radiator parameter meets formula (14), peak wavelength holding stable state, i.e. equivalent peak wavelength X 'pAmplitude of variation is minimum,
Since peak wavelength is consistent with the variation tendency of colour temperature, colour temperature also keeps stable state at this time.
Therefore the equivalent peak of the white light LEDs under the dipulse drive mode can be determined according to the formula (14)
Wavelength change amplitude minimal condition are as follows:
The formula (15) is the mathematic(al) manipulation of the formula (14), when white light LED part under dipulse drive mode
When electricity, thermal characteristic meet the relationship in the formula (15), equivalent peak wavelength X 'pAmplitude of variation it is minimum.Work as institute
State equivalent peak wavelength X 'pWhen amplitude of variation minimum, real peak wavelength XpAmplitude of variation equally also for minimum.It is i.e. described
Average current Iave, the second order electric current IHAnd IL, the device thermal resistance Rjc, the heat radiator thermal resistance Rhs, the heat-dissipating power
Coefficient khAnd the average voltage VaveWhen meeting the equation (15), the equivalent peak wavelength, the peak wavelength and institute
It states colour temperature and keeps stability characteristic (quality) with the change of duty ratio.
Step 304: being kept according to the colour temperature that the equivalent peak wavelength change amplitude minimal condition controls the white light LEDs
Stable state.
The color of white light LEDs includes chromaticity coordinates, colour temperature, colour rendering index, and the color of white light LEDs is determined by its spatial distribution
Fixed, white LED spectrum is generally by two parts spectrum (sodium yellow that the blue color spectrum and YAG fluorescent powder of LED chip transmitting generate
Spectrum) it is constituted.Wherein the peak wavelength of White-light LED chip is decided by the size of the excitation spectrum of YAG fluorescent powder.As long as therefore controlling
The peak wavelength amplitude of variation of White-light LED chip processed is minimum, and the colour temperature of white LED light source can be made to be in stable shape simultaneously
State.
Therefore the step 304 specifically:
Control the average current I of the white light LEDsave, the second order electric current IHAnd IL, the device thermal resistance Rjc, institute
State heat radiator thermal resistance Rhs, the heat-dissipating power coefficient khAnd the average voltage VaveMeet the formula (15), makes described
The colour temperature of white light LEDs keeps stable state.
In addition, also can get by the formula (15) to draw a conclusion:
(c) similar with DC drive mode, under dipulse drive mode, when white light LEDs load current conditions are identical, if
White light LEDs are installed on the lesser radiator of thermal resistance, i.e. R in formula (15)hsWhen smaller, white light LED color temperature has more steady
Determine temperature characterisitic, with temperature change, color temperature change amplitude is smaller.If white light LEDs are installed on the biggish radiator of thermal resistance, that
With temperature change, color temperature change amplitude is larger.
(d) in order to make white light LEDs under dipulse drive mode, the stability of colour temperature is kept, needs to control second order electric current
IHAnd ILFor particular range, it is necessary to make (Iave-1)ln(IL) it is consistently less than Iaveln(IH)+ln(β)。
(e) as I under dipulse drive modeHAnd ILAnd average current IaveWhen for fixed value, the variation of peak wavelength is taken
Certainly in the heat radiator thermal resistance R of white light LED parths, device thermal resistance RjcAnd heat-dissipating power coefficient kh。
Fig. 5 is the schematic diagram that white light LED color temperature under DC driven mode is controlled by adjusting radiator temperature.Referring to Fig. 5,
When electric power load range is incremented to 8W from 2W, the color temperature change 2200K of white light LEDs under DC driven mode.When load electricity
It when power is 8W, needs to adjust 78 DEG C of radiator temperature, colour temperature could be controlled in target range.
Fig. 6 is the schematic diagram that white light LED color temperature under dipulse drive mode is controlled by adjusting radiator temperature.Referring to figure
6, when electric power load range is incremented to 8W from 2W, the color temperature change 1700K of white light LEDs under dipulse drive mode.When negative
It when load electrical power is 8W, needs to adjust 69 DEG C of radiator temperature, colour temperature could be controlled in target range.
Through Fig. 5 and Fig. 6 it is found that in identical electric power load, color temperature shift caused by dipulse drive mode
Amplitude Ratio DC driven mode is small, while in order to guarantee colour stability, adjusting radiator required for dipulse drive mode
Temperature range is also smaller than DC driven mode.
The first peak value wavelength model (see formula (5)) and double arteries and veins under the DC driven mode provided according to the present invention
The second peak wavelength model (see formula (16)) under drive mode is rushed it is found that by changing radiator temperature ThsIt adjusts indirectly
LED junction temperature Tj, can control equivalent peak wavelength and reach target value, so that realizing will be in color temperature adjustment to target zone.
Fig. 7 is to control the white light LED color temperature according to equivalent peak wavelength change amplitude minimal condition provided by the invention
Schematic diagram.Referring to Fig. 7, when the duty ratio of dipulse drive mode is steady state value D=0.5, device thermal resistance Rjc=6.4K/W dissipates
Hot device thermal resistance RhsWhen=10.3K/W, pass through the second order electric current I of white light LEDs under control dipulse drive modeHAnd ILDescribed in satisfaction
Formula (15), to control its peak wavelength λpAnd color temperature change amplitude is minimum.Control ILFor 0.33A, IHFor 1A, second order electricity
Flow IHAnd ILWhen interval is 0.67A, white light LED color temperature fluctuating range is minimum, and colour temperature is only 100K, as shown in Figure 7.If
Have no basis the reasonable second order electric current I of the formula (15) selectionHAnd IL, it will cause biggish colour temperature fluctuation range, for example sets
Fixed identical second order electric current IHAnd ILInterval be 0.67A, but ILIt is selected as 0.67A, IHFor 1.34A, white light LEDs at this time
Colour temperature fluctuating range is 600K, hence it is evident that 100K when greater than colour temperature fluctuating range minimum.
As it can be seen that the equivalent peak wavelength change amplitude minimal condition provided according to the present invention controls the institute of the white light LEDs
State average current Iave, the second order electric current IHAnd IL, the device thermal resistance Rjc, the heat radiator thermal resistance Rhs, the heat dissipation function
Rate coefficient khAnd the average voltage VaveMeet the formula (15), the color temperature change amplitude of the white light LEDs can be made most
It is small, to guarantee that white light LEDs are in stable state, improve the colour stability of white LED light source.
The present invention also provides a kind of white light LED color temperature control systems.Fig. 8 is a kind of white light LEDs color provided by the invention
The structural schematic diagram of temperature control system.Referring to Fig. 8, the white light LED color temperature control system includes:
First peak value wavelength model obtains module 801, for obtaining the first peak value wave of white light LEDs under DC driven mode
Long model；
Average driving current formula obtains module 802, for obtaining being averaged for white light LEDs under dipulse drive mode
Driving current formula；
Equivalent peak wavelength change amplitude minimal condition determining module 803, for according to the first peak value wavelength model
The equivalent peak wavelength change width of the white light LEDs under the dipulse drive mode is determined with the average driving current formula
Spend minimal condition；
Color temperature control module 804, for controlling the white light according to the equivalent peak wavelength change amplitude minimal condition
The colour temperature of LED keeps stable state.
Wherein, the first peak value wavelength model obtains module 801 and specifically includes:
Current-voltage characteristic acquiring unit, for obtaining the I-E characteristic of the white light LEDs:
Wherein I is electric current, and β is constant relevant to doping concentration and junction area, TjFor junction temperature, e is unit charge, and V is
Voltage, RsFor series resistance, n is ideal factor, and k is Boltzmann constant；
Load voltage and forbidden bandwidth energy relationship acquiring unit, it is wide for obtaining semiconductor PN load voltage and forbidden band
Spend the relationship between energy:
Eg=Ve-IRse-eΔVel (2)
Wherein EgFor forbidden bandwidth energy, Δ VelFor physical constant；
Forbidden bandwidth energy theorem unit obtains forbidden bandwidth energy for the formula (1) to be substituted into the formula (2)
Measure formula:
Wherein V0For barrier voltage；
Peak wavelength and forbidden bandwidth energy harvesting unit, the peak wavelength and forbidden band for obtaining the white light LEDs are wide
Spend the relationship between energy:
Wherein λpFor peak wavelength, h is Planck's constant, and c is the light velocity, EgFor forbidden bandwidth energy, EDFor alms giver's latent electricity
Sub- energy, EAFor acceptor's bound electron energy, e is unit charge, and ε is dielectric constant, and R is acceptor-donor pair distance, ε0It is true
Empty dielectric constant；
First peak value wavelength model acquiring unit obtains described for the formula (3) to be substituted into the formula (4)
One peak wavelength model:
The average driving current formula obtains module 802 and specifically includes:
Average driving current formula acquiring unit, for obtaining the average driving current formula:
Iave=DIH+(1-D)IL (6)
Wherein IaveFor the average current under the dipulse drive mode, D is duty ratio, IH、ILFor second order electric current.
The equivalent peak wavelength change amplitude minimal condition determining module 803 specifically includes:
Junction temperature theoretical expression acquiring unit, for obtaining the junction temperature theoretical expression of the white light LEDs:
Tj=(Rjc+Rhs)*(IV)kh+Ta (7)
Wherein RjcFor device thermal resistance, RhsFor the heat radiator thermal resistance of the white light LEDs, khFor heat-dissipating power coefficient, TaFor
Environment temperature；
Junction temperature expression formula acquiring unit obtains the dipulse and drives for the formula (6) to be substituted into the formula (7)
The junction temperature expression formula of the white light LEDs under dynamic model formula:
Tj=(Rjc+Rhs)[(IH-IL)khVaveD+ILVavekh]+Ta (8)
Wherein VaveFor the average voltage under the dipulse drive mode；
Junction temperature and duty cycle relationship acquiring unit, for obtaining the junction temperature and the duty ratio according to the formula (8)
Between relationship:
Peak wavelength and junction temperature and duty cycle relationship acquiring unit, for being obtained according to the formula (5) and the formula (8)
Obtain the relationship between the peak wavelength and the junction temperature and the duty ratio D:
First equivalent peak wavelength model acquiring unit, for obtaining the first of the white light LEDs according to the formula (5)
Equivalent peak wavelength model:
Wherein λ 'pFor equivalent peak wavelength；
Equivalent peak wavelength and junction temperature Relation acquisition unit are obtained for the formula (11) to be substituted into the formula (5)
Relationship between the equivalent peak wavelength and the junction temperature:
Equivalent peak wavelength and duty cycle relationship acquiring unit, for the formula (5), (9), (12) to be substituted into the public affairs
Formula (10) obtains the relationship between the equivalent peak wavelength and the duty ratio:
dλ'p={ nkTj[ln(IH)-ln(IL)]+nk[ln(IL)-ln(β)-2ln(Tj)-2](Rjc+Rhs)(IH-IL)
khIaveVave}dD (13)
Minimal condition expression formula acquiring unit, for obtaining the equivalent peak wavelength to described according to the formula (13)
Duty ratio derivation is the minimal condition expression formula in the case of 0:
(dλ'p)min=nkTj[ln(IH)-ln(IL)]+nk[ln(IL)-ln(β)-2ln(Tj)-2](Rjc+Rhs)(IH-IL)
khIaveVave=0 (14)
Equivalent peak wavelength change amplitude minimal condition determination unit, for determining double arteries and veins according to the formula (14)
Rush the equivalent peak wavelength change amplitude minimal condition of the white light LEDs under drive mode are as follows:
The color temperature control module 804 specifically includes:
Colour temperature control unit, for controlling the average current I of the white light LEDsave, the second order electric current IHAnd IL、
The device thermal resistance Rjc, the heat radiator thermal resistance Rhs, the heat-dissipating power coefficient khAnd the average voltage VaveMeet institute
Formula (15) are stated, the colour temperature of the white light LEDs is made to keep stable state.
Since the offset of White-light LED chip peak wavelength is related to many physical agents, especially in dipulse drive mode
Lower second order electric current loads on device simultaneously, and average current and junction temperature depend on the factors such as duty ratio, second order electric current, frequency.No
With duty, when frequency will generate the second order electric current of different in width, will directly influence system junction temperature dynamic response characteristic, in turn
Cause system colors dynamic change, therefore the variation of White-light LED chip peak wavelength has complicated multiple physical field cross rule
Rule.The present invention discloses White-light LED chip peak wavelength under dipulse drive mode, second order electric current and junction temperature from different level
Dynamic cross rule, by more physical models to the color temperature characteristic of White-light LED illumination system under dipulse drive mode
It is controlled, there is important theory significance.
Each embodiment in this specification is described in a progressive manner, the highlights of each of the examples are with other
The difference of embodiment, the same or similar parts in each embodiment may refer to each other.For system disclosed in embodiment
For, since it is corresponded to the methods disclosed in the examples, so being described relatively simple, related place is said referring to method part
It is bright.
Used herein a specific example illustrates the principle and implementation of the invention, and above embodiments are said
It is bright to be merely used to help understand method and its core concept of the invention；At the same time, for those skilled in the art, foundation
Thought of the invention, there will be changes in the specific implementation manner and application range.In conclusion the content of the present specification is not
It is interpreted as limitation of the present invention.
Claims (2)
1. a kind of white light LED color temperature control method, which is characterized in that the described method includes:
The first peak value wavelength model of white light LEDs under DC driven mode is determined according to diode Xiao Telai model；The basis
Diode Xiao Telai model determines the first peak value wavelength model of white light LEDs under DC driven mode, specifically includes:
The I-E characteristic of the white light LEDs is determined according to the diode Xiao Telai model:
Wherein I is electric current, and β is constant relevant to doping concentration and junction area, TjFor junction temperature, e is unit charge, and V is voltage,
RsFor series resistance, n is ideal factor, and k is Boltzmann constant；
Obtain the relationship between semiconductor PN load voltage and forbidden bandwidth energy:
Eg=Ve-IRse-eΔVel (2)
Wherein EgFor forbidden bandwidth energy, Δ VelFor physical constant；
The formula (1) is substituted into the formula (2), obtains forbidden bandwidth energy theorem:
Wherein V0For barrier voltage；
The peak wavelength and forbidden bandwidth energy of the white light LEDs are determined according to semiconductor material photon transition energy balance principle
Between relationship:
Wherein λpFor peak wavelength, h is Planck's constant, and c is the light velocity, EgFor forbidden bandwidth energy, EDFor alms giver's bound electron energy
Amount, EAFor acceptor's bound electron energy, e is unit charge, and ε is dielectric constant, and R is acceptor-donor pair distance, ε0For vacuum Jie
Electric constant；
The formula (3) are substituted into the formula (4), obtain the first peak value wavelength model:
Obtain the average driving current formula of the white light LEDs under dipulse drive mode；The acquisition dipulse drive mode
Under the white light LEDs average driving current formula, specifically include:
Obtain the average driving current formula:
Iave=DIH+(1-D)IL (6)
Wherein IaveFor the average current under the dipulse drive mode, D is duty ratio, IH、ILFor second order electric current；
Institute under the dipulse drive mode is determined according to the first peak value wavelength model and the average driving current formula
State the equivalent peak wavelength change amplitude minimal condition of white light LEDs；It is described according to the first peak value wavelength model and described flat
Equal driving current formula determines the equivalent peak wavelength change amplitude minimum item of the white light LEDs under the dipulse drive mode
Part specifically includes:
Obtain the junction temperature theoretical expression of the white light LEDs:
Tj=(Rjc+Rhs)*(IV)kh+Ta (7)
Wherein RjcFor device thermal resistance, RhsFor the heat radiator thermal resistance of the white light LEDs, khFor heat-dissipating power coefficient, TaFor environment
Temperature；
The formula (6) are substituted into the formula (7), obtain the junction temperature table of the white light LEDs under the dipulse drive mode
Up to formula:
Tj=(Rjc+Rhs)[(IH-IL)khVaveD+ILVavekh]+Ta (8)
Wherein VaveFor the average voltage under the dipulse drive mode；
The relationship between the junction temperature and the duty ratio is obtained according to the formula (8):
It is obtained between the peak wavelength, the junction temperature and the duty ratio D according to the formula (5) and the formula (8)
Relationship:
The first equivalent peak wavelength model of the white light LEDs is obtained according to the formula (5):
Wherein λ 'pFor equivalent peak wavelength；
The formula (11) are substituted into the formula (5), obtain the relationship between the equivalent peak wavelength and the junction temperature:
The formula (5), (9), (12) are substituted into the formula (10), obtain the equivalent peak wavelength and the duty ratio it
Between relationship:
dλ'p={ nkTj[ln(IH)-ln(IL)]+nk[ln(IL)-ln(β)-2ln(Tj)-2](Rjc+Rhs)(IH-IL)khIaveVave}
dD (13)
According to the formula (13) obtain the equivalent peak wavelength to the duty ratio derivation be 0 in the case of minimal condition table
Up to formula:
(dλ'p)min=nkTj[ln(IH)-ln(IL)]+nk[ln(IL)-ln(β)-2ln(Tj)-2](Rjc+Rhs)(IH-IL)
khIaveVave=0 (14)
The equivalent peak wavelength change amplitude of the white light LEDs under the dipulse drive mode is determined according to the formula (14)
Minimal condition are as follows:
Stable state is kept according to the colour temperature that the equivalent peak wavelength change amplitude minimal condition controls the white light LEDs；Institute
It states and stable state is kept according to the colour temperature that the equivalent peak wavelength change amplitude minimal condition controls the white light LEDs, specifically
Include:
Control the average current I of the white light LEDsave, the second order electric current IHAnd IL, the device thermal resistance Rjc, it is described dissipate
Hot device thermal resistance Rhs, the heat-dissipating power coefficient khAnd the average voltage VaveMeet the formula (15), so that described white
The colour temperature of light LED keeps stable state.
2. a kind of white light LED color temperature control system, which is characterized in that the system comprises:
First peak value wavelength model obtains module, for determining white light under DC driven mode according to diode Xiao Telai model
The first peak value wavelength model of LED；The first peak value wavelength model obtains module and specifically includes:
Current-voltage characteristic acquiring unit, for determining electric current-electricity of the white light LEDs according to the diode Xiao Telai model
Press characteristic:
Wherein I is electric current, and β is constant relevant to doping concentration and junction area, TjFor junction temperature, e is unit charge, and V is voltage,
RsFor series resistance, n is ideal factor, and k is Boltzmann constant；
Load voltage and forbidden bandwidth energy relationship acquiring unit, for obtaining semiconductor PN load voltage and forbidden bandwidth energy
Relationship between amount:
Eg=Ve-IRse-eΔVel (2)
Wherein EgFor forbidden bandwidth energy, Δ VelFor physical constant；
It is public to obtain forbidden bandwidth energy for the formula (1) to be substituted into the formula (2) for forbidden bandwidth energy theorem unit
Formula:
Wherein V0For barrier voltage；
Peak wavelength and forbidden bandwidth energy harvesting unit, for being determined according to semiconductor material photon transition energy balance principle
Relationship between the peak wavelength and forbidden bandwidth energy of the white light LEDs:
Wherein λpFor peak wavelength, h is Planck's constant, and c is the light velocity, EgFor forbidden bandwidth energy, EDFor alms giver's bound electron energy
Amount, EAFor acceptor's bound electron energy, e is unit charge, and ε is dielectric constant, and R is acceptor-donor pair distance, ε0For vacuum Jie
Electric constant；
First peak value wavelength model acquiring unit obtains the first peak for the formula (3) to be substituted into the formula (4)
It is worth wavelength model:
Average driving current formula obtains module, for obtaining the average driving electricity of the white light LEDs under dipulse drive mode
Flow formula；The average driving current formula obtains module and specifically includes:
Average driving current formula acquiring unit, for obtaining the average driving current formula:
Iave=DIH+(1-D)IL (6)
Wherein IaveFor the average current under the dipulse drive mode, D is duty ratio, IH、ILFor second order electric current；
Equivalent peak wavelength change amplitude minimal condition determining module, for according to the first peak value wavelength model and described flat
Equal driving current formula determines the equivalent peak wavelength change amplitude minimum item of the white light LEDs under the dipulse drive mode
Part；The equivalent peak wavelength change amplitude minimal condition determining module specifically includes:
Junction temperature theoretical expression acquiring unit, for obtaining the junction temperature theoretical expression of the white light LEDs:
Tj=(Rjc+Rhs)*(IV)kh+Ta (7)
Wherein RjcFor device thermal resistance, RhsFor the heat radiator thermal resistance of the white light LEDs, khFor heat-dissipating power coefficient, TaFor environment
Temperature；
Junction temperature expression formula acquiring unit obtains the dipulse driving mould for the formula (6) to be substituted into the formula (7)
The junction temperature expression formula of the white light LEDs under formula:
Tj=(Rjc+Rhs)[(IH-IL)khVaveD+ILVavekh]+Ta (8)
Wherein VaveFor the average voltage under the dipulse drive mode；
Junction temperature and duty cycle relationship acquiring unit, for being obtained between the junction temperature and the duty ratio according to the formula (8)
Relationship:
Peak wavelength and junction temperature and duty cycle relationship acquiring unit, for obtaining institute according to the formula (5) and the formula (8)
State the relationship between peak wavelength, the junction temperature and the duty ratio D:
First equivalent peak wavelength model acquiring unit, be used to obtain the white light LEDs according to the formula (5) first are equivalent
Peak wavelength model:
Wherein λ 'pFor equivalent peak wavelength；
Equivalent peak wavelength and junction temperature Relation acquisition unit, for the formula (11) to be substituted into the formula (5), described in acquisition
Relationship between equivalent peak wavelength and the junction temperature:
Equivalent peak wavelength and duty cycle relationship acquiring unit, for the formula (5), (9), (12) to be substituted into the formula
(10), the relationship between the equivalent peak wavelength and the duty ratio is obtained:
dλ'p={ nkTj[ln(IH)-ln(IL)]+nk[ln(IL)-ln(β)-2ln(Tj)-2](Rjc+Rhs)(IH-IL)khIaveVave}
dD (13)
Minimal condition expression formula acquiring unit, for obtaining the equivalent peak wavelength to the duty according to the formula (13)
Minimal condition expression formula in the case of being 0 than derivation:
(dλ'p)min=nkTj[ln(IH)-ln(IL)]+nk[ln(IL)-ln(β)-2ln(Tj)-2](Rjc+Rhs)(IH-IL)
khIaveVave=0 (14)
Equivalent peak wavelength change amplitude minimal condition determination unit, for determining that the dipulse is driven according to the formula (14)
The equivalent peak wavelength change amplitude minimal condition of the white light LEDs under dynamic model formula are as follows:
Color temperature control module, for controlling the color of the white light LEDs according to the equivalent peak wavelength change amplitude minimal condition
Temperature keeps stable state；The color temperature control module specifically includes:
Colour temperature control unit, for controlling the average current I of the white light LEDsave, the second order electric current IHAnd IL, it is described
Device thermal resistance Rjc, the heat radiator thermal resistance Rhs, the heat-dissipating power coefficient khAnd the average voltage VaveMeet the public affairs
Formula (15), so that the colour temperature of the white light LEDs keeps stable state.
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