CN106714368B - A kind of New LED drive control method - Google Patents
A kind of New LED drive control method Download PDFInfo
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- CN106714368B CN106714368B CN201611042817.0A CN201611042817A CN106714368B CN 106714368 B CN106714368 B CN 106714368B CN 201611042817 A CN201611042817 A CN 201611042817A CN 106714368 B CN106714368 B CN 106714368B
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- luminous flux
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/10—Controlling the intensity of the light
Abstract
The present invention relates to a kind of New LED drive control methods, by the output voltage signal for sampling LED drive circuitu, and be sent in current controller；Current controller obtains one and setting reference light flux by specific algorithmΦ refCorresponding reference current signali ref, the current reference signali refWith the output current of LED driveri dIt is compared to obtain error signalε, and obtain control signal by compensation network.Under the control of the control signal, driver provides one to LED load and generates reference current with current controlleri refEqually big forward current signal, to make LED load generate luminous flux holding and reference light fluxΦ refUnanimously, that is, the control of luminous flux is realized.Relatively accurately controlling for LED output light fluxs may be implemented in the present invention.
Description
Technical field
The present invention relates to LED drive control strategies field, especially a kind of New LED drive control method.
Background technology
LED electric light sources application scenario is more next extensively, small to display, instruction field, arrives road lighting, medical treatment, aviation etc. greatly
High leading-edge field.These only need LED that can generate light output with some, play simple indicative function, some but needs
It wants that LED output lights can be accurately controlled.No matter which kind of is using the drive control that all can't do without LED.
LED drive control strategies common at present are current constant control and power limitation control.The size of the output light flux of LED
It is not only related with the size of forward current but also closely related with the height of junction temperature of chip.By modeling analysis it is found that the change of junction temperature
The size of input electric power can not only be influenced by changing, while can also influence the conversion ratio size that electric energy is converted to luminous energy.Current constant control
When, when the forward voltage of the larger rising of junction temperature of chip, LED will decline, input power declines, and apparent light will occur in LED chip
Decline phenomenon, that is, output light flux is decreased obviously；When power limitation control, when the larger rising of junction temperature of chip, the forward voltage of LED
Decline, power limitation control by accordingly improve the size of input current make up because junction temperature increase caused by voltage decline, but by
Rise with the decline of forward voltage in fever coefficient, still can lead to the decline of luminous flux, therefore power limitation control is not yet
It can effectively improve because temperature raising leads to the sharp-decay of LED light flux.
In bigger or relatively high to the output light quality requirement occasion of variations injunction temperature, LED output light fluxs are realized
It accurately controlling, current constant control and power limitation control are difficult to meet such requirement, so, the mesh based on optimization LED light characteristic
, it is very necessary to study novel LED drive control strategies.
Invention content
In view of this, the purpose of the present invention is to propose to a kind of New LED drive control methods, at the same consider forward current and
Influence of the temperature variable to LED output light fluxs improves traditional current constant control and power limitation control mode often because of larger temperature
Degree rises the case where caused luminous flux drastically declines.And by forward voltage argument table temperature displaying function information, it is convenient for the control
Specific implementation of the strategy in LED drive circuit.
The present invention is realized using following scheme：A kind of New LED drive control method, specifically includes following steps：
Step S1：According to LED chip, LED light electric model is established, and is obtained using luminous flux phi and forward voltage U as variable
Forward current IdAlgorithm model Id=f-1(φ, U)；
Step S2：In current controller, the reference value Φ of required LED light flux is setref, sample LED driving transducers
Output voltage U, and based on the forward current I obtained by step S1dAlgorithm model, obtain corresponding current reference signal iref；
Step S3：The current reference signal i that current controller is generatedrefWith the output current sampled signal of LED driver
idIt is compared to obtain error signal, and a control signal is obtained by corresponding compensation network, controlled using the control signal
It is i that LED driver, which generates a size,refElectric current output.
Further, step S1 specifically includes following steps：
Step S11：If LED forward direction input currents are less than 1A, based on LED forward directions C-V characteristic and pass through Taylor series expansion
LED power P can be obtained in analysisdWith forward current IdBetween approximately linear, relational expression is as follows：
Pd=aId+b (1)
Wherein, a, b are constant, the actual measurement P that value size passes through specific LED chipdWith IdData obtain；
Step S12：If the forward current I of LEDdConstant, forward voltage U can be with junction temperature TjIncrease and approximately linear subtracts
It is few, LED heat is hindered into RjRegard constant, forward voltage U and heatsink temperature T ashsCan be approximately linear relationship, relational expression is as follows：
Ths=cU+d (2)
Wherein, c, d are constant, the actual measurement T that value size passes through specific LED chiphsIt is obtained with U data；
Step S13：Definition LED heating powers are Ph, with input electric power PdBetween relationship can be expressed with following formula：
Ph=KhPd (3)
Wherein, KhFor the coefficient that generates heat, i.e. electric conversion efficiency, to determine LED for generate heat and the size of luminous power；
Step S14：As fixed positive input current IdWhen, COEFFICIENT K of generating heathOn linear with the rising of heatsink temperature
It rises；As fixing cooling fins temperature ThsWhen, COEFFICIENT K of generating heathIt will be with the rising of positive input current also linear rise.Therefore, it is based on
Relational expression (2), can be able to forward voltage U and forward current IdFor the fever COEFFICIENT K of variablehModular form：
Kh(U,Id)=(k1U+k2)(k3Id+k4)/γ (4)
Wherein, coefficient k1、k2、k3、k4, γ provided by LED chip producer or experimental results obtain；
Step S15：According to formula (1), (2), (3), (4), the photoelectricity model of LED chip junction temperature is obtained：
Step S16：If positive input current IdIt is constant, the light efficiency E and junction temperature T of LEDjBetween there are linear approximate relationships, can
It is expressed as following formula：
E=E0[1+ke(Tj-T0)] (6)
Wherein, keFor light efficiency variation with temperature rate, keLess than zero；T0For 25 DEG C of junction temperature, E0For 25 DEG C of corresponding volumes of junction temperature
Determine light efficiency, the value size and input rated current IdIt is related；
Step S17：It is obtained with electric current and electricity in conjunction with (1), (5), (6) formula according to the relationship of the Φ of luminous flux and light efficiency E
Pressure is the photoelectricity model of the N LED chip luminous fluxes of variable, such as following formula：
Step S18：The parameter of specific LED chip is substituted into, obtains specific LED photovoltaic model expression, and further
Reverse goes out using luminous flux phi and forward voltage U as the forward current I of variabledAlgorithm model, such as following formula：
Id=f-1(φ,U) (8)。
Further, the control signal is duty cycle signals.
Further, one and luminous flux phi can be obtained according to (8)ref, the corresponding current reference letters of LED forward voltages U
Number iref, by current reference signal irefWith the output current sampled signal i of LED driverdIt is compared to obtain error signal, and
A duty cycle control signal is obtained by corresponding compensation network, controls the break-make of driver switch, and then LED load is made to send out
Luminous flux be setting Φref。
Compared with prior art, the present invention has following advantageous effect：The present invention considers forward current and temperature variable simultaneously
Influence to LED output light fluxs improves under traditional current constant control and power limitation control mode, often because of larger temperature rise
The case where caused luminous flux drastically declines.And by forward voltage argument table temperature displaying function information, exist convenient for the control strategy
Specific implementation in LED drive circuit.
Description of the drawings
Fig. 1 is the principle schematic of the embodiment of the present invention.
Fig. 2 is application of the embodiment of the present invention in LED chip, and specially CREE XPG R4 chips are in different positive electricity
Pressure, forward current with light flux variations schematic diagram.
Fig. 3 is CREE XPG R4 chips in the embodiment of the present invention respectively in permanent luminous flux control and constant current, power limitation control
Under, curve graph that forward current changes with forward voltage.
Fig. 4 is CREE XPG R4 chips in the embodiment of the present invention respectively in permanent luminous flux control and constant current, power limitation control
Under strategy, curve graph that luminous flux changes with forward voltage.
Fig. 5 is a specific embodiment of the present invention on Flyback driving circuits.
Specific implementation mode
The present invention will be further described with reference to the accompanying drawings and embodiments.
As shown in Figure 1, present embodiments providing a kind of New LED drive control method, mainly there are driver, current control
Device and compensation network etc..Specifically include following steps：
Step S1：According to LED chip, LED light electric model is established, and is obtained using luminous flux phi and forward voltage U as variable
Forward current IdAlgorithm model Id=f-1(φ, U)；
Step S2：In current controller, the reference value Φ of required LED light flux is setref, sample LED driving transducers
Output voltage U, and based on the forward current I obtained by step S1dAlgorithm model, obtain corresponding current reference signal iref；
Step S3：The current reference signal i that current controller is generatedrefWith the output current sampled signal of LED driver
idIt is compared to obtain error signal, and a control signal is obtained by corresponding compensation network, controlled using the control signal
It is i that LED driver, which generates a size,refElectric current output.
In the present embodiment, with Cree companies XPG R4 chip assemblies when heatsink temperature is 50 DEG C, acquired reality
Data instance is tested, the determination process of the design parameter of LED light electric model is discussed in detail：
It, and can by Taylor series expansion analysis based on LED forward directions C-V characteristic when LED forward direction input currents are less than 1A
Obtain LED power PdWith forward current IdBetween approximately linear, relational expression such as (1)：
Pd=aId+b (1)
According to the P of the Cree XPG R4 chips of actual measurementdWith IdData, can linear fit obtain a=3.2409, b=-
0.09964。
As the forward current I of LEDdWhen constant, forward voltage U can be with junction temperature TjIncrease and approximately linear reduce.This core
Piece RjFor 15 DEG C/W, forward voltage U and heatsink temperature ThsCan be approximately linear relationship (2)：
Ths=cU+d (2)
According to the Cree XPG R4 chips of actual measurement under different heatsink temperatures ThsWith U data, linear fit obtains c=-
394.74, d=1186.3.
Definition LED heating powers are Ph, with input electric power PdBetween relationship can use formula (3) express.
Ph=KhPd
(3)
K in formulahFor the coefficient, i.e. electric conversion efficiency of generating heat；It will determine LED for generating heat and the size of luminous power.
As fixed positive input current IdWhen, COEFFICIENT K of generating heathBy the linear rise with the rising of heatsink temperature；Work as fixation
Heatsink temperature ThsWhen, COEFFICIENT K of generating heathIt will be with the rising of positive input current also linear rise.Therefore, it is based on relational expression (2),
It can be able to forward voltage U and positive input current IdFor the fever COEFFICIENT K of variablehModular form (4)：
Kh(U,Id)=(k1U+k2)(k3Id+k4)/γ (4)
The coefficient k of Cree XPG R4 chips can be obtained by specific experiment data1=-2.4353, k2=7.56, k3=
0.173、k4=0.6064, γ=0.663.
According to formula (1), (2), (3), (4), the photoelectricity model (5) of LED chip junction temperature can be further arrived：
Positive input current IdIt is constant, the light efficiency E and junction temperature T of LEDjBetween there are linear approximate relationships, be represented by formula
(6)：
E=E0[1+ke(Tj-T0)] (6)
The k of CreeXPG R4 chips is obtained by the result of Experiments of OpticsE=-0.012；T0It is corresponding for 25 DEG C of junction temperature
Specified light efficiency E0For 69.282lm/W.
According to the relationship of the Φ of luminous flux and light efficiency E, in conjunction with (1), (5), (6) formula, can be obtained with electric current and voltage is to become
The photoelectricity model of the LED light flux of amount, such as formula (7)：
The design parameter of the built photoelectricity model of Cree XPG R4 chips is shown in Table 1.
1 XPG R4 chip model parameters of table
| k1(/V) | k2 | k3(/A) | k4 | a(V) | b(W) | c(℃/V) |
| -2.4353 | 7.56 | 0.173 | 0.6064 | 3.2409 | -0.09964 | -394.74 |
| d(℃) | E0(lm/W) | T0(℃) | Rj(℃/W) | ke | γ | N |
| 1186.3 | 69.282 | 60.149 | 15 | -0.012 | 0.663 | 9 |
The change curve of luminous flux and forward current under different voltages can be obtained in step more than repeating, such as Fig. 2 institutes
Show.Each forward voltage U and luminous flux phi correspond to a forward current I in Fig. 2d, this is the current algorithm of current controller
Foundation.
In the present embodiment, the main present invention that introduces puies forward a kind of New LED drive control method in LED perseverance luminous flux controls
In application.Using CREE XPG R4 chips as research object, when 10 DEG C of heatsink temperature, forward current 0.314A, positive electricity
Pressure is 2.978V, input power 0.93W, output light flux 106.23lm.It is analyzed by simulation software, obtains chip difference
Under permanent luminous flux control, current constant control, power limitation control strategy, the curve graph that chip forward current changes with forward voltage,
As shown in Figure 3；The curve graph that chip luminous flux changes with forward voltage, as shown in Figure 4.By Fig. 3, Fig. 4 it is found that temperature leads to light
Being affected for amount, will overcome its influence, really to realize the invariable control of luminous flux, it is necessary to substantially change positive electricity
The size of stream.The constant purpose of output light flux can not achieve using current constant control and power limitation control strategy.Only persevering light is logical
Amount control could realize luminous flux constant control truly.
The present embodiment puies forward a kind of novel drive control method, the one embodiment applied in specific LED drive circuit,
As shown in Figure 5.The main circuit of LED driver is Flyback converters.The reference of luminous flux needed for being set in current controller
Value ΦrefAnd with the output voltage sampled value of Flyback converters, corresponding current reference signal is obtained by current algorithm
iref；The current reference signal i of the generation of current controllerrefWith the output current sampled signal i of Flyback convertersdThrough accidentally
Poor amplifier relatively obtains an error signal, which passes through the control circuit for being sent to transformer primary side of optocoupler, passes through
One PWM adjustment units generate pwm signal, control switching tube break-make, so that Flyback converters is generated size and reach irefElectric current carries
LED load is supplied, even if the luminous flux that LED is generated is Φref。
The foregoing is merely the preferred embodiment of the present invention, which is suitable for all driving transformation for being suitble to LED
Circuit.All equivalent changes and modifications done according to scope of the present invention patent should all belong to the covering scope of the present invention.
Claims (3)
1. a kind of New LED drive control method, it is characterised in that：Include the following steps：
Step S1：According to LED chip, establish LED light electric model, and obtain using luminous flux phi and forward voltage U as variable just
To electric current IdAlgorithm model Id=f-1(φ, U)；
Step S2：In current controller, the reference value Φ of required LED light flux is setref, sample the defeated of LED driving transducers
Go out voltage U, and based on the forward current I obtained by step S1dAlgorithm model, obtain corresponding current reference signal iref；
Step S3：The current reference signal i that current controller is generatedrefWith the output current sampled signal i of LED driverdInto
Row relatively obtains error signal, and obtains a control signal by corresponding compensation network, is driven using control signal control LED
It is i that dynamic device, which generates a size,refElectric current output；
Step S1 specifically includes following steps：
Step S11：If LED forward direction input currents are less than 1A, analyzed based on LED forward directions C-V characteristic and by Taylor series expansion
LED power P can be obtaineddWith forward current IdBetween approximately linear, relational expression is as follows：
Pd=aId+b (1)
Wherein, a, b are constant, the actual measurement P that value size passes through specific LED chipdWith IdData obtain；
Step S12：If the forward current I of LEDdConstant, forward voltage U can be with junction temperature TjIncrease and approximately linear reduce, will
LED heat hinders RjRegard constant, forward voltage U and heatsink temperature T ashsCan be approximately linear relationship, relational expression is as follows：
Ths=cU+d (2)
Wherein, c, d are constant, the actual measurement T that value size passes through specific LED chiphsIt is obtained with U data；
Step S13：Definition LED heating powers are Ph, with input electric power PdBetween relationship can be expressed with following formula：
Ph=KhPd (3)
Wherein, KhFor the coefficient that generates heat, i.e. electric conversion efficiency, to determine LED for generate heat and the size of luminous power；
Step S14：It calculates with forward voltage U and forward current IdFor the fever COEFFICIENT K of variablehModular form：
Kh(U,Id)=(k1U+k2)(k3Id+k4)/γ (4)
Wherein, coefficient k1、k2、k3、k4, γ provided by LED chip producer or experimental results obtain；
Step S15：According to formula (1), (2), (3), (4), the photoelectricity model of LED chip junction temperature is obtained：
Step S16：If positive input current IdIt is constant, the light efficiency E and junction temperature T of LEDjBetween there are linear approximate relationships, can indicate
For following formula：
E=E0[1+ke(Tj-T0)] (6)
Wherein, keFor light efficiency variation with temperature rate, keLess than zero；T0For 25 DEG C of junction temperature, E0For 25 DEG C of corresponding normal lights of junction temperature
Effect, the value size and input rated current IdIt is related；
Step S17：According to the relationship of the Φ of luminous flux and light efficiency E, in conjunction with (1), (5), (6) formula, obtain be with electric current and voltage
The photoelectricity model of the N LED chip luminous fluxes of variable, such as following formula：
Step S18：The parameter of specific LED chip is substituted into, specific LED photovoltaic model expression, and further reverse are obtained
Go out using luminous flux phi and forward voltage U as the forward current I of variabledAlgorithm model, such as following formula：
Id=f-1(φ,U) (8)。
2. a kind of New LED drive control method according to claim 1, it is characterised in that：The control signal is to account for
Sky compares signal.
3. a kind of New LED drive control method according to claim 1 or 2, it is characterised in that：The light of each setting
Flux phirefWith all corresponding one positive reference current i of LED forward voltages Uref, control is so that the actual forward that LED load obtains
Electric current idThe reference current i generated for LED driverref, and then the Φ that the luminous flux for making LED load send out is settingref。
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| CN107590326B (en) * | 2017-08-31 | 2020-06-09 | 江苏大学 | Simulation model and simulation method of LED module |
| CN112702814B (en) * | 2020-12-21 | 2023-03-31 | 中国人民解放军战略支援部队信息工程大学 | Bias current optimization method and system based on LED electric heating model |
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| CN202258255U (en) * | 2011-10-11 | 2012-05-30 | 深圳Tcl新技术有限公司 | Light-emitting diode (LED) driving device, LED light source module and liquid crystal display |
| CN104717781A (en) * | 2013-12-11 | 2015-06-17 | 台达电子企业管理（上海）有限公司 | Light adjusting device and method |
| CN104853486A (en) * | 2015-04-27 | 2015-08-19 | 欧普照明股份有限公司 | PWM-based light adjusting circuit |
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| CN202258255U (en) * | 2011-10-11 | 2012-05-30 | 深圳Tcl新技术有限公司 | Light-emitting diode (LED) driving device, LED light source module and liquid crystal display |
| CN104717781A (en) * | 2013-12-11 | 2015-06-17 | 台达电子企业管理（上海）有限公司 | Light adjusting device and method |
| CN104853486A (en) * | 2015-04-27 | 2015-08-19 | 欧普照明股份有限公司 | PWM-based light adjusting circuit |
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