CN105222014A - A kind of heat spreader structures determination method for parameter for high-power LED street lamp - Google Patents

Abstract

A kind of high-power LED street lamp, is characterized in that it comprises lamp housing, support, diffuser, reflector, power supply, LED lamp bead array, aluminum base PCB plate, driver and Aluminium Radiator composition; Its heat spreader structures determination method for parameter comprises: modeling, simplify, set up thermal resistance network figure, calculate heat spreader structures parameter; Its superiority is: 1. perfect heat-dissipating, easy for installation, maintenance cost is low, solves a heat radiation difficult problem for high-power LED street lamp; 2. the design method of heat radiator based on Equivalent heat path method makes the impact of parameters on radiating effect more clear, conveniently carries out program calculation, and the optimization being more conducive to radiator parameter calculates.

Description

A kind of heat spreader structures determination method for parameter for high-power LED street lamp

(1) technical field:

The present invention designs field of LED illumination, particularly relates to the heat spreader structures dimensional parameters defining method in high-power LED street lamp luminaire design process, especially a kind of heat spreader structures determination method for parameter for high-power LED street lamp.

(2) background technology:

Semiconductor lighting (LED, LightEmittingDiode) be LED application product give priority to field, according to the prediction of internal authority mechanism, 21 century is novel illumination light source epoch of representative by entering with LED illumination.According to Department of Science and Technology's planning, within 2011, enter ten thousand, the ten city plan of second stage, namely build 2,000,000 LED street lamp in 50 cities.LED street lamp is compared with conventional high-tension sodium vapor lamp, and the long-life is one of its most significant advantage, and will ensure that high-power LED street lamp can give full play to this advantage, and heat radiation is the primary key issue needing to solve.

Light-the photoelectric transformation efficiency of the LED chip extensively adopted at present only has 15% ~ 20%, the electric energy conversion of the overwhelming majority is in order to radiationless heat energy, if this partial heat energy can not shed timely, will be that the junction temperature of LED chip sharply raises, thus reduce the light extraction efficiency of LED chip, cause LED street lamp light decay, affect the service life of LED street lamp.

Existing LED street lamp radiator design adopts comparatively economical and practical gilled radiator, usually the method for Experience Design is adopted in fin structure size design process, radiating effect is poor, and design process wastes time and energy, easily cause the wasting of resources, some high-power LED street lamp have employed the novel radiating mode enhance heat effect such as heat-pipe radiator, but be only often for the design of road lamp of a certain concrete model go out heat radiator dedicated, there is the problem that versatility is poor.The present invention is intended to propose a kind of new radiator for high-power LED street lamp, its structure adopts the mode that traditional fin combines with flat-plate type micro heat pipe array, for the high-power LED street lamp of a certain appointment model, conveniently junction temperature of chip can be doped, by adjusting the key parameter of radiator according to its input power---the quantity N of spacing of fin S, fin height H, fin thickness t and flat-plate type micro heat pipe array _h, junction temperature of chip is controlled at T _j≤ 70 DEG C, and consider Machinability Evaluation and cost factor, determine the structural parameters of radiator, instruct fansink designs.

(3) summary of the invention:

The object of the invention is to design a kind of heat spreader structures determination method for parameter for high-power LED street lamp, it can overcome the deficiencies in the prior art, for designed novel large-power LED street lamp heat radiator, set up the physical model of crucial thermal component, thermal resistance network figure is drawn out based on Equivalent heat path method in the basis of model being carried out to Rational Simplification, proposes a kind of quantity N determining spacing of fin S, fin height H, fin thickness t and flat-plate type micro heat pipe array _hdeng the algorithm of radiator key parameter, for the purpose of control chip junction temperature, parameter can be adjusted flexibly according to the power of the street lamp of reality and appearance forrns, instruct the design of Structural Parameters of new radiator, there is important production practices meaning.

Technical scheme of the present invention: a kind of high-power LED street lamp, is characterized in that it comprises lamp housing, support, diffuser, reflector, power supply, LED lamp bead array, aluminum base PCB (PrintedCircuitBoard---printed circuit board) plate, driver and Aluminium Radiator composition; Wherein, described LED lamp bead array is arranged on lamp stand, and is encapsulated on the copper foil layer of aluminum base PCB plate; Described pcb board is fixed on the base plate of Aluminium Radiator by two screws, and described LED lamp bead is welded on pcb board; The thermal-conduction resistance between heat conductive silica gel reduction plate is filled in gap between described pcb board and Aluminium Radiator base plate; Described driver is arranged on Aluminium Radiator according to driver cover plate.

Described Aluminium Radiator is gilled radiator, and its fin is the Special-shaped fin improved; The different in nature fin of described improvement increases and slotted different in nature fin; The fluting of described different in nature fin is embedded with the flat-plate type micro heat pipe can strengthening radiator heat transfer ability.

For a heat spreader structures determination method for parameter for high-power LED street lamp, it is characterized in that it comprises the following steps:

1. set up the physical model of the crucial radiating component of high-power LED street lamp, extract and road lamp cooling relation the most several component: LED street lamp, aluminum base PCB plate, flat-plate type micro heat pipe array, fin radiator;

2. due to step 1. in physical model be three-dimensional structure body, therefore will to its carry out analysis simplify, suppose:

(1) input electric power of single LED lamp pearl is constant;

(2) each structure uniform in material, thermal conductivity factor λ is constant;

(3) free convection environment is the dry air of normal atmosphere pressure, and temperature T _aconstant;

(4) NATURAL CONVECTION COEFFICIENT OF HEAT α only with fin temperature T _frelevant;

(5) because the thickness t of fin heat radiation is much smaller than fin height H, so ignore the heat convection impact of flight tip and side;

(6) ignore the impact of heat loss through radiation, only consider heat convection effect;

3. the foundation of equivalent thermal resistance network:

Through step modeling 1. and step simplification 2., the three-dimensional heat dissipation problem of high-power LED street lamp has been reduced to one-dimensional steady-state heat transfer problem, further, heat-transfer path is converted into Equivalent heat path form, forms the thermal resistance network of the series and parallel relation between convenient analysis each point of thermal resistance;

4. founding mathematical models and calculating heat spreader structures parameter:

According to step 3. in thermal resistance network, in conjunction with the series and parallel form of each several part thermal resistance, the entire thermal resistance of chip-environment can be defined as:

$R_{J-A}=\frac{R_{LED}}{N_{LED}}+R_{Cu}+R_D+R_{Al}+R_B+R_F=\frac{T_J-T_M}{Q_T}+\frac{T_M-T_B}{Q_T}+\frac{T_B-T_F}{Q_T}+\frac{T_F-T_A}{Q_T}---\left(1\right)$

In formula (1):

R _lED--LED lamp bead packaging thermal resistance, can obtain by looking into reference books;

N _lED--the quantity of LED lamp bead;

R _cu--copper clad layers thermal resistance on MCPCB plate;

R _d--MCPCB plate upper dielectric layer thermal resistance;

R _al--aluminum base layer thermal resistance on MCPCB plate;

R _f--the thermal resistance of new radiator finless parts;

Wherein, R _lEDand N _lEDfor known parameters, the copper clad layers thermal resistance R on MCPCB plate _cu, dielectric layer thermal resistance R _d, aluminum base layer thermal resistance R _alwith radiator aluminum substrate heat resistance R _bcalculate comparatively simple, all can be equivalent to one dimension flat late heat transfer problem, known parameters can be substituted in following formula and calculate:

$R_X=\frac{{\mathrm{\δ}}_X}{{\mathrm{\λ}}_X{A}_X}=\frac{{\mathrm{\δ}}_X}{{\mathrm{\λ}}_X(f\·L_X\·H_X)}---\left(2\right)$

In formula, X represents copper clad layers C respectively _u, dielectric layer D, aluminum base layer A _lwith radiator aluminum base plate B:

δ _x--each structure material coefficient of heat conduction;

A _x--each structure is perpendicular to the heat-conducting area of direction of heat flow;

F--area coefficient, wherein copper clad layers area coefficient f=0.8, all the other are f=1;

According to thermal resistance expression formula and thermal resistance network figure, heat radiator fin thermal resistance R can be obtained _fbe made up of two parts: traditional square-section fin heat resistance R _f' and the thermal resistance R of flat-plate type micro heat pipe array _h, wherein, R _hcan provide in the description of product of micro heat pipe array, and R _f' can be calculated by following formula:

${R_F}^{\′}=\frac{1}{{\mathrm{\αA\η}}_F}=\frac{1}{{\mathrm{\α\η}}_F\left(2N_F{H}_{B}W\right)}---\left(3\right)$

In formula:

Vertical heat flow direction on A--fin and not uncared-for area of dissipation summation;

η _f--fin fin efficiency, can be calculated by following formula;

${\mathrm{\η}}_F=\frac{\tanh \left(mW\right)}{mW}=\frac{\tanh \left(\sqrt{2\mathrm{\α}/\left({\mathrm{\λ}}_{H}t\right)}W\right)}{\sqrt{2\mathrm{\α}/\left({\mathrm{\λ}}_{H}t\right)}W}---\left(4\right)$

Heat spreader structures due to LED street lamp belongs to square-section on perpendicular and participates in the situation of heat transfer free convection, therefore, according to through the revised Elenbaas equation of VandePol Fan Debo and measured data, the numerical value of convection transfer rate α can be obtained, select this empirical equation to ask for convection transfer rate α:

$\mathrm{\α}=\frac{{\mathrm{\λ}}_{Air}}{r}Nu=\frac{{\mathrm{\λ}}_{Air}}{r}\·\frac{Ra}{\mathrm{\ψ}}\[1-e^{-\mathrm{\ψ}{(0.50/Ra)}^{3/4}}\]---\left(5\right)$

In formula:

$\mathrm{\ψ}=\frac{24(1-0.483e^{-0.17/a^{*}})}{{\{(1+a^{*}/2)\[1+(1-e^{-0.83a^{*}})(9.14\sqrt{a^{*}}{e}^{-0.4646S}-0.61)\]\}}^3},Ra=\frac{g\mathrm{\β}(T_F-T_A)}{\mathrm{\ν}a}\frac{r}{H_B}$

$r=\frac{2WS}{2W+S},a^{*}=\frac{S}{W}$

From thermal resistance network figure, between two parts thermal resistance, belong to parallel relationship, therefore, the entire thermal resistance R of radiator _fmeet:

$\frac{1}{R_F}=\frac{1}{{R_F}^{\′}}+\frac{N_H}{R_H}---\left(6\right)$

Thus known, $R_F=\frac{{R_F}^{\′}\·R_H}{{R_F}^{\′}\·N_H+R_H}.$

In formula (5), by known structural physical parameter, comprise lower fin radiator base width L _b, substructure height H _b, base thickness δ _b, spacing of fin S, fin height H, fin thickness t, number of fins N _f, flat-plate type micro heat pipe array quantity and gravity acceleration g, in substitution formula, and according to air physical property table, can obtain the coefficient of expansion β related in air physical property, thermal diffusion coefficient a and the thermal conductivity factor λ that are correlated with _air, the quantity N of new radiator key parameter spacing of fin S, fin height H, fin thickness t and flat-plate type micro heat pipe array can be determined _h.

Described step 4. in the thermal resistance R of heat radiator fin part _fbe the form being thought of as common aluminum square-section fin and flat-plate type micro heat pipe array in parallel, ignore the thermal resistance that the inner phase-change heat-exchange carried out of flat-plate type micro heat pipe array produces.

Superiority of the present invention is:

1. compared with traditional aluminum fin radiator, the new radiator initiatively combined with passive radiating mode is adopted to have outstanding heat dispersion, easy for installation, maintenance cost is low, under the prerequisite ensureing reliability and cost, well solves a heat radiation difficult problem for high-power LED street lamp;

2. compare with Software Numerical Simulation method with traditional Empirical Design, design method of heat radiator based on Equivalent heat path method proposed by the invention makes the impact of parameters on radiating effect more clear, conveniently carry out program calculation, the optimization being more conducive to radiator parameter calculates.

(4) accompanying drawing illustrates:

The structural representation of Fig. 1 a kind of high-power LED street lamp involved by the present invention;

Fig. 2 a kind of high-power LED street lamp middle plateform micro heat pipe array involved by the present invention is embedded in the schematic diagram in fin radiator;

The simplification physical model of radiator critical component in Fig. 3 a kind of high-power LED street lamp involved by the present invention, comprises LED lamp bead, aluminum base PCB plate, flat-plate type micro heat pipe array and fin radiator;

Fig. 4 involved by the present invention a kind of in the heat spreader structures determination method for parameter of high-power LED street lamp high-power LED street lamp along the thermal resistance network structural representation on direction of heat flow;

Fig. 5 is a kind of for the junction temperature of chip calculation process schematic diagram based on Equivalent heat path method in the heat spreader structures determination method for parameter of high-power LED street lamp involved by the present invention.

Wherein, 1 is lamp housing; 2 is reflector; 3 is LED lamp bead array; 4 is Aluminium Radiator; 5 is Aluminium Radiator base plate; 6 is flat-plate type micro heat pipe array; 7 is driver; 8 is lamp stand; 9 is driver cover plate; 10 is aluminum base PCB plate.

(5) detailed description of the invention:

Embodiment: a kind of high-power LED street lamp (see Fig. 1), is characterized in that it comprises lamp housing 1, support, diffuser, reflector 2, power supply, LED lamp bead array 3, aluminum base PCB plate 10 and aluminum fin formula radiator 4 and forms; Wherein, described LED lamp bead array 3 is arranged on lamp stand 8, and is encapsulated on the copper foil layer of aluminum base PCB plate 10; Described pcb board is fixed on the base plate of Aluminium Radiator 4 by two screws, and described LED lamp bead array 3 is welded on aluminum base PCB plate 10; The thermal-conduction resistance between heat conductive silica gel reduction plate is filled in gap between described aluminum base PCB plate 10 and Aluminium Radiator base plate 5; Described driver 7 is arranged on Aluminium Radiator 4 according to driver cover plate 9.

Described Aluminium Radiator 4 is gilled radiator, and its fin is the Special-shaped fin (see Fig. 2) improved; The different in nature fin of described improvement increases and slotted different in nature fin; The fluting of described different in nature fin is embedded with the flat-plate type micro heat pipe array 6 can strengthening radiator heat transfer ability.

A kind of heat spreader structures determination method for parameter (see Fig. 4, Fig. 5) for high-power LED street lamp, is characterized in that it comprises the following steps:

2. set up the physical model of the crucial radiating component of high-power LED street lamp, extract and road lamp cooling relation the most several component: LED lamp bead array 3, aluminum base PCB plate 10, flat-plate type micro heat pipe array 6, Aluminium Radiator 4, as shown in Figure 3;

2. due to step 1. in physical model be three-dimensional structure body, therefore will to its carry out analysis simplify, suppose:

(1) input electric power of single LED lamp pearl is constant;

(2) each structure uniform in material, thermal conductivity factor λ is constant;

(3) free convection environment is the dry air of normal atmosphere pressure, and temperature T _aconstant;

(4) NATURAL CONVECTION COEFFICIENT OF HEAT α only with fin temperature T _frelevant;

(5) because the thickness t of fin heat radiation is much smaller than fin height H, so ignore the heat convection impact of flight tip and side;

(6) ignore the impact of heat loss through radiation, only consider heat convection effect;

3. the foundation (see Fig. 4) of equivalent thermal resistance network:

Through step modeling 1. and step simplification 2., the three-dimensional heat dissipation problem of high-power LED street lamp has been reduced to one-dimensional steady-state heat transfer problem, further, heat-transfer path is converted into Equivalent heat path form, forms the thermal resistance network of the series and parallel relation between convenient analysis each point of thermal resistance;

4. founding mathematical models and calculating heat spreader structures parameter:

According to step 3. in thermal resistance network, in conjunction with the series and parallel form of each several part thermal resistance, the entire thermal resistance of chip-environment can be defined as:

$R_{J-A}=\frac{R_{LED}}{N_{LED}}+R_{Cu}+R_D+R_{Al}+R_B+R_F=\frac{T_J-T_M}{Q_T}+\frac{T_M-T_B}{Q_T}+\frac{T_B-T_F}{Q_T}+\frac{T_F-T_A}{Q_T}---\left(1\right)$

In formula (1):

R _lED--LED lamp bead packaging thermal resistance, can obtain by looking into reference books;

N _lED--the quantity of LED lamp bead;

R _cu--copper clad layers thermal resistance on MCPCB plate;

R _d--MCPCB plate upper dielectric layer thermal resistance;

R _al--aluminum base layer thermal resistance on MCPCB plate;

R _f--the thermal resistance of new radiator finless parts;

Wherein, R _lEDand N _lEDfor known parameters, the copper clad layers thermal resistance R on MCPCB plate _cu, dielectric layer thermal resistance R _d, aluminum base layer thermal resistance R _alwith radiator aluminum substrate heat resistance R _bcalculate comparatively simple, all can be equivalent to one dimension flat late heat transfer problem, known parameters can be substituted in following formula and calculate:

$R_X=\frac{{\mathrm{\δ}}_X}{{\mathrm{\λ}}_X{A}_X}=\frac{{\mathrm{\δ}}_X}{{\mathrm{\λ}}_X(f\·L_X\·H_X)}---\left(2\right)$

In formula, X represents copper clad layers C respectively _u, dielectric layer D, aluminum base layer A _lwith radiator aluminum base plate B:

δ _x--each structure material coefficient of heat conduction;

A _x--each structure is perpendicular to the heat-conducting area of direction of heat flow;

F--area coefficient, wherein copper clad layers area coefficient f=0.8, all the other are f=1;

According to thermal resistance expression formula and thermal resistance network figure, heat radiator fin thermal resistance R can be obtained _fbe made up of two parts: traditional square-section fin heat resistance R _f' and the thermal resistance R of flat-plate type micro heat pipe array _h, wherein, R _hcan provide in the description of product of micro heat pipe array, and R _f' can be calculated by following formula:

${R_F}^{\′}=\frac{1}{{\mathrm{\αA\η}}_F}=\frac{1}{{\mathrm{\α\η}}_F\left(2N_F{H}_{B}W\right)}---\left(3\right)$

In formula:

Vertical heat flow direction on A--fin and not uncared-for area of dissipation summation;

η _f--fin fin efficiency, can be calculated by following formula;

${\mathrm{\η}}_F=\frac{\tanh \left(mW\right)}{mW}=\frac{\tanh \left(\sqrt{2\mathrm{\α}/\left({\mathrm{\λ}}_{H}t\right)}W\right)}{\sqrt{2\mathrm{\α}/\left({\mathrm{\λ}}_{H}t\right)}W}---\left(4\right)$

Heat spreader structures due to LED street lamp belongs to square-section on perpendicular and participates in the situation of heat transfer free convection, therefore, according to through the revised Elenbaas equation of VandePol Fan Debo and measured data, the numerical value of convection transfer rate α can be obtained, select this empirical equation to ask for convection transfer rate α:

$\mathrm{\α}=\frac{{\mathrm{\λ}}_{Air}}{r}Nu=\frac{{\mathrm{\λ}}_{Air}}{r}\·\frac{Ra}{\mathrm{\ψ}}\[1-e^{-\mathrm{\ψ}{(0.50/Ra)}^{3/4}}\]---\left(5\right)$

In formula:

$\mathrm{\ψ}=\frac{24(1-0.483e^{-0.17/a^{*}})}{{\{(1+a^{*}/2)\[1+(1-e^{-0.83a^{*}})(9.14\sqrt{a^{*}}{e}^{-0.4646S}-0.61)\]\}}^3},Ra=\frac{g\mathrm{\β}(T_F-T_A)}{\mathrm{\ν}a}\frac{r}{H_B}$

$r=\frac{2WS}{2W+S},a^{*}=\frac{S}{W}$

From thermal resistance network figure, between two parts thermal resistance, belong to parallel relationship, therefore, the entire thermal resistance R of radiator _fmeet:

$\frac{1}{R_F}=\frac{1}{{R_F}^{\′}}+\frac{N_H}{R_H}---\left(6\right)$

Thus known, $R_F=\frac{{R_F}^{\′}\·R_H}{{R_F}^{\′}\·N_H+R_H}.$

In formula (5), by known structural physical parameter, comprise lower fin radiator base width L _b, substructure height H _b, base thickness δ _b, spacing of fin S, fin height H, fin thickness t, number of fins N _f, flat-plate type micro heat pipe array quantity and gravity acceleration g, in substitution formula, and according to air physical property table, can obtain the coefficient of expansion β related in air physical property, thermal diffusion coefficient a and the thermal conductivity factor λ that are correlated with _air, the quantity N of new radiator key parameter spacing of fin S, fin height H, fin thickness t and flat-plate type micro heat pipe array can be determined _h.

Described step 4. in the thermal resistance R of heat radiator fin part _fbe the form being thought of as common aluminum square-section fin and flat-plate type micro heat pipe array in parallel, ignore the thermal resistance that the inner phase-change heat-exchange carried out of flat-plate type micro heat pipe array produces.

In order to the scheme making the art personnel better understand this invention, below in conjunction with drawings and embodiments, the present invention is set forth in more detail.

Rule of thumb and the result of numerical simulation, region heat flow density between every two groups of lamp pearl array elements is larger, therefore the rectangular fin in this region is set to Special-shaped fin---namely fin is suitably thickeied and increase and slot so that embedded installation flat-plate type micro heat pipe, according to the result of numerical simulation, suggestion arranges 7 groups and amounts to 35 flat-plate type micro heat pipes on the street lamp Aluminium Radiator of 150W power level, need not completely equidistantly arrange in reality, according to the installing space of actual heat flux distribution adjustment flat-plate type micro heat pipe, the schematic diagram of installation site can be given in fig 2.

New radiator design is carried out for certain 180W high-power LED street lamp finished product, set up physical model, conveniently analytical calculation, ignore non-key factor, only extract and modeling is carried out on larger critical component LED lamp bead array, aluminum base PCB plate (MCPCB) and the aluminum fin formula radiator of heat radiation impact, as shown in Figure 3, inspection information handbook, obtains LED lamp bead packaging thermal resistance R _lED, the parameters such as each layer thickness of MCPCB plate and material thermal conductivity.

The input electric power of single LED lamp pearl is constant is 1.5W, and calculate by electricity conversion 15%, the heat radiation constant total quantity of 120 LED lamp pearls is Q _t=102W, and the encapsulation internal thermal resistance of LED lamp bead is constant, looks into reference books known, this model LED lamp bead packaging thermal resistance of 1.5W is R _lED=11K/W, drive current I _f=480mA. aluminum base circuit board total length is L _m=420mm, width is W _m=23mm, gross thickness is t _m=1.2mm, copper clad layers thickness is t _cu=0.2mm, copper clad layers thermal conductivity factor λ _cu=387.5W/ (mK), medium thickness t _i=0.075mm, dielectric layer thermal conductivity factor is λ _i=0.7W/ (mK), aluminium base thickness t _al=0.8mm, aluminum base layer thermal conductivity factor λ _al=237.5W/ (mK). in order to ensure the mounting arrangements of LED lamp bead array, consider Machinability Evaluation, the base dimensions of new radiator is fixed as long L _b=500mm, wide H _b=360mm, thick δ _b=10mm. chooses spacing of fin s, fin height H, the quantity N of fin thickness t and flat-plate type micro heat pipe array _hfor design variable, given initial value: spacing of fin s=8mm, fin height H=36mm in iterative computation, fin thickness t=2mm, flat-plate type micro heat pipe array quantity N _h=35.

Adopt Equivalent heat path method to analyze model, draw the thermal resistance network figure of cooling system, analyze the series and parallel relation between each point of thermal resistance.Carry out iterative computation according to the calculation flow chart provided coding in MATLAB above, during calculating, first should measure the temperature T of fin radiator some points on the surface under high-power LED street lamp is in stable state _f, for the purpose of reliable, several groups of data can be measured more and average, also should measure the ambient parameter T around street lamp heat radiator under steady-working state simultaneously _a, substitute into foot of radiator parameter L _b=500mm, wide H _b=360mm, thick δ _b=10mm, consults manual data and obtains the air physical parameter ρ needed for calculating, ν, a, λ _air, before beginning iterative computation, the street lamp of different capacity and structure needs the initial configuration size s rule of thumb providing corresponding radiator, t, H, N _h, in detailed description of the invention at the beginning, we illustrate the initial parameter for certain high-power LED street lamp product, as a reference, substitute into the air physical parameter and working environment state parameter that check in, first draw the convection transfer rate α of fin radiator, and then try to achieve the fin efficiency η of fin _f, then can draw square-section finless parts thermal resistance R by formula (5) _f', look into the thermal resistance R getting flat-plate type micro heat pipe array _h, and then heat sink part entire thermal resistance R can be pushed away to obtain by formula (6) _f; Fin radiator base thermal resistance R can be obtained on this basis _bwith base temperature T _b; Next product manual is consulted, obtain the thermodynamic parameter of each layer of aluminum base PCB, specific embodiments give at the beginning certain product adopt the design parameter of aluminum base PCB, but the parameter of the aluminum base PCB that different manufacturers product is selected is not quite identical, concrete analysis is needed in Practical Calculation, on the basis of above-mentioned parameter, substitute into the thermal resistance R that formula (2) can calculate aluminum base PCB _mwith copper clad layers temperature T on it _m; Then the packaging thermal resistance that product manual obtains LED lamp bead is consulted, single different power is often different with the LED lamp bead packaging thermal resistance of packaging technology, when for specific product design radiator, can check and selected LED lamp bead product manual obtains, finally extrapolate the LED chip junction temperature under street lamp steady-working state, by the result of iterative computation gained compared with the junction temperature that product manual specifies, if do not met, iterative computation is restarted, until meet junction temperature of chip requirement after then revising the parameter of new radiator.

If met the demands, then carry out next step to calculate, it is carry out further optimal design to the size of radiator meeting on cooling requirements basis that this part calculates, in order to design more reasonably new radiator on the basis meeting junction temperature of chip requirement, by the method for control variables, investigate spacing of fin S, fin height H, the quantity N of fin thickness t and flat-plate type micro heat pipe array _heach single argument is on the impact of junction temperature, optimum size parameter distribution when junction temperature of must sening as an envoy to meets design requirement, consider that the cost of new radiator, consumptive material and workability suitably adjust parameter more simultaneously, thus provide guidance for the application of new radiator on 180W high-power LED street lamp.

Shown in the following Fig. 4 of calculation flow chart of the present invention, should consider the consumptive material of Novel fin radiator in computational process, the impact of the many factors such as cost and Machinability Evaluation, radiator parameter determining step will elaborate in a specific embodiment.

In sum, computational methods proposed by the invention can determine that the new radiator of band flat-plate type micro heat pipe array is applied in the critical size parameter in concrete LED street lamp very easily, for the application of new radiator provides Technical Reference, there is very large engineering practical value.

Claims (4)

1. a high-power LED street lamp, is characterized in that it comprises lamp housing, support, diffuser, reflector, power supply, LED lamp bead array, aluminum base PCB plate, driver and Aluminium Radiator composition; Wherein, described LED lamp bead array is arranged on lamp stand, and is encapsulated on the copper foil layer of aluminum base PCB plate; Described pcb board is fixed on the base plate of Aluminium Radiator by two screws, and described LED lamp bead is welded on pcb board; The thermal-conduction resistance between heat conductive silica gel reduction plate is filled in gap between described pcb board and Aluminium Radiator base plate; Described driver is arranged on Aluminium Radiator according to driver cover plate.

2. a kind of high-power LED street lamp according to claim 1, is characterized in that described Aluminium Radiator is gilled radiator, and its fin is the Special-shaped fin improved; The different in nature fin of described improvement increases and slotted different in nature fin; The fluting of described different in nature fin is embedded with the flat-plate type micro heat pipe can strengthening radiator heat transfer ability.

3., for a heat spreader structures determination method for parameter for high-power LED street lamp, it is characterized in that it comprises the following steps:

1. set up the physical model of the crucial radiating component of high-power LED street lamp, extract and road lamp cooling relation the most several component: LED street lamp, aluminum base PCB plate, flat-plate type micro heat pipe array, fin radiator;

2. due to step 1. in physical model be three-dimensional structure body, therefore will to its carry out analysis simplify, suppose:

(1) input electric power of single LED lamp pearl is constant;

(2) each structure uniform in material, thermal conductivity factor λ is constant;

(3) free convection environment is the dry air of normal atmosphere pressure, and temperature T _aconstant;

(4) NATURAL CONVECTION COEFFICIENT OF HEAT α only with fin temperature T _frelevant;

(5) because the thickness t of fin heat radiation is much smaller than fin height H, so ignore the heat convection impact of flight tip and side;

(6) ignore the impact of heat loss through radiation, only consider heat convection effect;

3. the foundation of equivalent thermal resistance network:

Through step modeling 1. and step simplification 2., the three-dimensional heat dissipation problem of high-power LED street lamp has been reduced to one-dimensional steady-state heat transfer problem, further, heat-transfer path is converted into Equivalent heat path form, forms the thermal resistance network of the series and parallel relation between convenient analysis each point of thermal resistance;

4. founding mathematical models and calculating heat spreader structures parameter:

According to step 3. in thermal resistance network, in conjunction with the series and parallel form of each several part thermal resistance, the entire thermal resistance of chip-environment can be defined as:

$R_{J-A}=\frac{R_{LED}}{N_{LED}}+R_{Cu}+R_D+R_{Al}+R_B+R_F=\frac{T_J-T_M}{Q_T}+\frac{T_M-T_B}{Q_T}+\frac{T_B-T_F}{Q_T}+\frac{T_F-T_A}{Q_T}---\left(1\right)$

In formula (1):

R _lED--LED lamp bead packaging thermal resistance, can obtain by looking into reference books;

N _lED--the quantity of LED lamp bead;

R _cu--copper clad layers thermal resistance on MCPCB plate;

R _d--MCPCB plate upper dielectric layer thermal resistance;

R _al--aluminum base layer thermal resistance on MCPCB plate;

R _f--the thermal resistance of new radiator finless parts;

Wherein, R _lEDand N _lEDfor known parameters, the copper clad layers thermal resistance R on MCPCB plate _cu, dielectric layer thermal resistance R _d, aluminum base layer thermal resistance R _alwith radiator aluminum substrate heat resistance R _bcalculate comparatively simple, all can be equivalent to one dimension flat late heat transfer problem, known parameters can be substituted in following formula and calculate:

$R_X=\frac{{\mathrm{\δ}}_X}{{\mathrm{\λ}}_X{A}_X}=\frac{{\mathrm{\δ}}_X}{{\mathrm{\λ}}_X(f\·L_X\·H_X)}---\left(2\right)$

In formula, X represents copper clad layers C respectively _u, dielectric layer D, aluminum base layer A _lwith radiator aluminum base plate B:

δ _x--each structure material coefficient of heat conduction;

A _x--each structure is perpendicular to the heat-conducting area of direction of heat flow;

F--area coefficient, wherein copper clad layers area coefficient f=0.8, all the other are f=1;

According to thermal resistance expression formula and thermal resistance network figure, heat radiator fin thermal resistance R can be obtained _fbe made up of two parts: traditional square-section fin heat resistance R _f' and the thermal resistance R of flat-plate type micro heat pipe array _h, wherein, R _hcan provide in the description of product of micro heat pipe array, and R _f' can be calculated by following formula:

${R_F}^{\′}=\frac{1}{{\mathrm{\αA\η}}_F}=\frac{1}{{\mathrm{\α\η}}_F\left(2N_F{H}_{B}W\right)}---\left(3\right)$

In formula:

Vertical heat flow direction on A--fin and not uncared-for area of dissipation summation;

η _f--fin fin efficiency, can be calculated by following formula;

${\mathrm{\η}}_F=\frac{\tanh \left(mW\right)}{mW}=\frac{\tanh \left(\sqrt{2\mathrm{\α}/\left({\mathrm{\λ}}_{H}t\right)}W\right)}{\sqrt{2\mathrm{\α}/\left({\mathrm{\λ}}_{H}t\right)}W}---\left(4\right)$

Heat spreader structures due to LED street lamp belongs to square-section on perpendicular and participates in the situation of heat transfer free convection, therefore, according to through the revised Elenbaas equation of VandePol Fan Debo and measured data, the numerical value of convection transfer rate α can be obtained, select this empirical equation to ask for convection transfer rate α:

$\mathrm{\α}=\frac{{\mathrm{\λ}}_{Air}}{r}Nu=\frac{{\mathrm{\λ}}_{Air}}{r}.\frac{Ra}{\mathrm{\ψ}}\[1-e^{-\mathrm{\ψ}{(0.50/Ra)}^{3/4}}\]---\left(5\right)$

In formula:

$\mathrm{\ψ}=\frac{24(1-0.483e^{-0.17/a^{*}})}{{\{(1+a^{*}/2)\[1+(1-e^{-0.83a^{*}})(9.14\sqrt{a^{*}}{e}^{-0.4646S}-0.61)\]\}}^3},Ra=\frac{g\mathrm{\β}(T_F-T_A)}{va}\frac{r}{H_B}$

$r=\frac{2WS}{2W+S},a^{*}=\frac{S}{W}$

From thermal resistance network figure, between two parts thermal resistance, belong to parallel relationship, therefore, the entire thermal resistance R of radiator _fmeet:

$\frac{1}{R_F}=\frac{1}{{R_F}^{\′}}+\frac{N_H}{R_H}---\left(6\right)$

Thus known, $R_F=\frac{{R_F}^{\′}\·R_H}{{R_F}^{\′}\·N_H+R_H}.$

In formula (5), by known structural physical parameter, comprise lower fin radiator base width L _b, substructure height H _b, base thickness δ _b, spacing of fin S, fin height H, fin thickness t, number of fins N _f, flat-plate type micro heat pipe array quantity and gravity acceleration g, in substitution formula, and according to air physical property table, can obtain the coefficient of expansion β related in air physical property, thermal diffusion coefficient a and the thermal conductivity factor λ that are correlated with _air, the quantity N of new radiator key parameter spacing of fin S, fin height H, fin thickness t and flat-plate type micro heat pipe array can be determined _h.

4. a kind of heat spreader structures determination method for parameter for high-power LED street lamp according to claim 3, is characterized in that the thermal resistance R of the heat radiator fin part during described step 4. _fbe the form being thought of as common aluminum square-section fin and flat-plate type micro heat pipe array in parallel, ignore the thermal resistance that the inner phase-change heat-exchange carried out of flat-plate type micro heat pipe array produces.