CN103868613A - LabVIEW-based LED junction temperature measurement method - Google Patents
LabVIEW-based LED junction temperature measurement method Download PDFInfo
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- CN103868613A CN103868613A CN201210538233.8A CN201210538233A CN103868613A CN 103868613 A CN103868613 A CN 103868613A CN 201210538233 A CN201210538233 A CN 201210538233A CN 103868613 A CN103868613 A CN 103868613A
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Abstract
The invention discloses a LabVIEW-based LED junction temperature measurement method. The invention can provide theoretical data support for scientific and reasonable LED structure design and effective LED heat dissipation problem solution. According to the method of the invention, a forward voltage method is used as the technical basis, and a LabVIEW-based virtual system is adopted to measure the junction temperature of an LED. A LabVIEW-based data acquisition card makes a measurement result stable, accurate and reliable.
Description
Technical field
The present invention relates to a kind of semiconductor material detection system, particularly a kind of LED junction temperature measurement method based on LabVIEW
Background technology
The basic structure of LED is a semi-conductive p-n junction, and in the time that electric current flows through LED device, the temperature of p-n junction will rise.Conventionally because device chip all has very little size, so the temperature of LED chip can be considered as to junction temperature.The reason of LED junction temperature is because the electric energy adding is not all converted into luminous energy, but a part transforms into heat energy.
Measuring principle and the method for traditional forward voltage method are as follows
[following information source is known photoelectricity data], the junction temperature of LED is a key factor that affects light emitting diode property indices, the method for measuring LED junction temperature can be with obtaining by measuring the size of the forward voltage of LED at varying environment temperature.As shown in Figure 1, tested LED is placed in integrating sphere experimental principle, and integrating sphere is placed on the centre of constant temperature oven, and the light in integrating sphere imports SSP3112 fast spectral analysis instrument through silica fibre, can measure fast peak wavelength or the W/B ratio of LED.By thermopair and LED pin close contact, read the pin temperature at different heating electric current and varying environment temperature with temperature measurer.The temperature range of constant temperature oven is 0 DEG C-150 DEG C, 1 DEG C of precision.PC is the heating current to LED (IF) and reference current (IFR) by High-speed on-off control, and measures VF and the VFR under IF and IFR.
Heat is to dispel the heat from temperature eminence to temperature lower.The main heat dissipation path of LED is: tube core → cooling pad → printed board copper-clad → printed board → surrounding air.If the junction temperature of LED is TJ, the temperature of surrounding air is TA, and the temperature of cooling pad bottom is Tc (TJ>Tc>TA.
In hot conductive process, the heat conductivility difference of various materials, has different thermal resistances.If it is that thermal resistance that RJC (thermal resistance of LED), cooling pad are transmitted to PCB surface layer copper-clad is that the thermal resistance that RCB, PCB are transmitted to surrounding air is RBA that tube core is transmitted to the thermal resistance of cooling pad bottom surface, is transmitted to the entire thermal resistance RJA of air TA and each thermal resistance from the junction temperature TJ of tube core and closes and be: the unit of the each thermal resistance of RJA=RJC+RCB+RBA is DEG C/W.
Can understand like this: thermal resistance is less, its heat conductivility is better, and heat dispersion is better.
If the copper-clad of the cooling pad of LED and PCB adopts Reflow Soldering welded together, RCB=0, above formula can be write as: RJA=RJC+RBA
The computing formula of heat radiation
Be that the power consumption of TA, LED is PD if junction temperature is TJ, environment temperature, the pass of RJA and TJ, TA and PD is: RJA=(TJ-TA)/PD (1)
In formula, the unit of PD is W.The pass of the forward current IF of the forward voltage drop VF of PD and LED and LED is: PD=VF × IF (2)
If measured the temperature T C of LED cooling pad, (1) formula can be write as:
RJA=(TJ-TC)/PD+(TC-TA)/PD
RJC=(TJ-TC)/PD (3)
RBA=(TC-TA)/PD?(4)
In heat radiation is calculated, when having selected after great power LED, from data information, can find its RJC value; When determining after the forward current IF of LED, can calculate PD according to the VF of LED; If measured the temperature of TC, can obtain TJ by (3) formula.
Surveying before TC, first to do a brassboard (select certain PCB, determine certain area), the LED that burn-ons, input IF electric current, wait stable after, survey the cooling pad temperature T C of LED with K type thermoelectricity pair-point thermometer.
In (4) formula, TC and TA can measure, and PD can obtain, and RBA value can be calculated.If calculate TJ, substitution (1) formula can be obtained RJA.
Research LED junction temperature in real time, measuring method, technology accurately and fast, in theoretical and actual production, have very large meaning.By a large amount of gross datas and numerous luminous engineerings of LED, the experience of manufacturer: reduce LED junction temperature, thermal resistance, also will significantly improve reliability and the serviceable life of product in the luminescence efficiency that can greatly improve LED product.Therefore determine scientific and effective measuring method, design a set of accurately measuring system fast, be conducive to more science, reasonably carry out LED structural design and optimize LED illuminating engineering heat dissipation design.
Traditional forward voltage method, is the temperature effect of utilizing LED charge transport, is to calculate by the size of direct measurement forward instantaneous voltage of LED at varying environment temperature.But the main heat dissipation path of LED is: tube core → cooling pad → printed board copper-clad → printed board → surrounding air, and internal heat dissipation structures complexity, classic method can not record the distributivity of the temperature of chip, can only obtain medial temperature effect.And the transient voltage that classic method records, utilizes common voltage table to meet the demands, and error is larger.
Summary of the invention
The object of this invention is to provide a kind of LED junction temperature measurement method based on LabVIEW.
A kind of LED junction temperature measurement method based on LabVIEW of the present invention is achieved by following technical proposals: a kind of LED junction temperature measurement method based on LabVIEW of the present invention, comprise LED to be detected, thermostat, constant current source, data collecting card, computer testing platform, it is characterized in that: described method is to be technical basis by forward voltage method, virtual system by the data collecting card based on LabVIEW is measured in real time, described forward voltage method is to utilize the temperature effect of LED charge transport character, determine junction temperature by the forward voltage under surveying work electric current.Concrete grammar is first to measure voltage temperature coefficient K(V/K), then record experimental situation temperature T
1, LED to be measured powers up instantaneous voltage V
1forward voltage V after stable with LED to be measured
2, by p-n junction forward characteristic principle, can calculate LED junction temperature T to be measured
2.A kind of LED junction temperature measurement method based on LabVIEW of the present invention has following beneficial effect compared with prior art: the present invention is based on forward voltage method, adopts the virtual platform of LabVIEW independent research effectively to solve LED junction temperature measurement based on data collecting card.The present invention is carried out Real-time Collection, real time record, shows in real time LED two ends forward voltage by computer testing platform and LabVIEW data collecting card.And by voltage temperature coefficient K(V/K) accurate measure, can very accurately calculate LED junction temperature.
Brief description of the drawings
A kind of LED junction temperature measurement method based on LabVIEW of the present invention has following accompanying drawing:
Fig. 1: a kind of LED junction temperature measurement method system composition schematic diagram based on LabVIEW of the present invention;
Fig. 2: a kind of LED junction temperature measurement method voltage temperature coefficient K instrumentation plan based on LabVIEW of the present invention;
Fig. 3: a kind of LED junction temperature measurement method Software for Design process flow diagram based on LabVIEW of the present invention.
In figure: 1, constant current source; 2, switch; 3, LED to be measured; 4, constant temperature oven; 5, data collecting card; 6, computer testing platform; 7, sampling resistor; 8, current sample; 9, voltage sample.
Embodiment
Below in conjunction with drawings and Examples, a kind of LED junction temperature measurement method and technology scheme based on LabVIEW of the present invention is further described.
As shown in Figure 1-Figure 3, a kind of LED junction temperature measurement method based on LabVIEW comprises LED to be detected, thermostat, constant current source, data collecting card, computer testing platform, described method is to be technical basis, to be measured in real time by the virtual system of the data collecting card based on LabVIEW by forward voltage method, described forward voltage method is to utilize the temperature effect of LED charge transport character, determines junction temperature by the forward voltage under surveying work electric current.Concrete grammar is first to measure voltage temperature coefficient K(V/K), then record experimental situation temperature T
1, LED to be measured powers up instantaneous voltage V
1forward voltage V after stable with LED to be measured
2, by p-n junction forward characteristic principle, can calculate LED junction temperature T to be measured
2.
Described voltage temperature coefficient K(V/K) measuring method is under steady current, by measuring in thermostat T under different temperatures
xlED energising moment forward voltage initial value V to be measured
x, by T
xwith V
xslope after linear fit is voltage temperature coefficient K(V/K).
Embodiment.
The 6009 model data collecting cards that the present embodiment adopts America NI company to produce, notebook data capture card has 8 12 analog input ports, and 2 analog output mouths, when the variation range of input voltage is
20
, sample frequency is up to 48
.
1, voltage temperature coefficient K measures: LED sample to be measured and thermometer probe are put into constant temperature oven, set a steady current, and record current environmental temperature, Closing Switch, by LED to be measured access Acquisition Circuit, starts LabVIEW system, by LabVIEW system automatically according to collection period measurement demonstration and the record set, form forward voltage change curve and data file, and preserve, after the cycle completes, open switch.By changing calorstat temperature, repeat above step, by LabVIEW systematic survey, record under different temperatures corresponding forward voltage change curve and data.The computational algorithm of voltage temperature coefficient K is by the slope numerical value of the linear relationship presenting after the initial forward voltage values under each environment temperature under this steady current and the matching of relevant temperature value.
Algorithm fundamental formular is:
K=（V
X
-V
Y
）/(T
X
-T
Y
)
In formula
v x -for
t x forward voltage at temperature,
v y for
t y forward voltage at temperature.
2, the measuring and calculating of junction temperature: record experimental situation temperature T
1, within the designated cycle cycle, measured LED to be measured by LabVIEW system and power up instantaneous voltage V
1forward voltage V after stable with LED to be measured
2, by p-n junction forward characteristic principle, can calculate LED junction temperature T to be measured
2.Junction temperature computational algorithm formula is:
T
2
=T
1
+（V
2
－V
1
）/K。
Claims (2)
1. the LED junction temperature measurement method based on LabVIEW, comprise LED to be detected, thermostat, constant current source, data collecting card, computer testing platform, it is characterized in that: described method is to be technical basis, to be measured in real time by the virtual system of the data collecting card based on LabVIEW by forward voltage method, described forward voltage method is to utilize the temperature effect of LED charge transport character, determines junction temperature by the forward voltage under surveying work electric current; Concrete grammar is first to measure voltage temperature coefficient K(V/K), then record experimental situation temperature T
1, LED to be measured powers up instantaneous voltage V
1forward voltage V after stable with LED to be measured
2, by p-n junction forward characteristic principle, can calculate LED junction temperature T to be measured
2.
2. the LED junction temperature measurement method based on LabVIEW according to claim 1, is characterized in that: described voltage temperature coefficient K(V/K) measuring method is under steady current, by measuring in thermostat T under different temperatures
xlED energising moment forward voltage initial value V to be measured
x, by T
xwith V
xslope after linear fit is voltage temperature coefficient K(V/K).
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|---|---|---|---|
| CN201210538233.8A CN103868613A (en) | 2012-12-13 | 2012-12-13 | LabVIEW-based LED junction temperature measurement method |
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| CN201210538233.8A CN103868613A (en) | 2012-12-13 | 2012-12-13 | LabVIEW-based LED junction temperature measurement method |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104020405A (en) * | 2014-06-26 | 2014-09-03 | 厦门大学 | Pulse type power mode LED voltage-current-junction temperature characteristic testing device |
| CN104848961A (en) * | 2015-05-14 | 2015-08-19 | 哈尔滨工业大学 | Saturation-conduction-voltage-drop-based temperature calibration platform for measuring IGBT junction temperature and method for realizing IGBT junction temperature measurement |
| CN107300663A (en) * | 2017-07-06 | 2017-10-27 | 扬州扬杰电子科技股份有限公司 | A kind of semiconductor junction temperature test device and its method of testing |
| CN107607850A (en) * | 2017-09-21 | 2018-01-19 | 重庆秉为科技有限公司 | A kind of radiation performance of semiconductor lighting product detection means |
| CN113834996A (en) * | 2021-11-30 | 2021-12-24 | 北京京瀚禹电子工程技术有限公司 | Parameter measuring method and device for burn-in test of power device and electronic equipment |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104020405A (en) * | 2014-06-26 | 2014-09-03 | 厦门大学 | Pulse type power mode LED voltage-current-junction temperature characteristic testing device |
| CN104848961A (en) * | 2015-05-14 | 2015-08-19 | 哈尔滨工业大学 | Saturation-conduction-voltage-drop-based temperature calibration platform for measuring IGBT junction temperature and method for realizing IGBT junction temperature measurement |
| CN107300663A (en) * | 2017-07-06 | 2017-10-27 | 扬州扬杰电子科技股份有限公司 | A kind of semiconductor junction temperature test device and its method of testing |
| CN107300663B (en) * | 2017-07-06 | 2023-10-03 | 扬州扬杰电子科技股份有限公司 | Test method of semiconductor junction temperature test device |
| CN107607850A (en) * | 2017-09-21 | 2018-01-19 | 重庆秉为科技有限公司 | A kind of radiation performance of semiconductor lighting product detection means |
| CN113834996A (en) * | 2021-11-30 | 2021-12-24 | 北京京瀚禹电子工程技术有限公司 | Parameter measuring method and device for burn-in test of power device and electronic equipment |
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