Nghiên cứu hệ thống đo dòng phát sáng của các đi ốt phát sáng của viện đo lường việt nam

Journal of Science & Technology 101 (2014) 188-191 Study on Luminous Flux Measurement System of Light-Emitting Diodes in Vietnam Metrology Institute Quan Cao Xuan H Xuan K J T H Nga.N.P, Son Vo Thach '-* 'School of Engineering Physics, Hanoi University ofScience and Technology No-1, Dai Co Viet Sir., Hai Ba Trung, Ha Noi, Viet Nam ^Photometry and Radiometry Laboratory, Vietnam Metrology Institute Received March 5, 2014, accepted Aprd 22, 2014 Abstract Light-emitting diodes (LEDs) are used tn various applications due to their small size, durability and energy efficiency However, the optical properties of LEDs are more complex than those ot In candescent lamps In order to measure the luminous flux of LEDs with low uncertainty, the equipment used for the measurements needs to be carefully charactenzed In this paper, measurement system constructed for luminous flux measunng of LEDs is an integrating sphere system The integrating sphere designed for measurement of LEDs has ports for LED photometer head, auxiliary lamp, spectroradiometer to be equipped with thermoelectric cooler (TEC) and Integrating sphere with a diameter d = m and inner sphere is coated with barium sulphate (BaSO^) The study results show that barium sulphate layer has high average value of reflectivity of about 92.6 % in the visible light region Uncertainty for luminous flux measurements related to this system is estimated at 1.78 % at a confidence level P=95%, k = 2, in about 10 to 4000 Im for COB LEDs The results obtained were compared with lllumia Pro System 500-100 - Labsphere - USA Keywords COB, Luminous flux, Integrating sphere, Reflectance, Uncertainty Introduction Light emitting diodes (LEDs) are solid-slate lighting sources which are increasingly being used in display backlightings, commumcahons, medical services, signages, and general illumination [1-6] LEDs have better mechanical impact resistance compared to fraditional lighting LEDs are also eco-friendly products with no mercury and low health impact due to low UV radiation, LED is one of high efficient illuminations which can replace the incandescent lamp and compete with the fluorescent mbe in the recent years LEDs that have a single colour are over ten times more efficient than incandescent lamps White LEDs are more than twice as efficient as incandescent lamps [3j The luminous flux of LEDs can be measured using Sphere-spectroradiometer system Sphere photometer system and Goniophotometer system [2,3], The total luminous flux is then obtained by integrating the luminance values over the area of the virtual surface defined by the measurement geometry In this paper, we developed a new integrating sphere photometer specfra-radiometer system for luminous flux measurement of COB LEDs " Con-esponding author (+84)904 132,226 Email.son.vothach@hust.edu.vn Setup integrating spectroradiometer system Integrating specfroradiometer system was a product of Photometry and Radiometry Laboratory, Vietnam Mefrology institute The integrating sphere was coaled by Barium sulphate as diffiising reflectance material Diffuse reflectance surface in integrating sphere is prepared by spraying method, BaSOi powder (France), polyvinyl alcohol (France) and pure water as precursor Diffuse reflectance surface deposited on the surface of integrating sphere (subsfrate) with technological parameters: distance from the spray nozzle to the substrate d = 15 -7-25 cm, temperature substrate T = 25 -=- 30 "C, and injection pressure p = 3.8 -=4.5 kg/cm^ The total luminous flux measurement We use COB LEDs (Chip On Board Light NSBxL066A-10 W was Emitting Diodes) Nichia-Japan in manufactured by experiments Firstly, the total luminous flux standard lamp (SCL-1400-E120, U = 1% at k = 2, Japan) is mounted in an integrating sphere, with the lit geomefric as showed in Fig Journal ofScience & Technology 101 (2014) 188-191 Fig Standard lanqj is mounted in an mtegyating sphere Fig COB LEDs is mounted on thermoelectric cooler The COB LEDs mounted on a thermoelectnc cooler (TEC) in an integrating sphere, with the 2n geometric, as showed in Fig layer of specfral reflectance has large variations in the spectral range of 380 nm to 570 nm The variation reflectance values between one layer and two layers is about 2.0%, and that between two layers and three layers is about 2.8%, three layers and four layers is about 2.2%, However, between four layers and five layers is only aboul 0,23 Therefore, the coating of five layers is an appropriate requirement, The photometer head (P30SCT, LMT) is used in this system, with V(>.) approximation f) < 1,0% , cos-conection f2 < 1,5 % , sensitivity about 15 to 26 tiA/lx and calibrated precisely Standard Illuminate A, The Spectroradiometer (CS-2000A, Konica Minolta) IS used for spectrum mismatch measurement, -with half of bandwidth: 5iim The reflectance spectra of coating layers are measured by UVA'is/NIR Spectrometer (Serial number: I050LI306131) Results and Discussion Setup integrating spectroradiometer system sphere TTie total luminous Jlux of COB LEDs The luminous flux of the standard lamp is measured and showed in table The luminous flux of COB LEDs can be calculated by the luminous flux of the standard lamp according to the following equation [4, 5], photometer As a matter of fact, coating layers quality in integrating sphere is very important We investigated the effects of number of coating layers to reflectance The reflectance specfra of coating layers are shown in fig 3, We can see that, the reflectance increases for increasing number of coating layers An average reflectance value of 92.6% is obtained, this is an appropnate requirement The reflectance is of about p(k) =5 0.8 as recommended by CIE [8], "•cc/ Where- 4^ '^scf • ^ (1) is the luminous flux of the standard lamp, 4^^ is the luminous flux of the measured lamp, the self-absorption conection factor kabi [3,5] detemuned using the auxiliary lamp placed on the integrating sphere wall, the spectral mismatch conection factor ktcf determined from spectral power distnbution of the standard and measured lamps [3,5], the sphere response conection factor kscf determined from the angular luminous intensity distribution of the standard and measured lamps distnbution fiinction [3,5] These conection factors are calculated and they have values of about kab5^=1.023,kccrL00488,kscrI.000013[4,5] Table i COB LEDs Luminous flux measuremeni results Luminous flux Lamp No measurements -Pjlm) 1325 L066A/001 1328 L066A/002 1305 L066 A/004 Fig The reflectance specfra of coating layers The study results show the coating of the first Journal of Science & Technology 101(2014) 188-191 Table The luminous flux of lamps measured with (VMI-PR-OOl)-VMl• and (Illuma , Labsphere-USA systems Lamp No L066A/001 L066A/002 L066 A/004 Luminous flux Lamp voltage [V] VMI-PR-0 01 32 41 32 57 32,42 Illumia Pro 500-100 32.40 32,59 32 43 VMI-PR-O lUunua Pro 01 500-100 1325 1306 1328 1315 1305 1319 ""'>ã \lisolute , v,ces "eô differences [V] e [lm] (VMI/Labsphere USA) -1 031«10' 0.61>cl0-' 1.45«10' 0.99x!0-> mixin-' 1.10x10-' Table Uncertainty budget for luminous flux measurements Source of uncertainty Standard lamp Test lamp Symbol Uncertainty of the primary standard lamp Repeatability of the measurement Lamp standard mounting reproducibility Stability of lamp cunent Repeatability of the measurement Test lamp mounting reproducibility Stability of lamp current The self-absorption correction factor The spectral mismatch conection factor The sphere response conection factor stability of m 0.50 "AyX 0.04 0,023 0.06 -AyX 0,009 0.0025 0.25 35 0.49 0.0004 0.05 Photocurrent measurement Long-term Relative standard uncertainty the 0,317 calibration system 0.89 Combined relative standard uncertainty Relative expanded uncertainty The luminous flux of lamps measured with (VMl-PR-OOl)-VMI and (Illumia Pro 500-100)Labsphere-USA systems, their results are given in Table Average voltage difference (VMI/Labsphere -1) of compared lamp was 0,41^10"^ with absolute standard deviation of O.I8>:10-' and average luminous flux difference of 1.18>:10"^ with absolute standard deviation of 2,4x10'^ as seen in the table The uncertainty analysis for luminous flux measurement is presented in Table All known uncertainty components have been included in the analysis regardless of whether they have significant effects on the combined uncertainty [4, 5] Uily, k=2 Conclusion Integrating sphere photometer spectroradiometer system was manufactured by Photometry and Radiometry Laboratory, Vietaam Metrology Instimte The average reflectance value of integrating sphere coating layer is about 92.6 % The luminous flux of LEDs is detemiined by integratmg sphere photometer specfroradiometer system The overaU uncertaint> integrating sphere photometer system was estimated as 78 % ^ ] j^y j[,jg liometer "idence Journal ofScience & Technology 101 (2014) 188-191 level This method has been successfiilly apphed to the range of 10 to 4000 Im for LEDs It is also possible to calibrate light emitting diodes type by using the established system Acknowledgements This work was partially supported by the Vietnam Metrology Institute as part of the research program No 1198/QD-TDC, dated June 29,2012 References [I] Kraincs MR, Shchekin OB, Mueller-Mach R, Mueller GO, Zhou L, Harbers G, "Status and future of high-power light-emitting diodes for solid-state hghtmg", J Disp Teehnol, (2007) 160-75 [2] Steigerwald DA, Bhat JC, Collins D, Fletcher RM, Holcomb MO, Ludowise MJ, "Illumination with solid state lighting technology", IEEE J Sel Top Quant Elecfron, (2002) 310-20 [3] Steranka FM, Bhat J, Collins D, Cook L, Craford MG, Fletcher R, '• High power LEDs technology status and market applications" Phys Status Sohdi A, 194 (2002) 380-8 [4] Schubert EF, Kim JK, Luo H, Xi J-Q, "Solid-state lighting-a benevolent technology" Rep Prog Phys, 69 (2006) 3069-99 [5] Aoyama Y, Yachi T, "An LED module anay system designed for streetlight use", IEEE Energy 2030, (2008) 1-5, [6] Vitlori R, Scabuni A, "New solid state technologies and light emission diodes as a mean ot" control and lighting source applicable to explosion proof equipment, with the scope to reduce maintenance, to limit Ihe nsk of bad maintenance and to expand the plants' life" PCIC Europe, (2009) 193-8 [7] Nichia Application Note, "COB Assembly and Handling", SE-AP00003A, Mar 30,2012 [8] Casimer Decusatis "Handbook of Applied Photometry", American Institute of Physics, ISBN 1-56396-416-3 [9] "Electrical and photomefric measurements of solid-state hghting products", lES LM-79-08 [10] Part of the research program 1198/OD-TDC, dated June 29 2012 No [II] Luminous Flux - Calibration procedure, CP-08, Viemam metrology  ... type by using the established system Acknowledgements This work was partially supported by the Vietnam Metrology Institute as part of the research program No 1198/QD-TDC, dated June 29,2012 References