Pub Date : 2015-12-21DOI: 10.1109/SSLCHINA.2015.7360687
H. Ye, Hongyu Tang, S. Leung, C. Qian, Xuejun Fan, Guoqi Zhang
The drive to increase electrical currents input, and to achieve high lumen output for High Brightness Light Emitting Diode (HB LED) has led to a series of thermal problems. Hence, thermal management is one of key design parameters as the temperature directly affecting the maximum light output, quality, reliability and life time. For LED arrays, the arrangement of chips will affect the thermal performance and junction temperature is very important in the design. However, because direct junction temperature determination is hard to detect due to the encapsulation, indirect methods are more preferred. Among them, the diode forward-voltage method is the most accurate one. Therefore, we used the diode forward-voltage method to optimize thermal design of LED arrays in this work.
{"title":"Junction temperature measurement to optimize thermal design of LED arrays","authors":"H. Ye, Hongyu Tang, S. Leung, C. Qian, Xuejun Fan, Guoqi Zhang","doi":"10.1109/SSLCHINA.2015.7360687","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360687","url":null,"abstract":"The drive to increase electrical currents input, and to achieve high lumen output for High Brightness Light Emitting Diode (HB LED) has led to a series of thermal problems. Hence, thermal management is one of key design parameters as the temperature directly affecting the maximum light output, quality, reliability and life time. For LED arrays, the arrangement of chips will affect the thermal performance and junction temperature is very important in the design. However, because direct junction temperature determination is hard to detect due to the encapsulation, indirect methods are more preferred. Among them, the diode forward-voltage method is the most accurate one. Therefore, we used the diode forward-voltage method to optimize thermal design of LED arrays in this work.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"70 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129016379","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-21DOI: 10.1109/SSLCHINA.2015.7360682
Jiaping Shao
The COB (Chip-on-Board) arrays are utilized comprehensively, especially in commercial lighting and indoor lighting. Here we would like to discuss the recent progress of COB technology and color quality metrics, including SC5 technology, lumen output, light efficacy, light emitting surface, center beam candlepower, COB performance in SMT LED, correlated color temperature, color consistency, EasyWhite technology, color rendering index, R9, special color points, color fidelity, color gamut, and TrueWhite technology.
{"title":"Recent progress of COB technology and color quality metrics","authors":"Jiaping Shao","doi":"10.1109/SSLCHINA.2015.7360682","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360682","url":null,"abstract":"The COB (Chip-on-Board) arrays are utilized comprehensively, especially in commercial lighting and indoor lighting. Here we would like to discuss the recent progress of COB technology and color quality metrics, including SC5 technology, lumen output, light efficacy, light emitting surface, center beam candlepower, COB performance in SMT LED, correlated color temperature, color consistency, EasyWhite technology, color rendering index, R9, special color points, color fidelity, color gamut, and TrueWhite technology.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132948339","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-21DOI: 10.1109/SSLCHINA.2015.7360702
Xinke Wu, Chen Hu, G. Hua
Anasymmetric PWM controlled LLCC LED driver with capacitor connected in series with secondary windingof the transformer is proposed. Due to the presence of the secondary side resonant capacitor, the DC bias of the magnetizing current can be eliminated when asymmetric PWM control is employed. Because the switching frequency is fixed regardless of the load variation, the efficiency of light load is improved compared to conventional frequency controlled LLC topology, especially in dimming applications. The operating principle and circuit simplification of the secondary side circuit are presented. A two outputs LED driver prototype with 100V-200V output, 0.035A-0.35A/channel is built up to verify the theoretical analysis.
{"title":"Asymmetric PWM controlled LLCC resonant half bridge dual outputs LED driver","authors":"Xinke Wu, Chen Hu, G. Hua","doi":"10.1109/SSLCHINA.2015.7360702","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360702","url":null,"abstract":"Anasymmetric PWM controlled LLCC LED driver with capacitor connected in series with secondary windingof the transformer is proposed. Due to the presence of the secondary side resonant capacitor, the DC bias of the magnetizing current can be eliminated when asymmetric PWM control is employed. Because the switching frequency is fixed regardless of the load variation, the efficiency of light load is improved compared to conventional frequency controlled LLC topology, especially in dimming applications. The operating principle and circuit simplification of the secondary side circuit are presented. A two outputs LED driver prototype with 100V-200V output, 0.035A-0.35A/channel is built up to verify the theoretical analysis.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130751782","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-21DOI: 10.1109/SSLCHINA.2015.7360678
Li Kunzhui, Xu Shaohua, Tang Yuchuang, Weng Xiangze, Wang Yi
This paper focus our attention on the deep considerations for LED package technology. The research includes the following content: (i) the influence of binding force between the chip and substrate, the leakage rate of silver paste conductive adhesive, the failure rate of light emission based on different glue quantities from different companies are studied carefully; (ii) a variety of abnormalities appeared in the process of die bond are demonstrated, and some failure reasons of lighting extracting are analyzed, and the correct processing method for dealing of these abnormalities are suggested; (iii) the influence of the size, abrasiveness, the tear force, and the power of porcelain mouth on package product performance and the quality are discussed; (iv) the influence of phosphor particle size, the amount of anti-settling powder, the viscosity of the fluorescent glue, and the baking conditions on white LED color coordinates and color concentration are analyzed. For same batch of the same chip packaging technology with same device setting parameters, there are still existing a certain bias in lighting output power, color coordinates and color concentration etc. It is found that many key factors are coming from the less consideration for package materials. The uneven distribution of mixing or dispensing phosphors is also a key factor to influence the package quality of SMD and COB light source.
{"title":"Deep considerations on LED package technology","authors":"Li Kunzhui, Xu Shaohua, Tang Yuchuang, Weng Xiangze, Wang Yi","doi":"10.1109/SSLCHINA.2015.7360678","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360678","url":null,"abstract":"This paper focus our attention on the deep considerations for LED package technology. The research includes the following content: (i) the influence of binding force between the chip and substrate, the leakage rate of silver paste conductive adhesive, the failure rate of light emission based on different glue quantities from different companies are studied carefully; (ii) a variety of abnormalities appeared in the process of die bond are demonstrated, and some failure reasons of lighting extracting are analyzed, and the correct processing method for dealing of these abnormalities are suggested; (iii) the influence of the size, abrasiveness, the tear force, and the power of porcelain mouth on package product performance and the quality are discussed; (iv) the influence of phosphor particle size, the amount of anti-settling powder, the viscosity of the fluorescent glue, and the baking conditions on white LED color coordinates and color concentration are analyzed. For same batch of the same chip packaging technology with same device setting parameters, there are still existing a certain bias in lighting output power, color coordinates and color concentration etc. It is found that many key factors are coming from the less consideration for package materials. The uneven distribution of mixing or dispensing phosphors is also a key factor to influence the package quality of SMD and COB light source.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126651181","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-21DOI: 10.1109/SSLCHINA.2015.7360690
M. Meneghini, C. de Santi, M. Buffolo, A. Munaretto, G. Meneghesso, E. Zanoni
This paper reviews the most relevant mechanisms responsible for the gradual and catastrophic failure of InGaN-based light emitting diodes, for application in general lighting. Based on recent results obtained on state-of-the-art LEDs and lamps, we discuss the following: (i) the lifetime of 800 lm retrofit lamps is still limited by the early degradation of the InGaN-LEDs, of the plastic encapsulant/reflectors, and of the driving circuitry. High temperatures and/or poor thermal management can significantly reduce the lifetime of the lamps in real-life applications. (ii) mid-power LEDs, that represent a low-cost widely adopted alternative to power devices, can suffer from both chip and package degradation, that result in a significant decrease in optical power and shift in the chromatic properties. (iii) Electrical overstress (EOS) can result in the sudden failure of power LEDs; failure can be due to the fusion of the bonding wires, to the degradation of the metal lines, or to the cracking of the semiconductor material. The results presented within this paper provide an update on the state-of-the-art of LED reliability.
{"title":"Towards high reliability GaN LEDs: Understanding the physical origin of gradual and catastrophic failure","authors":"M. Meneghini, C. de Santi, M. Buffolo, A. Munaretto, G. Meneghesso, E. Zanoni","doi":"10.1109/SSLCHINA.2015.7360690","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360690","url":null,"abstract":"This paper reviews the most relevant mechanisms responsible for the gradual and catastrophic failure of InGaN-based light emitting diodes, for application in general lighting. Based on recent results obtained on state-of-the-art LEDs and lamps, we discuss the following: (i) the lifetime of 800 lm retrofit lamps is still limited by the early degradation of the InGaN-LEDs, of the plastic encapsulant/reflectors, and of the driving circuitry. High temperatures and/or poor thermal management can significantly reduce the lifetime of the lamps in real-life applications. (ii) mid-power LEDs, that represent a low-cost widely adopted alternative to power devices, can suffer from both chip and package degradation, that result in a significant decrease in optical power and shift in the chromatic properties. (iii) Electrical overstress (EOS) can result in the sudden failure of power LEDs; failure can be due to the fusion of the bonding wires, to the degradation of the metal lines, or to the cracking of the semiconductor material. The results presented within this paper provide an update on the state-of-the-art of LED reliability.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"71 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122540506","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-21DOI: 10.1109/SSLCHINA.2015.7360700
Haoran Li, Zechun Liu, Yaojie Sun, Yandan Lin
LEDs are widely used in illumination, indication and dimming area. Most commercial LED light dimming system today can achieve rough color temperature regulation with high but nonadjustable color rendering index. However most of these systems are designed for daily illumination, which cannot meet the precise requirement in the laboratory. In this work we achieved the design of color combination system with tunable luminance, color temperature, chromaticity coordinate and color rendering index with three to five color LEDs, which meets the experimental requirement to the greatest extent.
{"title":"Design of LED dimming system with the specific target parameter control function","authors":"Haoran Li, Zechun Liu, Yaojie Sun, Yandan Lin","doi":"10.1109/SSLCHINA.2015.7360700","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360700","url":null,"abstract":"LEDs are widely used in illumination, indication and dimming area. Most commercial LED light dimming system today can achieve rough color temperature regulation with high but nonadjustable color rendering index. However most of these systems are designed for daily illumination, which cannot meet the precise requirement in the laboratory. In this work we achieved the design of color combination system with tunable luminance, color temperature, chromaticity coordinate and color rendering index with three to five color LEDs, which meets the experimental requirement to the greatest extent.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"45 4-5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116507418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-21DOI: 10.1109/SSLCHINA.2015.7360679
Qinjin Wang, Jun Ma, Teng Zhan, X. Yi, Enqing Guo, Zhiqiang Liu, Ting Wang, Xiansong Fu, Junxi Wang, Guohong Wang, Jinmin Li
In this work, we first proposed an innovation on GaN p-type reflective electrode in flip-chip LEDs (FCLEDs) using a novel method so called electroless silver plating (ESP). In our ESP method, we use chemical way to form a perfect Ag reflector, differ from traditional fabrication of p-type reflective electrode using electron beam deposition (EB). Under our investigation, the Ag reflective electrode formed by ESP possesses better optical and electric characteristics. Compared with EB, the reflectance of electrode by ESP over the whole visible light spectrum was 93%, higher than EB samples, which only show 82%. Otherwise, ohmic contact characteristic between metal and GaN also shows the same rule as reflectance. ESP samples exhibit better specific contact resistance than EB samples, they're 6.5 * 10-3Ω · cm2 and 6 * 10-2Ω· cm2, respectively. Moreover, the fantastic results of I-V as well as L-I measurement likewise verify electroless silver plating to be a potential manufacturing technology of p-type reflective electrode.
{"title":"A subversive innovation on GaN P-type reflective electrode using electroless silver plating","authors":"Qinjin Wang, Jun Ma, Teng Zhan, X. Yi, Enqing Guo, Zhiqiang Liu, Ting Wang, Xiansong Fu, Junxi Wang, Guohong Wang, Jinmin Li","doi":"10.1109/SSLCHINA.2015.7360679","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360679","url":null,"abstract":"In this work, we first proposed an innovation on GaN p-type reflective electrode in flip-chip LEDs (FCLEDs) using a novel method so called electroless silver plating (ESP). In our ESP method, we use chemical way to form a perfect Ag reflector, differ from traditional fabrication of p-type reflective electrode using electron beam deposition (EB). Under our investigation, the Ag reflective electrode formed by ESP possesses better optical and electric characteristics. Compared with EB, the reflectance of electrode by ESP over the whole visible light spectrum was 93%, higher than EB samples, which only show 82%. Otherwise, ohmic contact characteristic between metal and GaN also shows the same rule as reflectance. ESP samples exhibit better specific contact resistance than EB samples, they're 6.5 * 10-3Ω · cm2 and 6 * 10-2Ω· cm2, respectively. Moreover, the fantastic results of I-V as well as L-I measurement likewise verify electroless silver plating to be a potential manufacturing technology of p-type reflective electrode.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126522437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-21DOI: 10.1109/SSLCHINA.2015.7360677
Yanan Guo, Yun Zhang, Junxi Wang, Jianchang Yan, Yingdong Tian, Xiang Chen, Lili Sun, T. Wei, Jinmin Li
Recently, our group has demonstrated several methods to improve the performance of deep ultraviolet (DUV) LEDs and LDs. A high-quality and crack-free AlN template has been achieved by inserting multiple middle-temperature AlN layers with modulated source flow. Using silicon-doped AlGaN MQWs, the internal quantum efficiency (IQE) has been increased by 41% due to the improvement of crystal and interface quality. An easy-facilitative Al reflector technique has been also proposed to enhance the light extraction efficiency (LEE). We obtained light output power (LOP) of 6.31 mW for the 280-nm LED at 100 mA, and realized optical pumping stimulated emission at 288 nm.
{"title":"Development of AlGaN-based deep ultraviolet light-emitting diodes and laser diodes","authors":"Yanan Guo, Yun Zhang, Junxi Wang, Jianchang Yan, Yingdong Tian, Xiang Chen, Lili Sun, T. Wei, Jinmin Li","doi":"10.1109/SSLCHINA.2015.7360677","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360677","url":null,"abstract":"Recently, our group has demonstrated several methods to improve the performance of deep ultraviolet (DUV) LEDs and LDs. A high-quality and crack-free AlN template has been achieved by inserting multiple middle-temperature AlN layers with modulated source flow. Using silicon-doped AlGaN MQWs, the internal quantum efficiency (IQE) has been increased by 41% due to the improvement of crystal and interface quality. An easy-facilitative Al reflector technique has been also proposed to enhance the light extraction efficiency (LEE). We obtained light output power (LOP) of 6.31 mW for the 280-nm LED at 100 mA, and realized optical pumping stimulated emission at 288 nm.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"34 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114062123","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-21DOI: 10.1109/SSLCHINA.2015.7360711
Yanda Chen, Y. Tu, Fan Lu, Lu Liu, Lili Wang
The difference of perceived glare between two different working modes (i.e., computer work and reading/writing) caused by LEDs in office was investigated. Discomfort glare are evaluated in two aspects, the general glare and overhead glare. For general glare study, all the LED luminaires installed in the ceiling of the experimental room were switched on to realize a uniform lighting distribution like a normal office lighting design. While for overhead glare assessment, only one single LED luminaire just above the subject was switched on. The results show that the perceived general glare increased with the luminance level of the luminaires significantly in both working modes; and the perceived overhead glare was found to be significantly influenced by luminance level and viewing angle only in computer working mode. Both perceived general glare and perceived overhead glare in computer working mode were more serious than that in the reading/writing working mode.
{"title":"Glare perception in office lighting with LEDs for different working modes","authors":"Yanda Chen, Y. Tu, Fan Lu, Lu Liu, Lili Wang","doi":"10.1109/SSLCHINA.2015.7360711","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360711","url":null,"abstract":"The difference of perceived glare between two different working modes (i.e., computer work and reading/writing) caused by LEDs in office was investigated. Discomfort glare are evaluated in two aspects, the general glare and overhead glare. For general glare study, all the LED luminaires installed in the ceiling of the experimental room were switched on to realize a uniform lighting distribution like a normal office lighting design. While for overhead glare assessment, only one single LED luminaire just above the subject was switched on. The results show that the perceived general glare increased with the luminance level of the luminaires significantly in both working modes; and the perceived overhead glare was found to be significantly influenced by luminance level and viewing angle only in computer working mode. Both perceived general glare and perceived overhead glare in computer working mode were more serious than that in the reading/writing working mode.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129059604","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2015-12-21DOI: 10.1109/SSLCHINA.2015.7360689
Guangjun Lu, W. V. van Driel, Xuejun Fan, M. Y. Mehr, Jiajie Fan, C. Qian, G. Zhang
Color shift mechanism of LED lighting is complex due to its much more comprehensive structure, generally composed of LED die, phosphor, silicone, reflector, diffusers, and so on, each of them may contribute to the color shift during operation. This paper proposed a breakdown method for the color shift study and investigation on the LED based luminaire level products. For the downlight investigated in this paper, the LED packages part has the most important contribution in color shift, higher than 1sdcm even under the normal operation conditions of room temperature. Both humidity and temperature conditions can be used to accelerate the color shift of the mid power 5630 package and the humidity has a stronger acceleration. The reflective part contributes far less than 1 sdcm even when the reflective material crumbles after 4000hours of humidity test under certain conditions.
{"title":"A POF based breakdown method for LED lighting color shift reliability","authors":"Guangjun Lu, W. V. van Driel, Xuejun Fan, M. Y. Mehr, Jiajie Fan, C. Qian, G. Zhang","doi":"10.1109/SSLCHINA.2015.7360689","DOIUrl":"https://doi.org/10.1109/SSLCHINA.2015.7360689","url":null,"abstract":"Color shift mechanism of LED lighting is complex due to its much more comprehensive structure, generally composed of LED die, phosphor, silicone, reflector, diffusers, and so on, each of them may contribute to the color shift during operation. This paper proposed a breakdown method for the color shift study and investigation on the LED based luminaire level products. For the downlight investigated in this paper, the LED packages part has the most important contribution in color shift, higher than 1sdcm even under the normal operation conditions of room temperature. Both humidity and temperature conditions can be used to accelerate the color shift of the mid power 5630 package and the humidity has a stronger acceleration. The reflective part contributes far less than 1 sdcm even when the reflective material crumbles after 4000hours of humidity test under certain conditions.","PeriodicalId":331882,"journal":{"name":"2015 12th China International Forum on Solid State Lighting (SSLCHINA)","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2015-12-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124124308","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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