The purpose of this paper is to present a methodology for optimizing the geometry of the LED （light emitting diode） secondary lens. The research objective is to uniform the illumination distribution on a target plan...The purpose of this paper is to present a methodology for optimizing the geometry of the LED （light emitting diode） secondary lens. The research objective is to uniform the illumination distribution on a target plane for nonimaging application. In order to achieve this, a software that simulates ray tracing is used, in conjunction with a heuristic process for enhancing the optimized parameters that form the geometry of the LED secondary lens. Spherical lenses was opted for optimization due to its lower manufacture complexity.展开更多
The operating circuits for LED （light emitting diode） lamp composed of diodes and DC capacitors only are proposed. The proposed circuit is based on a double-voltage rectifier circuit and a Cockcroft-Walton circuit. ...The operating circuits for LED （light emitting diode） lamp composed of diodes and DC capacitors only are proposed. The proposed circuit is based on a double-voltage rectifier circuit and a Cockcroft-Walton circuit. The circuit can operate LED without flicker, and is free from switching noise since high frequency switching circuit is not used. To replace an AC capacitor by a DC capacitor for the ballast, a diode is connected across the capacitor in parallel, and the operating voltage of LED unit is kept at the value greater than the peak voltage of the input power source. The circuit realizes high efficiency and high input power factor compared with the operating circuits on the market. Cockcroft-Walton-type circuit can operate many LED devices in series connection. Series connection is preferable for fabricating LED unit of a constant voltage characteristic. Moreover, fairly flat waveform of LED operating current is realized by Cockcrofl-Walton-type circuit, even though capacitor ballast is used.展开更多
This paper summarizes different kinds of heat sinks on the market for high power LED lamps. Analysis is made on the thermal model of LED, PCB and heat sink separately with a simplified mode provided. Two examples of s...This paper summarizes different kinds of heat sinks on the market for high power LED lamps. Analysis is made on the thermal model of LED, PCB and heat sink separately with a simplified mode provided. Two examples of simulation are illustrated as a demonstration for the thermal simulation as guidance for LED lamp design.展开更多
In order to verify which of the distributions and established methods of reliability model are more suitable for the analysis of the accelerated aging of LED lamp, three established methods （approximate method, analy...In order to verify which of the distributions and established methods of reliability model are more suitable for the analysis of the accelerated aging of LED lamp, three established methods （approximate method, analytical method and two-stage method） of reliability model are used to analyze the experimental data under the condition of the Weibull distribution and Lognormal distribution, in this paper. Ten LED lamps are selected for the accelerated aging experiment and the luminous fluxes are measured at an accelerated aging temperature. AIC information criterion is adopted in the evaluation of the models. The results show that the accuracies of the analytical method and the two-stage method are higher than that of the approximation method, with the widths of confidence intervals of unknown parameters of the reliability model being the smallest for the two-stage method. In a comparison between the two types of distributions, the accuracies are nearly identical.展开更多
To acquire a rational minimum cut-off time and the precision of lifetime prediction with respect to cut-off time for the accelerated aging test of LED lamps, fifth-order moving average error estimation is adopted in t...To acquire a rational minimum cut-off time and the precision of lifetime prediction with respect to cut-off time for the accelerated aging test of LED lamps, fifth-order moving average error estimation is adopted in this paper. Eighteen LED lamps from the same batch are selected for two accelerated aging tests, with 10 samples at 80 ℃ and eight samples at 85 ℃. First, the accelerated lifetime of each lamp is acquired by exponential fitting of the lumen maintenances of the lamp for a certain cut-offtime With the acquired lifetimes of all lamps, the two-parameter Weibull distribution of the failure probability is obtained, and the medium lifetime is calculated. Then, the precision of the medium lifetime prediction for different cut-off times is obtained by moving average error estimation. It is shown that there exists a minimum cut-off time for the accelerated aging test, which can be determined by the variation of the moving average error versus the cut-offtime. When the cut-off time is less than this value, the lifetime estimation is irrational. For a given cut-off time, the precision of lifetime prediction can be computed by average error evaluation, and the error of lifetime estimation decreases gradually as the cut-off time- increases. The minimum cut-off time and medium lifetime of LED lamps are both sensitive to thermal stress. The minimum cut-off time is 1104 h with the lifetime esti- mation error of 1.15% for the test at 80 ~C, and 936 h with the lifetime estimation error of 1.24% for the test at 85 ℃. With the lifetime estimation error of about 0.46%, the median lifetimes are 7310 h and 4598 h for the tests at 80 ℃ and 85℃, respectively.展开更多
The Rwandan State-run Energy Water and Sanitation Authority Company (EWSA) is rapidly increasing the number of population having access to electrical power energy. 30% of electrical energy is used in lighting. The inc...The Rwandan State-run Energy Water and Sanitation Authority Company (EWSA) is rapidly increasing the number of population having access to electrical power energy. 30% of electrical energy is used in lighting. The incandescent bulbs, compact fluorescent lamp bulbs as well as fluorescent tubes are mostly used to convert electrical energy into light. The said light sources have many disadvantages such as excessive power consumption leading to giant bills of electricity, short life span leading to continuous replacement of lamps, and emission of CO2. Application of light-emitting diode (LED) lamps in lighting in long term suppresses the aforementioned problems resulting into saving of money that will be used for running new small investments.展开更多
文摘The purpose of this paper is to present a methodology for optimizing the geometry of the LED （light emitting diode） secondary lens. The research objective is to uniform the illumination distribution on a target plane for nonimaging application. In order to achieve this, a software that simulates ray tracing is used, in conjunction with a heuristic process for enhancing the optimized parameters that form the geometry of the LED secondary lens. Spherical lenses was opted for optimization due to its lower manufacture complexity.
文摘The operating circuits for LED （light emitting diode） lamp composed of diodes and DC capacitors only are proposed. The proposed circuit is based on a double-voltage rectifier circuit and a Cockcroft-Walton circuit. The circuit can operate LED without flicker, and is free from switching noise since high frequency switching circuit is not used. To replace an AC capacitor by a DC capacitor for the ballast, a diode is connected across the capacitor in parallel, and the operating voltage of LED unit is kept at the value greater than the peak voltage of the input power source. The circuit realizes high efficiency and high input power factor compared with the operating circuits on the market. Cockcroft-Walton-type circuit can operate many LED devices in series connection. Series connection is preferable for fabricating LED unit of a constant voltage characteristic. Moreover, fairly flat waveform of LED operating current is realized by Cockcrofl-Walton-type circuit, even though capacitor ballast is used.
文摘This paper summarizes different kinds of heat sinks on the market for high power LED lamps. Analysis is made on the thermal model of LED, PCB and heat sink separately with a simplified mode provided. Two examples of simulation are illustrated as a demonstration for the thermal simulation as guidance for LED lamp design.
基金Project supported by the National High Technology Research and Development Program of China(Nos.2015AA03A101,2013AA03A116)the Cuican Project of Chinese Academy of Sciences(No.KZCC-EW-102)the Jilin Province Science and Technology Development Plan Item(No.20130206018GX)
文摘In order to verify which of the distributions and established methods of reliability model are more suitable for the analysis of the accelerated aging of LED lamp, three established methods （approximate method, analytical method and two-stage method） of reliability model are used to analyze the experimental data under the condition of the Weibull distribution and Lognormal distribution, in this paper. Ten LED lamps are selected for the accelerated aging experiment and the luminous fluxes are measured at an accelerated aging temperature. AIC information criterion is adopted in the evaluation of the models. The results show that the accuracies of the analytical method and the two-stage method are higher than that of the approximation method, with the widths of confidence intervals of unknown parameters of the reliability model being the smallest for the two-stage method. In a comparison between the two types of distributions, the accuracies are nearly identical.
基金supported by the National High-Tech R&D Program(863)of China(Nos.2015AA03A101 and 2013AA03A116)the Cui Can Project of Chinese Academy of Sciences(No.KZCC-EW-102)
文摘To acquire a rational minimum cut-off time and the precision of lifetime prediction with respect to cut-off time for the accelerated aging test of LED lamps, fifth-order moving average error estimation is adopted in this paper. Eighteen LED lamps from the same batch are selected for two accelerated aging tests, with 10 samples at 80 ℃ and eight samples at 85 ℃. First, the accelerated lifetime of each lamp is acquired by exponential fitting of the lumen maintenances of the lamp for a certain cut-offtime With the acquired lifetimes of all lamps, the two-parameter Weibull distribution of the failure probability is obtained, and the medium lifetime is calculated. Then, the precision of the medium lifetime prediction for different cut-off times is obtained by moving average error estimation. It is shown that there exists a minimum cut-off time for the accelerated aging test, which can be determined by the variation of the moving average error versus the cut-offtime. When the cut-off time is less than this value, the lifetime estimation is irrational. For a given cut-off time, the precision of lifetime prediction can be computed by average error evaluation, and the error of lifetime estimation decreases gradually as the cut-off time- increases. The minimum cut-off time and medium lifetime of LED lamps are both sensitive to thermal stress. The minimum cut-off time is 1104 h with the lifetime esti- mation error of 1.15% for the test at 80 ~C, and 936 h with the lifetime estimation error of 1.24% for the test at 85 ℃. With the lifetime estimation error of about 0.46%, the median lifetimes are 7310 h and 4598 h for the tests at 80 ℃ and 85℃, respectively.
文摘The Rwandan State-run Energy Water and Sanitation Authority Company (EWSA) is rapidly increasing the number of population having access to electrical power energy. 30% of electrical energy is used in lighting. The incandescent bulbs, compact fluorescent lamp bulbs as well as fluorescent tubes are mostly used to convert electrical energy into light. The said light sources have many disadvantages such as excessive power consumption leading to giant bills of electricity, short life span leading to continuous replacement of lamps, and emission of CO2. Application of light-emitting diode (LED) lamps in lighting in long term suppresses the aforementioned problems resulting into saving of money that will be used for running new small investments.
