[Source: "High-tech LED - Technology and Applications" August issue of Peng Shaoquan]
For the measurement and evaluation of lumen maintenance life of LED lighting products, unlike the measurement of total luminous flux, correlated color temperature, color rendering index and other performance parameters, it can be quickly measured by optical test equipment, and long-term test records are required, and test data is needed. Perform a fitting analysis to estimate the life of the product. This paper studies the requirements of the ENERGY STAR program for LED lighting products and a large number of relevant standard data, and analyzes the current ENERGY STAR specification for the evaluation of lumen maintenance life of monolithic LED lamps and LED lamps, providing research for lumen maintenance life prediction of LED lighting products. reference.
I. Introduction
Since the US Department of Energy released the ENERGY STAR [1] program for solid-state lighting (SSL) products in 2007, few domestic lighting companies have conducted ENERGY STAR testing and certification, which may be considered for various reasons. One of the main reasons is that the ENERGY STAR specification requires a long test time for the lumen maintenance life of monolithic LED lamps and LED lamps. LED lighting technology is changing with each passing day. Many companies are worried about 6,000 hours of lumen maintenance. After the test, new products were launched and the original products were withdrawn from the market.
At present, LED lighting has been greatly improved from light source, driving, to heat dissipation and other key technologies, and has gradually matured. At the same time, the LED lighting standard system of various countries has gradually been established, including the European Union's ErP Directive, the Hong Kong Electrical and Mechanical Services Department's LED Light Energy Efficiency Labeling Scheme, and China's CQC Energy Conservation Certification. Therefore, energy efficiency certification of LED lighting products is imperative. The total luminous flux, correlated color temperature, color rendering index and other performance parameters can be quickly measured by optical test equipment according to IES LM-79-08 [2], while lumen maintenance life has no experimental method to accelerate aging [ 3] It is obviously unrealistic to conduct tens of thousands of hours of long-term experiments. Therefore, it is necessary to have a reasonable evaluation method for lumen maintenance life assessment of LED lamps and lamps.
This paper analyzes the evaluation method of lumen maintenance life of monolithic LED lamps and LED lamps through the study of ENERGY STAR specifications and related IES standards.
Second, the requirements of the Energy Star certification
The ENERGY STAR specification and the IES LM-80-08 et al. [4] standard define the end of life of LED lighting products not like the definition of traditional lighting products, that is, the total igniting time of the product to work, but The lumens of the L70 maintain their lifetime to define their lifetime cessation, ie the total luminescence time at which the total luminous flux of the LED lighting product decays to 70% of its initial total luminous flux. At present, LED lighting products have claimed tens of thousands, even 100,000 hours of lumen maintenance, and the fact is that it is impossible to carry out such long-term life test to prove the life expectancy of the product, and there is no mature accelerated aging test method at present. . Therefore, ENERGY STAR has developed a set of rules for monolithic LED lights and LED luminaires to evaluate the lumen maintenance life standards of products.
Among them, the evaluation of the lumen maintenance life of the integrated LED lamp, Energy Star [5] requirements are: 1) Provide the test report of the IES LM-80-08 using the LED light source, and maintain the lumen of 6000 hours at least 91.8. %; 2) The LED light source used in the LED lamp specifies that the temperature and drive current of the test point cannot be greater than the maximum case temperature and drive current condition in the IES LM-80-08 test report; 3) the lumen maintenance of the LED lamp for 3000 hours is also required Not less than 95.8% (93.1% for decorative lights). The integrated LED lamp meets the above three requirements, and if other performance parameters can also meet the standard, the product can obtain the initial certification of ENERGY STAR, and the ENERGY STAR label can be used in advance. To obtain full certification, a 6000-hour lumen maintenance life test is required, and the lumen maintenance result is also 91.8% (86.7% for decorative lights). Otherwise, the product cannot continue to use the ENERGY STAR label. If the IES LM-80-08 test report for the LED source used is not available, the integrated LED lamp will be ENERGY STAR qualified to complete the 6000-hour lumen maintenance life test and meet the ENERGY STAR specifications.
For the lumen maintenance life assessment of LED luminaires, ENERGY STAR requirements [6], there are also two options, one of which is to meet the requirements of points 1) and 2) of similar integrated LED lights, and The maximum operating temperature of the driver used in the LED luminaire does not exceed the maximum recommended by the driver manufacturer. The test result of item 3) is not required, which can greatly save the ENERGY STAR certification certification cycle. Otherwise, LED lamps must also complete a 6000-hour lumen maintenance life test before applying for Energy Star.
Therefore, if the IES LM-80-08 test report of the LED light source that meets the requirements can be provided, the cycle of the ENERGY STAR detection and certification of the integrated LED lamp and the LED lamp can be greatly shortened.
Third, lumen maintenance life assessment method
Since the lumen maintenance life of LED lighting products depends not only on the lumen maintenance life of the LED light source used, but also on the life of the driver and its internal components, and also on its heat dissipating components, protective structure and the like, and The various factors are related to each other and affect each other. Therefore, the evaluation of the life and reliability of LED lighting products is a complex system engineering. This paper mainly discusses the lumen maintenance life of monolithic LED lamps and LED lamps from two aspects of LED light source and driver.
There are two basic prerequisites for simple and accurate estimation of the lumen maintenance life of monolithic LED lamps and LED lamps. One is to provide the LED source used to measure according to the IES LM-80-08 test method. The lumens maintain the data; the second is to ensure that the LED driver can provide a more stable driving current condition for the LED light source during the rated life of the entire product.
First, it is necessary to confirm whether the LED light source used in the LED lighting product is operating within the range of the maximum forward current and the maximum allowable junction temperature allowed in the specifications provided by the light source manufacturer. For the measurement of the forward current IF, an ammeter can be connected between the driver and the light source of the LED lighting product to measure the forward current through the LED light source in series. For the measurement of the junction temperature Tj of the LED light source, the temperature of the PN junction at this time can be calculated by using the formula (1) by detecting the temperature TS of the LED solder joint when the LED lighting product is stable.
(1)
Among them, RθJ-S is the thermal resistance of the PN junction to the solder joint, and VF is the rated forward voltage of the LED light source. Both of these parameters can be obtained from the specification of the LED light source.
For LED luminaire products, since the driver is external, it can simultaneously monitor the temperature of the case during normal operation to ensure that it does not work at the highest temperature specified by the driver manufacturer to ensure that it provides normal driving conditions for the LED light source. .
Then, the lumen test is maintained from the IES LM-80-08 of the LED source to determine the LED drive current conditions during the test, the temperature range of the burn-in test, and the lumen maintenance at different temperature conditions. According to the IES LM-80-08 standard, the lumen maintenance test method of the LED light source under different shell temperature conditions, the obtained test data can be fitted by the following exponential function of (2), and the LED is calculated at the specified temperature. The lumens at the point in time maintain the situation.
For the measurement and evaluation of lumen maintenance life of LED lighting products, unlike the measurement of total luminous flux, correlated color temperature, color rendering index and other performance parameters, it can be quickly measured by optical test equipment, and long-term test records are required, and test data is needed. Perform a fitting analysis to estimate the life of the product. This paper studies the requirements of the ENERGY STAR program for LED lighting products and a large number of relevant standard data, and analyzes the current ENERGY STAR specification for the evaluation of lumen maintenance life of monolithic LED lamps and LED lamps, providing research for lumen maintenance life prediction of LED lighting products. reference.
I. Introduction
Since the US Department of Energy released the ENERGY STAR [1] program for solid-state lighting (SSL) products in 2007, few domestic lighting companies have conducted ENERGY STAR testing and certification, which may be considered for various reasons. One of the main reasons is that the ENERGY STAR specification requires a long test time for the lumen maintenance life of monolithic LED lamps and LED lamps. LED lighting technology is changing with each passing day. Many companies are worried about 6,000 hours of lumen maintenance. After the test, new products were launched and the original products were withdrawn from the market.
At present, LED lighting has been greatly improved from light source, driving, to heat dissipation and other key technologies, and has gradually matured. At the same time, the LED lighting standard system of various countries has gradually been established, including the European Union's ErP Directive, the Hong Kong Electrical and Mechanical Services Department's LED Light Energy Efficiency Labeling Scheme, and China's CQC Energy Conservation Certification. Therefore, energy efficiency certification of LED lighting products is imperative. The total luminous flux, correlated color temperature, color rendering index and other performance parameters can be quickly measured by optical test equipment according to IES LM-79-08 [2], while lumen maintenance life has no experimental method to accelerate aging [ 3] It is obviously unrealistic to conduct tens of thousands of hours of long-term experiments. Therefore, it is necessary to have a reasonable evaluation method for lumen maintenance life assessment of LED lamps and lamps.
This paper analyzes the evaluation method of lumen maintenance life of monolithic LED lamps and LED lamps through the study of ENERGY STAR specifications and related IES standards.
Second, the requirements of the Energy Star certification
The ENERGY STAR specification and the IES LM-80-08 et al. [4] standard define the end of life of LED lighting products not like the definition of traditional lighting products, that is, the total igniting time of the product to work, but The lumens of the L70 maintain their lifetime to define their lifetime cessation, ie the total luminescence time at which the total luminous flux of the LED lighting product decays to 70% of its initial total luminous flux. At present, LED lighting products have claimed tens of thousands, even 100,000 hours of lumen maintenance, and the fact is that it is impossible to carry out such long-term life test to prove the life expectancy of the product, and there is no mature accelerated aging test method at present. . Therefore, ENERGY STAR has developed a set of rules for monolithic LED lights and LED luminaires to evaluate the lumen maintenance life standards of products.
Among them, the evaluation of the lumen maintenance life of the integrated LED lamp, Energy Star [5] requirements are: 1) Provide the test report of the IES LM-80-08 using the LED light source, and maintain the lumen of 6000 hours at least 91.8. %; 2) The LED light source used in the LED lamp specifies that the temperature and drive current of the test point cannot be greater than the maximum case temperature and drive current condition in the IES LM-80-08 test report; 3) the lumen maintenance of the LED lamp for 3000 hours is also required Not less than 95.8% (93.1% for decorative lights). The integrated LED lamp meets the above three requirements, and if other performance parameters can also meet the standard, the product can obtain the initial certification of ENERGY STAR, and the ENERGY STAR label can be used in advance. To obtain full certification, a 6000-hour lumen maintenance life test is required, and the lumen maintenance result is also 91.8% (86.7% for decorative lights). Otherwise, the product cannot continue to use the ENERGY STAR label. If the IES LM-80-08 test report for the LED source used is not available, the integrated LED lamp will be ENERGY STAR qualified to complete the 6000-hour lumen maintenance life test and meet the ENERGY STAR specifications.
For the lumen maintenance life assessment of LED luminaires, ENERGY STAR requirements [6], there are also two options, one of which is to meet the requirements of points 1) and 2) of similar integrated LED lights, and The maximum operating temperature of the driver used in the LED luminaire does not exceed the maximum recommended by the driver manufacturer. The test result of item 3) is not required, which can greatly save the ENERGY STAR certification certification cycle. Otherwise, LED lamps must also complete a 6000-hour lumen maintenance life test before applying for Energy Star.
Therefore, if the IES LM-80-08 test report of the LED light source that meets the requirements can be provided, the cycle of the ENERGY STAR detection and certification of the integrated LED lamp and the LED lamp can be greatly shortened.
Third, lumen maintenance life assessment method
Since the lumen maintenance life of LED lighting products depends not only on the lumen maintenance life of the LED light source used, but also on the life of the driver and its internal components, and also on its heat dissipating components, protective structure and the like, and The various factors are related to each other and affect each other. Therefore, the evaluation of the life and reliability of LED lighting products is a complex system engineering. This paper mainly discusses the lumen maintenance life of monolithic LED lamps and LED lamps from two aspects of LED light source and driver.
There are two basic prerequisites for simple and accurate estimation of the lumen maintenance life of monolithic LED lamps and LED lamps. One is to provide the LED source used to measure according to the IES LM-80-08 test method. The lumens maintain the data; the second is to ensure that the LED driver can provide a more stable driving current condition for the LED light source during the rated life of the entire product.
First, it is necessary to confirm whether the LED light source used in the LED lighting product is operating within the range of the maximum forward current and the maximum allowable junction temperature allowed in the specifications provided by the light source manufacturer. For the measurement of the forward current IF, an ammeter can be connected between the driver and the light source of the LED lighting product to measure the forward current through the LED light source in series. For the measurement of the junction temperature Tj of the LED light source, the temperature of the PN junction at this time can be calculated by using the formula (1) by detecting the temperature TS of the LED solder joint when the LED lighting product is stable.
(1)
Among them, RθJ-S is the thermal resistance of the PN junction to the solder joint, and VF is the rated forward voltage of the LED light source. Both of these parameters can be obtained from the specification of the LED light source.
For LED luminaire products, since the driver is external, it can simultaneously monitor the temperature of the case during normal operation to ensure that it does not work at the highest temperature specified by the driver manufacturer to ensure that it provides normal driving conditions for the LED light source. .
Then, the lumen test is maintained from the IES LM-80-08 of the LED source to determine the LED drive current conditions during the test, the temperature range of the burn-in test, and the lumen maintenance at different temperature conditions. According to the IES LM-80-08 standard, the lumen maintenance test method of the LED light source under different shell temperature conditions, the obtained test data can be fitted by the following exponential function of (2), and the LED is calculated at the specified temperature. The lumens at the point in time maintain the situation.
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