Cree® XLamp® LED Operating Capacity Table of Contents Introduction and executive summary Introduction and executive summary............................................ 1 This document demonstrates the application of a concept Cree What is LED operating capacity?................................................... 2 calls LED operating capacity, maximizing the utilization of an Design approach/objectives.......................................................... 2 LED rather than driving the LED at its binning current. The design The 6-step methodology................................................................. 3 shows that driving an LED at its designed current capacity 1. Define lighting requirements............................................... 3 2. Define design goals............................................................. 5 3. Estimate efficiencies of the optical, thermal & electrical systems................................................................................ 5 4. Calculate the number of LEDs............................................ 9 5. Consider all design possibilities......................................... 9 6. Complete the final steps: implementation and analysis... 9 www.cree.com/Xlamp Conclusions................................................................................... 16 CLD-AP89 rev 0D Application Note presents options for cost reduction. In today’s LED marketplace, there are many high-power LEDs to choose from for any given lighting project. However, not all LEDs are created equal and special care has to be exercised to create a high-performance, reliable LED lighting product. One key parameter for an LED-based luminaire design is forward driving current, as it determines the lumen output, efficacy, and lifetime of the final luminaire. Copyright © 2012-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree® and XLamp® are registered trademarks and the Cree logo is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product and company names are the property of their respective owners and do not imply specific product and/or vendor endorsement, sponsorship or association. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree Sales at [email protected]. Cree, Inc. 4600 Silicon Drive Durham, NC 27703 USA Tel: +1.919.313.5300 1 XLamp ® LED Operating Capacity What is LED operating capacity? High-power LEDs are binned according to lumen output at a set current level. A single current level is chosen as the binning current and the industry has traditionally used 350 mA. Advancements in LED technology have resulted in LEDs with an operating range up to a maximum LED drive current that may be higher than the binning current. Driving an LED close to the maximum specified drive current can deliver much more light than at the binning current. The potential to drive an LED to what it is capable of is what we call LED operating capacity, the luminous flux produced at the maximum drive current. Figure 1 shows the difference in efficacy between the light output at the binning current and the light output at the maximum drive current. Figure 1 Driving LEDs above the binning current results in more lumens per LED, resulting in fewer LEDs and a lower system cost. Driving LEDs Light Output, Efficacy above the binning current takes advantage of LED operating capacity that is otherwise unused. LED Capacity Binning Current (350 mA) Un-utilized = $$$ capacity LPW Efficacy Light Output Max Drive Current (1500 mA) Input Current (If, mA) Figure 1: Unused LED operating capacity above an LED’s binning current Please note that other factors may play a role in the driving current limit, such as ENERGY STAR® minimum efficacy requirements, system thermal performance and LED L70 lifetime. This reference design demonstrates the LED operating capacity concept in the context of a 6-inch recessed downlight fixture using Cree’s XLamp® XP-G high-power LED. Designed to operate over a wide range of forward drive currents, from 0.35 A to 1.5 A, the XLamp XP-G LED provides ample opportunity to show the benefits of driving an LED well above the binning current. We produced 2 downlight designs. Design 1 uses 12 XP-G LEDs at the LED’s 0.35 A binning current; Design 2 uses 5 LEDs at 1 A. The 5-LED downlight produces light output and light distribution nearly identical to the 12-LED downlight from less than half the number of LEDs. Both downlights meet ENERGY STAR efficacy, correlated color temperature (CCT) and color rendering index (CRI) requirements. Taking advantage of an LED’s operating capacity becomes an attractive option for applications requiring maximum lumen output at a reduced cost. Design approach/objectives In the “LED Luminaire Design Guide”Cree advocates a 6-step framework for creating LED luminaires. All Cree reference designs use this framework, and the design guide’s summary table is reproduced below. Copyright © 2012-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree® and XLamp® are registered trademarks and the Cree logo is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product and company names are the property of their respective owners and do not imply specific product and/or vendor endorsement, sponsorship or association. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree Sales at [email protected]. 2 XLamp ® LED Operating Capacity Table 1: Cree 6-step framework Step Explanation 1. Define lighting requirements • The design goals can be based either on an existing fixture or on the application’s lighting requirements. 2. Define design goals • • Specify design goals, which will be based on the application’s lighting requirements. Specify any other goals that will influence the design, such as special optical or environmental requirements. 3. Estimate efficiencies of the optical, thermal & electrical systems • • • Design goals will place constraints on the optical, thermal and electrical systems. Good estimations of efficiencies of each system can be made based on these constraints. The combination of lighting goals and system efficiencies will drive the number of LEDs needed in the luminaire. 4. Calculate the number of LEDs needed • Based on the design goals and estimated losses, the designer can calculate the number of LEDs to meet the design goals. 5. Consider all design possibilities and choose the best • • With any design, there are many ways to achieve the goals. LED lighting is a new field; assumptions that work for conventional lighting sources may not apply. 6. Complete final steps • • • • • Complete circuit board layout. Test design choices by building a prototype luminaire. Make sure the design achieves all the design goals. Use the prototype to further refine the luminaire design. Record observations and ideas for improvement. The 6-step methodology The goal is to demonstrate applying the concept of LED operating capacity in a 6-inch downlight design. This is best shown by creating a downlight that fulfills real-world requirements. 1. Define lighting requirements Table 2 shows a ranked list of desirable characteristics to address in a downlight reference design. Table 2: Some ranked design criteria for an LED downlight Importance Characteristics Units Price $ Manufacturability Critical Luminous flux (steady-state) lumen (lm) Efficacy lumens per watt (lm/W) Luminous distribution Color uniformity Form factor Important Lifetime hours Operating temperatures °C Operating humidity % relative humidity CCT K CRI 100-point scale Ease of installation Although the prime purpose of this reference design is to demonstrate applying the concept of LED operating capacity, it is useful to show that driving an LED above its binning current need not preclude meeting requirements such as ENERGY STAR. Table 3 and Table 4 summarize the ENERGY STAR requirements for luminaires.1 1 ENERGY STAR® Program Requirements , Product Specification for Luminaires (Light Fixtures), Eligibility Criteria, Version 1.1 Copyright © 2012-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree® and XLamp® are registered trademarks and the Cree logo is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product and company names are the property of their respective owners and do not imply specific product and/or vendor endorsement, sponsorship or association. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree Sales at [email protected]. 3 XLamp ® LED Operating Capacity Table 3: ENERGY STAR luminous efficacy, output and zonal lumen density requirements ENERGY STAR Requirements Luminaire Type Downlights: • recessed • surface • pendant • SSL downlight retrofits Luminaire Efficacy (Initial) Luminaire Minimum Light Output (Initial) 42 lm/W ≤ 4.5” aperture: 345 lumens > 4.5” aperture: 575 lumens Luminaire Zonal Lumen Density Requirement Luminaire shall deliver a minimum of 75% of total initial lumens within the 0-60° zone (axially symmetric about the nadir) Table 4: ENERGY STAR luminaire requirements Characteristic Minimum Goal Light source life requirements: all luminaires The LED package(s) / LED module(s) / LED array(s), including those incorporated into LED light engines or GU24 based integrated LED lamps, shall meet the following L70 lumen maintenance life values (refer to Lumen Maintenance Requirements in the next section): 25,000 hours for residential grade indoor luminaires 35,000 hours for residential grade outdoor luminaires 35,000 hours for commercial grade luminaires Lumen maintenance life projection claims in excess of the above requirements shall be substantiated with a TM-21 lumen maintenance life projection report. Lumen maintenance requirements: directional and non-directional luminaires The LED package(s) / module(s) / array(s), including those incorporated into LED light engines or GU24 based integrated LED lamps, shall meet the following L70(6k) rated lumen maintenance life values, in situ: • • L70(6k) ≥ 25,000 hours for residential indoor L70(6k) ≥ 35,000 hours for residential outdoor, or commercial Compliance with the above shall be documented with a TM-21 lumen maintenance life projection report as detailed in TM-21, section 7. The report shall be generated using data from the LM-80 test report for the employed LED package/ module/array model (“device”), the forward drive current applied to each device, and the in situ TMPLED temperature of the hottest LED in the luminaire. In addition to LM-80 reporting requirements, the following information shall be reported: • • • • • • sampling method and sample size (per LM-80 section 4.3) test results for each TS and drive current combination description of device including model number and whether device is an LED package, module or array (see Definitions) ANSI target, and calculated CCT value(s) for each device in sample set Δ u’v’ chromaticity shift value on the CIE 1976 diagram for each device in sample set a detailed rationale, with supporting data, for application of results to other devices (e.g. LED packages with other CCTs) Access to the TMPLED for the hottest LED may be accomplished via a minimally sized hole in the luminaire housing, tightly resealed with a suitable sealant if created for purposes of testing. All thermocouple attachments and intrusions to luminaire housing shall be photographed. CCT requirements: all indoor luminaires The luminaire (directional luminaires), or replaceable LED light engine or GU24 based integrated LED lamp (nondirectional luminaires) shall have one of the following nominal CCTs: • • • • • 2700 Kelvin 3000 Kelvin 3500 Kelvin 4000 Kelvin 5000 Kelvin (commercial only) The luminaire, LED light engine or GU24 based integrated LED lamp shall also fall within the corresponding 7-step chromaticity quadrangles as defined in ANSI/NEMA/ANSLG C78.377-2008. Color rendering requirements: all indoor luminaires The luminaire (directional luminaires), or replaceable LED light engine or GU24 based integrated LED lamp (nondirectional luminaires) shall meet or exceed Ra ≥ 80. Color angular uniformity requirements: directional solid state indoor luminaires Throughout the zonal lumen density angles detailed above, and five degrees beyond, the variation of chromaticity shall be within 0.004 from the weighted average point on the CIE 1976 (u’,v’) diagram. Copyright © 2012-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree® and XLamp® are registered trademarks and the Cree logo is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product and company names are the property of their respective owners and do not imply specific product and/or vendor endorsement, sponsorship or association. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree Sales at [email protected]. 4 XLamp ® LED Operating Capacity Characteristic Minimum Goal Color maintenance requirements: solid state indoor luminaires only The change of chromaticity over the first 6,000 hours of luminaire operation shall be within 0.007 on the CIE 1976 (u’,v’) diagram, as demonstrated by either: • • • the IES LM-80 test report for the employed LED package/array/module model, or as demonstrated by a comparison of luminaire chromaticity data in LM-79 reports at zero and 6,000 hours, or as demonstrated by a comparison of LED light engine or GU24 based integrated LED lamp chromaticity data in LM-82 reports at zero and 6,000 hours. Source start time requirement: directional and nondirectional luminaires Light source shall remain continuously illuminated within one second of application of electrical power. Source run-up time requirements: directional and non-directional luminaires Light source shall reach 90% of stabilized lumen output within one minute of application of electrical power. Power factor requirements: directional and nondirectional luminaires Total luminaire input power less than or equal to 5 watts: PF ≥ 0.5 Transient protection requirements: all luminaires Ballast or driver shall comply with ANSI/IEEE C62.41.1-2002 and ANSI/IEEE C62.41.2-2002, Class A operation. The line transient shall consist of seven strikes of a 100 kHz ring wave, 2.5 kV level, for both common mode and differential mode. Operating frequency requirements: directional and non-directional luminaires Frequency ≥ 120 Hz Noise requirements: directional and non-directional luminaires All ballasts & drivers used within the luminaire shall have a Class A sound rating. Electromagnetic and radio frequency interference requirements: directional and non-directional luminaires Power supplies and/or drivers shall meet FCC requirements: Total luminaire input power greater than 5 watts: Residential: PF ≥ 0.7 Commercial: PF ≥ 0.9 Note: This performance characteristic addresses problems with visible flicker due to low frequency operation and applies to steady-state as well as dimmed operation. Dimming operation shall meet the requirement at all light output levels. Ballasts and drivers are recommended to be installed in the luminaire in such a way that in operation, the luminaire will not emit sound exceeding a measured level of 24 dBA. • • Class A for power supplies or drivers that are marketed for use in a commercial, industrial or business environment, exclusive of a device which is marketed for use by the general public or is intended to be used in the home. Class B for power supplies or drivers that are marketed for use in a residential environment notwithstanding use in commercial, business and industrial environments. 2. Define design goals The design goals for this project are given in Table 5. Table 5: Design goals Characteristic Light output Unit Minimum Goal Target Goal lm 900 > 900 Luminous distribution Power Both fixtures identical W 20 < 20 Luminaire efficacy lm/W 45 55 Lifetime hours 35,000 35,000 K 3000 3000 80 > 80 0.9 > 0.9 30 40 CCT CRI Power factor Max ambient temperature °C 3. Estimate efficiencies of the optical, thermal & electrical systems We used Cree’s Product Characterization Tool (PCT) tool to determine the drive current for each design. Copyright © 2012-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree® and XLamp® are registered trademarks and the Cree logo is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product and company names are the property of their respective owners and do not imply specific product and/or vendor endorsement, sponsorship or association. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree Sales at [email protected]. 5 XLamp ® LED Operating Capacity For the 900-lumen target, we used a typical 85% optical efficiency and 83% driver efficiency. We also estimated solder point temperatures of 65 °C and 75 °C for the two Compare: designs.SYS lm tot 13 SYS # LED11 SYS W Target Lumens : System: Current Display Range: 12 SYS lm/W 15 Optical Efficiency: 900 Q5 [107] 6 SYS lm tot SYS # LED 0.100 0.150 0.200 0.250 0.300 0.350 0.400 0.450 0.500 0.550 0.600 0.650 0.700 0.750 0.800 0.850 0.900 0.950 1.000 1.100 1.200 1.300 900.4 909.5 914.9 954.5 921.4 900.4 925.3 926.7 904.9 984 928.3 993.5 906.1 959 1010.1 1059.9 923.3 962.2 999.6 1070.7 909.2 958.1 Price $ - 107.0 Tsp (ºC) 2.0 LED Multiple 37 25 19 16 13 11 10 9 8 8 7 7 6 6 6 6 5 5 5 5 4 4 SYS W 11.96 12.32 12.68 13.54 13.39 13.4 14.1 14.45 14.44 16.05 15.48 16.94 15.78 17.06 18.34 19.64 17.46 18.55 19.65 21.86 19.26 21.03 83% LED 2 Model Cree XLamp 25XP-G {CW/NW/WW} Current (A) Flux 3 Electrical Efficiency: 85% LED 1 Model Medium (0.1A - 2.0A) 65 x1 LED 3 Model Cree XLamp 25XP-G {CW/NW/WW} Flux Q5 [107] Price $ 1 6 - SYS lm/W SYS lm tot SYS # LED 75.3 73.8 72.2 70.5 68.8 67.2 65.6 64.1 62.7 61.3 60 58.7 57.4 56.2 55.1 54 52.9 51.9 50.9 49 47.2 45.6 906.3 926.9 943.8 935.4 902.9 962.4 906.7 908 997.5 964 909.4 973.3 1035.5 939.4 989.5 1038.2 904.3 942.4 978.9 1048.6 1112.9 938.1 38 26 20 16 13 12 10 9 9 8 7 7 7 6 6 6 5 5 5 5 5 4 Flux 107.0 Tsp (ºC) 2.0 LED Multiple SYS W 12.19 12.72 13.25 13.45 13.3 14.51 14 14.35 16.13 15.95 15.38 16.83 18.29 16.95 18.23 19.52 17.35 18.44 19.53 21.73 23.93 20.9 Price 73 x1 1 (none) 1 $ 1 LED Multiple SYS lm/W 74.4 72.9 71.2 69.6 67.9 66.3 64.8 63.3 61.8 60.5 59.1 57.8 56.6 55.4 54.3 53.2 52.1 51.1 50.1 48.3 46.5 44.9 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A Figure 2: PCT view of the number of LEDs used and driving current The PCT yields the following results: Design 1: At 350 mA, it appears that 11 LEDs are sufficient, but the light output barely meets the goal and, to be safe, we chose to use 12 LEDs. Design 2: Five LEDs can achieve 900 lm at 900 mA; however, this requires a custom-made driver. Because the driver can be placed external to the downlight and does not have a space constraint, we chose to use an off-the-shelf driver at 1 A instead. Thermal Requirements The 6-inch downlight in this reference design is of a simple geometry and we decided to make a custom aluminum housing, shown in Figure 3. We decided to use a commercially available heat sink, shown in Figure 4, attached to the back of the housing to dissipate the thermal load.2 2 AAVID Thermalloy Part number 637303B03000 Copyright © 2012-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree® and XLamp® are registered trademarks and the Cree logo is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product and company names are the property of their respective owners and do not imply specific product and/or vendor endorsement, sponsorship or association. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree Sales at [email protected]. 6 XLamp ® LED Operating Capacity Figure Figure 5 5 Figure 3: Custom-made aluminum housing Figure 4: Heat sink We performed thermal simulations of both luminaire designs to ensure this thermal design is sufficient. We assumed that ~75% of the input power is converted to heat and the rest to light. We included the 6-inch can and a ceiling in the simulation to mimic a real-life application condition. Figure 5 shows the thermal simulation results for the 12-LED design at 350 mA. The simulated TSP is 55 °C. Figure 5: Thermal simulation of 12-LED downlight (left) and downlight mounted in ceiling (right) Figure 6 shows the thermal simulation results for the 5-LED design at 1000 mA. The simulated TSP is 73 °C. Copyright © 2012-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree® and XLamp® are registered trademarks and the Cree logo is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product and company names are the property of their respective owners and do not imply specific product and/or vendor endorsement, sponsorship or association. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree Sales at [email protected]. 7 XLamp ® LED Operating Capacity Figure 6: Thermal simulation of 5-LED downlight (left) and downlight mounted in ceiling (right) Driver Because the driver for a 6-inch downlight can be located next to the housing above the ceiling, there is no driver size limit. Thus there is no need to design a custom driver for this reference design. We decided to use off-the-shelf drivers from Thomas Research.3 Both drivers are standard current-type devices with ~87% efficiency. 350-mA driver for 12-LED downlight 1000-mA driver for 5-LED downlight Figure 7: Drivers Secondary Optics In a multiple-LED lighting system, a diffuser is a popular secondary optic used to minimize glare and hot spots and to distribute light evenly. In many cases, a white reflector is used between the LED and the diffuser to form a recycling cavity to maximize light output. In this reference design, we tried a number of combinations of reflectors and diffusers and found that a white reflective paper, a diffuser from 3 350 mA driver part number LED20W-24-C0700, 1000 mA driver part number LED25W-24-C1040 Copyright © 2012-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree® and XLamp® are registered trademarks and the Cree logo is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product and company names are the property of their respective owners and do not imply specific product and/or vendor endorsement, sponsorship or association. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree Sales at [email protected]. 8 XLamp ® LED Operating Capacity Bright View Technologies,4 and a commercial downlight trim kit from Halo to hold everything together to form a successful secondary optic for this design. Figure 8: Diffuser lens 4. Calculate the number of LEDs Design 1 uses 12 XP-G LEDs from the Q5 luminous flux group driven at 350 mA each. Design 2 uses 5 XP-G LEDs from the Q5 luminous flux group driven at 1000 mA each. 5. Consider all design possibilities Using the methodology described above, we determined a suitable combination of LEDs, components and drive conditions. This section describes how Cree assembled the downlights and compares the results of the two designs. 6. Complete the final steps: implementation and analysis This section illustrates some of the techniques used to create a working prototype downlight using the XLamp XP-G LED. Prototyping Details 1. We verified the component dimensions to ensure a correct fit. 2. Following the recommendations in Cree’s Soldering and Handling Application Note for the XP-G LED, we reflow soldered the LEDs onto the metal core printed circuit board (MCPCB) with an appropriate solder paste type and reflow profile. We cleaned the flux residue with isopropyl alcohol (IPA). 3. We soldered the driver input wires to the MCPCB. We tested the connection by applying power to the LEDs to verify that they lit. 4. We applied a thin layer of thermal conductive compound to the back of the MCPCB and secured the MCPCB to the aluminum housing with screws. 4 Part number P001 Copyright © 2012-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree® and XLamp® are registered trademarks and the Cree logo is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product and company names are the property of their respective owners and do not imply specific product and/or vendor endorsement, sponsorship or association. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree Sales at [email protected]. 9 XLamp ® LED Operating Capacity 5. We applied a thin layer of thermal conductive compound to the back of aluminum housing and secured the finned heat sink with screws. 6. We secured the white reflective paper to the MCPCB with double-sided tape. 7. We secured the diffuser cover trim to the aluminum housing. 8. We connected the LED DC input wires to the driver DC output wires with connectors. 9. We performed final testing. Figure Figure 9 9 Results We compare 2 downlight designs with different numbers of LEDs running at different currents to achieve the same lumen output. The results show that driving an LED to its operating capacity allows designers to lower cost while retaining performance and reliability. Thermal Results Cree verified the board temperature with a thermocouple and an infrared (IR) thermal imaging camera to confirm that the thermal dissipation performance of the heat sink aligns with our simulations. The solder point temperature of the 12-LED downlight was 52 °C. The solder point temperature of the 5-LED downlight was 74 °C. Both results are in close agreement with the simulations and show that the heat sink is sufficient for this design. Figure 9: Thermal results for 12-LED (left) and 5-LED (right) XP-G downlights Copyright © 2012-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree® and XLamp® are registered trademarks and the Cree logo is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product and company names are the property of their respective owners and do not imply specific product and/or vendor endorsement, sponsorship or association. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree Sales at [email protected]. 10 XLamp ® LED Operating Capacity Estimated LED lifetime We used Cree’s TM-21 Calculator Tool to project the lifetime of the XP-G LED used in this downlight. Figure 10 shows the calculated TM-21 Lifetime Report and reported lifetimes, determined using the TM-21 projection algorithm, for the XP-G LED at 500-mA input current at 3 solder-point temperatures. LED I Data Set Tsp Sample Size Test Duration α β Calculated Lifetime Reported Lifetime 7 45°C 25 10,080 hrs -1.322E-06 1.005E+00 α<0; see Reported Lifetime L70(10k) > 60,500 hours XLamp XP-G White 500 mA 8 55°C 25 10,080 hrs 3.963E-07 1.006E+00 L70(10k) = 914,000 hours L70(10k) > 60,500 hours 9 85°C 25 10,080 hrs -1.060E-06 9.996E-01 α<0; see Reported Lifetime L70(10k) > 60,500 hours Reported L70 Calculated Lifetim Reported Lifetime 110 105 100 95 % Luminous Flux 90 85 45°C (LM-80) 80 55°C (LM-80) 85°C (LM-80) 75 45°C (TM-21) 70 55°C (TM-21) 65 85°C (TM-21) 60 55 50 1,000 10,000 100,000 1,000,000 Time (hours) Figure 10: XP-G TM-21 data at 500 mA This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarks of Cree, Inc. Copyright © 2012-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree® and XLamp® are registered trademarks and the Cree logo is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product and company names are the property of their respective owners and do not imply specific product and/or vendor endorsement, sponsorship or association. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree Sales at [email protected]. 11 XLamp ® LED Operating Capacity Figure 11 shows the calculated and reported lifetimes for the XP-G LED, interpolated from the data shown in Figure 10, at the measured 52 °C TSP of the 12-LED lamp, but with a drive current of 500 mA, higher than the 350 mA used in the reference design. With a reported Lifetime Report L70(10k) lifetime greater than 60,500 hours and a calculated L70(10k) lifetime ofTM-21 914,000 hours, we expect the 12-LED downlight to easily meet the ENERGY STAR lifetime requirement. XLamp XP-G White 500 mA Tsi (Interpolated) LED I Ts1 Tsp Tsp Ea/kB A α β Calculated L70 Reported L70 Calculated Lifetime Reported Lifetime Ts2 45°C 52°C 55°C 318.15 K 325.15 K N/A N/A N/A N/A L70(10k) = 914,000 hours L70(10k) > 60,500 hours L70(10k) = 914,000 hours L70(10k) > 60,500 hours 328.15 K -1.322E-06 1.005E+00 α<0; see Reported Lifetime L70(10k) > 60,500 hours 3.963E-07 1.006E+00 L70(10k) = 914,000 hours L70(10k) > 60,500 hours 110 105 100 95 85 45°C (LM-80) 80 55°C (LM-80) 75 85°C (LM-80) 70 45°C (TM-21) 65 55°C (TM-21) 60 85°C (TM-21) 55 52°C (LM-80) 50 1,000 10,000 100,000 L70: 914,000 hrs % Luminous Flux 90 1,000,000 Time (hours) Figure 11: TM-21 report for XP-G at 500 mA at 52 °C TSP This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarks of Cree, Inc. Copyright © 2012-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree® and XLamp® are registered trademarks and the Cree logo is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product and company names are the property of their respective owners and do not imply specific product and/or vendor endorsement, sponsorship or association. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree Sales at [email protected]. 12 XLamp ® LED Operating Capacity TM-21 Lifetime Report Figure 12 shows the calculated and reported lifetimes, determined using the TM-21 projection algorithm, for the XP-G LED at 1000 mA input current at 3 solder point temperatures. LED I Data Set Tsp Sample Size Test Duration α β Calculated Lifetime Reported Lifetime 10 55°C 20 10,080 hrs -4.219E-06 9.847E-01 α<0; see Reported Lifetime L70(10k) > 60,500 hours XLamp XP-G White 1000 mA 11 85°C 20 10,080 hrs 1.284E-06 1.016E+00 L70(10k) = 290,000 hours L70(10k) > 60,500 hours 12 105°C 20 6,048 hrs 5.561E-06 1.007E+00 L70(6k) = 65,500 hours L70(6k) > 36,300 hours 110 105 100 95 % Luminous Flux 90 85 55°C (LM-80) 80 85°C (LM-80) 105°C (LM-80) 75 55°C (TM-21) 70 85°C (TM-21) 65 105°C (TM-21) 60 55 50 1,000 10,000 100,000 1,000,000 Time (hours) Figure 12: XP-G TM-21 data at 1000 mA This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarks of Cree, Inc. Copyright © 2012-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree® and XLamp® are registered trademarks and the Cree logo is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product and company names are the property of their respective owners and do not imply specific product and/or vendor endorsement, sponsorship or association. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree Sales at [email protected]. 13 XLamp ® LED Operating Capacity Figure 13 shows the calculated and reported lifetimes for the XP-G LED, interpolated from the data shown in Figure 10, at the measured TM-21 Lifetime Report 74 °C TSP of the 5-LED lamp. With a reported L70(10k) lifetime greater than 60,500 hours and a calculated L70(10k) lifetime of 290,000 hours, we expect the 5-LED downlight to also easily meet the ENERGY STAR lifetime requirement. Ts1 XLamp XP-G White 1000 mA Tsi (Interpolated) Ts2 55°C 74°C 85°C 328.15 K 347.15 K N/A N/A N/A N/A L70(10k) = 290,000 hours L70(10k) > 60,500 hours L70(10k) = 290,000 hours L70(10k) > 60,500 hours 358.15 K LED I Tsp Tsp Ea/kB A α β Calculated L70 Reported L70 Calculated Lifetime Reported Lifetime -4.219E-06 9.847E-01 α<0; see Reported Lifetime L70(10k) > 60,500 hours 1.284E-06 1.016E+00 L70(10k) = 290,000 hours L70(10k) > 60,500 hours 110 55°C (LM-80) 105 85°C (LM-80) 100 105°C (LM-80) 95 55°C (TM-21) % Luminous Flux 90 85°C (TM-21) 85 105°C (TM-21) 80 74°C (LM-80) 75 L70: 290,000 hrs 70 65 60 55 50 1,000 10,000 100,000 1,000,000 Time (hours) Figure 13: TM-21 report for XP-G at 1000 mA at 74 °C TSP This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. Copyright © 2011 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo and XLamp are registered trademarks of Cree, Inc. Copyright © 2012-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree® and XLamp® are registered trademarks and the Cree logo is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product and company names are the property of their respective owners and do not imply specific product and/or vendor endorsement, sponsorship or association. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree Sales at [email protected]. 14 XLamp ® LED Operating Capacity Optical and Electrical Results We tested the two prototype downlight designs in a two-meter sphere for 30 minutes to obtain the results in Table 6.5 As the table shows, both designs meet the 900 lm target for the design. Both designs also meet the ENERGY STAR efficacy and CRI requirements. The 12-LED design uses about 25% less power and produces about 15 lm/W more than the 5-LED design. However, the 5-LED design uses less than half the number of LEDs, which offers a significant savings. Note than the lifetime values are for the XP-G LED and do not reflect for the lifetime of the other components of the downlights. Table 6: 12-LED and 5-LED XP-G downlight comparison Characteristic Unit 12-LED Downlight Light output (30 min on time) lm 943 930 Current mA 350 1000 Power 5-LED Downlight W 14.5 19.2 lm/W 65.0 48.4 K 3000 3020 L70(10k) reported lifetime hours > 60,500 @ 500 mA > 60,500 @ 1000 mA L70(10k) calculated lifetime hours 914,000 @ 500 mA 290,000 @ 1000 mA 80.6 80.2 Efficacy CCT CRI TSP °C 52 74 TJ (calculated) °C 57 89 We also tested the intensity distribution of the 2 designs. Figure 14 shows that the intensity distribution of the 2 downlights is very similar. The 5-LED downlight has almost exactly the same intensity distribution as the 12-LED downlight using 60% fewer LEDs. The diffuser distributes the light evenly despite the difference in LED numbers and location. 5 Testing was performed at the Cree facilities in Santa Barbara, CA. Copyright © 2012-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree® and XLamp® are registered trademarks and the Cree logo is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product and company names are the property of their respective owners and do not imply specific product and/or vendor endorsement, sponsorship or association. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree Sales at [email protected]. 15 Figure 14 XLamp ® LED Operating Capacity 175 170 165 600 160 155 150 145 500 140 135 130 400 125 120 300 115 110 200 105 100 100 95 90 0 85 80 75 70 65 60 55 50 45 40 35 30 2520 1510 5 180 0 12-LED downlight 12 pcs XPG 175 170 55-LED pcs XPG downlight 165 160 155 150 145 140 135 130 125 120 115 110 105 100 95 90 85 80 75 70 65 60 55 50 45 40 35 30 2025 15 5 10 Figure 14: Angular luminous intensity distribution of 12-LED and 5-LED XP-G downlights Conclusions This reference design demonstrates the LED operating capacity concept by applying it to a 6-inch downlight design using Cree XLamp XP-G high-power LEDs. The 5-LED downlight matches the light output of the 12-LED downlight using 60% fewer LEDs. Both downlights deliver the target lumen output and efficacy. With the XP-G LED’s maximum drive current of 1.5 A, even this reference design leaves some LED operating capacity unused. Even higher drive currents provide opportunities for additional light output and reduction in the number of LEDs used. Any lighting design must balance numerous factors including efficiency, thermal management, chromaticity and long-term reliability,6 and the application of the LED operating capacity concept gives lighting designers and engineers the option of using fewer LEDs, thereby reducing cost without sacrificing performance or reliability. 6 For additional information on operating XLamp LEDs at or above the maximum drive current, see the Pulsed Over-Current Driving of XLamp LEDs: Information and Cautions Application Note Copyright © 2012-2016 Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree® and XLamp® are registered trademarks and the Cree logo is a trademark of Cree, Inc. ENERGY STAR® is a registered trademark of the U.S. Environmental Protection Agency. Other trademarks, product and company names are the property of their respective owners and do not imply specific product and/or vendor endorsement, sponsorship or association. This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at www.cree.com. For warranty information, please contact Cree Sales at [email protected]. 16