Cree XLamp XM-L LED 6-Inch Downlight Reference Design

Transcription

1 Cree XLamp XM-L LED 6-Inch Downlight Reference Design Application Note CLD-AP93 rev 0C Table of Contents Introduction...1 Design approach/objectives...2 The 6-step methodology Define lighting requirements Define design goals Estimate efficiencies of the optical, thermal & electrical systems Calculate the number of LEDs Consider all design possibilities Complete the final steps...8 Conclusion...14 Bill of materials...15 Introduction This application note details the design of a 6-inch downlight using Cree s XLamp XM-L LED, a single die, high-flux component optimized for very high-lumen applications such as indoor commercial, high-bay and roadway lights. The XM-L offers industry-leading performance and reliability. Six-inch downlights are the industry standard indoors and outdoors in both residential and commercial applications such as soffits and ceilings, where a wide beam pattern is desirable. Although typical light output ranges from 500 to 2000 lumens, high-ceiling applications require even higher light levels. The high flux and efficacy offered by the XLamp XM-L LED make it a strong candidate for use in such a 6-inch downlight. Reliance on any of the information provided in this Application Note is at the user s sole risk. Cree and its affiliates make no warranties or representations about, nor assume any liability with respect to, the information in this document or any LED-based lamp or luminaire made in accordance with this reference design, including without limitation that the lamps or will not infringe the intellectual property rights of Cree or a third party. Luminaire manufacturers who base product designs in whole or part on any Cree Application Note or Reference Design are solely responsible for the compliance of their products with all applicable laws and industry requirements. Copyright 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. For product specifications, please see the data sheets available at For warranty information, please contact Cree Sales at sales@cree.com. Cree, Inc Silicon Drive Durham, NC USA Tel:

2 Design approach/objectives In the LED Luminaire Design Guide Cree advocates a 6-step framework for creating LED. All Cree reference designs use this framework, and the design guide s summary table is reproduced below. Step Table 1: Cree 6-step framework 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 of the design is an LED-based downlight that shows the performance available from the XLamp XM-L LED. 1. Define lighting requirements Table 2shows 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 Critical Important Luminous flux (steady-state) lumens (lm) Efficacy lumens per watt (lm/w) Luminous distribution Color uniformity Form factor Price $ Lifetime hours Operating temperatures C Operating humidity % relative humidity CCT K CRI 100-point scale Manufacturability Ease of installation Cree Sales at sales@cree.com. 2

3 Table 3 and Table 4 summarize the ENERGY STAR requirements for. 1 Table 3: ENERGY STAR luminous efficacy, output and zonal lumen-density 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 ENERGY STAR REQUIREMENTS 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 Light source life requirements: all Requirements 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 35,000 hours for residential grade outdoor 35,000 hours for commercial grade 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 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 TMP LED 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 TMP LED 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 The luminaire (directional ), or replaceable LED light engine or GU24 based integrated LED lamp (non-directional ) 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 C Color rendering requirements: all indoor Color angular uniformity requirements: directional solid state indoor The luminaire (directional ), or replaceable LED light engine or GU24 based integrated LED lamp (non-directional ) shall meet or exceed Ra 80. Throughout the zonal lumen density angles detailed above, and five degrees beyond, the variation of chromaticity shall be within from the weighted average point on the CIE 1976 (u,v ) diagram. 1 ENERGY STAR Program Requirements, Product Specification for Luminaires (Light Fixtures), Eligibility Criteria, Version 1.1 Cree Sales at sales@cree.com. 3

4 Characteristic Color maintenance requirements: solid state indoor only Requirements The change of chromaticity over the first 6,000 hours of luminaire operation shall be within 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 non-directional Source run-up time requirements: directional and non-directional Power factor requirements: directional and non-directional Transient protection requirements: all Light source shall remain continuously illuminated within one second of application of electrical power. Light source shall reach 90% of stabilized lumen output within one minute of application of electrical power. Total luminaire input power less than or equal to 5 watts: PF 0.5 Total luminaire input power greater than 5 watts: Residential: PF 0.7 Commercial: PF 0.9 Ballast or driver shall comply with ANSI/IEEE C and ANSI/IEEE C , 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 Noise requirements: directional and non-directional Electromagnetic and radio frequency interference requirements: directional and non-directional Frequency 120 Hz Note: This performance characteristic addresses problems with visible flicker due to low frequency operation and applies to steadystate as well as dimmed operation. Dimming operation shall meet the requirement at all light output levels. All ballasts & drivers used within the luminaire shall have a Class A sound rating. 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 BA. Power supplies and/or drivers shall meet FCC requirements: 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 Table 5 shows the design goals for this project. Table 5: Design goals Characteristic Unit Minimum Goal Target Goal Light output lm 3000 > 3000 Power W 50 < 50 Luminaire efficacy lm/w Lifetime hours 50,000 50,000 CCT K CRI 100-point scale 80 > 80 Power factor % 90 > Estimate efficiencies of the optical, thermal & electrical systems We used Cree s Product Characterization Tool (PCT) tool to determine the drive current for the design. For the 3000-lumen target, we estimated 92% optical efficiency and 85% driver efficiency. We also estimated a solder point temperature of 55 C. Cree Sales at sales@cree.com. 4

5 This document is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data Copyright Cree, Inc. All rights reserved. The information in this document is subject to change without notice. Cree, the Cree logo a Figure 1: PCT view of the number of LEDs used and driving current The PCT shows that, at 1.7 A, 8 XM-L LEDs provide sufficient light output to meet the design goals. Thermal Requirements LED System Comparison Rep 1 System: Target Lumens : 3,000 Optical Efficiency: 90 LED 1 LED 2 Model Cree XLamp XM-L {CW/NW/WW} Model (none) Flux T3 [220] Tsp (ºC) 55 Flux Tj (ºC) 2 Price $ - Price $ - SYS lm tot SYS # LED SYS lm/w SYS W #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 #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 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A Current (A) For the 6-inch downlight in this reference design, we decided to use a commercially available housing, shown in Figure 2. We also decided to use a commercially available heat sink, shown in Figure 3, attached to the back of the housing to dissipate the thermal load. Cree Sales at sales@cree.com. 5

6 Figure 2: Housing Figure 4 Figure 3: Heat sink We performed thermal simulations to verify this thermal design is sufficient. Figure 4 shows the thermal simulation results for the design. The simulated solder point temperature (T SP ) was determined to be 51 C. Figure 4: Thermal simulation of XM-L downlight Driver The driver for this 6-inch downlight can be mounted separate from the downlight and there is no driver size limit. This reference design does not require a custom driver and we decided to use a constant-current off-the-shelf driver. Figure 5: Driver Cree Sales at sales@cree.com. 6

7 Secondary Optics A diffuser is commonly used in downlight designs to minimize glare and hot spots and to distribute light evenly. This downlight design uses a diffuser and a reflector to maximize light output. These two optical elements are contained in the housing. Figure 6: Diffuser lens Figure 7: Reflector The reflector efficiency is ~99% and the diffuser efficiency is ~89%, giving a total optical efficiency of ~90%. 4. Calculate the number of LEDs Using Cree s PCT, we determined that 8 XLamp XM-L LEDs produce sufficient light to meet the 3000-lm design goal. 5. Consider all design possibilities There are many ways to design an LED-based downlight. This reference design aims to show that a small number of XM-L LEDs enable a downlight offering superior performance. The XM-L LED offers a wide range of color temperatures. As highlighted in Table 6, we selected a warm white LED for this downlight design. By selecting an LED from a low-level flux bin, we ensured that this design meets its goals using an LED that is readily available. Table 6: XM-L order codes Color CCT Range Base Order Codes Min. Luminous 700 ma (lm) Min. Max. Group Flux (lm) Order Code Cool White 5,000 K 8,300 K Neutral White 3,700 K 5,000 K 80-CRI White 2,600 K 4,300 K Warm White 2,600 K 3,700 K T5 260 XMLAWT T5051 T6 280 XMLAWT T6051 T4 240 XMLAWT LT40E4 T5 260 XMLAWT LT50F4 T2 200 XMLAWT HT20E7 T3 220 XMLAWT HT30F7 T2 200 XMLAWT LT20E7 T3 220 XMLAWT LT30F7 Cree Sales at sales@cree.com. 7

8 6. Complete the final steps Using the methodology described above, we determined a suitable combination of LEDs, components and drive conditions. This section describes how Cree assembled the downlight and shows the results of the design. 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 XM-L LED with an appropriate solder paste and reflow profile, we reflow soldered the LEDs to the metal core printed circuit board (MCPCB). 3. We soldered the input wires to the MCPCB. 4. We tested the connection by applying power to the LEDs and verified the LEDs lit up. 5. We applied a thin layer of thermal conductive compound to the back of MCPCB and attached it to the heat sink. 6. We attached a round white reflector (with cutout openings matching the LEDs) to the MCPCB, securing it with screws. Cree Sales at sales@cree.com. 8

9 7. We attached the housing to the heat sink with screws. 8. We attached the reflector to the bottom of the housing with screws. We attached the reflector to the sides of the housing with double-sided tape. 9. We fit the diffuser lens into the housing and secured it with the diffuser cover trim. 10. We connected the LED DC input wires to the driver DC output wires with connectors. 11. We performed final testing. Cree Sales at 9

10 Results 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. As shown in Figure 8, the measured solder point temperature was 53 C, which is in close agreement with the simulation and shows that the heat sink is sufficient for this design. Based on the measured solder point temperature of 53 C, the junction temperature (T J ) can be calculated as follows: T J = T SP + (LED power * LED thermal resistance) T J = 53 C + (5.3 W * 2.5 C/W) T J = 66 C Figure 8: Thermal results for XM-L downlight Estimated LED Lifetime We used Cree s TM-21 Calculator Tool to project the lifetime of the XM-L LED used in this downlight. Figure 9 shows the calculated and reported lifetimes, determined using the TM-21 projection algorithm, for the XM-L LED at a 2-A input current at three solder point temperatures. The duration of Cree s XM-L LM-80 data set is 6000 hours at a 2-A drive current. Because the TM-21 methodology limits the projection to six times the duration of the LM-80 data set, our TM-21 calculation shows a lifetime L70(6k) projection of greater than 36,300 hours. We are confident that most drivers can meet this temperature/lifetime requirement as well. Cree Sales at sales@cree.com

11 TM-21 Lifetime Report LED I XLamp XM-L White 2000 ma Data Set Tsp 45 C 55 C 85 C Sample Size Test Duration 6,048 hrs 6,048 hrs 6,048 hrs α 1.459E E E-06 β 9.847E E E-01 Calculated Lifetime L70(6k) = 2,340,000 hours L70(6k) = 362,000 hours L70(6k) = 158,000 hours Reported Lifetime L70(6k) > 36,300 hours L70(6k) > 36,300 hours L70(6k) > 36,300 hours Reported L70 Calculated Lifetim Reported Lifetime % Luminous Flux ,000 10, ,000 1,000,000 10,000,000 Time (hours) Figure 9: XM-L TM-21 data 45 C (LM-80) 55 C (LM-80) 85 C (LM-80) 45 C (TM-21) 55 C (TM-21) 85 C (TM-21) Figure 10 shows This document the calculated is provided for and informational reported purposes lifetimes only for and the is not XM-L a warranty LED, interpolated or a specification. from For the product data specifications, shown in please Figure see 9, the at a measured data sheets available at 53 C T SP. With Copyright a reported 2011 L70(6k) Cree, Inc. lifetime All rights reserved. greater than The information 36,300 hours, in this document we expect is subject the lamp to change to easily without meet notice. the Cree, design s the Cree lifetime logo and requirement. XLamp are registered trademarks of Cree, Inc. Cree Sales at sales@cree.com

12 TM-21 Lifetime Report LED I Ts1 Tsi (Interpolated) Ts2 Tsp 45 C 53 C 55 C Tsp K K K Ea/kB A XLamp XM-L White 2000 ma E+19 α 1.459E E E-07 β 9.847E E E-01 Calculated L70 L70(6k) = 2,340,000 hours L70(6k) = 519,000 hours L70(6k) = 362,000 hours Reported L70 L70(6k) > 36,300 hours L70(6k) > 36,300 hours L70(6k) > 36,300 hours Calculated Lifetime L70(6k) = 519,000 hours Reported Lifetime L70(6k) > 36,300 hours % Luminous Flux C (LM-80) 55 C (LM-80) 85 C (LM-80) 45 C (TM-21) 55 C (TM-21) 85 C (TM-21) 53 C (TM-21) ,000 10, ,000 1,000,000 10,000,000 Time (hours) L70: 519,000hrs Figure 10: XM-L TM-21 data with T SP = 53 C Optical and This Electrical document Results is provided for informational purposes only and is not a warranty or a specification. For product specifications, please see the data sheets available at We obtained Copyright the results 2011 in Cree, Table Inc. 7 All by rights testing reserved. the downlight The information a in 2-meter this document sphere is subject after a to 30-minute change without stabilization notice. Cree, time. the Cree 2 As logo the and table shows, XLamp are registered trademarks of Cree, Inc. the downlight meets the target goals of 3000 lm using less than 50 W of power. The downlight also meets the ENERGY STAR efficacy, power factor, CCT and CRI requirements. 2 Testing was performed at the Cree facilities in Santa Barbara, CA. Cree Sales at sales@cree.com

13 Table 7: XM-L downlight steady-state results Characteristic Unit XM-L Downlight Light output (30 min on-time) lm 3106 Power W 47.2 Luminaire effic acy lm/w 65.9 CCT K 3093 CRI 100-point scale 82 Power factor % 99.2 We also tested the intensity distribution of the downlight. 3 Figure 11 shows an even intensity distribution for the downlight with an 86 beam angle. Figure 11: Angular luminous intensity distribution of XM-L downlight Table 8 shows the illuminance of the XM-L downlight at various distances from the light source. 3 Testing was performed in a type A goniometer at the Cree facilities in Shenzhen, China. An IES file for the downlight is available. Cree Sales at sales@cree.com

14 Table 8: XM-L downlight illuminance 86 beam angle Height Illuminance Diameter 1 m 3.3 ft fc lx cm 6.1 ft 2 m 6.6 ft 31.4 fc lx cm 12.2 ft 3 m 9.8 ft 13.9 fc lx cm 18.3 ft 4 m 13.1 ft 7.8 fc 84.4 lx cm 24.4 ft 5 m 16.4 ft 5.0 fc 54.0 lx cm 30.5 ft 6 m 19.7 ft 3.5 fc 37.5 lx cm 36.5 ft 7 m 23.0 ft 2.6 fc 27.6 lx cm 42.6 ft 8 m 26.2 ft 2.0 fc 21.1 lx cm 48.7 ft 9 m 29.5 ft 1.6 fc 16.7 lx cm 54.8 ft 10 m 32.8 ft 1.3 fc 13.5 lx cm 60.9 ft Conclusion This reference design illustrates the excellent results obtainable from a 6-inch downlight based on the Cree XLamp XM-L LED. The high flux output of the XM-L LED enabled these results with a small number of LEDs, keeping system costs low. The directionality of the XM-L LED is a plus in a downlight, putting more light on the surface to be illuminated. The downlight components in this design are all commercially available, showing that an extremely capable luminaire can be designed without the time and expense of developing custom parts. The lighting-class performance of the Cree XLamp XM-L LED makes it an attractive design option for an LED-based 6-inch downlight. Cree Sales at sales@cree.com

15 Bill of materials Table 9: Bill of materials for XM-L downlight Component Order Code/Model Number Company Web Link Diffuser C3-85 Bright View Technologies Driver EUC-060S170ST Inventronics Heat sink 437 Housing XN-8012 Foshan Xin Yi Kangke Metal Product Co. Ltd. Xuning Hardware Plastic Products Co., Ltd. LED Cree, Inc. XM-L product page Reflector Flying Technology Co. Reliance on any of the information provided in this Application Note is at the user s sole risk. Cree and its affiliates make no warranties or representations about, nor assume any liability with respect to, the information in this document or any LED-based lamp or luminaire made in accordance with this reference design, including without limitation that the lamps or will not infringe the intellectual property rights of Cree or a third party. Luminaire manufacturers who base product designs in whole or part on any Cree Application Note or Reference Design are solely responsible for the compliance of their products with all applicable laws and industry requirements. Cree Sales at sales@cree.com