Cree XLamp XM-L LED 10,000-Lumen High-Bay Reference Design

Transcription

1 Cree XLamp XM-L LED 10,000-Lumen High-Bay Reference Design Application Note CLD-AP96 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: implementation and analysis... 8 Conclusions...13 Special thanks...13 Bill of materials...13 Introduction This application note details the design of a replacement high-bay luminaire using Cree s XLamp XM-L LED. The high flux output and efficacy offered by the XM-L LED make it a particularly strong candidate for use in a high-bay luminaire. The performance of the XM-L LED means that it is not necessary to use hundreds of LEDs to match the light output of traditional metal halide and fluorescent high-bay lighting. An XM-L LED-based high-bay luminaire not only offers energy efficiency benefits but its long lifetime also reduces maintenance costs in typically hard-to-reach industrial and commercial applications. 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, the Cree logo and XLamp are registered trademarks 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 six step framework for creating LED and lamps. 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 3. Estimate efficiencies of the optical, thermal & electrical systems 4. Calculate the number of LEDs needed 5. Consider all design possibilities and choose the best 6. Complete final steps 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. 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 effiiciencies will drive the number of LEDs needed in the luminaire. Based on the design goals and estimated losses, the designer can calculate the number of LEDs to meet the design goals. 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. 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 high-bay luminaire that can replace high-intensity discharge (HID) and 54-watt fluorescent T5 and T8 in commercial, industrial and warehouse applications. As a replacement luminaire, this design uses a form factor that is similar to traditional high-bay lighting currently in use. 1. Define lighting requirements Table 2 shows a ranked list of desirable characteristics to address in a high-bay luminaire design. Table 2: Ranked design criteria for a high-bay luminaire Importance Characteristics Units Critical Important Illuminance distribution footcandles (fc)/lux (lx) Electrical power watts (W) Lifetime hours Luminous flux lumens (lm) Manufacturability Operating temperatures C Operating humidity % RH Correlated Color Temperature (CCT) K Color Rendering Index (CRI) 100-point scale Ease of installation cree.com. 2

3 Table 3 summarizes the ENERGY STAR requirements for solid-state. 1 There are no ENERGY STAR requirements for high-bay. Table 3: 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 Color maintenance requirements: solid state indoor only 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. 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 Light source shall remain continuously illuminated within one second of application of electrical power. 1 ENERGY STAR Program Requirements, Product Specification for Luminaires (Light Fixtures), Eligibility Criteria, Version 1.1 cree.com. 3

4 Characteristic Source run-up time requirements: directional and non-directional Power factor requirements: directional and non-directional Transient protection requirements: all Requirements 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. The DesignLights Consortium provides requirements for a high-bay luminaire. 2 Characteristic Table 4: DesignLights Consortium high-bay luminaire requirements High-Bay and Low-Bay Fixtures for Commercial and Industrial Buildings Application High-Bay-Aisle Lighting Minimum light output 10,000 lm 10,000 lm Zonal lumen density 30% %, %, 0 20 Minimum luminaire efficacy 70 lm/w 60 lm/w Allowable CCTs (ANSI C ) < 5700 K < 6000 K Minimum CRI L70 lumen maintenance 35,000 hours 35,000 hours Minimum luminaire warranty 5 years 5 years 2. Define design goals Table 5 shows the design goals for this project. 2 Technical Requirements Table v1.6, DesignLights Consortium Qualified Products List - Non-Residential Applications cree.com. 4

5 Table 5: Design goals Characteristic Unit Minimum Goal Target Goal Light output lm 10,000 10,000 Power W 150 < 150 Luminaire efficacy lm/w Lifetime hours 50,000 50,000 CCT K 5,000 5,000 CRI 100-point scale 75 > 75 Power factor 0.9 > 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 10,000-lm target, we estimated 93% optical efficiency and 85% driver efficiency. We also estimated a solder point temperature of 85 C. The PCT output highlighted in Figure 1 shows that, at 2.4 A, sixteen XM-L LEDs provide sufficient light output to meet the design goals. Optic LED 1 Model Cree XLamp XM-L {CW/NW/WW} Flux T6 [280] Tj (ºC) 85 Price $ - SYS # LED SYS lm tot SYS W SYS lm/w Current (A) Figure 1: PCT view of the number of LEDs used and drive current Because this reference design is targeted as a replacement high-bay luminaire, the design has a form factor similar to incumbent. The optic is a commercially available 16-inch diameter reflector commonly used in HID high-bay. The LED array size and arrangement is designed to fit this reflector. To maximize the luminaire s light output, we painted the inside of the reflector with reflective white paint. cree.com. 5

6 Figure 2: High-bay reflector Thermal Requirements The thermal solution is a key factor in the success of this reference design, as the LEDs are concentrated at the center of the luminaire. To make this design feasible, we worked with two partners to design and fabricate a custom metal core printed circuit board (MCPCB) and heat sink. MCPCB As shown in Figure 4, this high-bay luminaire design has sixteen XLamp XM-L LEDs arranged in a closely spaced 4 x 4 rectangular array. To handle the high power density we used a special copper MCPCB from Rayben. As shown in Figure 3, where a typical MCPCB has a copper trace layer and a dielectric layer to transfer heat to the aluminum base layer and on to the surrounding environment, the Rayben MCPCB in this design has a micro heat exchanger (MHE) layer to transfer heat to the copper base layer and offers greater heat transfer capability. The electrically neutral thermal path of the XM-L LED makes this possible. Figure 3: MHE thermal substrate Figure 4: MCPCB with XM-L LEDs cree.com. 6

7 Heat Sink This reference design uses a custom vapor-chamber heat sink by Steady Heat & Mass Transfer Technology Academy Ltd, shown in Figure 6. As Figure 5 illustrates, the heat sink has a unique vapor chamber design to enhance thermal conductivity and heat dissipation. A special liquid is vacuum sealed in a chamber formed between the heat source, in this design the MCPCB, and the heat fins. The heat from the MCPCB causes the liquid to evaporate; the vapor condenses on the cooler part of the chamber to enhance cooling and collects on the base near the heat source to repeat the cycle. Figure 5: Heat sink design Figure 6: Heat sink attached to heat sink support We performed thermal simulations to verify this thermal design is sufficient. Figure 7 shows the thermal simulation results for the design. The simulated solder point temperature (T SP ) is 72 C. Figure 7: Thermal simulation of XM-L high-bay heat sink cree.com. 7

8 Driver We used a market-ready constant-current driver that fits within the heat sink support and matches the design s current and voltage range. The high-bay luminaire design can also accommodate locating the driver separate from the luminaire. Figure 8: Driver 4. Calculate the number of LEDs Using Cree s PCT, we determined that sixteen XLamp XM-L LEDs produce sufficient light to meet the 10,000-lm design goal. 5. Consider all design possibilities There are many ways to design an LED-based high-bay luminaire. This reference design aims to show that the XM-L LED enables a highbay luminaire offering superior performance. The XM-L LED offers a wide range of color temperatures. We selected a neutral white LED for this high-bay luminaire design, shown highlighted in Table 6. Table 6: XM-L order codes Color CCT Range Base Order Codes Min. Luminous 700 ma (lm) Order Code Min. Max. Group Flux (lm) T4 240 XMLAWT LT40E3 Neutral White 3,700 K 5,000 K T5 260 XMLAWT LT50E3 T6 280 XMLAWT LT60E3 6. Complete the final steps: implementation and analysis Using the methodology described above, we determined a suitable combination of LEDs, components and drive conditions. This section describes how Cree assembled the high-bay luminaire 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 MCPCB. cree.com. 8

9 3. We ran the LED DC input wires through an enclosed channel in the heat sink. The channel runs the length of the heat sink and insulates the LED DC input wires from the heat and moisture in the heat sink. 4. We soldered the LED DC input wires to the MCPCB. 5. We tested the connection by applying power to the LEDs and verified the LEDs lit up. 6. We applied a thin layer of thermal conductive compound to the back of MCPCB and attached it to the heat sink with screws. 7. We secured the heat sink support to the end of the heat sink with screws. 8. We connected the LED DC input wires to the driver DC output wires with connectors. 9. We fit the LED driver into the heat sink support. This is an optional step as the driver is a remote standalone type. This driver can be located apart from the luminaire or a centralized dedicated power line can be directly wired to the luminaire. 10. We secured the reflector to the heat sink with screws. 11. We performed final testing Figure 9: Assembled high-bay luminaire ready to test Results Thermal Results Cree verified the board temperature with a thermocouple to confirm that the thermal dissipation performance of the heat sink aligns with our simulation. As shown in Figure 10, the measured solder point temperature was 61 C, which shows that the heat sink is sufficient for this design. T SP Solder Point Temperature T2 PCB Temperature T3 Heat Sink Temperature 61 C 56 C 50 C Figure 10: Thermal measurement cree.com. 9

10 Based on the measured solder point temperature of 61 C, the junction temperature (T J ) can be calculated as follows. T J = T SP + (LED power * LED thermal resistance) T J = 61 C + (7.8 W * 2.5 C/W) T J = 81 C Estimated LED lifetime Figure 11 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 HEW LM-80 data set is 6000 hours at a 2-A drive current. The TM- 21 methodology limits the projection to six times the duration of the LM-80 data set. 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 % Luminous Flux ,000 10, ,000 1,000,000 10,000,000 Time (hours) Figure 11: 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) cree.com. 10

11 Figure 12 shows the calculated and reported lifetimes for the XM-L LED, interpolated from the data shown in Figure 11, at the measured 61 C T SP for the XM-L LED in this design. Although this design operates at a slightly higher current than the 2-A level of the TM-21 data set, Cree s experience with the XM-L LED gives us reason to expect that, with a reported L70(6k) lifetime greater than 36,300 hours and a calculated L70(6k) lifetime of 302,000 hours at 2 A, the high-bay luminaire to easily meet the 35,000-hour DesignLights Consortium L70 lumen maintenance requirement when operating at a measured 2.3 A. 3 LED I Ts1 Tsi (Interpolated) Ts2 Tsp 55 C 61 C 85 C Tsp K K K Ea/kB A XLamp XM-L White 2000 ma E-02 α 9.543E E E-06 β 9.887E E E-01 Calculated L70 L70(6k) = 362,000 hours L70(6k) = 302,000 hours L70(6k) = 158,000 hours Reported L70 L70(6k) > 36,300 hours L70(6k) > 36,300 hours L70(6k) > 36,300 hours Calculated Lifetime L70(6k) = 302,000 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) 61 C (LM-80) ,000 10, ,000 1,000,000 10,000,000 Time (hours) L70: 302,000hrs Figure 12: XM-L TM-21 data with T SP = 61 C 3 That is, after 35,000 hours of operation, the LED will still deliver at least 70% of its initial luminous flux. cree.com. 11

12 Optical and Electrical Results We obtained the results in Table 7 by testing the luminaire in a 2-meter sphere at steady state. 4 As the table shows, the luminaire meets the 10,000-lm target goal using less than 150 W of power and compares favorably with published data for two comparison metal halide. The XM-L high-bay luminaire also exceeds the DesignLights Consortium efficacy, CCT and CRI requirements. Characteristic Unit Table 7: XM-L high-bay luminaire steady-state results DesignLights Consortium High-Bay Requirement Comparison Metal Halide High-Bay Luminaire Comparison Pulse Start Metal Halide High-Bay Luminaire XM-L High-Bay Luminaire Result Luminous flux lm 10,000 10,427 9,676 10,737 Power W Luminaire efficacy lm/w CCT K < 5,700 K ~ 5,000 ~ 5,000 5,154 CRI 100-point scale Current A Goniometric measurements show a consistent beam shape and light distribution for the XM-L high-bay luminaire Figure 13: Angular luminous intensity distribution of XM-L high-bay luminaire The light intensity and distribution data in Table 8 show the XM-L high-bay luminaire effectively illuminates the area in which it is installed. 4 Testing was performed at Cree s Durham Technology Center. 5 Ibid. IES files for the high-bay luminaire are available. cree.com. 12

13 Table 8: XM-L high-bay light intensity and distribution Height Illuminance Diameter 1.3 m 4.2 ft fc lx 1.3 m 4.3 ft 2.5 m 8.3 ft fc lx 2.6 m 8.5 ft 3.8 m 12.5 ft 56.3 fc lx 3.9 m 12.8 ft 5.7 m 16.7 ft 31.7 fc lx 5.2 m 17.1 ft 6.3 m 20.8 ft 20.3 fc lx 6.5 m 21.4 ft 7.6 m 25.0 ft 14.1 fc lx 7.8 m 25.6 ft Conclusions This reference design illustrates the excellent performance of a high-bay luminaire based on the Cree XLamp XM-L LED. The efficacy of the XM-L LED allows a relatively small number of LEDs to match the light output of comparison with better color consistency without the metal halide s slow start-up times and ultraviolet light. The lighting-class performance of the Cree XLamp XM-L LED makes it an attractive design option for an LED-based high-bay luminaire. Special thanks Cree would like to acknowledge and thank the following partner companies that collaborated in the successful prototyping of this luminaire. Rayben Steady Heat & Mass Transfer Technology Academy Ltd. Bill of materials Table 9: Bill of materials for XM-L high-bay luminaire Component Order Code/Model Number Company Web Link Driver HLG A Mean Well USA, Inc. Heat sink HBEXC-98D160L200-S Steady Heat & Mass Transfer Technology Academy Ltd. LED XMLAWT LT60E3 Cree, Inc. XM-L product page MCPCB MHE 301 Rayben Thermal epoxy ASTA-7G Arctic Silver, Inc. 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.com. 13