Cree XLamp CXA3050 LED Wall Pack Reference Design

Transcription

1 Cree XLamp CXA3050 LED Wall Pack Reference Design Application Note CLD-AP170 rev 0D 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 needed Consider all design possibilities Complete the final steps... 6 Other design possibilities...15 Conclusions...15 Bill of materials...16 Introduction Wall packs are widely used in environments such as parking garages, tunnels, building entrances, walkways and recreational areas to provide perimeter, accent and security lighting. Wall packs have traditionally used high pressure sodium, metal halide (MH), or incandescent lamps. This reference design demonstrates the possibility of retrofitting an existing metal halide wall pack with a small number of Cree XLamp CXA3050 LED integrated arrays to achieve a result that exceeds the original s light output with improved color rendering, efficiency and energy savings. The high flux output and efficacy offered by the XLamp CXA3050 LED integrated array make it a particularly strong candidate for use in a wall pack. 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 luminaires 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 application note, 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 in Table 1. Step Explanation Table 1: Cree 6-step framework 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 4. Calculate the number of LEDs needed 5. Consider all design possibilities and choose the best 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. 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. 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 for this project was to retrofit an existing fixture to produce a 250 watt equivalent wall pack using the XLamp CXA3050 LED integrated array. 1. Define lighting requirements Table 2 lists important characteristics to consider in the design of the wall pack in this reference design. Table 2: Ranked design criteria for wall pack Importance Characteristics Metric Critical Important Luminous flux lumens (lm) Electrical power watts (W) Efficacy lm/w Price $ Lifetime hours Operating temperatures C Correlated color temperature (CCT) K Color rendering index (CRI) 100-point scale Lamp-to-lamp consistency Power factor Manufacturability We gathered the performance data in Table 3 from data sheets available publicly. Cree Sales at sales@cree.com. 2

3 Table 3: Performance data for comparison 250 W MH wall packs Characteristic Unit Wall Pack A Wall Pack B Light output lm 12,333 12,394 Power W Efficacy lm/w CCT K CRI 100-point scale 63 - There are currently no ENERGY STAR requirements for wall packs, however the DesignLights Consortium provides requirements, summarized in Table 4. 1 Characteristic Minimum light output Zonal lumen density Minimum luminaire efficacy Allowable CCTs (ANSI C ) Table 4: DesignLights Consortium wall pack requirements Outdoor Wall-Mounted Area Luminaires 300 lm = 100%: 0 90, < 10% lm/w 5700 K Minimum CRI 65 L70 lumen maintenance Minimum luminaire warranty 50,000 hours 5 years 2. Define design goals Table 5 shows the design goals for this project. We measured the lumen output of the MH lamp to be approximately 20,000 lm with the reflector in the wall pack but without the wall pack s glass cover and we used this number as goal for the CXA3050 wall pack. Table 5: CXA3050 wall pack design goals Characteristic Unit Minimum Goal Target Goal Light output lm 20,000 > 20,000 Luminaire efficacy lm/w 70 > 70 Power W 285 < 285 CCT K CRI 100-point scale 80 > 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. To match the 20,000 lumen target, the initial output of the MH lamps in the wall pack without the glass cover, we estimated 100% optical efficiency and 100% driver efficiency. 2 We also estimated a case temperature of 75 C. As highlighted in yellow in Figure 1, the PCT shows that, at 2 A, three XLamp CXA3050 LED integrated arrays provide light output that exceeds the design goal. 1 Technical Requirements Table v2.1 2 We did not expect the wall pack optics and driver to be 100% efficient, but we used this value for our estimates of the conditions to match the lumen output of the MH lamp. Cree Sales at sales@cree.com. 3

4 Current (A) Model LED 1 Cree XLamp CXA3050 LES 23r {EZW} Flux X2 [5590] Tc (ºC) 75 Price $ - SYS # LED SYS lm tot SYS lm/w SYS W Figure 1: PCT output with CXA3050 data Thermal Requirements Each of the three XLamp CXA3050 LED integrated arrays in this reference design was attached to an individual extruded aluminum heat sink, shown in Figure 2. The heat sinks were cut at an angle to fit in the housing and so the dimensions of the heat sink assembly serve to position of LEDs within the wall pack housing and no additional mounting hardware was required. The three heat sinks were connected side by side by a metal bar screwed to the top and bottom edges of the heat sinks, as shown in Figure 3. Figure 2: CXA3050 wall pack heat sink Figure 3: CXA3050 wall pack heat sink assembly Figure 4 shows the results of the thermal simulation of the design. The 75 C estimated case temperature (T c ) is within the operating limit curve for the CXA3050 LED integrated array. 3 3 For additional information on thermal management, refer to the Thermal Management Application Note and the CXA3050 LED Thermal Load Application Note Cree Sales at sales@cree.com. 4

5 Figure 4: CXA3050 wall pack thermal simulation Drive Electronics Cree selected a constant current driver, shown in Figure 5. Each XLamp CXA3050 LED integrated array is connected to an individual driver, however, a single driver can be custom made to match the number of LEDs used in a production wall pack. Figure 5: CXA3050 wall pack driver Secondary Optics An optical cavity is a common practice for LED optical design to improve system efficacy. In this design, we replaced the original metal reflector with a white reflective paper, and kept the original glass optic that serves as the front cover of the wall pack. The CX Family LED Design Guide provides basic information on the requirements to use Cree XLamp CXA LEDs successfully in luminaire designs. 4. Calculate the number of LEDs needed The XLamp CXA3050 LED offers a wide range of color temperatures and flux levels. As highlighted in Table 6, we selected a neutral white LED for this wall pack design. Cree Sales at sales@cree.com. 5

6 Table 6: CXA3050 LED order codes CCT Range CRI Min Typ Group Minimum Luminous 1400 ma Flux 85 C Flux 25 C* Chromaticity Regions Order Code W CXA N00W40E X A0, 5B0, 5C0, 5D0 CXA N00X20E5 X CXA N00X40E5 W CXA N0HW20E K W A0, 5B0, 5C0, 5D0 CXA N0HW40E5 X CXA N0HX20E5 V CXA N0UV20E V A0, 5B0, 5C0, 5D0 CXA N0UV40E5 W CXA N0UW20E5 5. Consider all design possibilities The basic design of this wall pack is to retrofit an existing wall pack fixture with XLamp CXA3050 LED integrated arrays. We therefore removed the reflector and MH lamp from the fixture and replaced them with the heat sink assembly and the attached LEDs. We opened a slot in the top and bottom of the housing to allow airflow for cooling. The driver is IP 67 rated, and with the appropriate wiring connections, this prototype wall pack s construction is similar to that of other fixtures that are exposed to the elements. An O-ring could be added to make a seal between the heat sinks and the housing. To show the capabilities of the CXA3050 LED integrated array, we made two wall packs: one with two LEDs and another with three LEDs. As shown in Figure 6, the two surfaces of the reflector in the MH wall pack direct light normal to the lens opening. The reflection angle of the light from the horizontally mounted MH lamp is the same as angle of the lens opening. The CXA3050 s light emission is lambertian and the heat sink is aligned to match the angle of the lens opening, as shown in Figure 7. The directional light output of the XLamp CXA3050 LED integrated array is an advantage in a wall pack design. Figure 6: MH wall pack light output Figure 7: CXA3050 wall pack light output 6. Complete the final steps This section illustrates the techniques used to retrofit a wall pack with XLamp CXA3050 LED integrated arrays and shows the results of the design. Cree Sales at sales@cree.com. 6

7 Prototyping Details The essence of the design is to replace the internal components of an existing wall pack with the heat sinks and drivers necessary to operate the Cree XLamp CXA3050 LED integrated arrays. The assembly steps are detailed below. 1. We verified the component dimensions to ensure a correct fit. 2. We removed the internal components of the original MH wall pack and cut a slot in the top and bottom of the housing. 3. We screwed a metal bar to the top and bottom edges of the heat sinks to connect the three heat sinks side by side. 4. We applied a thin layer of thermally conductive compound to the back of the CXA3050 LED integrated arrays and attached the LEDs to the heat sink. Thermal conductive epoxy can also be used. 5. We attached a two piece connector to the LED to align the LED and provide for electrical connection. Companies that participate in the Cree Solution Provider Program (CSP) can supply connectors and their websites can be accessed from the Cree website. 6. We fed the LED input wires through the through holes in the heat sink and attached the wires to the connectors. 7. We installed reflective paper (with cutouts for the LEDs) over the LEDs. Figure 8 shows the wall pack at this point in the assembly process. Figure 8: CXA3050 LED integrated arrays attached to heat sink 8. We secured the heat sink to the front part of the housing with screws. 9. As shown in Figure 9, we mounted the drivers to the back part of the housing. Figure 9: Drivers connected to housing Cree Sales at sales@cree.com. 7

8 10. We connected the output wire of one driver to an individual LED s input wire, resulting in a one to one driver to LED connection. We made the other two driver to LED connections. 11. We secured the front and back parts of the housing together. 12. We performed final testing. Results Thermal Results Cree verified the case temperature with a thermocouple to confirm that the thermal dissipation performance of the heat sink is sufficient. For the 3 LED wall pack, we measured a case temperature of 67 C for the center LED and 65 C for the other two LEDs, within the operating limit curve for the CXA3050 LED integrated array. LED Lifetime We used the Environmental Protection Agency (EPA ) TM-21 Calculator to determine the calculated and reported lifetimes for the XLamp CXA3050 LED integrated array at a 2-A input current and 67 C case temperature. The duration of Cree s CXA3050 LM 80 data set is 6,048 hours at 85 C. The TM-21 methodology limits the projection to six times the duration of the data set. With a reported L70(6k) lifetime greater than 36,000 hours and a calculated L70(6k) lifetime of 76,000 hours for the CXA3050 LED integrated array, we expect the CXA3050 wall pack to easily exceed an L70 lifetime of 50,000 hours. The CXA3050 LED integrated array s calculated and reported L90(6k) lifetimes of 23,000 hours are a significant improvement over the 10,000- to 15,000 hour lifetimes of a typical MH lamp. Optical and Electrical Results We obtained the results in Table 7 and following by testing the luminaire in a 2-meter sphere and Type C goniophotometer at steady state. 4 As the table shows,both CXA3050 wall packs exceed the performance of the comparison wall packs, providing considerably higher light output, CRI and efficacy. Both CXA3050 wall packs also exceed the DLC light output, efficacy and CRI requirements. The 2 LED CXA3050 wall pack matches the lumen output of the comparison wall packs with a 36% energy savings. The 3 LED CXA3050 wall pack provides 66% more lumen output using the same power as the comparison wall packs. The DLC requirements specify a wall pack that produces no uplight. The CXA3050 wall packs use the housing and glass optic of wall pack A, and their lumen densities are the same as the original fixture. Characteristic Unit Table 7: CXA3050 wall pack steady-state results DesignLights Consortium Wall Pack Requirement Target Goal Wall Pack A Wall Pack B 2 LED CXA3050 Wall Pack 3 LED CXA3050 Wall Pack Light output lm ,00 12,333 12,394 13,746 20,454 Luminaire efficacy lm/w 70 lm/w > Power W - < Zonal lumen density = 100%: 0 90, < 10% %: 0 90, 10% %: 0 90, 9% %: 0 90, 10% %: 0 90, 10% CCT K 5700 K CRI 100-point scale 65 > Testing was performed at Cree s Durham Technology Center. IES files for the 2 LED wall pack and the 3-LED wall pack are available. Cree Sales at sales@cree.com. 8

9 Figure 10 shows the polar candela distribution for the comparison wall packs. Wall Pack A Wall Pack B Figure 10: Polar candela distribution for comparison wall packs The polar candela distribution in Figure 11 shows a consistent beam shape and light distribution for the CXA3050 wall packs. 2 LED CXA3050 Wall Pack 3 LED CXA3050 Wall Pack Figure 11: Polar candela distribution for CXA3050 wall packs Cree Sales at sales@cree.com. 9

10 Table 8 through Table 11 show the simulated illumination of the comparison wall packs and the CXA3050 wall packs. The simulated area is 150 ft X 150 ft (45.7 m X 45.7 m) with the wall packs mounted 15 ft (4.6 m) high at the mid point of one side of the area. Illuminance values on the ground in front of the wall pack at various ratios of distance to mounting height are shown. Cree Sales at sales@cree.com. 10

11 Table 8: Simulated illumination for comparison wall pack A Wall Pack A Legend fc lx ft ft ft ft ft ft Ratio of Distance to Mounting Height fc lx fc lx fc lx fc lx fc lx fc lx fc lx fc lx fc lx Ratio of Distance to Mounting Height Cree Sales at sales@cree.com. 11

12 Table 9: Simulated illumination for comparison wall pack B Wall Pack B Legend fc lx ft ft ft ft ft ft Ratio of Distance to Mounting Height fc lx fc lx fc lx fc lx fc lx fc lx fc lx fc lx fc lx Ratio of Distance to Mounting Height Cree Sales at sales@cree.com. 12

13 Table 10: Simulated illumination for 2 LED CXA3050 wall pack 2-LED CXA3050 Wall Pack Legend fc lx ft ft ft ft ft ft Ratio of Distance to Mounting Height fc lx fc lx fc lx fc lx fc lx fc lx fc lx fc lx fc lx Ratio of Distance to Mounting Height Cree Sales at sales@cree.com. 13

14 Table 11: Simulated illumination for 3 LED CXA3050 wall pack 3-LED CXA3050 Wall Pack Legend fc lx ft ft ft ft ft ft Ratio of Distance to Mounting Height fc lx fc lx fc lx fc lx fc lx fc lx fc lx fc lx fc lx Ratio of Distance to Mounting Height Cree Sales at sales@cree.com. 14

15 Other design possibilities This reference design demonstrates a retrofit wall pack design based on an existing product. Other designs are possible to fulfill application specific requirements, such as the following: A custom heat sink with an O ring can be made to seal the housing and glass cover from the environment. The drivers can be housed separately and relocated to the back of the fixture. A tilting feature can be added to adjust the distribution pattern and achieve a cut-off requirement. The pictures in Figure 12 are examples of other wall pack reference designs. Figure 12: Example wall pack design Conclusions This reference design illustrates the excellent performance of a wall pack based on the Cree XLamp CXA3050 LED integrated array. The light output and efficacy of the CXA3050 LED integrated array enable a wall pack with excellent light output and color consistency without metal halide s slow start-up and restrike times and ultraviolet light. With color temperatures from 2700 K to 5000 K and lumen output up to Cree Sales at sales@cree.com. 15

16 9,000 lm, the CXA3050 LED integrated array offers the possibility of a product line of wall packs based on a single XLamp LED component. The lighting class performance of the Cree XLamp CXA3050 LED integrated array makes it an attractive design option for an LED based wall pack. Bill of materials Table 12: Bill of materials for CXA3050 wall pack Component Order Code/Model Number Company Web Link Tyco Electronics Corporation Connector ahrpbmcvdgutbgvklwhvbgrlcnmuzxh0zxjuywxizwfkzxiuahrtba Driver LDB SW Excelsys Technologies Heat sink HeatsinkUSA LLC LED CXA N0HX20E5 Cree, Inc. CXA3050 product page Reflective paper F-16 White98 White Optics LLC whiteoptics.com/white97%20film%20data%20sheet.pdf Thermal compound Silver Ice Timtronics 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 luminaires 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. 16