AB05 LUMILEDS | Alldatasheet
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LUXEON® Power Light Sources provide the highest light output with the smallest footprint of any Light Emitting Diodes (LEDs) in the world. This is due, in part, to LUXEON's ground breaking thermal design. LUXEON is the first LED solution to separate thermal and electrical paths, drawing more heat away from the emitter core and significantly reducing thermal resistance. As a result, LUXEON packages handle significantly more power than competing LEDs. LUXEON's larger, brighter emitters together with its unique high-power capabilities provide a tremendous amount of light in a small, durable package. This, in turn, provides lighting designers with a unique opportunity to explore new designs and product ideas and to improve the quality, energy-efficiency, safety and longevity of existing products. Lighting designers working with LUXEON Power Light Sources do need to consider some potentially unfamiliar factors, such as the impact of temperature rise on optical performance. Proper thermal design is imperative to keep the LED emitter package below its rated operating temperature. This application note will assist design engineers with thermal management strategies. We recommend taking the time to develop a thermal model for your application before finalizing your design. The LUXEON Custom Design Guide provides important details about operating temperatures for each LED emitter package. Once you determine your target temperature, a thermal model will allow you to consider the impact of factors such as size, type of heat sink, and airflow requirements. Lighting designers needing additional development support for thermal management issues will find ample resources. The thermal management industry has grown along side advances in electronics design. The thermal analysis resources section at the end of this document provides a useful introduction to some industry resources. LUXEON® Power Light Sources Index Minimum Heat Sink Requirements .2 Inputs/Output of the Thermal Model 4 Best Practices for Thermal Design .8 Thermal Design Using
calculate the junction temperature of the LUXEON device. Typical values for RΘ are shown in Table 2. lations when using a Total Array thermal resistance model. Figure 2. Parallel Thermal Resistance Model
thermal model as control factors in your application design.
- Light output with T J rise
- Color shift with T J rise
information on light output and color shift with rise in T J. junction temperature than other colors. to cool the components alleviates this condition. Table 1. Maximum Thermal Ratings. heat such as electronics or heating due to sun exposure. for selecting RΘB-A is explained in the examples that follow. determine the most suitable heat sink for your application. Stars and Floods including both finned and flat heat sinks. 3D) and forced convection in a small wind tunnel (Figure 3E). flow over the attached heat sink.
Thermal Design Using LUXEON Power Light Sources App Brief AB05 (6/06) 8 TTaabbllee 33 TTyyppiiccaall TThheerrmmaall RReessiissttaanncceess ooff GGlluueess aanndd TTaappeess.. LLeevveell 11 MMoouunnttiinngg -- EEmmiitttteerr LLeevveell 22 MMoouunnttiinngg -- BBooaarrdd SSlluugg ttoo BBooaarrdd ttoo HHeeaatt SSiinnkk AAddddeedd RRΘΘsslluugg--bbooaarrdd ((°°CC//WW)) AAddddeedd RRΘΘBBooaarrdd--HHeeaatt__SSiinnkk__TToopp ((°°CC//WW)) ppeerr EEmmiitttteerr ppeerr EEmmiitttteerr 00..004444 iinn22 ((2288 mmmm22)) 11 iinn22 ((662255 mmmm22)) MMaannuuffaaccttuurreerr AAddhheessiivveess SSlluugg AArreeaa BBooaarrdd AArreeaa IInnffoorrmmaattiioonn GGlluueess Amicon E3503-1 4.5 * Emerson & Cuming-Belgium approx. Ph: 0032/ 14 57 56 11 0.05” thick TTaappeess Bond Ply 105 14 3°C/W The Bergquist Company (0.005” thick) www.bergquistcompany.com Before selecting an adhesive or interface material be sure to determine its suitability and compatibility with LUXEON, your man u- facturing processes, and your application. Philips Lumileds uses Amicon 3503-1 from Emerson and Cuming. This epoxy may be purchased from multiple distributors. Some examples of these distributors may be found in the Philips Lumileds Resource Guide at www.philipslumileds.com. Best Practices for Thermal Design
- A flat, aluminum heat sink can be as effective as a finned heat sink when emitters are spaced at least 25 mm apart.
- A finned heat sink is an effective solution to minimize foot- print area.
- For maximum thermal performance using a flat heat sink, allow an exposed surface area of about 9in 2 per emitter (with 25 mm emitter spacing).
- A LUXEON Flood requires a flat heat sink with an exposed surface area of 36in2 to operate at room temperature (25°C).
- Where practical, use mechanical fasteners to mount heat sinks to smooth and flat surfaces. Evaluating Your Design Use the charts in Figures 4 to 9 to approximate the heat sink size, as well as its orientation and shape. To do so, you must first determine the required RΘ B-A, per emitter, given both the thermal and optical requirements of your application. Then based on the required R Θ B-A, you can use the data in the charts to define your heat sink require- ments. General steps for doing this follow. For single or multi-emitter applications with 25mm spacing, you can approximate heat sink requirements using Figures 4 to 8. For applications with dense emitter spacing such as the LUXEON Flood, use Figure 9. A. Steps to Select Minimum Size Heat Sink SStteepp 11)) Determine allowable RQJ-A With TJ as the constraining variable, you can use the following equation: TJ = TA+(P)(RΘJ-A) Enter the absolute maximum TJ and the worst case oper- ating conditions TA into the equation. You may need to specify a maximum TJ lower than 120°C in order to achieve the optical performance required for your application. See the LUXEON Custom Design Guide for more information. The dissipated power per string, P , can be determined by: P = (V F)(IF) Solve for RΘJ-A using: Junction Ambient Junction Ambient (T T )R P −Θ=
Thermal Design Using LUXEON Power Light Sources App Brief AB05 (6/06) 10 D. Examples EExxaammppllee 11:: LLUUXXEEOONN SSttaarr--SSiinnggllee EEmmiitttteerr A single-emitter LUXEON Star application requires a flat, aluminum heat sink using free convection: It will operate at a maximum ambient of 85°C. The application uses an amber batwing emitter driven at 335mA. SStteepp 11)) Determine allowable RΘ Junction-Ambient. Using the heat transfer formula: TJunction = TAmbient + (P)(RΘJunction-Ambient) or: Where: TJ = 120°C (max. junction temp.) TA = 85°C (max. based on operating conditions) Maximum Vf = 3.3 V for amber batwing (consult data sheet) P d = ( VF )( IF ) Pd = 3.3 V * 335mA = 1.1W Solving for RΘJ-A: RΘJ-A = 32°C/W SStteepp 22)) Obtain the target RΘB-A. Subtract RΘJ-B of the LUXEON emitter: RΘB-A = 32°C/W - 17 °C/W (for Batwing LED) RΘB-A = 15°C/W SStteepp 33)) Review heat sink characterization data in results section. Depending on the space requirements of the application, the thermal resistance target (RΘB-A = 15°C/W) could be met with several different heat sink designs. The area required for a flat, horizontal heat sink with only one free convection surface would be about 9in 2 (Figure 4). The design could also be executed using a 4in 2 flat, vertical heat sink that has two free convection surfaces (Figure 5). To reduce the foot print area to 2in2, a finned heat sink may be used with a total surface area of about 11.5in 2 (Figure 8). If the required drive current of the emitter was 350mA, then the target RΘB-A would have been slightly lower, necessi- tating a heat sink with a slightly larger area. EExxaammppllee 22:: LLUUXXEEOONN LLiinnee --1122 EEmmiitttteerr A LUXEON Line (12 emitters) will be mounted in a vertical position. The maximum ambient operating condition is 75°C for LUXEON products with optics. The emitters are red and driven at 325mA. SStteepp 11)) Determine allowable RΘ Board-Ambient. Using the heat transfer formula: Where: TJ = 120° (max. junction temp.) TA = 75 °C Maximum Vf = 20 V/6 emitters in series (consult data sheet) Maximum V f = 3.3 V Pd = 325mA * 3.3 V = 1.1W per emitter Solving for RΘJ-A: RJ-A = 41°C/W SStteepp22)) Obtain the target RΘB-A. Use Equation 4 to obtain the R ΘJ-B per emitter: Total RΘJ-B = 1.4°C/W for LUXEON Line (consult data sheet) RΘJ-B per emitter = 1.4°C/W*12 RΘJ-B per emitter = 17°C/W RΘB-A = 41°C/W - 17°C/W RΘB-A = 24°C/W per emitter SStteepp 33)) Review heat sink characterization data in results section. Reviewing Figure 5, the LUXEON Line would require 2in 2 foot print of flat heat sink per emitter with two vertically oriented, free convection surfaces. That would correspond to a total HS area of 48in 2 with a 24in2 footprint. The total system RΘJ-A can be obtained by using a calcula- tion similar to Equation 4, where "N" is the number of emitters. ()Junction Ambient Junction Ambient TTR (P) −Θ= JA (120 85)R 1.1 ()Junction Ambient Junction Ambient TTR (P) −Θ= JA (120 75)R 1.1 Junction Board Junction Board LED _Emitter _RTotal_Array_R N ΘΘ= Junction Ambient Junction Ambient Emitter_RTotal_System_R N ΘΘ=
Thermal Design Using LUXEON Power Light Sources App Brief AB05 (6/06) 11 Total_System_RJ-A = 3.4°C/W The TJ at a given TA can be calculated using Equation 3. The total array power must be used when using the total system RΘ J-A. Calculate TJ at TA = 25°C Total Array Power = 12*1.1 W= 13.2 W Equation 3: TJunction = TAmbient + (P)(RΘJunction-Ambient) TJ = 70°C Validation of Method To test the validity of this method, we instrumented and measured a LUXEON Line 12-emitter array with 48in 2 of flat heat sink. In a vertically oriented position, the measured RΘ B-A = 2.5°C/W. By adding the Total Array RΘJ-B of 1.42°C/W, the measured Total System RΘJ-A is 3.9°C/W versus the predicted RΘJ-A of 3.4°C/W.
©2006 Philips Lumileds Lighting Company. All rights reserved. Product specifications are subject to change without notice. Luxeon is a registered trademark of the Philips Lumileds Lighting Company in the United States and other countries. www.luxeon.com www.lumiledsfuture.com For technical assistance or the location of your nearest sales office contact any of the following: North America: +1 888 589 3662 or askluxeon@futureelectronics.com Europe: 00 800 443 88 873 or luxeon.europe@futureelectronics.com Asia: 800 5864 5337 or lumileds.asia@futureelectronics.com Company Information LUXEON®, SuperFlux and SnapLED are developed, manufactured and marketed by Philips Lumileds Lighting Company. Philips Lumileds is a world-class supplier of Light Emitting Diodes (LEDs) producing billions of LEDs annually. Philips Lumileds is a fully integrated supplier, producing core LED material in all three base colors (Red, Green, Blue) and White. Philips Lumileds has R&D centers in San Jose, California and in The Netherlands and production capabilities in San Jose and Penang, Malaysia. Founded in 1999, Philips Lumileds is the high-flux LED technology leader and is dedicated to bridging the gap between solid-state LED technology and the lighting world. Philips Lumileds technology, LEDs and systems are enabling new applica- tions and markets in the lighting world. Philips Lumileds may make process or materials changes affecting the perform- ance or other characteristics of our products. These products supplied after such changes will continue to meet published specifications, but may not be identical to products supplied as samples or under prior orders.