The Future of Lighting Fixture Design LED Thermal Management

Transcription

1 Welcome to The Future of Lighting Fixture Design LED Thermal Management Cavendish Conference Centre, London Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 1

2 Abstract The majority of problems in a LED lighting solution are caused by poor thermal management. The fact is that LED heat dissipation must primarily utilize conduction and convection means rather than radiation. Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 2

3 LED junction temperatures are limited and hence heat management cannot solely depend upon radiant waste heat dissipation anymore. In fact, radiation is negligible. Abstract Heat Management requires a SYSTEM approach! This is a paradigm shift, lighting designers must recognize when moving to LEDs Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 3

4 Abstract Thermal challenges Different heat dissipation mechanism in LED system, from conventional light sources High Power LED Light Engines dissipating more heat and requiring better cooling solutions Thermal management ensuring customers staying at the forefront of the lighting revolution Lighting fixtures undergoing the most radical redesign in a century Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 4

5 The Challenge Proper control of Tj critical and key Inside LED Module Main means = Conduction. External Main means = Convection. LED die Tj Case Tc Waste Heat Disposal LED Module Manufacturer OEM Lighting Designers Junction Temp (Tj) is monitored via Case Temp (Tc) as Junction Temp cannot be measured Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 5

6 Means Cooling Options Cooling options for LEDs range from natural convection into air, passive or active to liquid cooling means Air cooling with conventional heat sinks, fans and/or advanced two-phase technology is widely accepted by the market place and will remain the primary choice. The market reluctantly go for liquid cooling, such as cold plates, due to various issues associated with water near electronics and pumps. Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 6

7 Means Passive AL heatsinks CU heatsinks Advanced passive cooling methods Active Fans assisted heat sink (forced convection) Membrane assisted heat sink (forced convection) Cold Plates Water pumped underneath heatsource (for special applications and not covered here) Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 7

8 AL or CU heatsinks (natural convection) Passive Material Thermal Conductivity (W/mK) Aluminum (99.5) ~ 240 Aluminum (Alloys) ~120 - ~180 Copper ~ 400 There is little heat transfer in horizontal direction die die ~ 45 ~ 45! Heat travels in a ~ 45 angle into the heatsink. Therefore increasing the surface area with a larger heat spreader will not significantly improve the thermal design. Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 8

9 Pros & Cons Passive Heat Sink Solutions Pros No risk of operation No cost of operation Highly reliable No performance degradation Lot of variations possible No CO₂ Emissions 0 db operation Cons Bigger form factor than active Higher Weight Performance limitations Requires more material per W cooling Orientation sensitive Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 9

10 AL or CU heatsinks (natural convection) Passive ¹ Conventional passive coolers are confined to handling low power LED applications due to the thermal limitations of the materials used Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 10

11 Fan or Membrane assisted sinks Active Fan or membrane assisted heat sinks increase the air flow thus significantly improving the convection properties of the heat sink Results in much smaller area required to achieve the same thermal resistance. SUNON LA A99DN - Cooling module; LED 40 W Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 11

12 Pros & Cons Active Solutions Pros Sunon LED 40 W More compact form factor Lower weight Lower Tr case to ambient Resource considerate (less material usage) Nuventix Par25 32W Cons Noise and Sound Echos and Vibrations Proactively attract debris/dust Increasing sound levels Reduced performance Reduced lifetime CO₂ Emissions, not ecological friendly Wiring, Controllers Cost of operation Specs typically allow for ~10% failure rate Severe longevity concerns Everything whichs moves will stop moving High risk of operation Potential replacement cost Unpredictable cost of ownership. Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 12

13 Fan or Membrane assisted sinks Active ² Fans can provide a much higher airflow than membranes thus can reach lower thermal resistance requirements Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 13

14 The Passive Revolution Advance Passive 2-Phase Systems employ evaporative cooling technology to transfer thermal energy from one point to another by evaporation and condensation of a working fluid embedded in a vacuum tight vessel. Q Heat Input Evaporator Capillary wick Container Liquid Flow Adiabatic section Vapour Flow Heat Output Condenser Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 14

15 Advance Passive The Passive Revolution Based on this physical principle FrigoDynamics has developed a patented platform of advanced passive HPK-Fin 2-Phase heat exchanger solutions. They are extremely effective, light weight, eco friendly, 100% recyclable and easy to apply cooling solutions. They pose neither cost nor risk of operation, and thus are the most cost effective Solid State LED cooling solutions available. They are particularly well suited to cooling high power LEDs with a small heat source foot print due to being able to efficiently spread heat across all areas of the 2-Phase heat exchanger regardless of heat source size and meeting challenging ΔT requirements. Material Thermal Conductivity (W/mK) Aluminum (99.5) ~ 240 Aluminum (Alloys) ~120 - ~180 Copper ~ Phase device ~50,000 - ~200,000 Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 15

16 The Passive Revolution Advance Passive The LED market is high demanding on eco friendly solutions. Reliability, longevity and cost of ownership are key. Passive cooling means are primarily considered for LEDs and modules. Advanced passive cooling solutions can help when.. Many commercial and industrial LED applications are demanding thermal needs that conventional passive cast or extruded heat sinks can no longer meet, due to the thermal limitations of the materials used. Substantial size and weight of heat sinks, along with significant and substantial performance degradation, when changing orientation, signifies that things must change. Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 16

17 The Passive Revolution Advance Passive Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 17

18 Pros & Cons Passive 2-Phase HX Solutions Pros No cost of operation No risk of operation, no friction Highly reliable, nothing moving No performance degradation No CO₂ Emissions Resource saving Compact form factors Very light weight Soundless, 0 db operation Application specific scaleable Cools all lumen values Lot of variations possible Meets Low ΔT requirements Orientation insensitive Cons No functional or operational cons Requires volume Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 18

19 Pros & Cons Summary in Brief ³ Required Tr case to ambient at Pth levels of 60W + at ΔT 30K (Tr c-a < 0.5 K/W) Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 19

20 Thermal Design Process Process 1. Determine aesthetic goals 2. Determine envelope (dimensional) constraints 3. Determine operation orientation(s) 4. Calculate thermal powerloss of chosen LED 5. Determine max T case at max T ambient 6. Calculate thermal resistance case to ambient required. Select cooling means based on the above! If an extruded or cast AL heat sink does not meet the thermal requirements, or is too big and/or too heavy and you want to avoid active means or active means are not permitted or desired, FrigoDynamics is here to help. Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 20

21 Thank You Thank You for your attention Dr Song Lin 30. May 2012 Copyright 2012 FrigoDynamics 21