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Hot Binning, Droop, And Other Fun Led Topics


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Selected hot LED topics from Light Fair 2011

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Hot Binning, Droop, And Other Fun Led Topics

  1. 1. “Hot Binning”, Droop, TM-21 and other ‘Fun’ LED Topics<br />June 14, 2011<br />
  2. 2. “Hot” Binning<br />LF Binning @ 85˚C<br />LF Binning @ 25˚C<br />120<br />120<br />110<br />110<br />100<br />100<br />90<br />90<br />80<br />80<br />70<br />70<br />Generic <br />“120” lm LED<br />“Hot” binning could be important if your design runs only, always, and forever, EXACTLY at the “hot” binning temperature AND “hot” binning current your LED vendor has selected for you (e.g., 85˚C, 350mA)<br /><ul><li>The marketing guys may claim to have eliminated binning, but they’ve really just created a new framework from which to do the same old math
  3. 3. Worse: Some suppliers have created this marketing construct for their convenience, not yours!! (read on…)</li></li></ul><li>“Hot/Cold Factor”<br />LF Binning @ 85˚C<br />LED “A”, “Good” H/C (109 lm)<br />120<br />110<br />LED B, “Bad” <br />H/C (106 lm)<br />100<br />90<br />80<br />70<br />Generic <br />“120” lm LED<br />Measurement tolerance on Luminous Flux:<br /><ul><li>Supplier A: 6.5%
  4. 4. Supplier B: 7%
  5. 5. Supplier C: 11.5%</li></ul>“H/C factor” is real and could be an important consideration at very high temperatures; it’s within measurement uncertainties in normal operating ranges and there are other critical issues to keep in mind… (there’s more…)<br />
  6. 6. Bottom Line On Binning & H/C Factor<br />Various LED companies have been claiming to have eliminated binning for years, but so far nobody has really done it<br /><ul><li>“Freedom from binning” really “creates” (or masks) other issues…</li></ul>“Hot/Cold Factor” is a real issue, but focusing on any one isolated parameter can cause you to lose sight of the big picture…<br />LED binning is a reality of LED technology – no matter what mathematical framework you start from – but there are ways to make it easier to deal with and leverage it to your advantage…<br />LED Color Shift Over Max Current & Temp<br />LED “A”, “Good” <br />H/C (109 lm)<br />LED “A”, “Good H/C”: ∆CCT = 411K<br />350-1500mA; 35-105˚C<br />LED “B”, “Bad H/C”: ∆CCT = 31K<br />350-1500mA; 35-105˚C<br />LED “B”, “Bad” <br />H/C (106 lm)<br />
  7. 7. Color Performance and Leveraging Binning to Save Money<br />LED CCx, CCy<br />Yield to Bin<br />Start with the right target, expectation – what traditional lighting technology are you trying to match?<br />“Perfect” color performance is achievable with LED – sometimes at a price…<br />
  8. 8. Games People Play – “Donuts and Holes”…<br />Everybody wants the “hole”; nobody wants the “donut”<br /><ul><li>Marketing: Wants to promote it: “3-step MacAdams”
  9. 9. Customers: Want to have it – and only it</li></ul>Why you care:<br /><ul><li>Everyone pays for the “hole” – somehow…
  10. 10. “Holes” are great for making demo fixtures for the exhibition floor at a trade show. Try ordering a million “holes” and watch the marketing guys run for cover (and/or you for your wallet)…</li></ul>New!<br />
  11. 11. Some Smart Ways To Specify LEDs<br />Buy only the distribution you need (e.g., CFL quality)<br />Specify multi-chip LED arrays that do the color mixing for you – inside the lamp<br />Make your own “hole”: Buy the full distribution to get the best supply/ lowest cost, but do the mixing yourself – in the fixture<br />
  12. 12. Tools for Doing It<br />Works well for downlights, most bulb types, most diffused light applications<br />More challenging for linear, wall-washers, etc.<br /><br />
  13. 13. 50,000 hours is:<br />137 Years at 1 hour/day<br />68.5 Years at 2 hours/day<br />34.2 Years at 4 hours/day<br />22.8 Years at 6 hours/day<br />17.1 Years at 8 hours/day<br />11.4 Years at 12 hours/day<br />5.7 Years at 24 hours/day<br />…A WAG when it comes to LED lifetime… <br />
  14. 14. Semiconductor Reliability Testing<br />Reliability test methods and acceptance criteria for semiconductor components have been standardized (JEDEC, EIAJ, others…) and practiced for decades<br />Think: processors, regulators, microcontrollers, etc..<br />If you’ve ever flown in an airplane, driven in a car, or talked on a cell phone, you’ve depended on this body of scientific work and testing…<br />
  15. 15. LED Reliability Testing<br />LEDs are semiconductor components that happen to emit light…<br />Most LED manufacturers conduct standardized semiconductor component reliability testing – the same tests Intel tests their microprocessors with – on their LED lamps<br />The Illumination Engineering Society of North America published IES LM-80 in 2008 to characterize the Lumen Maintenance aspect of LED semiconductor components<br />Note: Lumen Maintenance ≠ LED Lifetime<br />
  16. 16. LEDs Last Forever!! [under ideal conditions]<br />Well-designed systems with Lighting-class LEDs at low TA, TJ will run a very, very long time…<br />
  17. 17. Typical LM-80 Lumen Maintenance Behavior<br />100%<br />TSP = TA = 85˚C; IF = 1500mA<br />94.1%<br />90%<br />Lumen Maintenance (%)<br />80%<br />70%<br />2,000<br />1,000<br />3,000<br />5,000<br />4,000<br />6,000<br />Time (hours)<br />LEDs do not normally fail catastrophically; gradually lose light output over very long time periods<br />Small “hump” is frequently observed between 0 and 500 hours<br />Lower drive currents and lower temperatures yield higher Lumen Maintenance curves<br />
  18. 18. Everyone Asks for an “LM-80 Report”<br />Here is what one looks like (too detailed, no interpretation, just data…):<br />
  19. 19. LM-80 & TM-21<br />LM-80<br />(testing)<br />TM-21(projection)<br />Something useful<br />+ =<br />IES LM-80-2008 is just an LED testing standard<br />IES TM-21-2011 provides the mathematical framework for taking LM-80 data and making useful LED lifetime projections<br />Key points of TM-21:<br /><ul><li>Developed by major LED suppliers with support from DOE, NIST, PNNL
  20. 20. Projection limited to 6x the available LM-80 data set
  21. 21. Projection algorithm: least squares fit to the data set
  22. 22. L70, L80, L90, Lp projections easily possible
  23. 23. Nomenclature: Lp(Yk) where p is the Lumen Maintenance percentage and Y is the length of the LM-80 data set in thousands of hours</li></ul>Example: L90(12k)<br />
  24. 24. Typical LM-80 Test Behavior and TM-21 Lumen Maintenance Projection (6k)<br />100%<br />94.1%<br />6 x 6,000 = 36,000 hours (max)<br />90%<br />Lumen Maintenance (%)<br />80%<br />Projected L70(6k) = 35,000 hours<br />Reported L70(6k) = 35,000 hours<br />70%<br />10,000<br />20,000<br />30,000<br />40,000<br />50,000<br />Time (hours)<br />First 1k hours is ignored for TM-21 projection purposes<br />Upper reporting bound set by 6x available data (6 x 6k = 36k hrs)<br />Exponential extrapolation to least squares mathematical fit between 1k and 6k hours<br />Reported and projected L70 may or may not be the same number<br />
  25. 25. Typical LM-80 Test Behavior and TM-21 Lumen Maintenance Projection (10k)<br />100%<br />6 x 10,000 = 60,000 hours (max)<br />90%<br />Lumen Maintenance (%)<br />80%<br />Projected L70(10k) = 93,000 hours<br />Reported L70(10k) = >60,000 hours<br />70%<br />10,000<br />20,000<br />30,000<br />40,000<br />50,000<br />Time (hours)<br /><ul><li>Tmax/2 is used for TM-21 projection (10K/2 = last 5K hours)
  26. 26. Upper reporting bound set by 6x data (6 x 10k = 60k hrs)
  27. 27. Exponential extrapolation to least squares mathematical fit between 5k and 10k hours
  28. 28. Reported and projected L70 may or may not be the same number</li></li></ul><li>Typical LM-80 Test Behavior and TM-21 Lumen Maintenance Projection (20k)<br />100%<br />6 x 20,000 = 120,000 hours (max)<br />90%<br />Lumen Maintenance (%)<br />80%<br />Projected L70(20k) = 114,000 hours<br />Reported L70(20k) = 114,000 hours<br />70%<br />10,000<br />20,000<br />30,000<br />40,000<br />50,000<br />Time (hours)<br /><ul><li>Tmax/2 is used for TM-21 projection (20K/2 = last 10K hours)
  29. 29. Upper reporting bound set by 6x data (6 x 20k = 120k hours)
  30. 30. Exponential extrapolation to least squares mathematical fit between 10k and 20k hours
  31. 31. Reported and projected L70 may or may not be the same number</li></li></ul><li>LED Lifetime Is Irrelevant<br />System Lifetime is What Creates Value<br />Heat Sink: Linchpin of the entire system. If this is poorly designed, all the other components can be compromised<br />Driver: Currently the weakest point of the system, but the big companies are working on this<br />LED Lamps: Practically never fail; depreciate very slowly in a well-designed system<br />Optical Components: Can (rarely) yellow over time and lose light; system design choice<br />
  32. 32. LED Chemical Compatibility<br />AllLEDs are susceptible to contamination from volatile organic compounds<br />Accelerated by:<br />Heat<br />Photonic energy<br />Short wavelength light<br />Some glues, adhesives, gaskets, seals, o-rings, oils, lard, tape, potting materials, conformal coatings, FR4 boards… have all been found to be a potential problem<br /><ul><li>Consult your LED supplier for specific guidance on these…</li></li></ul><li>Chemical Incompatibility Mechanism<br /><ul><li>Tightly sealed secondary optic (adhesive, tape, etc.)
  33. 33. Adhesive outgases VOCs, concentrates under optic
  34. 34. VOC penetrates silicone lens
  35. 35. Heat, photonic energy turn the VOC brown
  36. 36. Significant light loss mechanism</li></li></ul><li>One Example<br />Normal LED<br />Contaminated LED<br />
  37. 37. Chemical Compatibility Experiment<br />Vented Optic@ 336 hrs<br />Standard LED<br />(Control)<br />SealedSecondary Optic<br />C<br />
  38. 38. Happens On All Types of LEDs, All Suppliers<br />Multi-chip LED (sealed)<br />Applications Notes…<br />Multi-chip LED (vented)<br />Cree<br />Philips Lumileds<br />
  39. 39. Chemical Incompatibility – Prevention<br />Cree<br />
  40. 40. Chemical Incompatibility – Prevention, cont.<br />Philips Lumileds<br />
  41. 41. Testing for Chemical Compatibility<br />Control<br />Compound<br />Under Test<br />Tape<br /><ul><li>Chemical compatibility test kits are available:
  42. 42. Simple boards
  43. 43. Instructions
  44. 44. Hermetically sealed glass vials</li></li></ul><li>LED Droop<br />“Droop”<br />Light Output, Efficacy<br />LPW efficacy<br />Light Output<br />Max Drive<br />Current (mA)<br />Binning <br />Current (mA)<br />Input Current (If, mA)<br />Light output and LPW efficacy of an LED varies with input drive current<br />Different LED types are BINNED at different currents<br />Driving an LED much above the binning current is perfectly OK, but comes at a cost – “droop”…<br />Solving the droop issue would be an enormous technical breakthrough for LED, but<br />
  45. 45. LED Chips: Size Doesn’t Matter<br />* Typical data sheet of packaged LED lamp<br /><ul><li>Small chips droop; Big chips droop
  46. 46. Small chips sometimes appear to have higher efficacy since they are customarily binned higher up the droop curve
  47. 47. Primary real difference (not an advantage or disadvantage) is in the optics  very application-specific</li></li></ul><li>Problem or Opportunity?<br />LED Capacity<br />Light Output, Efficacy<br />LPW efficacy<br />Light Output<br />Max Drive<br />Current (mA)<br />Binning <br />Current (mA)<br />Input Current (If, mA)<br />“Droop” was a much bigger deal when LEDs were barely 70 LPW – now there are LPW “to spare” for some applications<br />Capacity of LED is Luminous Flux @ Max Drive Current<br />
  48. 48. LED Capacity Example<br />LED Capacity<br />Light Output, Efficacy<br />LPW efficacy<br />Un-utilized <br />capacity<br />Light Output<br />= $$$<br />Max Drive<br />Current (1500mA)<br />Binning <br />Current (350mA)<br />Input Current (If, mA)<br />At the binning current only 23% of the capacity of this LED is utilized;77% of the LED goes UNUSED!<br />There are, of course, practical limitations to this…<br />
  49. 49. Capacity Limits – Energy Star<br />Energy Star LPW “capacity” limit<br />LED Capacity<br />Light Output, Efficacy<br />LPW efficacy<br />Light Output<br />Max Drive<br />Current (mA)<br />Binning <br />Current (mA)<br />Input Current (If, mA)<br />Energy Star Requirements may be the capacity limit <br />Energy star potential capacity limits: <br /><ul><li>System efficacy minimum
  50. 50. Reported/Projected LED lifetime (per TM-21)</li></li></ul><li>Other Capacity Limits – Thermal<br />MR16 Thermal “capacity” limit<br />MR16<br />LED Capacity<br />Light Output, Efficacy<br />LPW efficacy<br />Light Output<br />Max Drive<br />Current 4 amps<br />Binning <br />Current (1.1A)<br />Input Current (If, A)<br />System Thermal capacity is the limiting factor in this highly constrained application<br />
  51. 51. What About LED Cost?<br />The Semiconductor Industry is a solution looking for a problem<br />Articulating the problem in a way a chip company can understand is often the challenge<br />A problem – once understood – gets solved in a very predictable way…<br />
  52. 52. Moore’s Law for Transistor Cost<br />-36% <br />CAGR<br />
  53. 53. Driving Lumen Affordability with Technology<br />Working on both numerator and denominator!!<br />93% improvement in 5 years<br />Cool White (6000K)<br />Normalized $/klm<br />* At maximum drive current<br />
  54. 54. How Would You Like That Lumen…?<br />U.S. DOE Multi-year R&D Program, March 2010, p.28<br />Cool? Warm? High CRI? Efficient? Long life? Stable Color? Uniform? Optically-controlled? At what drive current? Energy Star?<br />Simplistic comparisons like this do not work – everything matters with LED…<br />
  55. 55. By That Metric, LEDs are Already Cheap!<br />Raw $/klm Cost of One Commercially-available LED<br />XLamp XM-L<br />$/klm<br />$/klm @<br />Binning <br />Current <br />DOE<br />Values<br />$/klm @<br />Max Drive<br />Current<br /> LED Drive Current <br />Raw LED cost is already close to parity with most incumbent technologies – if we must be simple about it, but…<br />How would you like that lumen…?<br />Raw LED cost is only part of the story (driver, optic, etc.)<br />Must factor in application efficacy, energy savings, maintenance avoidance, environmental impact, etc., get the real answer on LED VALUE (different than cost!)<br />
  56. 56. Cost Impact of Increasing LED Performance, Fully Utilizing LED Capacity – A Real Example<br />2007<br /><ul><li>42LEDs
  57. 57. 650 lm
  58. 58. 12W</li></ul>2010<br /><ul><li>8LEDs
  59. 59. 575 lm
  60. 60. 10.5W</li></ul>Cree LR6<br />Cree CR6<br />>$100 Commercial <br />Wholesale<br />$50 Retail<br />