Visual Notification Appliances Using LED Technology

Transcription

1 2017 NFPA Conference & Expo Visual Notification Appliances Using LED Technology Presented by: Dr. John W. Curran President LED Transformations, LLC 2017 NFPA Conference & Expo CEUs: Evaluation: Handouts: Recordings: To receive CEUs for this session, scan your bd badge at the back of the room bf before leaving Complete a session evaluation on the mobile app. (Search app store for NFPA 2017 C&E. ) Handouts will be available via the mobile app and at nfpa.org/conference Audio recordings of all sessions will be available free of charge via NFPA Xchange. 2

2 Copyright Materials This presentation is protected by US and International copyright laws. Reproduction, distribution, ib i display and use of the presentation without written permission of LED Transformations, LLC is prohibited. 3 Course Description LED technology has rapidly become the predominant light source in the general lighting market over the past ten years. More recently, LEDs have found their way into visual notification appliances, replacing the traditional xenon flash tube. What are LEDs and how do they work? What are the characteristics that make them different from other light sources such as the xenon flash tubes used in conventional visual appliances? What are their advantages and disadvantages? In this presentation, Dr. Curran, who is the coinventor of the first LED visual notification appliance will discuss the importantelements ofled technologyincluding, lifetimes, temperature effects, color shifts and reliability. Attendees will come away with a fundamental understanding of this important technology. 4

3 Learning Objectives 1. Attendees will gain an understanding of the effect of heat on LED performance 2. Participants i will learn how LEDs produce light and how that differs from traditional light sources 3. A review of the unique characteristics of LED technology will provide attendees an appreciation of operating performance for this type of device 4. Discussing Haitz s Law will provide participants with an appreciation of the rapid pace of LED evolution and the difficulties that rate can create in terms of product development andtesting testing. 5. How the lighting industry defines lifetime for LEDs as compared to conventional lighting will be reviewed so that attendees can appreciate the implications i of that difference. 5 Outline Outline 1. Introduction A brief background on solidstate lighting gtechnology 2. Physics of SSL How LEDs work 3. Differences Comparison of traditional i and LED light sources 4. LED Standards New metrics 5. Final Thoughts ht The future of lighting 6

4 Introduction The Changing Lighting Marketplace LEDs take over Luminaire Unit Shipments by Lamp Type, World Markets Source: Navigant Research HID % 0.67% 0.55% 0.46% 0.39% 0.32% 0.24% 0.17% 0.14% 0.10% 7 Introduction Semi Conductor Heritage Improved performance and lower cost Technological Push Higher output and lower cost 1, Haitz s Law lumens) Light ou utput / pa ackage (in Red Output (in lumens/device) White Output (in lumens/device) Red Cost (in $/lumen) White Cost (in $/lumen) Output Trend Cost ttrend Cost / Lumen ($ / lumen)

5 Introduction Semi Conductor Heritage Improved performance and lower cost White Light LED Package Efficacy Projections for Commercial Product Source: : DOE Solid State Lighting R&D Plan, May Introduction LED Device Trends Haitzs Law at work $350 LED Prices in $/klum Data Source: Vrinda Bhandarkar, Strategies Unlimited $300 9/3/12 $250 4/19/13 $200 5/9/14 $150 $100 $50 5/9/14 $2.49/lamp 5/1/15 $ Year 10

6 Introduction Everything is Different New names and shapes Traditional Lamp Suppliers LED Suppliers Osram Lumileds Cree Bridgelux Sl Sylvania Philips GE Nichia Seoul Semiconductor Toshiba Sharp Toyota Gosei Edison Opto GE and many more 11 Introduction The Culture Wars Something new to the lighting industry LEDs grew up in the semi conductor world, where change is king; Lighting practices have slowly evolved over time Testing Standards Obsolescence Rapid Evolution of Products Versus Limited Testing Long Product Cycles Slow Style Changes 12

7 Introduction Standards The generation gap Timeline for a new LED based product LM 80 Testing (To claim 50k hours) LDL LM 80 Testing (minimum) LF = Lighting Facts Design Tooling Pilot LF LDL LDL = Lighting Design Lab, Energy Star or Agency Design Lights Consortium = Market Release LED Mfg Introduces new LED LED Mfg Introduces new LED LED Mfg Introduces new LED 13 Introduction Color Changing Applications and features not previously possible 14

8 Introduction Trends Personal lighting and the ability to change color of room light Imagine an office system that recognizes what tasks its occupant is performing, the time of day, the ambient lighting environment, what his/her lighting preferences are, what type of mood to set, etc. Source: Osram Sylvania Or imagine light bulbs that light a home based on what its occupants are wearing 15 Outline Outline 1. Introduction A brief background on solidstate lighting gtechnology 2. Physics of SSL How LEDs work 3. Differences Comparison of traditional i and LED light sources 4. LED Standards New metrics 5. Final Thoughts ht The future of lighting 16

9 Physics of SSL Xenon Flash Tube How it operates The glass tube (typically quartz or borosillicate glass) is filled with Xenon gas. To trigger the flashtube, a capacitor is charged and connected to the electrodes. The xenon gas provides a high resistance path between the two electrodes, so as long as the applied voltage supplied by the charged capacitor is below the ionization voltage of the xenon gas, no current flows. When a high voltage is applied to the trigger coil, it ionizes the gas, allowing a low resistance path to form between the two electrodes. This, in turn, allows the capacitor to discharge, creating a high current flowing between the two electrodes, and causing the xenon gas to heat up forming a plasma. The heat causes electrons in the ionized atoms to jump to higher energy levels. On returning to their ground state, the electrons give up their energy in the form of photons which provides the high intensity light. 17 Physics of SSL Basic Types of LEDs Reflector Cup LED Chip Gold Wire Epoxy Lens The heatsink is what allows the high flux LED to generate much more light Cathode Lens LED Chip Anode Silicon Submount Cathode Outer Package Gold Wire Heatsink Typical construction for a 5mm LED Typical construction for a High Flux LED Typical Flux 3 5 lm Typical Flux lm Number of LEDs to equal the Number of LEDs to equal the output of a 60W incandescent output of a 60W incandescent light bulb > 250 light bulb between

10 Physics of SSL Semiconductor Doping Base P Doped N Doped Structure Structure Structure 5e 3e 5e free 3e free holes electrons 19 Physics of SSL Radiative recombination Photon generation photon electron hole 20

11 Physics of SSL Nonradiative recombination Phonon or heat generation photon electron hole 21 Physics of SSL Creating Light with LEDs Different colors; different bandgaps For metals E g is small; for insulators E g is very large. Materials bt between these two extremes are known as semiconductors E c Bottom of Conduction Band Proton Neutron Electron E gingan E v Top of Valence Band E galingap Electron Hole Photon When electrons and holes combine, the resulting photon has a wavelength related to the bandgap energy given by λ = 1239 / E g Smaller bandgap Lower energy Longer wavelength photon Red Larger bandgap Higher energy Shorter wavelength photon Blue 22

12 Physics of SSL How Do You Make a White LED? Downconverting Phosphor Blue LED + YAG (Yttrium aluminum garnet) = Cool White Blue LED + YAG + Other phosphor (red, green, etc.) = Warm White UV LED + Red phosphor p + Green phosphor p + Blue phosphor p Convention Coating Yellow Phosphor Cool/Warm White LED Spectra Yellow and Red Phosphor Phosphor Conformal Coating InGaN Die Wavelength Blue Die 23 Physics of SSL Thermal Considerations Mounting orientation matters 100% effective 85% effective Thermal resistance of a heat sink is a function of the volume as well as the flow rate of the air surrounding the heat sink. Airflow depends or heat sink orientation as shown in the diagrams at left. 60% effective 70% effective 24

13 Physics of SSL Light extraction Results in high directionality Due to the high Index of Refraction of the semiconductor (n s ) as compared to the epoxy dome material (n e ), by Snell s law, photons exiting the active layer at angles greater than the escape cone angle θ c will be reflected back into the semiconductor and will not exit the device. Active layer Absorbing substrate n e n s θc Somedevice manufacturers cutthesidesofthechipstoprovide the the chips to provide better exit angles and extract more light while others rough the surfaces of the chips to create optical interfaces which can improve the overall light extraction. A third approach is to use what are known as photonic crystals to reduce certain propagation modes (reflected) and increase others (exiting). Source: Lumileds 25 Physics of SSL Photometric Considerations Equivalent to traditional sources What does equivalent mean? LED devices have highly directional light output unlike conventional light sources In directional fixtures such as downlights, this results in much less wasted light trapped in the fixture In properly designed fixtures, this might be a benefit 26

14 Physics of SSL LED Performance Be careful what you ask for; you might get it There is much discussion on light trespass, light pollution, etc. Cut-off Extremes The typical view is that light cut off is desirable for many applications LEDs allow cut offs that are not possible with other light sources Sometimes, that exact cut off is not what people really want LED Transformations, LLC PG&E Emerging Technologies 27 Outline Outline 1. Introduction A brief background on solidstate lighting gtechnology 2. Physics of SSL How LEDs work 3. Differences Comparison of traditional i and LED light sources 4. LED Standards New metrics 5. Final Thoughts ht The future of lighting 28

15 Differences Differences Waveform Comparisons Major spectral and period differences LED non Xen Note: Pulse waveform for LED can be made to any arbitrary shape and length. However, due to the lower light output levels, the LED pulse waveform must be longer than the xenon waveform in order to provide the required minimum intensity 29 Differences Efficacy Comparisons Major difference Efficacy the power or capacity to produce a desired effect In lighting it is a measure of how well a light source turns input power into light (typically measured in lumens) Xenon flash tubes have an efficacy of about 40 lumens/watt LED devices today often have efficacies of over 150 lumens/watt Efficiency the ratio of effective or useful output to total input In lighting, it is the ratio of output optical power to input electrical power (both measured in watts) 30

16 Differences Lifetime Comparisons Catastrophic vs. gradual failure Xenon flashtubes Catastrophic failure due to fracture of the glass tube Gradual failure due to sputtering of cathode material which is redeposited on the wall of the glass tube reducing the light output Typical 1,000,000+ flashes (>277 hours) when operated at less than 30% of tube's explosion energy LEDs Catastrophic failure does not typically occur Gradual failure is typical due to increased discontinuities in the crystal structure of the LED die Typical 25,000 hours or more of operation 31 Differences Response Time Comparisons Some publications An examination of a prototype LED fire alarm signaling appliance J Curran and S Keeney 4 th International Conference on Solid State Lighting Proceedings of SPIE Vol 5530, October 2004 Human Factors Comparison of Detectability For LED and Xenon Tube Light Sources for Fire Alarm Notification Strobes Follow On Testing to Determine Xenon Equivalency K. Savage, TYCO Fire Protection Products, 2012 Performance Objectives for Light Sources Used in Emergency Notification Appliances J. D. Bullough, Y. Zhu Lighting Research Center, Rensselaer Polytechnic Institute May,

17 Outline Outline 1. Introduction A brief background on solidstate lighting gtechnology 2. Physics of SSL How LEDs work 3. Differences Comparison of traditional i and LED light sources 4. LED Standards New metrics 5. Final Thoughts ht The future of lighting 33 Standards Lifetime Considerations Traditional vs. LED lamps Traditional lamps X X X X X Choose a statistically valid population of lamps X X Run them at specified ambient temperature X X X X Cycle them on/off at a prescribed pattern The time at which half the population has failed is considered the lifetime for that lamp X X X X X Typically this process can take up to 15 months for lamps rated at 10,000 hours LED lamps Since LEDs typically don t fail catastrophically, but rather slowly dim, the industry has defined end of life to be the point at which the LED outputs 70% of the light it produced initially Need a different method of measuring lifetime More on that subject in Section 4 34

18 Standards LED Economics Energy and Maintenance Savings 35 Standards What Everyone Wants The ultimate solution If only choosing solid state luminaires was this simple 36

19 Standards Luminaire Lifetime A Luminaire is a System The failure of any one component can cause the entire system to stop functioning LED source Controller Luminaire designers make trade offs among the components, depending on the desired performance criteria for example the number of LEDs ($$$) versus s drive current (lifetime) Optics Thermal Management Driver Luminaire Housing 37 Standards Lifetime Considerations A measurement issue It is difficult to predict the long term performance of a device with only early lifetime data 6,000 Hours of data Source: Cree 10,600 Hours of data 34,800 Hours of data Almost 3.5 X s longer predicted lifetime than the 6,000 hour results 38

20 Standards Electronics/Driver Reliability depends on the driver as well 39 Standards Thermal Considerations It is a matter of where the heat goes Incandescent Fixture Radiated Heat LED Fixture Conducted Heat Ceiling Tile 40

21 Standards Standards Enclosures Can have major effect on LED temperature and lifetime Lamp performance highly dependent on application/environment Open environment T j = 79.1 O C Closed environment T j = 97.4 O C Higher temperature results in lower light output and shorter life Source: Michael Poplawski, PNNL 41 Standards Effect of Heat on LEDs Light output and lifetime reductions Reduction in light output with increasing junction temperature Source: Lumileds data sheet (July 2002) 42

22 Standards Standards Mechanical/Thermal Two approaches for LED Printed Circuit Boards Solder Mask Copper Traces Dielectric Layer Aluminum Plate MCPCB FR4 PCB Copper Traces Solder Mask FR 4 Bottom Copper Layer Thermal Vias 43 Standards Standards Critical to be aware of LM Approved Method: Electrical and Photometric Measurements of Solid State St t Lighting Products Describes testing procedure for evaluating light distribution from LED based luminaires LM Approved Method for Measuring Luminous Flux and Color Maintenance of LED Packages, Arrays and Modules Procedure for measuring lumen depreciation of LED devices Includes procedures for measuring chromaticity changes over time TM Projecting Long Term Lumen Maintenance of LED Light Sources Method for determining when the useful lifetime of an LED is reached TM IES Method for Evaluating Light Source Color Rendition Objective and statistical approach for evaluating light source color rendition which quantifies fidelity and gamut ANSI C Specifications for the Chromaticity of Solid StateLighting State (SSL) Products Describes binning structure to specify LED device colors 44

23 Standards Standards Additional standards that manufacturers should know LM Measuring Luminous Flux and Color Maintenance of LED Lamps, Light Engines and Luminaires Addresses the evaluation of the changes in performance of SSL systems over time Useful ltool lfor engineering i evaluations and luminous flux maintenance for entire assemblies when environmental considerations and variability for the base LED deprecation is incorporated into the analysis TM Projecting Long Term Luminous Flux Maintenance of LED Lamps and Luminaires Intended to help product organizations avoid any unnecessary burdens related to excessive product testing Companion document to LM LM Electrical and Photometric Measurements of High Power LEDs Guide for the measurement of high power (those that require a heat sink) light emitting diodes (LEDs), normally in a form of LED packages, used for lighting products. 45 Standards LM 80 A measurement issue LM 80 provides a measurement procedure for lumen depreciation and chromaticity changes of LED devices over time. It does not explain what to do with the data once it is taken. tenance Lu umen Main 100% 95% 90% 85% 80% 75% 70% 65% 60% 55% 50% Lumen Maintenance versus Hours A particular LED at 85 O C ,000 10, ,000 Hours Data source: (round 10) 46

24 Standards The Fix for LM 80 TM 21 TM 21 provides guidance on how to use the LM 80 data to extrapolate lumen depreciation over time with the following limitations: Limits extrapolation of test data 6 times actual test time (if 20 samples are used) 5.5 times actual test time (if less than 20 samples used) Not valid ldfor sample sizes of less than 10 units Recommended curve is an exponential least squares fit using the equation Φ(t) = B exp( t) where Φ(t) is the averaged normalized luminous flux output over time B is a projected initial constant derived by the least squares fit is the decay rate constant derived by the least squares fit Restricts what data can be used For 6,000 to 10,000 hours of test data use the last 5,000 hours For greater than 10,000 hours use the last half of the collected data It offers no guidance on what to do with ihany chromaticity i data gathered using LM 80 testing procedures 47 Standards ANSI C Chromaticity Standards Latest C edition adds 2 additional color quadrangle regions labeled 2500 O K and 2200 O K and centered at 2238 O K and 2460 O K respectively It also introduces the concept of tighter tolerances for the quadrangles, 4 step MacAdam ellipses versus the previous 7 step Finally it introduces the concept of u' v' circles having the same dimensions as the 4 step quadrangles Source: ANSI C

25 Standards Color Consistency Can be extremely important over lifetime Color changes occur due to binning which occurs during LED production as well as color shift due to phosphor/die changes over time Variation unit to unit Purchase to purchase Shift during lifetime Source: LED Transformations 49 Standards Color Shifts Can change in many directions Results of DOE CALiPER testing from 2008 thru 2010 shows color shifts after 6000 hours of operation (black) and 12,000 hours (red) Even worse, the color shift can move in different directions over those time periods as shown Shift to blue Shift to yellow Source: Michael Royer, PNNL 50

26 Standards Color Shifts Why the changes? A number of different mechanisms can be responsible for color shifts Low/mid power LED housings can yellow, affecting the reflection of light from the sides of the cavity In some older LEDs that use soft silicon coverings, the ephosphor o can settle to the bottom Edges of phosphor plates can curl with a shift hf to blue (left image) or delaminate with a shift to yellow (right image) 51 Standards Lumen Depreciation Applied to LED sources Five different light sources: 2 LED; 2 fluorescent; L Prize and their associated lumen depreciation rates Source: M Royer, Lumen Maintenance and Light Loss Factors: Consequences of Current Design Practices for LEDs, LEUKOS, 12/13 52

27 Outline Outline 1. Introduction A brief background on solidstate lighting gtechnology 2. Physics of SSL How LEDs work 3. Differences Comparison of traditional i and LED light sources 4. LED Standards New metrics 5. Final Thoughts ht The future of lighting 53 Final Thoughts T8 Replacement Lamps They are LED lamps In thefuturecould LED lightingused forgeneral illumination applications expand to be used for fire notification? Easily capable of flashing Being used today for LiFi (e.g. WiFi using the visible part of the electromagnetic spectrum) applications requiring MHz+ frequencies Long lifetimes i (at least for the LEDs) Low voltage and current draws which are two to three times less than conventional xenon flashtubes Already in use for emergency egress lighting applications Power over Ethernet (PoE) 54

28 Final Thoughts A Changing Lighting Industry The LED/Controls tsunami Presently the Lighting gindustry "owns the ceiling" That may be changing The combination of LED and Controls technology will fundamentally change the lighting industry Growth of luminaires with build in sensors Internet of Things (IoT) predicted to be a multi trillion dollar industry New players surveying the industry (e.g. IT companies) Anupcoming battle for control of building systems Fire Industry HVAC Industry Security Industry Lighting Industry Computer Industry 55 Final Thoughts The Future A warning for companies If the rate of change on the outside exceeds the rate of change on the inside, id the end is near. Jack Welsh 56

29 Final Thoughts A Lesson from History Think of how the microprocessor has changed the world over the last 30 years. The lighting world is about to undergo a change not seen since the invention of the incandescent lamp, and driven by that same semi conductor industry. What role will the fire industry play in this LED world? 57 Thank You Contact Information: Dr. John (Jack) W. Curran President LED Transformations, LLC 41 Balsam Bay Court Bluffton, SC (843) jcurran@ledtransformations.com 58