雷士照明品质系统SSL

Reliability & Quality Limitations of SSL  System Design  R&D Centre (Shanghai) NVC Lighting Technology Co LtdNVC Lighting Technology Co., Ltd.  2011‐5‐12 Lingmin Xu New Stamp Background1 2 Limitations of thermal management 3 Quality of Optical design 4 Optimization for Electrical System Background What is reliability ?Background——What is reliability ? • Quality: The totality of Quality • Failure: The termination of features and characteristics of a product or service that bear on its ability to satisfy d i li d d• Failure: The termination of the ability of an item to perform a required function stated or implied needs. (ISO8420) Failure perform a required function (IEC50(191)) Reliability li bili• Reliability: The probability that a system will perform its intended function under stated conditions for a specified period of time without failures (IEC50(191)/SEMI E10-600) B k d LED li hti i th tBackground——LED lighting is the system Heat sink LED array Heat sink Lum Module /  LED Array Controller LED array  (PCB) LED component m inair Power supply &  controller Power supplyOptics e Optics pp y Reliability Limitations LED failureReliability Limitations——LED failure • LED component reliability testing is based on standard semiconductor pre- release qualification test conditions and methods defined by JEDEC . 10,000 ppm m A Reliability of WW LEDs 2830 ppm y 1,000 ppm f F a i l u r e s s @ I f = 7 0 0 m 0 ° C 1130 ppm 100 d R a t e o o u r s o f S t r e s = 8 5 ° C T j = 1 1 30 ppm 100 ppm E x p e c t e f t e r 1 , 0 0 0 h o T b pp 10 ppm LUXEON® Rebel Competitor B Competitor A a f Product A Product B Product C Th P LED d t th t f t t hi f il i t l l• The Power LEDs product, the rate of catastrophic failure is extremely low, • LED component failure (excepted the fail mode: lumen maintenance) is not the key item in a SSL system. Background1 2 Limitations of thermal management 3 Quality of Optical design 4 Optimization for Electrical System Reliability Limitations Thermal managementReliability Limitations——Thermal management • Getting the heat away from the LEDGetting the heat away from the LED source is essential Heat sink Thermally  Conductive Material – Check proper thermal management, since Tj determines performance: light output, useful life, efficacy and light color quality. • For SSL lighting thermal management, two critical factors that we focused : thermal spreading resistance & p g thermal interface management. Reliability Limitations Thermal InterfaceReliability Limitations——Thermal Interface • The interface between theThe interface between the circuit board and the heat sink is critical due to the heat sensitive nature of LED sources . non‐isothermal interface • A thermally conductive material is typically used between the PCB andbetween the PCB and heat sink to minimize air gaps which reduce the transfer of heat . Reliability Limitations Thermal Spreading ResistanceReliability Limitations——Thermal Spreading Resistance • LED components are getting smaller and hotter. The heat sinks have become much larger than the LED devices that they cool and a thermal spreading resistance occursand a thermal spreading resistance occurs. • The higher the power and the smaller the source the greater thesmaller the source, the greater the spreading resistance • Optimized heat sinks provides anOptimized heat sinks provides an effective way to spread the heat uniformly, a very uniform temperature distribution leading to more efficiencydistribution leading to more efficiency from the heat sink. Background1 2 Limitations of thermal management 3 Quality of Optical design 4 Optimization for Electrical System Quality Limitations O ti l d i • Take the light from the LED to the areas you want to illuminate. Quality Limitations——Optical design g y • ……and keep it from areas you don’t want to illuminate. • ……while minimizing the losses. O pticaal E fficieency L ossses Quality Limitations O ti l d i Luminaire #1 Luminaire #2 Quality Limitations——Optical design Luminaire #1 Luminaire #2 Lens Design1 Lens Design2 Lens Design1 Lens Design2 Illumination Effect ▪Lower illumination ▪Bad Uniformity ▪High and uniform illumination, sharp edge effect ‹Serious discoloration, ‹non-uniform illumination No discoloration, high and uniform illumination, sharp edge effectillumination edge effect Light Pattern(1m） Accurate and high efficient optics design is essential not only for luminaireAccurate and high efficient optics design is essential not only for luminaire  efficacy but also for illumination effect. Quality Limitations Optical design ‐‐ Near‐field Luminance Distributions  for Optical Design and Simulation  Quality Limitations——Optical design Illumination distributions for target place The basic LED optical model is enough for the SSL system without the secondary optical components. Basic LED optics model Complex LED optics model Background1 2 Limitations of thermal management 3 Quality of Optical design 4 Optimization for Electrical System Reliability Limitations Electrical System In-rush current : Typical Power Supply ( PS ) Switched Circuit Reliability Limitations——Electrical System  Electrical overstress ( EOS ) Case Ⅱ- --Hot Switching (Mutated Load )Case Ⅰ--Hot Plugging (Power Supply) Metal migration  Broken wires Damage near bond pads Reliability Limitations Electrical SystemReliability Limitations——Electrical System  In-rush current : Case Ⅰ--Hot Plugging (Power Supply) • Solution: “Soft Start” / “Cold Switched” is sufficient to assure no current surge. In-rush current : Case Ⅱ- --Hot Switching (Mutated Load ) • Solution: “Active in-rush current protection” Reliability Limitations Electrical System Over-current : Case Ⅰ--high-current repetitive pulsing Reliability Limitations——Electrical System  • Problem : gain in light output and efficiency decreases three different duty cycles (5% 20% and #1: Ipk-pk=333mA, Irms=329.8mA, Freq. =34.7kHz #2: Ipk-pk=115mA, Irms=330.6mA, Freq. =2.51kHz three different duty cycles (5%, 20% and 50%), at a frequency of 1000 Hz Ripple current flux efficiency 333mA 144lm 35lm/w Ripple current flux efficiency 115mA 191lm 40lm/w ReliabilityReliability Electrical  Reliability EMI Thermal  Design Security  IP Class  Reliability Design Vibration Supply voltage， Topology Components         is increased Pressure， IP  Topology， Components， Control strategy， Protection Conduction， Radiation， Surge is increased  by 2  degrees, dow n 10% Class, Failure is  caused by  vibrationProtection  circuit，PFC n 10%  reliability Reliability Limitations——Electrical System Quality  h Reliability Limitations Electrical System  components E t 8000h 105C Lifetime Electroly capacito O perati tem perat O perat tem pera tic  or ng  ture ting  ature Semiconduct or devices Ripple current Reliability Limitations Electrical System Factors that influence efficiency Reliability Limitations——Electrical System  Loss of magnetic components and design of it have a major impact on efficiency Reliability Limitations Electrical System Magnetic components of the design considerations Reliability Limitations——Electrical System  Structural  Design Electrical  Design Stray  parameters Loss  design Thermal  Design EMI Design Reliability Limitations Electrical System DC loss Coil Choose thick wire Reliability Limitations——Electrical System  T f Skin effect Core Material multiple AC loss Transformer loss Core Material 1.Reduce primary turns NP; Loss Leakage 2 .Increasing the width of  winding ( election EE core, to increase the width);Leakage inductance to increase the  width); 3 .Increase the height and width ratio;d a o; 4 .Reduce the insulation between the windings; Loss VS Ns Ae Ae 5 .Increase the coupling  between windings. Loss  VS  Ns , Ae C l iConclusions SSL is about more than just LEDs, and designing a reliable & quality SSL S i l i f k Li i iSSL System involves a series of key Limitations. Source: Strategies Unlimited Product manage centre