专题篇_LED测试技术.ppt

1、,LED测试技术 Measurement technology of LED,OUTLINE,Introduction of photometry facilities Measurement of LEDs Measurement of SSL products Color rendering of white LED light sources,OUTLINE,Introduction of photometry facilities Measurement of LEDs Measurement of SSL products Color rendering of white LED l

2、ight sources,Photometric bench,4 m long Luminous intensity (cd) of lamps Illuminance meters Luminance meters Averaged LED intensity (A results vary depending on size of heat sink, ambient temp. and how LED is mounted) Use a temperature-controlled heat sink. Set heat sink temperature at 50C, 60C, . (

3、need to be standardized) Use a metal-core PC board to mount the LED to the heat sink.,Data Example,OUTLINE,Introduction of photometry facilities Measurement of LEDs Measurement of SSL products Color rendering of white LED light sources,Incandescent,Fluorescent,15 lm/W,90 lm/W,Solid State (White LEDs

4、),Potential 200 lm/W,Solid State Lighting,Driving Force Energy Saving,Lighting consumes 22 % of electricity 8 % of total energy (statistics of USA),Solid State Lighting, by 2025 50% reduction of energy consumed by lighting 10% reduction in greenhouse gas emissions Customer savings of $115 billion an

5、nually (U.S. Dep. Energy),SSL Products are coming out,Niche applications,General lighting applications,U.S. Dept. of Energys initiative for SSL,DOEs Lab-to-Market strategy,Commercialization support Product Testing Standards development Laboratory accreditation program Lighting for Tomorrow competiti

6、on,DOE Energy Star program for SSL products,SSL products for general illumination (residential and commercial applications) Designed to ensure energy efficiency (also quality) relative to existing sources Requirements for luminaire efficacy, chromaticity, and CRI (Ra 75 for indoor applications) Requ

7、ires measurements by accredited laboratories. is developing NVLAP (National Voluntary Laboratory Accreditation Program) program for SSL products.,(2nd draft 4/9/2007),Measurement of SSL products,Luminaires are measured for relative luminous intensity distribution and total luminous flux, normalized

8、by measured lamp total luminous fux, e.g., per 1000 lm. Absolute scale given by published lamp lumen values.,Traditional luminaire photometry (Relative Photometry),This method does not work for SSL products.,Lamp and fixture cannot be separated. Published LED luminous flux values are not reliable.,S

9、SL products: mostly in a form of luminaire.,Test methods for lamps and luminaires combined are needed.,Standardization for SSL specification and measurement,Standards for SSL being developed in USA ANSI C78.377 Specifications for the Chromaticity (CDC2) IESNA LM-79 Approved method for electric and p

10、hotometric measurement of SSL products (CDC2) IESNA LM-80 Life test of SSL products International standards being developed CIE TC1-69 Color Rendition of White Light Sources,Table 1.,ANSI C78.377A Specifications for the Chromaticity of SSL products (Draft),ANSI C78.377 Draft,Flexible Color,IESNA LM-

11、79 Approved Method for Electrical and Photometric Measurement of SSL Products (Draft),Covers SSL products complete with electronics and heat sinks. - therefore, no temperature issues (SSL product operated at 25C ambient). Does not cover LED modules, LED packages, nor individual LEDs. Addresses both

12、aspects of lamp photometry and luminaire photometry Total luminous flux (lumen), electrical input, luminous efficacy (lm/W) Chromaticity, CCT, CRI (4 integrated) Angular intensity distribution,No spectral mismatch correction needed for luminous flux. Total luminous flux and color quantities measured

13、 at the same time. Color quantities measured as spatially (4) averaged values.,One of the methods recommended (for smaller SSL products),A goniphotometer is needed for large-size SSL products),IESNA LM-79 Approved Method for Electrical and Photometric Measurement of SSL Products (Draft),l,Measuremen

14、t of SSL products,Measuring a refrigerator LED luminaire,Total luminous flux (lm) Total spectral radiant flux (350 nm to 830 nm) Chromaticity, CCT, Duv, CRI (4 averaged) 25C ambient temp. SSL products up to 30 cm diameter or linear 1.5 m long. Individual LEDs also measured.,For SSL products,Data exa

15、mple (LED downlight),Measurement of SSL products,Goniospectroradiometer,Introduction of photometry facilities Measurement of LEDs Measurement of SSL products Color rendering of white LED light sources,OUTLINE,Luminous Efficacy of a source lm/W,=,Radiant Efficiency,Luminous Efficacy of Radiation lm/W

16、,X,Luminous Efficacy of a Source (lm/W),Optical power W Electrical power W,Luminous flux lm Optical power W,Luminous flux lm Electrical power W,(External Q.E.),Theoretical maximum lm/W of a given source.,Depends only on spectral power distribution (SPD).,Daylight,Low pressure sodium lamp,White LED,5

17、20 lm/W, 400 lm/W, 250 lm/W,Theoretical maximum,Color Rendering vs. Energy Efficiency,Excellent color rendering,? color rendering,No color rendering,Problems of CRI (1),3-LED Model Peaks at: 457, 540, & 605 nm CRI Ra =80,Ref.,LED,This spectrum has higher lm/W.,Good scores do not guarantee good satur

18、ated colors,Problems of CRI (2),CRI penalizes light sources having enhanced color contrast.,Neodymium incandescent lamp CRI Ra = 77 (Normal incandescent lamp Ra =100),Ref.,LED,Poor correlation of visual evaluation (preference) of RGB white LEDs and the CRI,Narendran, 2002 (SPIE Proc.),63,81,25,63,82,98,CRI Ra value,“RGB Low” (460/525/635) 4100 K CRI Ra=24,“RGB High” (460/525/615) 4100 K CRI Ra=64,Reproduction of RGB white light used in Narendrans expe