[Original] 牟同升: LED standards are basically in sync with the industry


Editor's Note: Associate Professor of the Department of Optoelectronic Engineering of Zhejiang University and Chairman of Hangzhou Zheda Tricolor Instrument Co., Ltd., Tong Tongsheng, has been engaged in optical and color testing technology research in the field of lighting and display test technology for more than 20 years, in the field of flat panel display in the field of semiconductor lighting LED. And other aspects have achieved fruitful research results. According to incomplete statistics, he has obtained 8 national invention patents and 9 utility model patents; he has written two books, published more than 30 professional papers, and participated in the formulation and validation of more than 30 national standards. He is a member of the Working Group on Semiconductor Lighting LED Technology Standards of the Ministry of Information Industry and an expert in the International Standards Working Group of IEC projects. He is a leading expert in the industry and a leader and leader in the industry. In terms of LED standards, he is undoubtedly one of the most talked about. His views and opinions have a strong guiding significance for the development of the entire industry.

The product standard in the form of "blank specification" is reasonable

China Lighting Network: Please briefly introduce the current development of LED standards.

Zhai Tongsheng, Chairman of Zheda Sancolor: LED standards should include upstream product standards such as LED chips, materials, devices, modules and components, as well as downstream application product standards such as LED lighting, display and other special applications. The upstream product standards of LEDs are mainly drafted by the “Working Group of Semiconductor Lighting Technology Standards of the Ministry of Industry and Information Industry”; the standards for downstream application products involve standardization bodies in various related application fields. For example, the National Lighting Standardization Committee is responsible for the standardization of lighting application products; the “Lights and Accessories Subcommittee” is responsible for formulating the standards for LED light sources and their accessories, and the “Lighting Subcommittee” is responsible for formulating relevant standards for LED lamps. The standard for LED display application products is currently drafted by the “Industrial and Information Industry Department Flat Panel Display Technology Standard Working Group”; among them, “LED Display Group” is responsible for formulating LED display product standards for outdoor and indoor use, “OLED grouping” "Responsible for the development of OLED product standards, LED backlight standards for liquid crystal display LCDs are currently directly responsible for the development of the entire large working group. The application standards of LEDs in traffic lights and indications are formulated by the Ministry of Public Security Road Traffic Management Standardization Technical Committee. The LED mine lamp product standards are formulated by the Coal Mine Special Equipment Standardization Technical Committee.

By the end of 2008, more than 20 standards had been developed specifically for LED products. Some of these standards need to be approved by the relevant government authorities before they can be promulgated. Recently, various standardization technical committees have newly established a number of LED standards, so the LED standards are basically in sync with the industry.

At present, LED products are still in rapid development, and they are quite mature in the field of signal indication; they have also been widely used in the field of display; and the lighting field has just begun, still in its infancy. Therefore, the current standards are mainly basic standards such as definitions, classifications, and methods, as well as relatively mature application product standards. The product standard is more reasonable in the form of “blank specification”, which indicates the direction of the development of the industry and leaves a certain space for the enterprise.



Industry is currently in urgent need of safety, energy efficiency, longevity and application standards

China Lighting Network: In your opinion, what is the most urgent standard for China's semiconductor lighting industry?

Zhai Tongsheng, Chairman of Zhejiang University Tricolor: Whether a industry can develop rapidly and well, the key factor is whether the products can truly meet the needs of people in society. Standards are important levers to regulate market and industry development; at present, governments at all levels attach great importance to the development of the LED industry, and formulate various preferential and support policies, which are very important for the development of the LED industry. But whether an industry can be stronger or bigger will essentially follow its own development rules. LEDs have their outstanding characteristics and are therefore widely used in the fields of indication, display and special lighting. However, many of the features of LEDs, if not well designed and scientifically applied, will bring new problems. For example, high-brightness LEDs are very good performance as indicators and displays; in lighting products, a reasonable optical system design is required to avoid glare; excessive LED blue light can also damage the human eye retina; current single LED power Too small, if you put multiple chips together, you must solve the heat problem. The lifetime of LED devices is closely related to the junction temperature. In practical applications, the junction temperature of LEDs is much higher than the ambient temperature, so the lifetime is far less than 100,000 hours.

Therefore, the standards currently in urgent need of the semiconductor industry include safety, energy efficiency, longevity and LED lighting application standards. Safety standards are mandatory standards for products entering the market. For LED products, in addition to meeting the mechanical and electrical safety standards of traditional electronic products, special attention should be paid to the safety standards for optical radiation. The international standard IEC62471 includes the optical radiation safety requirements for LEDs. The EU regulations have incorporated the light safety of LEDs into mandatory indicators. The CE certification already includes LED light radiation safety.

The energy efficiency of LED products is the focus of the industry. From the perspective of luminous efficacy (lumens/watt), LED products may not be as good as high-efficiency fluorescent lamps and HID sources. In order to cope with government projects, some domestic units have overemphasized “lighting efficiency”, including some LED street lighting products, with color temperatures reaching nine thousand (K) and even tens of thousands (K). LED products are entering the field of general lighting applications, color temperature and color rendering are very important. For indoor lighting applications, LED products with warm white light are required, and the current low-color white LED efficiency is still low.

In addition, the LED light source can achieve very good lighting effects by means of decentralized illumination, multi-sub-light source lamps and digital control. Although the average illuminance value is not as good as the traditional light source, the actual visual effect is not bad. Therefore, how to scientifically measure the energy efficiency of LED products, formulate corresponding standards, give full play to the characteristics of LEDs, and make the LED industry develop in a healthy direction is a very important task.

Last year, the National Development and Reform Commission issued a subsidy policy for energy-efficient lighting products, including LED products. However, due to the lack of corresponding energy efficiency standards, it is difficult for the LED industry to obtain national policy subsidies. Life expectancy is a key indicator of LED products. Many publicity claims that LED life is very long and can reach 100,000 hours. This is misleading for the LED industry. In fact, many inferior LED products may last for less than a thousand hours. Therefore, how to objectively evaluate the life of LED products is an important task.



Develop standards to pay attention to the difference between LED and traditional light source

China Lighting Network: What are the difficulties in developing LED standards? What are the main international standards for reference?

Zhai Tongsheng, chairman of Zhejiang University, said: The LED standard must pay attention to the difference between LED and traditional light source. First of all, we must fully understand the characteristics of LED products and human needs for light. LED products are directly compared with traditional light sources. With traditional concepts, it is difficult to formulate a standard that truly meets the development of LED industry. On the other hand, the LED industry is still developing rapidly. The performance standard of LED application products must have a certain maturity of products, and the standard can play a role in regulating the market and promoting industrial development.

According to the agreement reached between ISO and IEC, the international standards in the field of electrical and electronic engineering are mainly formulated by the International Electrotechnical Commission IEC. At present, the IEC technical committee dealing with international standards for LED products mainly includes IEC TC 47 "semiconductor device", IEC TC 34" lamp and related equipment", IEC TC 110 "flat panel display device", IEC TC 76 "optical radiation safety". IEC TC47 has been issued for a number of related small and medium power LED devices. A number of related standards for indication, display and optical communication have been released. In recent years, there have not been many new standards. IEC TC34 has issued several safety standards for LED modules and connectors, which have a certain effect on lighting LED products. IEC TC110 mainly involves LED backlights for LCD display and OLED standards. Currently, three standards have been basically completed, and six other standards are being developed. In particular, LED backlights are an important application direction of LEDs. China (mainly Taiwan) And Hong Kong's research institutions have certain characteristics in regional dynamic backlight technology; China's IEC experts are actively striving to have more say in international standards. The OLED international standard is one of the most outstanding areas in China's international standardization activities. At present, two international standards have been drafted by China, including Tsinghua University (Beijing Weixinnuo Technology Co., Ltd.) and Zhejiang University (Hangzhou Zheda Tricolor Instrument Co., Ltd.) as the heads of the two international standard projects.

At present, IEC TC76 focuses on the optical radiation safety standards of LED products, and is developing the IEC62471 series of standards, which is a mandatory safety standard for human health. “Zheda Three Colors” Company is the only unit in China that has participated in the formulation of IEC62471 series standards. At present, the biggest problem facing international standards is how to conduct effective measurement and evaluation. LED products are more complicated than lasers. The “Zheda Tricolor” company has been researching for more than five years and actively participates in the development of international optical safety measurement standards.

Most of the documents issued by CIE of the International Commission on Illumination are technical reports. About one-tenth of them are formulated into standards, and are generally released jointly with ISO or IEC to become an industry standard. It is worth noting that the current IEC technical reports are directly translated into our national standards, and how to apply these standards needs to be considered. The CIE's report on LED technology, including the color rendering of white LEDs, and the measurement methods for LED devices, have been released; five other related documents are being drafted.



National standards and industry standards are not contradictory

China Lighting Network: The Semiconductor Lighting Technology Standards Working Group was responsible for drafting seven electronic industry standards such as "Semiconductor Lighting Terminology" and "Semiconductor Light-Emitting Diode Phosphor". The National Lighting Appliance Standardization Technical Committee passed at the Zhuhai Conference in July 2008. 15 LED national standards were submitted for review, such as "Glass and LED Module Terms and Definitions for General Lighting". What are the similarities and differences between the two sets of standards in terms of their nature and function?

Zhai Tongsheng, Chairman of Zhejiang University, said: The standards of the two standardization bodies are different. The LED standard working group mainly formulates the standards for the front end of LED chips, materials, modules, components, etc., while the lighting standardization committee mainly sets standards for LED light sources and lamps for lighting. So the two are not contradictory.

Zhejiang University Tricolor Company participated in the formulation of industry standards

China Lighting Network: We understand that Zhejiang University Tricolor Instrument Co., Ltd. is one of the drafting units of "Plasma for Semiconductor Light Emitting Diodes". This standard first proposed the use of "external quantum efficiency" instead of "relative brightness" as an indicator for evaluating the luminous efficiency of phosphors. Can you briefly introduce the pros and cons of these two test methods?

Zhai Tongsheng, Chairman of Zheda Sancolor: Since the 1980s, we have participated in the formulation of national standards for photophosphorus, including calcium halide calcium phosphate phosphors and rare earth trichromatic phosphors. How to evaluate the luminous efficiency of phosphors has always been a difficult problem. At that time, due to the limitations of the test instrument technology, the relative brightness was used as an evaluation index; the relative brightness of the test phosphor was measured by a method compared with the standard phosphor. We have also invented a relative brightness meter for many phosphor and lamp manufacturers.

With relative brightness, the most critical is the need for a corresponding standard phosphor. As a standard phosphor, a complete set of standard phosphor preparation, storage, and volume transfer procedures is required, involving a series of tasks that are much more complicated than setting standards. In fact, more than 20 years have passed, and in the national standard material system, no brightness standard phosphor has been established yet. In addition, since the brightness value of the phosphor is closely related to the emission spectrum and the color temperature, it is difficult for the phosphors of different spectra to judge directly from the relative brightness.

LED phosphors face the same problem, how to establish a national standard brightness phosphor? The color temperature of LEDs is very wide. How do you choose standard phosphors with different color temperatures? When the semiconductor lighting standard working group formulated the "phosphor for semiconductor light-emitting diodes" standard, we proposed to use "external quantum efficiency" instead of "relative brightness" as an evaluation index for evaluating the luminous efficiency of phosphors; Zhejiang University Tricolor also developed corresponding Test equipment, the 13th Research Institute of China Electronics Group cooperated in a large number of tests and verification; in addition, the experts of the standard working group also held an on-site analysis meeting at the 13th Shijiazhuang Institute to test several sets of LED phosphor samples; It is shown that using "external quantum efficiency" to evaluate the luminous efficiency of LED phosphors is a relatively scientific method, which essentially reflects the photon energy conversion performance of phosphors. And no standard phosphor is needed; it is completely an objective physical measurement method.

China Lighting Network: When are the above 7 industry standards and 15 national standards expected to be introduced? After the introduction of the LED national standard, the LED industry will face a major reshuffle. In order not to be eliminated, what should LED companies prepare for?

Zhai Tongsheng, chairman of Zhejiang University, said: These standards should be released this year. Most of the current LED standards are still some basic standards, and will not impose too many restrictions on LED companies. However, LED companies should pay close attention to the trend of standards; in particular, the next phase of drafting "safety", "energy efficiency", "lifetime" and environmental protection standards, these are the market access standards or certification standards for LED products, for enterprises Development has a relatively strong guiding role.



Local standards should avoid conflicts with national standards

China Lighting Network: Some areas in China have introduced local standards. For example, in Fujian Province, four local standards such as "LED lamps for general lighting", "LED lamps for landscape decoration", "LED lamps for floodlighting" and "LED lamps for road lighting" were implemented. Do you think the introduction of local standards will promote the development of local LED companies?

Zhai Tongsheng, Chairman of Zhejiang University, said: In the absence of international standards and national standards, some regions in China have introduced some local standards according to local industrial characteristics, which is an encouragement and promotion for local LED companies. The formulation of future national standards is also a reference. However, there are already relevant national standards, or basic national standards, and conflicts should be avoided when developing local standards.

China Lighting Network: How to define the relationship between local standards, industry standards and national standards for semiconductor lighting. Zhai Tongsheng, chairman of Zhejiang University, said: The local standards, industry standards and national standards for semiconductor lighting should be at different levels. National standards are more basic, common standards of various industries; industry standards are mainly oriented to the industry's characteristics of the industry; local standards are to develop product standards with local characteristics and advantages.

Focus on European and American standards and lead the development of international standards

China Lighting Network: It is understood that the "General Rules for White LED Metering for Lighting" formulated by Japan is currently the only measurement standard for white light-emitting diodes for lighting. What are the places worthy of reference for this standard?

Zhai Tongsheng, Chairman of Zhejiang University Tricolor: I don't think Japan's "General Rules for White LED Metering for Lighting" is the only measurement standard for white LEDs for lighting. Similar standards have been developed in our country, and the North American Institute of Lighting Engineers IESNA also has relevant standards. However, Japan does attach importance to the LED standard. In 2007, the Japan National Machinery Industry Federation released a 170-page LED standardization research report, which detailed analysis of the LED industry characteristics, LED optical performance, life, reliability and electrical safety evaluation methods. The impact of LED light radiation on human safety and evaluation, the requirements of LED in traffic signals and outdoor lighting, the requirements of LED in indoor lighting and special lighting, etc., are worth learning from.

China Lighting Network: In addition to Japan, in the development of LED test methods and standards, which countries in the world are ahead of us, what is their progress?

Zhai Tongsheng, Chairman of Zheda Sancolor: In terms of LED standards, we should pay attention to European Standards (EN) and North American Standards (IES). European standards are mainly for product safety standards. The European Union also promulgated the requirements for optical radiation safety in lighting applications in 2006. decree. Most of the North American IES standards are functional requirements. In 2008, the United States issued the ENERGY STAR solid-state lighting SSL test standard requirements, implementing ANSI C78.377 “Specifications for the Chromatography of Solid-State Lighting Products”, IES LM-79-08 “Measurements of Solid-State Lighting Products”, IES LM-80 "Method for Measuring Lumen Maintenance for SSL Light Sources" and other standards.

In the past two years, China's standards have developed very rapidly. In the LED international standard, China is also one of the active participating countries, and has begun to lead the formulation of international standards in certain test method standards.



China should strengthen the research of "next generation" semiconductor lighting technology

China Lighting Network: Although the LED industry has been booming, LED lighting technology is not mature. At this time, the development (promulgation) of industry standards will restrict the development of LED lighting technology?

Zhai Tongsheng, Chairman of Zheda Sancolor: The current industry standards in our country mainly refer to the standards set by the departments of transportation, railway and coal; the standards set by the Working Group of Semiconductor Lighting Technology Standards of the Ministry of Industry and Information Industry, with national standards and LED industry The two standards. At present, it is necessary to strengthen the research of industrial application product standards and formulate various application standards suitable for LED development, in order to promote the application of LED in various fields.

China Lighting Network: Developed countries such as Europe, America and Japan have developed corresponding semiconductor lighting development plans, such as the US “Energy Star”. Compared with their plans, what is the biggest highlight of China's 863 semiconductor lighting development plan?

Zhai Tongsheng, chairman of Zhejiang University, said: The United States has divided semiconductor lighting into two phases. According to the current status of the LED industry, the US Department of Energy led the organization and formulated the first phase of the five-year plan to 2012. It mainly develops several LED application products with certain application advantages, which can partially replace traditional lighting products. The next stage is not just a replacement, but a new LED lighting product and system based on the characteristics of LEDs and people's lighting needs. Many R&D institutions are starting to study future semiconductor lighting technologies; Japan has better indoor LED lighting applications. Progress, China should strengthen research on "next generation" semiconductor lighting technology.

Link: Introduction of Hangzhou Zheda Tricolor Instrument Co., Ltd.

Hangzhou Zheda Tricolor Instrument Co., Ltd. is a high-tech enterprise directly under the National University Science Park. Specializing in the research and production of spectroscopic, luminosity and colorimetric measuring instruments, electrical parameters, mechanics and temperature measuring instruments. Products are widely used in light sources, lamps, luminescent materials and display devices. In the long-term scientific research practice, the company has developed a series of unique products, and has a number of invention patents, filling the domestic gap in many fields, leading in the same industry, three-color instruments have been exported to Hong Kong, Taiwan, Europe, America, Southeast Asia, Africa and other countries and regions have become an important tool for quality testing and analysis of many internationally renowned companies, and have been widely praised by users at home and abroad.
Interview / Editor: China Lighting Network Wu Yu

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