Application and advantages of white LED in indoor lighting

　　 Semiconductor light-emitting diodes (LEDs) have a history of more than forty years. After blue LEDs appeared in the first half of the 1990s, the white LEDs were quickly solved. The advent of white light LED and its rapid development have attracted the attention of various lighting companies in the world. They have invested a lot of money and conducted fruitful research. In more than ten years, the light efficiency of white light LED has increased by nearly ten times. A new type of solid-state light source (SSL) entered the lighting field and became the third-generation new light source after the second-generation (gas discharge lamp) light source.

　　 1. The advantages of white LED

　　 White LED has appeared for nearly 15 years, and its development speed is faster than people's expectations. It is like a super-developed young "prodigy" who has received special attention and nurturing from the family and society. Its main advantages and features are:

(1) Rapid improvement of light efficiency: Up to now, the practical light efficiency of the product can reach 70-90lm/W. According to reports, the US laboratory data has reached 160lm/W, and the use will continue to increase. It is expected that in the future 3 to 5 It is possible for the practical luminous efficiency to reach 150-200lm/W by 1 year, and it may become the most efficient light source by then.

　　(2) Good starting performance, fast and reliable, only millisecond response time, can achieve full luminous output.

　　(3) Convenient dimming and strong controllability.

　　(4) Vibration resistance, good weather resistance and long life.

　　(5) Mercury-free, excellent environmental performance.

　　(6) LED radiates directionally within a certain beam angle. When it is used in spotlights, downlights and other lamps, it is beneficial to improve the downlight flux ratio.

(7) For landscape, decoration, advertising, signal and other occasions, there are a variety of colored light LEDs, coupled with good starting and dimming performance, easy to achieve digital control, in order to achieve colorful and dynamic changes, in commercial and entertainment The place is very rendering.

　　2, white LED used for indoor lighting problems to be solved

　　 White light LED is exploring and advancing in the field of lighting, and it has been continuously improved in practical applications. It has achieved a lot of achievements and promoted the development of LED lighting. The application of LED to night scene lighting has shown great advantages. However, as a functional lighting, whether in terms of products or technology, it is far from reaching the mature stage. There are many problems that need to be further solved. Of course, this is also in line with The main problems of the law of development are:

(1) LED chips mainly rely on imports, domestic chips are rarely used, high-power (1W and above) chips are not yet available, and the chips lack their own technology and intellectual property rights; my country already has a large-scale LED packaging industry with relatively excellent Equipment, but there are still gaps in packaging technology, materials and processes.

(2) There is a lack of unified standards, including LED lighting systems, drive circuits, etc. Some companies have used their advantages to research and develop their own products, and some have borrowed or imitated. The product level varies, and the scale of each product is different, and they are interchangeable. Poor sex, difficult to maintain.

　　(3) The test method of LED lighting is not uniform, and the test of some parameters is yet to be studied, such as the measurement of color rendering and the gas discharge lamp are not necessarily the same.

　　(4) LED lighting products are still in its infancy, technically immature, and there are still many problems, such as:

　　1) Heat dissipation problem: How to effectively reduce the junction temperature to the allowable level is still being explored and practiced. Poor temperature control will affect the light efficiency, increase the light flux attenuation, and even stabilize the color temperature and color rendering.

　　2) At present, most LEDs have a high color temperature and excessive blue spectrum. For most indoor places, it will make people feel uncomfortable, produce irritation, not coordinate with the environment, and the light is not soft enough, which is not conducive to eye protection.

3) LED is used as indoor functional lighting. How to design the light distribution and light control system of lamps is also a new topic. Directional LEDs are different from existing light sources. The reflection, diffusion and light distribution of lamps have their own Features.

　　4) LED lighting drive circuit: It also needs further optimization and standardization, and it takes time. Its performance, including service life, power consumption, harmonics, power factor, etc., needs to be explored.

(5) The price is too high, which is another obstacle to popularization. Relying on government subsidies alone is not a good strategy for development. Using LEDs to replace low-efficiency light sources such as incandescent lamps has significant energy-saving effects and can enjoy subsidies; compared with three-primary-color straight tubes More efficient light sources such as fluorescent lamps have no energy-saving effect (at least today), and the excessive initial construction costs are by no means economically reasonable.

　　(6) Another problem of LED lighting is the lack of a stable and orderly development trend. In just a few years, thousands of companies have squeezed into LED lighting, and there is a rush, reminding people of the "Great Leap Forward" era. Some companies make in imitation, low-level repetition, relying on exaggeration to enter the market, some companies merge with some media, overhype, exaggerate the energy-saving effect, and even individual government officials have played a role in fueling the flames and misled the users. It is necessary to establish a complete set of technical standards and an objective evaluation mechanism, and a pragmatic public opinion orientation to guide its healthy development.

　　3. The role of LEDs in indoor lighting

　　3.1 Principles and directions of application

Indoor lighting is different from night lighting, and emphasizes the function of lighting; compared to road lighting, it is a broader space. Different places of use, different functions, different sizes of places, and different decorative aesthetic requirements determine the interior There are many types of lighting fixtures and different light distribution types. At present, hundreds of companies are flocking to street lights. They should broaden their horizons, change their thinking, and enter the wider world of indoors.

　　Walking into the room, what to do first, and from which areas to break through, it is recommended to consider the following principles and directions.

　　(1) First of all, it should meet the requirements of "Architectural Lighting Design Standards", including requirements for illuminance, uniformity, glare, color rendering index and appropriate color temperature, in order to achieve good visual conditions and LPD limits.

　　(2) Choose places, pilot applications, gradually expand, step by step, sum up experience, continue to improve, and avoid disregarding the target, not analyzing the conditions, and promoting it on a large scale. We should find places where we can give full play to our own advantages as an entry point.

　　 (3) Highlight energy saving: The current goal is to replace low-efficiency incandescent lamps and give full play to its advantages; the second goal is to replace halogen lamps; and the third is to gradually replace compact fluorescent lamps. Special attention: not all LEDs are energy-saving, they should be compared under the same illumination level and similar lighting quality conditions; from this point of analysis, LEDs should not be used to replace high-efficiency three-primary-color straight fluorescent lamps.

　　(4) Leverage the advantages of LED colored light and use it indoors where higher decoration requirements are required, or as a landscape or sign light.

　　(5) Give full play to the advantages of LED's quick start and convenient dimming, and preferentially use it in places requiring automatic control of sound and light, dimming or frequent switching of lights.

　　(6) Using the characteristics of LED directional light emission, it is applied to parts that need directional lighting, such as spotlights, downlights, etc.

　　3.2 Suitable places for application

　　 According to the above principles, the following places are suitable for application or trial.

(1) The stairwells and walkways of residences or similar places are equipped with energy-saving self-extinguishing lamps. Almost all use incandescent lamps. LEDs are the most suitable replacement. The energy-saving effect is good. Although it is only a "small lamp", the number is large. It is estimated that over 100 million pieces, its energy-saving benefits are considerable, and the economic benefits of the enterprise are significant.

　　(2) Evacuation lights, evacuation sign lights, and other sign lights, as well as some spare lights (when HID lights are used for normal lighting), LEDs are suitable.

(3) It is very suitable to replace the 5 types of PAR38 (reflective incandescent lamps) with LEDs; further study to replace MR16, MR25 (halogen lamps) and other types of spotlights; these should require LEDs to have a higher color rendering index (Ra) and has a warm color table (<3300K).

　　(4) Spotlights used in shopping malls for key lighting, spotlights for exhibition halls, and tube and spotlights for public buildings.

(5) Hotels use more incandescent lamps and halogen lamps, which are suitable places for the application of LED lamps, which can be used to replace incandescent lamps and halogen lamps: bedside lamps that need to be dimmed in the guest room, reading lamps on the bedside, and night lamps. , Wardrobe lights, bar lamps, door opening lights, door aisle lights, and bathroom shower lights.

　　(6) Local lighting, using safety extra low voltage (SELV) inspection lights.

　　(7) Auxiliary places for general buildings that require low visual conditions, such as walkways, toilets, general-purpose warehouses, fans, pump rooms, etc.

　　3.3 Need to study application places

　　(1) The crystal glass chandeliers in places with high decorative requirements (hotels, etc.) now use candle-shaped incandescent lamps. It should be studied to replace LEDs that can achieve similar effects, and research from the effects of color temperature, spectrum and color rendering.

　　 (2) In halls, multi-function halls and other similar places that need dimming, incandescent lamps should be used instead of LEDs.

　　3.4 Places that currently do not have the conditions to apply LED

　　(1) Such places mainly include offices, classrooms, general lighting in shopping malls, control rooms, and various industrial places (such as meters, electronics, textiles, clothing, cigarettes, etc.).

(2) This kind of place lighting is mainly functional lighting, which requires high color rendering, suitable color temperature, better glare control, and good uniformity to ensure a good visual environment, while requiring high lighting energy efficiency; now used Three-primary-color straight tube fluorescent lamps (not less than 4 feet long) have high luminous efficiency and good visual effects. The current LEDs are still difficult to meet these requirements, so it is not suitable for use. You can study the preparation conditions and how to use light distribution lamps to adapt.

　　 4. Future prospects

　　LED is still under continuous development, the indoor lighting space is vast, and the future application prospects are bright. However, there must be greater progress and corresponding research and exploration work to create conditions for application.

　　(1) Further improve light efficiency and color rendering, and study a variety of more suitable color temperatures.

　　(2) The semiconductor discipline and the lighting discipline are more organically combined, and the luminaire form and luminaire light distribution system suitable for the characteristics of LED are studied in depth.

　　(3) Further reduce costs.

　　 It is expected that in 5-10 years, LED will be widely used in the field of indoor functional lighting.

While paying attention to the development and application of LEDs, it should also be noted that another solid-state light source-organic semiconductor light-emitting diodes (OLED) is also quietly emerging, has begun to show more advantages, and may become an existing light source in the next few years. A strong competitor of LED, we need more attention.