LED indoor lighting applications and prospects

Abstract This paper describes the development of white LED and has the advantage, and the current application of lighting in the area a number of problems, analysis of the principles of indoor lighting applications and fields, assess the prospects for future years.
Key words Tricolor fluorescent indoor lighting LED color temperature color-rendering index
Semiconductor light-emitting diode (LED) has forty years of history, to the first half of the nineties of last century of blue LED appears soon after the successful resolution of the white light on the LED. The advent of white LED and its rapid development has been the concern of the world's lighting business, invested a lot of money, carried out fruitful research, twelve years, the white LED light efficiency increased nearly tenfold, as a new solid light (SSL) into the lighting field, becoming the second-generation (gas discharge lamps) light sources beyond the third generation of a new light.
1 advantage of white LED
White LED in nearly 15 years, and its rapid development, more than people expect, like a teenager extraordinary development, "child prodigy" by the family and society, special attention and nurturing. The main advantages and characteristics are:
(1) rapid increase in luminous efficiency: up to now, the product of practical optical efficiency up to 70 ~ 90lm / W, according to reports, the U.S. laboratory data up to 160lm / W, while still increasing with the trend expected in the next 3 to 5 , the practical effect of light to reach 150 ~ 200lm / W is possible, then there may be the most efficient light sources.
(2) starting performance, fast and reliable, only millisecond response time, can reach full lumen output.
(3) dimming easy controllable.
(4) Shock, good weather resistance, long life.
(5) does not contain mercury, superior environmental performance.
(6) LED beam angle at a certain orientation within the radiation, for spotlights, downlights and other lamps, will help improve the next shot lumen ratio.
(7) for the landscape, decoration, advertising, signals and so on, a variety of colored light LED, with a good start and dimming performance, easy to implement digital control to achieve the colorful, dynamic changes in the commercial, entertainment great rendering of place.
2 white LED for interior lighting problems to be solved
White LED lighting in the area exploring the way forward, in practice continuous improvement has been made a lot of achievements, promote the development of LED lighting. LED used in landscape lighting, has shown a lot of advantages, but as functional lighting, whether in product or technology, but also far from reaching a mature stage, there are many problems to be solved, of course, this is also consistent with the law of development, the problems are:
(1) LED chip is mainly dependent on imports, with domestic chip small, high-power (1W or more) chips do not, the lack of its own chip technology and intellectual property; China has a very large-scale LED packaging industry, with more good equipment, but the packaging technology, materials and processes, there is still a gap.
(2) lack of uniform standards, including LED lighting system, the driving circuits, some companies play to their strengths, their own product research and development, while others draw or imitation, the level of good and bad products, individual products, scales, and exchange poor maintenance difficulties.
(3) LED lights there is no uniform testing methods, some parameters of the test has to be studied, such as color measurement and the gas discharge lamp is not necessarily the same.
(4) LED lighting products at an early stage, technically immature, there are still many problems, such as:
1) The heat problem: how to effectively reduce the junction temperature to the permissible level, is still exploring and practice, temperature control is not good, will affect the light efficiency, plus bare-pass attenuation, and even color temperature, color stability.
2) The majority of high color temperature LED's, too much blue spectrum, for most indoor places, will make people feel uncomfortable, resulting in irritation, and the environment is not enough coordination, insufficient light, soft, not conducive to eye protection.
3) LED for indoor functional lighting, how to design a lighting system with light and control light, but also a new topic, the LED directional light is different from the existing light source, light reflection, diffuse, with light, has its own characteristics.
4) LED lighting driver circuit: but also to further optimization and standardization, but also take time, its performance, including life, power, harmonics, power factor, etc., need to be explored.
(5) the price is too high, another obstacle is the application alone, government subsidies, not a good policy development, such as inefficient use LED instead of incandescent light sources, a significant energy savings can be subsidized; and relatively straight tricolor these more efficient fluorescent lighting, and no energy-saving effect (at least today is the case), the high initial construction costs, absolutely no economic rationality.
(6) LED lighting Another problem is the lack of stable and orderly development of the situation. Just a few years, thousands of companies to squeeze into the LED lighting, a herd of posture, reminiscent of the "Great Leap Forward" years. There are some enterprises in the production of imitation, low repetition, by exaggerating the market, some companies and some media convergence, too much hype, exaggerated energy-saving effect, and even some government officials are taking to the waves role in misleading the use of units. Must establish a complete set of technical standards and objective evaluation mechanism, seeking truth from facts of public opinion, and guide the healthy development.
3 LED's role in indoor lighting
3.1 Application of the principles and directions
Unlike indoor lighting landscape lighting, more emphasis on the function of lighting; relative to street lighting, said it is a wider space, the use of different places, different functions, different size spaces, different decorative aesthetic requirements, determine the indoor wide variety of lighting fixtures, with different types of light, hundreds of companies flocking to the lamp current situation, should broaden their horizons, change thinking, into the interior of this wider world.
Go inside, do first, from the areas in which breakthroughs, it is recommended to consider the following principles and direction.
(1) must first comply with "Architectural lighting design" provision, including illumination, uniformity, glare, color rendering index requirements and the appropriate color temperature, in order to achieve good visual conditions and provisions of LPD limits.
(2) should choose the place, pilot applications, and gradually expanded, step by step, sum up experience, continuous improvement, should not disregard the object, not of conditions, large area. Should find a better place to play to their strengths as a starting point.
(3) to highlight the energy saving: The current first goal is to replace inefficient incandescent lamps, more advantages; second objective is to replace the halogen; the third is to try to gradually replace the compact fluorescent lamps. Special Note: Not all energy-saving LED should be to achieve the same illumination level in close to the quality of lighting conditions can be compared; From this analysis, the current should not be efficient LED to replace the three primary colors straight tube fluorescent lamps.
(4) to play the advantages of LED colored light, in the interior decoration for the need for higher requirements, or as a landscape, lights and so on.
(5) to play a quick start LED, the advantages of easy dimming, first used in the requirements of sound, light and self-control and the need for dimming or frequent switching lights and other places.
(6) the use of LED directional light features, applications that require directional lighting the site, such as lighting, down light and so on.
Appropriate place for application of 3.2
According to the above principles, the following locations suitable for application or trial.
(1) residential or similar places of the stairs, the hallway light switch installing energy-saving self-extinguishing, almost incandescent, LED instead of using the most appropriate, energy-saving effect, although only a "little light", but the large number of national estimated expenditure of billions of dollars, and its impressive energy efficiency, companies with significant economic benefits.
(2) evacuation lighting, evacuation lights and other lights, there are some spare lights (when the normal lighting using HID lamps), suitable to use LED.
(3) instead of using LED PAR38 (by reflective incandescent) lights the 5 categories, it is very appropriate; further study instead of MR16, MR25 (with halogen) spotlights a class; these should require a higher color rendering index LED (Ra) and a warm table (<3300K).
(4) used in shopping malls in the spotlight for accent lighting, architectural lighting Bo Hall class, and public buildings of the cylinder, lighting and so on.
(5) The use of incandescent and halogen lamps are more hotels, is the application of suitable sites LED lights can be used to replace incandescent lamps, halogen lamps are: rooms to be dimming bedside lamps, bedside reading light on top, nightlights , closet lights, bar lamps, door lamps, door, aisle lights, bath lights, and bathroom.
(6) local lighting, the use of the safety extra low voltage (SELV) the maintenance of lights.
(7) visual conditions less demanding general construction of the auxiliary spaces such as corridors, toilets, general-purpose warehouse, fans, water pump house and so on.
3.3 The need for research and application areas
(1) decoration for high places (hotels, etc.) of the crystal glass chandeliers, candle-shaped incandescent lamps are now used, should be studied to achieve a similar effect of the LED replacement, from the color temperature, spectral and color and other effects were studied.
(2) require dimming the auditorium, function rooms and other similar places, and now with the incandescent lamp, should study the use of LED instead.
3.4 Application of LED current conditions do not have a place
(1) such establishments are offices, classrooms, shopping malls and the general lighting, control room, all kinds of industrial sites (such as instruments, electronics, textiles, clothing, cigarettes, etc.).
(2) of such places lighting is mainly functional lighting, requiring high color rendering, color temperature affordable, good glare control, uniformity is good, in order to ensure good visual environment, but requires a high efficiency lighting; now use trichromatic straight tube fluorescent lamps (not less than 4 feet long), and its high luminous efficiency, visual effects, the current LED is also difficult to meet these requirements, it should not be used for preparation of the study conditions, how the light distribution with the form of lamps to meet .
4 Future prospects
LED is constantly evolving, indoor lighting is vast, and the future prospects are bright. But the forward and the corresponding need for greater research, exploration work and to create conditions for the application.
(1) further improve the light efficiency and color rendering, color temperature of a variety of more suitable.
(2) Subject to the semiconductor and lighting is more organic integration of disciplines, in-depth study characteristics for LED lighting and lamps with the form of optical systems.
(3) to further reduce costs.
Expect 5 to 10 years or so, LED lighting in the interior features to wider application areas.
Concerned about the development of LED application at the same time, it should be noted that another solid source - organic light emitting diode (OLED) is also quietly rising, has begun to show more advantages, perhaps in the coming years as existing light sources and the LED strong competitors, we need more attention.