Local dips in the emission spectrum of LED lamps. Plant lighting with white LEDs. Phosphor LED design

Houseplants do not always have enough light at home. Without this, their development will be slow or incorrect. To avoid this, you can install LEDs for plants. It is this lamp that can provide the required spectrum of color. widely used for lighting greenhouses, conservatories, indoor gardens and aquariums. They replace sunlight well, do not require large expenditures and have a long service life.

Plant photosynthesis is a process that occurs with sufficient light. The following factors also contribute to the correctness: ambient temperature, humidity, light spectrum, length of day and night, carbon sufficiency.

Determining the sufficiency of light

If you decide to install lamps for plants, then you need to do it as correctly as possible. To do this, you need to decide which plants lack the ray, and which will be superfluous. If you are designing lighting in a greenhouse, then you need to provide zones with different spectrums. Next you need to determine the number of LEDs themselves. Professionals do this with a special device - a lux meter. You can also make the calculation yourself. But you will have to dig a little and design the desired model.

If the project is being done for a greenhouse, there is one universal rule for all types of light sources. When the height of the suspension increases, the illumination decreases.

LEDs

The spectrum of color radiation is of great importance. The optimal solution would be red and blue LEDs for plants in a two to one ratio. How many watts the device will have doesn't really matter.

But more often they use one-watt ones. If you need to install diodes yourself, it is better to purchase ready-made tapes. You can secure them with glue, buttons or screws. It all depends on the holes provided. There are a lot of manufacturers of such products; it is better to choose a well-known, rather than a faceless seller who cannot give a guarantee for his product.

Light wavelength

The spectrum of natural sunlight contains both blue and red colors. They allow plants to develop mass, grow and bear fruit. When irradiated only with a blue spectrum with a wavelength of 450 nm, the representative of the flora will be stunted. Such a plant cannot boast of a large green mass. It will also bear fruit poorly. When absorbing the red range with a wavelength of 620 nm, it will develop roots, bloom well and bear fruit.

Pros of LEDs

When a plant is illuminated, it goes all the way: from sprout to fruit. At the same time, during this time, only flowering will occur when the luminescent device is operating. LEDs for plants do not heat up, so there is no need to frequently ventilate the room. In addition, there is no possibility of thermal overheating of flora representatives.

Such lamps are irreplaceable for growing seedlings. The directionality of the radiation spectrum helps the shoots to grow stronger in a short time. Low energy consumption is also a plus. LEDs are second only to But they are ten times more economical LEDs for plants last up to 10 years. - from 3 to 5 years. Having installed such lamps, you will not have to worry about replacing them for a long time. Such lamps do not contain harmful substances. Despite this, their use in greenhouses is very preferable. The market today presents a large number of different designs of such lamps: they can be hung, mounted on a wall or ceiling.

Minuses

To increase the radiation intensity, LEDs are assembled into a large structure. This is a disadvantage only for small rooms. In large greenhouses this is not significant. The disadvantage can be considered the high cost compared to analogues - fluorescent lamps. The difference can reach eightfold. But diodes will pay for themselves after several years of service. They can significantly save energy. A decrease in glow is observed after the warranty period expires. With a large greenhouse area, more lighting points are needed compared to other types of lamps.

Radiator for lamp

It is necessary that heat is removed from the device. This would be better done by a radiator made of aluminum profile or steel sheet. The use of a U-shaped finished profile will require less labor. Calculating the radiator area is easy. It must be at least 20 cm 2 per 1 Watt. After all the materials have been selected, you can assemble everything into one chain. It is better to alternate LEDs for plant growth by color. This will ensure uniform lighting.

PhytoLED

The latest development, such as phyto-LED, can replace conventional analogues that glow in only one color. The new device combines the necessary spectrum of LEDs for plants in one chip. It is needed for all stages of growth. The simplest phytolamp usually consists of a block with LEDs and a fan. The latter, in turn, can be adjusted in height.

Fluorescent lamps

Fluorescent lamps have long remained at the peak of popularity in household gardens and vegetable gardens. But such lamps for plants do not fit the color spectrum. They are increasingly being replaced by phyto-LED or special-purpose fluorescent lamps.

Sodium

A light as strong in saturation as that of a sodium apparatus is not suitable for placement in an apartment. Its use is advisable in large greenhouses, gardens and greenhouses where plants are illuminated. The disadvantage of such lamps is their low performance. They convert two-thirds of the energy into heat and only a small part is used for light radiation. In addition, the red spectrum of such a lamp is more intense than the blue one.

We make the device ourselves

The easiest way to make a lamp for plants is to use a strip with LEDs on it. We need it in the red and blue spectra. They will connect to the power supply. The latter can be purchased in the same place as tapes - at a hardware store. You also need a fastening - a panel the size of the lighting area.

Manufacturing should begin by cleaning the panel. Next, you can glue the diode tape. To do this, remove the protective film and stick the sticky side to the panel. If you have to cut the tape, then its pieces can be joined using a soldering iron.

LEDs for plants do not require additional ventilation. But if the room itself is poorly ventilated, then it is advisable to install the tape on a metal profile (for example, made of aluminum). Lighting modes for flowers in a room can be as follows:

• for those growing far from the window, in a shaded place, 1000-3000 lux will be enough;
• for plants that need diffused light, the value will be up to 4000 lux;
• representatives of the flora that need direct lighting - up to 6000 lux;
• for tropical and those that bear fruit - up to 12,000 lux.

If you want to see indoor plants in a healthy and beautiful form, you must carefully satisfy their need for lighting. So, we have found out the advantages and disadvantages for plants, as well as the spectrum of their rays.

The massive appearance of LED lamps on the shelves of hardware stores, visually reminiscent of an incandescent lamp (base E14, E27), has led to additional questions among the population about the advisability of their use. Advertisers claim unprecedented energy performance, a working life of several decades, and the most powerful luminous flux of innovative light sources. Research centers, in turn, put forward theories and present facts indicating the dangers of LED lamps. How far have lighting technologies come, and what is the other side of the coin called “LED lighting”?

What is fact and what is fiction?

Several years of using LED lamps allowed scientists to draw the first conclusions about their true effectiveness and safety. It turned out that such bright light sources as LED lamps also have their “dark sides”. The negativity was added by our Chinese colleagues, who, once again, flooded the market with low-quality products. Which lighting should you prefer so as not to worsen your vision in the pursuit of energy efficiency? In search of a compromise solution, you will have to become more familiar with LED lamps.

The design contains harmful substances

To make sure that an LED lamp is environmentally friendly, just remember what parts it consists of.
Its body is made of plastic and a steel base. In powerful samples, a radiator made of aluminum alloy is located around the circumference. A printed circuit board with light-emitting diodes and radio driver components are fixed under the bulb. Unlike energy-saving fluorescent lamps, the bulb with LEDs is not sealed or filled with gas. Based on the presence of harmful substances, LED lamps can be placed in the same category as most electronic devices without batteries. Safe operation is a significant advantage of innovative light sources.

White LED light is harmful to your eyesight

When you go shopping for LED lamps, you need to pay attention to the color temperature. The higher it is, the greater the intensity of radiation in the blue and cyan spectrum. The retina of the eye is most sensitive to blue light, which over long periods of repeated exposure leads to its degradation. Cold white light is especially harmful to children's eyes, whose structure is still developing.

To reduce visual irritation, it is recommended to include low-power incandescent lamps (40–60 W) in lamps with two or more sockets, as well as use LED lamps that emit warm white light. The use of such lamps without a high pulsation coefficient does not cause harm and is approved by the Ministry of Health of the Russian Federation. The color temperature (Tc) is indicated on the packaging and should be in the range of 2700–3200 K. Russian manufacturers Optogan and SvetaLed recommend purchasing warm-colored lighting fixtures, since their emission spectrum is most similar to sunlight.

Flicker strongly

The harm of pulsations from any artificial light source has long been proven. Flickers with a frequency of 8 to 300 Hz negatively affect the nervous system. Both visible and invisible pulsations penetrate through the organs of vision into the brain and contribute to poor health. LED lamps are no exception. However, it's not all bad. If the driver output voltage additionally undergoes high-quality filtering, getting rid of the variable component, then the ripple value will not exceed 1%.
The ripple coefficient (Kp) of lamps in which a switching power supply is built-in does not exceed 10%, which satisfies the sanitary standards in force in the Russian Federation. The price of a lighting device with a high-quality driver cannot be low, and its manufacturer must be a well-known brand.

Suppress melatonin secretion

Melatonin is a hormone responsible for sleep frequency and regulating the circadian rhythm. In a healthy body, its concentration increases with the onset of darkness and causes drowsiness. Working at night, a person is exposed to various harmful factors, including lighting. As a result of repeated studies, the negative impact of LED light at night on human vision has been proven.

Therefore, with the onset of darkness, you should avoid bright LED radiation, especially in bedrooms. Lack of sleep after prolonged viewing of LED TV (monitor) is also explained by a decrease in melatonin production. Systematic exposure to the blue spectrum at night provokes insomnia. In addition to regulating sleep, melatonin neutralizes oxidative processes, which means it slows down aging.

There are no standards for LED lamps

This statement is partially erroneous. The fact is that LED lighting is still developing, which means it is gaining new pros and cons. There is no individual standard for it, but it is included in a number of current regulatory documents that provide for the influence of artificial lighting on humans. For example, GOST R IEC 62471–2013 “Photobiological safety of lamps and lamp systems.”
It describes in detail the conditions and methods for measuring the parameters of lamps, including LEDs, and provides formulas for calculating the limit values ​​of dangerous exposure. According to IEC 62471–2013, all continuous wave lamps are classified into four eye hazard groups. Determination of the risk group for a specific type of lamp is carried out experimentally based on measurements of dangerous UV and IR radiation, dangerous blue light, as well as thermal effects on the retina.

SP 52.13330.2011 establishes regulatory requirements for all types of lighting. In the “Artificial Lighting” section, due attention is paid to LED lamps and modules. Their operating parameters must not exceed the permissible values ​​provided for in this set of rules. For example, clause 7.4 indicates the use of lamps with a color temperature of 2400–6800 K and a maximum permissible UV radiation of 0.03 W/m2 as sources of artificial lighting. In addition, the value of the pulsation coefficient, illumination and luminous efficiency is normalized.

Emit a lot of light in the infrared and ultraviolet range

To understand this statement, you need to analyze two methods of producing white light based on LEDs. The first method involves placing three crystals in one case - blue, green and red. The wavelength they emit does not extend beyond the visible spectrum. Consequently, such LEDs do not generate luminous flux in the infrared and ultraviolet range.

To obtain white light in the second way, a phosphor is applied to the surface of a blue LED, which generates a luminous flux with a predominant yellow spectrum. As a result of mixing them, you can get different shades of white. The presence of UV radiation in this technology is negligible and safe for humans. The intensity of IR radiation at the beginning of the long-wave range does not exceed 15%, which is disproportionately low with the same value for an incandescent lamp. The talk about applying a phosphor to an ultraviolet LED instead of a blue LED is not unfounded. But for now, producing white light using this method is expensive, has low efficiency and many technological problems. Therefore, white lamps based on UV LEDs have not yet reached industrial scale.

Have harmful electromagnetic radiation

The high-frequency driver module is the most powerful source of electromagnetic radiation in an LED lamp. The RF pulses emitted by the driver can affect the operation and degrade the transmitted signal of radio receivers and WIFI transmitters located in close proximity. But the harm from the electromagnetic flux of an LED lamp for a person is several orders of magnitude less than the harm from a mobile phone, microwave oven or WIFI router. Therefore, the influence of electromagnetic radiation from LED lamps with a pulse driver can be neglected.

Cheap Chinese light bulbs are harmless to health

Partially the answer to this statement has already been given above.
Regarding Chinese LED lamps, it is generally accepted that cheap means poor quality. And unfortunately, this is true. Analyzing the product in stores, it can be noted that all LED lamps costing less than 200 rubles apiece have a low-quality voltage conversion module. Inside such lamps, instead of a driver, a transformerless power supply unit (BP) with a polar capacitor is installed to neutralize the alternating component. Due to the small capacity, the capacitor copes with its assigned function only partially. As a result, the pulsation coefficient can reach up to 60%, which can negatively affect a person’s vision and health in general.
There are two ways to minimize the harm from such LED lamps. The first involves replacing the electrolyte with an analogue with a capacity of about 470 uF (if free space inside the case allows). Such lamps can be used in the corridor, toilet and other rooms with low visual stress. The second is more expensive and involves replacing a low-quality power supply with a driver with a pulse converter. But in any case, it is better to use decent LED lamps for lighting living rooms and workplaces, and it is better to refrain from purchasing cheap products from China.

Reviews from experts

Experts who study the operation of light-emitting diodes argue that the harm of LED lamps is greatly exaggerated. But until the problem of blue light is solved, when choosing LED lamps you should pay attention to the color temperature (Tc). If the box indicates a value of 4 thousand K or more, then it is better to refuse to purchase such lamps for an apartment. Their purpose is to illuminate streets and industrial facilities. Light sources with Тс=3000–4000 K are recommended as the main lighting in the apartment, except for bedrooms. For living rooms and rest rooms, you should choose LED lamps with Tc = 2500–3000 K, simulating the warm light from an incandescent lamp.

To completely switch to LED lighting or, conversely, to completely abandon it is an individual choice for each person. Technologies make it possible to further modernize the LED, and developers predict a great future for it. Now the man finds himself at about two ends of the scale. On the same scale is commerce, which very effectively imposes imperfect goods in large quantities. On the other side are the warnings of scientists who are seeking stricter standards for the use of super-bright white LEDs.

Use quality LED lighting and remember to walk for at least one hour every day in sunlight. For children whose vision is still developing, this figure should be increased by 2–3 times. You should also avoid direct light from the LED lamp. This statement applies to any light source.

ledjournal.info

Why can LED light be harmful to your eyesight?

Scientists have found that not all LED radiation as a whole has a harmful effect on the organs of vision, but only the blue and violet components of the spectrum, which have the shortest wavelength and, accordingly, higher frequency and higher energy. Spanish scientists who conducted such studies published their reviews in the journal Seguridad y Medio Ambiente. The main results of this research work are the following statements:

• LED light sources can cause irreparable harm to the health of humans and animals by affecting the retina of the eye.
• Short-wave blue and violet light causes damage.
• Radiation causes three types of injuries to the retina: photomechanical (impact energy of a wave of light energy), photothermal (during irradiation, tissue tissue is heated) and photochemical (photons of light can cause chemical changes in macromolecules).
• Green and white light have much less phototoxicity, and no negative changes were found when the retina was exposed to red light.

The results of the study suggest that looking at a bright LED lamp is contraindicated.

But this safety rule can also be applied to other sources of bright light: incandescent lamps and fluorescent lamps. Thus, the harm of energy-saving lamps to the eyes consists of a negative effect on the retina. However, most leading manufacturers supply lamps with diffusers, or good chandeliers have shades that provide soft diffused light, the benefits of which are much higher.

Classification of lighting according to risk level

An international standard has been adopted to assess the safety of visible light radiation EN 62471, which is called “Photobiological safety of lamps and lamp systems.” In accordance with this standard, four risk groups are identified, which indicate the maximum time of exposure to lighting from the light source under study.

• Zero risk group (no risk). Exposure to radiation from such light sources can last for 10,000 seconds or more.
• First risk group (low risk). The maximum exposure time can be from 100 to 10,000 seconds.
• The second risk group (moderate risk). The maximum exposure time for luminaires of this group is possible from 0.25 to 100 seconds.
• Third risk group (high risk). The exposure time should not exceed 0.25 seconds.

A study was conducted based on this standard. Institute of Health and Medical Research Professor Francine Behar-Cohen led a team of scientists who, as a result of research, came to some important conclusions, by making your comments about the dangers and benefits of LED lamps:

• A blue LED with a power of 15 W or more can be classified as the third risk group.
• A blue LED with a power of 0.07 W belongs to the first risk group.
• Compared to traditional incandescent lamps, which belong to the zero or first risk group, LED lighting can be classified as the second group.
• At the same color temperature, the emission of white LEDs contains 20% more of the dangerous blue component of the spectrum.

LED lamps and suppression of melatonin secretion

A team of scientists from Israel, the USA and Italy conducted a study of the effect of various artificial light sources on the production of an important hormone - melatonin, which is produced in humans and higher animals in the pineal gland. This hormone is responsible for sleep frequency, blood pressure, and is involved in the functioning of brain cells.

Melatonin is a powerful antioxidant, it slows down the aging process and activates the immune system.

Scientists used the light of high-pressure sodium lamps, which have a warm yellow color, as a model. It was found that halogen lamps, which have a higher color temperature, suppress the secretion of melatonin by three times. During the study, it was noticed that the suppression of secretion occurs five times stronger, with the same power of sodium and LED lamps.

It turned out that it is the bright light of the blue spectrum that has such a detrimental effect. Italian physicist Fabio Falchi argues that exposure to any powerful light source in the evening, when the body should be preparing for sleep, is contraindicated, especially fluorescent and LED lamps, the spectrum of which contains blue and violet components of the spectrum .

• It is better to use incandescent lamps for lighting bedrooms.
• Avoid looking at any bright light sources 2-3 hours before bedtime.
• When working at a computer in the dark, use special glasses that block the blue spectrum of lamps.
• It is better to use red lighting as night lighting.
• Use only high-quality LED lamps from well-known manufacturers that have a “warm” white color temperature and a high color rendering index.
• Use chandeliers and lamps specifically designed for LED lamps. More about this in this article.

Flickering lamps and its effect on vision

It is known that incandescent lamps operating in our AC networks of 220 V, 50 Hz flicker at a frequency of 100 Hz. Energy-saving lamps equipped with conventional ballasts also flicker at the same frequency, while lamps equipped with electronic ballasts (electronic ballasts) may flicker at a lower frequency. The inertia of the human eye does not allow us to see pulsations in the glow of lamps, but as studies have shown, the human brain perceives pulsations up to a frequency of 300 Hz. These fluctuations in energy-saving lamps harm the human psyche, change hormonal levels, reduce performance, increase fatigue, and change natural circadian rhythms.

The emission of an LED occurs when direct current flows through it, and the alternating mains voltage is converted into constant voltage by a special circuit - the driver, which is equipped with all lamps. True, most drivers convert alternating mains voltage not into direct current, but into a series of direct current pulses. So, firstly, it is easier to implement the circuit, and, secondly, it makes it possible to dim the lamps, that is, change the brightness by changing the duty cycle of the pulses. Read how to choose a dimmer here. In high-quality lamps from well-known manufacturers, the pulse repetition rate is more than 300 Hz, which practically reduces the pulsation of lighting from such lamps to zero.

Emission spectrum of LED lamps

An LED produces radiation when holes and electrons in semiconductors recombine to produce a photon of light. The frequency of radiation is determined by the chemical composition of semiconductors. Radiation can be either in the invisible range (infrared or ultraviolet) or in the visible range (red, orange, yellow, green, blue, violet, white).

LED emission occurs in a very narrow range, so the spectrum of such radiation is lined, which negatively affects color rendering parameters.

Another disadvantage of LED lighting is that the generated radiation is coherent, that is, the same frequency and fixed phase shift. Undiffused LED light has a certain “hardness,” but manufacturers find a way out by using diffusers on lamps or shades in chandeliers. These measures significantly reduce the “hardness” of its radiation.

It should be noted that there is currently no semiconductor crystal that emits white light, although white LEDs do exist. White color can be obtained in two ways:

• The first method is a combination of three LEDs: red, green and blue. Such LEDs exist, but their emission spectrum is very linear, which affects the color rendering index. They have found application more in LED displays, where the color of the display pixel can be adjusted by the intensity of a certain color. Such combined LEDs are rarely used in lighting.
• The second way is to use the photoluminescence effect. When special substances - phosphors - are irradiated, they re-emit light, only in a different range. This effect has long been used in fluorescent lamps, when the ultraviolet glow of a gas discharge is transformed by phosphors deposited on the inner surface of the lamp bulb. And the spectrum depends on the quality of the phosphor. White LEDs use emitters in the blue, violet or ultraviolet range and a phosphor that is responsible for light in the desired range, the desired color temperature and the desired color rendering index.

The spectral composition, color temperature and color rendering index depend on the quality and quantity of the phosphor in white LEDs. A combination of phosphors is used, the higher quality they are and the more there are, the richer the spectrum, but also the more expensive the lamp. And the development of LED lighting occurs in parallel with the development of the use of different phosphors. Naturally, the emission of white LEDs contains either a blue, or violet, or ultraviolet component of the spectrum, which carries certain harm, so you must follow certain precautions described earlier.

Thermal radiation of LED lamps

Any sources of artificial light have thermal radiation, including LED lamps. But if in incandescent lamps the glow of the filament occurs due to the high temperature of the filament, then with LEDs there is an almost direct conversion of electric current into light energy. Naturally, the current causes heating of the semiconductor crystal, but the need to cool it is more due to the need to preserve its properties and extend its service life, since already at temperatures of 60-80°C accelerated degradation of the semiconductor occurs.

White bright LEDs are necessarily equipped with radiators for cooling, but the thermal radiation itself from such lamps is very small compared to incandescent lamps.

Any heated body, as is known from physics courses, emits infrared rays, but in the case of LED lamps it is negligible compared to incandescent lamps. That is why LED lighting is now replacing the lighting of television studios and stage areas, where halogen and metal halide lamps were previously used.

Electromagnetic radiation from LED lamps

LED lamp drivers are an electronic circuit that generates high-frequency pulses, so the operation of these devices creates electromagnetic interference that can disrupt the operation of some electronic devices: FM receivers, televisions and other devices. Therefore, the minimum distance from the lamp to another device should be at least 40 centimeters.

What LED lamps can you buy for your home?

Based on all of the above, we can draw certain conclusions about the appropriateness of using LED lamps.

• In terms of energy saving and luminous efficiency, LED lamps are the most efficient light sources with prospects for widespread implementation.
• All high-power artificial light sources can have a negative impact on human health, primarily through their effect on the retina. If simple safety precautions are followed, LED lamps do not have a harmful effect.
• When purchasing LED lamps, you should trust only well-known global brands, and the purchase should be made only from reputable sellers.
• For home use, it is better to use lamps with a light temperature of 2700-3200 K (warm white). The color rendering index must be at least 80 CRI.
• The use of more advanced phosphors in the production of white LEDs will only improve the characteristics of LED lamps, including their safety.

www.indeolight.com

Sources of harm to health

To prove or disprove the harm of LED lamps to health, we will determine the sources of damage to the body. Let us conditionally divide them into 2 groups: device characteristics and improper operation.

Characteristics of a lighting device that are harmful to the body:

• Spectral characteristics of the light source;
• radiation in the infrared spectrum;
• pulsations of light flux.

The second group is harm to health not from the light source itself, but from its improper use. Let's look at each lighting factor that affects your health and determine whether LED light is harmful to your eyes.

What are the differences between light sources?

Sunlight should be taken as the standard, since it contains the most complete spectrum of light radiation. Of all the artificial lighting devices, the incandescent light bulb is the closest to the sun. Compare the spectral characteristics of different sources.

The graphs show different spectra of lighting fixtures. Incandescent light has a smooth spectrum, increasing towards the red region. The spectrum of fluorescent light sources is quite ragged, plus a low color rendering index (about 70).

Working in rooms with such lighting causes increased fatigue and headaches, as well as distorted color perception.

The spectrum of LED lamps is more complete and even. It has increased intensity in the wavelength region of 450 nm, for cold glow, and in the region of 600 nm, for “warm” lamps, respectively. LED sources provide normal color rendering with a CRI index of more than 80. LED lamps have extremely low UV intensity.

If you compare the spectrum of diode and popular fluorescent lamps, it becomes clear why the latter are used less and less. The spectrum of CFLs is completely far from the standard, and their color rendering index leaves much to be desired.

Based on this, we can conclude that, based on the characteristics of the spectrum, LED lamps are harmless to health.

Why do the lamps flicker?

The next factor that affects well-being is the pulsation coefficient of the light flux. To understand what it is and what it depends on, you need to consider the shape of the voltage in the electrical network.

The quality of light and its pulsation depend on the power source from which they operate. Light sources that operate on constant voltage, such as 12-volt LED lamps, do not flicker. Let's look at flickering and the harm of LED lamps to the eyes, the causes of their occurrence and ways to eliminate them.

From the outlet we receive alternating voltage with an effective value of 220V and 310V amplitude, which you can see in the top graph (a).

Since LEDs are powered by direct current, not alternating current, it needs to be rectified. The body of the LED lamp contains an electronic circuit with a single- or full-wave rectifier, after which the voltage becomes unipolar. It is constant in sign, but not in magnitude, i.e. pulsating from 0 to 310 volts, graph in the middle (b).

Such lamps pulsate at a frequency of 100 hertz or 100 times per second, in time with the voltage ripples. The harm to the eyes of LED lamps depends on their quality, more on this later.

Do the LEDs pulsate?

LED lamps use drivers with current stabilization (expensive), or anti-aliasing filters (cheap). The voltage becomes constant and stabilized if capacitive filters are used.

If the manufacturer has not saved on the driver, the current value becomes stable. This is the best option for both ripple reduction and LED lifespan.

The photo below shows what the pulsations look like from the camera's perspective. You may not notice the pulsation, since the organs of vision strive to adapt the picture for perception. The brain absorbs these pulsations perfectly, which causes fatigue and other side effects.

The effect of LED lamps on human vision can be negative if they produce a pulsating light flux. Sanitary standards limit the depth of pulsations for office premises to 20%, and for places where work is carried out causing eye strain to 15%.

Lamps with large pulsations should not be installed at home; they are only suitable for lighting the corridor, pantry, entrances and utility rooms. Any room where you do not do any visual work and do not stay for a long time.

The harm from low-price LED lamps is caused primarily by pulsations. Don’t skimp on lighting; an LED with a normal driver costs only 50-100 rubles more than the cheapest Chinese analogues.

Other light sources and their pulsations

Incandescent lamps do not flicker because they operate on alternating current and the filament does not have time to cool down when the voltage crosses the zero mark. Fluorescent tubular lamps flicker if connected using the old “throttle” circuit. You can distinguish it by the characteristic throttle hum during operation. The photo below shows the pulsations of a raster lamp as seen by the phone camera.

More modern CFLs and LLs do not hum or flicker only because their circuit uses a high-frequency switching power supply. Such a power source is called an electronic ballast (electronic ballast or device) .

Harm from the infrared spectrum

To determine whether LED lamps are harmful to vision, consider the third factor of harm - infrared radiation. It is worth noting that:

• Firstly, the harmfulness of the IR spectrum is doubtful and does not have a solid argument;
• secondly, in the spectrum of LEDs, infrared radiation is either absent or extremely small. You can verify this in the graphs given at the beginning of the article.

Are halogen lamps harmful to health? In light sources rich in the infrared spectrum (halogens), responsible manufacturers (Philips, Osram, etc.) use IR filters, so their harm to health is minimized.

Blue spectrum harm

It has been scientifically proven that radiation in the blue spectrum reduces the production of the sleep hormone melatonin and damages the retina, causing irreversible changes in it.

In addition to a drop in melatonin levels, blue light radiation causes a number of side effects: fatigue, increased eyestrain, eye disease. This color is perceived as brighter, which is often used in marketing to attract our attention. Most indicators on speakers, TVs, monitors, and other equipment are blue.

More details about this and how safe LED lamps are for the eyes are written in the community.

White LEDs are blue LEDs coated with a special phosphor that converts the radiation to white.

Blue color is the most negative factor in the influence of LED lamps on vision. Take a look at the graphs, namely the emission spectrum of the LEDs presented above. Even a warm-light LED lamp has a brightness peak in the blue spectrum, while a cold lamp has a very high brightness peak.

The practical side of the problem

So the harm of LED lamps to humans is not a myth? Not certainly in that way. The fact is that the studies were carried out under conditions where the samples under study were illuminated with powerful blue LEDs and their entire spectrum was in the “harmful” range.

Although there is a share of blue light in cold LEDs, it is no less in sunlight.

Modern people of any age spend a lot of time in front of computer screens, smartphones and tablets. Continuous focusing at a distance of 0.3-1 meter from the screen causes incomparably greater damage to vision.

The harmfulness of the blue spectrum of LED lamps, compared to the harm from device screens, is insignificant. LED is ideal for illuminating a room, office or other premises with a stream of bright light with low energy consumption.

If you are worried, various types of lenses and glasses for computer work have been developed to reduce the harm of blue radiation. Their filters reflect light in the blue range and make colors warmer.

Need to remember: It is not LEDs that are harmful to human health, but the incorrect mode of working with gadgets and poor lighting.

LEDs - benefit or harm?

You can understand whether LED lamps are harmful or not by organizing proper lighting in accordance with GOST on lighting. It regulates the amount of light to carry out work of varying precision and size of parts that you operate with during work.

LED light sources allow you to achieve the desired brightness in the workplace, with minimal electricity bills. You will preserve your vision, it will be easier for you to work when the room is light and you don’t need to look at small details in dim light. In this case, the harmfulness of LED lamps to the eyes is minimal.

The high energy consumption of old incandescent lamps is unprofitable both on a national scale (high load on power lines) and on an individual scale (high consumption and high price of electricity).

Today, the debate about whether LED lamps are harmful to vision remains open and a definite answer cannot be given. They have filled the lighting market relatively recently, less than 10 years ago, and many are skeptical about them.

The impact of LED lamps on human health will be zero if the daily routine, sleep and work are followed correctly. If a person is subject to stress, excessive loads and does not take the quality of sleep seriously, no light source will preserve his health.

svetodiodinfo.ru

Determining the sufficiency of light

If you decide to install lamps for plants, then you need to do it as correctly as possible. To do this, you need to decide which plants lack the ray, and which will be superfluous. If you are designing lighting in a greenhouse, then you need to provide zones with different spectrums. Next you need to determine the number of LEDs themselves. Professionals do this with a special device - a lux meter. You can also make the calculation yourself. But you will have to dig a little and design the desired model.

If the project is being done for a greenhouse, there is one universal rule for all types of light sources. When the height of the suspension increases, the illumination decreases.

LEDs

The spectrum of color radiation is of great importance. The optimal solution would be red and blue LEDs for plants in a two to one ratio. How many watts the device will have doesn't really matter.

But more often they use one-watt ones. If you need to install diodes yourself, it is better to purchase ready-made tapes. You can secure them with glue, buttons or screws. It all depends on the holes provided. There are a lot of manufacturers of such products; it is better to choose a well-known, rather than a faceless seller who cannot give a guarantee for his product.

Light wavelength

The spectrum of natural sunlight contains both blue and red colors. They allow plants to develop mass, grow and bear fruit. When irradiated only with a blue spectrum with a wavelength of 450 nm, the representative of the flora will be stunted. Such a plant cannot boast of a large green mass. It will also bear fruit poorly. When absorbing the red range with a wavelength of 620 nm, it will develop roots, bloom well and bear fruit.

Pros of LEDs

When a plant is illuminated with LED lamps, it goes all the way: from sprout to fruit. At the same time, during this time, only flowering will occur when the luminescent device is operating. LEDs for plants do not heat up, so there is no need to frequently ventilate the room. In addition, there is no possibility of thermal overheating of flora representatives.

Such lamps are irreplaceable for growing seedlings. The directionality of the radiation spectrum helps the shoots to grow stronger in a short time. Low energy consumption is also a plus. LEDs are second only to sodium lamps. But they are ten times more economical than incandescent lamps. LEDs for plants last up to 10 years. The warranty period is from 3 to 5 years. Having installed such lamps, you will not have to worry about replacing them for a long time. Such lamps do not contain harmful substances. Despite this, their use in greenhouses is very preferable. The market today presents a large number of different designs of such lamps: they can be hung, mounted on a wall or ceiling.

Minuses

To increase the radiation intensity, LEDs are assembled into a large structure. This is a disadvantage only for small rooms. In large greenhouses this is not significant. The disadvantage can be considered the high cost compared to analogues - fluorescent lamps. The difference can reach eightfold. But diodes will pay for themselves after several years of service. They can significantly save energy. A decrease in glow is observed after the warranty period expires. With a large greenhouse area, more lighting points are needed compared to other types of lamps.

Radiator for lamp

It is necessary that heat is removed from the device. This would be better done by a radiator made of aluminum profile or steel sheet. The use of a U-shaped finished profile will require less labor. Calculating the radiator area is easy. It must be at least 20 cm 2 per 1 Watt. After all the materials have been selected, you can assemble everything into one chain. It is better to alternate LEDs for plant growth by color. This will ensure uniform lighting.

PhytoLED

The latest development, such as phyto-LED, can replace conventional analogues that glow in only one color. The new device combines the necessary spectrum of LEDs for plants in one chip. It is needed for all stages of growth. The simplest phytolamp usually consists of a block with LEDs and a fan. The latter, in turn, can be adjusted in height.

Fluorescent lamps

Fluorescent lamps have long remained at the peak of popularity in household gardens and vegetable gardens. But such lamps for plants do not fit the color spectrum. They are increasingly being replaced by phyto-LED or special-purpose fluorescent lamps.

Sodium

A light as strong in saturation as that of a sodium apparatus is not suitable for placement in an apartment. Its use is advisable in large greenhouses, gardens and greenhouses where plants are illuminated. The disadvantage of such lamps is their low performance. They convert two-thirds of the energy into heat and only a small part is used for light radiation. In addition, the red spectrum of such a lamp is more intense than the blue one.

We make the device ourselves

The easiest way to make a lamp for plants is to use a strip with LEDs on it. We need it in the red and blue spectra. They will connect to the power supply. The latter can be purchased in the same place as tapes - at a hardware store. You also need a fastening - a panel the size of the lighting area.

Manufacturing should begin by cleaning the panel. Next, you can glue the diode tape. To do this, remove the protective film and stick the sticky side to the panel. If you have to cut the tape, then its pieces can be joined using a soldering iron.

LEDs for plants do not require additional ventilation. But if the room itself is poorly ventilated, then it is advisable to install the tape on a metal profile (for example, made of aluminum). Lighting modes for flowers in a room can be as follows:

• for those growing far from the window, in a shaded place, 1000-3000 lux will be enough;
• for plants that need diffused light, the value will be up to 4000 lux;
• representatives of the flora that need direct lighting - up to 6000 lux;
• for tropical and those that bear fruit - up to 12,000 lux.

If you want to see indoor plants in a healthy and beautiful form, you must carefully satisfy their need for lighting. So, we have found out the advantages and disadvantages of LED lamps for plants, as well as the spectrum of their rays.

The emission spectrum of an LED is determined by the bandgap of the semiconductor material used, the type of dopant, the doping level, and the radiative recombination mechanism. As mentioned above, the main materials for the manufacture of efficient LEDs are binary semiconductor compounds A III B V and their solid solutions. In Fig. Figure 4.4 shows the emission spectra at room temperature of some typical commercially produced LEDs in relative units.

LEDs based on gallium arsenide are the most efficient GaAs with band gap ∆ E= 1.45 eV. Consequently, the maximum of the spectral characteristics of the radiation itself GaAs observed at wavelength λ max=1.24/1.4 = 0.9 µm, which corresponds to the infrared region. When doping GaAs various impurities (tellurium, selenium, lithium, etc.) having different depths in the band gap, LEDs can emit in the range λ max= 0.9…0.96 µm. LEDs on GaAs have the highest quantum efficiency ( η external=10...30% depending on the design). It is important that the emission spectrum GaAs-LEDs correspond very well to the photosensitivity spectrum of the most common Si-photodiodes.

LEDs for longer wavelengths are manufactured based on direct-gap solid solutions Ga X 1p 1's As And Ga X 1p 1's As 1st R at . For them, quasi-interband radiative recombination is predominant.

It is important that the maximum emission spectrum of such LEDs is determined by the composition of the solid solution. Changing X And at, it is possible to produce an LED for a given region of the spectrum, for example, coinciding with the minimum of losses in an optical fiber or with the maximum of the absorption spectrum of any substance whose concentration is to be controlled. LEDs for the spectrum region λ >5 microns can be made on the basis of lead chalcogenides: Rb X SP 1- x Those and mercury: Cd X Hg 1- x Those.

Gallium phosphide ( GaP) has a band gap ∆ E = 2.25 eV, which determines the wavelength of the radiation λ max=0.56 µm. This corresponds to the green color of the glow. When doped with impurities ( N, O 2 , Zn) such LEDs can emit red, yellow, green light. Thus, GaP LEDs are designed to operate in the visible part of the spectrum. For GaP - η external = 7…0,7 %.

Light-emitting diodes for the short-wave region of the visible spectrum, operating in the blue, indigo and violet ranges, can be created on the basis of gallium nitride GaN and heterojunctions using solid solutions Ga X In 1- x N And Ga 1- x Al x N. LED based GaN give off radiation λ max=0.44 µm, but with very low efficiency η external 0,5 %.

Silicon carbide is used for the same purpose. SiC. Although diodes based SiC have small η external 0.01%, but have high time and temperature stability. Based on them, standard radiation sources are created.

Fig.4.4. Emission spectra of LEDs.

For emitting diodes of both infrared and visible radiation, ternary compounds made on the basis of a gallium-aluminum-arsenic solid solution are widely used GaAlAs. Solid solutions based on gallium-arsenic-phosphorus are also used GaAsP and indium gallium phosphorus I nGaP. According to the general indicator ( R izl, performance) GaAlAs most fully satisfies the requirements of optoelectronics. In this material, some of the atoms Ga in crystal GaAs replaced by atoms Al. As the fraction of substituted atoms increases, the band gap varies from ∆ E=1.45 eV ( GaAs) before ∆ E=2.16 eV (pure AlAs). Thus, such LEDs can emit at a wavelength  max=0.6...0.9 µm, i.e. generate radiation in both the visible and infrared regions of the spectrum. The external quantum yield for this material is η external =1,2…12 %.

Brightness LED illumination or radiation power depends almost linearly on the current through the diode over a wide range of current changes. The exception is red GaP- LEDs, in which brightness saturates as the current increases. With a constant current through the LED, its brightness decreases with increasing temperature. For the Reds GaP- for LEDs, an increase in temperature compared to room temperature by 20 o C reduces their brightness by about 10%, and for green ones - by 6%. As temperatures rise, the lifespan of LEDs decreases. The lifespan of an LED also decreases as its current increases.

White LED

Powerful white LED

There are two types of white LEDs:

• Multi-chip LEDs, more often three-component (RGB LEDs), containing three semiconductor emitters of red, green and blue light, combined in one housing.
• Phosphor LEDs, created on the basis of an ultraviolet or blue LED, containing a layer of a special phosphor that, as a result of photoluminescence, converts part of the LED radiation into light in a relatively wide spectral band with a maximum in the yellow region (the most common design). The emission of the LED and phosphor, when mixed, produce white light of various shades.

History of invention

The first red semiconductor emitters for industrial use were obtained by N. Holonyak in 1962. In the early 70s, yellow and green LEDs appeared. The light output of early low-efficiency devices reached the single lumen level by 1990. In 1993, Suji Nakamura, an engineer at Nichia (Japan), created the first high-brightness blue LED. Almost immediately, LED RGB devices appeared, since blue, red and green colors made it possible to obtain any color, including white. White phosphor LEDs first appeared in 1996. Subsequently, the technology developed rapidly and by 2005, the luminous output of LEDs reached 100 lm/W or more. LEDs appeared with different shades of glow, the quality of light made it possible to compete with incandescent lamps and with already traditional fluorescent lamps. The use of LED lighting devices in everyday life, in indoor and outdoor lighting, has begun.

RGB LEDs

White light can be created by mixing different colored LEDs. The most common trichromatic design is made from red (R), green (G) and blue (B) sources, although bichromatic, tetrachromatic and more multi-chromatic variants are found. A multicolor LED, unlike other RGB semiconductor emitters (luminaires, lamps, clusters), has one complete housing, most often similar to a single-color LED. The LED chips are located next to each other and share a common lens and reflector. Since semiconductor chips have a finite size and their own radiation patterns, such LEDs most often have uneven angular color characteristics. In addition, to obtain the correct color ratio, it is often not enough to set the design current, since the light output of each chip is unknown in advance and is subject to changes during operation. To set the desired shades, RGB lamps are sometimes equipped with special control devices.

The spectrum of an RGB LED is determined by the spectrum of its constituent semiconductor emitters and has a pronounced line shape. This spectrum is very different from the spectrum of the sun, therefore the color rendering index of the RGB LED is low. RGB LEDs make it possible to easily and widely control the color of the glow by changing the current of each LED included in the triad, adjusting the color tone of the white light they emit directly during operation - up to obtaining individual independent colors.

Multicolor LEDs have a dependence of light output and color on temperature due to the different characteristics of the emitting chips that make up the device, which results in a slight change in the color of the glow during operation. The service life of a multicolor LED is determined by the durability of the semiconductor chips, depends on the design and most often exceeds the service life of phosphor LEDs.

Multicolor LEDs are used primarily for decorative and architectural lighting, in electronic signage and video screens.

Phosphor LEDs

Spectrum of one of the phosphor LED options

Combining a blue (more often) or ultraviolet (less often) semiconductor emitter and a phosphor converter allows you to produce an inexpensive light source with good characteristics. The most common design of such an LED contains a blue gallium nitride semiconductor chip modified with indium (InGaN) and a phosphor with maximum re-emission in the yellow region - yttrium-aluminum garnet doped with trivalent cerium (YAG). Part of the power of the initial radiation of the chip leaves the LED body, dissipating in the phosphor layer, the other part is absorbed by the phosphor and re-emitted in the region of lower energy values. The re-emission spectrum covers a wide region from red to green, but the resulting spectrum of such an LED has a pronounced dip in the green-blue-green region.

Depending on the composition of the phosphor, LEDs are produced with different color temperatures (“warm” and “cold”). By combining different types of phosphors, a significant increase in the color rendering index (CRI or R a) is achieved, which suggests the possibility of using LED lighting in conditions critical to the quality of color rendering.

One way to increase the brightness of phosphor LEDs while maintaining or even reducing their cost is to increase the current through the semiconductor chip without increasing its size - increasing the current density. This method is associated with a simultaneous increase in requirements for the quality of the chip itself and the quality of the heat sink. As the current density increases, the electric fields in the bulk of the active region reduce the light output. When the limiting currents are reached, since areas of the LED chip with different impurity concentrations and different band gaps conduct current differently, local overheating of the chip areas occurs, which affects the light output and the durability of the LED as a whole. In order to increase the output power while maintaining the quality of spectral characteristics and thermal conditions, LEDs are produced containing clusters of LED chips in one housing.

One of the most discussed topics in the field of polychrome LED technology is its reliability and durability. Unlike many other light sources, an LED changes its light output (efficiency), radiation pattern, and color tint over time, but rarely fails completely. Therefore, to estimate the useful life, for example for lighting, a level of reduction in luminous efficiency of up to 70% of the original value (L70) is taken. That is, an LED whose brightness decreases by 30% during operation is considered to be out of order. For LEDs used in decorative lighting, a brightness reduction level of 50% (L50) is used as an assessment of the lifespan.

The service life of a phosphor LED depends on many parameters. In addition to the manufacturing quality of the LED assembly itself (the method of attaching the chip to the crystal holder, the method of attaching the current-carrying conductors, the quality and protective properties of the sealing materials), the lifetime mainly depends on the characteristics of the emitting chip itself and on changes in the properties of the phosphor over the course of operation (degradation). Moreover, as numerous studies show, the main factor influencing the service life of an LED is temperature.

Effect of temperature on LED service life

During operation, a semiconductor chip emits part of the electrical energy in the form of radiation and part in the form of heat. Moreover, depending on the efficiency of such conversion, the amount of heat is about half for the most efficient emitters or more. The semiconductor material itself has low thermal conductivity; in addition, the materials and design of the housing have a certain non-ideal thermal conductivity, which leads to the heating of the chip to high temperatures (for a semiconductor structure). Modern LEDs operate at chip temperatures in the region of 70-80 degrees. And a further increase in this temperature when using gallium nitride is unacceptable. High temperature leads to an increase in the number of defects in the active layer, leads to increased diffusion, and a change in the optical properties of the substrate. All this leads to an increase in the percentage of non-radiative recombination and absorption of photons by the chip material. An increase in power and durability is achieved by improving both the semiconductor structure itself (reducing local overheating), and by developing the design of the LED assembly, and improving the quality of cooling of the active area of ​​the chip. Research is also being conducted with other semiconductor materials or substrates.

The phosphor is also susceptible to high temperatures. With prolonged exposure to temperature, re-emitting centers are inhibited and the conversion coefficient, as well as the spectral characteristics of the phosphor, deteriorate. In early and some modern polychrome LED designs, the phosphor is applied directly to the semiconductor material and the thermal effect is maximized. In addition to measures to reduce the temperature of the emitting chip, manufacturers use various methods to reduce the influence of chip temperature on the phosphor. Isolated phosphor technologies and LED lamp designs, in which the phosphor is physically separated from the emitter, can increase the service life of the light source.

The LED housing, made of optically transparent silicone plastic or epoxy resin, is subject to aging under the influence of temperature and begins to dim and yellow over time, absorbing part of the energy emitted by the LED. Reflective surfaces also deteriorate when heated - they interact with other elements of the body and are susceptible to corrosion. All these factors together lead to the fact that the brightness and quality of the emitted light gradually decreases. However, this process can be successfully slowed down by ensuring efficient heat removal.

Phosphor LED design

Diagram of one of the white LED designs. MPCB ​​is a high thermal conductivity printed circuit board.

A modern phosphor LED is a complex device that combines many original and unique technical solutions. The LED has several main elements, each of which performs an important, often more than one function:

All LED design elements experience thermal stress and must be selected taking into account the degree of their thermal expansion. And an important condition for a good design is manufacturability and low cost of assembling an LED device and installing it in a lamp.

Brightness and quality of light

The most important parameter is not even the brightness of the LED, but its luminous efficiency, that is, the light output from each Watt of electrical energy consumed by the LED. The luminous efficiency of modern LEDs reaches 150-170 lm/W. The theoretical limit of the technology is estimated at 260-300 lm/W. When assessing, it is necessary to take into account that the efficiency of a lamp based on LEDs is significantly lower due to the efficiency of the power source, the optical properties of the diffuser, reflector and other design elements. In addition, manufacturers often indicate the initial efficiency of the emitter at normal temperature. While the temperature of the chip during operation is much higher. This leads to the fact that the actual efficiency of the emitter is 5 - 7% lower, and that of the lamp is often twice as low.

The second equally important parameter is the quality of the light produced by the LED. There are three parameters to assess the quality of color rendering:

Phosphor LED based on an ultraviolet emitter

In addition to the already widespread combination of a blue LED and YAG, a design based on an ultraviolet LED is also being developed. A semiconductor material capable of emitting in the near ultraviolet region is coated with several layers of a phosphor based on europium and zinc sulfide activated by copper and aluminum. This mixture of phosphors gives re-emission maxima in the green, blue and red regions of the spectrum. The resulting white light has very good quality characteristics, but the efficiency of such conversion is still low.

Advantages and disadvantages of phosphor LEDs

Considering the high cost of LED lighting sources compared to traditional lamps, there are compelling reasons to use such devices:

• The main advantage of white LEDs is their high efficiency. Low specific energy consumption allows them to be used in long-running sources of autonomous and emergency lighting.
• High reliability and long service life suggest possible savings on lamp replacement. In addition, the use of LED light sources in hard-to-reach areas and outdoor conditions reduces maintenance costs. Combined with high efficiency, there are significant cost savings when using LED lighting in some applications.
• Light weight and size of devices. LEDs are small in size and suitable for use in hard-to-reach places and small portable devices.
• The absence of ultraviolet and infrared radiation in the spectrum allows the use of LED lighting without harm to humans and for special purposes (for example, for illuminating rare books or other objects exposed to light).
• Excellent performance at sub-zero temperatures without reducing, and often even improving, parameters. Most types of LEDs exhibit greater efficiency and longer life as temperatures drop, but power, control, and design components may have the opposite effect.
• LEDs are inertia-free light sources; they do not require time to warm up or turn off, such as fluorescent lamps, and the number of on and off cycles does not negatively affect their reliability.
• Good mechanical strength allows LEDs to be used in harsh operating conditions.
• Ease of power regulation by both duty cycle and supply current regulation without compromising efficiency and reliability parameters.
• Safe to use, no risk of electric shock due to low supply voltage.
• Low fire hazard, possibility of use in conditions of explosion and fire hazard due to the absence of incandescent elements.
• Moisture resistance, resistance to aggressive environments.
• Chemical neutrality, no harmful emissions and no special requirements for disposal procedures.

But there are also disadvantages:

Lighting LEDs also have features inherent in all semiconductor emitters, taking into account which the most successful application can be found, for example, the direction of radiation. The LED shines only in one direction without the use of additional reflectors and diffusers. LED luminaires are best suited for local and directional lighting.

Prospects for the development of white LED technology

Technologies for manufacturing white LEDs suitable for lighting purposes are under active development. Research in this area is stimulated by increased public interest. The prospect of significant energy savings is attracting investment in process research, technology development and the search for new materials. Judging by the publications of manufacturers of LEDs and related materials, specialists in the field of semiconductors and lighting engineering, it is possible to outline development paths in this area:

see also

Notes

1. , p. 19-20
2. Cree MC-E LEDs containing red, green, blue and white emitters. LED Professional. Archived
3. Vishay VLMx51 LEDs containing red, orange, yellow and white emitters. LED Professional. Archived from the original on November 23, 2012. Retrieved November 10, 2012.
4. Cree XB-D and XM-L Multicolor LEDs. LED Professional. Archived from the original on November 23, 2012. Retrieved November 10, 2012.
5. Cree XP-C LEDs containing six monochromatic emitters. LED Professional. Archived from the original on November 23, 2012. Retrieved November 10, 2012.
6. Nikiforov S.“S-class” of semiconductor lighting technology // Components and technologies: magazine. - 2009. - No. 6. - P. 88-91.
7. Truson P. Halvardson E. Advantages of RGB LEDs for lighting devices // Components and technologies: magazine. - 2007. - No. 2.
8. , p. 404
9. Nikiforov S. Temperature in the life and operation of LEDs // Components and technologies: magazine. - 2005. - No. 9.
10. LEDs for interior and architectural lighting (English). LED Professional. Archived from the original on November 23, 2012. Retrieved November 10, 2012.
11. Siang Ling Oon LED solutions for architectural lighting systems // : magazine. - 2010. - No. 5. - P. 18-20.
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13. Turkin A. Gallium nitride as one of the promising materials in modern optoelectronics // Components and technologies: magazine. - 2011. - No. 5.
14. LEDs with high CRI values. LED Professional. Archived from the original on November 23, 2012. Retrieved November 10, 2012.
15. Cree's EasyWhite technology. LEDs Magazine. Archived from the original on November 23, 2012. Retrieved November 10, 2012.
16. Nikiforov S., Arkhipov A. Features of determining the quantum yield of LEDs based on AlGaInN and AlGaInP at different current densities through the emitting crystal // Components and technologies: magazine. - 2008. - No. 1.
17. Nikiforov S. Now electrons can be seen: LEDs make electric current very visible // Components and technologies: magazine. - 2006. - No. 3.
18. LEDs with a matrix arrangement of a large number of semiconductor chips (English). LED Professional. Archived from the original on November 23, 2012. Retrieved November 10, 2012.
19. White LED Lifetime Archived from the original on November 23, 2012. Retrieved November 10, 2012.
20. Types of LED defects and methods of analysis (English). LED Professional. Archived from the original on November 23, 2012. Retrieved November 10, 2012.
21. , p. 61, 77-79
22. LEDs from SemiLEDs (English). LED Professional. Archived from the original on November 23, 2012. Retrieved November 10, 2012.
23. GaN-on-Si Silicon LED Research Program. LED Professional. Retrieved November 10, 2012.
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Literature

• Schubert F.E. LEDs. - M.: Fizmatlit, 2008. - 496 p. - ISBN 978-5-9221-0851-5
• Weinert D. LED Lighting: A Handbook. - Philips, 2010. - 156 p. - ISBN 978-0-615-36061-4

Links

• US Department of Energy website about LED lighting
• Led Professional. Scientific and technical journal about LEDs and LED lighting, Austria
• LEDs Magazine. Scientific and technical magazine about LEDs and LED lighting. USA
• Semiconductor lighting technology. Russian magazine about LEDs and LED lighting

White LED

Unlike traditional incandescent and fluorescent lamps, which produce white light, LEDs generate light in a very narrow range of the spectrum, i.e. give an almost monochrome glow. That is why LEDs have long been used in control panels and garlands, and today they are especially effectively used in lighting installations that emit a specific primary color, for example, in traffic lights, signs, and signal lights.

Principle of a white LED

The design principle of a white LED is not very complicated; the implementation technology is complex. In order for an LED to emit white light, it is necessary to resort to additional technical elements and technical solutions. The main methods for obtaining white light in LEDs are:

applying a layer of phosphor to blue crystals;

applying several layers of phosphor to crystals that emit light close in color to ultraviolet;

RGB systems, in which a white glow is achieved by mixing the light of many monochrome red, green and blue diodes.

In the first case, most often, blue LED crystals are used, which are coated with a phosphor, yellow phosphorus. Phosphorus absorbs some blue light and emits yellow light. When the remaining unabsorbed blue light is mixed with yellow, the resulting light is close to white.

The second method is a recently developed technology for producing solid-state white light sources based on a combination of a diode emitting a glow similar in color to ultraviolet and several layers of phosphor made of phosphorus of various compositions.

In the latter case, white light is produced in the classical way by mixing three basic colors (red, green and blue). The quality of white light is improved by complementing the RGB configuration with yellow LEDs to cover the yellow part of the spectrum.

Advantages and disadvantages of old LEDs

Each of these methods has its positive and negative sides. Thus, white phosphor LEDs, manufactured on the principle of combining blue crystals with a phosphor phosphor, are characterized by a fairly low color rendering index, a tendency to generate white light in cold tones, heterogeneity in the hue of the glow with a fairly high luminous flux and a relatively low cost.

White phosphor LEDs, obtained on the basis of a combination of diodes with a glow close to ultraviolet color and multi-colored phosphors, have an excellent color rendering index, can generate white light of warmer shades and are characterized by greater uniformity of glow shades from diode to diode. However, they consume more electricity and are not as bright as the first ones.

In turn, RGB LEDs make it possible to create dynamic lighting effects in lighting installations with a change in the color of the glow and different tones of white light and can potentially provide a very high color rendering index. At the same time, LEDs of individual colors react differently to the operating current, ambient temperature and brightness control, and therefore RGB LEDs require rather complex and expensive control systems to achieve stable operation.

So that lamps based on white LEDs provide better quality light, i.e. a more complete spectrum is used in the design of lamps