About the efficiency of lamps, including LEDs. Efficiency of LED lamps

The traditional approach to LED lamps often leads to a misunderstanding of fundamental circumstances. It's about about the efficiency of lamps and the influence of the design of LED and conventional lamps on the efficiency.

The efficiency of a luminaire is the ratio of the output from the luminaire luminous flux to the entire luminous flux created by a light source. For example, a lamp in the form of a light bulb without lighting fixtures, primarily without a reflector, has an efficiency of 100%. This does not mean at all that this is an ideal to which we must strive; for lamps - less efficiency, this does not mean worse. Any attempts to concentrate (direct) light leads to a decrease in efficiency. But the method of concentration and the quality of the reflector may be different, and the lamps will have different efficiency. You can compare luminaires by efficiency only those that have a similar light distribution(KSS), in this case the efficiency will be determined by the quality of the optical system of the lamp (reflector, glass). It makes no sense to compare luminaires with different KSS in terms of efficiency!

The fundamental difference between LEDs and lamps is that they shine only in one half-plane. That is, an LED lamp without lighting fixtures (100% efficiency) will be directed! The emission angle of LEDs without secondary optics is 90-120 degrees. For example, if we compare two “lamps” in the form of a light bulb and an LED (100% efficiency) with the same luminous flux, then on the axis of the lamp at the same distance the illumination will be approximately 2 times less than on the axis of the LED. If you try to collect the luminous flux of the lamp using a reflector (to achieve the same angle of radiation), then in any case you will not be able to obtain the same illumination that the LED provides due to reflection losses. In this regard, replacing a light bulb light source with an LED source in directional luminaires will make sense, even if these sources have the same luminous efficiency (lm/W).

If a luminaire with a lamp has flat glass, that is, the entire light source is “immersed” inside the lamp, The efficiency of the lamp will decrease significantly due to the fact that the main part of the light coming out of the lamp will be reflected, that is, with reflection losses. For an LED lamp of this design, there is practically no decrease in efficiency(only losses in glass are about 5%), although intuitively it seems that, by analogy with lamp lamps, the efficiency should decrease.

A tube luminaire with flat glass will have an efficiency of about 50-60%.

An LED lamp with flat glass will have an efficiency of about 95%.

This is the main fundamental difference LED lamps from lamp ones. Directional LED lights are much more efficient than directional tube lights. This is due largely to the design features of LEDs, and not just to their high luminous efficiency.

Understanding this circumstance should lead to a revision of approaches to the calculation of lighting installations using LED lamps.

How efficient are LEDs really and how can you extend their lifespan?

How to measure their efficiency at home and increase the efficiency, as well as increase the durability of LED lamps?

To answer all these questions, it is enough to conduct several visual experiments, without using any complex laboratory instruments.
LED is one of the most efficient and easiest to use light sources. However, at the same time, it still wastes most of the energy consumed, converting it not into light, but into heat.

Of course, there is no need to compare LEDs with a regular light bulb; here they have run far ahead. But how high do you think their real efficiency is?

How to measure LED efficiency

Let's check this live, not by the labels on the packages and data from tables on the Internet, but by the colorimetric method at home.

If you lower an LED into water and measure the temperature difference before it turns on and some time after, you can find out how much energy from it will turn into heat.

Knowing the total amount of energy expended and energy lost into heat, you can really find out how much benefit there is from this source light turned into light.

The container in which measurements will be made must be insulated from temperature fluctuations outside and inside. A regular thermos flask is suitable for this.

With some modification, you will have a completely usable homemade colorimeter.

To isolate and prevent current leakage, all wires and terminals on the LED should be coated with a thick layer of electrical insulating varnish.

Before the experiment, pour 250 ml of distilled water into the flask.

Place the LED in water until it completely covers it. In this case, the light should come out freely.

Turn on the power and start counting down the time.

After 10 minutes, turn off the voltage and measure the water temperature again.

At the same time, do not forget to mix it well.

Now you need to repeat the experiment, but this time, tightly seal the matrix with some opaque material. This is necessary so that energy cannot leave the system in the form of light.

The experiment with the sealed specimen is repeated again in the same sequence:

• 250ml distilled water

• initial temperature measurement

• 10 minutes of “glow”

• final temperature measurement

1 of 4

After all measurements and experiments, you can proceed to calculations.

Efficiency calculation

Let's say for this model the average consumption of the light source is 47.8 W. Operating time – 10 minutes.

If we substitute these data into the formula, we get that over a period of 600 seconds, 28,320 J were spent on lighting the LED.

In the case of the sealed model, the water heated from 27 to 50 degrees. The heat capacity of water is 4200 J, and the mass is 0.25 kg.

Another 130 J per degree was spent heating the bulb, plus you need to add energy to heat the LED itself. It weighs 27 grams and is mainly composed of copper. The result is a figure of 27377 J.

The ratio of energy released and energy expended will be 96.7%. That is, more than 3% is missing. This is precisely heat loss.

In the case of an open LED, the water heated from 28 to 45 degrees. All other variables remained the same. The calculation here would look like this:

What conclusion can be drawn from all these experiments and calculations?

As can be seen from this small experiment, about 28% of the energy left the system directly in the form of light. And if we take into account 3% of heat losses, then only 25% remains.

As you can see, LEDs are still very far from being ideal light sources, as many sellers present them.

Even worse, there are often models on the market that are extremely Low quality with even lower efficiency.

Brightness and power

Let's now compare the brightness different models and let's see what it depends on and whether we can somehow influence it. To make a reliable comparison, use a regular piece of pipe and a lux meter.

Let’s say a previously tested high-quality sample provides illumination of 1100 lux. And this is with a power consumption of 50 W.

And if you take more cheap model? The data may turn out to be two times lower - less than 5500 Lux.

And this is with the same power! It turns out that you will pay the same amount for light as in the first case, but you will receive it 50% less.

Is it possible to get 3 times more light, using as little energy as possible?

It is possible, but for this you will need an LED operating in a slightly different mode. To understand how to do this, you need to take some more measurements.

First of all, you should be interested in the dependence of brightness on power consumption. Gradually increase the power and monitor the lux meter readings.

As a result, you will reach such a nonlinear relationship.

If it were linear, you'd get something like this.

It will turn out even more interesting if you calculate the relative efficiency of the LED, taking the power value of 50W as 100%.

You can see how its effectiveness is deteriorating. This deterioration with increasing power is inherent in all LEDs. And there are several reasons for this.

Why LED Efficiency Deteriorates

One of them is, of course, heating. With increasing temperature, the probability of photon formation in the p-n junction decreases.

In addition, the energy of these photons decreases. Even with good cooling housing, temperature p-n junction may be tens of degrees higher, since it is separated from the metal by a sapphire substrate.

And it doesn't conduct heat very well. The temperature difference can be calculated by knowing the dimensions of the crystal and the heat generated on it.

With a heat release of 1 W, taking into account the thickness and area of ​​the substrate, the junction temperature will be 11.5 degrees higher.

In the case of a cheap LED, everything is much worse. Here the result is more than 25 degrees.

High junction temperatures lead to rapid degradation of the crystal, shortening its service life. This is where blinking, flickering, etc. occurs.

I wonder if manufacturers are unaware of this difference in temperature or are they deliberately creating doomed devices?

Often, components that seem to be in normal, expensive lamps operate in extreme conditions, at maximum temperatures, without any safety margin.

As long as the current is small, it is not noticeable. But due to the quadratic relationship, as the current increases, more and more of the energy turns into useless heat.

How to increase efficiency

That is, connect another LED in parallel, thereby halving the resistance losses. And this method certainly works.

By connecting two LEDs in parallel to the lamp instead of one, you will get more light with less energy and, accordingly, less heat.

Of course, this also extends the life of the LED.

You don’t have to stop and connect 3.4 diodes instead of one, it won’t be any worse.

And if there is not enough space for several LEDs, then you can install an LED originally designed for more power. For example, a 100-watt, 50-watt lamp.

It is in this way that the efficiency of the lamp can be increased several times, with the same energy consumption as the original source, but with less power, and operating at the limit of its capabilities.

Moreover, using no more than a third of the maximum power, you will forever forget what it is like to replace burnt-out LEDs.

At the same time, their operating efficiency and efficiency will increase noticeably.

Therefore, when purchasing LEDs, always be interested in the crystal size. After all, their cooling and internal resistance depend on this.

The rule here is that the more, the better.

The dream of a durable, practical and economical light source that shines and does not heat has become a reality thanks to the rapid development of semiconductor technologies. And, despite the fact that today the cost of an LED is relatively high, it may soon displace other, traditional light sources. At least for the next 15-20 years, he is already guaranteed a carefree future.

About LEDs as light sources capable of not only flickering Christmas tree garlands, but also to serve for full illumination of facades, interiors, local areas, parks and swimming pools, they started talking about five or six years ago. And the practice of their use in this area began just a couple of years ago. And although such a period for a global analysis of prospects is still relatively short, this light source may still very well displace others. If only because today traditional lighting sources have already reached their maximum luminous efficiency, and LEDs have only approached 10% of their capabilities. As an example, I would like to cite the fact that modern LEDs are already a hundred times brighter than the brightest LEDs just five years ago.

TO THE DEFINITION

The LED, or light-emitting diode, was invented in the early 1960s by Englishman Nick Holonyak. Therefore, this light source is also called LED (Light Emitting Diode).
An LED is an organic solid-state light source or semiconductor crystal that is made of layers of polymer semiconductor. LEDs do not contain glass, filaments, or replaceable parts. They are miniature, compact, powerful. In addition, they emit light with unique characteristics.

ABOUT ADVANTAGES AND DISADVANTAGES

LEDs have many advantages over classic light sources. Among them:

• Economical energy consumption. LED power consumption is maximum 5 W. Lamps with this light source consume 5-10 times less energy than lamps based on halogen and incandescent lamps of similar brightness. LED conversion efficiency electrical energy in light is an order of magnitude higher than the efficiency of a conventional incandescent lamp. For example, ordinary lamp A 100 W incandescent lamp has a light emission power equivalent to only 3-5 W. And an LED light source, producing the same power of light radiation, consumes not 100, but only 1.5 W. The high efficiency of LED electricity consumption is especially relevant in modern stage, since humanity’s growing needs for lighting require increased electricity production. This requires additional capital investments for the construction of power plants, the development of energy deposits and the subsequent disposal of production waste. In addition, an energy saving program is being implemented at the state level. And LEDs are an alternative, highly efficient light source that can meet lighting demand without increasing production and energy costs.

• Possibility of operation from low-voltage power supply. LED lamps can be installed in places where there is no mains power(2.8 V to 28 V DC).

• High efficiency. For an LED lamp, the efficiency is 75-90% (light). And only 10-25% is spent on heat generation. For comparison: an incandescent lamp efficiency of 5-10% is light. The remaining 90-95% goes to pointless heating of the environment.

• Practicality in operation. Due to the longevity of LEDs, there is no need for frequent replacement and maintenance of the installation.

• Sufficient radiation power. The brightness of an LED, exceeding neon, leads to a large increase in the distance of information perception by the human eye (this is due to the almost monochromatic radiation of the LED). For example, an LED with a power of only 1 W can illuminate a column 6 meters high.

• Lack of sensitivity to changes in electrical networks. The response time to changes in supply voltage for an LED is measured in tens of microseconds, which is significantly less than similar indicators for incandescent lamps. LEDs have low inertia and can operate in pulsed mode without damage.

• Wide range of colors. Due to the fact that radiation occurs in a narrow spectrum band, the efficiency of colored LEDs is much higher than the efficiency of an incandescent lamp with a filter of a similar shade. Primary LED colors: red, blue, green, amber, turquoise, orange, white.

• Dynamic color change. LED sources The lights are easily controlled by any electronics. They can be given almost any color and temporary programs work. And the LED radiation can be adjusted, creating beautiful dynamic and lighting effects. In addition to the static operating mode, colors can be mixed, obtaining up to 16 million shades, controlled, and also created various dynamic effects.

• Fire safety and user safety. LEDs practically do not heat up, so they do not create a fire hazard. In addition, their glow is free of infrared and ultraviolet radiation, which makes them the safest light source for the eyes.

• Environmentally friendly. LEDs do not contain mercury. And they do not require expensive disposal after the end of their service life.

• Wide range of applications. LEDs are relatively small, which allows them to be used almost anywhere, for example, placed inside almost any device, or to make an LED lamp of any shape, color and design.

LEDs have virtually no disadvantages. The only difference is that the price is high compared to traditional light sources. But the initial costs are recouped due to low energy consumption and low financial expenditure during the operation period. For example, operating LED lamps is 2.5-3 times cheaper than incandescent lamps.

ABOUT CAPABILITIES AND APPLICATIONS

The possibilities of LEDs are extremely wide. With their help you can:

• receive 100% light immediately when turned on;
• ensure uniform illumination of the surface;
• create bright, rich colors;
• create and adjust the brightness and color of light;
• create lamp designs without the need to replace lamps, as well as vandal-proof lamps;
• “hide” the light source, showing only the light, etc.

The range of applications for LEDs is quite wide. Their use, for example, is optimal when the power allocated for lighting is too low for other light sources. They can also become indispensable in places where frequent and problematic (due to inaccessibility) replacement of traditional lamps is undesirable. But they can be of particular interest to designers and architects, since they allow them to realize their most daring decisions.

LEDs are used for interior and exterior decoration, signboards, shop windows and indicators, architectural and decorative lighting, as well as cheerful decorative lighting for any holiday.
LEDs can be mounted in walls, steps, podiums; use as lighting for parking lots, walkways, landscapes, fountains and swimming pools.

Since LEDs are easily controlled electronically, precise direction of light, control and regulation of color and intensity of radiation, color mixing are possible (which, in particular, can be interesting for creating stage lighting, light paintings, graphics, panels).
LEDs, due to their monochrome nature, are unique generators of colored light. Moreover, the vibrant richness of colors is achieved much more effectively than if a light filter was used for standard light sources. Thus, with the help of LEDs, objects, space and surroundings can be freely “painted” with deep, vibrant and bright colors. Or change it by simply pressing a button on the control panel, creating a certain atmosphere in the room.

Based on LEDs, it is possible to produce lamps of any color, design, shape and configuration for domestic and industrial needs, as well as underwater use. This variety provides wide freedom of choice for any application: horizontal and vertical, hanging, recessed, etc.

Thus, using LED technologies you can create a unique architectural image or a unique and unforgettable atmosphere in places of recreation and entertainment; emphasize the individuality and unique appearance of the home and make working conditions in the office comfortable.

By appropriately selecting the semiconductor material and additive, it is possible to specifically influence the characteristics of the light emission of the LED crystal, primarily the spectral region of the emission and the efficiency of converting the input energy into light:

• GaALAs- aluminum gallium arsenide; It is based on red and infrared LEDs.
• GaAsP- gallium arsenide phosphide; AlInGaP - aluminum-indium-gallium phosphide; red, orange and yellow LEDs.
• GaP- gallium phosphide; green LEDs.
• SiC- silicon carbide; The first commercially available blue LED with low luminous efficiency.
• InGaN- indium gallium nitride; GaN - gallium nitride; UV blue and green LEDs.

To obtain white radiation with a particular color temperature, there are three fundamental possibilities:

1. Conversion of blue LED radiation by yellow phosphor (Figure 1a).

2. Conversion of UV LED radiation by three phosphors (similar to fluorescent lamps with the so-called three-band spectrum) (Figure 1b).

3.Additive mixing of emissions from red, green and blue LEDs (RGB principle, similar to color TV technology). The color hue of white LEDs can be characterized by the value of the correlated color temperature.

Most types of modern white LEDs are produced on the basis of blue ones in combination with conversion phosphors, which make it possible to obtain white radiation with wide range color temperature - from 3000 K (warm white light) to 6000 K (cold daylight).

Operation of LEDs in power circuits

An LED crystal begins to emit light when current flows in it in the forward direction. LEDs have an exponentially increasing current-voltage characteristic. They are usually powered by a constant stabilized current or constant voltage with a pre-connected limiting resistance. This prevents unwanted changes in the nominal current that affect the stability of the luminous flux and, in the worst case, can even lead to damage to the LED.
For low powers, analog linear regulators are used; to power high-power diodes, network units with stabilized current or output voltage are used. Typically, LEDs are connected in series, parallel, or in series-parallel circuits (see Figure 2).

A smooth decrease in brightness (dimming) of LEDs is carried out by regulators with pulse-width modulation (PWM) or reduction direct current. Using stochastic PWM, it is possible to minimize the interference spectrum (problem electromagnetic compatibility). But in in this case with PWM, interfering pulsation of the LED radiation may be observed.
The amount of forward current varies depending on the model: for example, 2 mA for miniaturized panel-mount LEDs (SMD-LEDs), 20 mA for LEDs with a diameter of 5 mm with two external current leads, 1 A for high-power LEDs for lighting purposes. The forward voltage UF usually ranges from 1.3 V (IR diodes) to 4 V (indium gallium nitride LEDs - white, blue, green, UV).
Meanwhile, power circuits have already been created that make it possible to connect LEDs directly to a 230 V AC network. To do this, two branches of the LEDs are switched on anti-parallel and connected to a standard network through an ohmic resistance. In 2008, Professor P. Marx received a patent for a circuit for regulating the brightness of LEDs powered by a stabilized alternating current(see Figure 3).
The South Korean company Seoul Semiconductors has integrated a circuit (Figure 3) with two anti-parallel circuits, (in each of which a large number of LEDs) directly in one chip (Acriche-LED). The forward current of the LEDs (20 mA) is limited by an ohmic resistor connected in series to the anti-parallel circuit. The forward voltage across each LED is 3.5 V.

Energy efficiency

Energy efficiency of LEDs (efficiency) is the ratio of radiation power (in Watts) to electrical power consumption (in lighting terminology, this is the energy output of radiation - i.e.).
In thermal emitters, which include classic incandescent lamps, to generate visible radiation (light), the coil must be heated to a certain temperature. Moreover, the main share of the supplied energy is converted into thermal (infrared radiation), and only ?e = 3% for conventional ones is transformed into visible radiation, and 7% for conventional ones. halogen lamps incandescent

LEDs for use in applied lighting convert the supplied electrical energy into visible radiation in a very narrow spectral region, and thermal losses occur in the crystal. This heat must be removed from the LED by special design methods in order to provide the necessary light, color options and maximum service life.
LEDs for lighting and signaling purposes have virtually no IR and UV components in the emission spectrum, and such LEDs have significantly higher energy efficiency than thermal emitters. With favorable thermal conditions, LEDs convert 25% of the supplied energy into light. Therefore, for example, for a white LED with a power of 1 W, approximately 0.75 W is due to thermal losses, which requires the presence of heat-dissipating elements or even forced cooling in the design of the lamp. Such management of the thermal regime of LEDs is of particular importance. It is advisable that manufacturers of LEDs and LED modules provided energy efficiency values ​​in the list of characteristics of their products

Thermal mode control
Let us remember that almost 3/4 of the electricity consumed by an LED is converted into heat and only 1/4 into light. Therefore, when designing LED lamps, a decisive role in ensuring their maximum efficiency optimization of the thermal regime of LEDs plays a role, in other words, intensive cooling.

As is known, heat transfer from a heated body is carried out due to three physical processes:

1. Radiation

Ф = W? =5.669?10-8?(W/m2?K4)??A?(Ts4 – Ta5)
where: W? – thermal radiation flux, W
? – emissivity
Тs – surface temperature of a heated body, K
Ta – temperature of surfaces enclosing the room, K
A is the area of ​​the heat-emitting surface, m?

2. Convection

F = ?? Huh? (Ts-Ta)
where: Ф – heat flow, W
A is the surface area of ​​the heated body, m?
? - heat transfer coefficient,
Тs – temperature of the boundary heat-removing medium, K
Ta – surface temperature of a heated body, K
[for unpolished surfaces? = 6...8 W / (m? K)].

3. Thermal conductivity

Ф = ?T?(А/l) (Тs-Та) =(?T/Rth)
where: Rth= (l / ?T?A) – thermal resistance, K/W,
Ф – thermal power, W
A – cross section
l-length - ?T – thermal conductivity coefficient, W/(m?K)
for ceramic cooling elements?T=180 W/(m?K),
for aluminum – 237 W/(m?K),
for copper – 380 W/(m?K),
for diamond – 2300 W/(m?K),
for carbon fibers – 6000 W/(m?K)]

4. Thermal resistance

The total thermal resistance is calculated as:

Rth par.com.=1/[(1/ Rth,1)+ (1/ Rth, 2)+ (1/ Rth,3)+ (1/ Rth,n)]

Rth afterword = Rth,1 + Rth, 2 + Rth,3 +....+ Rth,n

Summary
When designing LED luminaires, every possible measure must be taken to alleviate the thermal behavior of the LEDs through conduction, convection and radiation. Therefore, the primary task when designing LED lamps is to ensure heat removal due to the thermal conductivity of special cooling elements or the housing design. Then these elements will remove heat by radiation and convection.
The materials of the heat sink elements should, if possible, have minimal thermal resistance.
Good results were obtained with heat-removing units of the “Heatpipes” type, which have extremely high heat-conducting properties.
One of best options heat sink - ceramic substrates with pre-applied current-carrying paths, directly to which the LEDs are soldered. Cooling structures based on ceramics remove approximately 2 times more heat compared to usual options metal cooling elements.
The relationship between the electrical and thermal parameters of the LED is illustrated in Fig. 4.
In Fig. 5 shows a typical design powerful LED with an aluminum cooling element and a circuit of thermal resistances, and in Fig. 6-8 – various methods cooling.

Radiation

The surface of the lighting fixture on which the LED or module with several LEDs is mounted should not be metal, since metals have a very low emissivity. The surfaces of luminaires in contact with LEDs should, if possible, have a high spectral emissivity?.

Convection

It is desirable to have a sufficiently large surface area of ​​the lamp body for unhindered contact with ambient air flows (special cooling fins, rough structure, etc.). Additional heat removal can be provided by compulsory measures: minifans or vibrating membranes.

Thermal conductivity

Due to the very small surface area and volume of LEDs, the necessary cooling by radiation and convection is not achieved.

Example of calculating thermal resistance for a white LED

UF= 3.8 V
IF = 350 mA
PLED = 3.8 V? 0.35 A = 1.33 W
Since the optical efficiency of the LED is 25%, only 0.33 W is converted into light, and the remaining 75% (Pv=1 W) is converted into heat. (Often in the literature, when calculating thermal resistance RthJA make the mistake of assuming that Pv = UF? IF = 1.33 W - this is incorrect!)

Maximum permissible temperature active layer (p-n junction – Junction) TJ = 125°C (398 K).

Maximum ambient temperature TA = 50°C (323 K).

Maximum thermal resistance between barrier layer and surroundings:

RthJA= (TJ – TA)/ Pv = (398 K – 323K)/1 W = 75 K/W

According to the manufacturer, the thermal resistance of the LED

RthJS = 15 K/W

Required thermal resistance of additional heat-dissipating elements (cooling fins, heat-conducting pastes, adhesive compounds, board):

RthSA= RthJA – RthJS = 75-15 = 60 K/W

In Fig. 9 explains the thermal resistances for the diode on the board.
The relationship between the temperature of the active layer and the thermal resistance between the blocking (active) layer and the solder point of the crystal leads is determined by the formula:

TJ= UF ? IF? ?e? RthJS + TS

where TS is the temperature measured at the solder point of the crystal leads (in this case it is equal to 105°C)

Then, for the example under consideration with a white LED with a power of 1.33 W, the temperature of the active layer will be determined as
TJ = 1.33 W? 0.75? 15 K/W + 105°C = 120°C.

Degradation of emissive characteristics due to temperature load on the active (blocking) layer.
Knowing real temperature at the solder point and with data provided by the manufacturer, it is possible to determine the thermal load on the active layer (TJ) and its effect on radiation degradation. Degradation refers to the decrease in luminous flux over the life of the LED chip.

Effect of barrier layer temperature
Fundamental requirement: the maximum permissible temperature of the blocking layer should not be exceeded, as this can lead to irreversible defects of the LEDs or spontaneous failures.
Due to the specifics of the physical processes occurring during the operation of LEDs, the change in the temperature of the blocking layer TJ is in the range acceptable values affects many LED parameters, including forward voltage, luminous flux, chromaticity coordinates and service life.

Technical and economic indicators of lamps

The TEP of a lamp is significantly influenced by the type and quality of the optical systems of the lamp. The level of efficiency depends on the power factor of the ballast and the optical efficiency of the device, as well as the condition of the optics. A number of domestic equipment and most foreign samples have high coefficients. However, no matter how good these indicators are, the optics (transparent cover, diverging or converging lens and reflectors) become dirty during operation and undergo significant changes in surface structures, which leads to deterioration of parameters. This statement applies to all types of luminaires, regardless of whether ballasts are used or not.

In new lamps, optical efficiency ranges from 60 to 95%. As a result of practical observations and special laboratory examinations, it turned out that during the period of 1 year of operation, the optical efficiency decreases to 35% of its original value (and the main level of losses occurs in the very first days of operation). Within 2 years, optics lose from 50 to 65% of their original efficiency level.

The observed devices were operated outdoors (street lighting) on ​​the territory of the Republic of Tatarstan, under normal, non-extreme conditions. It is clear that if operating conditions require the operation of lighting equipment in conditions of increased dust or gas pollution, then the optical efficiency decreases at a faster rate.

*Measurements of optical and electrical properties were carried out by specialists from the TATLED Group of Companies at their own base.

(Luminous flux, Ф; Distribution of the total luminous flux over any 2 levels of luminous intensity or radiation angles within the radiation pattern, Ф(Ω),

Data on measuring equipment in Appendix 1.

As a rule, the task of protecting lamps (especially their internal volume) from unfavorable factors impact external environment is solved by manufacturers of lighting equipment by sealing between the housings of closed lighting devices and protective glass, as well as sealing wire entry points.

However, with more detailed study problems, it turned out that this was not enough to ensure proper insulation of the internal volume of the lamp. According to the laws of thermodynamics, in closed lighting devices there is a “breathing” effect associated with a change in air pressure enclosed in the internal isolated volume of the lighting device. When the light source of the device is turned on and the air trapped inside the device is heated, the pressure increases, and when it is turned off, the pressure drops. As a result of even an imperceptible defect in the seal, contaminated air is sucked into the internal cavity of the lamp. This phenomenon presents the possibility of dust, fibers and corrosive particles settling on the lamp bulb, reflector, inner surface, protective glass, lens and socket contact assemblies. As a result, the lighting capacity of the devices decreases and they themselves fail within a short period of operation (for example, in some areas of metallurgical production, lighting devices are replaced annually, significantly increasing the cost of operating the lighting system).

LED lamps do not have the above disadvantage. The fact is that the LEDs used in such lamps do not require reflective reflectors.

In lighting devices using conventional light sources, a reflective reflector is built in, the shape of which cannot always be adjusted in accordance with the requirements of light distribution. Unlike conventional lamps, LED devices use light sources that emit light energy not in all directions, but in one. The direction and intensity of the light flux is regulated by the location of the axes of the light emitter in a given direction and their number. The opening angle of the emitted radiation is adjusted using secondary optics (microlens).

Thus, the LED lamp is free from the disadvantages caused by losses in optical systems omnidirectional light sources used. That is, the Lumen/Watt ratio for LED lamps is more attractive.

Lumens measure the flow in all directions, i.e. in a solid angle of 4pi. One lumen is equal to the luminous flux emitted by a point isotropic source, with a luminous intensity equal to one candela, into a solid angle of one steradian (1 lm = 1 cd × sr)

A steradian is equal to a solid angle with its vertex at the center of a sphere of radius R, cutting out on the surface of the sphere an area equal to the area of ​​a square with side R (that is, R²). If such a solid angle has the form of a circular cone, then its opening angle will be approximately 65.541° or 65°32′28″).

If we assume that the calculated cone is directed directly at the illuminated object, then the rest of the light energy hits the illuminated surface through a reflector or optical lenses.
Candela (from Latin candela - candle), unit of luminous intensity of the International System of Units. Designation: Russian CD, international CD. Candela (unit of luminous intensity) - the intensity of light emitted from an area of ​​1/600000 m2 of the cross-section of a full emitter in a direction perpendicular to this section at an emitter temperature equal to the solidification temperature of platinum (2042 K) at a pressure of 101325 n/m2.

Based on the above, to compare TEC lamps with a conventional light source and an LED lamp, it is necessary to introduce a correction for the difference in the efficiency of optical systems.

Consider as concrete example widely used lighting device RKU15-250 using DRL lamps and LED lamp.

To determine real lighting performance indicators, we make the following calculations:

According to the manufacturer, the efficiency of the RKU15 lamp is 65%. The light source (DRL-250 (V) lamp) has a luminous flux level of 13,200 Lumens. We get the level of luminous flux actually emitted by the device: 65% of 13,200 lm = 8,580 Lumens.

It is also necessary to take into account the accelerated loss of the DRL luminous flux level in the first 1000 hours of operation. From the graph below (according to VNISI data) it is clear that during the first 1000 hours of operation, the level of emitted luminous flux decreases by 15-20% of the initial value. From here we get Фv = 6,864 Lumens. During the further period of operation, degradation occurs less intensively.

The lumen level curve of LEDs used in LED luminaires also has an uneven characteristic. However, as you can see from the graph below (courtesy of OSRAM Opto Semiconductors), after a short dip the level gradually increases (Golden Dragon plus diodes).

Chart of device ownership costs over 5 years

The data is given taking into account the constant cost of electricity. Taking into account the growth of tariffs predicted by the Ministry of Economic Development, the point of intersection of the cost level curves will occur earlier than the period obtained by calculations (presumably 4 years).

An example of the use of DRL lamps and LED lamps for road lighting. Thanks to a more rationally distributed light energy, the road surface illuminated by LED lamps (picture on the left) is flooded more evenly.

Conclusion: the optical properties of luminaires using LEDs are noticeably superior in lighting parameters to luminaires with conventional light sources.

CONTROL EQUIPMENT (CONTROL EQUIPMENT).

Ballasts (ballasts) are a special product that is used to start and maintain the operation of a light source.

Structurally, the ballast can be made in the form of a single block or several separate ones.

Depending on the type of light source, ballasts are divided into:

• Ballasts for gas discharge lamps
• Ballasts for halogen lamps (transformers)
• Ballasts for LEDs (LED drivers)

Depending on the type of device and operation of ballasts, there are:

• electromagnetic (EMPRA)
• electronic (electronic ballasts)

In addition to the optical parameters, the efficiency of a lighting device is significantly affected by the power factor parameter of the ballast.

For discharge lamp ballasts, this parameter (according to manufacturers) ranges from 0.6 to 0.9. The most effective today are electronic ballasts, since with the help of electronics the ability to ignite and control the glow can be done much more efficiently compared to inductive chokes. Ballasts for discharge lamps have been produced for a long time and, despite ongoing improvement, are well known to consumers, so they are not discussed in detail in this work.

In LED lamps, the ballast (LED driver) performs the function of a stabilizer direct current, voltage stabilizers and dimming (specialized).

Drivers can be divided into two main groups:

1. LED power supplies with constant stabilized output current (LED drivers) - designed to power LEDs (or LED lamps) connected in series.

2. Power supplies with stabilized constant voltage (LED transformers) - designed to power groups of LEDs that are already equipped with a current-limiting resistor, usually LED strips, rulers or panels.

In addition, since the industry produces LEDs designed for different meanings rated current, LED drivers are also divided according to this parameter.

The most common current values ​​are 350 and 700 milliamps.

The power factor of LED drivers from most manufacturers is 0.95. A separate LED requires a constant voltage of 2-4V and several tens of mA of current. A daisy chain array of LEDs requires more high voltage. The LED driver is the source of this voltage. It transforms the power supply of a household electrical network 110-240V AC voltage to low-voltage DC for powering LED systems.

There are increased requirements for the quality of LED control gear, since LEDs, being a semiconductor device, are extremely demanding on the quality of the power supply. Deviations from the specified parameters within 2-5% sharply affect the lighting and electrical properties of LEDs, and can lead to a significant reduction in the life of the crystal or phosphor.

Based on the foregoing, it is clear that the quality of LED control gear is initially high, and accordingly it is a product with high efficiency.

The vast majority of manufacturers declared values ​​are from 0.90 to 0.95. Simple measurements confirm these values.

For dimming (changing the brightness of LEDs), the principle is usually used pulse width modulation(PWM).

In terms of efficiency and degree of reliability, ballasts for discharge lamps and ballasts for LED lamps differ only in the quality of the circuitry and the used element base, which ultimately implies a difference in the cost of the product. High-quality and expensive ballasts of various types of lamps approach a single indicator (close to 1).

Appendix 2 and Appendix 3 contain reviews from organizations that have implemented LED lamps as prototypes.

Conclusion: the influence of ballast efficiency on the overall efficiency lighting fixture for discharge lamps and for LED lamps there is no noticeable difference, and is determined only by the price of the product.

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