In the near future, bright LEDs will displace lamps in the emergency lighting of public places and in transport - in airplanes, trains, cars. After all, already now the development of technology and cheaper production has led to the fact that China is installing quite bright LED lighting for roads and streets. Naturally, this provides significant energy savings. But powerful bright LEDs cannot work without special optics. A number of companies produce such optics for high-power LEDs, otherwise the LED radiation will have the wrong light angle that is required. Many campaigns are engaged exclusively in LED optics. They produce a wide range of optical systems that are consistent with products from leading LED manufacturers. There are optics with different directional diagrams, including elliptical, as well as optics for three LEDs, which allows you to create RGB modules. The cost of good optics for one powerful LED reaches 5ue.
It is well regulated, but not by changing the voltage on it - it is absolutely impossible (!) To do this, but by the method of pulse-width modulation, which requires a special control unit or simply by adjusting the current. The PWM method consists in the fact that the LED is supplied not with a constant, but with a pulse-modulated current, while its frequency is several kilohertz, and the width of the pulses and pauses between them varies. So the brightness of the LED becomes controlled.
Modern bright provide:
Greater light output with small dimensions;
- lack of elements with high temperature;
- MTBF of up to 100,000 hours, or 10 years of continuous operation;
- energy consumption is reduced by 90%;
-high resistance to mechanical stress;
- wide color gamut radiation;
- lack of toxic substances in an LED.
Very pleased with the rapid decline in prices for LED products. For example, a powerful bright LED at 50 watts Edistar 50W, has fallen in price almost half in half a year! A ten-watt Golden X can be ordered in just 10ye.
Now, probably, only the deaf did not hear about LED lamps and super-bright LEDs. In the environment of radio amateurs, a super-bright LED has long been an object of close study and the main element of home-made innovative devices. Yes, this is not surprising, superbright LEDs are interesting primarily for their efficiency and good light output characteristics. LEDs have good mechanical strength, do not be afraid of vibration and shaking. It is not for nothing that powerful LEDs are increasingly used in the automotive industry.
Another important positive quality of LEDs can be considered that they begin to emit instantly after power is applied. Fluorescent lamps, for example, are inferior to LEDs in this regard. For long-term operation of the fluorescent lamp, a hot start is recommended when preheating of the filament occurs. The lamp turns on after a few seconds.
In the early nineties, Nichia introduced the world the first LED in blue and white. Since then, a technological race has begun in the production of super-bright powerful LEDs.
The LED itself cannot emit white light, since white light is the sum of all colors. Light emitting diode emits strictly defined light wavelengths. The color of the LED radiation depends on the width of the energy gap of the transition, where the recombination of electrons and holes occurs.
The energy gap is in turn dependent on the material of the semiconductor. To get white light on a crystal blue LED a phosphor layer is applied, which under the action of blue radiation emits yellow and red light. The mixture of blue, yellow and red produces white light.
This is one of several widespread technologies for producing white light through light emitting diodes.
The supply voltage of superbright white LEDs, as a rule, lies in the range from 2,8 before 3,9 volt. The exact characteristics of the LED can be found in the datasheet.
Powerful superbright white LEDs, although affordable, are still expensive compared to the red and green LEDs, so you should pay attention to using them in lighting installations quality LED power.
Despite the fact that the resource of LEDs is quite large, any light emitting semiconductor very sensitive to overcurrent. As a result of overloads, the LED can maintain operability, but its light output will be significantly less. In some cases, a partially working LED can cause failure of the remaining LEDs that are connected with it.
To exclude overloading of LEDs, and, consequently, the output of their system, apply power drivers on specialized microcircuits. The power driver is nothing but a stabilized current source. To adjust the brightness of the LEDs, pulse modulation is recommended.
It is possible that in the near future manufacturers of high-power LEDs will embed a current stabilizer chip directly in the design of a high-power LED, similar to flashing LEDs ( blinking led ) in which the pulse generator chip is integrated.
A light emitting diode can work for decades, but provided that the light-emitting crystal will not become very hot due to the flow of current. In modern high-power LEDs, the supply current can reach more 1000 mA (1 Amp!) At supply voltage from 2,5 before 3,6 – 4 volt. These parameters are, for example, powerful LEDs Lumileds . To remove excess heat in such LEDs, an aluminum radiator is used, which is structurally combined with the LED crystal. Manufacturers of high-power white LEDs also recommend installing them on additional radiators. The conclusion is obvious - if you want long-term operation of the LED - provide good heat dissipation.
When installing high-power LEDs, you need to remember that the heat-conducting base of the LED not electrically neutral. In this regard, it is necessary to provide electrical isolation of the bases of the LEDs when mounted on a common radiator.
Since the typical supply voltage of superbright LEDs is 3,6 volts, then such LEDs can be easily used for LED flashlights in conjunction with rechargeable batteries of the format AA. To power the LED, you need 3 series-connected batteries with a voltage of 1,2 volt. In total, the voltage will be just what is needed 3,6 volt. In this case, no voltage converters are needed.
The still high price of high-power LEDs is associated with the complexity of manufacturing a high-power LED. The cost of modern technological installations, which produce crystals of high-power LEDs by epitaxial technology, is 1.5 - 2 million dollars!
Structurally powerful LED is a rather complex device.
The figure shows the device of a superbright LED Luxeon III by Lumileds, with a power of 5 watts .
As can be seen from the figure, modern superbright LED is a complex device that requires many manufacturing steps.
Currently, manufacturers of high-power LEDs are trying various LED manufacturing techniques using various materials and components. All this is aimed at reducing the cost of LEDs and ensuring the necessary product quality.
It should be noted that a powerful LED, manufactured with a violation of the technological process and the use of low-quality materials, loses its calculated light output after some time. As a rule, such LEDs are cheaper than analogues. Cheap LEDs for the first 4000 hours of operation lose their brightness on 35% . This is due to the fact that the epoxy material of the LED bulb turns yellow, and the emissivity of the blue LED chip and the phosphor layer deposited on it also decrease. At high-quality LEDs for 50 000 hours of use, the brightness decreases by no more than 20% .
If the use of LEDs was unprofitable for humanity, then only a limited circle of scientists would know about them. But the source with a fundamentally new type of radiation was very effective. Over time, small crystals began to combine several pieces in one case, they also learned to grow super crystals of larger sizes. As a result, we got ultra-bright LEDs, or, as they are also called, super-bright LEDs with the widest possible application.
The elemental LED itself is designed for voltages of more than 3-5 volts. Its characteristics make it possible to use such an element for display purposes and for decorative lighting. However, scientists managed to develop more powerful devices using a number of tricks. So the light appeared superbright super LEDs at 12 volts. Using the driver, a 12-volt device can be connected to a higher voltage, including a 220-volt network.
Impulse brightness change
The main advantage that a super-bright super LED at 12 volts has is its small energy appetites and at the same time, bright light. An additional advantage is the controlled change in the brightness of the LEDs, for which a controller is used. It turns out that a device that uses ultra-bright LEDs can reduce or increase the intensity of its radiation.
To control the brightness of the LEDs, pulse width modulation is used. With this method, you can reduce the brightness by periodically turning off the light bulb. The lamp pulsates, and the pulsation parameters will determine the intensity of its glow.
This principle of operation allows you to expand the capabilities of high brightness LEDs. As a result, we get functional:
- flashlights;
- car lights;
- light alarm;
- home lights.
Note that the alarm uses a blinking LED at 5, 12 and even 14 volts, which helps to draw attention to the windows, the counter or the cash register window. Low voltage devices are also used. The flashing LED is slightly different than a regular indicator light. In the case where the crystal is located, a pulse generator chip is placed.
Most often, super-bright 12 volt LEDs replace halogen lamps that provide directional light. That is why, producing lamps using LEDs, they make the standard base E14, GU10 and some others.
Important Features
All superbright sources have the same light characteristics as conventional LEDs:
- light flow;
- brightness;
- light output;
- illumination
When installing a 12-volt LED lamp on a particular device, it must be understood that its effectiveness depends on the radiation wavelength or, more simply, on color. Here is a table showing the dependency.
But studying these characteristics, not every person will be able to understand which device is right for him. It is much easier to determine by looking at the electrical parameters: voltage, maximum forward current, power of the device.
In addition, there are other characteristics. Superbright LEDs can be created on the basis of a single crystal or be multi-chip. Characteristics such as wavelength and color temperature are responsible for the color of the glow. Important parameters are the angle of light, the size of the housing, and the number of LEDs in one lamp.
The development of new models has led to the emergence of another distinctive feature - the shape of the case. A popular case for ultra-bright 12-volt LEDs is the Piranha, which has four outputs. There are also two-pin models and surface mount models.
Each model of the device has its own table of parameters, having looked into which you can find out the features of this device.
A few caveats
The main problem in the production of super-bright LEDs is the problem of heat dissipation. The LED must not overheat, otherwise the light intensity will irreversibly decrease. Superbright high-power devices are especially susceptible to overheating, therefore, when installing independently, it is necessary to ensure their cooling with a radiator.
Pay special attention to electrical parameters, not allowing connections to voltages that are higher than those specified in the instructions, and providing only the permissible current. Thus, superbright sources can shine as long as possible.
Be careful with the copper terminals, as their kink or severe deformation will cause the signal strength to change.
Lighting devices, where superbright LEDs are used as light sources, will not surprise anyone. The demand for such devices is constantly growing, this is directly related to the low power consumption of these devices. Considering that about 25-35% of consumed electricity is spent on lighting, the savings will be very noticeable.
But given the relatively high cost of super-bright LEDs, due to their design features, it is not yet timely to talk about a complete transition to this type of lighting. According to experts, this process will take from 5 to 10 years, it will be so much needed for debugging and implementation of new technologies.
The efficiency of the lighting device is considered to be the ratio of the generated light flux (measured in lumens) to the consumed electricity (watts). A high-quality lamp with a filament has an efficiency of about 16 lumens per watt, fluorescent (energy-saving) - four times more (64 lm / W), for long day lamps this figure is around 80 lm / W.
The efficiency of superbright LEDs, mass-produced at the moment, is about the same as that of fluorescent lamps. Please note that we are talking about mass production. As for the theoretical limit for superbright LED sources, it is defined by a threshold of 320 lm / W.
As many manufacturers promise, in the next few years, efficiency can be increased to 213 lm / W.
Influence of design features on cost
For the manufacture of superbright LED light sources, one of two methods can be used:
- to obtain light close in spectrum to white, three crystals are used installed in one housing. One is red, the second is blue and the third is green;
- a crystal emitting in the blue or ultraviolet spectrum is used; it illuminates the lens coated with a phosphor; as a result, the radiation is converted into light that is close to natural in the spectrum.
Despite the fact that the first option is more effective, its implementation is somewhat more expensive, which negatively affects prevalence. In addition, the spectrum of light emitted by such a source is different from natural.
The devices manufactured by the second technology have less efficiency. It is also worth considering that the phosphor contains a composite composite of cerium and yttrium, which are complex in composition, which themselves are expensive. Actually, this explains the relatively high cost of superbright white LEDs. The design of such a device is shown in the figure.
Designations:
- A - printed conductor;
- B - base with increased thermal conductivity;
- C - protective housing of the device;
- D - solder paste;
- E - LED crystal emitting ultraviolet or blue light;
- F - phosphor coating;
- G - glue (can be replaced by a eutectic alloy);
- H is the wire connecting the crystal and the output;
- K is the reflector;
- J is the heat sink base;
- L - power output;
- M is the dielectric layer.
Mounting Features
The operation of superbright LEDs is affected by the degree of heating of the crystal and the pn junction itself. The life of the device directly depends on the first, and the level of luminous flux on the second. Therefore, for the long service life of superbright LEDs, it is necessary to organize a reliable heat sink, this is done using a radiator.
It should be noted that the heat-conducting bases of these semiconductors, as a rule, conduct electricity. Therefore, when several elements are installed on one radiator, care should be taken about reliable electrical insulation of the bases.
The rest of the installation rules are almost the same as with conventional diodes, that is, the polarity must be observed, both when installing the part itself and when connecting the power.
Power Features
Given the relatively high cost of super-bright LEDs, it is very important to use reliable and high-quality power sources for their operation, since these semiconductor elements are critical to current overload.
After an abnormal mode, the device may remain operational, but the power of the emitted light flux will be significantly reduced. In addition, such an element is likely to cause damage to other, jointly connected LEDs.
Before talking about drivers for super-bright LEDs, we will briefly talk about the features of their power supply. First of all, it is necessary to take into account the following factors:
- the power of the light flux emitted by these elements directly depends on the magnitude of the electric current flowing through them;
- superbright LEDs are characterized by a non-linear I-V characteristic (volt-ampere characteristic);
- temperature has a strong influence on the I – V characteristics of these semiconductor devices.
The change in the I – V characteristic at the temperature of the semiconductor element (superbright smd LED) is 20 ° C and 70 ° C.
As can be seen from the graph, when a stable voltage of 2 V is applied to the semiconductor, the electric current passing through it changes depending on the temperature. When the crystal is heated to 20 ° C, it will be equal to 14 mA, when the temperature rises to 70 ° C, this parameter will correspond to 35 mA.
The result of such a difference will be a change in the power of the light flux at the same supply voltage. Based on this, it is necessary to stabilize not the voltage, but the electric current passing through the semiconductor.
Such power supplies are called LED drivers, they are ordinary current stabilizers. This device can be purchased ready-made or assembled on your own, in the next section we will provide some typical driver schemes.
Homemade LED Driver
We bring to your attention several options for drivers based on specialized chips of the Monolithic Power System company, the use of which greatly simplifies the design. The schemes are given as an example, a full description of the typical inclusion can be found in the datasheet on the microcircuit.
Option one based on the MP4688 buck converter.
This driver can work with voltages from 4.5 to 80 V, the maximum output current threshold is 2 A, which allows the luminaire to be powered by ultra-bright high-power LEDs. The level of electric current passing through the LEDs is regulated by the resistance R FB. The implementation of PWM dimming with a frequency of 20 kHz allows you to smoothly change the electric current flowing through the LED.
The second version of the driver is based on the MP2489 chip. Its compact housing (QFN8 or TSOT23-5) makes it possible to place the driver in the MR16 base used by halogen lamps, which allows replacing the latter with LED ones. A typical MP2489 connection diagram is shown in the figure.
The above circuit allows you to turn on two parallel LEDs, each of which has an operating current of 350 mA.
The latest driver based on the MP3412 chip, which can be used in portable flashlights. A distinctive feature of this scheme is the ability to work from a AA AA battery.
Superbright LEDs are sources of LED lighting with a power of 1 W or more with a current of 300 mA and a high brightness. A 10 Watt LED is obtained by using 10 such light emitting diodes in the form of a matrix.
NEW !!! 3D LED LUMINAIRES - There is always a place for magic in life ...80 Watt LED Array.
How the superbright LED is arranged
An ultra-bright LED has the same design as a regular one, with the only difference being that light-emitting crystals are mounted on a special base in it, and a powerful super-bright led has a heat sink in the design. In all other respects, this is the same light-emitting diode with a p-n junction, which creates optical radiation as a result of the flow of electric current.
Varieties
It is widely used in fixtures due to the white color of the glow. The power of this led can reach 1W, so its body has a heat sink.
In the photo we can see how the LED SMD 5050 looks.
Characteristics
The most important of all characteristics is the operating current. Ultra-bright powerful LEDs operate on direct current, and exceeding its value leads to failure of the led. The average operating current of a superbright is 15 - 20 mA, the current of a powerful ultrabright LED can reach 1A.
The operating voltage (hereinafter U) is the value of the voltage drop across the LED. Light emitting diodes are available with a working U of 1.5 - 4 V. Diodes of different colors have different U (the lowest have infrared diodes - 1.5-1.9 V, and the highest - white diode - 3-3.7 V). One driver with a constant output U \u003d 12V can connect, for example, four light-emitting diodes with a working U \u003d 3V or twelve LEDs with a working U \u003d 1V.
The average power rating for ultra-bright LED sources is 0.2-0.3 W, and for powerful super-bright sources - 1 W.
If the current and voltage are indicated on the box of a powerful LED, but the power is not indicated, it is quite easy to determine it by multiplying the indicated values \u200b\u200bamong themselves.
To obtain the necessary interior lighting, important indicators will be: the color of the glow, the scattering angle, the light flux.
Superbright powerful LEDs are presented in the following colors: amber, orange, blue, green, red and white. In turn, white can give out cold white light (5000 - 7000K), white (3500-5000K), warm white (2700-3500K).
The dispersion angle varies from 15º to 120º depending on the type. The smallest scattering angle has the series in a standard round casing, and the largest is the PLCC series. The use of superbright LEDs with different scattering angles makes it possible to set the necessary accents in the interior.
Luminous flux plays an important role in obtaining a given level of illumination of a room.
Power Features
Before you need to carefully study what current and voltage it is designed for. The ultra-bright ones are connected through a driver, which makes it possible to stabilize the current necessary for the normal operation of the LED. A driver with an output voltage of 12V is connected to a 220V network.
Below is the simplest diagram of connecting several LEDs through a driver.
Mounting Features
The main condition for installing and connecting led is the need to observe the polarity of the power supply.
Powerful superbright LEDs need additional cooling, because during operation they heat up intensively.
In powerful ultra-bright LEDs, the crystal heating temperature affects the normal operation of the super-bright LED, so when installing it, it is necessary to make a heat sink, which can be done using a radiator.
The heat-conducting bases used are conductors of electricity, therefore, when installing a light-emitting diode, it is necessary to ensure their electrical insulation.
In addition, a light emitting diode is a fragile product; it should be carefully installed to avoid deformation of its case.
Advantages and disadvantages
Superbright LEDs are becoming increasingly popular in the lighting market. The reason lies in the advantages that these light sources have:
- long service life (50 000-100 000 hours);
- high profitability;
- resistance to voltage drops;
- the ability to work at low ambient temperatures;
- compactness. Superbright LEDs are small in size, which allows them to be mounted in very small devices;
- environmental friendliness (lack of mercury, gas vapors or other hazardous substances);
- shock resistance and vibration resistance;
- lED technologies provide a wide variety in the design of interior, decorative lighting, as well as digital control of color and light intensity;
- resistance to repeated inclusions.
As you can see, the operating parameters of such devices compare favorably with other light sources. But besides the advantages, there are some disadvantages:
- high price, significantly increasing the payback period of the lighting device;
- low technical characteristics in low-quality products;
- the need for drivers, which increases the cost;
- the inability to use dimmers for all types of superbright LEDs. The device of these regulators is more complicated than for traditional light sources, which also affects their cost;
- declared color rendering names do not always correspond to real characteristics;
- small angle of light scattering;
- difficulties in obtaining uniform lighting due to the unique characteristics of each LED, etc.
Despite these shortcomings, with the right approach to the selection and installation, some of them can be leveled.
Application features
Today, thanks to the positive qualities, superbright LEDs are widely used:
- as light-emitting elements in traffic lights, road signs and LED screens;
- in the automotive industry (lighting and indication devices inside the car and outside); There are kits in which ultra-bright 12V LEDs are ready to be connected to the vehicle’s power circuit;
- in the advertising field;
- in landscape lighting, lighting of residential and public buildings, etc.
LED traffic light - not uncommon in the modern world
Summary
Superbright LEDs allow you to get a large luminous flux with low power consumption. Such properties will make it possible to solve the problem with high energy costs for lighting, which today remain significant, as well as create the necessary level of lighting inside buildings and outside.