What is an LED?
Light-emitting diodes are made of compounds containing gallium (Ga), arsenic (As), phosphorus (P), nitrogen (N), etc.
It changes the principle of incandescent lamp tungsten filament luminescence and energy-saving lamp tricolor luminescence and uses solid semiconductor chip as a luminescent material.
When the positive voltage is applied at both ends, the carrier in the semiconductor compounds and emits excess energy, which causes photon emission to produce visible light.
LED can directly emit red, yellow, blue, green, green, orange, purple, and white light.
LED is called the fourth generation lighting source or green light source.
It has the characteristics of energy-saving, environmental protection, long life, and small size.
It is widely used in various fields such as indication, display, decoration, backlight, general lighting, and urban night scene.
The power consumption of LED is quite low. Generally speaking, the working voltage of the LED is 2-3.6V.
Only a very weak current is needed to emit normal light.
Under the appropriate current and voltage, the lifetime of LED can reach 50,000 hours.
LED is made of non-toxic materials. Unlike fluorescent light containing silver, which can cause pollution, LED can also be recycled.
Luminous flux (unit: LM lumen)
Luminous flux refers to the brightness of the light source. Wattage is only the power of the lamp and has no direct relationship with brightness.
We usually say that the light is not bright enough, which refers to the flux of light. The old 100-watt incandescent lamp may have the same brightness as the 12-watt LED lamp, so the LED lamp is very energy-efficient.
So that the same LED lamp, or even the same brand of LED lamp, brightness may not be the same under the same wattage.
Illuminance (unit: lx Lux)
Illumination can be measured directly by an illuminometer. The unit of illumination is lux or lx.
It refers to the illumination of the object that is illuminated uniformly by light is 1 lux, when the luminous flux is 1 lux on an area of 1 square meter.
For example, when a lamp gets closer, it looks brighter, but it won’t look bright when getting away enough. The brightness (luminous flux) of the light itself hasn’t changed. What changes are the illumination we receive.
Many lighting designs are based on illumination as a strict standard. For example, the illumination of a football field needs to reach 300 lux. So the location, power, and quantity of light are all around the goal of 300 lux.
Chromogenic Index (CRI or Ra)
The concept of a chromogenic index is seldom mentioned in daily life. The higher the Chromogenic Index, the more realistic the color of the object is. The greater the color difference, the worse the color rendering of the light source. The color rendering index coefficient (Kaufman) is still a common method for defining the color rendering evaluation of light sources.
The color rendering of sunlight is 100. Artificial lamps cannot reach that high. In the national standard, the lights which the color rendering can be used at home. 90 has been applied to precision mapping. The color rendering above 95 is commercial professional-grade lamps.
There are two kinds of color rendering: faithful color rendering and effect color rendering.
Faithful color rendering can correctly represent the original color of the material and need to use a high color rendering index (Ra) light source. The color rendering is the best when its value is close to100.
The effect of color rendering clearly emphasizes the specific color. To express the beauty of life, we can add color to enhance the effect of color rendering. Low color temperature light source can make the red more bright; medium color temperature light source can make the blue cool; high color temperature light source can make the object look cold.
Color temperature (unit: K)
Color temperature is a measure of the color component of light. The higher the color temperature, the colder the light; The lower the color temperature, the warmer the light. Warm light is generally considered good for life and white light is considered good for work. So many books suggest different color temperatures should be used for each area of your home.
Usually, the “yellow light” bulb or lamp belt used in the home should be called warm white. Its color temperature is between 2700 and 3300K. The white light of the daylight tube is white, and the color temperature is between 4500 and 5000. The color temperature of the cold white used in the outer wall of the commercial building is between 5500 and 7000K.
Classification of LED Light
LED light is divided into the outdoor lighting, indoor lighting, and special lighting.
Application of street lamp: highway, main city road, viaduct, overpass, square, etc.
Tunnel light usage: tunnel, toll station, viaduct bottom, etc.
Application of flood light: buildings, landmarks, sculptures, parks, docks, billboards, stadiums, etc.
Landscape lighting: building facade, sculpture, stone statue, pedestrian street, square, path indicator, lawn, park, square, small square, block, pedestrian area, aquarium, pool, fountain, swimming pool lamp.
Emergency light: as backup lighting.
Car lights: brake lights, headlights, auxiliary lights, interior atmosphere lights, etc.
Stage lamp: stage, entertainment place, etc.
Plant growth lamp: used to promote plant growth.
Fishing lamp: gather fish by light and make it easier to catch fish.
Other special lamps: flashlight, horse lamp, headlamp, etc.
Downlight: the adornment lamps and lanterns inside domestic condole top.
Fluorescent lamp: home, office, store, etc.
Light belt/strip: family, shop, shopping mall, etc.
Bulb: home, hotel, shopping mall, etc.
Panel light: home, office, shop, shopping mall, etc.
Spotlight: home, office, shop, shopping mall, etc.
High bay light: mostly used in factories, warehouses, and another lighting environment.
Composition of LED lamps
Any LED lamp can be summarized into three parts: LED chip, LED driver power supply and lamp shell (including reflective material, heat dissipation material, wire material, a thermally conductive material, etc.)
Types of LED Chips
At present, there are three types of LED lamps on the market: LED plug-in, LED integrated chip, and LED patch.
LED Plug-in Lamp Beads
Nowadays, there are few LED lamps with this kind of chip. The advantage is the low cost. The disadvantage is the case that the parameters of all aspects are not very good. Now, it is rarely seen that this kind of LED chip is on the lamps.
LED Integrated Chip
Before 2014, most outdoor LED lamps and lanterns adopt this kind of LED light source. This kind of integrated package can achieve 200 W single power. Chips under 150 W usually use 10 series of N-parallel circuits (for example, 50 W light sources are 10 series and 5 parallels, 100 W is 10 series and 10 parallel). More than 150 W light beads usually use 14 series of bright beads. For example, 200 W is 14 series and 14 parallels. By narrowing the current, the heating effect of the chip is reduced, so that an integrated LED light source can achieve 200 W high power.
The weakness of the LED integrated chip is also apparent. The requirement of heat dissipation and driving power for the lamp shell of distinct high power integrated chip is also very high. Because the chip package is very dense, the heating of the LED chip will be very large. For instance, 200 W single integrated chip, either choose large aluminum shell for heat dissipation or need to use it. Certain copper tubes for heat dissipation, the corresponding driving power supply must also be able to work generally under long-term elevated temperature conditions. (Many lamp damages are a series of other problems arising from heat dissipation.)
After 2014, the LED lamp mostly uses the LED patch, because the patch area is compact and the heat dissipation effect is good. With the continuous upgrading of technology, the chip’s lumen is getting higher and higher, which makes the patch gradually replace the LED integrated chip in the field of road lighting and factory lighting, and now it is the mainstream soft source.
In the range of 2.8-3.6V, 3014 (0.1W, 30ma), 3528 (0.06W, 20ma) 2835 (0.2W, 60ma) 5630 (0.5W, 150ma) 5050 (0.2W, 60ma), 3030 (1W, 350ma) 4014 (0.2W, 60ma) 3535 (1-3W, 350-1000ma) are all conventional power, as for other kinds of patches. There are 0603, 0805, 1206, 0402, 2016, 3020, and so on.
Household LED lamps and lanterns are generally heat dissipation from aluminum substrates because of their low power. High power LED housing is all aluminum products.
As for the dissipation of the whole aluminum lamp body heat, the higher the power, the larger the volume and weight. It is challenging to maintain the temperature of aluminum products with heat dissipation exceeding 200W. Copper tubes need to be used for heating dissipation. Copper tubes are attached to the light source and emitted onto the aluminum lamp body. The higher the power is, the better the thermal conductivity system is needed for heat dissipation.
Because the input voltage of LED is 2.8-3.6V, an LED driver is needed to reduce the voltage, from high voltage to low voltage. Because the voltage used in the world is different, all LED driver is internal voltage. For example, the input voltage of the HLG model of the Mingwei driver is 100V-305V.
According to different power, the separate series-parallel driver is selected to the output voltage and current. The LED driver is like the heart of the LED lamp. Selecting a suitable driver can make the LED lamp a more stable and longer life.