How to choose LED lamps?

Release date: 2017-11-20 Source: Foreign station sharing:

 LED will definitely become the fourth generation of lighting, its development momentum is getting more and more fierce, the main advantages are: energy saving and environmental protection, long life, no stroboscopic does not hurt the eyes, does not attract mosquitoes. As long as the heat dissipation design of the high-power LED luminaire is good enough, the life of 3-5 million hours is no problem (the definition of life is: because the LED is a semiconductor component, its wafer is affected by temperature will produce light decay, when the luminous flux of the LED is When the light decay is reduced to 30% of the initial luminous flux, basically the secondary LED lamp has no illumination meaning, that is, the life is summarized. Although the LED lamp can still be lit at this time, the brightness has been seriously reduced, so the LED lamp is very cool. Important is important).
The object that you said by the LED light will be biased because of the lack of a color in the spectrum, which is the wrong idea. Quite simply, color TV sets (CRT) are not just a mixture of three primary colors (red, green, blue) to get a variety of colors. Lighting uses a large number of high-power white LEDs, mainly blue-light wafers to stimulate the phosphor to mix and get white light.
I think you said that the objects that are illuminated will be color cast, mainly due to two factors:
1. The LED color rendering index used is too low, so that the emitted light does not reflect the true color of the object. (The ability of the light source to color the object is called color rendering, the color rendering index Ra is 100, and the color rendering is best.) If the LED color rendering index reaches 80-85, it is already very good, and it can be used indoors.
2. The color temperature of the LED used is not good. A simple understanding can be considered as the color of light. If the color temperature is low, the light will be greenish and reddish, and if it is too high, it will be blue. It is not suitable for indoor lighting. Therefore, indoor lighting is a very important parameter for the color temperature of LED lights. LED generally defines a color temperature of 2700K-4000K for warm color, 4000K-5000K for natural white, 5000K-6700K for white, warm white and natural white temperature will give people a warm, warm feeling, suitable for hotels, hotels, and bedroom. The positive white gives people a cool and refreshing feeling. It is used in the office and the living room is more illuminated (fluorescent lamps generally have more such color temperatures).
The brightness is equivalent to 100W energy-saving lamps, it depends on the efficacy of the LED lamps used (lumen / watt, lm / w), the same wattage, the higher the efficiency of the LED lamps, the higher the brightness. Generally, when the luminous efficacy of an LED lamp reaches 70 lm/w, as long as 50-60 W can exceed the brightness of a 100 W energy-saving lamp.
In addition, I have never seen the brightness of 100W energy-saving lamps in indoor lighting. At least our company does not produce LED indoors of 60W or more.
The last thing to say is to buy LED lamps to pay attention to light efficiency, color temperature, color rendering index, light decay. The first three are common parameters for all luminaires, and the final light fading is a unique property of LEDs as a semiconductor.
In addition, some people have the following misunderstandings when choosing LED lights!
Misunderstanding 1, the expectation of the actual service life is too high.
LED manufacturers expect LED life to reach 100,000 hours MTBF
(Average time between failures, the standard used by traditional luminaire manufacturers to measure lamp life). But like all basic light sources, LED
Luminous flux lumens also decay over time. So although the LED illumination time can be very long, MTBF is not the only consideration for determining the service life.
The attenuation of LED lumens is affected by many environmental conditions such as ambient temperature, humidity and ventilation. Lumen attenuation is also affected by control, thermal management, current levels, and many other electrical design considerations (cited by CK Corporation, USA).
Many salesmen may give customers some ambiguous information for some reason when selling LEDs, which is misleading. For example, the service life of LEDs is about 100,000 hours, and the 100,000 hours here refers to the life expectancy of LEDs. As the light source of illumination, the brightness of the lamp has a process of gradually decaying and darkening (such as fluorescent lamps, energy-saving lamps), which is referred to as light decay. On application-level LEDs, when the light decay exceeds 50%, the human eye can clearly feel the change in brightness. At this time, the brightness of the product is not suitable for illumination. Many manufacturers and contractors use low-cost LEDs for three months to half a year. It is often found that the brightness of LEDs is not as bright as when they were installed, or even close to nothing. It is precisely because LED light is not considered. In summary, when we buy LEDs, we should pay attention to its light decay speed, not the use time.
Misunderstanding 2, the actual luminous angle is taken as an effective angle.
The illumination angle of the LED is divided into an effective angle and an actual illumination angle. The angle at which the luminous intensity value is half of the axial strength value and the angle of the luminous axis (normal) are effective angles. The angle of view of the half angle angle (or half power angle) is the actual light angle. Angles other than half of the axial strength are not considered effective angles in practical applications because the light is too weak. (The picture below shows the side view of the piranha particles. The angle between the solid line and the dotted line is not included in the effective angle.)
Therefore, we should pay attention to the actual illumination angle of the product when purchasing the product. When calculating the quantity of products used in the project, the actual illumination angle can be used as the reference value.
Misunderstanding three, the higher the power, the higher the brightness.
The brightness of an LED is measured by the intensity of illumination, which is the luminous intensity in the direction of the normal (to the axis of the cylindrical luminous tube), that is, the luminous flux emitted by the unit solid angle, in units of candlelight (Candela,
Cd). Since the luminous intensity of a general LED is small, the luminous intensity is usually measured in millicald (mcd). Generally speaking, the light source emits its luminous flux with different intensity in different directions, and the visible light radiation intensity emitted by the solid angle in a specific direction is called light intensity, which is simply referred to as axial brightness.
The concept of electric power is introduced from the amount of work done in equal time. The current is fast and the electric power is large; the current is slow, the electric power is small, or the electric work is more in the same time, the electric power is larger. On the LED, the higher the power, the higher the brightness of the product. Taking Yimei Electronics' three-lamp red LED as an example, when the axial brightness is 1200mcd, the current is 40ma and the power is 0.48W; the three-lamp white LED has the same brightness, the current is 18ma, and the power is only 0.24W; The power of the two lights at the same brightness is different. So what we pay attention to when buying LEDs is its axial brightness, not power.
Misunderstanding 4, about the purchase of white LED modules.
  1. High-brightness (blue-green) white LEDs are sensitive to static electricity and are determined by the characteristics of the LED itself. Exceeding the maximum forward DC current and maximum reverse voltage it can allow can cause damage or breakdown of the LED. For example, a three-lamp LED module, each lamp will have an anti-static resistor, plus a resistor for current limiting, a total of four. The anti-static resistor can effectively suppress the damage caused by static electricity to the LED. 

 The current limiting resistor mainly limits the amount of current that the entire module passes. This design can effectively improve the overload resistance of the LED. 

Label: How to choose LED lamps?

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