LED ceiling light and its power supply knowledge

- Feb 12, 2021-

1. The problems and shortcomings of ordinary ceiling lamps


  2.1 Low luminous efficiency


  The energy-saving lamp with ballast has only 55lm/W, and the highest high-power U-type is only 80lm/W. And because all these ceiling lamps mostly use T5 tubes, which are bent into various shapes. But no matter what shape it is finally bent into, it emits light in 360 degrees, and the upward 180 degrees of light must be reflected back to become useful light. This reflection process will lose a lot of light. Therefore, the luminous efficiency of the lamps must be discounted at least 70%. That is, the above-mentioned light effect has to be multiplied by 0.7. And in actual use, its brightness decays quickly with time. For example, a Philips 32W circular T5 tricolor tube YH32RR16 has a color temperature of 6500ºK, a luminous efficiency of 67lm/W, and a total lumens of 2150lm. In fact, only 70% of the light can be used. That is only 1500lm.


  2.2 Contains mercury

Mercury has a very low boiling point and can evaporate at room temperature. After a waste and discarded fluorescent lamp is broken, it immediately emits mercury vapor to the surroundings, instantly making the mercury concentration in the surrounding air reach 10-20 mg/m3, which exceeds the maximum allowable concentration of mercury in the air specified by the state (0.01 mg/m3) M) 1000 to 2000 times, the human body inhaling 2.5 grams of mercury vapor is life-threatening. Moreover, the permeability of liquid mercury is extremely high, and when it falls underground, it will immediately seep into the ground and pollute groundwater. One milligram of mercury is enough to pollute 5454.5 kilograms of drinking water, making it fall short of safe drinking standards. Now desperately promoting energy-saving lamps is actually irresponsible to our children and grandchildren.


2.3 Low life


   Energy-saving lamps are classified according to phosphors: mixed powder, halogen powder, and three primary colors. The life of halogen powder is 3000~4000 hours; the life of mixed powder is 4000~6000 hours; the three primary colors are said to be more than 8000 hours.


  2.4 low quality ballast


   Most of the ballasts used in fluorescent lamps cannot give enough power. For example, the author measured a 32W fluorescent lamp with a ballast whose output power is only 16W, that is, only 50% of the rated power. Moreover, the short life of all fluorescent lamps is mainly due to the short life of the ballast, and once the fluorescent lamp is damaged, the ballast is usually damaged. Almost everyone’s experience is that the ballast or lamp tube is usually replaced once a year, most of the time it is less than a year, and both have to be replaced.


  2.5 The price is not cheap


Generally, ceiling lamps cost tens to hundreds of yuan. Foreign brands cost more than 600 yuan. As for some ceiling lights with crystal ornaments, the price is as high as several thousand yuan. The light source is only But at most it is a 40W special-shaped fluorescent lamp. So ceiling lamps are not as cheap as ordinary energy-saving lamps.


  一. The advantages of LED ceiling lights


  3.1 High luminous efficiency


   The luminous efficiency of the LED itself has reached 130lm/W, so the overall luminous efficiency of the LED ceiling lamp can reach 100lm/W. And this efficiency is still growing every year. It is estimated that by 2020, the luminous efficiency of the LED itself will reach 240lm/W. High light efficiency means energy saving. According to the measured results, an 8W LED can replace a 32W ceiling lamp. Electric power can be saved more than 4 times.


  3.2 Long life


The lifespan of LED is 100,000 hours. After being made into lamps, it is actually recognized that the lifespan is at least 30,000 hours. The high-quality ones can achieve 50,000 hours, which is more than 10 times longer than fluorescent lamps, even the three-primary-color fluorescent lamps with the highest lifespan. The life span is 10,000 hours, which is also more than 5 times higher.


  3.3 Mercury free


  3.4 No ultraviolet radiation, no light pollution


  3.5 It can provide light of various color temperatures as required, usually 2550-3700ºK, and 4700-7000ºK.


  3.6 No glass parts, shock and vibration resistance, easy to transport.


  3.7 No need for aluminum radiator, low cost and light weight


  二. The composition and heat dissipation of LED ceiling lamps


   Regardless of the gorgeous crystal ceiling lights, the structure of ordinary LED ceiling lights is no different from ordinary ceiling lights. They are composed of four parts: bottom shell, outer cover, power supply, and light.


4.1 Lamp beads of LED ceiling light


   Usually, 1W LED lamp beads are used for power larger than 30W, and low-power LED lamp beads (such as 3020, 3014, 3528, etc.) are mostly used for power below 30W. It is recommended to use SMD low-power LEDs to facilitate heat dissipation and improve the uniformity of light emission.


 


  The lamp beads can be arranged according to their shape. For example, if the shape is round, the lamp beads are arranged in a circle. On the contrary, if the shape is square, then they are arranged in a square.


4.2 Shade of LED ceiling lamp


 


  The lampshade usually uses PC board, and its performance is as follows:


 


  (1) Light transmittance: The light transmittance of the PC board can reach up to 89%, which is as beautiful as glass. UV-coated panels will not produce yellowing, atomization and poor light transmission under sunlight. After ten years, the loss of light transmission is only 6%, the loss rate of PVC is as high as 15%-20%, and the glass fiber is 12 %-20%.


 


(2) Impact resistance: The impact strength of PC board is 250-300 times that of ordinary glass, 30 times that of acrylic board of the same thickness, and 2-20 times that of tempered glass. There will be no cracks when it is dropped two meters under a 3kg hammer. The reputation of "unbreakable glass" and "sound steel".


 


   (3) Anti-ultraviolet: One side of the PC board is coated with an anti-ultraviolet (UV) coating, and the other side has an anti-condensation treatment, which integrates anti-ultraviolet, heat insulation and anti-drip functions. It can block ultraviolet rays from passing through, and is suitable for protecting valuable artworks and exhibits from ultraviolet rays.


 


  (4) Light weight: The specific gravity is only half of that of glass, saving the cost of transportation, handling, installation and supporting frame.


 


  (5) Flame-retardant: National standard GB50222-95 confirms that the PC board is flame-retardant grade one, that is, grade B1. The ignition point of the PC board is 580 degrees Celsius, and it will self-extinguish after leaving the fire. It will not produce toxic gas during combustion and will not promote the spread of fire.


 


  (6) Flexibility: According to the design drawing, it can be cold-formed on the construction site and installed into an arch, semi-circular roof and window shape. The minimum bending radius is 175 times the thickness of the adopted plate, and hot bending is also possible.


 


  (7) Temperature adaptability: PC board will not be cold brittle at -100℃, and will not soften at 135℃, and its mechanics and mechanical properties will not change significantly in harsh environments.


 


  (8) Weather resistance: PC board can maintain the stability of various physical indexes in the range of -40℃ to 120℃. After 4000 hours of artificial weathering test, the yellowing degree was 2, and the light transmittance decreased by only 0.6%.


 


  4.3 Heat dissipation of LED ceiling lamp


 


  Using low-power LED lamp beads, arranged and scattered, can help heat dissipation.


 


The structural characteristics of    ceiling lamps are also conducive to heat dissipation.


 


   1. The internal air circulates freely without obstruction. This is the biggest advantage of ceiling lamps compared to other lamps. Airtight but not circulating air is an insulator with good thermal insulation performance. Conversely, air that can circulate freely is the best heat sink. All heat generating objects in the world finally radiate heat into the air. Because the bottom plate of the ceiling lamp has many small holes, in the lampshade of the ceiling lamp, the heat generated by the LED lamp beads can be immediately transferred to the outside through the air.


 


   2. The lampshade can dissipate heat well. We know that convection and radiation heat dissipation are mainly related to area and material, and the effect of plastic radiation heat dissipation is very good, and the thickness of the lampshade is very thin, so the poor thermal conductivity of plastic can be ignored.


Previous:Introduction of epitaxial wafer knowledge for LED Next:Cause analysis of LED dead light