2012 will be a year of full and large-scale LED entry into the home. The E26 type incandescent lamp is mainly used in American households. However, in urban households in China, few people still use incandescent lamps, and most of them use ceiling lamps with curved fluorescent tubes. How to produce low-cost, good-performance LED ceiling lamps will be a great challenge for LED practitioners. In order to do this alternative work, we must first have a full understanding of ordinary ceiling lamps in order to be able to know ourselves and know each other.
Ordinary ceiling light
1.1 The shape of the ceiling lamp
Although there are many types of ordinary ceiling lamps (Fig. 1), the most common ones are round or square, and the more complex ones have various odd-shaped crystal ceiling lamps:
Figure 1. Ceiling lights of various shapes
1.2 ceiling lamp tube
Most of its lamps are T5 fluorescent lamps after bending (Fig. 2). There are many kinds of specifications, mainly the following.
Figure 2. Fluorescent lamp for ceiling lamps
1.3 The power of the ceiling lamp is not clearly defined.
The most commonly used powers are 10W, 16W, 21W, 28W, 32W, 38W, 40W and so on.
Common ceiling lamps' problems and shortcomings
2.1 Low luminous efficiency
The overall lighting efficiency with ballast energy-saving lamps is only 55lm/W, and the highest high-power U-shape is only 80lm/W. And because most of these ceiling lamps are mostly T5-type lamps, they are bent into various shapes. But no matter what shape it is finally bent into, it is 360-degree light, and the upward 180 degrees of light must be reflected back to become useful light, and this reflection process will lose a lot of light. Therefore, at least 70% discount will be applied to the light effect after the lamp is made. That is to say, the above light effect is multiplied by 0.7. Moreover, in actual use, its brightness decays rapidly with time. For example, a Philips 32W ring T5 tricolor lamp YH32RR16 has a color temperature of 6500oK, a luminous efficiency of 67lm/W, and a total lumen of 2150lm. In fact, only 70% of the light can be used. That is only 1500lm.
2.2 Containing mercury
Mercury has a very low boiling point and can evaporate at normal temperatures. After a waste discarded fluorescent lamp is broken, it immediately emits mercury vapor to the surrounding area, which instantly makes the concentration of mercury in the surrounding air reach 10-20 mg/m3, exceeding the maximum allowable concentration of mercury in the air (0.01 mg/cubic). 1000 to 2000 times the amount of rice, the human body inhaled 2.5 grams of mercury vapor is life-threatening. Moreover, the liquid mercury has a very high permeability and will immediately penetrate into the underground polluted groundwater when it falls to the ground. 1 milligram of mercury is enough to contaminate 5454.5 kilograms of drinking water, making it impossible to meet safe drinking standards. Nowadays, the promotion of energy-saving lamps is actually an irresponsible approach 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 the halogen powder is 3000-4000 hours; the life of the mixed powder is 4000-6000 hours; the three primary colors are more than 8000 hours.
2.4 ballast quality is low
Most of the ballasts used in fluorescent lamps do not give enough power. For example, the authors measured the ballast used in a 32W fluorescent lamp with an output of only 16W, which is only 50% of the rated power. Moreover, the life of all fluorescent lamps is short, mainly because the life of the ballast is very short, and once the fluorescent lamp is damaged, the ballast is usually followed. Almost everyone's experience is that the ballast or lamp should be replaced once a year. Most of the time it is less than a year, and both must be changed.
2.5 The price is not cheap
The price of general ceiling lamps ranges from tens to hundreds of dollars. The ceiling lamps of foreign brands should cost more than 600 yuan. As for some ceiling lamps with crystal ornaments, the price is as high as several thousand yuan, and the light source is only But at most it is a 40W shaped fluorescent lamp. Therefore, ceiling lamps are not as cheap as ordinary energy-saving lamps.
Advantages of LED ceiling lamps
3.1 High luminous efficiency
The luminous efficiency of the LED itself has reached more than 130lm/W, so the overall efficacy 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 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. The electric power can be saved by more than 4 times.
3.2 Long life
The life of the LED is 100,000 hours. After the lamp is made, the life is actually recognized as at least 30,000 hours. The high quality can be 50,000 hours. It is 10 times longer than the fluorescent lamp, even the highest life three-color fluorescent lamp. The life expectancy is 10,000 hours, and it is also more than 5 times higher.
3.3 Mercury free
3.4 No UV radiation, no light pollution
3.5 Various color temperature lights can be provided as needed, usually 2550-3700oK, and 4700-7000oK.
3.6 No glass parts, shock and vibration resistant, easy to transport.
3.7 No need for aluminum radiators, low cost and light weight.
Fourth, the composition of LED ceiling lamps and heat dissipation
Regardless of the gorgeous crystal ceiling lamp, the structure of a common LED ceiling lamp is no different from that of a normal ceiling lamp. They are composed of four parts: the bottom case, the cover, the power supply, and the lamp.
4.1 LED ceiling lamp lamp beads
Generally, 1W LED lamp beads are used for powers greater than 30W, and low-power LED lamp beads (for example, 3020, 3014, 3528, etc.) are mostly used below 30W. SMD-type low-power LEDs are recommended for heat dissipation and uniformity of illumination.
The beads can be arranged according to their shape. For example, if the shape is circular, the beads are arranged in a circle, and if the shape is square, they are arranged in a square shape. Even so, there are many ways to arrange the lamp bead. The internal structure of a typical LED ceiling lamp is shown in Figure 3.
Figure 3. Internal structure of the LED
In the figure, there are two LED lamp beads on the circular printed board. It uses 23 0.4W type 5730 LED lamp beads with a total power of 18W. The middle rectangle is its constant current power supply, and the lower right corner of the box is the photodiode of the remote receiver to receive the infrared control signal of the remote brightness.
What needs to be mentioned is that there are still a large number of low-cost LED ceiling lamps that use low-power straw hat lamps. However, due to the large thermal resistance of the straw hat lamps (450 °C/W), it is difficult to derive heat, resulting in severe light decay and short life. .
4.2 LED ceiling lamp cover
The lampshade usually uses a PC board and its performance is as follows:
(1) Transmittance: The transmittance of PC board is up to 89%, which is comparable to glass. UV-coated panels do not produce yellowing under sunlight, and fogging, poor light transmission, after 10 years, the loss of light transmission is only 6%, the rate of PVC loss is as high as 15%-20%, and the fiberglass is 12 %-20%.
(2) Anti-impact: The impact strength of PC board is 250-300 times that of ordinary glass, 30 times of acrylic sheet of the same thickness, 2-20 times of tempered glass, and there is no crack when it is dropped by 2 meters below 3kg hammer. The name of “not broken glass†and “ring steelâ€.
(3) UV protection: The PC board is coated with anti-ultraviolet (UV) coating on one side and anti-condensation treatment on the other side, which combines anti-UV, heat insulation and anti-drip function. It blocks UV rays and protects valuable artwork and exhibits from UV damage.
(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: The national standard GB50222-95 confirms that the PC board is a non-flammable first grade, namely B1 grade. PC board's own ignition point is 580 degrees Celsius, self-extinguishing from the fire, no toxic gas will be produced when burning, it will not promote the spread of fire.
(6) Flexibility: It can be installed in an arched shape, semi-circular top and window shape according to the design drawing. The minimum bending radius is 175 times the thickness of the plate, and it can also be bent.
(7) Temperature adaptability: PC plate does not appear cold and brittle at -100 °C, does not soften at 135 °C, and its mechanical and mechanical properties do not change significantly in harsh environments.
(8) Weather resistance: The PC board can maintain the stability of various physical indexes in the range of -40 ° C to 120 ° C. The artificial climate aging test was 4000 hours, the yellowing degree was 2, and the light transmittance reduction value was only 0.6%.
4.3 Cooling of LED ceiling lamps
Using low-power LED lamp beads, the arrangement is scattered to help dissipate heat. The structural characteristics of the ceiling lamp are also conducive to heat dissipation.
1. The internal air is free to flow without blocking. This is the biggest advantage of ceiling lamps compared to other lamps. The air that is sealed and not circulated is a kind of insulation with good heat insulation performance. In turn, the air that can flow freely is the best heat sink. All the hot objects in the world finally emit 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 bead can be immediately transmitted to the outside through the air.
2. The lamp cover can dissipate heat very well. We know that convection and radiation heat dissipation are mainly related to area and material, while the radiation heat dissipation effect of plastic is very good, and the thickness of the lamp cover is very thin, so the influence of poor heat conduction of plastic can be neglected. This can be illustrated from Figure 4.
Figure 4 thinner thickness reduces the effect of thermal conductivity
The thickness of the bulb of the ceiling lamp is only 1-2 mm. So although its thermal conductivity is only 0.1-1W/mk, it can quickly transfer heat from one side to the other.
Led Tube light
LED tube is commonly known as light tube, daylight tube, its light source using LED as the luminous body. Led tube has many advantages, using led as the light source, light efficiency is higher, more energy saving, longer service life, and more environmental protection. It is generally used for general lighting, office buildings, shopping malls, restaurants, schools, homes, factories and other Indoor Lighting. LED tube can save more than 70% electricity, and its life is more than 10 times that of ordinary light (in theory, it can reach more than 50,000 hours). It does not need to be replaced frequently. At the same time, LED tube has soft light, pure color, which is beneficial to people's vision protection and health.
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