At present, one of the biggest technical problems of LE […]
At present, one of the biggest technical problems of LED lighting is heat dissipation. Poor heat dissipation leads to LED driving power supply and electrolytic capacitor becoming the short board of further development of LED lighting lamps, and the cause of premature aging of LED light source.
Only by exporting heat as soon as possible can the cavity temperature of LED lamps be effectively reduced, the power supply can not work in a long-term high-temperature environment, and the premature aging of LED light source due to long-term high-temperature work can be avoided.
It is precisely because the LED light source itself has no infrared and ultraviolet rays, so the LED light source itself has no radiation and heat dissipation function. The heat dissipation way of LED lighting lamps can only be derived from the heat sink which is closely combined with LED lamp bead plate. The radiator must have the function of heat conduction, heat convection and heat radiation.
Any radiator, in addition to being able to quickly transfer heat from the heat source to the surface of the radiator, the most important thing is to dissipate the heat to the air by convection and radiation. Heat conduction only solves the way of heat transfer, and heat convection is the main function of radiator. The heat dissipation performance is mainly determined by the heat dissipation area, shape and natural convection strength, while thermal radiation is only an auxiliary function. Generally speaking, if the distance between the heat source and the radiator surface is less than 5mm, the heat can be derived as long as the thermal conductivity of the material is greater than 5, and the remaining heat dissipation must be dominated by thermal convection.
Most LED lighting sources still use LED beads with low voltage (VF = 3.2V) and high current (if = 200-700ma). Due to high heat during operation, aluminum alloy with high thermal conductivity must be used. There are usually die-casting aluminum radiator, extrusion aluminum radiator, stamping aluminum radiator. Die casting aluminum radiator is a kind of pressure casting technology. The liquid zinc copper aluminum alloy is poured into the feed port of the die casting machine. After the die casting machine is die cast, the radiator with the shape defined by the designed mold is cast.
The following is a comparative analysis of five types of radiators.
Die casting aluminum radiator
The production cost is controllable, and the cooling wing cannot be made thin, so it is difficult to maximize the heat dissipation area. Adc10 and ADC12 are commonly used as die-casting materials for LED lamp radiator.
Extruded aluminum radiator
Liquid aluminum is extruded through a fixed die, and then the bar is machined and cut into the required shape of the radiator. The later processing cost is higher. The extruded aluminum radiator is shown in Figure 3. The cooling wing can be made a lot of very thin, and the heat dissipation area can be expanded to the largest extent. When the heat dissipation wing works, the air convection diffusion heat will be formed automatically, and the heat dissipation effect is good. The commonly used materials are Al6061 and al6063.
Stamping aluminum radiator
It is to punch and pull up the steel and aluminum alloy plates by punch and die, so as to make them into cup and barrel type radiator. The inner and outer periphery of the radiator formed by stamping is smooth, and the heat dissipation area is limited due to no wings. The commonly used aluminum alloy materials are 5052, 6061 and 6063. The quality of stamping parts is very small and the material utilization rate is high, which is a low cost scheme.
The heat conduction of aluminum alloy radiator is ideal and suitable for isolated switching constant current power supply. For the non isolated switch constant current power supply, it is necessary to do a good job in the isolation of AC and DC, high voltage and low voltage power supply through the structural design of lamps, so as to pass CE or UL certification.
Plastic cladding aluminum radiator
It is a kind of heat conduction plastic shell aluminum core radiator. The thermal conductive plastic and the aluminum heat dissipation core are molded in the injection molding machine at one time. The aluminum heat dissipation core is an embedded part, which needs to be machined in advance. The heat of LED lamp bead is quickly transferred to thermal conductive plastic through aluminum heat dissipation core. Thermal conductive plastic uses its multi wings to form air convection heat dissipation, and uses its surface to radiate part of the heat.
Plastic coated aluminum radiator generally uses the original color of thermal conductive plastic white and black, and the radiation heat dissipation effect of plastic clad aluminum radiator with black plastic is better. Thermal conductive plastic is a kind of thermoplastic material. The fluidity, density, toughness and strength of the material are easy to be molded by injection molding. It has good thermal shock resistance and excellent insulation performance. The radiation coefficient of thermal conductive plastics is better than that of common metal materials. The density of thermal conductive plastic is 40% less than that of die-casting aluminum and ceramics, and the weight of plastic coated aluminum can be reduced by nearly one third for the same shape radiator; compared with all aluminum radiator, the processing cost is low, the processing cycle is short, and the processing temperature is low; the finished product is not fragile; the injection molding machine provided by the customer can design and produce the lamp with different shapes. Plastic coated aluminum radiator has good insulation performance and is easy to pass the safety regulations.
High thermal conductivity plastic radiator
High thermal conductivity plastic radiator is a kind of all plastic radiator. Its thermal conductivity is dozens of times higher than that of ordinary plastics, up to 2-9w / MK, which has excellent heat conduction and radiation capacity. It can be used in various power lamps and lanterns, and can be widely used in all kinds of LED lamps from 1W to 200W.
The withstand voltage grade of high thermal conductive plastic can reach 6000V AC, which is suitable for non isolated switch constant current power supply and high voltage linear constant current power supply of hvled. This kind of LED lighting lamp is easy to pass the CE, TUV, UL and other strict safety inspection. High voltage (VF = 35-280vdc) and low current (if = 20-60ma) are adopted for hvled, so the heat of hvled lamp bead plate is reduced. Traditional injection molding and extrusion machines can be used for high thermal conductivity plastic radiator. Once molding, the finished product has high finish. Greatly improve the efficiency of production, high flexibility of modeling design, can give full play to the designer's design concept. High thermal conductivity plastic radiator is polymerized with PLA (corn starch), which is completely degraded, no residue, no chemical pollution, no heavy metal pollution, no sewage and no exhaust gas in the production process, which meets the requirements of global environmental protection.
The PLA molecules of high thermal conductivity plastic radiator are densely packed with nano metal ions, which can move rapidly at high temperature and increase the thermal radiation energy. Its activity is better than that of metal radiator. High thermal conductivity plastic radiator is resistant to high temperature, does not crack and deform at 150 ℃ for five hours. With the application of high voltage linear constant current IC driving scheme, it does not need electrolytic capacitor and large volume inductance, and greatly improves the life of LED whole lamp. The non isolated power supply scheme has high efficiency and low cost. It is especially suitable for the application of fluorescent lamp and high-power mining lamp.
High thermal conductivity plastic radiator can be designed with many precision fins. The fins can be made into many thin ones, and the heat dissipation area can be expanded to the largest extent. When the heat dissipation wing works, the air convection will be formed automatically to diffuse heat, and the heat dissipation effect is good. The heat of LED lamp bead is directly transferred to the heat dissipation wing through high thermal conductivity plastic, which can quickly dissipate heat through air convection and surface radiation.
The density of high thermal conductive plastic radiator is lighter than that of aluminum. The density of aluminum is 2700kg / m3, while the density of plastic is 1420kg / m3, which is almost half of that of aluminum. Therefore, the weight of plastic radiator with the same shape is only half of that of aluminum. Moreover, the processing is simple, and the molding cycle can be shortened by 20-50%, which reduces the power of cost.