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Comparison of 5 radiators for indoor LED lighting fixtures
author:tom2020 Release time:2020-04-10 09:36:04 Read:11
Atpresent,thebiggesttechnicalproblemofLEDlightingfixturesistheproblemofheatdissipation.PoorheatdissipationhasledtoLEDdrivepowerandelectrolyticcapacitorsbecomingshortcomingsforthefurtherdevelopmentofLE

At present, the biggest technical problem of LED lighting fixtures is the problem of heat dissipation. Poor heat dissipation has led to LED drive power and electrolytic capacitors becoming shortcomings for the further development of LED lighting fixtures. The reason for the premature decline of LED light sources.


In the luminaire scheme using LV LED light source, because the LED light source works in a working state of low voltage (VF = 3.2V) and large current (IF = 300 ~ 700mA), the heat is very strong. It is difficult for the radiator to dissipate heat quickly. Despite the use of multiple heat dissipation solutions, the results were unsatisfactory and became an unsolvable problem for LED lighting fixtures. Looking for simple and easy to use, good thermal conductivity, and low-cost heat dissipation materials are always working hard.


At present, after the LED light source is powered on, about 30% of the electrical energy is converted into light energy, and the rest is converted into heat energy. Therefore, to export so much heat energy as soon as possible is a key technology for the structural design of LED lamps. Heat energy needs to be dissipated through heat conduction, heat convection, and heat radiation. Only by exporting heat as quickly as possible can the temperature of the cavity in the LED lamp be effectively reduced, the power supply can be protected from working in a persistent high-temperature environment, and the premature aging of the LED light source due to long-term high-temperature work can be avoided.


The cooling way of LED lighting


Because the LED light source itself does not have infrared or ultraviolet rays, the LED light source itself does not have a radiation heat dissipation function. The heat dissipation of LED lighting fixtures can only derive heat through a heat sink closely combined with the LED lamp bead plate. The radiator must have the functions of heat conduction, heat convection and heat radiation.


In addition to the ability to quickly transfer heat from the heat source to the surface of the radiator, any radiator must mainly dissipate heat into the air by convection and radiation. Heat conduction only solves the way of heat transfer, and heat convection is the main function of the radiator. The heat dissipation performance is mainly determined by the ability of the heat dissipation area, shape, and natural convection intensity. The heat radiation is only an auxiliary function.


In general, if the distance of heat from the heat source to the surface of the heat sink is less than 5mm, as long as the thermal conductivity of the material is greater than 5, its heat can be exported, and the rest of the heat must be dominated by thermal convection.


Most LED lighting sources still use low-voltage (VF = 3.2V) and high-current (IF = 200-700mA) LED lamp beads. Due to the high heat during operation, aluminum alloys with higher thermal conductivity must be used. There are usually die-cast aluminum radiators, extruded aluminum radiators, and stamped aluminum radiators. Die-casting aluminum radiator is a technology of die-casting parts. The liquid zinc-copper-aluminum alloy is poured into the inlet of the die-casting machine. After die-casting by the die-casting machine, the radiator with the shape limited by the pre-designed mold is cast.


Die-casting aluminum radiator


The production cost is controllable, the heat dissipation wings cannot be made thin, and it is difficult to enlarge the heat dissipation area. The commonly used die casting materials for LED lamp radiators are ADC10 and ADC12.


Extruded aluminum radiator


The liquid aluminum is extruded through a fixed mold, and then the bar is machined and cut into a radiator of the desired shape, and the later processing cost is higher. The heat dissipation wings can be made very thin, and the heat dissipation area is maximized. When the heat dissipation wings are working, air convection is automatically formed to diffuse heat, and the heat dissipation effect is better. Common materials are AL6061 and AL6063.


Stamped aluminum radiator


It is the punching and pulling of steel and aluminum alloy plates by punch and die to make it into a cup-shaped radiator. The inner and outer circumferences of the stamped and formed radiator are smooth, and the heat dissipation area is limited due to the wingless. 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 solution.


The heat conduction of the aluminum alloy radiator is ideal, and it is more suitable for isolated switching constant current power supply. For the non-isolated switch constant current power supply, the structural design of the lamp needs to be well isolated for AC and DC, high-voltage and low-voltage power supply in order to pass the CE or UL certification.


Plastic-coated aluminum radiator


It is a heat sink with heat conductive plastic shell and aluminum core. The thermally conductive plastic and the aluminum heat-dissipating core are formed on the injection molding machine at one time, and the aluminum heat-dissipating core is used as an embedded part, which needs to be processed in advance. The heat of the LED lamp bead is quickly transmitted to the thermally conductive plastic through the aluminum heat dissipation core. The thermally conductive plastic uses its multi-wings to form air convection to dissipate heat, and uses its surface to radiate part of the heat.


Plastic-coated aluminum radiators generally use the original colors of thermally conductive plastics, white and black. Black plastic plastic-coated aluminum radiators have a better radiation cooling effect. Thermally conductive plastic is a kind of thermoplastic material. The fluidity, density, toughness and strength of the material are easy to be injection molded. It has good resistance to cold and hot shock cycles and excellent insulation properties. The radiation coefficient of thermally conductive plastics is superior to ordinary metal materials.


The density of thermally conductive plastic is 40% lower than that of die-cast aluminum and ceramics. The heat sink of the same shape can reduce the weight of plastic clad aluminum by nearly one third; compared with all-aluminum radiators, the processing cost is low, the processing cycle is short, and the processing temperature is low; The finished product is not fragile; the customer's own injection molding machine can be used to design and produce differentiated lamps and lanterns. The 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 radiators have developed rapidly recently. High thermal conductivity plastic radiators are all-plastic radiators whose thermal conductivity is several tens of times higher than ordinary plastics, reaching 2-9w / mk, with excellent heat conduction and heat radiation capabilities ; New insulation and heat dissipation materials that can be applied to various power lamps, and can be widely used in various types of LED lamps from 1W to 200W.


High thermal conductivity plastics can withstand voltage up to 6000V, suitable for non-isolating switch constant current power supply, HVLED high voltage linear constant current power supply. Make this kind of LED lighting fixture easy to pass strict safety regulations such as CE, TUV, UL and so on. HVLED uses high voltage (VF = 35-280VDC), small current (IF = 20-60mA) working state, so the heat of HVLED lamp bead plate is reduced. The high thermal conductivity plastic radiator can be used with traditional injection molding and extrusion machines.


Once formed, the finished product has high finish. Significantly improve the efficiency of production, high flexibility of shape design, can give full play to the designer's design concept. The high thermal conductivity plastic radiator is polymerized by PLA (corn starch), fully degraded, no residue, no chemical pollution, no heavy metal pollution, no sewage, no exhaust gas in the production process, in line with global environmental protection requirements.


Nano-level metal ions are densely packed between PLA molecules inside the high thermal conductivity plastic heat sink, which can move quickly at high temperature and increase the heat radiation energy. Its vitality is better than that of metal heat sink. High thermal conductivity plastic radiator withstands high temperature, does not crack or deform at 150 ℃ for five hours, cooperates with the application of high voltage linear constant current IC driving scheme, does not require electrolytic capacitors and large volume inductance, greatly improves the life of LED whole lamp, non-isolated power scheme, high efficiency ,low cost. It is especially suitable for the application of fluorescent tubes and high-power industrial and mining lamps.


High-conductivity plastic radiators can be designed with many precise cooling fins. The cooling fins can be made very thin, and the heat dissipation area is maximized. When the cooling fins work, they will automatically form air convection to diffuse heat, and the cooling effect is better. The heat of the LED lamp beads is directly passed to the heat dissipation wing through the high thermal conductivity plastic, and is quickly dissipated by air convection and surface radiation.


High thermal conductivity plastic heat sinks are lighter than aluminum. The density of aluminum is 2700kg / m3, and the density of plastic is 1420kg / m3, which is almost half of that of aluminum. So the heat sink of the same shape, the weight of plastic radiator is only 1/2 of that of aluminum. And the processing is simple, and its molding cycle can be shortened by 20-50%, which also reduces the driving force for cost.


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