Comparative analysis of five types of radiators for LED lighting fixtures

At present, the major technical problem of LED lighting lamps is the problem of heat dissipation. Poor heat dissipation has LED to the short board of LED driving power supply and electrolytic capacitor for the further development of LED lighting lamps. The reason for the premature aging of LED light sources. In the lamp scheme using LVLED light source, because the LED light source works at low voltage (VF = 3. 2 V), Large current (IF = 300-700mA) The working state of the radiator is very hot, the space of traditional lamps is small, and it is difficult for small-area radiators to export heat quickly. Although a variety of heat dissipation schemes have been adopted, the results are not satisfactory and have become an unsolved problem for LED lighting lamps. 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 electric energy is converted into light energy, and the rest is converted into heat energy. Therefore, it is the key technology for the structural design of LED lamps to export so much heat energy as soon as possible, heat energy needs to be dissipated through heat conduction, heat convection, and heat radiation. Only by exporting heat as soon as possible can the cavity temperature in LED lamps be effectively reduced, the power supply can be protected from working in a long-lasting high-temperature environment, and premature aging of LED light sources can be avoided due to long-term high-temperature work. The heat dissipation way of LED lighting lamps is precisely because the LED light source itself has no infrared and ultraviolet rays, so the LED light source itself has no radiation heat dissipation function, the heat dissipation way of LED lighting lamps can only derive heat through the heat sink closely combined with the LED lamp bead board. The radiator must have the functions of heat conduction, heat convection and heat radiation. Any radiator, in addition to being able to quickly conduct heat from the heat source to the surface of the radiator, mainly depends on convection and radiation to dissipate heat into the air. Heat conduction only solves the way of heat transfer, while heat convection is the main function of the radiator. The heat dissipation performance is mainly determined by the heat dissipation area, shape and natural convection intensity. Heat radiation is only an auxiliary function. Generally speaking, if the distance between the heat source and the surface of the radiator is less than 5mm, then as long as the thermal conductivity of the material is greater than 5, the heat can be derived, and the rest of the heat dissipation must be dominated by heat convection. Most LED lighting sources still use low voltage (VF = 3. 2 V), Large current (IF = 200-700mA) The LED lamp bead must use aluminum alloy with high thermal conductivity due to its high heat consumption during operation. There are usually die-cast aluminum radiators, extruded aluminum radiators, and stamped aluminum radiators. Die-cast aluminum radiator is a technology of pressure casting parts. Liquid zinc-copper-aluminum alloy is poured into the feed inlet of the die casting machine. After die casting by the die casting machine, the shape radiator of the die is designed first. Die-cast aluminum radiator, the production cost is controllable, the heat dissipation wing 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. Extrusion of aluminum radiator is to extrude liquid aluminum into a fixed mold, and then cut the bar into a radiator with the required shape through machining, thus the later processing cost is relatively high. The extruded aluminum radiator is shown in Fig. 3. The heat dissipation wing can be made a lot of very thin, and the heat dissipation area is greatly expanded. When the heat dissipation wing works, air convection diffuses heat automatically, and the heat dissipation effect is better. Common materials are AL6061 and al6063. Stamping aluminum radiator is to punch and pull up steel and aluminum alloy plates through punching machines and dies, so as to make it a cup-shaped radiator, and the inside and outside of the punched radiator are smooth, the heat dissipation area is limited due to no wings. Commonly used aluminum alloy materials are 5052, 6061 and 6063. Stamping parts have small quality and high material utilization rate, 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 non-isolated switch constant current power supply, it is necessary to isolate AC and DC, high voltage and low voltage power supply through the structural design of lamps before passing CE or UL certification. The plastic-coated aluminum radiator is a heat-conducting plastic shell aluminum core radiator. The thermal conductive plastic and the aluminum heat dissipation core are molded once in the injection molding machine, and the aluminum heat dissipation core is used as an embedded part, which needs to be machined in advance. The heat of the LED lamp bead is quickly conducted to the heat-conducting plastic through the aluminum heat-dissipating core. The heat-conducting plastic uses its multi-wings to form air convection heat dissipation, and uses its surface to radiate part of the heat. Plastic-coated aluminum radiators generally use the original colors of heat-conducting plastic white and black, while black plastic plastic-coated aluminum radiators have better radiation heat dissipation effect. Thermal conductive plastic is a thermoplastic material. Its fluidity, density, toughness and strength are easy to be injection molded. It has good cold and hot impact cycle resistance and excellent insulation performance. The radiation coefficient of thermal conductive plastic is better than that of common metal materials. The density of thermal conductive plastic is 40 less than that of die-cast aluminum and ceramics. For radiators of the same shape, the weight of plastic-coated aluminum can be reduced by nearly 1/3; 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; Customers bring their own injection molding machines to design and produce differentiated appearance of lamps. The plastic-coated aluminum radiator has good insulation performance and is easy to pass the safety regulations.