At present, the biggest technical problem of LED lighting is heat dissipation. Poor heat dissipation has led to LED driving power supply and electrolytic capacitor becoming the short board for further development of LED lighting, and the reason for premature aging of LED light source.

In the lighting scheme using LV LED light sources, due to the LED light source operating at low voltage (VF=3.2V) and high current (IF=300-700mA), the heat generation is severe. Traditional lighting fixtures have limited space, and small heat sinks are difficult to quickly export heat. Despite adopting various cooling schemes, the results were not satisfactory, becoming an unsolvable problem for LED lighting fixtures. We are always striving to find low-cost heat dissipation materials that are easy to use, with good thermal conductivity.

At present, about 30% of the electrical energy of LED light sources is converted into light energy after being powered on, while the rest is converted into thermal energy. Therefore, exporting so much thermal energy as soon as possible is a key technology in the structural design of LED lighting fixtures. Thermal energy needs to be dissipated through thermal conduction, convection, and radiation. Only by exporting the heat as soon as possible can the temperature of the cavity inside the LED lamp be effectively reduced, the power supply be protected from working in a long-lasting high-temperature environment, and the premature aging of the LED light source caused by long-term high-temperature operation be avoided.

Heat dissipation methods for LED lighting fixtures

Because LED light sources do not have infrared or ultraviolet radiation, they do not have radiative heat dissipation function. The heat dissipation pathway of LED lighting fixtures can only be derived through heat sinks closely combined with LED bead plates. The radiator must have the functions 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, mainly relies on convection and radiation to dissipate heat into the air. Heat conduction only solves the path of heat transfer, while thermal convection is the main function of a radiator. The heat dissipation performance is mainly determined by the heat dissipation area, shape, and natural convection intensity, while thermal radiation is only an auxiliary function.

Generally speaking, if the distance from the heat source to the surface of the radiator is less than 5mm, as long as the material’s thermal conductivity is greater than 5, its heat can be exported, and the remaining heat dissipation must be dominated by thermal convection.

Most LED lighting sources still use low voltage (VF=3.2V) and high current (IF=200-700mA) LED beads. Due to the high heat during operation, aluminum alloys with high thermal conductivity must be used. Usually there are die-cast aluminum radiators, extruded aluminum radiators, and stamped aluminum radiators. Die cast aluminum radiator is a technology for pressure casting parts, which involves pouring liquid zinc copper aluminum alloy into the feed port of the die casting machine, and then casting it into a pre designed mold with a predetermined shape.

Die cast aluminum radiator 

The production cost is controllable, and the heat dissipation wing cannot be made thin, making it difficult to maximize 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 into shape through a fixed mold, and then the bar is machined and cut into the desired shape of the heat sink, resulting in higher processing costs in the later stage. The heat dissipation wing can be made very thin, with the maximum expansion of the heat dissipation area. When the heat dissipation wing works, it automatically forms air convection to diffuse heat, and the heat dissipation effect is good. The commonly used materials are AL6061 and AL6063.

Stamped aluminum radiator 

It is the process of stamping and lifting steel and aluminum alloy plates through a punch and mold to create a cup shaped radiator. The stamped radiator has a smooth inner and outer circumference, and the heat dissipation area is limited due to the lack of wings. The commonly used aluminum alloy materials are 5052, 6061, and 6063. Stamped parts have low quality and high material utilization, making them a low-cost solution.

The thermal conductivity of aluminum alloy radiators is ideal and suitable for isolated switch constant current power supplies. For non isolating switch constant current power supplies, it is necessary to isolate AC and DC, high-voltage and low-voltage power supplies through the structural design of the lighting fixtures in order to pass CE or UL certification.

Plastic coated aluminum radiator

It is a heat sink with a thermal conductive plastic shell and an aluminum core. The thermal conductive plastic and aluminum heat dissipation core are formed in one go on an injection molding machine, and the aluminum heat dissipation core is used as an embedded part that requires pre mechanical processing. The heat of LED lamp beads is quickly transferred to thermal conductive plastic through the aluminum heat dissipation core. Thermal conductive plastic uses its multiple wings to form air convection heat dissipation, and uses its surface to radiate some of the heat.

Plastic coated aluminum radiators generally use the original colors of thermal conductive plastic, white and black. Black plastic plastic plastic coated aluminum radiators have a better radiation and heat dissipation effect. Thermal 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 performance. The radiation coefficient of thermal conductive plastic is superior to that of ordinary metal materials

The density of thermal conductive plastic is 40% lower than that of die-cast aluminum and ceramics, and for radiators of the same shape, the weight of plastic coated aluminum can be reduced 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 for differentiated appearance design and production of lighting fixtures. The plastic coated aluminum radiator has good insulation performance and is easy to pass 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, with a thermal conductivity several tens of times higher than ordinary plastics, reaching 2-9w/mk, and excellent heat conduction and radiation capabilities; A new type of insulation and heat dissipation material that can be applied to various power lamps, and can be widely used in various LED lamps ranging from 1W to 200W.

The high thermal conductivity plastic can withstand voltage up to 6000V AC, making it suitable for using non isolating switch constant current power supplies and high-voltage linear constant current power supplies with HVLED. Make this type of LED lighting fixture easy to pass strict safety regulations such as CE, TUV, UL, etc. HVLED operates at high voltage (VF=35-280VDC) and low current (IF=20-60mA), which reduces the heating of the HVLED bead plate. High thermal conductivity plastic radiators can be used with traditional injection molding and extrusion machines.

Once formed, the finished product has high smoothness. Significantly improving productivity, with high flexibility in styling design, it can fully leverage the designer’s design philosophy. The high thermal conductivity plastic radiator is made of PLA (corn starch) polymerization, fully degradable, residue free, and chemical pollution-free. The production process has no heavy metal pollution, no sewage, and no exhaust gas, meeting global environmental requirements.

The PLA molecules inside the high thermal conductivity plastic heat dissipation body are densely packed with nanoscale metal ions, which can quickly move at high temperatures and increase the thermal radiation energy. Its vitality is superior to that of metal material heat dissipation bodies. The high thermal conductivity plastic radiator is resistant to high temperature, and does not break or deform for five hours at 150 ℃. With the application of the high-voltage linear constant current IC drive scheme, it does not need electrolytic capacitor and large inductance, greatly improving the life of the entire LED lamp. The non isolated power supply scheme has high efficiency and low cost. Especially suitable for the application of fluorescent tubes and high-power industrial and mining lamps.

High thermal conductivity plastic radiators can be designed with many precision heat dissipation fins, which can be made very thin and have the maximum expansion of heat dissipation area. When the heat dissipation fins work, they automatically form air convection to diffuse heat, resulting in good heat dissipation effect. The heat of LED lamp beads is directly transferred to the heat dissipation wing through high thermal conductivity plastic, and quickly dissipated through air convection and surface radiation.

High thermal conductivity plastic radiators have a lighter density than aluminum. The density of aluminum is 2700kg/m3, while the density of plastic is 1420kg/m3, which is about half that of aluminum. Therefore, for radiators of the same shape, the weight of plastic radiators is only 1/2 that of aluminum. Moreover, the processing is simple, and its forming cycle can be shortened by 20-50%, which also reduces the driving force of costs.