Design of high brightness bulb based on plastic radiator

Generally, bulbs use aluminum heat sinks . The disadvantage of this type of bulb is that it is heavy. Moreover, because aluminum is conductive, it is not easy to pass CE, UL and other safety certifications if it is powered by a non-isolated constant current power supply. Because these certifications require a high voltage of more than 4000V, and this voltage is completely applied to a very thin layer of insulating cloth on the aluminum substrate. Usually, the withstand voltage of the aluminum substrate rarely exceeds 3000V, which becomes a bottleneck for passing the certification. The withstand voltage of the insulating plastic heat sink can easily exceed 4000V. This makes it easy for bulbs with plastic heat sinks to pass these safety certifications when using a non-isolated constant current power supply at the same time.

Most people think that metal heat sinks must be used for good heat dissipation. This concept is incorrect. Although metals do conduct heat better than plastics, the main purpose of the shell heat sink is to dissipate heat into the air. When the thickness of the heat sink is less than 5mm, heat conduction is not a major problem. As long as the thermal conductivity of the heat sink material is greater than 5W/mK, the heat dissipation is mainly based on convection (see Figure 1), and there is no difference between metal and plastic. Some good thermally conductive plastics mixed with ceramic powder can easily achieve a thermal conductivity greater than 5W/mK.

Figure 1. The heat dissipation capacity of a heat sink with a thermal conductivity greater than 5W/mK and a thickness less than 5mm is entirely determined by convection.

What's more, plastic is better than aluminum in terms of radiative heat dissipation. Therefore, it is a good choice to use plastic radiators for bulbs.

The bulb developed by Longmao Company (www.long-mao.com.cn) has an input power of 8W and an efficiency of more than 88%. Actual tests show that its heat dissipation effect is satisfactory. Moreover, its weight is about 30% lighter than that of ordinary bulbs with aluminum heat sinks. Currently, this product is being put into mass production.