Research On The Thermal Properties Of Flexible LED Filament Bulb

As the fourth generation of new lighting source,LED lighting has a series of advantages,such as high light efficiency,energy saving,environmental protection,high reliability,and gradually replaced the traditional lighting source to become the mainstream of the lighting market.LED flexible filament lamp is produced under this background.In this paper,the thermal properties of Archimedes spiral LED filament bulb and concentric circular LED filament were studied,which has a certain practical significance for the heat dissipation design of LED filament.In practical applications,heat dissipation has an important impact on the light decay,junction temperature,light efficiency and aging life of LED filaments.Based on the principle of conservation of energy,the energy input from LED filament is converted into light energy and heat energy.Therefore,the heat transfer part needs to be reduced as far as possible.The thermal management of LED filament package is particularly important.A new type of flexible spiral LED filament is introduced in this paper.The optimum drawing height of the filament is studied.At the same time,the flow of gas in the LED bulb with the filament is simulated by the finite element FLOEFD thermal simulation software.The temperature distribution in the actual bulb shell is explored by infrared thermal image.The junction temperature of the filament was investigated by using the junction temperature tester.The experimental results show that the stretched flexible filament can increase the gas pressure difference between the top and bottom of the filament and form a chimney effect inside the bulb shell.Based on the chimney effect principle,the gas circulation efficiency in the bulb shell can be greatly improved,the symmetry of temperature distribution can be significantly enhanced,and the junction temperature of LED filament can be significantly reduced.At the same time,in view of the advantages of Archimedes spiral flexible LED filament in heat dissipation,this paper further proposes a concentric circular spiral flexible LED filament.The pitch and radius of this kind of filament can be adjusted,and the shape of the filament can meet the requirements of different bulb shells,and the luminous performance is more uniform.Based on the geometric principle of helix,the relationship between the initial deployment angle and junction temperature of the concentric spiral filament was investigated by using FLOEFD thermal simulation software and thermal imager.The results show that the larger the initial expansion angle is,the lower the filament junction temperature is,and the higher the pitch is,the lower the filament junction temperature is.The experimental results are consistent with the simulation results.The conclusion is of great practical significance for the thermal design of filament.Finally,from the perspective of heat transfer,the thermal resistance models of flexible filaments and bulbs are analyzed,and the effects of radiation,conduction and convection on bulbs are qualitatively analyzed.For thermal designers of bulb lamps,the basic theoretical knowledge of heat transfer is improved,which fills the gap of heat conduction of bulb lamps,and has important reference significance for thermal designers.