Study On Lighting And Thermal Properties Of Flexible Spiral LED Filament Bulb

With the global prohibition of incandescent lamp issued,incandescent lamp with high power consumption and low luminous efficiency is gradually withdraw from people's Daily lighting.However,the flexible spiral LED filament bulb with high efficiency,energy saving and environmental protection is popular among the public because of their 360° all-around light emission.In this paper,the heat dissipation characteristics,the spatial distribution of light intensity and the coupling relationship between light and heat of LED filament bulbs are deeply explored,which provides some practical reference value for the photothermal design of LED filament.Due to the unique shape of flexible spiral LED filament bulb and the lack of effective radiator,the heat generated by LED chip can't be released into the environment in time,which seriously affects the performance of LED bulbs.Therefore,it is crucial to reduce the junction temperature of LED filament bulb by thermal management analysis.For lighting lamps,the uniformity of light intensity spatial distribution is also the most important link.The flexible spiral LED filament is arranged along the axis of the spiral array,but the structure and chip characteristics of the flexible spiral LED filament lead to the inhomogeneity of the spatial distribution of light intensity in the LED filament.In view of the above pain points,it is urgent to explore the flexible spiral LED filament bulb with low junction temperature and uniform spatial distribution of light intensity.In this paper,the relationship between the location of LED filament and junction temperature was studied firstly.Meanwhile,based on finite element analysis,the temperature distributions and internal gas flow path of LED filament were numerically simulated to explore how to reduce the junction temperature of LED filament by improving convection heat dissipation ability through self-circulation effect.The experimental results show that when the axial direction of the flexible spiral filament is consistent with the buoyancy direction,an effective circulating convection can be formed inside the bubble shell to greatly improve the heat dissipation performance,and the higher the tensile height of the filament,the lower the junction temperature.Secondly,the relationship between the number of turns and the inclination angle of the luminous surface and the spatial distribution uniformity of light intensity and the temperature distribution of the filament surface is further explored by using remote optical equipment and infrared thermal imager.The experimental results show that the temperature at both ends of the filament is lower than the middle temperature.As the number of filaments turns increases,the filament surface temperature decreases.It is found that the filament with inclined angle solves the shortcoming of "black under the lamp" and makes the lighting effect greatly improved.The larger the tilt angle,the lower the temperature of the LED filament.Compared with the filament without the tilt Angle,the light distribution curve is smoother and the spatial distribution of light intensity is more uniform.Finally,the existing experiments are carried out at room temperature,from a practical perspective,the injection current and environmental temperature on the flexible spiral LED filament bulb and the influence of electricity,thermal parameters were explored.In this paper,a set of integrated lights-thermo-electric test system for LED filament bulb integrated was built independently to measure and estimate the electrical,optical and thermal properties of LED bulbs as a function of injection current and environmental temperature,aims to determine the best operating conditions of the LED devices and systems.The basic principle of LED filament bulb lighting and thermal coupling was explored through experiments,which provides important reference value for the optimization and design of the flexible spiral LED filament bulb.