Design And Optimization Of A New White LED Phosphor Layer Structure

In recent years, the development of white LED the fast. For white LED, unlike other light sources,which radiation patrern is uniform, so the white LED color temperature distribution in the space is not uniform.Human eye can identify the minimum temperature of 80 k of color, in order to reduce to the discomfort caused by the uneven distribution of temperature and improve the quality of white LED, improve the white LED color temperature distribution uniformity is very necessary.This article through the establishment of the white LED light transmission model, the understanding of the impact mechanism of color temperature distribution uniformity, and the study of white LED encapsulation structure system, proposes an improved white LED color temperature distribution uniformity of encapsulation structure, and carries on the optimization design, on the basis of simulation, validated by experiment to proves that this new type of encapsulation structure can effectively improve the space of white LED color temperature distribution uniformity.First of all, establishing a physical model of white LED is important.Physical models include blue leds MQWs(Multiple Quantum Wells) model, the Mie scattering model, the structure of the phosphor powder layer model, boundary model, correlated color temperature calculation model and transmission model of white LED.By conbining those models, using Monte Carlo method simulates the optical properties of white LED.In the basis of light intensity self-adaptiveness encapsulation structure, this paper proposes a new optimal encapsulation structure based on curved surface and light intensity self-adaptiveness.The new optimal encapsulation structure conbines ligt intensity self-adaptiveness with traditional dispensing encapsulation,which is that add the traditional dispensing layer on the light intensity self-adaptive layer.Simulation results show that on the color temperature uniformity, optimal structure is better than self-adaptive structure.After that,this paper simulated various parameters that may affect the performance of new structure, mainly including self-adaptive layer thickness and the concentration of traditional dispensing layer.On the basis of simulation and experiments,this paper found that optimal structure is better than light intensity self-adaptive structure in the color temperature uniformity. When the average temperature is around 5200 k, ACU increased by 7.85% and the luminous efficiency increased by 33.3%.Then comparing optimal structure with light intensity self-adaptive structure layer coated with the silicon, found that the space color temperature uniformity of optimal structure is better.when the CCT is 4900 k, luminous efficiency increased by 12.2%.Then this paper studys the influence of different process and parameters of the optimal structure through the experiment.Through changing the thickness of light intensity self-adaptive layer and the concentration of the traditional dispensing, discussed their effects on optical properties of the optimal structure.This paper found the optimal structure that improved technology and the parameters, using the current at 1A to exposure and concentration of phosphor at 1/9.when average CCT at 5500 k, the space color temperature standard deviation of the optimal structure is 75 k,the luminous efficiency is 92.1lm/W; the space color temperature standard deviation of the light intenstiy self-adaptive structrue is 195 k luminous efficiency is 68.5lm/w;the space color temperature standard deviation of the light intensity self-adaptive structure layer coated with the silicon structure is 135 k, luminous efficiency is 83.9lm/W.The space color temperature standard deviation decreased by 61.5% and 61.5% respectively, and luminous efficiency increased by 34.4% and 9.7%, respectively. The color temperature uniformity and the luminous efficiency of the optimal structure improved.At the same time,the optimal structure is easily realised.Using the theory of edge light and energy conservation, this paper designs a new encapsulation structure based on free curved surface lens.Simulation by Monte Carlo Method found when CCT is 5200 k, ACU(Angular Color Uniformity) is larger than 0.98, the biggest difference of Color temperature is 107 k.