远程荧光粉形状对LED发光性能的影响

Impact of Remote Phosphor Shape on LED Luminous Performance

研究了不同驱动电流和光强分布条件下,圆顶形、椭球形以及圆锥形远程荧光粉的发光性能。实验采用蓝光LED激发YAG:Ce3+荧光粉产生白光,并通过恒流源和TEC控温热沉分别控制LED驱动电流和热沉温度,通过对三种不同形状远程封装的荧光粉的光、色指数等进行对比,发现椭球状样品的综合光学特性最佳,光通量最高。同时,三种远程荧光粉分别进行了不同电流下的Yellow-blue Ratio(YBR)空间分布测试,结果显示,圆顶形样品的YBR空间分布均匀性最好,且在不同电流下ACCTD及ACU值在三种样品中最优。相比大角度,三种样品在0°附近测量的YBR的值都有不同程度的下降,原因是芯片法线方向的荧光粉离光源较远,且光通过荧光粉的光程较短,因此激发效果与大角度出光时有差别。光源的封装形状以及荧光粉形状都成为影响光分布的重要因素,因此通过改变远程荧光粉的封装方式,优化出射光线路径,可以起到改善远程荧光粉发光性能的重要作用,对完善大功率白光LED光学特性的研究具有较好的参考价值。

The luminous performances of remote phosphor with domed, elliptical and conical shapes under various drive currents and light intensity distributions are researched. A blue LED is used as the light source to excite YAG：Ce3＋ phosphor to emit white light. Meanwhile, constant-current sources and TEC heat sink controllers are used to control LED driving current and heat sink temperature respectively. Comparing the optical and chromatic parameters of three remote packing phosphor samples with different shapes, it is found that the elliptical sample has the best optical characteristics and the highest luminous flux. Yellow-blue ratio （YBR） spatial distribu- tion tests of the three kinds of remote phosphor are performed respectively under different currents. The domed sample shows the best YBR spatial distribution uniformity, ACCTD and ACU value are the best among three samples. Comparing to big angle, the YBR values of the three samples measured closed to 0° decrease at different lev-els for the phosphor layer at the normal direction of the chip far away from the light source and shorter optical path in phosphor, so the excitation effect is different from that of the big angle exit light. Based on experimental phenomenon, shapes of light source encapsulation and phosphor layer become important factors to influence light distribution. Therefore, the exit light path is optimized through changing the packing way of the remote phosphor, which is important to improve remote phosphor illumination performances and has better reference to the research on high power white light LED optical performances.