Revisiting multi-domain empirical modelling of light-emitting diode luminaire

In this work, an empirically derived multi-domain model of a light-emitting diode (LED) luminaire is proposed. The optical, electrical, and thermal characteristics of LEDs are obtained from the data sheets provided by manufacturers. Both transient and steady-state performance of LED luminaire were realized theoretically and validated against experimental findings from earlier investigations. The difficulties encountered in creating an ideal LED luminaire are discoursed and examined. Most of the studies on LED luminaires described in prior works ignored the influence of luminaire housing and optics on the thermal management of the luminaire. Knowledge of thermal time constants of LED luminaires is important, as they decide the rate of luminous flux decay when LED lighting systems are used for long periods of operation. Thermal time constants also decide the time taken by the LED junction to reach steady state with its surrounding. From the study it is inferred that the increase in junction temperature and deterioration of luminous flux is controlled by the product of the single most dominant thermal resistance from the junction to a point along the heat conduction path and sum of all the downstream thermal capacitances. This is true as in most cases LED device thermal capacitance is very less related to the thermal capacitance of the heat-sink, hence the product of single most dominant thermal resistance and thermal capacitance of heat-sink decide the rate of rising of junction temperature or luminous flux deterioration.本研究提出了一种由实验推导得到的发光二极管（LED）多领域模型。LED的光学、电学与热学特性均取自厂商提供的产品数据表。本研究通过理论推导得到了LED灯具的瞬态与稳态性能，并与既往研究的实验结果进行了验证。本文对构建理想LED灯具过程中遇到的各类难题进行了探讨与分析。既往文献中提及的绝大多数LED灯具研究，均忽略了灯具外壳与光学结构对灯具热管理的影响。了解LED灯具的热时间常数至关重要，因为当LED照明系统长期运行时，热时间常数决定了光通量的衰减速率；同时，热时间常数也决定了LED结温达到与环境热平衡所需的时间。本研究推导得出：结温升高与光通量劣化的速率，由LED结至热传导路径上某一点的单一主导热阻，与所有下游热容量之和的乘积所决定。这一结论成立的原因在于：多数场景下，LED器件的热容量远小于散热器的热容量，因此单一主导热阻与散热器热容量的乘积，即可决定结温的上升速率或光通量的劣化速率。