LED 광원의 열-전기-광학 특성 관계와 최대 광선속 변화에 관한 연구

Optical power of an LED light source is directly affected by temperature. To understand and solve the degradation of light output and light efficiency due to heat generation in an LED, the relationship among thermal, electrical, and optical properties of the LED should preliminarily be investigated. This study aims to reveal the thermal, electrical, and optical relations of a single-chip LED light source and the conditions of its maximum luminous flux. First, the thermal, electrical, and optical relations based on the energy conservation law are derived to propose a dynamic multi-physical model of the LED light source. Then, the luminous efficacy, relative rate of luminous efficacy reduction with increasing junction temperature, thermal resistance of the LED junction, and heat dissipation coefficient of the LED are obtained based on its specifications and the experimental results. These parameters are implemented in the proposed model using Matlab software. Simulation results show the relationship between the power consumption of the LED and its relative luminous flux based on a quadratic function. The variations of the maximum luminous flux according to the change in the thermal resistance and power consumption of the lighting system are observed. Finally, considerations that should be taken into account to obtain the maximum luminous flux from a lighting system are discussed. This study will be helpful to design a lighting fixture using LED light sources.