Research On LED Temperature Spectrum Compensation Based On Visual And Non-visual Effects

With the continuous in-depth research on Photobiological effect,people have realized that light participates in the regulation of human physiological functions such as physical signs,hormone secretion and circadian rhythm through the non-visual channels of the human eye,which has an impact on physical and mental health and work efficiency.Therefore,lighting engineering must focus more on the comprehensive impact of light sources on the human body,and design a more intelligent and healthy personalized lighting system.As a new generation of green light source,LED(Light Emitting Diode)is widely used in various fields,but temperature is an important factor that affects the quality of the light source.Self-heating and extreme external environment make the operating temperature of LED change,causing the light source parameters to shift and affecting the stability and the performance of the light source,which in turn affects the visual and non-visual effects of the light source.Reducing or even eliminating the influence of temperature on LED spectrum and light source parameters is an important content of the research on the stability and controllability of healthy lighting systems.In this paper,the following researches are carried out on the compensation of LED temperature spectrum model and light source parameters.The research content of this paper is divided into two parts.In the first part,we first fits the spectrum of a single-channel light source through three spectral models,then builds an experimental test platform and a light source driving system,and conducts experiments to determine the spectral parameters of the single-channel LED light source and the heatsink temperature.The temperature spectrum model of the multi-LED mixed light source is established based on the principle of spectral linear superposition;in addition,this paper conducts temperature experiments on the RGBY four-color LED mixed light source(using D50 and D65 light sources).The experimental results show that the LED spectrum calculated by the temperature spectrum model under different heat sink temperatures is basically the same as the measured spectrum,and the maximum relative error of the two light source parameters do not exceed 6.15%,which verifies the reliability of the model.In the second part,in view of the temperature-induced changes in light source parameters(illuminance,correlated color temperature,circadian rhythm factors),based on the temperature spectrum model proposed in the previous section,the differential evolution algorithm is used to determine the compensation weight of each channel in the pulse width modulation control system in real time,which realize light source parameter compensation according to the feedback of heat sink temperature to weight.Meanwhile,the temperature compensation experiment was carried out on D50 and D65 light sources.The experimental results found that the absolute difference ratio of illuminance of D50 light source/D65 light source at 120℃ was compensated from25.4%/24.4% to 2.7%/2.6%,and the absolute difference ratio of correlated color temperature is compensated from 23.5%/22.6% to 5.4%/5.4%,and the absolute difference ratio of the circadian action factor is compensated from 14.9%/8.3% to10.3%/6.7%.The results show that spectral compensation based on the temperature spectrum model and DE algorithm is effective and feasible.