提出了一种基于脉冲宽度调制(PWM)的红/绿/蓝/暖白(R/G/B/WW)4色发光二极管(LED)调光调色计算模型。该模型根据二通道和三通道PWM的特点,采用黑体轨迹的Chebyshev方法,确定合成光的色坐标和相关色温(CCT)关系。在优化目标显色性能最佳时,建立了混合光的色坐标与占空比、相关色温与占空比的函数关系,并采用R/G/B/WW 4色LED进行实验验证。结果表明:R/G/B/WW LED模块可实现相关色温在2900~7600 K范围的白光调节。当光通量设定为300 lm时,相关色温的最大相对误差为0.99%,混合光一般显色指数(CRI)最大相对误差为0.11%;当光通量值在[150,800]范围内变化时,其最大相对误差为2.02%。该模型可应用于4通道LED调光调色,其计算方法简单、调光精度高、硬件易于实现。

This paper proposes a dimming calculation model for red/green/blue/warm-white (R/G/B/WW) light emitting diode (LED) based on four channels’ pulse width modulation (PWM). According to the characteristics of two-channel and three-channel PWM, the proposed model adopts Chebyshev method of black body locus to determine the relationship between chromaticity coordinate and correlated color temperature(CCT) of the synthesized light. When the color rendering performance is optimized, the functional relationships between chromaticity coordinate and duty cycles, CCT and duty cycles of the mixed light are established. And the experimental verification is carried out with R/B/G/WW LED. The experimental results show that R/G/B/WW LED module can realize a wide range of CCT tunable white light from 2900 K to 7600 K. When the luminous flux is set to 300 lm, the maximum relative error of CCT is 0.99%, and the maximum relative error of color rendering index (CRI) of the mixed light is 0.11%. When the luminous flux changes in the range of [150,800], the maximum relative error is 2.02%. The model can be applied to LED dimming of four channels. And its calculation method is simple, the dimming precision is high, and the hardware is easy to implement.