双通道PWM的冷暖白光LED混色模型研究

A study on colour mixture model for cold and warm white LEDs based on two-channel PWM

LED光色度的动态调节是实现智能照明的基础,采用冷暖白光LED和双通道脉冲宽度调制(PWM)法,基于1931 CIE标准建立混合光源模型,推导出混合光源色坐标、相关色温、最大亮度、显色指数与双通道调制脉冲占空比比值的关系式。采用暖白光(色温3 282K)和冷白光(色温12 930K)两种白光LED进行混色实验,通过微控制器输出PWM信号控制LED驱动电源,改变冷色光和暖色光的比重,得到的混合光源色坐标、最大亮度、相关色温及显色指数值与理论计算值吻合很好,证明了理论模型的正确性。理论和实验结果还表明,混合光源在双通道调制脉冲占空比比值为1的附近可得到低色温、高显色性和大光通量的混合白光。

In this paper a hybrid light model is proposed based on the 1931 CIE standard using cold and warm white light emitting diodes（LEDs）and two-channel pulse width modulation（PWM）.From the theoretical model,the relationships between chromaticity coordinate,of mixed light source,correlated colour temperature,maximal luminance,colour rendering index and the radio of duty ratio of two-channel PWM are derived.A mixed colour experiment is conducted using two white LED samples with cold（3 282K）and warm（12 930K）color temperatures respectively.LED drive power and the proportion between cold and warm white light are controlled by a micro-controller via the PWM output signal.The experimental results of chromaticity coordinate of mixed light source,correlated colour temperature,maximal luminance and color rendering index agree with the theoretical values very well,suggesting the theoretical model is valid.Theoretical and experimental results also show that the mixed white light with low color temperature,high color rendering index and high luminous flux can be obtained when the ratio of duty cycle of two-channel PWM is around 1.