ABSTRACT Broadband visible light-emitting diodes (LEDs) are now being used for applications where high-quality tunable light is needed. These LEDs are based on phosphors with wide emission bands (full width at half maximum, FWHM, of 70 nm or more). We describe the time-dependent characteristics of light emission from such devices. We found time lags in both luminescence buildup and decay as the broadband red, green and white LEDs are pumped by square pump photon flux. The reasons for such delays are photon percolation in phosphor/light scatterer blends and luminescence persistence due to defects in phosphors. The latter part of the paper describes a setup for combining light from phosphor-based red and green broadband LEDs with that of a band-edge emission blue LED to produce white light. It is shown that the chromaticity of white light can be changed stably by changing the frequency/duty cycle of PWM waveforms that are used for controlling red, green and blue LEDs. We also introduce a new LED drive scheme where PWM signals are converted to steady DC levels before driving LEDs. The setup described here enables the generation of full-spectrum white light with electrically controllable chromaticity.

中文翻译：

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宽带发光二极管的时间发光及其用于产生可定制的白光

摘要宽带可见光发光二极管 (LED) 现在被用于需要高质量可调光的应用。这些 LED 基于具有宽发射带（半高全宽，FWHM，70 nm 或更大）的磷光体。我们描述了此类设备的光发射的时间相关特性。我们发现，由于宽带红色、绿色和白色 LED 由方形泵浦光子通量泵浦，因此发光积累和衰减都存在时间滞后。这种延迟的原因是磷光体/光散射体混合物中的光子渗透和由于磷光体中的缺陷导致的发光余辉。论文的后半部分描述了一种将基于磷光体的红色和绿色宽带 LED 的光与带边发射蓝色 LED 的光相结合以产生白光的设置。结果表明，通过改变用于控制红色、绿色和蓝色 LED 的 PWM 波形的频率/占空比，可以稳定地改变白光的色度。我们还介绍了一种新的 LED 驱动方案，其中 PWM 信号在驱动 LED 之前转换为稳定的直流电平。此处描述的设置能够生成具有电子可控色度的全光谱白光。