Precise Luminous Flux and Color Temperature Control of Dimmable Bi-Color White Light-Emitting Diode Systems

Abstract

This paper proposes new nonlinear empirical models for practical bicolor white LED systems with feedback control, which provides a holistic understanding of the complex interactions of photometric, electric, thermal and chromatic aspects of such closed-loop LED systems. The proposed models enable precise prediction of luminous flux and correlated color temperature (CCT) based on the control variables in the feedback loop for independently regulating the current across the warm-white and cool-white LED strings. A hardware prototype of a single-inductor dual-output (SIDO) boost LED driver with a time-multiplexing digital control scheme is implemented, which is used to experimentally verify the nonlinear empirical flux and CCT models. The experiment results confirm that the measured values of luminous flux and CCT agree closely with the corresponding predicted ones.