A Linear Current Driver for Efficient Illuminations and Visible Light Communications

This paper presents a linear current driver for simultaneous illuminations and high-speed visible light communications. Our proposed driver integrates a high-efficient converter, a preequalizer, and a high-bandwidth transconductor with an emitter equalizing stage together. In order to enhance the bandwidth and stability, we present an accurate model of our proposed driver to analyze the major impact factors precisely and to indicate the methods to eliminate the effects of parasitic components. Accordingly, we demonstrate a single-capacitor bypass compensation approach to improve the stability without reducing too much bandwidth. The experimental results are in good agreement with our theoretical model analyses and illustrate the optimal intervals for parameter configurations. Through the optimized implementation, we achieve a peak data rate of 2.0 Gb/s with 256-quadrature amplitude modulation (QAM), when driving ten series light-emitting diodes (LEDs) (12 W in total). The efficiency of transconductor core is 87%, and the overall efficiency is 76.6%. At the same time, the -6 dB bandwidth of this driver is expanded to 573 MHz in -20 dBS gain and 184 MHz in 0 dBS gain. The peak spectral efficiency enlargement compared to the conventional voltage driver is nearly 42.8% (from 128 to 1024 quadratic-amplitude modulation) under the same output power. To the best of our knowledge, this is the first report of implementing a high-power Gb/s visible light communication driver and efficient lighting simultaneously thus far.