Taking Advantage of the Sum of the Light in Outphasing Technique for Visible Light Communication Transmitter

Visible light communication (VLC) takes advantage of the widespread use of the light-emitting diodes (LEDs), and by modifying the driver stage, the LEDs are capable of lighting and transmitting information. One of the main drawbacks is the low power efficiency due to the modification of the LED driver stage in order to add the communication capability. Most of the research work related to VLC is toward the communication task, whereas there is a limited work about the improvement on power efficiency. This article proposes a high-efficiency LED driver for VLC working as a transmitter based on the outphasing technique. This technique is used also in radio frequency (RF) communications and increases the efficiency of the amplifiers. The proposed transmitter is made up of two switching-mode power amplifiers that reproduce the signals required for the outphasing technique and a dc/dc converter that biases the LEDs. The proposal exploits the light and, instead of being added electrically, the signals are added in their light form, which leads to a reduction in the complexity of the design. As experimental results, a transmitter was built of two Class E amplifiers reproducing a 16-QAM modulation, achieving a signal-generation efficiency of 78% and an overall efficiency of 92%.