Development of LED Driver Circuit Architectures for Future Generation Visible Smart Lighting Networks, Combining High-Speed Data Communication and Illumination Control

With the development of semiconductor-based light generated by light-emitting diodes (LEDs), the second generation of lighting known as solid state lighting (SSL) has been shown to provide greater energy efficiency compared to the conventional incandescent light bulb. The vision for SSL technology is to attain the full potential of light by capitalizing on energy efficiency, long lifetime, and improved sustainability. The light modulation capability of LEDs has produced considerable interest in the use of solid-state illumination systems for data communication. Visible light communication (VLC) has a number of unique advantages from ecological and human health perspectives; and the optical range is free from regulation, resulting in high data rate channels. Dual-purpose indoor LED lighting systems providing illumination control and data communication requires novel LED driver circuit architectures to realize the plethora of VLC-based applications envisioned for future lighting networks. This thesis presents research on novel driver circuit architectures for VLC applications. The driver circuit architecture presented in this work overcomes the modulation bandwidth limitation by providing a feedback control loop to maintain the DC-DC converter output voltage independently of the LED drive signal to control data modulation and dimming. The main challenge of implementing a fast link in VLC networks is emanated from the inherent bandwidth limitations of LEDs. In this work the conventional methods of extending the bandwidth of LED drivers are reviewed and proposed topologies are introduced. Seven distinct methodologies of negative impedance converter (NIC), equalization techniques, pulse shaping, peaking, pole-zero cancellation, time-interleaved LEDs, and 16-level PAM are presented. The concept of NIC is reviewed and two different modes of fixed and floating structures with their corresponding proposed LED drivers are introduced. Pre- and post-equalization techniques are analyzed such as multiple resonant, and active and passive equalizations are methods, which compensate the roll-off in the transfer function of raw-LED, leading to bandwidth extension. An LED driver based on a pulse shaping circuit topology is presented which enhances the overall bandwidth of the VLC link by shortening the rise and fall times. The next method for bandwidth enhancement is peaking. Different peaking techniques such as shunt, series, (bridged) shunt-series and triple resonant peaking techniques are reviewed and a new technique called bridged-shunt-zero peaking is proposed. A peaking technique called bridged-shunt-zero peaking is presented in this work, which is suitable for incorporation into the LED driver circuit design. An LED driver with enhanced bandwidth using the pole-zero cancellation methodology is presented to overcome the inherent bandwidth limitation of LED device. Time-interleaved LEDs is yet another trend in compensating the low bandwidth of LEDs. In this method each binary input is sent with a fixed delay and it can be detected by processing the received signals. Finally, an LED driver that implements 16-level PAM signaling using a 4 x 4 array of LEDs is described, yielding an increase in the data transmission rate by 4 times.