Development of LED Driver Circuit Architectures for Future Generation Visible Smart Lighting Networks, Combining High-Speed Data Communication and Illumination Control.
Abstract: 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 ... read morelifetime, 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.
Thesis (Ph.D.)--Tufts University, 2015.
Submitted to the Dept. of Electrical Engineering.
Advisor: Valencia Koomson.
Committee: Aleksandar Stankovic, Mark Cronin-Golomb, and Eko Lisuwandi.
Keyword: Electrical engineering.read less