Benjamin K. Rhea

High efficiency data center power supply using wide band gap power devices

The energy efficiency of typical data centers is less than 50% because more than half of the power is consumed during power conversion, distribution, cooling, etc. In this paper, a combination of two approaches to improve power supply efficiency is implemented and experimentally verified. One approach uses a high voltage DC architecture, designed to reduce distribution loss and remove unnecessary power conversion stages. The other approach employs wide band gap (WBG) power devices, including silicon carbide (SiC) and gallium nitride (GaN) FETs and diodes, which helps to increase converter efficiency and power density. Scaled down prototypes of all power conversion stages in the data center power supply chain are designed, built, and tested. The advantages of utilizing WBG power devices are illustrated through simulations and then verified by experiment.

Design and implementation of planar inductors for low voltage GaN-based power converters

The design and implementation of planar inductors in low voltage GaN-based applications is investigated, and design techniques conducive to inexpensive, simple implementations are utilized. The advantages and limitations of planar technology, as it relates to filter inductors, are presented. Design considerations such as core material, core geometry, number of turns, gap size, fringing fields, and winding construction are addressed, and several planar inductors are evaluated in a 12-to-1 V GaN-based synchronous buck converter. Experimental results are used to determine the feasibility and advantages of replacing commercially packaged components with planar inductors. The primary focus is to reduce inductor core loss, winding loss, size, and raise saturation current by employing well-designed planar inductors to modern, wide-bandgap power converters.

Optimization of a 96% efficient 12–1 V Gallium Nitride based point of load converter

A 12-1 V Gallium Nitride based POL converter demonstrates over 96% efficiency and under 4 ns switching time. This is accomplished through a layout technique that does not require costly microvias but still minimizes parasitic inductance to support fast switching. A single-sided synchronous buck converter phase operates up to 30 A in a 5.6 cm2 (0.87 in2) package that outperforms other commercially available and published POL converters, and size could be reduced by over 40% in a similar double-sided design. Part selection and layout techniques are explored among three POL versions with incremental improvements. Expansion to multiple phases is explored, and experimental data illustrates that switching losses are remarkably low. This work shows how to properly employ modern wide bandgap semiconductor technology in power supply design for highly efficient DC-DC conversion.

A Novel Third Order Analog Chaotic Oscillator

Chaotic oscillators, which are characterized by a spread spectrum response, have a wide range of possible applications including random number generation, communication systems, noise signal generation, and jamming. A novel chaotic oscillator design and implementation that reduces design complexity, component count, and size over a traditional approach is presented. The oscillator design approach can be divided into three primary subsystems. The first subsystem is called the stretching mechanism, which exhibits an exponential unstable sinusoidal response as a standalone system. This unstable subsystem is bounded by a feedback network. The feedback network consists of guard condition and a folding mechanism. The stretching mechanism will grow until a criterion for the guard condition is met which triggers when the folding mechanism should fold, or double. The motivation behind this design was inspired by the linear second-order set of differential equations with an exactly solvable solution. The electronic...

A 4 MHz Chaotic Oscillator Based on a Jerk System

Chaotic oscillators have a wide range of possible applications including random number generation (RNG), a stimulation source for characterization of MEMS devices, spread spectrum communications, and audio range and RF noise sources. Some distinct characteristics of chaotic systems include topological mixing, determinism, long-term aperiodic behavior, sensitivity to initial conditions, as well as a spread spectrum response. In particular, the aperiodic behavior and sensitivity to initial conditions make chaotic oscillators an ideal candidate for RNG. In practice, one of the more important aspects of a RNG is the speed at which data/bits can be generated. In electronics, as the frequency of operation increases, so do the design restrictions and challenges. In addition, many of these chaotic systems are based on nonlinearities or complex math functions that are difficult to implement in electronic circuitry. Through careful selection of the system’s structure, complex behavior can be achieved in electronic circuitry with minimized component count, footprint and power consumption. Additionally, this concept reduces the design complexity compared to traditional techniques, and the jerk chaos architecture can aid in increasing the fundamental frequency by minimizing feedback paths in the chaotic oscillator. Presented in this work is a printed circuit board electronic implementation of a 4 MHz chaotic jerk system that exhibits complex, rich dynamics using very simple electronic circuits.

A Matched Filter Developed for Chaotic Waveforms

A matched filter developed for use in chaos-based communications systems is presented. A matched filter is the optimum filter for maximizing the signal-to-noise ratio of a received signal in the presence of additive Gaussian white noise (AGWN). Chaos-based communications systems encode information into a chaotic waveform using arbitrary small perturbations to control the trajectory of the chaotic oscillator. Chaotic waveforms are deterministic, are sensitive to initial conditions, have aperiodic long-term behavior, have a spread frequency spectrum, and are theoretically immune to interference. There has been great interest in using chaotic waveforms in communication applications. One reason for this interest is that the spread spectrum of a chaotic waveform gives the appearance of noise when observed over a prolonged period of time. This masks the waveform from anyone without prior knowledge of its presence. Another reason is that to retrieve the information encoded in the chaotic waveform, complete knowl...