Date of Graduation

12-2012

Document Type

Thesis

Degree Name

Master of Science in Electrical Engineering (MSEE)

Degree Level

Graduate

Department

Electrical Engineering

Advisor/Mentor

Mantooth, H. Alan

Committee Member

Ang, Simon S.

Second Committee Member

Balda, Juan C.

Keywords

Applied sciences; Dc-dc converters; Isolation; Optocoupler; Photoelectronics; Power system

Abstract

There is a need for power switches that can operate at high voltage, high temperature, and high switching frequencies with low losses. Power switches fabricated from wide bandgap materials such as silicon carbide (SiC) or gallium nitride (GaN) can outperform conventional silicon switches due to material property advantages. Another common problem in grid-connected applications is the need for high voltage-isolation of gate drivers and control circuitry while operating efficiently at the high switching frequencies, high power density, and high temperatures made possible by wide bandgap devices. Transformers cannot operate at the temperatures of these wide bandgap devices and a new solution needs to be determined to operate at higher temperatures with smaller footprints. The purpose of this research is to determine the baseline performance of the current technologies used to isolate gate driver and control signals from high voltage power electronics. Research was conducted to determine the characteristics of current optical isolation technologies and implementation techniques in the specific areas of propagation delay, linearity, power consumption, and voltage isolation to determine the baseline performance that future devices could improve upon. The techniques employed to operate the current optocoupler technology were looked at individually and implemented in a Buck converter to determine the performance characteristics with respect to the figures of merit above. The results of the research were that although optocouplers can be used in many different functions the current technology benchmark lacks the robustness of speed, noise immunity, and easy implementation to compete with current workhorse technologies like transformers. The linearity of transmitted analog signals, transmission speed of digital control signals, and the maximum allowable voltage between power stage and control circuitry will need to be improved by future optocoupler technologies like GaN to compete with current isolation techniques.

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