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Power electronic simulations.

How to convert the electrical power obtained from the outlet in your home from the form of an alternative current with a voltage amplitude of 220 Volts and a frequency of 60Hz to a direct current at 5 Volts for use in your computers is a goal of the Power Electronics discipline, which aims at converting efficiently and compactly one form of electrical power into another. On this subject, Dr. Vu-Quoc has been working closely with EE Prof. K.T.D. Ngo, an expert in this field.

A Power Electronic Module (PEM) includes the following components: Power devices (diodes and seminconductor transistor devices such as MOSFETs, IGBT, etc.), magnetic components (transformers, inductors), and capacitors. The current trend is to integrate all these components into ever shrinking power electronic modules. Thermal dissipation is an essential concern for the operation of these models. Most design incorporates a substrate of high conductivity, called heat spreader, to quickly dissipate the heat generated from the transistors. The figure below depicts the internal structure of a PEM, showing the location of the power devices and the heat spreader.

To design PEMs, it is important to simulate the response of the electronic components and of the heat sinks or heat spreaders. The electronic circuitry is governed by nonlinear ordinary differential equations (ODEs), whereas the thermal problem is governed by a partial differential equation (PDE). Traditionally, circuit designers use circuit analysis software such as SPICE, SABER, etc. to analyze their circuits, without accounting for the thermal problem. To facilitate the design process, it is important in practice to simulate the coupled electro-thermal problem in the same circuit software environment. Dr. Vu-Quoc, together with his former graduate student J.T. Hsu, has developed a method to convert the discretized thermal PDE into equivalent circuit networks for simulating the complete coupled electro-thermal problem within the same circuit analysis code. They also applied model-reduction techniques to electro-thermal simulations. Their publications in the {IEEE Transactions on Circuits and Systems} immediately received some attention; as a result, Dr. Vu-Quoc received funding to develop model-reduction techniques for the simulation of micro-electro-mechanical systems (MEMS). Prof. Ngo and J.T. Hsu later generalized this method to treat the coupled electro-magneto-thermal problems.

Capacitors act as electrical buffers that divert spurious electrical signals, and store surges of charge that could damage the circuits or disrupt their operation. These electronic guardians of all electrical circuits are present in PEMs. Miniaturization is an urgent priority of the capacitor industry, because the advantages of shrinking PEMs cannot be realized if capacitors did not shrink with them. Dr. Vu-Quoc, together with his former students, Dr. V. Srinivas and Mr. J. Langford, has developed a finite element formulation and model for analyzing Advanced Multilayer Capacitors with novel geometry patented by Prof. Ngo. He also developed accurate models for ferroelectric materials, which as used as dielectric materials in capacitors.