High-density high-efficiency power magnetics

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University of Alabama Libraries

This dissertation presents several concepts and techniques in order to (1) increase the inductance density and power density of power inductors (PIs) with high power efficiency and (2) achieve magnetically coupled wireless power transfer (WPT) systems with higher efficiency and longer transmission distances under varying conditions. Chapter 1 provides an overview and introduction on applications of power magnetic devices and systems along with the challenges facing the state-of-the-art PIs and WPT systems. Chapter 2 develops a concept which results in doubling the saturation current of a high current PI with NdFeB permanent magnet (PMPI). By adding a well-designed small piece of fabricated NdFeB magnet in the air gap of the PI, the saturation current of the PMPI is doubled with the same size and inductance value. Chapter 3 presents a two-phase coupled power inductor (CPI) that utilizes a PM in order to achieve almost doubled saturation current with the same size compared to the CPI and more than 70% core size reduction compared to the single-phase non-coupled PIs. Both the PMPI and PMCI concepts are experimentally verified in DC-DC power converter prototypes. Chapter 4 and 5 present a two-coil and a four-coil reconfigurable WPT system topology, respectively, in order to optimize transmission efficiency under different distance and misalignment conditions. The two-coil reconfigurable WPT system achieves re-configurability by switching between different values of series and shunt capacitors at Tx side and/or Rx side. The four-coil reconfigurable WPT system achieves re-configurability by switching between different sizes of drive loops and load loops. Experimental results verified effectiveness of developed reconfiguration methods. Chapter 6 presents a method to achieve wired power conversion and WPT using a hybrid “Power Converter-WPT system”. By achieving WPT using AC switching ripple of power converter, the system eliminates the need for a transmitter stage of conventional WPT system, which could be beneficial for system size and cost reduction. The method is verified and demonstrated using Buck-WPT system as an example. The last chapter summarizes this work and provides conclusions before discussing some possible future research directions related to the dissertation work.

Electronic Thesis or Dissertation
Electrical engineering