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Efficient, small, and reliable dc-dc power converters with high power density are highly desirable in applications such as aerospace and electric vehicles, where battery storage is limited. Bidirectional full-bridge (FB) dc-dc converters are very popular in medium and high-power applications requiring regenerative capabilities. Full-bridge topology has several advantages such as: Inherent galvanic isolation between input and output as well as high conversion ratio due to the transformer with a turns ratio n. Reduction in passive component sizes due to the increase in inductor current frequency to twice the switching frequency. Reduced voltage stresses on the low-voltage side switches and current stresses on the high-voltage side switches. However, due to the high number of switches, device losses increase.

In aerospace applications, it is important to have efficient, small, affordable, and reliable power conversion units with high power density to supply a wide range of loads. Use of wide-band gap devices, such as Silicon Carbide (SiC) and Gallium Nitride (GaN) devices, in power electronic converters is expected to reduce the device losses and need for extensive thermal management systems in power converters, as well as facilitate high-frequency operation, thereby reducing the passive component sizes and increasing the power density. A performance comparison of state-of-the art power devices in a 10 kW full-bridge dc-dc buck converter operating in continuous conduction mode (CCM) and at switching frequencies above 100 kHz will be presented in this manuscript. Power devices under consideration are silicon (Si) IGBT with Si antiparallel diodes, Si IGBT with SiC antiparallel diodes, Si MOSFETs, SiC MOSFETs, and enhancement-mode GaN transistors.

MEMS (Microelectromechanical Systems), as a technology, represents a new paradigm for integration of computational functions with elements that interact with the physical world. By combining mechanical moving parts with more traditional integrated circuits, new capabilities exist for sensing/actuating systems not previously possible. In developing MEMS, fundamental issues of packaging and fabrication have required considerable attention. An analogous group of technologies are emerging which combine chemically reacting elements with computational functions. These might be referred to as Microelectrochemical Systems. Examples include chemical sensors and actuators, as well as on-board chemical sources of energy, such as microscopic batteries, fuel cells, energy harvesters. The merger of chemical systems and computational capabilities requires us to address a host of issues such as packaging and fabrication, as was (and is) needed with MEMS.

Battery state of charge meters based on combining fuzzy logic analysis and either Coulomb counting or battery impedance measurements have been designed, fabricated and tested. The Coulomb counting meters have been implemented in digital hardware using Motorola 68HC11 and 68HC12 microcontrollers and in field programmable gate arrays. The impedance meter has been prototyped in analog hardware using discrete components. In this paper, we present the hardware/software designs for these meters and some test results on primary Li/SO2 cells.