PhD Thesis Proposal: Bahlakoana Mabetha

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"Hybrid DC-DC Converters for Soft Charging Capacitive Loads"

Abstract

Recent trends in technology have seen an increase in actuation, particularly the use of piezoelectric and other electrostatic actuators across applications such as miniaturized robotics, haptics, ultrasound. Electrostatic materials are mainly suited for these applications where a small form factor is essential. These electrostatic materials can be modeled as dominantly capacitive loads, that is, their equivalent model impedance can be approximated to that of a capacitor within their typical operating frequency range. Other applications that present as capacitive loads include ultrasound transducers, transistor gate capacitance, and supercapacitors. Unlike typical resistive loads that consume real power, capacitive loads consume reactive power (or reactive power dominates any real power consumed). Therefore, different circuits, operation, and optimization is required to drive these loads.

Several DC-DC converter architectures have been explored on delivering reactive power efficiently in applications of such capacitive loads. A review of these past works will be highlighted, including a comparison of applications and operating conditions where each topology might be preferred. This thesis proposal explores the use of hybrid DC-DC converters to drive electrostatic loads where high voltage, high power (energy) density, and high efficiency are important. In particular, techniques on how to leverage the benefits of different single stage topologies to develop hybrid topologies that process (deliver and recover) reactive power to soft charge the load will be discussed. Modeling and operation of magnetic buck-boost converter and switched capacitor converter as single stage topologies that are suited for hybrid architectures to achieve complete soft charging of the load will be detailed. Optimization and implementation of hybrid soft charging converters is presented, highlighting their benefits as a pathway towards high energy density converters for capacitive loads. Future work on the integrated circuit implementation of the converter will be discussed including key circuit blocks that enable soft charging.

Thesis Committee

• Prof. Jason T. Stauth (Chair)
• Prof. Charles R. Sullivan
• Prof. William J. Scheideler

Contact

For more information, contact Thayer Registrar at thayer.registrar@dartmouth.edu.