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MS Thesis Defense: Benjamin L. Dobbins

Thursday, December 3, 2020, 1:00pm


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“A Programmable Switching Waveform Generator for Switched Capacitor Networks in Power Converters”


Advances in manufacturing, transportation, and portable computing have created the need for small, high efficiency, and high-density power converters. Traditionally, power delivery for these applications has been realized using inductor-based buck and boost converters. As volume overhead becomes more limited, these approaches remain limited by their reliance on magnetic components, which scale poorly to small size. This constraint, along with the need for increased conversion ratios, has driven the exploration of alternative converter architectures that leverage the high energy density of capacitors to minimize the need for large inductors.

This work focuses on a family of converters known as hybrid switched capacitor (SC) converters, which have been found to have favorable trade-offs between efficiency, energy density, and size compared to traditional buck and boost converters. Hybrid SC converters merge a reconfigurable network of capacitors connected by switches with a small inductive output stage. By relying primarily on high-density capacitors to shuffle energy between the input and output voltage domains, switches are only required to block a fraction of the input voltage. Meanwhile, the energy storage requirements of the inductor are greatly reduced, with the small output inductor serving to eliminate charge transfer losses between flying capacitors. These benefits allow this family of converters to achieve high efficiency and power density at small scale.

While these trade-offs are favorable, the operation of SC based power converters is more complex than traditional buck and boost converters as SC converters typically have many switches which require unique control signals. This thesis presents a programmable digital architecture used to generate switch control signals for SC networks. To motivate the need for an easily tunable switch control circuit, the switching requirements of an exemplary hybrid SC converter, the flying capacitor multilevel (FCML) converter, are discussed. The digital switch control architecture is presented and two examples of its implementation in FCML based research projects are explored—highlighting the architecture’s facilitation of rapid bench-top prototyping and the ease of integration of the architecture into larger designs.

Thesis Committee

For more information, contact Daryl Laware at