Author ORCID Identifier

https://orcid.org/0000-0002-4842-1512

Date of Award

Fall 2026

Document Type

Thesis (Ph.D.)

Department or Program

Engineering Sciences

First Advisor

Jason T. Stauth

Abstract

Power conversion circuits have become a bottleneck in terms of reducing the size and cost of modern electronic systems in a vast number of applications ranging from personal devices, to automotive systems, to data centers. This has motivated designs at higher frequencies where smaller passive components can be used. Unfortunately, magnetic components scale poorly to smaller dimensions. In addition, the AC resistance of magnetic components deteriorates due to current crowding effects at high frequencies. This has resulted in fully- integrated power converters with planar magnetic components having efficiencies lower than what may be theoretically achieved. In this work, we investigate high-frequency DC-DC converter circuit techniques that can help solve these challenges. These techniques are especially applicable to air-core magnetic components, which can be integrated in semiconductor processes. One of the main concepts we explore is the use of multi-winding current ballasting. This involves splitting inductor or transformer windings into multiple separate windings with width comparable to the skin depth at the operating frequency. A unique current is forced through each winding to reduce the detrimental high-frequency effects. We resonate each winding with a unique capacitor to ballast the desired current profile across the windings. This is implemented by connecting a unique switched capacitor (SC) converter to individual windings, giving rise to a network of distributed hybrid SC stages to form the overall power converter. Using this technique, we have fabricated two fully integrated DC-DC converters. First, a non-isolated converter with a multi-winding inductor, achieving 84.7% peak efficiency and 0.55 Ω effective resistance in 130 nm SOI technology. Next, a bidirectional isolated converter with a multi-winding transformer that achieves 42.5% peak efficiency at a state-of-the-art 69.6 mW/mm2 power density, fabricated in 180 nm SOI process. These converters use results from theoretical analyses that calculate optimal current distribution for both multi-winding inductors and transformers. A current distribution ensuring equal voltage across all windings minimizes loss in inductors. For transformers, the power transfer efficiency is maximized by ensuring that the ratio of power transfer to power loss for every winding is the same. Implications of these results for planar spiral magnetic components are discussed in detail. We also present a systematic framework for analyzing the dynamics of flying capacitor voltage balancing in hybrid SC converters. We apply discrete-time state-space (DTSS) modeling for the state-transition analysis of these converters. We introduce the use of the linear-algebra-based concept of condition number to compare different hybrid SC converter topologies to better explain their controllability and observability. Finally, eigenvalue-based analysis on the overall passive feedback DTSS model of the converters is performed to compare the settling times of the balancing dynamics of different topologies.

Original Citation

1) K. Datta, Y. Wu, C. Sullivan and J. Stauth, "A Fully-Integrated, Bidirectional, Isolated DC-DC Converter With Distributed 5-Level Driver and Multi-Winding Transformer," in IEEE Journal of Solid-State Circuits (JSSC), 2026, doi: 10.1109/JSSC.2026.3731154

2) K. Datta, Y. Wu, C. Sullivan and J. Stauth, "A Fully Integrated Bidirectional 5-Level Isolated DC-DC Converter with 42.5% Efficiency and 170mW/mm2 Transformer Power Density," 2026 IEEE International Solid-State Circuits Conference (ISSCC), San Francisco, CA, USA, 2026, doi: 10.1109/ISSCC49663.2026.11409225

3) K. Datta, Y. Wu, C. R. Sullivan and J. T. Stauth, "Optimal Current Distribution in Multi-Winding Transformers for Isolated and Wireless Power Transfer," in IEEE Open Journal of Power Electronics, 2025, doi: 10.1109/OJPEL.2025.3590020

4) K. Datta, Y. Wu, C. R. Sullivan and J. T. Stauth, "Optimization for High-Frequency Power Transformers with Multi-Winding Current Ballasting," 2024 IEEE Workshop on Control and Modeling for Power Electronics (COMPEL), Lahore, Pakistan, 2024, doi: 10.1109/COMPEL57542.2024.10614023

5) K. Datta and J. T. Stauth, "Comparison of Voltage Balance and State Estimation Dynamics for Hybrid Switched-Capacitor Converter Topologies," 2023 IEEE 24th Workshop on Control and Modeling for Power Electronics (COMPEL), Ann Arbor, MI, USA, 2023, doi: 10.1109/COMPEL52896.2023.10220968

6) Z. Xia, K. Datta and J. T. Stauth, "State-Space Modeling and Control of Flying- Capacitor Multilevel DC-DC Converters," in IEEE Transactions on Power Electronics, 2023, doi: 10.1109/TPEL.2023.3294061

7) K. Datta, P. H. McLaughlin and J. T. Stauth, "A Fully-Integrated Direct-Conversion Resonant Switched Capacitor Converter with Modular Multi-Winding Current Ballasting," 2023 IEEE Custom Integrated Circuits Conference (CICC), San Antonio, TX, USA, 2023, doi: 10.1109/CICC57935.2023.10121241

8) K. Datta, P. H. McLaughlin and J. T. Stauth, "High-Frequency Resonant Switched- Capacitor Converters with Multi-Winding Current Ballasting: Analysis and Optimization," 2022 IEEE 23rd Workshop on Control and Modeling for Power Electronics (COMPEL), Tel Aviv, Israel, 2022, doi: 10.1109/COMPEL53829.2022.9830024

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