With increasing calls of electrification for transportation (e.g., electric vehicles, hybrid or electric aircraft), the need for systematic guidelines that gauge passive component specific energy density for weight-optimized converter design has become apparent. Observing a lack of data sets and corresponding modeling process for passive components that usually dominate a converter's weight, this work proposes a transformation that estimates the specific energy density of passive components from comprehensively surveyed volumetric energy density data and empirical specific density models, and thus forms a convenient guideline for converter weight optimization. The proposed model is then applied to a converter designed for electric aircraft applications to showcase the component mass estimation and selection process along with estimation accuracy.

The flying capacitor multilevel (FCML) converter has shown promise for high step-up/down conversion ratio applications due to its relatively low switch stress and small inductor volume. For higher level-count (N ≥ 3) variations of this topology, there is limited research on resonant mode operation, despite its potential to yield considerable performance benefits for fixed conversion ratio applications. When operating resonantly, the decreased inductance requirement compared to regulated operation can further reduce the magnetic volume and improve transient response, while also allowing for zero-voltage/zerocurrent switching (ZCS/ZVS). This work presents and analyzes a clocking scheme required to operate an N :1 FCML converter both at-resonance and above-resonance, while maintaining minimum current ripple for reduced losses. A complete derivation is presented, enabling the calculation of precise phase durations as a function of switching frequency. Moreover, a 5:1 FCML hardware prototype is demonstrated, verifying intended operation both atand above-resonance, in addition to highlighting the achievable loss reduction with the proposed switching scheme.

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Proper utilization of GaN devices generally necessitates ultra-low inductance printed circuit board (PCB) layout in the main commutation loop or switching cell of a power converter. The flying capacitor multilevel (FCML) topology in particular contains many of these switching cells, thus design optimization becomes critical. A novel asymmetrical cell layout design with sub-1 nH commutation loop inductance is proposed and characterized for the FCML by utilizing a transient-and impedance-based measurement technique in conjunction with 3D field simulation. To validate its efficacy, this switching cell design is demonstrated within a prototype high performance step-down intermediate bus converter supply (vout = 48 V) with wide input voltage range (v in = 48 to 340 V).

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