Design of a 1 kV bidirectional DC-DC converter with 650 V GaN transistors

Stillwell, Andrew; Blackwell, Margaret E.; Pilawa-Podgurski, Robert C. N.

doi:10.1109/apec.2018.8341162

Cited by 17 publications

(13 citation statements)

References 23 publications

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“…3 shows the inductor current ripple at a fixed switching frequency, f sw , and fixed inductor, L, for a 4and 5-level FCML normalized to the conventional two-level buck converter, with current ripple valleys at duty cycles of 0.33 and 0.66 for the 4-level FCML, and 0.25, 0.5, and 0.75 for the 5-level FCML. Previous works [8], [9] have shown that by varying the switching frequency along the duty cycle range, the inductor current ripple can be changed to maintain ZVS operation. However, the switching frequency can only be decreased to limits imposed by the flying capacitor ripple, inductor saturation, or practical limitations [9].…”

Section: Zero-voltage Switchingmentioning

confidence: 99%

“…Previous works [8], [9] have shown that by varying the switching frequency along the duty cycle range, the inductor current ripple can be changed to maintain ZVS operation. However, the switching frequency can only be decreased to limits imposed by the flying capacitor ripple, inductor saturation, or practical limitations [9]. These switching frequency limitations are summarized in Subsection III-C along with an evaluation of how the resonant frequency should be factored in to the ZVS frequency limitation.…”

Section: Zero-voltage Switchingmentioning

confidence: 99%

“…As mentioned above, there are limitations placed on the lower limits of the converter switching frequency, which prevent zero-voltage switching conditions. These limits, summarized in Table II for 5-level operation, are due to converter components [9], such as inductor current saturation or flying capacitor voltage ripple, and due to converter operation (i.e. resonance) [24].…”

Section: Frequency Limitationsmentioning

confidence: 99%

“…resonance) [24]. In [9], the component frequency limitations are derived for 4-level operation. Moreover, the resonant frequency of the converter must also be accounted for when determining the lower limit on switching frequency.…”

Section: Frequency Limitationsmentioning

confidence: 99%

“…Further reduction in volume can be achieved through higher frequency switching at the cost of higher switching losses. To mitigate these switching losses, zero-voltage switching (ZVS) can be employed at selected duty cycles as shown in [8], [9] through variable frequency control. However, both works noted the challenges of obtaining ZVS at specific duty cycles inherent to FCML operation.…”

Section: Introductionmentioning

confidence: 99%

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Dynamic Level Changing for Full Range ZVS in Flying Capacitor Multi-Level Converters

Blackwell

Stillwell

Pilawa-Podgurski

2022

IEEE Open J. Power Electron.

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This paper presents a control technique for flying capacitor multi-level (FCML) converters to achieve zero-voltage switching (ZVS) across the full range of duty cycles, with application in high power density and high efficiency power converters. Previous works have used variable frequency control to enable ZVS at specific duty cycles in FCML converters, but have not been able to use these methods to enable ZVS across the full range. This work uses dynamic level selection and variable frequency control to increase inductor current ripple at duty cycle ranges for which ZVS was previously unattainable. An experimental 5-level FCML prototype has been built using GaN devices on a single-sided PCB to demonstrate this control technique. We demonstrate 4-level and 5-level operation with ZVS at duty cycles that are not possible with 5-level operation alone, as well as a dynamic level transition with active capacitor voltage balancing.

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Section: Zero-voltage Switchingmentioning

confidence: 99%