Search results for: Robert C. N. Pilawa-Podgurski
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IEEE Transactions on Power Electronics > 2017 > 32 > 11 > 8570 - 8581
High-efficiency and compact single-phase inverters are desirable in many applications such as solar energy harvesting and electric vehicle chargers. This paper presents a 2-kW, 60-Hz, 450-V $ _{\text{DC}}$ -to-240-V $_{\text{AC}}$ power inverter, designed and tested subject to the specifications of the Google/IEEE Little Box Challenge. The inverter features a seven-level flying capacitor multilevel...
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Series-stacked server power delivery architectures have been proposed recently that can achieve much higher energy efficiency than conventional power delivery architectures. When servers are connected in series, differential power processing (DPP) converters can be used to regulate the server voltages when the servers are consuming different amount of currents. Server-to-bus DPP architecture has unique...
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Improving the power density of a power converter has many benefits for systems integration. Aspects such as thermal management, weight, conformation to mounting locations, and the footprint of the converter all become critical factors as systems continue to scale down in size. The flying-capacitor multilevel (FCML) converter topology is of interest because it has characteristics which contribute to...
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IEEE Transactions on Power Electronics > 2017 > 32 > 10 > 8071 - 8088
Current data center power delivery architectures consist of many cascaded power conversion stages, where the system-level power conversion efficiency is reduced each time the power is processed through the individual stages. Recently, series-stacked power delivery architectures have shown how the overall power conversion can be reduced through architectural changes, reporting above 99% system-level...
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Flying capacitor multilevel (FCML) converters are known to naturally balance the capacitor voltages through the use of phase-shifted pulse-width modulation. However, in practice, the capacitor voltages can still deviate and active balancing is often required. This work investigates the origins of the voltage imbalance in practical implementations of such converters and presents corresponding solutions...
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In single-phase power converters, passive power pulsation decoupling buffers (capacitors or LC circuits) have been widely adopted to reduce the twice-line frequency voltage and current ripple. With constant demands for higher power density and efficiency, active implementations of power pulsation buffers have always been an attractive prospect. While various implementations of active buffers have...
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IEEE Transactions on Power Electronics > 2017 > 32 > 6 > 4905 - 4924
A high-efficiency, high-power-density buffer architecture is proposed for power pulsation decoupling in power conversion between dc and single-phase ac. We present an active decoupling solution that yields improved efficiency and reduced circuit complexity compared to existing solutions. In the proposed architecture, the main energy storage capacitor is connected in series with an active buffer converter...
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A major challenge in the implementation of flying capacitor multi-level (FCML) converters is providing power to the gate drive circuits. A common method is to use isolated DC/DC converters, which are bulky, expensive and energy inefficient. This work discusses the design and implementation of an alternative gate drive power supply circuit, which utilizes three techniques termed cascaded bootstrap,...
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Series-stacking and differential power processing techniques have been proposed for data center power delivery applications in order to drastically increase power conversion efficiency in the server racks. Although above 99% system-level efficiency is achieved in the recent literature for steady-state and hot-swapped operation of the series-stacked servers, reported works required a well-regulated...
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This work presents a 1.3 kW, single phase, AC-DC converter with power factor correction based on a 7-level flying capacitor multilevel converter. The topology features a tradeoff of active circuit complexity for dramatic reduction on the magnetic component size, while maintaining a high efficiency. In this work, we demonstrate these features through theoretical analysis as well as a hardware prototype...
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Multilevel inverters such as the flying capacitor multilevel inverter (FCML) hold large potential benefit in applications where the size and weight of the inverter is constrained. This work presents the design and implementation of an inverter module which incorporates two individual 9-level FCML single-phase inverters in an interleaved design. Each inverter utilizes GaN FETs switching at 100 kHz,...
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Advances in transportation electrification and renewable energy processing have spurred a push towards higher power density. The flying capacitor multilevel converter topology shows promise in helping to further the trend of increasing power density. This paper describes the design, implementation, and verification of a testbed for the switching components in flying capacitor multilevel converters.
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IEEE Transactions on Power Electronics > 2017 > 32 > 1 > 715 - 722
This paper presents a technique for reducing the input current ripple on multiphase power converters that provide multiple heterogeneous power supply rails, such as those present in portable electronics and computers. Through asymmetric interleaving of individual phases, the input current ripple can be reduced compared to conventional interleaving. The technique is derived based on an analytic description...
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High power density converters in combination with cryogenic power systems could have a significant impact on the electrification of transportation systems as well as other energy conversion systems. In this study, the cryogenic temperature performance of an EPC gallium-nitride (GaN) power field-effect transistor was evaluated. At −195°C, an 85 % reduction in on-state resistance, and a 16 % increase...
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Recently, flying capacitor multi-level (FCML) converters with GaN power switches have received increased attention due to their potential to achieve high efficiency and high power density. However, one of the major challenges is providing power to the gate drive circuits, most of which are not ground referenced. The most common existing method utilizes isolated DC/DC converters, which are bulky, expensive...
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As demand for data centers grows with the expansion of cloud computing and storage, so too does the power consumption. In the search for more efficient and reliable power delivery to the servers that make up the data centers, researchers and industry have been investigating various power delivery options. Recently, series-stacked architectures have been proposed to address the efficiency limitation...
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Compact high step-up DC/DC conversion to provide high DC voltage has numerous applications. A conventional boost converter has many limitations with regard to achieving high voltage gain with high power density and efficiency. The flying-capacitor multilevel (FCML) converter topology has many inherent advantages to overcome many of the limitations of the conventional boost converter. In this work,...
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The goal of this work is to develop an analytical method to determine the optimum size of an active decoupling buffer in single phase DC-AC converters for the highest power density. The conventional method for active twice line frequency power pulsation decoupling is a structure commonly known as the full ripple port architecture. However, its high voltage stress and correspondingly large inductor...
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Multilevel topologies are an appealing method to achieve higher power density inverters for both mobile and stationary systems. This work discusses the design and development of a 13-level, flying capacitor multilevel (FCML) inverter. Operating from an 800 V bus, this inverter requires switches with a voltage blocking capability of less than 80 V. A 120 kHz switching frequency is enabled through the...
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Flying Capacitor Multi-Level (FCML) converters are attractive solutions for compact power conversion with a large step-down ratio. Many of these applications also need low-voltage auxiliary supplies to power control circuits or subsystems. Rather than build a separate converter that must be rated for the full input voltage, we propose to divert power from a naturally occurring, low-voltage node within...
