11 research outputs found

    Modeling and Efficiency Analysis of Multi-Phase Resonant Switched Capacitive Converters

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    International audienceThis paper presents an analytical method to evaluate pertinent data of the resonant capacitive switching converter especially the voltage gain and power efficiency. Instead of long transient simulation time, the proposed model uses frequency decomposition to speed-up computation. This method is valid for N-phase operation and extends the recently published studies on this promising topology outside zero-current/voltage switching conditions. Thanks to this tractable expression, we also reveal the intrinsic efficiencies over the voltage gain of 2-and 3-phase structures working at the resonant frequency in step-down operation. These results help to gain better understanding of multi-phase operation and encourage additional studies to use the full capability offered by the resonant switched capacitor converter especially for power on-chip integration. Keywords— DC-DC converter; switched-mode power supplies; resonant

    Comments on "Unified analysis of switched-capacitor resonant converters"

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    Author name used in this publication: Henry S. H. ChungAuthor name used in this publication: Chi K. Tse2006-2007 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

    Overview of the DC power conversion and distribution

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    Author name used in this publication: K. W. E. ChengPower Electronics Research Center, Department of Electrical EngineeringVersion of RecordPublishe

    Comments on "Design and analysis of switched-capacitor-based step-up resonant converters"

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    Author name used in this publication: Chi K. Tse2005-2006 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

    Hard-switched switched capacitor converter design

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    Switched capacitor (SC) converters are becoming quite popular for use in DC-DC power conversion. The concept of equivalent resistance in SC converters is frequently used to determine the conduction losses due to the load current. A variety of methodologies have been presented in the literature to predict the equivalent resistance in hard-switched SC converters. However, a majority of the methods described are difficult to apply to general SC converter topologies. Additionally, previous works have not considered all nonidealities in their analysis, such as switching losses or stray inductances. This work presents a generalized and easy to use model to determine the equivalent resistance of any high-order SC converter. The presented concepts are combined to derive a complete loss model for SC converters. The challenges of implementing output voltage regulation are addressed as well. A current-fed SC topology is presented in this work that overcomes the problems associated with voltage regulation. The new topology opens up a variety of additional operating modes, such as power sharing. These additional operating modes are explored as well. The presented concepts are verified using digital simulation tools and prototype converters. --Abstract, page iii

    On Energy Efficiency of Switched-Capacitor Converters

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    Power Electronics Intensive Energy Management Solutions for Hybrid Electric Vehicle Energy Storage Systems

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    Batteries, ultra capacitors (UCs), and fuel cells (FCs) are widely being proposed for electric and plug-in hybrid electric vehicles (EVs/PHEVs) as energy sources. The increasing popularity of EVs and PHEVs can be attributed to the savings in fuel costs, compared to conventional internal combustion engine (ICE) vehicles. EVs and PHEVs save energy due to the employment of reverse regenerating braking, during the deceleration cycle. This recuperated energy can be proficiently stored in batteries and/or ultra-capacitors. In general, the design of an intelligent control strategy for coordinated power distribution is a critical issue for ultra-capacitor supported PHEV energy storage systems. Implementation of several control methods have been presented in related literature, with the goal of improving battery life and overall vehicle efficiency. The control objectives vary with respect to vehicle velocity, power demand, and state-of-charge of both the batteries and ultra-capacitors. Hence, an optimal control strategy design is a critical aspect of an all-electric/plug-in hybrid electric vehicle operational characteristic. This thesis deals with the detailed analysis and novel hybrid controller design for bidirectional energy management solutions, using smart power electronic DC/DC converter solutions. More specifically, an intelligently designed novel digital control technique is presented for a 4-quadrant switched-capacitor Luo (4Q SC Luo) DC/DC converter. Features of voltage step-down, step-up, and bi-directional power flow are integrated into a single circuit. The novel control strategy enables simpler dynamics, compared to a standard buck converter with input filter, superior regulation capability, lower source current ripple, ease of control, and continuous input current waveform in buck and boost modes of operation. Furthermore, the proposed novel control strategy depicts high converter power density, high efficiency, and simple structure

    Switched capacitor converters:a new approach for high power applications

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    High-power, high-voltage and high voltage-conversion ratio DC-DC converters are an enabling technology for offshore DC grids of the future. These converters are required to interface between offshore wind farms and an offshore DC grid and a key design issue is the size and weight of the converter, which significantly impacts the cost of the associated off-shore platform. In addition to this application, some rural communities, particularly in Canada, Australia and South Africa,which are located far away from the electrical power generators, can take the advantages of this technology by tapping into existing HVDC transmission line using a high voltage-conversion ratio DC-DC converter. The work described in this thesis is an investigation as to how such DC-DC converters may be realised for these applications. First a review of existing DC-DC converters was carried out to assess their suitability for the target applications. A classification of DC-DC converters into Direct and Indirect converters was proposed in this work based on the manner in which the energy is transferred from the input to the output terminal of the converter. Direct DC-DC converters, particularly Switched Capacitor(SC) converters are more promising for high-voltage, high-power and high voltage-conversion ratio applications, since the converter can interface between the low-voltage and the high-voltage terminals using low-voltage and low-power power electronic modules. Existing SC topologies were examined to identify the most promising candidate circuits for the target applications. Four SC synthesis techniques were proposed in order to derive new SC circuits from existing topologies. A new 2-Leg Ladder, modular 2-Leg Ladder and bi-pole 2-Leg Ladder were devised, which had significant benefits in terms of size and weight when compared with existing circuits. A scaled power 1 kW converter was built in the laboratory in order to validate the analysis and compare the performance of the new 2-Leg ladder circuit against a conventional Ladder circuit, where it was shown that the new circuit had higher efficiency, smaller size and lower output voltage ripple than the Ladder converter

    Comments on ‘Unified analysis of switched-capacitor resonant converters

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    Abstract—The realization of line and load regulation in switchedcapacitor (SC)-based converters is discussed. A duty-cycle control is based on partial charging of the capacitors in the circuit. The influence on the efficiency is pointed out. The use of inductors in SC-based converters is discussed. Index Terms—Efficiency, switched-capacitor (SC) converter, voltage regulation. In the above paper [1], a way of realizing soft switching in switchedcapacitor (SC) converters by inserting small inductors in series with the switching capacitors has been discussed. Consequently, the proposed circuit behaves like a quasi-resonant converter, with turn-on and turn-off of the transistors under zero current switching. The extent of high-current spikes arising from charging the capacitors is limited, the EMI emission is reduced, and by fully charging the switching capacitors, the maximum available efficiency is attained. In this paper
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