Yazar "Oota, Ichirou" seçeneğine göre listele

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    Design of a cross-connected charge pump for energy harvesting systems
    (IOP Publishing, 2017) Eguchi, Kei; Fujisaki, Haruka; Oota, Ichirou
    For energy harvesting systems, a novel charge pump with cross-connected structure is proposed in this paper. Owing to the cross-connected structure, the proposed charge pump can offer the output voltage to the output load at every phase. Furthermore, the proposed charge pump can reduce the number of circuit stages from the conventional charge pump. For above-mentioned reasons, the proposed charge pump can realize not only smaller internal resistance but also smaller output capacitance than the conventional charge pump. The theoretical analysis and simulation program with integrated circuit emphasis (SPICE) simulation demonstrate that the proposed charge pump outperforms the conventional charge pump in the point of power efficiency and circuit speed.
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    Design of a non-thermal food processing system utilizing wire discharge of dual electrodes in underwater
    (International Journal of Innovative Computing, Information and Control, 2018) Eguchi, Kei; Jaiwanglok, Anurak; Julsereewong, Amphawan; Abe, Hiroto; Oota, Ichirou
    To provide nutritious and fresh processed foods, non-thermal food processing technologies have been developed in recent years. Among others, a non-thermal food processing method utilizing underwater shockwaves has cost-effectiveness. In this method, the design of a high voltage multiplier and its discharging method are key factors for processing target foods effectively. This paper proposes a non-thermal food processing system utilizing wire discharge of dual electrodes in underwater. Unlike conventional non-thermal food processing systems, the proposed system has two pairs of electrodes with thin metal wires. Owing to the electric discharge using thin metal wires, the energy to generate underwater shockwaves can be decreased. For this reason, by only one electric discharge, both sides of the target food are crushed by the proposed technique. The experiments using a laboratory prototype clarified that the proposed method can soften the whole flesh of the target food effectively. Furthermore, by assuming a four-terminal model, an equivalent model of the high voltage multiplier was analyzed theoretically. Concerning the series-connected voltage multiplier, the design conditions were derived to estimate the characteristics such as output voltage and power efficiency.
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    Design of an ınductor-less direct ac-ac converter realizing 1/4x and 4x conversion
    (IOP Science, 2018) Eguchi, Kei; Kuwahara, K; Oota, Ichirou
    In this paper, an inductor-less direct AC-AC converter realizing 1/4x and 4x conversion is designed by using switched-capacitor (SC) techniques. Unlike conventional SC AC-AC converters, the proposed AC-AC converter is synthesized with two converter blocks. By converting an AC input twice by these converter blocks, the 1/4x step-down / 4x step-up conversion is achieved by the proposed converter. The proposed converter has a simple circuit configuration, where each converter block consists of only four bidirectional switches and two capacitors. Hence, the proposed converter can realize smaller circuit components and higher input power factor than conventional converters. The effectiveness of the proposed converter was confirmed by simulation program with integrated circuit emphasis (SPICE) simulations and theoretical analysis. The SPICE simulation revealed that the proposed converter outperforms the conventional AC-AC converter using a flying capacitor.
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    A multi-input cross-connected charge pump for mobile applications
    (IEEE, 2018) Eguchi, Kei; Ishibashi, Takaaki; Oota, Ichirou
    To develop efficient mobile application systems, a multi-input cross-connected charge pump is proposed in this paper. By combing ambient energy and battery energy, the proposed charge pump achieves a long working-life of the battery. Furthermore, unlike conventional charge pumps, the converter blocks are cross-connected in the proposed charge pump. Therefore, the proposed charge pump can realize smaller ripple noise than the traditional charge pump, because the output voltage is provided to an output load at every clock cycle. To clarify the characteristics of the proposed charge pump, we conducted theoretical analysis and simulation program with integrated circuit emphasis (SPICE) simulations. The theoretical analysis revealed the characteristics such as power efficiency and output voltage theoretically. Furthermore, SPICE simulation showed that the proposed charge pump can achieve efficient power efficiency and circuit speed.
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    Reduction of inrush current in a shockwave non-thermal food processing system using an exponential clock pulse generator
    (MDPI, 2020) Eguchi, Kei; Asadı, Farzin; Shibata, Akira; Abe, Hiroto; Oota, Ichirou
    Recently, shockwave food processing is drawing much attention as a low-cost non-thermal food process technique. In shockwave non-thermal food processing, underwater shockwaves are generated by a high voltage generator. Therefore, high inrush currents and high voltage stress on circuit components significantly reduce the reliability and life expectancy of the circuit. However, to the best of our knowledge, stress reduction techniques and their experimental verification have not been studied yet in the shockwave non-thermal food processing system. In this paper, we propose a stress reduction technique for the shockwave non-thermal food processing system and investigate the effectiveness of the proposed technique experimentally. To achieve high reliability and life expectancy, a new high voltage multiplier with an exponential clock pulse generator is proposed for the shockwave non-thermal food processing system. By slowing down the rate at which the capacitors charge in the high voltage multiplier, the exponential clock pulse generator significantly reduces the inrush current. Furthermore, to perform shockwave non-thermal food processing continuously at a lower voltage level, we present a new electrode with a reset mechanism for wire electric discharge (WED), where a square-shaped metal wire swings on a hinge in the proposed electrode. The proposed electrode enables not only shockwave generation at a lower voltage level but also continuous non-thermal food processing, because the square-shaped metal wire is not melted in the WED process. To confirm the validity of the proposed techniques, some experiments are performed regarding the laboratory prototype of the shockwave non-thermal food processing system. In the performed experiments, reduction of inrush currents and effective food processing are confirmed.
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    A small direct sc ac-ac converter with cascade topology
    (International Journal of Innovative Computing, Information and Control, 2018) Eguchi, Kei; Kuwahara, Kyoka; Ishibashi, Takaaki; Oota, Ichirou
    To realize a small inductor-less AC-AC converter, this paper presents a cascade direct AC-AC converter using switched-capacitor (SC) techniques. The proposed AC-AC converter has cascade topology, where converter blocks with the conversion ratio of 1/2 or 2 are connected in series. Owing to the cascade topology, multiple conversion is performed to realize high conversion ratio. Furthermore, each converter block consists of only two capacitors and four switches, because no flying capacitor is necessary to realize AC-AC conversion. By reducing the number of capacitors, the proposed converter can achieve smaller circuit components and higher input power factor than conventional converters. To clarify the effectiveness of the proposed AC-AC converter, characteristic evaluation was performed by using simulation program with integrated circuit emphasis (SPICE) simulations and theoretical analysis. In the conversion ratio of 1/4, the SPICE simulation result demonstrated that the proposed AC-AC converter can improve 8% power efficiency and 0.4 input power factor from the conventional direct AC-AC converter using flying capacitors.