Yazar "Shibata, Akira" seçeneğine göre listele

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    Design and analysis of an inductor-less cross-coupled voltage equalizer
    (Elsevier, 2020) Eguchi, Kei; Shibata, Akira; Do, Wanglok
    To equalize the imbalance in the state-of-charge (SoC) of lithium-ion cells, we propose a novel inductor-less cross-coupled voltage equalizer for series-connected batteries. Unlike existing symmetrical voltage equalizers using diode switches, the proposed voltage equalizer can balance the voltage of battery cells without a threshold voltage drop, because the diode-less design is realized by the cross-coupled structure. The performance of the proposed voltage equalizer is clarified by theoretical analysis, computer simulations, and breadboard-based experimental tests. The computer simulations and experiments reveal that the proposed voltage equalizer outperforms conventional inductor-less voltage equalizers.
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    Design of a multi-input single-output step-up ac/dc converter with bipolar structure
    (Elsevier, 2020) Eguchi, Kei; Nakashima, Daigo; Shibata, Akira
    For vibration energy harvesting, we propose a multiple-input single-output (MISO) step-up ac/dc converter with bipolar structure in this paper. Unlike existing ac/dc converters for vibration energy harvesting, the proposed ac/dc converter features a bipolar MISO topology that transforms several vibration inputs to provide a step-up voltage. Furthermore, the proposed topology enables inductor-less designs. To clarify the effectiveness of the proposed converter, some computer simulations as well as breadboard-based experimental tests are performed. In the performed simulations, the voltage gain of the proposed converter with 2 modules reaches about 3.5 at 20mW and the power efficiency is about 92% at 20mW when the ac input is 3.5V at 50Hz. Furthermore, the physical feasibility of the proposed topology is proved by the breadboard-based experimental tests.
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    Design of a Single Inductor LED Sink Driver Employing a Negative Hybrid Cockcroft-Walton/Dickson Multiplier
    (Ieee, 2021) Eguchi, Kei; Shibata, Akira; Ishibashi, Takaaki; Asadi, Farzin
    For a lithium-ion battery input, a new LED (Light-Emitting Diode) sink driver with a single inductor is presented in this paper. Unlike existing LED sink drivers, the proposed driver consists of a negative hybrid Cockcroft-Walton/Dickson multiplier and a buck-boost converter. By connecting the negative hybrid Cockcroft-Walton/Dickson multiplier to the buck-boost converter in series, the proposed topology can provide not only a higher voltage gain but also smaller component count and simpler switching control. To confirm the effectiveness of the proposed topology, theoretical analysis, computer simulations and experiments were performed regarding the simplest proposed driver realizing 8 times gain. Furthermore, the comparative analysis clarified that the proposed driver can provide higher power efficiency and smaller component counts than conventional drivers.
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    A hybrid LED sink driver using a nesting-type switched-inductor/switched-capacitor buck-boost converter
    (Elsevier, 2020) Eguchi, Kei; Bevrani, Hassan; Shafiee, Qobad; Shibata, Akira
    This paper presents a novel light emitting diode (LED) sink driver with a high voltage gain for LED-based lighting applications. Unlike conventional LED sink drivers, the proposed driver has the nested switched-inductor/switched capacitor (SI/SC) topology consisting of an SI buck-boost converter block and a nesting-type SC cell. Owing to the nested SI/SC topology, the proposed driver offers not only a high voltage gain but also a flexible controllability of the LED currents and transformer-less structure. The effectiveness of the proposed driver is justified by some simulation results in SPICE software environment and laboratory experimental tests. In the performed simulations, the proposed driver in comparison of conventional drivers improved almost 6% power efficiency when the output power was 500 mW. Furthermore, in the performed experiments, the feasibility of the proposed topology is confirmed by demonstrating a high voltage gain and the output controllability.
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    An LED driver connecting a nested-type SC converter and an SI buck-boost converter in parallel
    (IEEE, 2021) Eguchi, Kei; Shibata, Akira; Do, Wanglok
    For light emitting diode (LED) lighting applications, a novel hybrid LED driver with high voltage gains is proposed in this paper. Unlike existing LED sink drivers with series-connected structure, the proposed driver has the switched-inductor and switched capacitor (SISC) topology combining with an SI buck-boost converter and a nested-type SC converter in parallel. In the proposed topology, the LED cathode and anode are connected to the SI buck-boost converter and the nested-type SC converter, respectively. The characteristics of the proposed topology are analyzed theoretically. Furthermore, the validity of the proposed topology is confirmed by simulation program with integrated circuit emphasis (SPICE) simulations and breadboard experiments. The SPICE simulations and experiments reveal that the proposed driver can achieve high voltage gains and flexible controllability of outputs.
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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 step-down nesting-type ac–ac converter combined with voltage equalizers and switched-capacitor simple converters
    (Elsevier, 2019) Eguchi, Kei; Rubpongse, Ratanaubol; Shibata, Akira; Ishibashi, Takaaki
    In this paper, we present an inductor-less direct ac–ac converter with improved nesting-type topology. Unlike existing direct ac–ac converters, the proposed ac–ac converter combines a voltage equalizer and a switched-capacitor (SC) simple converter. Owing to the nesting conversion using two techniques, the proposed converter can provide a stepped-down voltage with small number of circuit components and high input power factor. To evaluate the performance of the proposed ac–ac converter, we compared the proposed ac–ac converter with existing inductor-less ac–ac converters, namely, flying capacitor type converter, symmetrical type converter, and traditional nesting-type converter, by theoretical analysis and simulation program with integrated circuit emphasis (SPICE) simulations. The SPICE simulations demonstrate that the proposed ac–ac converter outperforms existing inductor-less ac–ac? converters in the point of circuit size and input power factor, although the power efficiency of the proposed ac–ac converter is inferior to that of the symmetrical type converter. In the case of 1/4 voltage gain, the proposed ac–ac converter achieves about 82% power efficiency and 0.58 input power factor when the output power is 200 W.
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    Vibration Energy Harvesting Using a MISO Converter Employing Hybrid Cockcroft-Walton/Dickson Multipliers
    (Ieee, 2021) Eguchi, Kei; Shibata, Akira; Ishibashi, Takaaki; Asadi, Farzin
    Vibration energy harvesting is the concept to convert vibrations in an electrical power. For the vibration energy harvesting, a multiple-input single-output (MISO) ac/dc converter is proposed in this paper. Unlike existing converters for vibration energy conversion, the proposed converter achieves not only inductor-less structure but also high voltage gains by the stack topology using hybrid Cockcroft-Walton/Dickson multipliers (HCWDMs). Regarding the proposed MISO converter with two modules, the characteristics, such as power efficiency and output voltage, are clarified by theoretical analysis and simulation program with integrated circuit emphasis (SPICE) simulations. Furthermore, the validity of the proposed MISO topology is confirmed by breadboard tests.