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Yayın Design of a dual-input cross-connected charge pump utilizing scavenged energy(Elsevier, 2020) Eguchi, Kei; Kozono, Yutaka; Ishibashi, TakaakiThis paper presents a novel dual-input cross-connected charge pump utilizing scavenged energy. The proposed converter has two input sources: a battery input and a scavenged energy input. Unlike existing charge pumps, the proposed converter alleviates the energy consumed in a battery source by utilizing the scavenged energy. Therefore, the proposed converter can extend the lifetime of a battery source. Furthermore, the cross-connected structure offers not only higher voltage gain but also faster response speed than existing charge pumps. Through theoretical analysis and simulation program with integrated circuit emphasis (SPICE) simulation, the proposed converter demonstrates high power efficiency and high output voltage, where the proposed converter is compared with series–parallel converter, traditional charge pump, and Fibonacci converter. Concretely, about 90% power efficiency can be achieved by the proposed converter when the output power is 15 ?W, and the settling time is less than 19 ?S when the output load is 500 k . Furthermore, the feasibility of the proposed converter is confirmed by breadboard experiments, where the experimental circuit is built with commercially available ICs.Yayın 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, FarzinFor 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.Yayın Development of a simple direct switched-capacitor ac-ac converter using cascade connection(International Journal of Innovative Computing, Information and Control, 2018) Eguchi, Kei; Abe, Hiroto; Ishibashi, Takaaki; Sasaki, HirofumiIn this paper, we propose a simple direct AC-AC converter with cascade connection by using switched-capacitor (SC) techniques. The proposed AC-AC converter is synthesized with n (= 1, 2, . . ., N) converter blocks, where each converter block realizing 1/2× step-down conversion consists of only two capacitors and four switches. Unlike conventional SC converters, power conversion of the proposed converter is achieved without a flying capacitor. Hence, the proposed converter can reduce circuit size from the conventional converters. Furthermore, high conversion ratio is realized by connecting these converter blocks in series. In other words, multiple conversion is performed by cascade topology. To evaluate the effectiveness of the proposed converter, we conducted simulation program with integrated circuit emphasis (SPICE) simulations and theoretical analysis concerning power efficiency and input power factor. The evaluation demonstrated that the proposed converter can achieve better performance than the conventional converter using a flying capacitorYayın The development of a step-down switched-capacitor inverter without flying capacitors and full-bridge circuits(Elsevier, 2020) Eguchi, Kei; Abe, Hiroto; Ishibashi, TakaakiRecently, an inductor-less inverter attracts many researchers’ attention, because the inductor-less design can provide not only small size but also small electromagnetic interference (EMI). In this paper, we propose a novel step-down switched-capacitor (SC) inverter without flying capacitors. Unlike traditional single-phase inverters, the proposed single-phase inverter has the advantages, namely, inductor-less design, downsizing by omitting flying capacitors, no full-bridge circuit, and symmetrical topology. To achieve these features, the proposed SC inverter changes the connection order of series-connected capacitors alternately. By offering a simple circuit configuration, the proposed inverter can achieve not only small EMI but also small size and high power efficiency. Furthermore, by using pulse width modulation (PWM), the proposed inverter generates a sinusoidal output without flying capacitors and full-bridge circuits. The effectiveness of the proposed inverter is justified by comparing the proposed inverter with an existing single-phase SC inverter. The simulation program with integrated circuit emphasis (SPICE) simulations demonstrate that the proposed inverter outperforms the existing SC inverter in the points of power efficiency and component counts. Concretely, about 94% power efficiency can be achieved when the output power is 2kW. Furthermore, the proposed inverter can reduce two flying capacitors from the existing SC inverter.Yayın The development of an led lighting circuit using high gain buck-boost converters(IJEETC, 2019) Kuwahara, Kyoka; Ishibashi, Takaaki; Eguchi, Keihis paper presents an LED driver using high gain buck-boost converters. By combining a traditional buck-boost converter and a Switched-Capacitor (SC) DC-DC converter with flying capacitors, the proposed driver can achieve the following features: 1) High voltage gain realized by cascade connection, 2) controllability of conversion ratio owing to the hybrid topology, and 3) small volume with only one inductor. The characteristics of the proposed driver, such as output voltage and power efficiency, were investigated by Simulation Program with Integrated Circuit Emphasis (SPICE) simulations. Furthermore, the feasibility of the proposed driver was confirmed by experiments. The simulation and experiment show the effectiveness of the proposed driver.Yayın A multi-input cross-connected charge pump for mobile applications(IEEE, 2018) Eguchi, Kei; Ishibashi, Takaaki; Oota, IchirouTo 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.Yayın A small dc-ac inverter by using cross-connected charge pumps(IJEETC, 2019) Fujisaki, Haruka; Ishibashi, Takaaki; Eguchi, KeiThis paper introduces a Switched-Capacitor (SC) DC-AC inverter with cross-connected topology. By cross connecting two charge pump DC-DC converters, the proposed SC DC-AC inverter can achieve small size with a grounded input. Moreover, the cross-connected structure provides the reduction of internal resistance. Therefore, not only small size but also efficient energy conversion can be realized by the proposed inverter. The characteristics of the proposed inverter were investigated by theoretical analysis as well as SPICE (simulation program with integrated circuit emphasis) simulations. The proposed inverter demonstrates higher performances, such as small size and high-power efficiency, than traditional SC DC-AC converters.Yayın 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, IchirouTo 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.Yayın 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, TakaakiIn 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.Yayın Vibration Energy Harvesting Using a MISO Converter Employing Hybrid Cockcroft-Walton/Dickson Multipliers(Ieee, 2021) Eguchi, Kei; Shibata, Akira; Ishibashi, Takaaki; Asadi, FarzinVibration 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.
