Yazar "Do, Wanglok" seçeneğine göre listele

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    A cross-connected charge pump for energy harvesting applications
    (International Journal of Innovative Computing, Information and Control, 2019) Do, Wanglok; Fujisaki, Haruka; Eguchi, Kei
    Energy harvesting is a process of capturing, storing and converting external energy from ambient energy. The energy harvesting systems commonly use a switchedmode power supply (SMPS) to convert energy harvested from the ambient energy. Therefore, the power converter is an essential component in terms of developing efficient energy harvesting systems. Among SMPS, inductor-less converter can be a solution. This paper suggests a new topology of charge pumps by cross-connecting two of them for efficient energy harvesting systems. With the cross-connected structure, the new topology transfers a stepped-up output to the output capacitor and load in all operation periods. This operation way can improve the power efficiency of the proposed charge pump and also decrease the internal resistance and the output capacitor’s capacitance of it. The performance of the proposed charge pump is verified by comparing with two conventional charge pumps, which is based on simulation program with the integrated circuit emphasis (SPICE) simulations and theoretical analysis. Moreover, we demonstrated the feasibility of the proposed one through the experimental circuit built on a breadboard. The proposed charge pump helps develop efficient energy harvesting systems.
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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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    Experiment of a high voltage gain switched capacitor dc-dc converter based on a cross-connected fibonacci-type converter
    (Innovative Computing, Information and Control, 2019) Rubpongse, Ratanaubol; Do, Wanglok; Eguchi, Kei
    To make an efficient converter for energy harvesting systems, a high voltage gain cross-connected switched-capacitor (SC) DC-DC converter is presented in this paper. By using a cross-connected structure based on Fibonacci-type converters, the proposed converter can realize high voltage gain, where the voltage gain is expressed as a power of two. On the other hand, unlike traditional converters, stepped-up voltage is created in every clock cycle. By using the cross-connected structure, the proposed converter can reduce the size of output capacitor and output ripple noise. Therefore, the proposed converter can be compact in size. Experimentation revealed that the proposed converter can realize a high voltage gain, fast response speed, small output ripple noise, even at a small size.
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    Implementation of inductor-less 13-level inverter topology with reduced number of required component
    (Elsevier, 2020) Eguchi, Kei; Bevrani, Hassan; Shafiee, Qobad; Do, Wanglok
    This paper presents an inductor-less multilevel inverter (MLI) with a 13-level ac output. The proposed MLI consists of only 11 switches, 2 capacitors, and 2 input sources. Owing to the inductor-less symmetrical topology, the proposed MLI can reduce the component count in comparison of conventional MLIs. This leads to reduction of power loss and hardware cost. To clarify the effectiveness of the proposed MLI, the characteristic evaluation is given in detail. Some computer-based simulations in SPICE simulator environment as well as breadboard-based experimental tests are conducted concerning the proposed 13-level inverter. In the performed simulations, the power efficiency of the proposed MLI reaches about 85% and 88% at 1 kW in the case of a sinusoidal output and a triangular output, respectively. The proposed MLI improves power efficiency more than 2.5% comparing with the conventional K-type MLI when the output power is 1 kW. Furthermore, the experimental result proves the physical feasibility of the proposed topology by demonstrating the 13-level ac output. ?
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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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    A new analysis way of three-phase switched capacitor converter
    (World Scientific, 2019) Do, Wanglok; Eguchi, Kei
    The paper presents the theoretical analysis way of the switched capacitor converter (SCC). The main goal of this research is to suggest the analysis way of three-phase SCC. A common SCC operates by two phases; charging phase and discharging phase. Therefore, state-space averaging model or slow and fast switching limit (S-FSL) model has been suitable. Although the four-terminal equivalent model can cover all situation including three-phases cases, this model does not include the parameter of frequency and capacitance. Therefore, the four-terminal model has a weakness. In this situation, we selected the Fibonacci sequence SCC operated by three-phase as the target circuit, which topology has been proved to have higher efficiency, small size in the previous research. In the paper, we suggest the new analysis way of the three-phase SCC by combination of the four-terminal equivalent model and RC circuit model from each loop equation of the equivalent circuits of the SCC. By using the suggested way, it is possible to analyze the three-phase SCC, deriving the effect of the load, operation frequency and duty ratio variation. In order to verify the feasibility and the cogency of the suggested analysis way, comparative analysis is implemented by SPICE simulations. The error in the load regulation between the suggested way and the simulation result is negligible. Through this result, we establish the foundation of the analysis of the three-phase SCC.
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    A Stacked cockcroft-walton high voltage multiplier for 220 V at 50 Hz inputs
    (IEEE, 2021) Eguchi, Kei; Nakashima, Daigo; Do, Wanglok
    For non-thermal food processing utilizing underwater shockwaves, this paper presents a stacked Cockcroft-Walton voltage multiplier (CWVM). By converting 220 V ac and 50 Hz inputs, the proposed multiplier generates more than 3.5 kV dc output. To generate 3.5 kV at high speed, conventional multipliers connect some voltage multipliers in series. Hence, the conventional multipliers suffer from high voltage stress on circuit components. To solve this problem, we design a novel high voltage multiplier by employing stack topology. By stacking CWVMs, the proposed multiplier can achieve high voltage gains with low voltage stress. The characteristics of the proposed multiplier are demonstrated by theoretical analysis and simulation program with integrated circuit emphasis (SPICE) simulations. The SPICE simulations demonstrated that the proposed multiplier can achieve high gains as well as high speed operation and low voltage stress.
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    A Stacked Cockcroft-Walton High Voltage Multiplier for 220 V at 50 Hz Inputs
    (Ieee, 2021) Eguchi, Kei; Nakashima, Daigo; Do, Wanglok; Asadi, Farzin
    For non-thermal food processing utilizing underwater shockwaves, this paper presents a stacked Cockcroft-Walton voltage multiplier (CWVM). By converting 220 V ac and 50 Hz inputs, the proposed multiplier generates more than 3.5 kV dc output. To generate 3.5 kV at high speed, conventional multipliers connect some voltage multipliers in series. Hence, the conventional multipliers suffer from high voltage stress on circuit components. To solve this problem, we design a novel high voltage multiplier by employing stack topology. By stacking CWVMs, the proposed multiplier can achieve high voltage gains with low voltage stress. The characteristics of the proposed multiplier are demonstrated by theoretical analysis and simulation program with integrated circuit emphasis (SPICE) simulations. The SPICE simulations demonstrated that the proposed multiplier can achieve high gains as well as high speed operation and low voltage stress.
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    Thermoelectric energy harvesting using a single inductor DC/DC converter employing a negative Dickson multiplier
    (Elsevier, 2021) Eguchi, Kei; Nakashima, Daigo; Do, Wanglok; İshibashi, Takaaki; Asadi, Farzin
    Thermoelectric energy harvesting is the concept to convert thermal energies in an electric power. For the thermoelectric energy harvesting, a single inductor dc/dc converter using a negative Dickson multiplier is presented in this research. By merging a negative Dickson multiplier into a buck-boost converter, high voltage gain, flexible output tuning, and small power loss are attained by the proposed topology. Moreover, fewer number of switch drivers and simpler switching control are achieved than conventional hybrid boost converters, because the proposed converter with a single inductor has only one transistor switch. Through theoretical analysis, a characteristic investigation is performed regarding an example of the proposed converter with 6 diodes, 6 capacitors, a MOS-switch and an inductor, where simple formulas to clarify the converter characteristics are derived by utilizing a four-port model. Furthermore, we justify the efficacy of the proposed topology by performing the comparison among hybrid dc/dc converters with a single inductor, namely, the hybrid converter using a voltage doubler and the hybrid converter using a Cockcroft–Walton multiplier. In the comparison, computer simulations using a SPICE simulator reveal that the proposed converter achieve the best performance the compared converters. Specifically, the efficiency of the proposed converter with three multiplier stages reaches about 84% when the voltage gain is 6 and the output power is 2 W. Furthermore, some experiments verify the possibility of realization by assembling the proposed converter with three multiplier stages on a printed circuit board (PCB). In laboratory tests, maximum power efficiency of 85% and the maximum voltage gain of 6.4 are measured.