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Author: search.filters.author.Pongswatd, SawaiSubject: search.filters.subject.Clean energy

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    Design of a dual-input buck-boost converter for mobile back-lighting applications
    (2012-04-01)
    Eguchi, Kei
    ;
    Pongswatd, Sawai
    ;
    Julsereewong, Amphawan
    ;
    Oota, Ichirou
    ;
    Terada, Shinya
    For mobile back-lighting applications, a dual-input white LED (WLED) driver using a bi-direction buck-boost converter is proposed in this paper. The proposed driver has two input terminals: battery input V <inf>in1</inf> and solar-cell input V <inf>in2</inf>. Unlike conventional drivers using boost converters, step-up SC DC-DC converters, and so on, the proposed converter drives the anode and the cathode of LEDs by using the solar-cell's voltage and the negative stepped-down voltage, respectively. Furthermore, by converting solar energy, the proposed driver can charge a rechargeable battery when the LED backlight is standby mode. Therefore, the proposed driver can achieve long battery lifetime. The validity of the proposed driver is confirmed by SPICE simulations and experiments. SPICE simulations show that the proposed driver can offer the sufficient voltage to drive LEDs by using solar energy and battery energy in spite of the variation in V <inf>in2</inf>. Furthermore, by employing a bi-direction buck-boost converter, the proposed driver provides us to realize long battery lifetime, because the battery charge process was confirmed by experiments. © 2012 ICIC International.
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    Synthesis and analysis of a dual-input parallel DC-DC converter designed by using switched capacitor techniques
    (2011-04-01)
    Eguchi, Kei
    ;
    Oota, Ichirou
    ;
    Pongswatd, Sawai
    ;
    Julsereewong, Amphawan
    ;
    Tirasesth, Kitti
    As a building block of mobile equipments, single-input switched-capacitor (SC) power converters have been used. However, the single-input converter is difficult to improve battery runtime by adjusting a voltage conversion ratio, because the ratio of the voltage conversion is predetermined by circuit structure. To solve this problem, a dual-input parallel-connected converter designed by the SC technique is proposed in this paper. Although the conventional single-input converter uses a lithium battery as an input energy source, the proposed dual-input converter uses not only a lithium battery but also solar cells. For the conventional SC converters, the energy conversion of clean energy is difficult, because the voltage of clean energy sources such as solar cells is sensitive to weather condition. To adopt the change in the voltage of clean energy input, the proposed converter provides the multi-state step-up conversion. By converting clean energy, the proposed converter realizes long battery runtime. Moreover, to design the multiple-input converter, the theoretical analysis to clarify circuit characteristics is required, because detailed analyses concerning multiple-input SC DC-DC converters have not been performed yet. Therefore, concerning circuit characteristics of the proposed dual-input converter, handy theoretical formulas are given in this paper. Through SPICE simulations, theoretical analyses and experiments, the validity of the proposed converter is confirmed. The theoretical results correspond well with SPICE simulation results. Therefore, the proposed analysis technique can be extended to the circuit design of other multiple-input SC DC-DC converters. Furthermore, the experimental results show that the proposed converter can generate the stepped-up voltage in spite of the change in the voltage of solar cells. Therefore, the proposed converter can realize long battery runtime. ICIC International © 2011.
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    Design of a dual-input SC DC-DC converter realizing negative outputs
    (2011-01-01)
    Eguchi, Kei
    ;
    Pongswatd, Sawai
    ;
    Tirasesth, Kitti
    ;
    Sasaki, Hirofumi
    ;
    Zhu, Hongbing
    Aimed at a back-lighting application, a dual-input switched-capacitor (SC) DC-DC converter with battery charge process is proposed in this paper. The proposed converter can realize -1/N× (N = 2,3,.) step-down conversion as well as (N + 1)/N× step-up conversion. By converting clean energy such as solar energy, the proposed dual-input converter not only drives light-emitting diodes (LEDs) but also recharges the battery, although conventional single-input converter only consumes battery energy. In the proposed converter, the -1/N× stepped-down voltage is generated to drive the LED's cathode when the input voltage is insufficient to drive a 1× transfer mode. Furthermore, unlike conventional converters, the battery is charged by the (N + 1)/N× stepped-up voltage when the LED back light is in standby mode. Hence, the proposed converter can realize long battery run time. The validity of circuit design is confirmed by theoretical analyses, simulations, and experiments. The derived theoretical formulas will be helpful to estimate circuit characteristics, because the theoretical results correspond well with the simulation program with integrated circuit emphasis (SPICE) simulation results. © 2011 Institute of Electrical Engineers of Japan.
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    Design of an inductor-based wled driver using clean energy power supplies
    (2010-10-01)
    Eguchi, Kei
    ;
    Pongswatd, Sawai
    ;
    Watanabe, Toshiya
    ;
    Zhu, Hongbing
    ;
    Tirasesth, Kitti
    For mobile back-lighting applications, a dual-input white LED (WLED) driver using a bi-direction buck-boost converter is proposed in this paper. The proposed driver has two input terminals: lithium battery input V<inf>in1</inf> and solar-cell input V<inf>in2</inf> Unlike conventional drivers using boost converters, step-up SC DC-DC converters, and so on, the proposed converter drives the anode and the cathode of LEDs by using the solar-cell's voltage and the negative stepped-down voltage, respectively. Furthermore, by converting solar energy, the proposed converter can charge the lithium battery when the LED back-light is off. Therefore, the proposed converter can realize long battery runtime. The validity of the proposed converter is confirmed by simulations and experiments. ICIC International © 2010 ISSN.
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    Design of a multiple-input SC DC-DC converter realizing long battery runtime
    (2010-01-01)
    Eguchi, Kei
    ;
    Pongswatd, Sawai
    ;
    Julsereewong, Amphawan
    ;
    Tirasesth, Kitti
    ;
    Sasaki, Hirofumi
    A multiple-input switched-capacitor DC-DC converter which can realize long battery runtime is proposed in this letter. Unlike conventional converters for a back-lighting application, the proposed converter drives some LEDs by converting energy from solar cells. Furthermore, the proposed converter can charge a lithium battery when an output load is light. The validity of circuit design is confirmed by theoretical analyses, simulations, and experiments. Copyright © 2010 The Institute of Electronics, Information and Communication Engineers.
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    Design of a multiple-input parallel SC DC-DC converter and its efficiencyestimation method
    (2009-09-01)
    Eguchi, Kei
    ;
    Sugimura, Tatsuya
    ;
    Pongswatd, Sawai
    ;
    Tirasesth, Kitti
    ;
    Sasaki, Hirofumi
    A multiple-input parallel SC (Switched Capacitor) DC-DC converter and itsefficiency estimation method are proposed in this paper. The proposed parallelconverter consists of two different kinds of converter blocks: 1. a 1.5×step-up SC DC-DC converter employing an input voltage from a lithium battery and2. a novel step-up converter employing an input voltage from clean energysupplies. Since the proposed step-up converter can achieve not only a largestep-up conversion ratio but also a wide input range, the proposed parallelconverter enables us to extend battery runtime, reduction of heat, and so on.Furthermore, concerning the proposed converter, theoretical analyses areperformed to estimate power efficiency. The proposed analysis technique can beextended to the circuit design of other SC DC-DC converters. The validity ofcircuit design and theoretical formulas is confirmed by SPICE simulations.ICIC International © 2009.