Pongswatd, Sawai

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Pongswatd, Sawai
Alternative Name
Pongswatd, S.
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Email
sawai.po@kmitl.ac.th

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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 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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    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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    A white LED driver using a buck-boost converter
    (2010-01-01)
    Eguchi, Kei
    ;
    Pongswatd, Sawai
    ;
    Watanabe, Toshiya
    ;
    Pannil, Pittaya
    ;
    Tirasesth, Kitti
    For mobile backlighting applications, a white LED (WLED) driver using a buck-boost converter is proposed in this letter. Unlike conventional converters using boost converters, 2×/1.5× charge pumps, and so on, the proposed converter offers the negative stepped-down voltage to drive the LED's cathode only when the input voltage is insufficient to drive a 1× transfer mode. Furthermore, unlike the LED backlight using charge pumps, the proposed converter can adjust the output voltage by controlling the duty factor of the clock pulse. Thus, the proposed converter can realize high power efficiency. The validity of the proposed converter is confirmed by simulations and experiments. © 2010 Institute of Electrical Engineers of Japan.