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A distributed structure of step-up/step-down DC-DC converters using power saving techniques
(2014-01-01)
Eguchi, Kei
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Komatsu, Daisuke
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Pongswatd, Sawai
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Sasaki, Hirofumi
Improving power efficiency is one of the most important issues in DC-DC converters, because cooling of inefficient power converters is difficult and expensive. To reduce parasitic power losses caused by stray parasitic capacitances, a distributed structure of switched-capacitor (SC) step-up/step-down DC-DC converters using power saving techniques has been proposed in this paper. Unlike conventional converters, the proposed converter consisting of two converter blocks has two conversion processes: 1) charging and transferring process; and 2) charge reusing process. In each converter block, the charging and transferring process and the charge reusing process are repeated alternately, where the energy stored in parasitic capacitances is reused in the charge reusing process. Therefore, by alleviating parasitic losses, higher power efficiency can be achieved by the proposed converter. The results of the simulation program with integrated circuit emphasis(SPICE) simulation showed that more than 5% of the power efficiency was improved by the proposed converter when the output load is 10kΩ. © 2014 ISSN 1881-803X.
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A switched-capacitor-based serial DC-DC converter using clean energy power supplies
(2011-06-01)
Eguchi, Kei
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Pongswatd, Sawai
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Tirasesth, Kitti
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Sasaki, Hirofumi
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Oota, Ichirou
Aimed at mobile back-lighting applications, a switched-capacitor-based serial DC-DC converter is proposed in this paper. By using battery energy and solar energy, the proposed converter generates the stepped-up voltage to drive white LEDs. Unlike conventional multiple-input parallel converters, the output voltage of the proposed converter is generated by adding the output voltage of the SC-based circuit to the voltage of solar-cells. For this reason, the proposed converter can realize not only small hardware-cost but also wide input-range. Concretely, in comparison with the conventional parallel converter using 1.5 × step-up SC converters, the proposed converter can achieve 20% reduction of hardware cost and 16% extension of input range. The characteristics of the proposed converter are clarified by theoretical analyses. Furthermore, SPICE simulations and experiments show the validity of circuit design, where theoretical results correspond well with simulation results. For this reason, derived theoretical formulas can provide basic information to design serial SC DC-DC converters. The proposed converter will be useful as a LED driver circuit for display back-lighting. © 2011 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
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Oota, Ichirou
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Pongswatd, Sawai
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Julsereewong, Amphawan
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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
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Pongswatd, Sawai
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Tirasesth, Kitti
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Sasaki, Hirofumi
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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 3 ×/4× step-up AC-DC converters for RFID tags
(2010-12-01)
Pongswatd, Sawai
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Eguchi, Kei
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Sugimura, Tatsuya
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Watanabe, Toshiya
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Tirasesth, Kitti
In this paper, two types of step-up AC-DC conveners for RFID tags are proposed: the 3× step-up converter and the 4× step-up converter. The proposed converters consist of 2 charge-pump type AC-DC converters with opposite polarities. Unlike conventional converters, the proposed converters can offer higher output voltages. Furthermore, as for the 3× step-up converter, the circuit size of the proposed converter is almost the same as that of the Cockcroft-Walton type AC-DC converter. The characteristics of the proposed converters are clarified by theoretical analyses. Furthermore, the SPICE simulation and the experiment showed the validity of theoretical formulas and circuit design. ICIC International © 2010 ISSN 1881-803X.
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Design of a multiple-input SC DC-DC converter realizing long battery runtime
(2010-01-01)
Eguchi, Kei
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Pongswatd, Sawai
;
Julsereewong, Amphawan
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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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A multiple-input SC DC-DC converter with battery charge process
(2009-12-01)
Eguchi, Kei
;
Pongswatd, Sawai
;
Zhu, Hongbing
;
Tirasesth, Kitti
;
Sasaki, Hirofumi
Aimed at a backlighting application, a multiple-input switched-capacitor (SC) DC-DC converter with battery charge process is proposed in this paper. Unlike conventional SC power converters such as a Dickson-type converter, etc., the proposed converter drives some LEDs by converting energy from solar cells when solar cells offer enough energy. Furthermore, the proposed converter can charge a lithium battery when an output load is light. Hence, the proposed converter enables us to realize long battery runtime. 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 theoretical results agree well with SPICE simulation results. © 2009 IEEE.
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Design of a multiple-input parallel SC DC-DC converter and its efficiencyestimation method
(2009-09-01)
Eguchi, Kei
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Sugimura, Tatsuya
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Pongswatd, Sawai
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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.

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