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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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Power saving techniques to improve efficiency of a parallel-connected negative DC-DC converter
(2013-09-02)
Eguchi, Kei
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Pongswatd, Sawai
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Thepmanee, Teerawat
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Fujimoto, Kuniaki
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Sasaki, Hirofumi
A parallel-connected negative DC-DC converter using power saving techniques has been proposed in this paper. Unlike conventional negative converters, the proposed converter consists of four negative heap converters connected in parallel, where the power switch is driven by non-overlapped four-phase pulses cyclically. In two of the four negative heap converters, a part of the electric charge in parasitic capacitances is reused in each clock cycle. For this reason, the proposed converter can reduce energy loss than the conventional converters. The validity of the proposed technique was confirmed by simulation program with integrated circuit emphasis (SPICE) simulations and theoretical analysis. When the output load is 1 km, the proposed converter was able to improve power efficiency more than 11% compared to the conventional converter. © 2013 IEEE.
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A step-up/step-down SC DC-DC converter and its power saving techniques
(2013-09-02)
Eguchi, Kei
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Pongswatd, Sawai
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Thepmanee, Teerawat
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Fujimoto, Kuniaki
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Sasaki, Hirofumi
To improve power efficiency, a power saving technique for the ring-type DC-DC converter is proposed in this paper. By reusing a part of the electric charge in stray parasitic capacitances, the proposed converter can achieve higher power efficiency than the conventional converter. The results of the simulation program with integrated circuit emphasis (SPICE) simulation showed that more than 8% of the power efficiency was improved by the proposed converter when the output load is 10km. Furthermore, a handy equation to estimate the maximum power efficiency of the proposed converter is provided by theoretical analysis. © 2013 IEEE.
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Design of fractional conversion ratio SC DC-DC converters
(2013-09-02)
Pongswatd, Sawai
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Smerpituk, Krit
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Julsereewong, Prasit
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Eguchi, Kei
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Sasaki, Hirofumi
This paper presents the switched-capacitor (SC) circuit structure whose design conversion ratio is fraction multiple. The proposed converters can step up or step down the input voltage and bidirectional power flow by using dual converters connected. The 2x and 1/2x fraction conversion ratio is specified as a case study. The characteristics of the proposed converters are clarified by theoretical analyses. In addition, the simulation and experimental show the validity of circuit design, where theoretical results correspond well with simulation and experimental results. The proposed converters will be useful for battery charger, battery equalizer and dc power transfer. © 2013 IEEE.
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Interface circuit using operational conveyors for differential resistive sensors
(2013-09-02)
Julsereewong, Amphawan
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Julsereewong, Prasit
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Rungkhum, Tipparat
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Sasaki, Hirofumi
In this paper, a simple and accurate circuit for interfacing differential resistive sensors is presented. The realization method employs three operational conveyors as active elements to provide voltage output linearly proportional to sensing resistance change. The performance is confirmed through PSPICE simulation and experimental results. © 2013 IEEE.
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Design of multiple conversion ratio and bidirectional power flow by using dual SC DC-DC converters
(2013-03-28)
Pongswatd, Sawai
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Smerpituk, Krit
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Eguchi, Kei
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Sasaki, Hirofumi
This paper presents the simple design technique to implement dual SC DCDC converters that can convert input voltage step up or step down. The output of proposed converters is connected between individual converter output capacitors so that the output voltage can convert to multiple levels step up or step down and bidirectional power flow. The conversion ratio can be specified by simple circuit structure by connecting the capacitors in parallel or series. The circuits are designed by digital technique to on-off the switches for step up or step down conversion ratio 1x, 2x, 3x, jx, or 1x, 1/2x, 1/3x, 1/jx, respectively. The characteristics of the proposed converter are clarified by theoretical analyses. In addition, experimentation shows the validity of circuit design, where theoretical results correspond well with experimentation results. The proposed converter will be useful as a driver circuit for battery charger and power battery transfer between different level voltages. © 2013 ICIC International.
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Simple resistance-to-frequency converter with lead-wire-resistance compensation
(2013-03-28)
Julsereewong, Amphawan
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Petchmaneelumka, Wandee
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Rungkhum, Tipparat
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Yahara, Mitsutoshi
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Fujimoto, Kuniaki
This article presents a simple technique to realize a resistance-to-frequency converter for single resistive sensor-based remote measurements. The proposed realization method uses commercially available devices to generate output frequency, which is linearly proportional to sensing resistance deviation. Experimental results are shown that not only the good circuit operation but also the effective lead-wire-resistance compensation of the proposed technique can be obtained. © 2013 ICIC International.
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A dickson-type adder/subtractor dc-dc converter realizing step-up/step-down conversion
(2013-01-16)
Eguchi, Kei
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Julsereewong, Prasit
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Julsereewong, Amphawan
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Fujimoto, Kuniaki
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Sasaki, Hirofumi
In this paper, a Dickson-type adder/subtractor DC-DC converter realizing step-up/step-down conversion is proposed. Although the conventional Dickson converter cannot achieve step-up/step-down conversion, the proposed converter can provide not only the stepped-up voltage but also the stepped-down voltage by combining the battery energy and the clean energy. Moreover, the proposed converter can achieve many con-version ratios by utilizing hybrid inputs. Therefore, by choosing the optimal combination of conversion ratio, the proposed converter can alleviate the energy loss caused by the output regulation. To evaluate circuit properties, theoretical analyses, simulations and experiments were performed concerning a simple example of the proposed converter. Cir-cuit simulations and experiments showed the following results: (1) The circuit design is appropriate, because the step-up/step-down conversion was confirmed by the experimen-tal circuit. (2) The number of conversion ratios of the proposed converter is three times as large as that of the conventional three-stage ring-type converter. (3) The proposed converter can reduce more than 25% hardware cost than the conventional converter. (4) The derived theoretical formulas are useful to estimate the characteristics of the proposed converter, because the theoretical result corresponded well with the simulated result. © 2013 ICIC International.
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Design of a dual-input buck-boost converter for mobile back-lighting applications
(2012-04-01)
Eguchi, Kei
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Pongswatd, Sawai
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Julsereewong, Amphawan
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Oota, Ichirou
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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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Resistive sensor interface circuits using operational conveyor and operational amplifier
(2012-03-01)
Julsereewong, Amphawan
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Julsereewong, Prasit
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Rungkhum, Tipparat
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Sasaki, Hirofumi
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Isoguchi, Hiroshi
A simple technique based on commercially available devices to implement three interface circuits for both differential resistive sensors and single resistive sensors is presented in this article. Each proposed scheme uses an operational conveyor and an operational amplifier as active elements. Surpassing the previously reported circuits, the proposed circuits provide not only simpler structures but also higher accuracy. Performances of the proposed circuits are verified through computer simulations. © 2012 ICIC International.

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