• Proceedings of the KIPE Conference
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• 2016.11a
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• pp.5-6
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• 2016

This paper introduces a high efficiency bidirectional resonant converter using an additional LC auxiliary circuit for dcdistribution applications. The LC auxiliary circuit operates as a variable inductor and the additional LC circuit helps to increase the effective magnetizing inductance, thereby reducing the turn-off and primary circulating current. A 5 kW bidirectional converter for dc-distribution system is implemented to verify the validity of the proposed method. The experimental results show the high efficiency characteristics of the proposed converter over the wide range of load in both direction of power flow. The maximum efficiency of the proposed system was 98.1 % at 3 kW.

• Steel and Composite Structures
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• v.32 no.4
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• pp.521-536
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• 2019

The mechanical response of concrete-filled steel tubular (CFST) columns subjected to pure compression or uniaxial bending was studied in depth over the last decades. However, the available research results on CFST columns under biaxial bending are still scarce and the lack of experimental tests for this loading situation is evident. At the same time, the design provisions in Eurocode 4 Part 1.1 for verifying the stability of CFST columns under biaxial bending make use of a simplistic interaction curve, which needs to be revised. This paper presents the outcome of a numerical investigation on slender CFST columns subjected to biaxial bending. Eccentricities differing in minor and major axis, as well as varying end moment ratios are considered in the numerical model. A parametric study is conducted for assessing the current design guidelines of EN1994-1-1. Different aspect ratios, member slenderness, reinforcement ratios and load eccentricities are studied, covering both constant and variable bending moment distribution. The numerical results are subsequently compared to the design provisions of EN1994-1- 1, showing that the current interaction equation results overly conservative. An alternative interaction equation is developed by the authors, leading to a more accurate yet conservative proposal.

• Journal of IKEEE
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• v.22 no.1
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• pp.174-179
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• 2018

In this paper, design of high-efficiency DC-DC converter is presented for low-power PMIC (power management integrated circuit). As PMIC technologies for IoT and wearable devices have been continuously improved, high-efficiency energy harvesting schemes should be essential. Since the supply voltage resulting from energy harvesting is low and widely variable, design techniques to achieve high efficiency over a wide input voltage range are required. To obtain a constant switching frequency for wide input voltage range, frequency compensation circuit using supply-voltage variation sensing circuit is included. In order to obtain high efficiency performance at very low-power condition, accurate burst-mode control circuit was adopted to control switching operations. In the proposed DC-DC buck converter, output voltage is set to be 0.9V at the input voltage of 0.95~3.3V and maximum measured efficiency is up to 78% for the load current of 180uA.