• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1108-1113
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• 2017

In this paper, a bidirectional topology for quasi-Cuk dc/dc converter with capability of zero-voltage and zero-current-switching (ZVZCS) is proposed. The bidirectional quasi-Cuk (BQ-Cuk) converter has different voltage and current transfer ratio, reduced voltage stress on capacitor and capability of changing the output polarity in comparison with conventional bidirectional Cuk converter. In this paper, steady-state analysis of the quasi-Cuk converter with capability of ZVZCS in turn-on is presented. Then, critical inductances for transient from this operation to two new operations are calculated. Next, besides values designing of used elements, maximum and minimum value of their current and voltage are calculated. Finally, experimental results to verify the accuracy of the proposed converter in different operating modes are presented.

• ETRI Journal
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• v.44 no.4
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• pp.695-707
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• 2022

As for the insufficient nature of the fossil fuel resources, the renewable energies as alternative fuels are imperative and highly heeded. To deliver the required electric power to the industrial and domestic consumers from DC renewable energy sources like fuel cell (FC), the power converter operates as an adjustable interface device. This paper suggests a new boost structure to provide the required voltage with wide range gain for FC power source. The proposed structure based on the boost converter and the quazi network, the so-called SBQN, can effectively enhance the FC functionality against its high operational sensitivity to experience low current ripple and also propagate voltage and current with low stress across its semiconductors. Furthermore, the switching power losses have been decreased to make this structure more durable. A full operational analysis of the proposed SBQN and its advantages over the conventional and famous structures has been compared and explained. Furthermore, a prototype of the single-phase converter has been constructed and tested in the laboratory.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.7
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• pp.615-621
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• 2005

The electrical stability against surge stress of varistors, which are composed of Zn-Pr-Co-Cr-Y oxide system, were investigated at different sintering times. As sintering time increases, the varistor voltage and nonlinear exponent decreased in the range of $279.6\~179.1$ and $52.5\~24.9$, respectively. On the contrary, the leakage current and dielectric dissipation factor increased in the range of $1.2\~9.8\;{\mu}A$ and 0.0461\~0.0651 with increase of sintering time. For all varistors, the variation rates of V-I characteristic parameters against surge stress were more strongly affected in order of varistor voltage ${\rightarrow}nonlnear$ $exponent{\rightarrow}leakage$ current. On the whole, the electrical stability against surge stress increased with increasing sintering time. Conclusively, it is assumed that the varistors sintered for 2 h exhibited comparatively good characteristics, in view of overall characteristics.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.12
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• pp.939-943
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• 2011

In this paper, reliability of the two sandwiched MIM capacitors of $Al_2O_3-HfO_2-Al_2O_3$ (AHA) and $SiO_2-HfO_2-SiO_2$ (SHS) with hafnium-based dielectrics was analyzed using two kinds of voltage stress; DC and AC voltage stresses. Two MIM capacitors have high capacitance density (8.1 fF/${\mu}m^2$ and 5.2 fF/${\mu}m^2$) over the entire frequency range and low leakage current density of ~1 nA/$cm^2$ at room temperature and 1 V. The charge trapping in the dielectric shows that the relative variation of capacitance (${\Delta}C/C_0$) increases and the variation of voltage linearity (${\alpha}$/${\alpha}_0$) gradually decreases with stress-time under two types of voltage stress. It is also shown that DC voltage stress induced greater variation of capacitance density and voltage linearity than AC voltage stress.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.317-322
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• 2003

A novel three-level DC/DC converter (TLC)for high power applications operating from high input voltage Is proposed. Its switch voltage stress can be ensured to be only one-half of the Input voltage. Nevertheless, since all input voltage is applied to the transformer primary side, it has good turns ratio. The driving method of each module is same as those of the conventional phase-shifted ZVS full bridge PWM converter (PSFB) and the zero-voltage-switching (ZVS) of the leading leg are achieved exactly in the same manner as that of the PSFB. Moreover, its three-level operation can considerably reduce the current ripple through the output inductor and it has no problems of the DC-link voltage unbalance. Therefore, it features a low voltage stress, high efficiency, low EMI, high power density, and small sized filter. To confirm the operation, validity, and features of the proposed circuit, experimental results from a 200W, 600V/DC-48V/DC prototype are presented.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.5
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• pp.64-72
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• 2008

In the three phase four wire system, voltage unbalance caused by the unbalanced load operation, gives rise to current unbalance and de-rates by the increase of machine's loss and eventually enlarges power capacity and besides has a bad effect on power quality. Power capacitor has been used for the power factor correction of inductive load and the voltage stability of power system. And it uses instead of power side for magnetic excitation of induction motor. If voltage unbalance keeps up, it affects on voltage stress at the power capacitor and finally can be caused breakdown. In this paper, we analysed that voltage and current of power capacitor increases by the voltage unbalance factor and its stress is growing more and more.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.2215_2216
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• 2009

As a driving method of AC PDP, address display separated (ADS) scheme has been widely used. In ADS method, a picture of one frame is divided into eight subfields. In this paper, the effect of sustain voltage stress have been studied with several parameters. The experimental results show that sustain pulses in the previous subfield work as the stress to address discharge in the current subfield. It is also shown that as the voltage of the sustain period in the previous subfield increases, the address time lag in the current subfield decrease slightly.

• Journal of Power Electronics
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• v.18 no.2
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• pp.356-363
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• 2018

The combination of a buck converter and a forward converter can be considered to accomplish a high step-down non-isolated converter. To decrease the insufficient step-down ratio of a regular buck converter and to distribute switch voltage stress, a forward-integrated buck (FIB) converter is proposed in this paper. The proposed interleaved DC-DC converter provides an additional step-down gain with the help of a forward converter. In addition to its simple structure, the transformer flux reset problem is solved and an additional magnetic core reset winding is not required. The operational principle and an analysis of the proposed FIB converter are presented and verified by experimental results obtained with a 240 W, 150 V/24 V prototype.

• Proceedings of the IEEK Conference
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• 2002.06b
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• pp.17-20
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• 2002

This study has been investigated that traps generated inside of the oxide and at the oxide interfaces by the stress bias voltage. The traps are charged near the cathode with negative charge and charged near the anode with positive charge. The charge state of the traps can easily be changed by application of low voltages after the stress high voltage. These trap generation involve either electron impact ionization processes or high field generation processes. It determined to the relative traps locations inside the oxides ranges from 113.4A to 814A with capacitor areas of 10$^{-3}$ $\textrm{cm}^2$ The oxide charge state of traps generated by the stress high voltage contain either a positive or negative charge.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.88-90
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• 2006

Conventional sustaining driver (SD) of plasma display panel (PDP) employing auxiliary circuits on both side of a H-bridge inverter increases volume of PDP with cost. To solve this problem, a new single sustaining driver (SSD), which utilize only one side of auxiliary circuit is proposed. Moreover, using the voltage stress reduction technique (VSRT), the proposed SSD effectively reduces switch voltage stress with a simple structure.