• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.339-340
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• 2010

본 논문에서는 배터리를 이용한 직류전원 백업장치, HID 램프, 연료전지 시스템 등 고승압이 요구되나 절연이 필요 없는 응용을 위한 새로운 비절연 컨버터를 제안한다. 제안한 컨버터는 인터리빙이 적용되고 CCM에서 모든 스위치의 ZVS 턴온과 다이오드의 ZCS 턴온 턴오프가 가능하며, 최적의 소자 선택이 되도록 배압회로의 수를 적절히 선정하여 회로구성이 가능한 장점이 있다. 1kW 시작품으로 동작원리를 확인하였으며 최고효율 96.1%를 달성하였다.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.357-358
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• 2017

본 논문에서는 새로운 비절연형 3-레벨 고승압 부스트 컨버터를 제안한다. 제안한 컨버터는 기존의 출력 전압 밸런싱 기능을 가지는 3-레벨 고승압 부스트 컨버터에서 스위치와 인덕터의 위치를 변경하여 인터리브드 구조를 적용함으로써 출력전압 밸런싱 기능을 유지하면서 입력 전류의 리플 저감이 가능한 구조이다. 제안한 컨버터를 시뮬레이션을 통해서 검증하였다.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.197-198
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• 2012

본 논문에서는 배전압셀을 이용한 비절연 고승압 컨버터의 최적설계기법을 제안한다. 제안한 컨버터는 배전압셀 수를 적절히 선정하여 소자의 전압정격을 줄일 수 있으며 작은 듀티로도 높은 승압비를 얻을 수 있다. 제안한 컨버터의 ZVS 영역 분석, 주요 수동소자 설계를 통하여 모든 스위치의 ZVS 턴온을 달성시킬 수 있는 설계기법을 제시한다. 1kW급 시작품으로 제안한 설계기법의 타당성을 검증하였다.

• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.163-164
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• 2015

본 논문에서는 고승압비를 갖는 단일스위치 ZCS 병렬 공진 컨버터를 제안한다. 제안하는 컨버터는 단일스위치를 사용하여 구조가 간단하며 병렬 공진회로를 이용하여 고승압이 가능하다. 또한, 별도의 클램프 회로 없이 전 부하영역에서 스위치의 ZCS 턴온 및 턴오프와 다이오드의 ZCS 턴오프를 성취한다. 제안하는 컨버터는 250W 시작품을 제작하여 타당성을 검증하였다.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.42-43
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• 2015

본 논문은 출력 전류 리플이 없는 소프트 스위칭 승압 컨버터를 제안한다. 제안하는 컨버터는 결합 인덕터와 보조 커패시터와 보조 인덕터를 사용하여 스위치의 영전압 스위칭이 가능하도록 하여 스위칭 손실을 줄이고 출력 전류 리플을 제거하였다. 제안하는 회로의 동작원리를 설명하고, 시뮬레이션으로 확인한 후 60[W]급 하드웨어 시작품을 이용하여 검증하였다.

• Journal of the Korean Society for Railway
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• v.20 no.3
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• pp.329-338
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• 2017

A recent trend of technical development in auxiliary-power-supplies (APS) is to replace 60Hz low frequency transformers with isolated type dc/dc converters. This paper introduces the technical trend in APS structures and proposes a power converter circuit suitable for high-efficient and light-weight APS. By utilizing the resonant converter, which achieves ZCS, to reduce switching losses, various types of APS structures (1-stage and 2-stage) are reviewed, and they are verified by simulation. The full-bridge resonant LLC converter is designed with a 1-stage power converting structure; the resonant converter topology is designed with a 2-stage power converting structure that has a pre-regulator converter to compensate for the wide input voltage range. Both a step-down converter and a step-up converter are designed and compared for the pre-regulator in the 2-stage structure. Operational characteristics are compared with simulation results and loss analyses are presented to proposes appropriate system structure and topologies.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.5
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• pp.61-68
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• 2004

Recently, a fuel cell is remarkable for new generation system. The fuel cell is characterized by low voltage and high current. Therefor, for connecting to general load, it needs both a step up converter and an inverter. The proposed system consists of an isolated DC-DC converter to boost the fuel cell voltage to 380[Vdc] and a PWM inverter with LC filter to convert the dc voltage to single phase 220[Vac]. Also, bi-directional DC-DC converter for fuel cell generation system is composed to improve load response characteristic. In this paper, full bridge converter and the single phase inverter are designed and installed for fuel cell. Simulation and experiment verify that fuel cell generation system could be applied for the distributed generation.

• Journal of Electrical Engineering and Technology
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• v.10 no.3
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• pp.1075-1080
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• 2015

A hybrid electric vehicle (HEV) powertrain has more than one energy source including a high-voltage electric battery. However, for a high voltage electric battery, the average current is relatively low for a given power level. Introduced to increase the voltage of a HEV battery, a compact, high-efficiency boost converter, sometimes called a step-up converter, is a dc-dc converter with an output voltage greater than its input voltage. The inductor occupies more than 30% of the total converter volume making it difficult to get high power density. The inductor should have the characteristics of good thermal stability, low weight, low losses and low EMI. In this paper, Mega Flux^® was selected as the core material among potential core candidates. Different structured inductors with Mega Flux^® were fabricated to compare the performance between the conventional air cooled and proposed potting structure. The proposed inductor has reduced the weight by 75% from 8.8kg to 2.18kg and the power density was increased from 15.6W/cc to 56.4W/cc compared with conventional inductor. To optimize the performance of proposed inductor, the potting materials with various thermal conductivities were investigated. Silicone with alumina was chosen as potting materials due to the high thermo-stable properties. The proposed inductors used potting material with thermal conductivities of 0.7W/m·K, 1.0W/m·K and 1.6W/m·K to analyze the thermal performance. Simulations of the proposed inductor were fulfilled in terms of magnetic flux saturation, leakage flux and temperature rise. The temperature rise and power efficiency were measured with the 40kW boost converter. Experimental results show that the proposed inductor reached the temperature saturation of 107℃ in 20 minutes. On the other hand, the temperature of conventional inductor rose by 138℃ without saturation. And the effect of thermal conductivity was verified as the highest thermal conductivity of potting materials leads to the lowest temperature saturations.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.3
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• pp.209-218
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• 2011

In low voltage high current applications such as fuel cells the current-fed DC-DC converter which has small ripple current and turn ratio is more efficient. In the applications larger than 5kW the conventional single-phase current-fed converter based on full-bridge, half-bridge or push-pull topologies has high current burden of devices such as switches, and the selection and optimized design of the devices are not easy. In this paper a three-phase active-clamped current-fed push-pull DC-DC converter suitable for high power high step-up applications is proposed. The proposed converter has reduced current burden and is suitable for wide input voltage applications due to the use of whole duty cycle range. Design methods of main components including three-phase high frequency transformers are provided, and the validity and performance of the proposed converter are proved from a 5kW prototype.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.340-343
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• 2003

This paper presents characteristics of piezo transformer for AC-DC converter. This transformer uses transverse vibration mode and the origin of the structure was the ring dot type transformer. Because, the ring dot type transformers produce only step-up phenomenon, we made a multi-layered ring dot structure for a step-down output. The characteristics of the transformer were simulated by using the ANSYS. And frequency and voltage were measured by changing the load resistance and current. Frequencies that have the maximum output voltage and current were gradually increased, when the resistance were increased. Output voltage and current show a stable linearity according to the input voltage. The maximum output power was expected greater than 20 [W]. So, we expect that this type of multi-layered step-down ring dot transformer can be adopted for a small AC adapters.