• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.2
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• pp.54-63
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• 2007

Recently, a fuel cell with low voltage and high current output characteristics is remarkable for new generation system. It needs both a DC-DC step-up converter and DC-AC inverter to be used in fuel cell generation system. Therefor, this paper, consists of an isolated DC-DC converter to boost the fuel cell voltage $380[V_{DC}]$ and a PWM inverter with LC filter to convent the DC voltage to single-phase $220[V_{AC}]$. Expressly, a tapped inductor filter with freewheeling diode is newly implemented in the output filter of the proposed high frequency isolated ZVZCS PWM DC-DC converter to suppress circulating current under the wide output voltage regulation range, thus to eliminate the switching and transformer turn-on/off over-short voltage or transient phenomena. Besides the efficiency of 93-97[%]is obtained over the wide output voltage regulation ranges and load variations.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.1
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• pp.64-73
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• 2001

This paper presents a Zero Voltage and Zero Current Switching (ZVZCS) 3-Level DC/DC converter. This converter overcomes the drawbacks presented by the conventional Zero Voltage Switching(ZVS) 3-Level converter, such as high circulating energy, severe parastic ringing on the rectifier diodes, and limited ZVS load range for the inner switches. The converter presented in this paper uses a phase shift control with a flying capacitor in the primary side to achieve ZVS for the outer switches. Additionally, the converter uses an energy recovery snubber to reset the primary current during the free-wheeling stage to achieve ZCS for the inner switches. The proposed converters are analyzed and verified on 6kW, 39kHz experimental prototype.

• Proceedings of the KSR Conference
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• 2003.10c
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• pp.646-652
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• 2003

AS a main Power Supply of the Railroad Vehicles, a three-Level ZVZCS DC/DC Converter is proposed in this paper. The proposed three-Level DC/DC Converter achieves zero voltage and zero current switching for the main switches. Its attribute is that the voltage across the switches is half the value of the input voltage. Also. using a diode and secondary side of the transformer, and simple auxiliary circuits it achieves zero current switching of the auxiliary switches. The principle operation and simulation results are included.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.266-269
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• 2000

This paper presents a novel single-stage unity power factor converter which features the reduced switching losses by zero-voltage switching and zero-current switching (ZVZCS). Hence the turn-on and turn-off losses of switches are sufficiently reduced. And the reduced conduction losses are achieved by the elimination of one leg of front-end rectifier. And low on-resistance MOSFETs (Synchronous Rectifier) are used in the rectifier at the secondary side of high frequency transformer instead of diodes. Theoretical analysis simulated results of a AC to DC 150W(5V, 30A) converter are presented.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.213-215
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• 2008

본 논문에서는 수 kW급 이상의 연료전지 응용을 위한 고효율 전압원 3상 DC-DC 컨버터를 제안한다. 제안한 컨버터는 전압원 컨버터임에도 작은 턴비(기존 풀브리지의 1/2 이하)를 가지며 입 출력 전류 리플이 작다. 또한 클램프 회로의 동작으로 다이오드 서지전압 제거는 물론 저전압측 순환전류를 큰 폭으로 감소시켜 스위치의 도통손실과 변압기의 동손을 최소화하였고 전 부하영역에서 하측 스위치의 ZVZCS를 성취하여 스위칭 손실을 최소화 하였다. 또한 유효 듀티를 증가시켜 누설인덕턴스에 의한 듀티 손실을 보상하였다. 본 논문에서는 제안하는 컨버터의 동작원리를 서술하고 1.5kW Prototype을 제작하여 실험을 통해 본 방식의 타당성을 검증하였다.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.10
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• pp.683-692
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• 2000

A new primary-side-assisted zero-voltage and zero-current switching full bridge DC-DC converter with transformer isolation is proposed. The auxiliary circuit adopted to assist ZCS for the leading leg is composed of only one small transformer and two diodes. It has a simple and robust structure, and load current control capability even in short circuit conditions. Possibility of magnetic saturation due to asymmetricity of circuits or transient phenomena is greatly reduced, which is a very attractive feature in DC/DC converters with transformer isolation. The power rating of the auxiliary transformer is about 10% of that of the main transformer. Operation of a 12.5KW prototype designed for welding application was verified by experiments.

• Journal of Power Electronics
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• v.2 no.4
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• pp.278-287
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• 2002

A novel zero-voltage and zero-current switching PWM DC-DC converter with lowered conduction losses is presented in this paper. A new double two-switch forward high frequency transformer type soft-switching converter topology is developed to minimize circulating currents occurs during freewheeling period. This converter has advantages as less number of the components, simple control principle under constant operation frequency, free of transformer Imbalance effect. The principle of operation is illustrated with steady-state analysis. Moreover, the effectiveness of the proposed converter topology is verified by implementation of a 500w-100kHz breadboard using IGBTs.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.548-551
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• 2000

The battery charger for high speed trail car is very important power source for the purpose of safty and system stability. it provides control power of VVVF, CVCF, DC/DC converter and inverter for traction motor. This paper included power circuit of the ZVZCS type battery charger for high speed trail car and battery included power circuit of the ZVZCS type battery charger for high speed trail car and inverter for traction motor. This paper included power circuit of the ZVZCS type battery charger for high speed trail car an battery charging algorithm. Also the optimum parallel operation of 50Kw battery charger for high speed trail car and charging control method of Ni-Cd battery illustrates validity and effectiveness through the experiments.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.334-335
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• 2011

본 논문에서는 절연이 요구되지 않는 고승압 응용에 적합한 비절연 고승압 컨버터를 제안한다. 제안하는 컨버터는 기존의 부스트 컨버터에 비해 약 2배의 승압비를 가지며 스위치와 다이오드의 전압 정격이 1/2로 감소되어 RDS(ON)이 작은 소자를 선정할 수 있다. 또한 스위치의 ZVS 턴온과 ZCS 턴오프가 성취되며 보조 회로의 공진을 이용함으로서 기존 방식에 비해 스위치의 턴오프 전류가 낮아져 스위칭 손실이 감소한다. 2kW의 시작품을 제작하여 제안하는 컨버터의 타당성을 검증하였다.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.2204-2206
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• 1997

A novel zero voltage and zero current switching (ZVZCS) full bridge (FB) PWM converter with a low output current ripple is proposed. The proposed circuit improve the demerits of the previously presented ZVBCS-FB-PWM converters[5-8] such as use of lossy components or additional active switches. A simple auxiliary circuit which includes neither lossy components nor active switches provides ZVZCS conditions to primary switches, ZVS for leading-leg switches and ZCS for lagging-leg switches. In addition, this proposed circuit reduces a output current ripple considerably. Many advantages including simple circuit topology, high efficiency, low cost and low current ripple make the new converter attractive far high power (> 1kW) applications.