• Journal of Power Electronics
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• 제10권5호
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• pp.461-467
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• 2010

This paper proposes a new soft-switched Sepic converter. It has low switching losses and low conduction losses due to its auxiliary communicated circuit and synchronous rectifier operation, respectively. Because of its positive and buck/boost-like DC voltage transfer function (M=D/(1-D)), the proposed converter is desirable for use in distributed power systems. The proposed converter has versions both with and without a transformer. The paper also suggests some design guidelines in terms of the power circuit and the control loop for the proposed converter.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 하계종합학술대회 논문집(5)
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• pp.103-106
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• 2001

In this paper, a soft switching half-bridge converter using secondary switches for output control and conduction loss reduction is proposed. The conventional half-bridge converter must be fixed on duty cycle for soft switching. The proposed converter was consisted of two added switches in series of the secondary rectifier diodes. The main switches with constant duty cycle are operated ZVS. The secondary switches are operated ZV-ZCS. Especially, the primary switches were fixed duty cycle for maximum voltage conversion ratio. Output of converter is controlled by duty cycle or phase-shifted time of secondary switches. The conduction loss of the proposed converter can be reduced by the secondary switches. The operation characteristic, analysis, simulation and experimental results of the proposed converter are presented.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 A
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• pp.559-561
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• 1994

In this paper a new AC/DC/AC converter in which Soft-Switched-Inductor Module is used, is proposed. This new converter adopts ZVS(Zero-Voltage-Switching) for main switches. Therefore the switching loss is minimized and high frequency operation is possible. Operations principles, short analyses and computer simulation results are presented.

• 전력전자학회논문지
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• 제18권3호
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• pp.263-269
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• 2013

The flyback converter has been applied widely in isolated DC/DC power converters because this converters employ a single MOSFET switch. The leakage inductance should be minimized for high efficiency of flyback converter. but in reality, it is very difficult. Namely, The Snubber circuit is essential to recover the leakage inductance stored energy when the switch is turn off. Flyback Converter typically operates in DCM mode and when switch is turn off in hard switching, this hard switching action results in a high power losses and switching stresses. In order to overcome these problems, a novel soft switching flyback converter using resonant snubber circuit is proposed in this paper. The resonant snubber circuit is composed of the transformer leakage inductance and a capacitor. To verify and confirm the proposed resonant snubber circuit, PSIM simulation and hardware prototype are implemented. Simulation and Experimental results indicate that the proposed resonant snubber circuit is effective.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2002년도 전력전자학술대회 논문집
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• pp.519-524
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• 2002

This paper presents a soft-switching technique of single-stage power conversion Matrix Converter of AC-AC converters. Conventional hard-switching method is limited to operate at low switching frequency due to increased switching loss. In this paper, by additional auxiliary switch circuits, it is shown that the main switch of the matrix converter operate as a zero-voltage switches, and the auxiliary switch operate as a zero current switch. Finally, the soft-switching technique with auxiliary switches is compared with conventional hard-switching technique, and Is analyzed by simulation.

• Journal of Power Electronics
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• 제15권6호
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• pp.1429-1437
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• 2015

A new parallel hybrid soft switching converter with low circulating current losses during the freewheeling state and a low output current ripple is presented in this paper. Two circuit modules are connected in parallel using the interleaved pulse-width modulation scheme to provide more power to the output load and to reduce the output current ripple. Each circuit module includes a three-level converter and a half-bridge converter sharing the same lagging-leg switches. A resonant capacitor is adopted on the primary side of the three-level converter to reduce the circulating current to zero in the freewheeling state. Thus, the high circulating current loss in conventional three-level converters is alleviated. A half-bridge converter is adopted to extend the ZVS range. Therefore, the lagging-leg switches can be turned on under zero voltage switching from light load to full load conditions. The secondary windings of the two converters are connected in series so that the rectified voltage is positive instead of zero during the freewheeling interval. Hence, the output inductance of the three-level converter can be reduced. The circuit configuration, operation principles and circuit characteristics are presented in detail. Experiments based on a 1920W prototype are provided to verify the effectiveness of the proposed converter.

• Journal of Electrical Engineering and Technology
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• 제13권6호
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• pp.2553-2560
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• 2018

In Korea, there are no instances where a hydrogen fuel cell power generation system has been used in a railway vehicle. Only the basic topology has been studied. In the previous study, conventional converters using a single switch were applied to the fuel cell power generation system. Therefore, current stress on the switch at converter on-off transitions would be large when controlling a large-capacity railway vehicle. In addition, since the input side ripple is also large, there is a problem with a shortening of the lifetime of both the fuel cell power generation system and the inductor. In this paper, a soft-switching transformer inductor boost converter for fuel cell powered railway vehicles was proposed. A technique to reduce both the switching current stress generated during on-off transitions, and the input ripple current flowing in the inductor were studied. The soft-switching TIB converter uses a transformer-type inductor to configure the entire circuit in an interleaved method, and reduces both input current ripple and the current ripple of the inductor and switch.

• 전력전자학회논문지
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• 제11권2호
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• pp.149-158
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• 2006

본 논문에서는 기존에 널리 사용되는 펄스폭 변조 (Pulse width modulation : PWM) 방식의 컨버터와 공진형 컨버터의 장점을 활용하고 단점을 보완할 수 있는 새로운 형태의 영전류 천이형 (Zero current transition : ZCT) 부우스트 컨버터를 제안한다. 제안한 회로는 기존의 PWM 부우스트 컨버터에 보조회로를 추가하여 주 스위치와 출력 다이오드의 스위칭 천이 순간에만 소프트 스위칭 조건을 제공함으로써 전체적인 동작은 기존의 부우스트 컨버터와 크게 차이가 없도록 하였다. 아울러, 보조회로에서의 부가적인 손실 역시 존재하지 않으므로 해서 고효율이 가능하게 된다. 본 논문에서는 제안한 회로의 동작을 분석하고 이를 바탕으로, 보조 회로의 소자값 결정에 도움이 되는 설계방식을 제공한다. 또한, 실험을 통하여 제안한 회로의 동작 원리 및 유용성을 검증하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.256-260
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• 2001

This paper presents boost and buck and buck-boost DC-DC converter circuit topologies of high-frequency soft switching transition PWM chopper type DC-DC high power converters with a single auxiliary passive resonant snubber. In the proposed boost power converter circuits operating under a principle of ZCS turn-on and ZVS turn-off commutation schemes, the capacitor and inductor in the auxiliary passive resonant circuit works as the loss less resonant snubber. In addition to this, the switching voltage and current peak stresses as well as EMI and RFI noises can be basically reduced by this single passive resonant snubber. Moreover, it is proved that converter circuit topologies with a passive resonant snubber are capable of solving some problems of the conventional hard switching PWM processing based on high-ferquency pulse modulation operation principle. The simulation results of this converter are discussed as compared with the experimental ones. The effectiveness of this power converter with a single passive resonant snubber is verified by the 5kW experimental breadboad set up.

• 전자공학회논문지SC
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• 제39권6호
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• pp.71-78
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• 2002

본 논문은 하프브릿지 컨버터와 포화자심으로 구성되는 간단한 회로에 의하여 소프트스위칭이 가능한 새로운 회로방식을 제안한다. 본 방식에서는 컨버터의 출력단자와 병렬로 각형의 자화특성을 갖는 포화인덕터를 결합하여 컨버터의 온시간과 인덕터의 불포화기간을 일치시킨다. 2개의 MOSFET 스위치에는 짧은 데드타임을 설정하여 그 기간에 자심의 포화인덕턴스와 스위치의 기생용량 성분에 의한 공진을 일으켜 소프트스위칭을 실현시킨다. 또한 전원 전압의 변동에 대처하기 위해 반도체와 선형인덕터를 가지고 자심의 동작을 모의한 새로운 실용회로를 제안한다. 본 논문에서는 포화자심의 모델링의 방법을 통하여 소프트스위칭의 원리를 해석하고 1.25kW의 컨버터에 대한 실험에 의해 그 타당성을 확인하였다.