• Journal of Power Electronics
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• v.16 no.1
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• pp.84-92
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• 2016

Compared with Si MOSFETs, the GaN FET has many advantages in a wide band gap, high saturation drift velocity, high critical breakdown field, etc. This paper compares the electrical properties of GaN FETs and Si MOSFETs. The soft-switching condition and power loss analysis in a flyback-forward high gain DC/DC converter with a GaN FET is presented in detail. In addition, a comparison between GaN diodes and Si diodes is made. Finally, a 200W GaN FET based flyback-forward high gain DC/DC converter is established, and experimental results verify that the GaN FET is superior to the Si MOSFET in terms of switching characteristics and efficiency. They also show that the GaN diode is better than the Si diode when it comes to reverse recovery characteristics.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.54 no.4
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• pp.171-178
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• 2005

The proposed dual-output DC-DC converter that bases on flyback converter can obtain two output voltage with non-isolated main-output and isolated sub-output at the same time using single-winding high frequency transformer. It can solve problems in multi-winding converter that use one main-switch, and also control quality of isolated sub-output voltage can be improved by additional sub-switch to the second. For analysis and design of the proposed converter system, converters are classified as operation mode from switching state and are become modeling by applying state space averaging method. Steady-state characteristics and dynamic characteristics are analyzed by DC component and perturbation component from state space averaging model. From experiment converter, validity of analysis and design for the propose converter system is confirm.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.176-178
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• 2009

본 논문은 개선된 형태의 Forward-flyback 컨버터 회로를 제안하고, 회로 동작 및 정상 상태를 분석한다. 제안된 회로는 단일 스위치와 다중 출력 변압기를 사용하여 Forward-flyback 컨버터를 구성하며, 기존의 Forward-flyback 회로보다 적은 수의 다이오드를 사용하여 회로를 구동한다. 또한 Flyback 부분의 경우 Forward 부분 출력단의 LC필터를 사용할 수 있도록 구성하여 전압 출력 특성에서의 개선 역시 얻을 수 있다. 기생소자가 없는 경우에 대하여 회로의 동작 분석이 이루어 졌으며, 실험을 통해 이를 검증하였다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.9
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• pp.1341-1350
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• 2017

In this paper, a high reliability 30W DC-DC converter is designed considering military standard (MIL-STD) for military applications such as guided weapon and aircraft. The performances and specifications of conventional military grade DC-DC converter are practically analyzed. The requirements for military grade DC-DC converter are established in consideration of MIL-STD and analysis results of conventional product. Two isolated DC-DC converter, forward and fly-back converter, are designed and compared to determine topology. From experimental results under various operating conditions, the forward topology satisfied performances and specifications of MIL-STD for military DC-DC converter.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.1
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• pp.67-76
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• 2012

This paper proposes the aggregated modeling and control of integated boost-flyback converter (IBFC) for understanding of dynamics characteristic and designing of relevant controller. The basic concept of the aggregated modeling is to substitute the boost or the flyback converter with an equivalent current source. Since each converter with equivalent current source corresponds to the basic boost and flyback converters, the overall mathematical process is significantly simplified for the modeling. Afterwards each result is combined to construct the complete model of the IBFC, and the relevant controller is designed through the achieved small-signal model. Simulation and experimental results show excellent agreement with the theoretical expectations.

• Proceedings of the KIEE Conference
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• 1997.07f
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• pp.2252-2254
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• 1997

There are increasing demands on high accruacy DC power supplies for varous basic science reseach, such as accelerators and plasma applications, in Korea. In this paper, we present a study on 1kW class DC power supply using the parell operation method of the flyback converters. This DC power supply is equipped with a remote controller for computer interface. A Serial Communication Controller(SCC) is also developed for large scale scientific facilities which is capable of handling upto 32 power supplies simultaneously with one serial port in the host computer.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.3
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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.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.43-45
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• 2008

컨버터의 제어는 보통 아날로그 제어기를 기반으로 한다. 전용 아날로그 상용 IC들로 복잡한 회로의 장점을 극복하고 있고 이로 인해 기본성능을 수행하고 저가격화와 사용상의 편의를 얻을 수 있다. 그러나 이러한 장점은 디지털 제어기의 성능 개선과 가격의 하락으로 전용의 IC에 필적하는 파워 컨버터의 응용을 가능하게 만들었다. DC-DC 컨버터 내부 파라미터에 대한 모니터링이 가능하며, 아날로그 제어방식에서는 처음의 사양에 의해 고정된 출력전압을 얻었지만 디지털 제어 방식에서는 PC와 DC-DC 컨버터간 통신을 통하여 사용자가 원하는 임의의 전압을 얻어낼 수 있고 원격제어가 가능하다. 본 논문에서는 이와 같은 디지털 제어기의 장점과 실용성을 제시하고자 소신호 모델식을 기반으로 하여 디지털 모드 제어기를 설계하고, 이를 구현하기 위해 원칩 마이크로컨트롤러인 microchip사의 dsPIC30F2020을 사용하였다. 마이크로컨트롤러를 이용한 DC-DC 컨버터의 실용성을 검토하였다.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.743-746
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• 1999

In this paper, Flyback type DC/DC Switching Converter was designed, analyzed and fabricated. Worst Case Analysis(WCA) was peformed with Mathcad program and presents circuit simulation results for the in-rush current limit circuit. The value of the maximum OFF voltage stress is 131.84V, it is less than device specification(200V). The switching frequency(nominal case) and duty cycle at the wont case analysis are 75KHz and 34.62%, respectively. The maximum in-rush current presents 0.5A Those results show a possibility for use in space

• Proceedings of the IEEK Conference
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• 2000.06e
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• pp.9-12
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• 2000

This paper describes the modeling and experimental results of coreless printed circuit board (PCB) based transformer that can be used for power conversion at high frequency operation. The principle of using coreless PCB based transformer in 2MHz, 10W class ZVS Flyback DC-DC converter has been successfully demonstrated. The maximum power conversion efficiency is 79%. Even for high operating frequency, an efficiency greater than 70% can be obtained with under 1% regulation error.