• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.980-982
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• 2002

In this paper, we report the experimental results of the Forward-flyback DC-DC converter with current doubler and synchronous rectifier. The experimental converter, that has a output voltage 1.8V, output current 25A, maximum power of 45W, switching frequency of 290kHz and input voltage range of 36-75V, has been successfully implemented. As a result, in the entire voltage range the measured full load efficiency was above 82%, and the output voltage was regulated at 1.8V within ${\pm}$3% tolerance.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.137-138
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• 2013

능동 클램프 포워드 컨버터의 2차단에 전류 증배 정류회로를 사용할 경우 2차단에서의 도통 손실을 줄일 수 있다. 뿐만 아니라 상대적으로 큰 자화 인덕턴스와 작은 누설 인덕턴스를 이용하여 영전압 스위칭을 달성할 수 있으므로 회로 전체 동작 측면에서 바람직하다. 본 논문에서는 제안된 회로의 동작 설명과 함께 영전압 스위칭을 위한 조건을 다루었고 240W급 (12-V/20-A) 프로토타입 회로를 통해 분석 결과의 타당성을 검증하였다.

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.362-364
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• 2006

This paper presents a novel DC-DC Converter for 3 [kW] Fuel Cell System Residential Application. Phase shifted control is employed to regulate the output voltage and achieve soft switching. The transformer leakage inductance is utilized effectively to achieve zero voltage turn on for the power semiconductor switches. The current doubler rectifier has only one diode drop. The transformer secondary winding current rating is one half the load current. The overall effciency of the converter is improved.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.376-378
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• 1996

This paper presents a new PFC control method which replaces a fast line current measurement with a filtered load current measurement. Using the power balance relation between the input and the output of the boost converter. the input current can be described as the function of load current. Thus the PWM signal which effects the switching control of the boost converter is generated using the PFC input voltage, the PFC output voltage and the load current as input variables. By using a filter between the bridge rectifier and a dc-to-dc converter, the input voltage of the dc-to-dc converter is forced to always maintain above zero volt. Then the input current traces a sinewave in phase. The proposed scheme accomplishes a very high power factor and a low harmonic distortion of the line current. The validity of this scheme is demonstrated through simulation.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.355-357
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• 1996

With the wide-spread use of rectifier in electronic equipments, such problems as electronic components failures or equipment disorders have been occurred due to current harmonics. To overcome these problems, power factor correction circuits employing boost converter have been used. The switching stress of boost converter can be reduced by snubber circuit. Recently, research activities in snubber circuits have been directed to energy recovery snubber for improving the efficiency of power converter. In this study, a new passive snubber circuit which can recover trapped snubber energy without added control is proposed for boost converter The control of boost converter with proposed snubber is the same as the conventional one. In addition, the energy recovery circuit can be implemented with a few passive components. The circuit operation is confirmed through simulation.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.440-442
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• 1996

In this paper, characteristics of harmonic spectrum are studied for three phase PWM converter as the switching frequency variation and current control method changing. Especially, Differential Mode Noise which causes harmful effect on the other equipments is measured and compared with three phase diode rectifier.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1996.11a
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• pp.49-52
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• 1996

This paper reports the development of an electronic starter for fluorescent lamps, which is so smartly designed that can be used directly in existing installations. The key point of the design lies in the protection of lamp filaments by sufficient preheating and at the same time in the control of time constant for start-up circuit. The starter is consisted of three system parts: a rectifier pact, a switching part. and a gate control part. The characteristics of the developed electronic starter is compared with those of a conventional glow starter. As a result, blackening of lamps is almost reduced due to the stable and idealized start-up characteristics. And, furthermore, it is shown that its slaving time is shortened at about half the level of the conventional one and the starting power is also reduced.

• Proceedings of the KIEE Conference
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• 2011.07a
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• pp.1191-1192
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• 2011

We released new triple redundant digital excitation system with real time generator-turbine simulator. One of its great merits is the real time generator-turbine simulator when it was compared with the other products. If excitation system is tripped by unexpected faults, Maintenance man can do easily performance test of digital excitation control board, sequence relay and thyristor switching device of phase controlled rectifier without manufacturer's support. For the verification of this system, It was tested with an actual excitation system implemented on 5kVA M-G Set. After finishing the tests, the trial product will be installed and operated at a 500MW thermal power plant.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.670-673
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• 2000

This paper describes a new inverter active inverter between a photovoltaic(PV) array and single-phase utility that avoid the bulky input(60Hz) transformer on the AC side. The interface employs a pwm boost converter on the DC side followed by a pwm boost converter on the DC side followed by a pwm current-forced single-phase rectifier for injecting the power from the PV array into the mains. The current waveform at the AC side remains sinusoidal and exactly in phase at all time. The circuit also has the advantage of requiring fewer switching device than high-frequency link system. This paper describes modeling of PV array and new system topology. Simulation results on the performance of the connection are also presented.

• Proceedings of the KIPE Conference
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• 2001.12a
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• pp.171-174
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• 2001

This paper proposes a nonlinear impedance circuit composed by diodes and inductors or capacitors. This circuit needs no control circuits and switches, and the impedance .value is changed by the polarity of current or voltage. and this paper presents one of these applications to improve the input current of capacitor input diode rectifiers. The rectifier using the nonlinear impedance circuit id constructed with four diodes and four capacitors in addition to the conventional rectifiers, that is, it has eight diodes and five capacitors, including a DC link capacitor. It makes harmonic components of the input current reduce and the power factor improve. A circuit design method is shown by experimentation and confirmed simulation. It explained that compared conventional pulse width modulated (PWM) inverter with half pulse-width modulated (HPWM) inverter. Proposed HPWM inverter eliminated dead-time by lowering switching loss and holding over-shooting.