• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.2
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• pp.42-48
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• 2005

A DC-DC converter is being widely used for various household appliances and for industry applications. The DC-CC converter is powered from single battery, and the voltage is varied according to the purpose. In the vehicle, various accessories whose electric power is different are being un4 Thus, plural number of DC-DC converter should be provided, so these situations bring complicated circuits, and accordingly, higher cost. Under such backgrounds, in this paper, we propose a novel buck-boost chopper circuit with simply configuration which can supply to two or more different output loads. The propose chewer circuit can control output voltages by controlling duty ratio by using typically two switching devices, which is composed by single boost-switch and single buck-switch. The output voltage can be controlled widely. A few modified circuits developed from the fundamental circuit are represented including the general multi-load circuit. And all this merits and appropriateness was proved by computer simulation and experience.

• Proceedings of the KIPE Conference
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• 2009.11a
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• pp.78-80
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• 2009

최근 화석에너지원의 고갈과 고유가 및 지구 온난화 방지를 위해 국가별로 이산화탄소 배출량을 규제하기 시작하면서 신재생 에너지의 사용에 대한 관심이 높아지고 있다. 그 중 연료전지가 한 부분을 차지하고 있으며, 연료전지는 친환경적이고 효율적인 에너지원으로서 근 미래의 새로운 대체 에너지로서 각광 받으며 여러 분야의 전기장치로 사용될 수 있다. 연료전지는 낮은 출력전압과 높은 출력전류를 갖는 특징이 있으며, 부하에 따라 출력전압이 변화하는 특성이 있기 때문에 연료전지의 사용을 위해서는 다양한 부하조건에서 연료전지와 연동된 승압 또는 강압형 컨버터의 제작이 반드시 필요하다. 본 논문에서는 DSP를 이용하여 컨버터의 디지털 제어가 가능하며, 고정 시비율로 동작하는 LLC 공진형 컨버터를 이용한 2kW급 연료전지용 양방향 컨버터를 제안하였다. 제안한 컨버터는 양방향으로 동작하며, 에너지 저장 및 재사용을 목적으로 하고, 출력은 24V 배터리가 된다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.5 no.2
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• pp.309-313
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• 2001

In this paper, a multifunctional three-phase electronic step-down transformer with output voltage stabilization characteristics is presented for custom power applications. The proposed electronic transformer has some advantages and features as follows: 1) It has 40 % weights lighter than that of commercial magnetic transformer, 2) It has output voltage stabilization characteristic with regulated output voltage over input variations, 3) It cab be operated as circuit breaker in the case of emergency, 4) It can be operated with so called soft starting function. Moreover, the electronic transformer may have stand-by power cutoff function and act as distortion compensator. This paper show the circuit diagram and present its features through various PSPICE simulations.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.97-98
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• 2012

본 논문에서는 친환경 자동차용 양방향 절연형 저전압 직류변환장치(Low voltage DC-DC converter, LDC)를 제안한다. 제안한 컨버터는 직렬 공진형 컨버터를 이용한 2단 방식으로 비절연 컨버터가 전압 및 양방향 제어를 하며 절연부는 고정듀티와 고정주파수로 동작시켜 전 부하영역에서 ZCS 턴온 및 턴오프가 가능한 장점을 갖는다. 또한 양방향 전압제어가 가능한 제어 전략을 제안하였다. 5 kW급 시작품으로 제안한 방식의 타당성을 검증하였으며 강압모드시 최고효율 95.13 %, 승압모드시 최고효율 95.08 %를 달성하였다.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.93-94
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• 2012

본 논문에서는 효율 향상과 부피저감을 위한 전기자동차용 3.7kW급 비절연형 탑재형 충전기를 소개하고, 강압영역에서의 성능 개선을 위한 알고리즘을 제안한다. 제안한 충전기 토폴로지는 Cascaded Buck-Boost 컨버터로 두개의 Pole로 구성되어 있으며, 강압영역에서 제어는 기존의 제어 방식과 다르게 두 개의 Pole을 동시에 제어하지 않고 각각을 제어하여 인덕터의 전류 리플을 저감하여 충전효율을 증가 시킬 수 있다. 제안한 시스템 및 알고리즘은 실험을 통해 검증한다.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.139-140
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• 2013

본 논문에서는 철도차량용 25kW급 배터리 충전기 개발에 대해 설명한다. 열차 판넬 및 제어용 전원으로 사용되는 배터리 전원을 사용한다. 이를 상시 충전하기 위한 충전기는 기존에 보조전원장치의 3상 380V를 받아 강압 변압기를 사용하여 다이오드 정류 혹은 싸이리스터를 사용하였다. 하지만, 기존방식은 강압 변압기가 60Hz의 낮은 주파수로 인하여 사이즈 및 중량 증대를 유발 한다. 이에 본 논문에서는 가선의 높은 전압을 받아 공진형 컨버터를 사용하여 주파수를 높여 변압기의 사이즈 및 중량을 감소 하였으며, 안정적인 전원을 공급 하는 배터리 충전기를 개발 하였다. 이를 25kW급 시제품에 대한 시뮬레이션을 통해 입증 하였다.

• Journal of the Korean Society for Railway
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• v.14 no.5
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• pp.411-415
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• 2011

DC/DC switching power converters are commonly used to generate a regulated DC output voltages with high efficiencies from different DC input sources. The voltage mode DC/DC converter utilizes MOSFET (metal-oxide semiconductor field effect transistor), inductor, and a PWM (pulse-width modulation) controller with oscillator, amplifier, and comparator, etc. to efficiently transfer energy from the input to the output at periodic intervals. The fundamental boost converter and a buck converter containing a switched-mode power supply are studied. In this paper, the electrical characteristics of DC/DC power converters are simulated by program of SPICE, and the PWM controller is implemented to check the operation. In addition, power efficiency is analyzed based on the specification of each component.

• Journal of the Korean Society for Railway
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• v.15 no.2
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• pp.116-121
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• 2012

DC/DC switching power converters produce DC output voltages from different DC input sources. The converter is used in regenerative braking of DC motors to return energy back in the supply, resulting in energy savings for the systems containing frequent stops. The DC/DC converter is composed of a PWM-IC (pulse width modulation integrated circuit) controller, a MOSFET (metal-oxide semi-conductor field-effect transistor), an inductor, capacitors, and resistors, etc. PWM is applied to control and regulate the total output voltage. In this paper, radiation shows the main influence on the changes in the electrical characteristics of comparator, operational amplifier, etc. in PWM-IC. In the PWM-IC operation, the missing pulses, the changes in pulse width, and the changes of the output waveform are studied by the simulation program with integrated circuit emphasis (SPICE) and compared with experiments.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.40 no.3
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• pp.208-214
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• 2003

Because the digital control includes microprocessor different from an analog control, the digital control enables to monitor internal parameters of DC-DC converter and to control output voltage remotely by communicating with a Window based PC and also to monitor whether exact voltage is output or not. These things are impossible in an analog control. In this paper, a simple buck converter controlled by DSP(TMS320C31) is implemented. This converter outputs 0V to 5V from 15V input voltage and is controlled by a PD algorithm using DSP. Finally the response characteristics of a step reference voltage and in a steady state are analyzed to verify the usefulness of this digital controlled converter.

• Journal of Advanced Marine Engineering and Technology
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• v.41 no.1
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• pp.76-82
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• 2017

Since the introduction of electronically controlled engines and electric propulsion ships, the need for an uninterruptible power supply for emergency power supply devices that use batteries has gained importance. The bidirectional converter in such emergency power supply devices is a crucial component. This paper proposes, a topology for an improved DC-DC bidirectional converter that is characterized by a high voltage conversion ratio and low voltage stress of switches. To confirm the performance of the converter, a computer simulation was executed with PSIM software. The conversion ratio of the proposed converter was found to be four times higher than the conventional boost converter in step-up mode and one-fourth that of the conventional buck converter in step-down mode, and the voltage stress of the switches was one-fourth of the high-side voltage. Moreover, the proposed converter was confirmed to be able to distribute equal currents between two interleaved modules without using any extra current-sharing control method because of the charge balance of its blocking capacitors.