• Proceedings of the KIPE Conference
• /
• 2011.07a
• /
• pp.364-365
• /
• 2011

본 논문에서는 납축전지 모델링, 파라미터 도출 및 3kW급 3상 절연형 인터리브드 배터리 충방전기를 설계하고 부하실험 결과를 분석하였다. 제작된 컨버터는 모든 스위치가 ZVS로 동작하여 높은 효율을 갖고 3상 구조를 채택하여 전류경로의 분산을 통한 전력전달 능력 증대의 효과 및 입력전류 리플크기를 줄여주는 인터리브드 효과를 갖는다. 승압/강압 능력이 있는 부스트/벅 컨버터 구조를 갖도록 하여 낮은 권선비의 변압기로 높은 승압/강압 전력변환, 에너지원과 부하사이에 절연이 가능 해진다. 이러한 동작을 실험을 통해 확인하고 3kW 부하에서 약 95% 효율로 동작하는 것을 실험을 통하여 확인하였다.

• Proceedings of the KIPE Conference
• /
• 2011.07a
• /
• pp.427-428
• /
• 2011

조명용 LED 시스템은 크게 LED 광원과 이 광원을 구동하기 위한 Power부로 구성되며 LED를 이용한 조명용 광원을 구성할 경우 LED 자체가 점광원이므로 면광원 구성을 위해서는 많은 수의 LED Array 구성이 필요하다. LED Array 구성에 있어 직 병렬 구성 및 조합은 직류 공급 장치의 출력 사양을 결정하는 중요한 요인이 된다. 본 논문에서는 온도 변화에 따른 전류변동을 보상하기 위한 DC/DC 컨버터 구조를 제안한다. 컨버터의 Base 입력전압 최대치는 온도변화에 대한 전류변동의 최저치가 되며, 온도변화에 따른 전압 조정을 위한 컨버터는 0~6[V]만을 제어함으로서 낮은 전압으로 전류를 제어하고, 결과적으로 효율을 증대할 수 있을 거라 예상된다.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.61 no.2
• /
• pp.59-66
• /
• 2012

Recently, the market of Electric Vehicle(EV) is increasing more and more than before. Thus a new heater for the EV is required. The PTC devices may be used the heater for the EV. In this paper, a simple DC-DC Converter is proposed as the PTC Heater for the EV. The proposed circuit was optimally desired to decrease the stress of the power devices and reduce the current ripples. To apply the result of the test in the laboratory to the actual EV system with the high DC voltage, ripple current, average current and output peak current are predicted by using the least-squares method. Finally, the proposed circuit is validated by various experiments.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.19 no.2
• /
• pp.116-123
• /
• 2014

In this paper, a soft-switching scheme for the PWM interleaved buck converter(IBC) is newly proposed to obtain the advantages of both the conventional PWM interleaved buck and resonant converters such as ease of control, reduced switching losses and stresses, and low EMI. To obtain the soft-switching action, the proposed scheme employs an auxiliary circuit, which is added to the conventional interleaved buck converter and used to achieve soft-switching for both the main switches and the output diodes while not incurring any additional losses due to the auxiliary circuit itself. In this paper, the basic operations are discussed and design guidelines are presented. And through the experimental results, the usefulness of the proposed converter is verified.

• Proceedings of the KIPE Conference
• /
• 2012.11a
• /
• pp.99-100
• /
• 2012

본 논문은 마이크로 그리드에서 에너지 저장용 시스템으로 이용되는 슈퍼커패시터용 양방향 DC-DC 컨버터의 충전 및 방전시 효율을 고려한 변압기 권선비 설계에 관한 것이다. 충방전 시스템의 토폴로지는 Dual Full-Bridge 방식의 양방향 DC-DC 컨버터이다. 이 컨버터는 슈퍼커패시터의 충전 및 방전시의 스위칭 동작에 따라 벅 또는 부스트 모드로 동작하므로 동일한 출력 조건하에 권선비를 달리해가면서 모드별로 스위칭 손실을 계산하였으며, 손실이 최소로 되는 변압기의 권선비를 제시하고자 한다.

• Phonetics and Speech Sciences
• /
• v.7 no.4
• /
• pp.103-110
• /
• 2015

The purpose of this study is to assess the vowel property by examining the vowel duration of the American English vowles found in the Buckeye corpus[6]. The vowel durations were analyzed in terms of various linguistic factors including the number of syllables of the word containing the vowel, the location of the vowel in a word, types of stress, function versus content word, the word frequency in the corpus and the speech rate calculated from the three consecutive words. The findings from this work agreed mostly with those from earlier studies, but with some exceptions. The relationship between the speech rate and the vowel duration proved non-linear.

• Proceedings of the KIPE Conference
• /
• 1998.11a
• /
• pp.44-48
• /
• 1998

In the buck-boost DC-DC converter which is used at a certain situation such as in factories where loads often change a lot, the switches in the device make big energy loss in operating at Buck-Boost Mode due to hard switching and are affected by lots of stresses which decrease the efficiency rate of the converter. In order to improve this problem, to decrease the loss of snubber and switching, it has been investigated that zero voltage switching mode and zero current switching mode which make the operation of switches with soft switching. For the more sophisticated and advanced device, this paper is presented the Partial Resonant Soft Switching Mode Power Converter which is adapted the power converter having the partial resonant soft switching mode, that makes switches operate when the resonant current or voltage becomes zero by making the resonant circuit partially at turning on and off of the switches with suitable layout of the resonant elements and switch elements in the converter. Also, this paper includes the analysis and simulation of the Partial Resonant type Buck-Boost Chopper.

• Proceedings of the IEEK Conference
• /
• 2008.06a
• /
• pp.537-538
• /
• 2008

A step-down DC-DC converter with On-chip Compensation for battery-operated portable electronic devices which are designed in 0.18um CMOS standard process. In an effort to improve low load efficiency, this paper proposes the PFM (Pulse Frequency modulation) voltage mode 1MHz switching frequency step-down DC-DC converter with on-chip compensation. Capacitor multiplier method can minimize error amplifier compensation block size by 20%. It allows the compensation block of DC-DC converter be easily integrated on a chip and occupy less layout area. But capacitor multiplier operation reduces DC-DC converter efficiency. As a result, this converter shows maximum efficiency over 87% for the output voltage of 1.8V (input voltage : 3.3V), maximum load current 500mA, and 0.14% output ripple voltage. The total core chip area is $mm^2$.

• Proceedings of the IEEK Conference
• /
• 2008.06a
• /
• pp.1069-1070
• /
• 2008

This paper presents a high efficient two-stage interleaved synchronous buck CMOS DC-DC converter. The proposed circuit has a fixed duty cycle as 0.5 by an added buck converter. And it causes the best ripple cancelation of the output current ripple. The proposed circuit was simulated by HSPICE with a standard CMOS $0.35{\mu}m$ process parameter.

• Journal of the Korean Society for Precision Engineering
• /
• v.27 no.3
• /
• pp.104-110
• /
• 2010

Cyclic deformations of polymer foam film are simulated using the finite element method. Material of polymer foam film is polypropylene (PP). The calculated polymer foam film is micro-scale thin film has cellular structure. The polymer foam film is used in ferro-electret applications. The polymer foam film is idealized to one cell structure as lens shaped stretched truncated octahedron model. Cyclic deformation is performed by uniaxial stretching. Stretching direction is perpendicular to plane of cellular film. Various cyclic strain amplitudes, pore wall thicknesses, pore shape are investigated to find deformation tendency of cellular structure. Consequently, cellular structure has various macroscopic stresses on cyclic deformation with various pore thickness and pore shape.