• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2011년도 추계학술대회
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• pp.404-407
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• 2011

본 논문은 전류모드에서 동작하는 PWM/PFM DC-DC Boost 변환기의 설계를 하였다. 부하전류가 클 때는 PWM으로 동작하고, 부하 전류가 작을 때는 PFM으로 동작함으로써 높은 효율을 유지할 수 있게 설계하였다. DC-DC Boost 변환기는 $0.35{\mu}m$ 공정으로 설계되었으며, 500KHz의 주파수에 동작하고, 최대 효율은 92.1%이다. 그리고 부하 전류가 최대 600mA까지 구동 할 수 있다. 전체 칩의 크기는 패드를 포함하여 $1300{\mu}m{\times}1070{\mu}m$이다. 따라서 작은 칩 면적으로 넓은 부하전류를 구동할 수 있는 DC-DC Boost 변환기를 설계하였다.

• Journal of Power Electronics
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• 제15권3호
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• pp.652-659
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• 2015

This paper presents a new hybrid soft switching dc-dc converter with a low circulating current and high circuit efficiency. The proposed hybrid converter includes two sub-converters sharing two power switches. One is a three-level PWM converter and the other is a LLC converter. The LLC converter and the three-level converter share the lagging-leg switches and extend the zero-voltage switching (ZVS) range of the lagging-leg switches from nearly zero to full load since the LLC converter can be operated at f_sw (switching frequency) $\approx$ f_r (series resonant frequency). A passive snubber is used on the secondary side of the three-level converter to decrease the circulating current on the primary side, especially at high input voltage and full load conditions. Thus, the conduction losses due to the circulating current are reduced. The output sides of the two converters are connected in series. Energy can be transferred from the input voltage to the output load within the whole switching period. Finally, the effectiveness of the proposed converter is verified by experiments with a 1.44kW prototype circuit.

• Journal of Electrical Engineering and Technology
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• 제13권1호
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• pp.143-151
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• 2018

In this paper, a novel hybrid configuration combining a phase-shift full-bridge (PSFB) and a half-bridge resonant LLC converter is proposed for the On-Board Charger of Electric Vehicles (EVs). In the proposed converter, the PSFB converter shares the lagging-leg switches with half-bridge resonant converter to achieve the wide ZVS range for the switches and to improve the efficiency. The output voltage is modulated by the effective-duty-cycle of the PSFB converter. The proposed converter employs an active reset circuit composed of an active switch and a diode for the transformer which makes it possible to achieve zero circulating current and the soft switching characteristic of the primary switches and rectifier diodes regardless of the load, thereby making the converter highly efficient and eliminating the reverse recovery problem of the diodes. In addition an optimal power sharing strategy is proposed to meet the specification of the charger and to optimize the efficiency of the converter. The operation principle the proposed converter and design considerations for high efficiency are presented. A 6.6 kW prototype converter is fabricated and tested to evaluate its performance at different conditions. The peak efficiency achieved with the proposed converter is 97.7%.

• Journal of Power Electronics
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• 제17권4호
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• pp.849-859
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• 2017

This paper illustrates the analysis and design of a multi-resonant converter applied to an electric vehicle (EV) charger. Thanks to the notch resonant characteristic, the multi-resonant converter achieve soft switching and operate with a narrowed switching frequency range even with a wide output voltage range. These advantages make it suitable for battery charging applications. With two more resonant elements, the design of the chosen converter is more complex than the conventional LLC resonant converter. However, there is not a distinct design outline for the multi-resonant converters in existing articles. According to the analysis in this paper, the normalized notch frequency $f_{r2n}$ and the second series resonant frequency $f_{r3n}$ are more sensitive to the notch capacitor ratio q than the notch inductor ratio k. Then resonant capacitors should be well-designed before the other resonant elements. The peak gain of the converter depends mainly on the magnetizing inductor ratio $L_n$ and the normalized load Q. And it requires a smaller $L_n$ and Q to provide a sufficient voltage gain $M_{max}$ at ($V_{o\_max}$, $P_{o\_max}$). However, the primary current increases with $(L_nQ)^{-1}$, and results in a low efficiency. Then a detailed design procedure for the multi-resonant converter has been provided. A 3.3kW prototype with an output voltage range of 50V to 500V dc and a peak efficiency of 97.3 % is built to verify the design and effectiveness of the converter.

• Journal of Biosystems Engineering
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• 제8권1호
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• pp.38-46
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• 1983

This study was carried out to investigate the possibility of improving the performance of a kerosene engine with water addition. The engine used in this study was a single-cylinder, four-cycle kerosene engine with the compression ratio of 4.5. Water could be successfully added into the inlet manifold by an extra carburetor for the volumetric ratios of 5, 10, 20, and 30 percents. Variable speed tests at wide-open throttle were performed for five speed levels in the range of 1,000 to 2,200rpm for each fuel type. Volumetric efficiency and brake specific fuel consumption were determined, and brake thermal efficiency based on the lower heats of combustion of kerosene was calculated. To examine variation in fuel consumption, CO concentration, and cooling water temperature, part load tests were also performed. The results obtained are summarized as follow. (1) Brake torque increased almost in proportion to volumetric efficiency. But the ratio of increase in torque was greater than that of volumetric efficiency. Mean torque over the speed range of 1,000 to 2,200rpm increased 1, 3, 7, and 2 percents for 5, 10, 20, and 30 percents water addition, respectively. The increase in brake torque with water addition was greater at lower speeds. (2) Mean brake specific fuel consumption over the speed range of 1,000 to 2,200rpm decreased 1, 2, 3, and 3 percents for 5, 10, 20, and 30 percents water addition, respectively. (3) Mean temperature of cooling water over the speed range of 1,000 to 2,200rpm decreased 2, 4, 8, and 12 percents for 5, 10, 20, and 30 percents water addition, respectively. (4) The effects of decreasing CO concentration in the exhaust emissions with water addition were significant. At the speed range of 1,000 to 2,200rpm, CO concentration in the exhaust emissions decreased 2, 10, 23, percents for 5, 10, and 20 percents water addition, respectively. (5) Deposits were not discovered in the combustion chamber during the experiment. However, a little rust was formed in the water-supply carburetor.

• 전력전자학회논문지
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• 제15권6호
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• pp.466-476
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• 2010

본 논문에서 다이오드정류기와 커패시터 필터로 구성된 입력전원을 가지고 동작되는 60W이하의 출력파워용량을 갖는 노트북용 어댑터를 위한 새로운 LLC 공진컨버터에 대한 내용이다. 보조스위치의 동작에 의해 제안된 LLC 공진컨버터는 모든 입력전원 (110VAC/220VAC) 및 부하조건에서 높은 효율특성을 가지고 전력을 전달 할 수 있다. 제안된 컨버터에 대한 동작특성에 대해 분석, 서술되어 있으며, 60W 시제품제작 및 실험을 통하여 적용 가능함을 보였다.

• 대한기계학회논문집B
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• 제37권11호
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• pp.1015-1022
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• 2013

본 연구에서는 현재 개발중인 200kW 급 마이크로 가스터빈의 운전 특성을 모사하였다. 세부적인 성능 데이터를 이용하여 부분부하 제어방식(터빈 입구온도 제어방식(constant TIT control)과 터빈 출구온도 제어방식(constant TET control))과 외기온도에 따른 성능 및 작동특성을 분석하였다. 넓은 운전 범위에 대하여 압축기 서지마진과 터빈 입출구 온도 같은 작동 파라미터의 민감도를 단위 연료량 변화에 따라 예측하였다. 정상상태 계산으로 부분부하 변동 시 최대서지마진의 감소에 대한 정보를 민감도 분석을 통해 알 수 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 학술대회 논문집 전문대학교육위원
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• pp.70-74
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• 2003

The buck-boost converter is employed as the variable output PFC power stage. From the loss analysis, this topology has a high efficiency from light load to heavy load. A modified input current sensing scheme is presented to overcome the problem of the insufficient phase margin for the PFC circuit near the maximum output voltage. The variable output PFC circuit has a good performance in the wide output voltage range, under both the Boost mode when the output voltage is high and the Buck+Boost mode when the output voltage is low.

• 전기학회논문지
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• 제62권8호
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• pp.1125-1131
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• 2013

Wireless power transmission technology has been studied variety. Recently, wireless power transmission technology used by resonance and magnetic induction field is applied to various fields. However, magnetic resonance and inductive coupling are have drawbacks - power transmission distance is short. Microwave transmission and accept techniques have been developed to overcome short distance. However, improvement in efficiency is required. This paper, propose a high-efficiency microwave energy acceptor IC(EAIC). Suggested EAIC is consists of RF-DC converter and DC-DC converter. Wide Input power range is -15 dBm ~ 20 dBm. And output voltage is boosted up to 5.5 V by voltage boost-up circuit. EAIC can keep the output voltage constant. Available efficiency of RF-DC converter is 95.5 % at 4 dBm input. And DC-DC efficiency is 94.79 % at 1.1 mA load current. Fully EAIC efficiency is 90.5 %.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 하계학술대회 논문집 B
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• pp.1110-1113
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• 2002

A Single-Stage Single-Switch power-factor- correction(PFC) AC/DC Converter with universal input is presented in this paper. The PFC Converter can be achieved based upon the continuous current mode(CCM). The switch has less current and voltage stresses over a wide range of load variation so that a low voltage rating device can be used. The presented converter features high power factor high efficiency, and low cost. An 90W prototype was implemented to show that it has 70% efficiency with low voltage stress over universal line input.