• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05b
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• pp.19-22
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• 2004

The resonant planar transformer, which had power capacity of 300 W, input voltage of 220 V, output voltage of 15 V, and switching frequency of 500 kHz, was designed and manufactured by using the planar core with large effective area and the flat copper lead frames for miniaturization and high efficiency of the switching mode power supply (SMPS). As well as, a resonant converter equipped with the above mentioned planar transformer was manufactured and electromagnetic characteristics were investigated. The numerical value of turns for 1st and 2nd winding were 12 and 2 respectively. The self inductance of 1st winding was 33.2 ${\mu}H$, very low leakage inductance of 1.27 ${\mu}H$, and the coupling factor of 0.98 were obtained at switching frequency of 300 kHz. The high efficiency of 88.21 % for the SMPS equipped with planar transformer was obtained at power capacity of 300 W.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.1
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• pp.61-65
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• 2017

In this paper a prototype of high frequency heating power supply system based on the high frequency heating principle is designed to take the place of acupuncture, moxibustion, warm dressing treatment and some other traditional physical therapy methods. Which possess the advantages of low cost, convenient, easy operation and good effect. The high frequency heating power supply can generate a pulse voltage of more than 1KV with 300KHz switching frequency to heat the patient's skin. The skin temperature can reach to $41{\sim}42^{\circ}C$. The peak current control method is used to maintain the skin temperature in the designed range. The design of the main circuit is based on the flyback converter topology. An easier and practical design method is proposed in this paper. The power supply system prototype is verified to be stable and reliable by both the simulation and experimental results.

• Proceedings of the KAIS Fall Conference
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• 2004.06a
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• pp.193-197
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• 2004

The four-leg Voltage Source Converter(VSC) can use the DC link voltage effectively by the 3-D SVPWM method. Hence the DC battery voltage can be reduced by $15\%$ in comparison to that of the conventional line-interactive UPS system. In this paper a novel line interactive Uninterruptible Power Supply(UPS) using the two four-leg VSCs is proposed. One VSC is in parallel with the ac link reactor of the power source side, and the other is in series with the load. The parallel four-leg voltage source inverter controls the three-phase line voltage independently in order to control the line reactor current indirectly. It eliminates the neutral line current and the active ripple power of the source side using the pqr theory so that unity power factor and the sinusoidal source current can be achieved even though both the source and the load voltages have zero sequence components. The series four-leg voltage source inverter compensates the line voltage and allows it to be balanced and harmonic-free. Both of the parallel and series four-leg voltage source inverters always act as independently controllable voltage sources, so that the three-phase output voltage shows a seamless transition to the backup mode. The feasibility of the proposed UPS system has been investigated and verified through computer simulations results.

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.4
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• pp.357-363
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• 2014

A programmable smart charger compatible to various load conditions is proposed in this paper. Since the proposed smart charger is compatible to various mobile devices having different rated voltage and power, it is convenient for carrying and easy to standardize many kinds of battery chargers. Moreover, since it uses the input impedance and built-in PMIC (Power management IC) of the load system to recognize the connection state and specifications of load system, hardware changes of load system is not only hardly necessary but it also features no addition communication cable and easy implementation. To confirm the validity of the proposed charger, the theoretical analysis and experiment results from a prototype compatible to three load conditions 5V/1A, 5V/2A and 12V/1A are provided.

• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.130-132
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• 2008

In this paper, we have proposed a novel zero-voltage-switching (ZVS) soft-switching H-bridge inverter. Because the conventional H-Bridge inverter generates switching losses at turn on and off, the efficiency is reduced. The proposed inverter operates ZVS switching using an auxiliary switch and resonant circuit to improve the efficiency. in the DC-DC converter stage, it can reduce not only switching loss but also capacity and size of passive devices due to the resonant elements. DC-AC inverter stage supplies load with energy through the ZVS operation of 4 switches. A detail mode analysis of operating is in presented. We have presented the inverter topology, principle of operation and simulation results obtained from the PSIM simulator.

• Proceedings of the KIPE Conference
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• 2014.07a
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• pp.191-192
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• 2014

Multiple output converters (MOCs) are widely used for applications which require various levels of the output voltages due to their benefits in cost, volume, and efficiency. However, most of the MOCs developed so far can regulate only one output tightly and require as many secondary windings in the transformer as the number of the outputs. In this paper, a novel Time Division Multiple Control (TDMC) method to regulate all the outputs in high precision is proposed and applied for the multiple output battery charger based on the phase shift full bridge topology to charge a multiple number of batteries at one time. The proposed converter can charge three different kinds of batteries or same kind of batteries in different state of charges (SOCs) by using constant current/constant voltage (CC/CV) charge mode independently. At the same time it can provide an even degree of tight regulation for each output to satisfy the strict ripple requirement of the battery. The validity and feasibility of the proposed method are verified through the experiments.

• Proceedings of the KIEE Conference
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• 2003.11c
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• pp.349-352
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• 2003

A personal low-frequency stimulator is a portable device to relax muscle pains of a person. The stimulator generates combined low-frequency pulses to be applied to pads attached to painful muscles. This paper reports a development of such device with its characteristic analyses. The major components of our stimulator are MCU, high-voltage generating circuit part, high-voltage switching circuit part, input switch part and display unit. High-voltage generating circuit is designed by using a boost converter circuit and allows user control of the output voltage. High-voltage switching circuit, controlled by MCU, generates output voltage to be applied to pads. Input switch part is composed of power supply, intensity selection, mode selection and memory. Display unit adopts a text LCD module to display modes, Intensity, output frequency and user set-up time. Our designed safety circuit, to protect human body from possible electric shock, slowly increases the output voltage to the selected output intensity. It continuously checks the output pulse shape and disable the output when dangerous pulses are detected. This paper also shows some experimental results.

• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.92-94
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• 2019

양방향 스위치를 가지는 Bridgeless PFC 컨버터(BBPFC)는 구조상 복잡한 플로팅 게이트 드라이버를 활용함에도 불구하고 좋은 공통모드 잡음 즉, Common-Mode (CM) 노이즈 특성과 간단한 제어 방법으로 인해 많은 브리지리스 PFC 컨버터 중에서도 고전력 응용분야에서 매우 매력적인 토폴로지이다. 이러한 BBPFC는 도통 경로 상에 위치한 정류 다이오드의 역회복 특성의 상대적인 편차를 활용하여 전력 밀도를 감소시키지 않고도 좋은 공통모드 (CM) 노이즈 특성의 확보가 가능하다. 하지만 이러한 장점을 가지는 BBPFC 구조를 고전력 서버용 전원장치분야에서 활용할 경우, 이미 등록된 특허로 인해 매우 높은 개런티를 지불해야 하므로 그 활용이 매우 제한적이다. 따라서, 본 논문에서는 이미 등록된 특허를 회피하고, 동시에 기존 BBPFC 회로가 가지는 단점인 플로팅 게이트 드라이버를 활용하는 단점을 개선하는 새로운 형태의 브리지리스 PFC 컨버터를 제안한다. 제안된 컨버터는 기존 BBPFC가 가지는 장점인 좋은 (CM) 노이즈 특성을 가지며, 동시에 높은 효율을 달성 할 수 있다. 또한 제안된 컨버터의 경우, 복잡한 플로팅 형태의 게이트 드라이버 회로가 아닌 간단한 부트스트랩 회로를 활용하여 회로를 운용할 수 있다. 더불어 제안된 컨버터는 입력의 양과 음의 주기에서 단 하나의 스위치를 사용하여 회로를 구동할 수 있기 때문에 기존회로 대비 적은 손실을 가져 높은 효율의 획득이 가능하다. 본 논문에서는 제안된 구조에 대해 하이라인 $230V_{RMS}$ 입력과 800W / 400V 출력의 조건을 적용하여 제안하는 구조의 효용성을 검증하고자 한다.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.6
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• pp.459-468
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• 2020

The pole interaction of the line-commutated converter high-voltage direct current (HVDC) is analyzed, and a practical solution that uses a surge arrester is proposed. Jeju HVDC No. 2 is a double-monopole HVDC link that has a rated power capacity of 2 × 200 MW and was commissioned in 2012. During normal operation, Jeju HVDC No. 2 is operated in the bipolar mode to minimize the loss caused by the dedicated metallic return. However, when one pole of the inverter valve is bypassed, a commutation failure can occur in the other pole. This phenomenon is called pole interaction in this work. This pole interaction interrupts the HVDC power transfer for almost 2 s and may affect the stability of the power system. This research proposes the installation of a surge arrester at the inverter neutral, which can be an effective and practical solution for pole interaction. The HVDC system is analyzed, and the residual voltage of the surge arrester is determined. Detailed simulation using PSCAD/EMTDC demonstrates that the proposed method eliminates the pole interaction of the bipolar-operated HVDC.

• Journal of Ocean Engineering and Technology
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• v.36 no.1
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• pp.21-31
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• 2022

In recent years, various studies have been conducted on oscillating-water-column-type wave energy converters (OWC-WECs) with multiple chambers with the objective of efficiently utilizing the limited space of offshore/onshore structures. In this study, a numerical investigation based on a numerical wave tank was conducted on single, dual, and triple OWC chambers to examine the hydrodynamic performances and the energy conversion characteristics of the multiple water columns. The boundary value problem with the Laplace equation was solved by using a numerical wave tank based on a finite element method. The validity of the current numerical method was confirmed by comparing it with the measured data in the previous experimental research. We undertook a series of numerical simulations and observed that the water column motion of sloshing mode in a single chamber can be changed into the piston motion of different phases in multiple OWC chambers. Therefore, the piston motion in the multiple chambers can generate considerable airflow at a specific resonant frequency. In addition, the division of the OWC chamber results in a reduction of the time-dependent variability of the final output power from the device. As a result, the application of the multiple chambers leads to an increase of the energy conversion performance as well as a decrease of the variability of the wave energy converter.