• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.174-176
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• 2003

The power conversion system must be increased switching frequency in order to achieve a small size, a light weight and a low noise. This paper proposes a skillful and a concise PWM DC-DC converter employing both zero voltage and zero current high frequency switching(ZVCS) operation. The Proposal ZVCS circuit is composed with resonant circuit using active resonant condenser. And this circuit provides switches with ZVS and ZCS by quasi resonant only that switching transients appear. This operation results in reduction of stress and losses in the power devices and resonant components. Some simulation results are included to confirm the validity of the analytical results.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.2
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• pp.46-52
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• 2012

This paper proposes a novel single-phase ac-ac converter topology based on the Z-source concept. The converter provides buck-boost function and plays the role of frequency changer. Compared to the traditional ac-dc-ac converter, it uses fewer devices, realizes direct ac-ac power conversion, and has a simpler circuit structure, so as to have higher efficiency and better circuit characteristics. Compared to the traditional matrix converter, it provides a wider voltage regulation range. The circuit topology, operating principle, control method and simulation results are given in this paper, and the rationality and feasibility is verified.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.2
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• pp.199-204
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• 2013

Recently, the demand for fuel efficient electric vehicles (EVs) and hybrid electric vehicles (HEVs) has been growing globally. Due to the increased number of switching devices in the electrified vehicles, the probability of the semiconductor device failure is much higher than in other application areas. A sudden failure in one of the power switches and insufficient power management ability in the systems not only decreases system performance, but also leads to critical safety problems. In this paper, novel switch open circuit fault detection method is proposed, and the proposed approach is verified by experiments.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.61 no.4
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• pp.192-198
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• 2012

Switch losses directly affect the efficiency of power conversion systems and those have big differences according to the power consumed by load systems and the structures of power conversion circuits. In this paper, analyses for switch losses in DC link converter are performed based on the circuit structures of the DC/DC converter in photovoltaic generation system whose output power is varied according to the amount of solar radiation, temperature and partial shade on the solar modules. Boost converter is adopted as a DC link converter topology of the photovoltaic generation system and the loss analyses for the switches used in the boost converters are performed according to the circuit structures. Analyses like the things performed in this paper will be a prerequisite to designing the photovoltaic generation system whose output power is changed according to the environmental variations.

• ETRI Journal
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• v.33 no.5
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• pp.818-821
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• 2011

A D-band subharmonically-pumped resistive mixer has been designed, processed, and experimentally tested. The circuit is based on a $180^{\circ}$ power divider structure consisting of a Lange coupler followed by a ${\lambda}$/4 transmission line (at local oscillator (LO) frequency). This monolithic microwave integrated circuit (MMIC) has been realized in coplanar waveguide technology by using an InAlAs/InGaAs-based metamorphic high electron mobility transistor process with 100-nm gate length. The MMIC achieves a measured conversion loss between 12.5 dB and 16 dB in the radio frequency bandwidth from 120 GHz to 150 GHz with 4-dBm LO drive and an intermediate frequency of 100 MHz. The input 1-dB compression point and IIP3 were simulated to be 2 dBm and 13 dBm, respectively.

• Journal of the Semiconductor & Display Technology
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• v.20 no.4
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• pp.68-71
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• 2021

In this paper, GaN-SBD devices with excellent breakdown voltage and frequency characteristics for use in high-power microwave wireless power transmission has been modeled for PSpice circuit simulation. The RF-DC conversion circuits were simulated and compared with a commercial Si-SBD device. Although the modeled GaN-SBD devices had lower RF-DC conversion efficiency compared to Si-SBD at 2.4 and 5.8 GHz, it was confirmed through PSpice circuit simulations that they can be used sufficiently according to the required application circuit in a high power situation.

• Journal of Power Electronics
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• v.5 no.2
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• pp.99-103
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• 2005

In this paper, a novel circuit topology of a three-winding coupling inductor-assisting a high-frequency PWM boost chopper type DC-DC power converter with a high boost voltage conversion ratio and low switch voltage stress is proposed for the new energy interfaced DC power conditioner in solar photovoltaic and fuel cell generation systems. The operating principle in a steady state is described by using its equivalent circuits under the practical condition of energy processing of a lossless capacitive snubber. The newly-proposed power MOSFET boost chopper type DC-DC power converter with the three-winding coupled inductor type transformer and a single lossless capacitor snubber is built and tested for an output power of 500W. Utilizing the lower voltage and internal resistance power MOSFET switch in the proposed PWM boost chopper type DC-DC power converter can reduce the conduction losses of the active power switch compared to the conventional model. Therefore, the total actual power conversion efficiency under a condition of the nominal rated output power is estimated to be 81.1 ％, which is 3.7％ higher than the conventional PWM boost chopper DC power conversion circuit topology.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.521-524
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• 1996

A new zero voltage and nero current switching(ZVZCS) full bridge(FB) PWM converter b proposed to improve the performance of the previously presented ZVZCS-FB-PWM converters [7,8]. By adding a secondary active clamp and controlling the clamp switch moderately, ZVS(for leading-leg switches) are ZCS(for lagging-leg switches) are achieved without nay lossy components, the reverie avalanche break down of leading-leg IGBTs[7] or the saturable reactor in the primary[8]. Many advantages including simple circuit topology, high efficiency, and low cost mate the new converter attractive for high voltage and high power(> 10 kW) applications. The principle of operation is explained and analyzed. The features and design considerations of the new converter are also illustrated and verified on an 1.8 kW, 100 kHz IGBT based experimental circuit.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.4
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• pp.402-412
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• 1995

A new energy conversion system which converts wind energy directly to heat instead of transforming it to electric power beforehand is suggested in this study. The new energy conversion system is composed of two big parts divided by their functions. One of them is a wind turbine part, and another is the heat energy conversion part. The object of this study is confined only to the heat energy conversion part, so the wind turbine is replaced with an electric motor for the convenience of experiment. In the experimental process, pressure difference at the hydraulic pump, revolution speed of the hydraulic pump, temperature at a few points on the oil circuit and the water circuit are measured at time intervals of five minutes. And integral values of input energy to the system and stored energy in the system is investigated.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1986.10a
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• pp.68-71
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• 1986

A new circuit configuration for charge-balancing successive approximation Analog-to-Digital converters is described. This consists of a improved successive approximation register(SAR) and a weighted capacitor Digital-to-Analog converter (WCDAC). Due to the inherent conversion property of the WCDAC, the A/D converter using the WCDAC can be simply implemented by successive approximation conversion method, and 4bit monotonicity conversion with differential nonlinearity less 1/2LSB is completed in 80 US.