• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.365-366
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• 2017

LLC resonant DC-DC converter is widely used in many kinds of applications such as battery energy storage systems, wireless power transfer and high voltage power supply. It is because of characteristics like high efficiency, power density, isolation, wide power level and stability enhancement at high switching frequency. Small signal modeling helps to design controller of the converter by approximating the behavior of nonlinear system with linear state equations. This paper presents comparison between small signal modeling analysis and experimental results of LLC resonant converter.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.860-862
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• 1993

This paper presents a study on a self oscillating dc/dc converter with low cost, high power density. This converter only consists of power filter, switch and comparater and time delay reduction parts. But it has better characteristics than the conventional self-oscillating dc/dc converter. And it can be made by a few devices and can be smaller size. These type of converters find their applications in many industrial equipments. And the performances of the proposed system are verified through expriment.

• Proceedings of the KIPE Conference
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• 2007.07a
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• pp.147-149
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• 2007

A new half bridge converter without DC offset of magnetizing current is proposed. The proposed half bridge converter can realize no DC offset of magnetizing current as well as no circulating current, and guarantee ZVS operation. Therefore it has high efficiency and high power density, especially in wide input range. The operational principle, DC conversion ratio and ZVS analysis are presented. Experimental results demonstrate that the proposed converter can achieve a significant improvement in the efficiency.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.4
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• pp.259-265
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• 2010

The proposed method offers an improved control method for high power density AC/DC adapter by using more energy efficient electrical equipments. Power factor corrector (PFC) topology is based on boost topology with boundary conduction mode (BCM) and DC/DC topology is based on LLC resonant converter, which helps to reduce size of the semiconductor and the magnetic devices. Test results with 85W AC/DC adapter (18.5V/4.6A) design shows that the measured efficiency is 90% at $90V_{rms}$ input voltage with power density of $36W/in^3$. It also shows low no load power consumption of about 0.5W.

• Journal of Power Electronics
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• v.18 no.4
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• pp.975-984
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• 2018

This work presents a high efficiency phase shifted full bridge (PSFB) DC-DC converter for use in the second stage of a battery charger for neighborhood electrical vehicle (EV) applications. In the design of the converter, Lithium-ion battery cells are preferred due to their high voltage and current rates, which provide a high power density. This requires wide range output voltage regulation for PSFB converter operation. In addition, the battery charger works with a light load when the battery charge voltage reaches its maximum value. The soft switching of the PSFB converter depends on the dead time optimization and load condition. As a result, the converter has to work with soft switching at a wide range output voltage and under light conditions to reach high efficiency. The operation principles of the PSFB converter for the continuous current mode (CCM) and the discontinuous current mode (DCM) are defined. The performance of the PSFB converter is analyzed in detail based on wide range output voltage and load conditions in terms of high efficiency. In order to validate performance analysis, a prototype is built with 42-54 V / 15 A output values at a 200 kHz switching frequency. The measured maximum efficiency values are obtained as 94.4% and 76.6% at full and at 2% load conditions, respectively.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.619-621
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• 1996

This paper presents the study on the development of the power factor correction convener with ZVT Boost converter, which is better than the conventional PWM Boost converter to increase the switching frequency for high density and lower stress of switch. A simple DC and small signal model for the power factor correction converter with constant switching frequency is derived. The guide line for design of controller is summarized.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.1
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• pp.75-81
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• 2017

This paper presents a design and parallel control strategy of 1.8 kW low-voltage DC-DC converter (LDC) for mild hybrid electric vehicles to improve their power density, system efficiency, and operation stability. Topology and control scheme are important on the LDC for mild hybrid electric vehicles to achieve high system efficiency and power density because of their very low voltage and large current in input and output terminals. Therefore, the optimal topological structure and control algorithm are examined, and a detailed design methodology for the power and control stages is presented. A working sample of 1.8 kW LDC is designed and implemented by applying the adopted topology and control strategy. Experimental results indicate 92.45% of the maximum efficiency and 560 W/l of power density.

• Journal of Power Electronics
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• v.2 no.4
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• pp.312-324
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• 2002

This paper presents a new PWM DC/DC converter with dual output power using single power stage, which has the isolation characteristics between each dual output. The proposed converter topology consists of two switches ($S_B$ and $S_F$) and only single secondary winding. Therefore, the proposed converter has better advantages of not only low cost and small size but also high power density because of using minimum components and devices compared with conventional methods which use multi winding transformers or several converters. The operating principle of the proposed converter topology, which includes the conventional auxiliary ZVT (Zero-Voltage-Transition) circuit to implement soft switching of the main switch, is illustrated in detail and the validity of the proposed converter is verified through several simulated and experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.5
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• pp.478-484
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• 2004

In this paper, two lossless snubber cells are proposed to generalize high frequency converter with losslless snubber. The selecting of snubber cells, which generalize high frequency converters, are depended on converter topologies. The cells have a saturable inductor, LC resonant tank and two diodes. In the cells, the saturable inductors extremely reduce resonant energy in the LC resonant tank. By minimizing resonant energy, the converter, which applies snubber cells, can operate at high frequency. These cells are applied for Buck, Boost, Buck-Boost, Cuk, ZETA, and SEPIC to generalize converter which have lossless snubber. The boost type converter has been implemented, with 400 kHz switching frequency for 125 W load to verify the converter characteristics.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.6
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• pp.551-554
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• 2017

This paper proposes a three-level LLC resonant converter using integrated magnetics (IM). Given that the switch voltage stress of the proposed converter is guaranteed to be half of the input voltage, the switching losses can be greatly reduced, thereby benefitting the high-frequency operation. To reduce the volume of reactive components such as transformers, high-frequency driving and planar core are applied. However, two resonant inductors and one transformer are required because of the three-level structure and the limited leakage inductance of the planar transformer for the resonant operation. Therefore, the effect of volume reduction is not very large. In order to solve these drawbacks, this paper proposes a new IM that integrates all magnetic elements used in the proposed three-level resonant converter by using the magnetizing inductor as a resonant inductor. The experimental results are presented by conducting a theoretical analysis of a prototype with 350 W to 800 kHz.