• Journal of IKEEE
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• v.14 no.2
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• pp.90-97
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• 2010

The high efficiency power management IC(PMIC) with DTMOS(Dynamic Threshold voltage MOSFET) switching device and DTMOS Error Amplifier is presented in this paper. PMIC is controlled with PWM control method in order to have high power efficiency at high current level. Dynamic Threshold voltage CMOS(DT-CMOS) with low on-resistance is designed to decrease conduction loss. The control parts in Buck converter, that is, PWM control circuits consist of a saw-tooth generator, a band-gap reference circuit, an DT-CMOS error amplifier and a comparator circuit as a block. the proposed DT-CMOS Error Amplifier has 72dB DC gain and 83.5deg phase margin. also Error Amplifier that use DTMOS more than CMOS showed power consumption decrease of about 30%. DC-DC converter, based on Voltage-mode PWM control circuits and low on-resistance switching device is achieved the high efficiency near 96% at 100mA output current. And DC-DC converter is designed with Low Drop Out regulator(LDO regulator) in stand-by mode which fewer than 1mA for high efficiency.

• Journal of Electrical Engineering and Technology
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• v.11 no.6
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• pp.1634-1644
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• 2016

In this paper, a current-fed two-inductor bi-directional DC/DC converter using resonance (CF-TIBCR) and its design method are proposed. The CF-TIBCR has characteristics of low current ripple and a high current rating because of two separated inductors. Also, it achieves zero voltage switching for all switches and zero current switching for switches of a low voltage stage by using the resonant tank. Besides, a voltage spike problem in conventional current-fed converters is solved without the need for an additional snubber or clamping circuits. As a result, the CF-TIBCR features high step-up and high efficiency. Since the proposed converter has difficulty achieving the soft-switching condition when the converter requires the low voltage transfer ratio, a method that varies the number of resonant cycles is adopted to extend the output voltage range with satisfying the soft-switching condition. The principles of the operation characteristics are presented with a theoretical analysis, and the proposed converter is verified through results of an experiment using a laboratory prototype.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.6
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• pp.507-515
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• 2012

DC-DC converter which composed of LLC resonant converter, operated by fixed switching frequency with fixed duty cycle (50%), and flyback converter to provide constant output voltage($400V_{DC}$) with variation of input voltage($30-60V_{DC}$) is proposed in this paper. To obtain constant output voltage($400V_{DC}$), flyback converter is not operated in case of above the maximum input voltage($60V_{DC}$) and operated as the input voltage decreases to below 60VDC. Therefore, flyback converter can be designed to the 50% power rating of the maximum power in the proposed DC-DC converter. Operation modes and voltage gain characteristics were analyzed and a 360W prototype converter was tested to verify the proposed converter.

• Journal of Power Electronics
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• v.12 no.1
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• pp.83-87
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• 2012

Input-series-output-parallel (ISOP) modular converters consisting of multiple modular DC/DC converters can enable low voltage rating switches for use in high voltage input applications. In this paper, an input voltage sharing control strategy for input-series-output-parallel (ISOP) full-bridge (FB) DC/DC converters is proposed. By sensing the difference in the input current of two modules, the system can achieve input voltage sharing for DC-DC modules. The effectiveness of the proposed control strategy is verified by simulation and experimental results obtained with a 200w-50kHz prototype.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.2
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• pp.137-143
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• 2008

High voltage MLCCs with C0G temperature coefficient characteristics could apply DC-DC invertor were investigated for its dielectric properties. Also we manufactured MLCC through various process and studied the characteristics of dielectric break down voltage [BDV] and dielectric property as the variation of thickness in the green sheet and how to pattern the internal electrode. As the thickness of green sheet is increase, the dielectric BDV per unit thickness is decreased. But as the pattern of internal electrodes were floated we could manufacture the high voltage MLCC maintained its dielectric BDV a unit.

• Journal of the Semiconductor & Display Technology
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• v.7 no.2
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• pp.7-12
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• 2008

This paper proposed DC-DC converter for fuel cell that have high voltage and high current output characteristics. It is required step-up converter to use by general power supply, because the general rated voltage of fuel cell is low about 20$\sim$50V. The miniaturization of converter and DC link voltage can be controlled and high quality of output voltage uses mainly DC-DC converter. The boost converter and buck-boost converter do not get high boosting ratio. It is that proposed boost-flyback converter. Through simulation and an experiment, it could get high boosting ratio and efficiency more than 90%.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.4
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• pp.343-349
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• 2005

This paper proposes a novel zero-voltage-switching (ZVS) Push-pull DC-DC Converter for high input voltage and high power applications. This topology utilizes two switches in series to replace one switch in conventional push-pull converter, and two clamping diodes are introduced. The voltage stress of the switches is the input voltage, and the switches can realize ZVS with the use of the leakage inductance of the transformer. Furthermore, secondary full-wave rectifier with a clamping capacitor is used to eliminate the voltage oscillation and spike of the rectifier diodes due to the reverse recovery. Therefore, the electromagnetic interference is reduced effectively. The operation principle of the proposed converter is analyzed theoretically. The output characteristic, ZVS condition and design principle of the clamping capacitor are discussed. Experimental results obtained from a 270V input 2kW prototype with $95.8\%$ high efficiency confirms the design.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.865-873
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• 2017

Converter transformer is the key equipment of high voltage direct current transmission system. The solid suspending particles originating from the process of installation and operation of converter transformer have significant influence on the insulation performance of transformer oil, especially in presence of DC component in applied voltage. Under high electric field, the particles easily lead to partial discharge and breakdown of insulating oil. This paper investigated copper particle effect on the breakdown voltage of transformer oil at combined AC and DC voltage. A simulation model with single copper particle was established to interpret the particle effect on the breakdown strength of insulating oil. The experimental and simulation results showed that the particles distort the electric field. The breakdown voltage of insulating oil contaminated with copper particle decreases with the increase of particle number, and the breakdown voltage and the logarithm of particle number approximately satisfy the linear relationship. With the increase of the DC component in applied voltage, the breakdown voltage of contaminated insulating oil decreases. The simulation results show that the particle collides with the electrode more frequently with more DC component contained in the applied voltage, which will trigger more discharge and decrease the breakdown voltage of insulating oil.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.24-27
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• 2008

For high voltage DC-DC converters, the parallel operation of several high voltage source modules is necessary to reduce the material cost. In the conventional parallel operation with HDC module control unit, it is difficult to repair the HDC system for the failure of control unit. To overcome these problems, new parallel operating algorithm for high voltage DC-DC converter is presented. The proposed algorithm has no main control unit and each module can be selected as the master according to the operating conditions. Therefore, one of modules can be replaced as the master immediately when the previous master module is failed. In addition, the extension of extra modules can be simple.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.10
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• pp.1721-1726
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• 2016

4-types of coils were prepared by coating with polyamideimide (PAI) organic/inorganic hybrid. One type was made with original PAI vanish and the other 3-types were made of double layers, that was to say, high flexural PAI layer and high anti-corona PAI/nanosilica (15 wt%) layer. Drying temperature (T/D) were $220^{\circ}C$, $240^{\circ}C$, and $260^{\circ}C$, respectively and rectangular type coil for high-voltage rotating machine was used. DC and AC electrical breakdown tests were carried out in order to study the insulation properties according to T/D temperature and coil curvature (5, 15, and $25mm{\Phi}$). As the curvature increased, electrical breakdown voltage decreased and as T/D temperature decreased, electrical breakdown voltage increased.