• Journal of IKEEE
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• v.13 no.4
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• pp.82-88
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• 2009

This paper is analyzed for a step up-down DC/DC chopper of high efficiency added electric isolation. The converters of high efficiency are generally made that the power loss of the used semiconductor switching devices is minimized. To achieve high efficiency system, the proposed chopper is constructed by using a partial resonant circuit. The control switches using in the chopper are operated with soft switching by partial resonant method. The control switches are operated without increasing their voltage and current stresses by the soft switching technology. The result is that the switching loss is very low and the efficiency of the chopper is high. The proposed chopper is also added electric isolation which is used a pulse transformer. When the power conversion system is required electric isolation, the proposed chopper is adopted with the converter system development of high efficiency. The soft switching operation and the system efficiency of the proposed chopper are verified by digital simulation and experimental results.

• Journal of IKEEE
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• v.17 no.3
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• pp.267-274
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• 2013

This paper presents a design of LLC resonant converter IC for LED backlight unit based on PFM/PWM dual-mode feedback. Dual output LLC resonant architecture with a single inductor is proposed, where the master output is controlled by the PFM and slave output is controlled by the PWM. To regulate the master output PFM is used as feedback to control the frequency of the power switch. On the other hand, PWM feedback is used to control the pulse width of the power switch and to regulate the slave output. This chip is fabricated in 0.35um 2P3M BC(Bipolar-CMOS-DMOS) Process and the die area is $2.3mm{\times}2.2mm$. Current consumptions is 26mA from 5V supply.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.45 no.4
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• pp.60-67
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• 2008

This paper presents a new full-bridge soft switching PWM DC-DC converter circuit topology that adding two switcher, two lossless snubber quasi-resonance capacity, two diode to power source for general welding machine. This half bridge soft switching Is low voltage hight current output that first coil current is smaller than second coil current in high frequency transformer can be obtained with decreasing path loss in conventional DC bus line switcher. As it operate ZCS/ZVS in full range, high frequency, high efficiency and high output are implemented at low voltage and high DC current switching power supplies. All of this items are got from simulation and the result of experiment. If make up for the weak points of this proposed circuit, it will be used more easily for next generation TIG, MIG and MAG type of arc-welding machine.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.6
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• pp.26-33
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• 2008

This paper presents a new full-bridge soft switching PWM DC-DC converter circuit topology that adding one switcher, one lossless snubber quasi-resonance capacity to power source for general welding machine This full-bridge soft switching DC-DC convoter· topology can applicable 600[V] switching device (IGBT)incase of AC 400[V] common power source because the voltage of active switcher is 1/2 of DC bus line voltage. And low voltage hight current out)ut that first coil current is smaller than second coil current in high frequency transformer can be obtained with decreasing path loss in conventional DC bus line switcher. As it operate ZCS/ZVS in full range, high frequency, high efficiency and high output are implemented at low voltage and high DC current switching power supplies. All of this items are got from simulation and the result of experiment. If make up for the weak points of this proposed circuit, it will be used more easily for next generation TIG, MIG and MAG type of arc-welding machine.

• Journal of Internet of Things and Convergence
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• v.8 no.2
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• pp.7-12
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• 2022

The main cause of cable accidents is the accelerated deterioration of the cable itself or internal and external electrical, mechanical, chemical, thermal, moisture intrusion, etc., which reduces insulation performance and causes insulation breakdown, leading to cable accidents. Insulation deterioration can occur even when there is no change in the appearance of the cable, so there is a difficulty in preventing cable accidents due to insulation deterioration. Since cable accidents can occur in areas with poor insulation due to the effects of overvoltage and overcurrent, it is necessary to comprehensively analyze transformers and circuit breakers, and ground faults caused by phase-to-phase imbalance. Ground fault accidents due to insulation breakdown of cables can occur due to defects in the cable itself and poor cable construction, as well as operational influences, arcs during operation of electrical equipment (switchers, circuit breakers, etc.). analysis is needed. This study intends to examine the causes of cable accidents through analysis of cable accidents that occurred in a manufacturing factory.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.4
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• pp.373-379
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• 2005

In this paper, the control algorithm of DC source device for inverter starting is proposed and the control method for compensating unbalance system source on operating time in the voltage type PWM converter with driving and regenerative faculty is suggested. The maintaining way of balancing condition for converter of AC source is used the compensating unbalanced status by current control loop. Because it is possible that the unbalanced System control is used to leakage transformer not equaled reactance by each phase in rectifier system, the proposed H/W and control algorithm of rectifier system is contributed to minimize of device and rising efficiency.

• Journal of the Korean Institute of Telematics and Electronics
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• v.5 no.1
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• pp.13-25
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• 1968

A detailed analysis of the transistor wide-band feedback amplifiers using the hybrid-$\pi$ equivalent circuit has been made. It is considered both for the low freqnency and for the high frequency. The expressions of the gain, bandwidth. input impedance and output impedance have been presented. It is shown that a series feedback amplifier should be driven from the voltage source and should drive into the low resistance load, and a shunt feedback amplifier should be driven from the current source and should drive into the high resistance load. It is also shown that these stages can be coupled without use of the buffer stage or coupling transformer.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.121-122
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• 2013

본 논문에서는 수출형 소 용량 태양광 인버터를 설계, 제작하였으며, 실제 제품을 제작하였다. 해당 제품은 VDE-AR-N_4105 및 VDE V 0126-1-1규정에 준하는 무변압기 방식 태양광 인버터로서 안정적이며 신뢰성 있는 동작을 할 수 있도록 절연레벨, 누설전류 및 기타 계통의 안정성 판단을 2개의 CPU에서 동시에 감시하도록 설계하였다. 또한 높은 IP등급을 만족하도록 설계되어 실외에서도 안정적이고 신뢰성 있는 동작을 할 수 있도록 설계하였다.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.12
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• pp.1111-1117
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• 2008

A transformer type superconducting fault current limiter (SFCL) is one of the fault current limiters which have been proposed to reduce the fault current in the transmission lines. This paper proposes the new circuit configuration of a transformer type SFCL and also investigates the operating characteristics of the transformer type SFCL containig the resistor in the tertiary winding. The proposed SFCL contains the resistor in the tertiary winding. The newly inserted resistor can divert the power which the High-Tc superconducting has to bear. Because the resistor in the tertiary winding relieves the power of the High-Tc superconducting, it is possible that the proposed transformer type SFCL can decrease the more larger fault current than the conventional SFCL with the same High-Tc superconducting. And the cost of the proposed transformer type SFCL can be reduced.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1167_1168
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• 2009

This paper presents new configuration of a.c. traction power supply system. The proposed system includes autotransformer with variable tab. The voltage drop in traction power supply system can be reduced due to tap change of autotransformer. In this paper, fault current and Impedance is investigated, when fault occurs in traction power supply system.