• Proceedings of the KIPE Conference
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• 1998.11a
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• pp.44-48
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• 1998

In the buck-boost DC-DC converter which is used at a certain situation such as in factories where loads often change a lot, the switches in the device make big energy loss in operating at Buck-Boost Mode due to hard switching and are affected by lots of stresses which decrease the efficiency rate of the converter. In order to improve this problem, to decrease the loss of snubber and switching, it has been investigated that zero voltage switching mode and zero current switching mode which make the operation of switches with soft switching. For the more sophisticated and advanced device, this paper is presented the Partial Resonant Soft Switching Mode Power Converter which is adapted the power converter having the partial resonant soft switching mode, that makes switches operate when the resonant current or voltage becomes zero by making the resonant circuit partially at turning on and off of the switches with suitable layout of the resonant elements and switch elements in the converter. Also, this paper includes the analysis and simulation of the Partial Resonant type Buck-Boost Chopper.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.323-326
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• 1999

For decrease the harmonic current components of the power source, a first method is insert the choke coil that used the choke input type rectifier, the booster chopper circuit and buck chopper circuit. And the several method are studying like as the PWM(Pulse Width Modulation) converter and the active filter type which is used the high frequency switching and the sinusoidal wave formed input current. In this type, there are many problem as a low efficiency, increased the noise, the high leakage current and cost up by the high frequency switching. For improve this problems, the partial resonan method is used on the booster inducter and lossles snubber condenser. This method decreased the distortion factor has lower harmonic components than the hard switching and there is no switching loss by the ZCS(Zero Current Switching) at switch turn-on and the ZVS(Zero Voltage Swithcing) at switch turn-off

• Proceedings of the KIPE Conference
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• 1998.11a
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• pp.39-43
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• 1998

A large number of soft switching topologies included a resonant circuit have been proposed. But these circuits increase number of switch in circuit and complicate sequence of switching operation. In this paper, the authors propose power conversion system, DC-AC inverter of high efficiency and high power factor with soft switching mode by partial resonant method. The switching devices in a proposed circuits are operated with soft switching by the partial resonant method, that is, PRS2MPC (Partial Resonant Soft Switching Mode Power Converter). The result is that the switching loss is very low and the efficiency of system is high. And the snubber condenser used in partial resonant circuit makes charging energy regenerated at input power source for resonant operation.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.614-617
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• 1999

To achieve high efficiency in high power and high frequency applications, reduction of switching losses and noise is very important. In this paper, an improved zero voltage switching forward dc/dc converter is proposed. The proposed converter is constructed by using energy recovery snubbers in parallel with the main switches and output diodes of the conventional forward dc/dc converter. Due to the use of the energy recovery snubbers in the primary and secondary side, the proposed converter achieves zero-voltage-switching turn-off without switching losses for switching devices and output rectification diodes. The complete operating principles and experimental results will be presented.

• Proceedings of the KIEE Conference
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• 2003.07e
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• pp.166-170
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• 2003

This paper deals with the power loss analysis of voltage source type space voltage vector modulated soft switching inverter, and proposed the new voltage vector correction principle during one sampling period on realize high quality cutput voltage waveforms for two soft-swiching approches. The operating pinciple of a single active auxiliary resonant DC link snubber circuit is described. Moreover, the effectiveness of soft switching inverter operating under the corrected voltage pattern is proved on the basis of simulation and experimental results.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.160-162
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• 1993

This paper proposes a new converter for switched reluctance motors using a Boost converter in conjunction with a Buck converter. The proposed converter has a unity power factor(hereafter referred to an UPF) in the ac input regardless of the load variations. Moreover, compared to the conventional converter topologies, the total system efficiency is improved by introducing choppingless voltage control methods in the machine side converter and an energy recovery snubber in the pre-voltage regulation stage, respectively.

• Proceedings of the KIEE Conference
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• 1993.11a
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• pp.148-150
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• 1993

The IGBT(Insulated Gate Bipolar Transistor) is a power semiconductor device that has gained acceptance among power electronic circuit design engineers for motor drive and Power converter applications. The device-circuit interaction of power insulated gate bipolar transistor for a series-inductor load, both with and without a snubber are, simulated. An analytical model for the transient operation of the IGBT is used in conjunction with the load circuit state equations for the simulations.

• Proceedings of the IEEK Conference
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• 2008.06a
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• pp.1103-1104
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• 2008

In this paper, authors propose a novel step-up AC-DC chopper operated with power factor correction (PFC) and with high efficiency. The proposed chopper behaves with discontinuous current control (DCC) of input current. The input current waveform in the proposed chopper is got to be a discontinuous sinusoid form in proportion to magnitude of ac input voltage under the constant duty cycle switching. Therefore, the input power factor is nearly unity and the control method is simple. In the general DCC chopper, the switching devices are turned-on with the zero current switching, but turn-off of the switching devices is switched at current maximum value. To achieve a soft switching of the switching turn-off, the proposed chopper is used a new partial resonant circuit. The result is that the switching loss is very low and the efficiency of chopper is high.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.1420-1423
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• 1990

DC series motor has been widely applicated in industry due to many advantageous characteristics, such as high starting torque, easy construction of its controller, and cost economy, etc.. However, by high starting current, excessive surge voltage, and so on, many problems which could make engineers relinguish to use it are induced. In this paper, various protection methods for power circuit are discussed. Particularly, a new proposed snubber circuit which consists of two diodes, one capacitor, and a resistor increases the performance with respect to the suppression of the surge voltage. Furthermore, the plugging algorithm, by checking the armature current and voltage and controlling the field coil current, is designed and implemented. Also, these methods and algorithms were applicated in electric vehicle, and we could find its stability to be considerably improved.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.1438-1444
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• 2007

Standard Gate Turn Off (GTO) Thyristor drive technology results in inhomogeneous turn-on and turn-off transients which in turn needs costly dv/dt and di/dt snubber circuits. Added to this GTO is bulky in size, needs external cooling, slower switching time etc. The development of high voltage Insulated Gate Bipolar Transistor (IGBT) have given new device advantage in the areas where they compete with conventional GTO technology. Indian Railway has developed first IGBT based traction converter and was commissioned in November 2006. Some of the supremacy of IGBT are smaller in size, no external cooling is required, built in power supply which enhances reliability, lower switching losses which leads to higher efficiency, reduced gate drive, high frequency operation in real time etc. These advantages are highlighted along with IGBT Traction system in operation.