• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.4
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• pp.377-383
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• 1999

A new soft switching single stage AC-DC full bridge boost converter with unit input power factor and isolated output i is presented in this paper. Due to the use of a non-dissipative snubber on the primary side, a single stage high-power f factor isolated full bridge boost converter has a significant reduction of switching losses in the main switching devices. The non-dissipative snubber adopted in this study consists of a snubber capacitor Cr, a snubber inductor Cr, a fast r recovery snubber diode Dr' and a commutation diode Dp. This paper presents the complete operating principles, t theoretical analysis and experimental results.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.597-597
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• 2013

The resistive switching behaviors of Pt nanodisk on Nb-doped SrTiO3 single-crystal have been studied with conductive atomic force microscopy in ultra-high vacuum. The nanometer sizes of Pt disks were formed by using self-assembled patterns of silica nanospheres on Nb-doped SrTiO3 single-crystal semiconductor film using the Langmuir-Blodgett, followed by the metal deposition with e-beam evaporation. The conductance images shows the spatial mapping of the current flowing from the TiN coated AFM probe to Pt nanodisk surface on Nb：STO single-crystal substrate, that was simultaneously obtained with topography. The bipolar resistive switching behaviors of Pt nanodisk on Nb：STO single-crystal junctions was observed. By measuring the current-voltage spectroscopy after the forming process, we found that switching behavior depends on the charging and discharging of interface trap state that exhibit the high resistive state (HRS) and low resistive state (LRS), respectively. The results suggest that the bipolar resistive switching of Pt/Nb:STO single-crystal junctions can be performed without the electrochemical redox reaction between tip and sample with the potential application of nanometer scale resistive switching devices.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.63 no.6
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• pp.764-769
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• 2014

This paper describes sheath voltage limiter(SVL) transient characteristics by switching overvoltage considering single point bonding in underground transmission cables. The crossbonding system is generally used for grounding methods of underground transmission system. However, the single point bonding system is used in selective area which is difficult to consist of crossbonding major section. The sheath voltage limiters are connected between joints in the single point bonding. Specially, the high overvoltage might be generated in that section as well as the aging of sheath voltage limiter might be progressed by various electrical stress including lightning overvoltage, switching overvoltage and power frequency overvoltage. Therefore, in this paper, the switching overvoltage characteristics in underground cables are firstly analysed using EMTP simulation. Then, the switching overvoltage of sheath voltage limiter is also studied in single point bonding. Finally, the reduction method of sheath voltage limiter switching overvoltage is proposed by various simulation studies including circuit breaker operating order.

• Journal of Power Electronics
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• v.16 no.2
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• pp.498-511
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• 2016

This paper presents a single-phase five-level inverter controlled by two novel pulse width modulation (PWM) switching techniques. The proposed PWM techniques are designed based on minimum switching power loss and minimum total harmonic distortion (THD). In a single-phase five-level inverter employing six switches, the first proposed PWM technique requires four switches to operate at switching frequency and two other switches to operate at line frequency. The second proposed PWM technique requires only two switches to operate at switching frequency and the rest of the switches to operate at line frequency. Compared with conventional PWM techniques for single-phase five-level inverters, the proposed PWM techniques offer high efficiency and low harmonic components in the output voltage. The validity of the proposed PWM switching techniques in controlling single-phase five-level inverters to regulate load voltage is verified experimentally using a 100 V, 500 W laboratory prototype controlled by dspace 1103.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.268-275
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• 2015

This paper proposes a method of switching to improve power loss for the single-phase three-level NPC inverter. The conventional switching methods, which are called as the bipolar and unipolar switching methods, are used for single phase inverters using three-level topology. However, these switching method have disadvantage in the power loss. Because all of the switch are operated. To reduce the power loss of the three-level NPC inverter, clamp switching method is introduced in this paper. This way, one of the lag is fixed that switching loss is reduced. This paper analyzes and compares power losses of unipolar method and clamp method. The validity of the power loss analysis is verified through the simulation and experimental results.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.430-432
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• 2005

This paper presents a novel, single stage, isolated, three-phase switching rectifier capable of switching at high frequency. The circuit topology Provides zero-voltage switching for all switches, output voltage regulation, unity input power factor, all in a single power conversion stage. Operating principle and experimental results in the 48V/100A DC power supply of three-phase single stage method are presented.

• Corrosion Science and Technology
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• v.7 no.6
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• pp.307-314
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• 2008

The influence of a moist atmosphere on $90^{\circ}$ domain switching under a sustained electric field, stress corrosion cracking of an indentation crack in water and an aggressive solution, and the relation between penetrating crack propagation and domain switching were studied using $BaTiO_3$ single crystal. The results indicate that enlarging the domain switching zone and crack propagation could be facilitated by a moist atmosphere or an aggressive solution due to the indentation residual stress. A moist atmosphere exerts remarkable influence upon the polarization of $BaTiO_3$ single crystal under a sustained electric field, and the surface energy of the c domain was much lower than that of the a domain. Domain switching ahead of a penetrating indentation crack tip was an essential requirement for crack propagation under constant stress.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.256-260
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• 2001

This paper presents boost and buck and buck-boost DC-DC converter circuit topologies of high-frequency soft switching transition PWM chopper type DC-DC high power converters with a single auxiliary passive resonant snubber. In the proposed boost power converter circuits operating under a principle of ZCS turn-on and ZVS turn-off commutation schemes, the capacitor and inductor in the auxiliary passive resonant circuit works as the loss less resonant snubber. In addition to this, the switching voltage and current peak stresses as well as EMI and RFI noises can be basically reduced by this single passive resonant snubber. Moreover, it is proved that converter circuit topologies with a passive resonant snubber are capable of solving some problems of the conventional hard switching PWM processing based on high-ferquency pulse modulation operation principle. The simulation results of this converter are discussed as compared with the experimental ones. The effectiveness of this power converter with a single passive resonant snubber is verified by the 5kW experimental breadboad set up.

• Journal of Power Electronics
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• v.9 no.4
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• pp.623-630
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• 2009

This paper proposes a filter design guideline for grid-connected single-phase inverters. By analyzing the instantaneous voltage applied to the filter inductor, the switching ripple current through the filter inductor can be precisely calculated. Therefore, filter inductance can be designed accurately, which guaranties that the switching ripple current will be under the target value. The proposed filter design method is verified by experiment.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.194-195
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• 2013

This paper presents novel single-phase PWM AC-AC converters that can solve commutation problem in single-phase direct AC-AC converter without sensing input voltage polarity. By using the basic switching cell concept and coupled inductor, the proposed converter can be short and open-circuit without damping switching devices. A 120 W prototype is built and tested to verify performance of the proposed converter.