• Journal of Electrical Engineering and Technology
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• v.9 no.6
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• pp.2168-2180
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• 2014

In this paper, a generalized power loss algorithm for multilevel neutral-point clamped (NPC) PWM inverters is presented, which is applicable to any level number of multilevel inverters. In the case of three-level inverters, the conduction loss depends on the MI (modulation index) and the PF (power factor), and the switching loss depends on a switching frequency, turn-on and turn-off energy. However, in the higher level of inverters than the three-level, the loss of semiconductor devices cannot be analyzed by conventional methods. The modulation depth should be considered in addition, to find the different conducting devices depending on the MI. In a case study, the power loss analysis for the three- and five-level NPC inverters has been performed with the proposed algorithm. The validity of the proposed algorithm is verified by simulation for the three-and five-level NPC inverters and experiment for three-level NPC inverter.

• Proceedings of the KIPE Conference
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• 2004.07a
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• pp.239-243
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• 2004

This paper presents a proper switching angle calculation method of Switched Reluctance Motor (SRM) for drill. The characteristic of SRM drive is very related to the scheduling of commutation angle and current waveforms. Therefore, a selection method of switching turn-on and turn-off angle is suggested for adaptational operation of SRM with varied rotor speed and load. Simulation and experimental results are presented for the validation of proposed method.

• Journal of Power Electronics
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• v.16 no.5
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• pp.1669-1677
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• 2016

A new auxiliary circuit for boost, buck, buck-boost, Cuk, SEPIC, and zeta converters is introduced to provide soft switching for pulse-width modulation converters. In the aforementioned family of DC-DC converters, the main and auxiliary switches turn on under zero current transition (ZCT) and turn off with zero voltage and current transition (ZVZCT). All diodes commutate under soft switching conditions. On the basis of the proposed converter family, the boost topology is analyzed, and its operating modes are presented. The validity of the theoretical analysis is justified by the experimental results of a 100W, 100 kHz prototype. The conducted electromagnetic emissions of the proposed boost converter are measured and found to be lower than those of another ZCT boost converter.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.211-214
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• 2001

This paper introduces a ZC-ZVS PWM(Pulse-Width -Modulation) boost converter. The IGBT(main switch) of the proposed converter is always switched at ZCS and soft switching of MOSFET(auxiliary switch) as well. Therefore, the proposed converter minimized the turn on/turn off switching losses of switches and reduced conduction losses by using IGBT switch. Moreover, using paralleled IGBT-MOSFET switch overcame the switching frequency limitation. Therefore high power density system can be realized. As mentioned above, the characteristics are verified through experimental results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.28 no.1
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• pp.36-44
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• 2014

The conventional central photo voltaic inverters have several problems. First, shadow problem in each solar panel, and high DC voltage problem from each panel because of concentration to one central inverter. Therefore, module integrated inverter is proposed to solve these problems. The inverter should be small and cost effective. The cost and size in the inverter depend on the inductor. So the switching frequency should be increased to reduce the inductor and total size, but there is a problem in efficiency because of the losses in turn-on and turn-off. In the paper, the critical conduction mode(CRM) switching method is adopted to reduce the switching loss and interleaving method is proposed to increase the efficiency in Flyback converter. Finally, the validity of the proposed scheme is investigated with simulated and experimental results for a prototype system rated at 200W.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.815-817
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• 1993

In this paper, it is considered spike voltage that is generated by ignoring the recovery time of switching device, turn on and turn off time. In the same principle, this spike voltage will be applicable to diode recovery time. The spike voltage causes to break down insulation of input transformer. So, we will show how to remove spike voltage by optimizing value of R and C and using switching diode which have fast recovery time.

• Proceedings of the KIEE Conference
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• 1995.07a
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• pp.188-190
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• 1995

This paper describes a soft switching using discontinuous inductor current. The soft switching snubber circuit provides ZCS and ZVS for main switch. For high power applications, the input ractifier is fed from a three-phase ac source. The Conventional switching method is hard switching technics, because of the device turn off is ocurred in maximum reactor current. In this time, switching losses are maximised by the hard switching. In generally, soft switching technique has been adjusted with the snubber condenser in order to compensates for this losses. So, it was compared hard switching with soft switching which has proposed in this paper for switching losses, distortion factor by the simulation.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.2
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• pp.152-158
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• 1999

Due to high power ratings and low conduction loss, the TGBT has become more attractive in switching power supplies. However, its lower turn-on and turn-off characteristics than those of MOSFET cause severe switching loss and s switching frequency limitation. This paper proposes 2.4kW. 48V. high efficiency half-bridge DC-DC converter using p paralleled TGBT-MOSFET switch concept to use the merits of TGBTs and MOSFETs. Tn parallel switches. each of I TGBT and MOSFET plays its part during on-periods and switching instants. The switching loss is analyzed by l linearized modelling and the operation of the converter are investigated by simulation results.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.3
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• pp.146-152
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• 2015

In this paper, we propose a boost DC-DC converter using a modification of the passive auxiliary resonant snubber circuit with a DC-DC converter in a typical active auxiliary resonant snubber-bridge inverter. The proposed boost DC-DC converter is small compared to the DC-DC converter according to the soft-switching scheme that requires a general auxiliary switch by realizing the soft switching operation as a DC-DC converter which does not require an auxiliary switch. It is light-weight, switch the turn-on and turn-off switching loss at the time of the superposition of the voltage and current is extremely small, so small. And the reduction of the surge voltage and current of the switch. In addition, the proposed boost DC-DC converter has a high efficiency over a wide load characteristics change area than conventional hard switching PWM boost converter using an RC snubber loss.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.9
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• pp.576-583
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• 2004

This paper presents a buck circuit topology of high-frequency with a single switching device. It solved the problem which arised from hard-switching in high-frequency using a resonant snubber and operating under the principle of ZCS turn-on and ZVS turn-off commutation schemes. In the existing circuit, it has the voltage stress that is almost twice of input voltage in a free-wheeling diode. In the proposed circuit, it has the voltage stress that is lower than input voltage with modifing a location of free -wheeling diode. In this paper, it expained the circuit operation of each mode and analyzed feedback-loop stabilization. Also it confirmed the waveform of each mode with simulation result. The experiment result verified the simulation waveform and compared the voltage stress of a free -wheeling diode in the exsiting circuit with the voltage stress of that in the proposed circuit. Moreover, it compares and analyzes the proposed circuit's efficiency with the hard-switching circuit's efficiency according to the change of load current.