• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.18 no.3
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• pp.120-127
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• 2004

With the proliferation of nonlinear loads such as switching mode power supplies, high neurtral harmonic currents in three-phase four-wire distribution system have been observed. It has been known that the grounded impedance has an effect on the neutral current of a system which operates with harmonics present since the neutral conductor is grounded. On-site measurements of harmonic currents and voltages were made and the corresponding equivalent circuit was developed. The circuit model under study was simulated numerically and graphically through the use of the software MATLAB. Simulation results verifying the relationship between the neutral harmonic current and ground impedance are presented.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.5
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• pp.389-396
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• 2003

This paper describes a novel ac/dc power converter suitable for frequent output short-circuit faults. The output dc power of the proposed converter can be disconnected from the load within several hundred microseconds at the instant of short-circuit fault. The rising time of the dc load voltage is as small as several hundred microseconds, and there Is no overshoot of the dc voltage because the dc output fillet capacitors stay at a undischarged state. The proposed converter has the characteristics of a simplified structure, reduced cost, weight, and volume compared to the conventional power supplies for frequent output short-circuit. Analysis, simulations, and experiments are carried out to investigate the operation and usefulness of the proposed scheme.

• Proceedings of the KIPE Conference
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• 2008.10a
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• pp.130-132
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• 2008

In this paper, we have proposed a novel zero-voltage-switching (ZVS) soft-switching H-bridge inverter. Because the conventional H-Bridge inverter generates switching losses at turn on and off, the efficiency is reduced. The proposed inverter operates ZVS switching using an auxiliary switch and resonant circuit to improve the efficiency. in the DC-DC converter stage, it can reduce not only switching loss but also capacity and size of passive devices due to the resonant elements. DC-AC inverter stage supplies load with energy through the ZVS operation of 4 switches. A detail mode analysis of operating is in presented. We have presented the inverter topology, principle of operation and simulation results obtained from the PSIM simulator.

• Journal of Power Electronics
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• v.8 no.1
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• pp.35-50
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• 2008

A zero-voltage-transition (ZVT) pulse width modulated (PWM) converter is a PWM converter with a single main power switch that has an auxiliary circuit to help it turn on with zero-voltage switching (ZVS). There have been many ZVT-PWM converters proposed in the literature as they are the most popular type of ZVS-PWM converters. In this paper, the properties and characteristics of several types of ZVT-PWM converters are reviewed. A new type of ZVT-PWM converter is then introduced, and the operation of a sample converter of this type is explained and analyzed in detail. A procedure for the design of the converter is presented and demonstrated experimentally. The feasibility of the new converter is confirmed with results obtained from an experimental prototype. Conclusions on the performance of ZVT-PWM converters in general are made based on the efficiency results obtained from the experimental prototypes of various ZVT-PWM converters of different types.

• IEIE Transactions on Smart Processing and Computing
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• v.4 no.1
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• pp.44-50
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• 2015

This paper presents a high speed synchronous single inductor dual output boost converter using Type-III compensation for power management in smart devices. Maintaining multiple outputs from a single inductor is becoming very important because of inductor the sizes. The uses of high switching frequency, inductor and capacitor sizes are reduced. Owing to synchronous rectification this kind of converter is suitable for SoC. The phase is controlled in time sharing manner for each output. The controller used here is Type-III, which ensures quick settling time and high stability. The outputs are stable within $58{\mu}s$. The simulation results show that the proposed scheme achieves a better overall performance. The input voltage is 1.8V, switching frequency is 5MHz, and the inductor used is 600nH. The output voltages and powers are 2.6V& 3.3V and 147mW &, 230mW respectively.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.494-497
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• 2002

Conducted electromagnetic interference (EMI) from switch mode power supplies (SMPS) has become a major problem due to the proliferation of these devices employing dc-dc converters using standard pulse width modulation (PWM). In this paper, we proposed the sigma-delta modulation $({\sum}{\Delta}M)$ as an alternative switching technique to reduce the conducted EMI in SMPS. A comparative investigation on conducted EMI generated by PWM and ${\sum}{\Delta}M$ techniques are experimentally performed on a 300W Boost converter.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.2
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• pp.109-113
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• 2020

A power device is a component used as a switch or rectifier in power electronics to control high voltages. Consequently, power devices are used to improve the efficiency of electric-vehicle (EV) chargers, new energy generators, welders, and switched-mode power supplies (SMPS). Power device designs, which require high voltage, high efficiency, and high reliability, are typically based on MOSFET (metal-oxide-semiconductor field-effect transistor) and IGBT (insulated-gate bipolar transistor) structures. As a unipolar device, a MOSFET has the advantage of relatively fast switching and low tail current at turn-off compared to IGBT-based devices, which are built on bipolar structures. A superjunction structure adds a p-base region to allow a higher yield voltage due to lower R_DS (on) and field dispersion than previous p-base components, significantly reducing the total gate charge. To verify the basic characteristics of the superjunction, we worked with a planar type MOSFET and Synopsys' process simulation T-CAD tool. A basic structure of the superjunction MOSFET was produced and its changing electrical characteristics, tested under a number of environmental variables, were analyzed.

• Journal of Power Electronics
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• v.11 no.6
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• pp.914-921
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• 2011

Commencing with incandescent light bulbs, every load today creates harmonics. Unfortunately, these loads vary with respect to their amount of harmonic content and their response to problems caused by harmonics. The prevalent difficulties with harmonics are voltage and current waveform distortions. In addition, Electronic equipment like computers, battery chargers, electronic ballasts, variable frequency drives, and switching mode power supplies generate perilous amounts of harmonics. Issues related to harmonics are of a greater concern to engineers and building designers because they do more than just distort voltage waveforms, they can overheat the building wiring, cause nuisance tripping, overheat transformer units, and cause random end-user equipment failures. Thus power quality is becoming more and more serious with each passing day. As a result, active power filters (APFs) have gained a lot of attention due to their excellent harmonic compensation. However, the performance of the active filters seems to have contradictions with different control techniques. The main objective of this paper is to analyze shunt active filters with fuzzy and pi controllers. To carry out this analysis, active and reactive current methods ($i_d-i_q$) are considered. Extensive simulations were carried out. The simulations were performed under balance, unbalanced and non sinusoidal conditions. The results validate the dynamic behavior of fuzzy logic controllers over PI controllers.

• Proceedings of the KIEE Conference
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• 2006.07a
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• pp.460-461
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• 2006

Computer Loads can be found in all of modern society. The switching mode power supplies used in personal computers are major sources of harmonic currents. Harmonic currents can cause lots of harmonic problems such as disruption in computer performance. A series resonant filter is very effective in harmonic reduction for personal computer loads. Voltage sags are short duration reductions in rms voltage. The main causes of voltage sags are faults, motor starting, and transformer energizing. Personal computers are another example of devices sensitive to voltage sags. A serious voltage sag at the terminals way lead mis-operation of the equipment. This paper presents an in depth analysis to evaluate the effect of harmonics reduction based on the IEC 61000-3-2 and the effect of voltage sag using ITI curve by applying a series resonant filter for personal computer loads.

• Journal of Power Electronics
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• v.13 no.4
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• pp.619-625
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• 2013

Switched mode power supplies (SMPS) are power electronic circuits extensively used in a wide range of applications. High frequency switching operation of SMPS causes electromagnetic emissions and has the potential to interfere with system operation, which in turn has an impact on system performance. This makes electromagnetic compatibility (EMC) an important concern. In this paper, a new and simple spread spectrum technique is proposed by modulating chaotic pulse position modulation (CPPM) and pulse width modulation (PWM). The resulting CPWM is implemented to reduce the conducted EMI in SMPS. The proposed method is found to be effective in reducing conduction EMI. The effectiveness and simplicity of the proposed method on spreading those dominating frequencies is compared to the EMI mitigation technique using an external chaotic generator. Finally, the levels of conductive EMI with standard PWM, CPWM with an external chaos generator and the proposed method are experimentally verified to comply with the CISPR 22A regulations. The results confirm the effectiveness of the proposed method.