• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.1
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• pp.67-75
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• 2011

This paper investigates the radiated emission from the enclosure aperture, when the enclosure contains a 4-layer PCB and the PCB is driven by a pulse train additive with the switching noise from an active device. Radiated emission characteristics with and without switch noise cases, respectively, are analyzed by changing the PCB location and the slot direction. The equivalent circuit of a DC-DC converter is used to simulate the switching noise of active device. Also, MWS simulation results are directly connected to the ADS simulator as a 2-port block. The simulated results are compared with the measured ones.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.326-326
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• 2014

It has been known since the mid 1960s that Ag can be photodissolved in chalcogenide glasses to form materials with interesting technological properties. In the 40 years since, this effect has been used in diverse applications such as the fabrication of relief images in optical elements, micro photolithographic schemes, and for direct imaging by photoinduced Ag surface deposition. ReRAM, also known as conductive bridging RAM (CBRAM), is a resistive switching memory based on non-volatile formation and dissolution of a conductive filament in a solid electrolyte. Especially, Ag-doped chalcogenide glasses and thin films have become attractive materials for fundamental research of their structure, properties, and preparation. Ag-doped chalcogenide glasses have been used in the formation of solid electrolyte which is the active medium in ReRAM devices. In this paper, we investigated the nature of thin films formed by the photo-dissolution of Ag into Ge-Se glasses for use in ReRAM devices. These devices rely on ion transport in the film so produced to create electrically programmable resistance states [1-3]. We have demonstrated functionalities of Ag doped chalcogenide glasses based on their capabilities as solid electrolytes. Formation of such amorphous systems by the introduction of Ag+ ions photo-induced diffusion in thin chalcogenide films is considered. The influence of Ag+ ions is regarded in terms of diffusion kinetics and Ag saturation is related to the composition of the hosting material. Saturated Ag+ ions have been used in the formation of conductive filaments at the solid electrolyte which is the active medium in ReRAM devices. Following fabrication, the cell displays a metal-insulator-metal structure. We measured the I-V characteristics of a cell, similar results were obtained with different via sizes, due to the filamentary nature of resistance switching in ReRAM cell. As the voltage is swept from 0 V to a positive top electrode voltage, the device switches from a high resistive to a low resistive, or set. The low conducting, or reset, state can be restored by means of a negative voltage sweep where the switch-off of the device usually occurs.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.5
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• pp.419-426
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• 2002

A new active lossless snubber for half-bridge dual converter(that is called'dual converter') is proposed in this paper It features soft switching(ZVS) as well as turn-off snubbing in both main and auxiliary switches. Therefore, it helps the dual converter to operate at the higher frequency with a higher efficiency and smaller-sized reactive components. Moreover, since it uses parasitic components, such as leakage inductances and switch output capacitances etc, to achieve the ZVS of power switches, it has simpler structure and lower cost of production. The operational principle, theoretical analysis, and design consideration are presented. To confirm the operation, features, and validity of the proposed circuit, experimental results from a 200w, 24V/DC-200V/DC proto-type are presented.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.4
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• pp.366-373
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• 2005

This paper presents two new circuit topologies of the dc busline side active resonant snubber assisted voltage source high frequency link soft switching PWM full-bridge dc-dc power converters acceptable for either utility ac 200V-rms or ac 400V-rms input grid. These high frequency switching dc-dc converters proposed in this paper are composed of a typical voltage source-fed full-bridge PWM inverter, high frequency transformer with center tap, high frequency diode rectifier with inductor input filter and dc busline side series switches with the aid of a dc busline parallel capacitive lossless snubber. All the active switches in the full-bridge arms as well as dc busline snubber can achieve ZCS turn-on and ZVS turn-off transition commutation with the aid of a transformer leakage inductive component and consequently the total switching power losses can be effectively reduced. So that, a high switching frequency operation of IGBTs in the voltage source full bridge inverter can be actually designed more than about 20 kHz. It is confirmed that the more the switching frequency of full-bridge soft switching inverter increases, the more soft switching PWM dc-dc converter with a high frequency transformer link has remarkable advantages for its power conversion efficiency and power density implementations as compared with the conventional hard switching PWM inverter type dc-dc power converter. The effectiveness of these new dc-dc power converter topologies can be proved to be more suitable for low voltage and large current dc-dc power supply as arc welding equipment from a practical point of view.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.10 no.11
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• pp.5400-5418
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• 2016

Femtocells are envisioned as a key solution to embrace the ever-increasing high data rate and thus are extensively deployed. However, the dense and random deployments of femtocell access points (FAPs) induce severe intercell inference that in turn may degrade the performance of spectral efficiency. Hence, unrestrained proliferation of FAPs may not acquire a net throughput gain. Besides, given that numerous FAPs deployed in ultra-dense networks (UDNs) lead to significant energy consumption, the amount of FAPs deployed is worthy of more considerations. Nevertheless, little existing works present an analytical result regarding the optimal FAP density for a given User Equipment (UE) density. This paper explores the realistic scenario of randomly distributed FAPs in UDN and derives the coverage probability via Stochastic Geometry. From the analytical results, coverage probability is strictly increasing as the FAP-to-UE ratio increases, yet the growing rate of coverage probability decreases as the ratio grows. Therefore, we can consider a specific FAP-to-UE ratio as the point where further increasing the ratio is not cost-effective with regards to the requirements of communication systems. To reach the optimal FAP density, we can deploy FAPs in line with peak traffic and randomly switch off FAPs to keep the optimal ratio during off-peak hours. Furthermore, considering the unbalanced nature of traffic demands in the temporal and spatial domain, dynamically and carefully choosing the locations of active FAPs would provide advantages over randomization. Besides, with a huge FAP density in UDN, we have more potential choices for the locations of active FAPs and this adds to the demand for a strategic sleeping policy.

• Journal of Electrical Engineering and Technology
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• v.13 no.1
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• pp.143-151
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• 2018

In this paper, a novel hybrid configuration combining a phase-shift full-bridge (PSFB) and a half-bridge resonant LLC converter is proposed for the On-Board Charger of Electric Vehicles (EVs). In the proposed converter, the PSFB converter shares the lagging-leg switches with half-bridge resonant converter to achieve the wide ZVS range for the switches and to improve the efficiency. The output voltage is modulated by the effective-duty-cycle of the PSFB converter. The proposed converter employs an active reset circuit composed of an active switch and a diode for the transformer which makes it possible to achieve zero circulating current and the soft switching characteristic of the primary switches and rectifier diodes regardless of the load, thereby making the converter highly efficient and eliminating the reverse recovery problem of the diodes. In addition an optimal power sharing strategy is proposed to meet the specification of the charger and to optimize the efficiency of the converter. The operation principle the proposed converter and design considerations for high efficiency are presented. A 6.6 kW prototype converter is fabricated and tested to evaluate its performance at different conditions. The peak efficiency achieved with the proposed converter is 97.7%.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.6
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• pp.539-546
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• 1999

A new integrated single-stage zero current switched(ZCS) quasi resonant convertedQRC) for the IX)wer f factor correction(PFCl converter is introduced in this paper. The power factor correction can be achieved by t the discontinuous conduction mod$\varepsilon$(DCM) operation of an input current. The proposed converter has the c characteristics of the good IX)wer factor, 10씨 line current harmonics, and tight output regulation. Furthern10re, t the ringing effect due to the output capacitance of the main switch can be eliminated by use of‘ active clamp c circuit. Therefore, the proIX)sed converter is expecttc'(] to be suitable for a compact power converter with a t tightly regulated output voltage requiring a switching frequency of more than several hundrtc'(]s kHz.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2006.05a
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• pp.399-402
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• 2006

This paper presents a new circuit topology of dc bus line switch-assisted half-bridge soft switching PWM inverter type dc-dc converter for arc welder. The proposed power converter is composed of typical voltage source half-bridge high frequency PWM inverter with a high frequency transformer link in addition to dc bus line side power semiconductor switching devices fer PWM control scheme and capacitive lossless snubbers. All the active power switches in the half-bridge arm and dc bus lines can achieve ZCS turn-on and ZVS turn-off commutation operation and consequently the total turn-off switching losses can be significantly reduced. As a result, a high switching frequency of using IGBTs can be actually selected more than about 20 kHz. The effectiveness of this new converter topology is proved for low voltage and large current dc-dc power supplies such as arc welder from a practical point of view.

• Journal of Communications and Networks
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• v.1 no.3
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• pp.189-200
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• 1999

For admitting a hard real-time connection to an ATM network, it is required that the end-새둥 delays of cells belong-ing to the connection meet their deadlines without violating the guarantees already provided to the currently active connections. There are two kinds of methods to analyze the end-to-end delay in an ATM network. A decomposed method analyzes the worst case delay for each switch and then computes the total delay as the sum of the delays at individual switches. On the other hand, an integrated method analyzes all the switches involved in an inte-grated manner and derives the total delay directly. In this paper, we present an efficient and effecitive integrated method to compute the end-to-end delay. We evaluate the network performance under different system parameters and we compare the performance of the proposed method with the conventional decomposed and other integrated methods [1], [3], [5]-[9].

• Journal of the Institute of Convergence Signal Processing
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• v.3 no.3
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• pp.70-75
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• 2002

This paper proposes new single stage power factor correction (PFC) full bridge converter. The proposed converter is combined previous ZVS full bridge DC/DC converter with two inductors, two diodes, two magnetic coupling transformer for PFC. This process of power is isolated from the source and also regulate stable DC output voltage in a category. In this topology, the voltage stress of main switches is reduced by zero voltage switching. Moreover, the proposed converter doesn't need active PFC switch and auxiliarly circuits, like control and gating board, so it could decrease the size and cost and increase the efficiency.