• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.11
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• pp.97-106
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• 1992

In integrated circuits, protection circuits are required to protect the internal nodes from the harmful ESD(Electrostatic discharge). This paper discusses the characteristics of the circuit components in ESD protection circuitry in order to analyze the ESD phenomina, and the design methodalogy of ESD protection circuits, using test pattern with a variation of the number of diode and transistor. The test devices are fabricated using a 0.8$\mu$m CMOS process. SPICE simulation was also carried out to relate output node voltage and measured ESD voltage. With increasing number of diodes and transistors in protection circuit, the ESD voltage also increases. The ESD voltage of the bi-directional circuit for both input and output was 100-300[V], which in higher than that of only output(uni-directional) circuit. In addition, the ESD protection circuit with the diode under the pad region was useful for the reduction of chip size and parasitic resistance. In this case, ESD voltage was improved to a value about 400[V].

• Proceedings of the KIEE Conference
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• 2006.04b
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• pp.211-215
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• 2006

This paper present the Half-Bridge converter for low current output. In converter system, magnetic components are important devices used for energy storage, energy transfer, galvanic isolation and filtering. The proposed Half-Bridge converter is to reduce the number of magnetic components. The secondary rectification was discussed by comparison of center-tap type with primary center-core transformer winding and primary side-core transformer winding. A prototype featuring 400V input, 10V output, 400kHz switching frequency, and 100W output power.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.4
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• pp.569-577
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• 2009

Mobile information retrieval is an evolving branch of information retrieval that is centered on mobile and ubiquitous environments. In general, mobile devices are characterized by lightweight, low power, small memory, small display, limited input/output, low bandwidth, and so on. Some of these characteristics make it impossible to apply general information retrieval to mobile environments without any modification. In order to relieve this problem, we design and implement an information retrieval system for mobile devices like wireless phones, PDA and handheld devices. We use document summarization techniques to alleviate the limitation of small display and user profiles to retrieve the most proper documents for each individual user for personalized search. Futhermore we use meta-search to lighten some burdens visiting several portal sites. In this paper, we have implemented and demonstrated the proposed mobile information retrieval system on the domain of travel and received good evaluation from users subjectively.

• Journal of the Korea Society of Computer and Information
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• v.23 no.4
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• pp.107-114
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• 2018

Recently, various wearable personal devices such as a smart watch have been developed and these personal devices are being miniaturized. The user desires to receive new services from personal devices as well as services that have been received from personal computers, anytime and anywhere. However, miniaturization of devices involves constraints on resources such as limited input and output and insufficient power. In order to solve these resource constraints, this paper proposes a resource collaboration system which provides a service by composing sharable resources in the resource sharing environment like IoT. the paper also propose a method to infer and recommend user-customized resources among various sharable resources. For this purpose, the paper defines an ontology for resource inference. This paper also classifies users behavior types based on a user model and then uses them for resource recommendation. The paper implements the proposed method as a prototype system on a personal device with limited resources developed for resource collaboration and shows the effectiveness of the proposed method by evaluating user satisfaction.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.1054-1057
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• 2002

The design and fabrication of Q-band 3-stage monolithic microwave integrated circuit(MMIC) amplifier for WLAN are presented using 0.2$\square$ AIGaAs/lnGaAs/GaAs pseudomorphic high electron mobility transistor (PHEMT). In each stage of the MMIC, a negative feedback is used for both broadband and good stability. The measurement results are achieved as an input return loss under -4dB, an output return loss under -10dB, a gain of 14dB, and a PldB of 17dBm at Q-band(36～44GHz). These results closely match with design results. The chip size is 2.8${\times}$1.3mm$^2$. This MMIC amplifier will be used as the unit cell to develop millimeter-wave transmitters for use in wideband wireless LAN systems.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1146-1155
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• 2017

Normally, the artificial intelligence algorithms are widely applied to the optimal controller design. Then, it is expected that the best output performance is achieved. Unfortunately, when resulting controller parameters are implemented by using the practical devices, the output performance cannot be the best as expected. Therefore, the paper presents the optimal controller design using the combination between the state-space averaging model and the adaptive Tabu search algorithm with the new criteria as two penalty conditions to handle the mentioned problem. The buck-boost converter regulated by the cascade PI controllers is used as the example power system. The results show that the output performance is better than those from the conventional design method for both input and load variations. Moreover, it is confirmed that the reported controllers can be implemented using the realistic devices without the limitation and the stable operation is also guaranteed. The results are also validated by the simulation using the topology model of MATLAB and also experimentally verified by the testing rig.

• Journal of Power Electronics
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• v.12 no.2
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• pp.249-257
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• 2012

An interleaved PWM converter is proposed to implement the features of zero voltage switching (ZVS), load current sharing and ripple current reduction. The proposed converter includes two ZVS converters with a common clamp capacitor. With the shared capacitor, the charge balance of the two interleaved parts is automatically regulated under input voltage and load variations. The active-clamping circuit is used to realize the ZVS turn-on so that the switching losses on the power switches are reduced. The ZVS turn-on of all of the switching devices is achieved during the transition interval. The interleaved pulse-width modulation (PWM) operation will reduce the ripple current and the size of the input and output capacitors. The current double rectifier (CDR) is adopted in the secondary side to reduce output ripple current so that the sizes of the output chokes and capacitor are reduced. The circuit configuration, operation principles and design considerations are presented. Finally experimental results based on a 408W (24V/17A) prototype are provided to verify the effectiveness of the proposed converter.

• Journal of Information Technology Services
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• v.16 no.4
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• pp.1-13
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• 2017

This study examines how specific technology from Information and Communications Technology (ICT)-which plays a critical role in increasing productivity by promoting a spread of technology across the society though the use of big data, mobile or wearable devices-impacts of the productivity of society and productivity of added values, respectively. The impact of technology was studied from the perspective of efficiency levels of input. In order to provide an analysis, we have categorized ICT into 16 specific technologies and have set the number of companies and number of employees each as an input factor while setting the respective output and the output of added values as an output factor. Afterwards, we have applied data envelopment analysis (DEA) which is a form of nonparametric frontier analysis and measured the productivity and efficiency of added values for each technology. According to the analysis results, there were 2 technologies by the CRS standards, and 3 technologies by the VRS standards that showed relative efficiency levels. We have also presented some efficiency improvement strategies for specific technologies that revealed relative inefficiency and offered a reference set and projection point. In addition, we provide an analysis on scale efficiencies (SE), diminishing returns to scale (DRS), and increasing returns to scale (IRS) of each ICT.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.6
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• pp.424-432
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• 2018

This study presents a single-phase single-stage three-level AC/DC converter with a wide controllable output voltage. The proposed AC/DC converter is designed to extend the application of e-mobility, such as electric vehicles. The single-stage converter integrates a PFC converter and a three-level DC/DC converter, operates at a fixed frequency, and provides a wide controllable output voltage (approximately 200-430Vdc) with high efficiencies over a wide load range. In addition, the input boost inductors operate in a discontinuous mode to improve the input power factor. The switching devices operate with ZVS, and the converter's THD is small, especially at full load. The feasibility of the proposed converter is verified by the experimental results of a 1.5 kW prototype.

• Korean Journal of Optics and Photonics
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• v.4 no.3
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• pp.294-300
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• 1993

Monolithic NOR and INVERTER active optical logic devices inte- grated with surface-emitting microlasers, heterojunction photo- transistors(HPT) in parallel and resistors in series are characterized. The differential quantum efficiency of the typical AlGaAs superlattice microlaser integrated in the active optical logic devices is 15%. Current gain of the HPT is 57, when emitter-collector voltage and input optical power are 4 V and $50{\mu}W$, respectively. $57{\mu}W$ of output power from the active optical logic device decreases to zero when $47{\mu}W$ of input optical power is incident on the HPT part of the active logic device.