• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.263-266
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• 2009

In the photovoltaic applications, MPPT(maximum power point tracking) method is essential due to the non-lineality of photovoltaic output characteristics. To ensure stable tracking response, two sensors are required in conventional popular MPPTs. In modularized PV system as an AC module system, the cost of a sensor can have an effect on entire system cost because a power conditioning device is connected in a PV module. Because only a current sensor is required for proposed MPPT, it is helpful in the cost reduction point of view. In this paper, a novel MPPT using current sensor is proposed In the proposed MPPT, the voltage is derived from sensed current value. The proposed method is verified by simulation results.

• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.2
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• pp.18-22
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• 2001

The thin films of high permitivity in ferroelectric materials using a capacitor are applied to DRAMs and FRAMs. (Ba, Sr)TiO$_3$ thin as ferroelectric materials were prepared by the sol-gel method and made by spin-coating on the Pt/Sio$_2$/Si substrate at 4,000 [rpm] for 10 seconds. The structural characteristics of the surface were analyzed by fractal dimension. The thickness of BST ceramics thin films was about 260∼280 [nm]. The property of the leakage current was stable with 10-9∼10-11[A] when the applied voltage was 0∼3[V]. BST thin films ha low leakage current properties when fractal dimension was low and a coating area was high.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.53 no.6
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• pp.312-315
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• 2004

The monolayer of oxygen atoms sandwiched between the adjacent nanocrystalline silicon layers was formed by ultra high vacuum-chemical vapor deposition (UHV-CVD). This multilayer Si-O structure forms a new type of superlattice, semiconductor-atomic superlattice (SAS). According to the experimental results, high-resolution cross-sectional transmission electron microscopy (HRTEM) shows epitaxial system. Also, the current-voltage (Ⅰ-Ⅴ) measurement results show the stable and good insulating behavior with high breakdown voltage. It is apparent that the system may form an epitaxially grown insulating layer as possible replacement of silicon-on-insulator (SOI), a scheme investigated as future generation of high efficient and high density CMOS on SOI.

• Proceedings of the IEEK Conference
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• 1999.06a
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• pp.911-913
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• 1999

Shallow Trench Isolation (STI) has become the most promising isolation scheme for ULSI applications. The stress of STI structure is one of several factors to degrade characteristics of a device. The stress contours or STI structure vary with the trench depth. Isolation characteristics of STI was analyzed as the depth of trench varied. And transistor characteristics was compared. Isolation punch-through voltage for n$^{＋}$ to pwell and p$^{＋}$ to nwell increased as trench depth increased. n$^{＋}$ to pwell leakage current had nothing to do with trench depth but n$^{＋}$ to pwell leakage current decreased as trench depth increased. In the case of transistor characteristics, short channel effect was independent on trench depth and inverse narrow width effect was greater for deeper trenches. Therefore in order to achieve stable device, it is important to minimize stress by optimizing trench depth.

• KIEE International Transactions on Electrophysics and Applications
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• v.11C no.3
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• pp.58-62
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• 2001

Since Metallo-Porphyrin (MP) is very interesting compound due to its unique electronic and redox properties and it is also chemically and thermally stable, MP has been studied for potential memory and switching devices. In this study, thin films of 5,10,15,20-Tetrakis-Octadecyloxymethylphenyl-Porphyrin-Zn(II) were prepared by the Langmuir-Blodgett (LB) method and characterized by using UV/vis absorption spectroscopy and cyclic voltammetry. It was found that the proper transfer surface pressure for film deposition was 25 mN/m and the limiting area per molecule was 135 ${\AA}^2$/molecule. The current-voltage (I-V) characteristics of these films were investigated. Further details on the electrical properties of Porphyrin-Zn(II) derivative films will be discussed.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.3
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• pp.77-80
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• 2003

An innovative ozonizer has been developed using a high frequency, surface discharge and a high purity Ti-Si-AI ceramic catalyst as a dielectric component. Using a type of thin film, a thin cylindrical compound ceramic catalyst layer was adhered to the outside surface of its inner electrode. An alternating current (AC) exciting voltage with frequencies from 0.6 KHz to 1.0 KHz and peak-to-peak voltages of 4-6 ㎸ was applied between the electrodes to produce a stable high-frequency silent discharge. A substantial reduction of the exciting voltage was also enabled by means of a thin Ti-Si-Al ceramic catalyst tube. As a result, the ozonizer can effortlessly obtain the required ozone concentration (50-60 g/$m^2$ for oxygen) and high ozone efficiency consumption power (180 g/kWh for oxygen) with-out the assistance of any particular methods. For purposes of this experiment, oxygen gas temperature was set at 2$0^{\circ}C$, with an inner reactor pressure of 1.6 atm at 600 Hz and a flow rate of 2 l/min.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.180-183
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• 2003

The monolayer of oxygen atoms sandwitched between the adjacent nanocrystalline silicon layers was formed by ultra high vacuum-chemical vapor deposition (UHV-CVD). This multi-layer Si-O structure forms a new type of superlattice, semiconductor-atomic superattice (SAS). According to the experimental results, high-resolution cross-sectional transmission electron microscopy (HRTEM) shows epitaxial system. Also, the current-voltage (I-V) measurement results show the stable and good insulating behavior with high breakdown voltage. It is apparent that the system may form an epitaxially grown insulating layer as possible replacement of silicon-on-insulator (SOI), a scheme investigated as future generation of high efficient and high density CMOS on SOI.

• Journal of Power Electronics
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• v.17 no.1
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• pp.272-281
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• 2017

The DC circuit breaker is essential for supplying stable DC power with the advent of DC transmission/distribution and sensitive loads. Compared with mechanical circuit breakers, which must interrupt a very large fault current due to their slow breaking capability, a solid-state circuit breaker (SSCB) can quickly break a fault current almost within 1 [ms]. Thus, it can reduce the damage of an accident a lot more than mechanical circuit breakers. However, previous DC SSCBs cannot perform the operating duty, and are not economical because many SCR are required. Therefore, this paper proposes a new DC SSCB suitable for DC grids. It has a low semiconductor conduction loss, quick reclosing and rebreaking capabilities. As a result, it can perform the operating duties of reclosing and rebreaking. The proposed DC SSCB is designed and implemented so that it is suitable for home dc distribution at a rated power of 5 [kW] and a voltage of 380 [V]. The operating characteristics are confirmed by simulation and experimental results. In addition, this paper suggests design guidelines so that it can be applied to other DC grids. It is anticipated that the proposed DC SSCB may be utilized to design and realize many DC grid systems.

• The Transactions of the Korean Institute of Power Electronics
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• v.15 no.2
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• pp.103-110
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• 2010

In this paper, a new mode changeable asymmetric full bridge dc/dc converter is proposed to solve the freewheeling current problem of the conventional zero voltage switching(ZVS) phase shift full bridge(PSFB) dc/dc converter of low output voltage and high output current applications. The proposed converter is operated as an asymmetric full bridge converter when the duty cycle is less than 50% and active clamp full bridge converter when the duty cycle is greater than 50%. As a result, since its freewheeling current is eliminated, the conduction loss is lower than that of the conventional ZVS PSFB dc/dc converter. Moreover, ZVS of all power switches can be ensured along a wide load ranges and output current ripple is very small. Therefore, high efficiency of the proposed converter can be achieved. Especially since its operation mode is changed to the active clamp full bridge converter during hold up time and can be operated with 50~100% duty ratio, it can produce the stable output voltage along wide input voltage range. The operational principles, theoretical analysis and design considerations are presented. To confirm the operation, validity and features of the proposed converter, experimental results from a 1.2kW($400V_{dc}/12V_{dc}$) prototype are presented.

• Journal of the Korean Society for Heat Treatment
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• v.23 no.1
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• pp.23-28
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• 2010

The cylindrical magnetron sputtering has not been widely used, although this system is useful for only certain types of applications such as fiber coatings. This paper presents electrode configurations which improved the complicacy of the target assembly by using the positive voltage power supply. It is a modified type which has a target constructed with a large cylindrical part, a conical part and a small cylindrical part. When positive voltage was applied to an anode, a stable glow discharge was established and a high deposition rate was obtained. The substrate bias current was monitored to estimate the effect of ion bombardment. As a result, it was found that the substrate current was large. With cylindrical and conical cathode magnetron sputter deposition on the surface of the substrate to prevent re-sputtering, ion impact because it can increase the effectiveness with excellent ductility and adhesion of Ti film deposition can be obtained. We board at the front end of the ground resistance of $5\;k{\Omega}$ attached to the substrate potential can be controlled easily, and Ti film deposition with excellent adhesion can be obtained. Microstructure and morphology of Ti films deposited on pure Cu wires were investigated by scanning electron microscopy in relation to preparation conditions. High level ion bombardment was found to be effective in obtaining a good adhesion for Cu wire coatings.