• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.9-9
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• 2010

In this paper, High Brightness LED driver IC using new current sensing circuit is proposed. This LED driver IC can provide a constant current with high current precision over a wide input voltage range. The proposed current-sensing circuit is composed of a cascode current sensor and a current comparator with only one reference voltage. This IC minimizes the voltage stress of the MOSFET from the maximum input voltage and has low power consumption and chip area by using simple-structured comparator and minimum bias current. The LED current ripple of the designed IC is in ${\pm}5%$ and a tolerance of the average LED current is lower than 2.43%. This shows much improved feature than the previous method. Also, protections for input voltage and operating temperature are designed to improve the reliability of the designed IC. Designed LED driver IC uses $1{\mu}m$ X-Fab. BiCMOS process parameters and electrical characteristics and functioning are verified by spectre(Cadence) simulation.

• Journal of the Korean Society of Safety
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• v.25 no.6
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• pp.53-59
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• 2010

A fatigue damage caused by cyclic load is considered as one of the important failure mechanisms that threaten the integrity of structures and components in a nuclear power plant. In ASME code section III NB, the fatigue analysis procedure and standard S-N curves for the class 1 components are described and these criteria should be met at the design step of components. As the current ASME S-N curves are based on the very conservative assumptions such as a local stress concentration effect, immoderate transient frequencies and a constant Young's modulus, however, they can not precisely address the fatigue behavior of components. In order to find out the technical solution for these problems, a number of researches and discussion have been carried out continuously at home and abroad over the decades. In this study, detailed fatigue analyses for DVI nozzle with various mesh density of finite elements were performed to evaluate effect of stress concentration factors on the fatigue analysis procedure and the excessive conservatism of stress concentration factors are confirmed through the analysis results.

• Journal of Surface Science and Engineering
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• v.13 no.3
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• pp.146-154
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• 1980

The effects of various electrodeposition conditions (deposition temperature and cathode current density) on preferred orientation and microhardness of electrodeposited Ni-Sn and Sn-Zn alloys were studied. At deposition temperatures from 25$^{\circ}$ to 95$^{\circ}C$ and constant cathode current density of 270 and 530 A/$m^2$ Ni-Sn and Sn-Zn were codeposited in chloride-fluoride acid and stannate-cyanide alkaline electrolyte bath respectively. Ni-Sn alloy deposited at temperatures from 25$^{\circ}$ to 35$^{\circ}C$ was composed of single phase of $Ni_3Sn_4$ with 73 wt.% Sn and the one deposited at temperatures from 45$^{\circ}$ to 95$^{\circ}C$ was made of multiphase mixture of NiSn, $Ni_3Sn_2$ and $Ni_3Sn_4$ with nearly equiatomic composition (65.5 wt.% Sn). The random orientation of thermody-namically metastable NiSn phase (hexagonal structure) predominated at deposition temperature range 25$^{\circ}$-45$^{\circ}C$, and the strong (110) preferred orientation was found at 65$^{\circ}$-85$^{\circ}C$ and then disappeared again at 95$^{\circ}C$. The microhardness of Ni-Sn deposits increased with deposition temperature up to 85$^{\circ}C$, and then decreased at constant cathode current density. The preferred orientation and the maximum microhardness were discussed in terms of lattice contractile stress which result from desorption of hydrogen atom absorbed in deposit lattice. The Sn content of Sn-Zn alloy deposits increased with deposition temperature up to 75$^{\circ}C$, and then decreased at constant cathode current density of 530 A/$m^2$. It also decreased with cathode current density up to 530 A/$m^2$, and then increased at constant deposition temperature of 25$^{\circ}C$. Sn-Zn alloy deposits were composed of two-phase mixture of ${beta}$-Sn and Zn. The preferred orientations of ${beta}$-Sn (tetragonal structure) changed with deposition temperature. The microhardness of Sn-Zn deposits decreased with deposition temperature. It also increased with cathode density up to 530 A/$m^2$, and then decreased at constant deposition temperature of 25$^{\circ}C$. The microhardness of Sn-Zn deposits was observed to be determinded more by the Sn content than by the preferred orientation.

• Steel and Composite Structures
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• v.17 no.4
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• pp.535-548
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• 2014

In this paper, the exact closed-form solutions for torsional analysis of heterogeneous magnetostrictive circular cylinder are derived. The cylinder is subjected to the action of a magnetic field produced by a constant longitudinal current density. It is also acted upon by a particular kind of shearing stress at its upper base. The rigidity of the cylinder is graded through its axial direction from one material at the lower base to another material at the upper base. The distributions of circumferential displacement and shear stresses are presented through the radial and axial directions of the cylinder. The influence of the magnetostrictive parameter is discussed. The effects of additional parameters are investigated.

• Proceedings of the Korean Fiber Society Conference
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• 1988.06a
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• pp.34-34
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• 1988

The pyroelectricity of poly(vinylidenefluoride) films prepared by varying the draw ratio and the poling field was investigated. As the draw ratio and the electric field on poling of the drawn samples increased, so did the pyroelectric coefficient. But the effect of electric field on the pyroelectricity was greater than that of draw ratio. The pyroelectric and piezoelectric activities could be explained by the polarization using the thermally stimulated current. The relation between pyroelectric coefficient and piezoelectric stress constant showed a good linearity.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.2097-2099
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• 1998

This paper proposed an improvement in the Buck ZC-ZVS converter Presented in [1]. This is achieved by change the auxiliary switch position, which reduces its rating power. By employing saturable inductor, the maximum voltage stress across the main switch becomes constant and independent of the load current. Operating principle of Buck proposed topolo described and confirmed by simulation results.

• Journal of Sensor Science and Technology
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• v.31 no.1
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• pp.41-44
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• 2022

In this study, we have fabricated and characterized vertical double-gate (DG) InGaAs tunnel field-effect-transistors (TFETs) with Al₂O₃/HfO₂ = 1/5 nm bi-layer gate dielectric by employing a top-down approach. The device exhibited excellent characteristics including a minimum subthreshold swing of 60 mV/decade, a maximum transconductance of 141 µS/㎛, and an on/off current ratio of over 10³ at 20℃. Although the TFETs were fabricated using a dry etch-based top-down approach, the values of DIBL and hysteresis were as low as 40 mV/V and below 10 mV, respectively. By evaluating the effects of constant voltage and hot carrier injection stress on the vertical DG InGaAs TFET, we have identified the dominant charge trapping mechanism in TFETs.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.05a
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• pp.411-414
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• 1999

70 ${\AA}$-thick oxides nitridied at various conditions were reoxidized at pemperatures of 900$^{\circ}C$ in dry-O$_2$ ambients for 5～40 mininutes. The gate oxide interface porperties as well as the oxide substrate interface properties of MOS(Metal Oxide Semiconductor) capacitors with various nitridation conditions, reoxidation conditions and pure oxidation condition were investigated. We stuided I$\sub$g/-V$\sub$g/ characteristics, $\Delta$V$\sub$g/ shift under constant current stress from electrical characteristics point of view and breakdown voltage from leakage current point of view of MOS capacitors with SiO$_2$, NO, RNO dielectrics. Overall, our experimental results show that reoxidized nitrided oxides show inproved charge trapping porperites, I$\sub$g/-V$\sub$g/ characteristics and gate $\Delta$V$\sub$g/ shift. It has also been shown that reoxidized nitridied oxide's leakage currented voltage is better than pure oxide's or nitrided oxide's from leakage current(1${\mu}$A) point of view.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.709-710
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• 2008

In this paper, we calculated permanent magnetic linkage flux ${\psi}_{\alpha}$ and Ld, Lq parameters of IPMSM and compared two model which has different barrier width. IPMSM has two kinds of torque that reluctance torque and magnetic torque. In constant torque region, using the Maxwell stress tensor method, we calculated the torque and current phase angle ${\beta}$ which has appeared maximum torque. In weakening flux region, we calculated the current phase angle ${\beta}$ which flux ${\psi}_o$ lower than limited flux ${\psi}_{omax}$. From the current phase angle ${\beta}$, we calculated torque by torque equation and compared two model characteristic.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.31A no.6
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• pp.107-116
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• 1994

In this paper, The electrical properties of MOS capacitors and transistoras with gate of in-situ doped amorphous Si and poly Si doped by POCI$_3$. Under constant current F-N stress, MOS capacitors with in-situ doped amorphous Si gate have shown the best resistance to degradation in reliabilty properties such as increase of leakage current, shift of gate voltage (V$_{g}$). shift of flat band voltage (V$_{fb}$) and charge to breakdown(Q$_{bd}$). Also, MOSFETs with in-situ doped amorphous Si gate have shown to have less degradation in transistor properties such as threshold voltage, transconductance and drain current. These improvements observed in MOS devices with in-situ doped amorphous Si gate is attributed to less local thinning spots at the gate/SiO$_2$ interface, caused by the large grain size and the smoothness of the surface at the gate/SiO$_2$ interface.