• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.322-322
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• 2008

Low-temperature co-fired ceramics (LTCC) have turned out to be very promising technology in accordance with the rapid developments in semiconductor technology. The demands for compact electrical assemblies, smaller power loss as well as high signal density can be fulfilled by LTCC. And for the multi-layered ceramic devices with embedded passive components such as high dielectric constant decoupling capacitor, LTCC materials require the several conditions to avoid delamination and internal cracks. For the present study, diopside-based glass is chosen as the LTCC substrate material in view of its high coefficient of thermal expansion (CTE). From the experimental resultsn the influence of each element on the CTE change can be revealed.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.483-484
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• 2007

In this paper, we describe a chip design technique for instrumentation amplifier using a nested-chopping technique. Conventional chopping technique uses a pair of chopper, but nested chopping technique uses two pairs of chopper to reduce residual offset and 1/f noise. The inner chopper pair removes the 1/f noise, while the outer chopper pair reduces the residual offset. Our instrumentation amplifier using a nested chopping technique has residual offset under 100 nV. We also implement very low frequency filter. Since this filter needs very large RC time constant, we use a technique named 'diode connected PMOS' to increase R with small die area. The total power consumption is 3.1 mW at the supply voltage of 3.3V with the 0.35um general CMOS technology. The die area of implemented chip was $530um{\times}300um$.

• Journal of Korean Institute of Industrial Engineers
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• v.22 no.3
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• pp.459-471
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• 1996

This paper considers ramp tests for exponential lifetime distribution when there are limitations on test stress and test time. The inverse power law and a cumulative exposure model are assumed. Maximum likelihood (ML) estimators of model parameters and their asymptotic covariance matrix are obtained. The optimum ramp test plans are also found which minimize the asymptotic variance of the ML estimator of the log mean life at design constant stress. For selected values of the design parameters, tables useful for finding optimal test plans are given. The effect of the pre-estimates of design parameters is studied.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.62 no.6
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• pp.750-755
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• 2013

In-wheel motor system gets the driving force from direct-driven motor in the wheel of electric vehicle. It is known as good system for vehicles, from an efficiency, packaging, handling and safety. This paper describes motor and inverter technologies, system configuration and control algorithms for in-wheel type electric vehicle. It is necessary to control on an interrelation perspective because this system drives two motors at same time. In system design, IPMSM(Interior Permanent Magnet Synchronous Motor) including a wide operating range and high-speed rpm is used and flux weakening control is performed in constant power range. Under the torque command from the host controller, auto control box, inverter's output torque is calculated with using torque estimation technique and applied to actual vehicle driving system. It is verified that the configuration and the algorithm are suitable for the in-wheel motor system.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.27-29
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• 2005

This paper studies particularly applicable method for sensorless Permanent Magnet Brushless DC(PMBLDC) Motor drive system. The waveform of the motor internal voltages (or back emf) contains a fundamental and higher order frequency harmonics. Therefore the third harmonics. component is extracted from the stator phase voltage. The resulting third harmonic signal keeps a constant phase relationship with the rotor flux for any motor speed and load condition. In addition, a simple starting method and a speed estimation approach are also proposed.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.336-339
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• 2005

This paper presents a PM type BLDC(Brushless DC) Motor servo drive system using high performance DSP TMS320F2812. The DSP controller with 150MIPS enables an enhanced real time implementation and increased efficiency and high performance for motor drive. The suggested drive system consists of PI action for the constant speed control and PID action for the current control with only 3 Halls, no encoders. The developed servo drive control system shows a good response speed characteristics at high speed up to 10000 [rpm].

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.587-590
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• 2005

In this paper, the PWM inverter-motor drive system including sensor is controlled through the network. The algorithm to compensate for the time delay of ac current and ac voltage sensors due to the network is proposed. The delay time of sensors is kept nearly constant, using the synchronous signal and timers. The error between the real and estimated ac signals can be reduced by using two slopes for estimating the value of at signals. The proposed algorithms are verified with the simulation studies and experiments.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.60-62
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• 2018

본 논문에서는 유도전동기의 회전자 시정수 오차에 강인한 센서리스 전차원(Full-Order) 자속(Flux) 관측기(Observer)를 제안하였다. 이 관측기는 고정자 자속과 회전자 자속을 동기좌표계상에서 추정한다. 고정자 자속에서 누설 자속을 뺀 공극 자속을 기준으로 제어를 수행하며, 동기좌표계가 공극 자속을 빠르게 따라갈 수 있는 방법을 제안하였다. 제안된 방법을 적용할 때, 기존의 회전자 자속을 직접 이용하는 방법보다 중-고속 영역에서 회전자 시정수 오차의 영향이 감소함을 확인하였다. 또한 기존 관측기와 달리 제안된 관측기에서 적응제어기(Adaptive Controller)는 전동기의 회전 주파수가 아닌, 전동기의 슬립 주파수 만을 추정하므로, 회전자 자속 오차에 민감한 적응제어기의 역할을 축소하였다. 시뮬레이션 및 실험으로 이론의 타당성 및 효과를 검증하였다.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.1088-1091
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• 2009

A boost converter with charge-recycling technique fabricated by $0.25{\mu}m$ CMOS BCD process can provide different supply voltages to drive series RGB LEDs in sequence for reducing the power consumption on the constant current generator. The proposed technique stores and restores extra energy to improve the efficiency, as well as enhances the reference tracking response. Experimental results show that the period of reference-tracking response can be improved. When the load current is 100mA, the periods of reference down-tracking and uptracking are smaller than $10{\mu}s$ and $20{\mu}s$, respectively. Experimental results demonstrate fast and efficient reference tracking performance is achieved.

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.636-639
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• 2007

We have developed novel bipolar host materials, designed to have both electron transporting and hole transporting abilities, which show significant increase in luminance efficiency and decrease in driving voltage of green phosphorescent OLEDs. In case of the best host material, CheilGH-3, the driving voltage was decreased 27 % at a given constant luminance of $1000cd/m^2$. Also the luminance efficiency was enhanced 44 % and the power efficiency was almost doubled compared to the reference device using CBP as a host.