• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.963-964
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• 2006

By combining a digital DLL and an analog DLL in 2-stage, an improved DLL is implemented in this paper. The proposed DLL is composed of a RDLL (Register Controlled DLL) and a conventional analog DLL. The phase comparator used in the DLL is built with sense-amp based D flip-flops for high speed operation. The proposed DLL circuits have been designed, simulated in 0.18um, 1.8V TSMC CMOS library. The implemented DLL have demonstrated the fast lock-on time of 1us and low jitter of 72ps.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.6
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• pp.7-16
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• 2010

Physical fundamentals of ultrashort femtosecond lasers are addressed along with emerging applications for precision manufacturing and metrology. Femtosecond lasers emit short pulses whose temporal width is in the range of less than a picosecond to a few femtoseconds, thereby enabling extremely high peak-power machining with less thermal damages. Besides, the broad spectral bandwidth of femtosecond lasers constructed in the form of frequency comb permits absolute distance measurements leading to ultraprecision positioning control and dimensional metrology.

• Journal of the Korean Society of Industry Convergence
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• v.21 no.6
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• pp.265-271
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• 2018

DC-DC buck converter is a critical building block in the power management integrated circuit (PMIC) architecture for the portable devices such as cellular phone, personal digital assistance (PDA) because of its power efficiency over a wide range of conversion ratio. To ensure a safe operation, avoid unexpected damages and enhance the reliability of the converter, fully-integrated protection circuits such as over voltage protection (OVP), under voltage lock out (UVLO), startup, and thermal shutdown (TSD) blocks are designed. In this paper, these three fully-integrated protection circuit blocks are proposed for use in the DC-DC buck converter. The buck converter with proposed protection blocks is operated with a switching frequency of 1 MHz in continuous conduction mode (CCM). In order to verify the proposed scheme, the buck converter has been designed using a 180 nm CMOS technology. The UVLO circuit is designed to track the input voltage and turns on/off the buck converter when the input voltage is higher/lower than 2.6 V, respectively. The OVP circuit blocks the buck converter's operation when the input voltage is over 3.3 V, thereby preventing the destruction of the devices inside the controller IC. The TSD circuit shuts down the converter's operation when the temperature is over $85^{\circ}C$. In order to verify the proposed scheme, these protection circuits were firstly verified through the simulation in SPICE. The proposed protection circuits were then fabricated and the measured results showed a good matching with the simulation results.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.2
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• pp.57-63
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• 2009

In this Paper, a novel 622Mbps burst-mode clock and data recovery (CDR) circuit is proposed for passive optical network (PON) applications. The CDR circuit is composed of CDR(Clock and Data Recovery) block and PLL(Phase Locked Loop) block. Lock dynamics is accomplished on the first data transition and data are sampled in the optimal point. The CDR circuit is realized in 0.35um CMOS process technology. With input pseudo-random bit sequences(PRBS) of $2^7-1$, the simulations show 17ps peak-to-peak retimed data jitter characteristics. The experimental results show that the proposed CDR circuits are operating as expected, recovering an incoming 622Mbps burst-mode input data without errors.

• Journal of Technology Innovation
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• v.22 no.3
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• pp.135-166
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• 2014

'Creative Economy' has been announced as the new paradigm of socio-economic development strategy of newly elected President Geun-Hye Park's administration. By explicitly defining people as a major player in creative activity, it seems to depart from expert-driven or science & technology-focused development paradigms of previous administrations. Yet, its interpretation and operation in terms of government policy does not seem to show any differences. This study aims to explicate the nature of Creative Economy as a development paradigm by clarifying the differences between people's creativity and that of scientists and engineers through extensive literature review. People can contribute to the creative activity not just as users but also as living persons who make everyday yet independent choices based on their humanistic, philosophical, ethical and experiential capabilities which are clearly different from the sources of scientists' & engineers' creativity. People's creative activity does involve value judgement about life and can often accelerate the system innovation or transition by changing consumer behaviour and lifestyle, and hence destruct technological lock-in user lock-in of the existing system. People's creativity can thus present 'User/Field-driven Innovation Paradigm which clearly differs from existing expert- or science & technology-driven innovation paradigm. The Creative Economy with focus on people's creativity therefore faces new socio-economic development challenges of fulfilling the User/Field-driven Innovation Paradigm.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.4
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• pp.506-517
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• 2015

This paper presents a 1.248 Gb/s - 2.918 Gb/s low-power receiver MIPI-DigRF M-PHY with a fully digital frequency detection loop. MIPI-DigRF M-PHY should be operated in a very short training time which is $0.01{\mu}s$ the for HS-G2B mode. Because of this short SYNC pattern, clock and data recovery (CDR) should have extremely fast locking time. Thus, the quarter rate CDR with a fully digital frequency detection loop is proposed to implement a fast phase tracking loop. Also, a low power CDR architecture, deserializer and voltage controlled oscillator (VCO) are proposed to meet the low power requirement of MIPI-DigRF M-PHY. This chip is fabricated using a $0.11{\mu}m$ CMOS process, and the die area is $600{\mu}m{\times}250{\mu}m$. The power consumption of the receiver is 16 mW from the supply voltage of 1.1 V. The measured lock time of the CDR is less than 20 ns. The measured rms and peak jitter are $35.24ps_{p-p}$ and $4.25ps_{rms}$ respectively for HS-G2 mode.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2500-2505
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• 2007

The vacuum interrupter (VI) is used for medium-voltage switching circuits due to its abilities and advantages as a compact and environmental friendly circuit breaker. In general, the application of a sufficiently strong axial magnetic field (AMF) permits the arc to be maintained in a diffused mode to a high-current vacuum arc. A full understanding of the vacuum arc physics is very important since it can aid to improve the performance of vacuum interrupter. In order to closely examine the vacuum arc phenomena, it is necessary to predict the magnetohydrodynamic (MHD) characteristics by the multidisciplinary numerical modeling, which is coupled with the electromagnetic and hydrodynamic fields, simultaneously. In this study, we have investigated the electromagnetic behaviors of high-current vacuum arcs for two different types of AMF contacts, which are coil-type and cup-type, using a commercial finite element analysis (FEA) package, ANSYS. The present results are compared with those of MAXWELL 3D, a reliable electromagnetic analysis software, for verification.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.5
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• pp.180-187
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• 2007

This paper presents a mathematical vehicle model that is designed to analyze the dynamic performance and to develop various safety control systems. Wheel slip controllers for ABS is also formulated to improve the vehicle response and to increase the safety on slippery road. Validation of the model and controller is performed by comparison with a commercial software package, CarSim. The result shows that performances of developed vehicle model are in good accordance with those of the CarSim on various driving conditions. Developed ABS controller is applied to the vehicle model and CarSim model, and it achieves good control performance. ABS controller improves lateral stability as well as longitudinal one when a vehicle is in turning maneuver on slippery road. A driver model is also designed to control steer angle of the vehicle model. It also shows good performance because the vehicle tracks the desired lane very well.

• Journal of Biosystems Engineering
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• v.12 no.1
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• pp.6-13
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• 1987

A mathematical model for the waste heat recovery system for an engine was developed. The model based on the experimental data reported before was validated and was used to predict the waste heat recovery and recoverable heat of the engine at various operating conditions of the engine and the system. The model was also used to determine flow rates of the circulating water in the system for a certain temperature increment of the water at various operating conditions of the engine to give basic data to design the system. Stability of the system performance was tested on subjects of vapor lock problem, thermal characteristics of the thermostatic valve, and temperature variation of the circulating water in the engine and fuel consumption of the engine during each mode of the system operation and its change into the other. The test showed that the system operation was stable enough. Temperature profile in the thermal energy storage (TES) was observed during storing thermal energy, and thermal stratification in the TES was well formed acceptable to be used in the system. Finally a scheme to automatize the system was suggested.

• Journal of the Korean Institute of Intelligent Systems
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• v.22 no.5
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• pp.597-602
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• 2012

In this paper, a manual and automatic steering system for electric vehicles capable of manned and unmanned driving is proposed. The automatic steering systems, EPS, MDPS, used in conventional engine based car includes the problem of handle lock phenomenon while driving of overloading, therefore it has a drawback to apply to manned and unmanned electric vehicles. By using electronic clutch and pulleys, the proposed manual and automatic steering mechanism was designed so that it is possible to convert from manual to automatic steering mode. To experiment the performance of the proposed steering system, we made an experimental setup of an electric vehicle. We confirmed that the proposed manual and automatic steering system was useful for manned and unmanned electric vehicles.