DC/DC 전력 컨버터의 전류모드 PWM 제어기의 방사선 영향

노영환(Young Hwan Lho),황의성(Eui Sung Hwang),노경수(Kyeoung Su Lho),푸파논(Phouphanonh),캄푸는(Khamphoungeun),한창운(Chang Won Han) 한국철도학회 2011 한국철도학회 학술발표대회논문집 Vol.2011 No.10

DC/DC switching power converters produce DC output voltages from different DC input sources. The converters can be used in regenerative braking of DC motors to return energy back in the supply resulting in energy savings for the systems containing frequent stops. The current mode DC/DC converter is composed of a PWM (pulse width modulation) controller a MOSFET and inductor etc. Pulse width modulation is applied to control and regulate the total output voltage. It is shown that the variation of threshold voltage at MOSFET and the offset voltage increase caused by radiation effects make the PWM pulse unstable. In the PWM operation the missing pulses the changes in pulse width and a change in the period of the output waveform are studied by simulation program with integrated circuit emphasis (SPICE) and experiments.

Accuracy Enhancement of Reflection Signals in Impact Echo Test

Lho, Byeong-Cheol Korea Concrete Institute 2003 콘크리트학회논문집 Vol.15 No.6

A majority of infrastructures has been deteriorated over time. Therefore, it is very important to verify the quality of construction, and the level of structural deterioration in existing structures, to ensure their safety and functionality. Many researchers have studied non-destructive testing (NDT) methods to identify structural problems in existing structures. The impact echo technique is one of the widely used NDT techniques. The impact echo technique has several inherent problems, including the difficulties in P-wave velocity evaluation due to inhomogeneous concrete properties, deterioration of evaluation accuracy where multiple reflection boundaries exist, and the influence of the receiver location in evaluating the thickness of the tested structures. Therefore, the objective of this paper is to propose an enhanced impact echo technique that can reduce the aforementioned problems and develop a Virtual Instrument for the application via a thickness evaluation technique which has same technical background to find deterioration in concrete structures. In the proposed impact echo technique, transfer function from dual channel system analysis is used, and coherence is improved to achieve reliable data. Also an averaged signal -ensemble- is used to achieve more reliable results. From the analysis of transfer function, the thickness is effectively identified.

A Methodology of Dual Gate MOSFET Dosimeter with Compensated Temperature Sensitivity

Lho, Young-Hwan Institute of Korean Electrical and Electronics Eng 2011 전기전자학회논문지 Vol.15 No.2

MOS (Metal-Oxide Semconductor) devices among the most sensistive of all semiconductors to radiation, in particular ionizing radiation, showing much change even after a relatively low dose. The necessity of a radiation dosimeter robust enough for the working environment has increased in the fields of aerospace, radio-therapy, atomic power plant facilities, and other places where radiation exists. The power MOSFET (Metal-Oxide Semiconductor Field-Effect Transistor) has been tested for use as a gamma radiation dosimeter by measuring the variation of threshold voltage based on the quantity of dose, and a maximum total dose of 30 krad exposed to a $^{60}Co$ ${\gamma}$-radiation source, which is sensitive to environment parameters such as temperature. The gate oxide structures give the main influence on the changes in the electrical characteristics affected by irradiation. The variation of threshold voltage on the operating temperature has caused errors, and needs calibration. These effects can be overcome by adjusting gate oxide thickness and implanting impurity at the surface of well region in MOSFET.

Design of Super-junction TMOSFET with Embedded Temperature Sensor

Lho, Young Hwan Institute of Korean Electrical and Electronics Eng 2015 전기전자학회논문지 Vol.19 No.2

Super-junction trench MOSFET (SJ TMOSFET) devices are well known for lower specific on-resistance and high breakdown voltage (BV). For a conventional power MOSFET (metal-oxide semiconductor field-effect transistor) such as trench double-diffused MOSFET (TDMOSFET), there is a tradeoff relationship between specific on-state resistance and breakdown voltage. In order to overcome the tradeoff relationship, a SJ TMOSFET structure is suggested, but sensing the temperature distribution of TMOSFET is very important in the application since heat is generated in the junction area affecting TMOSFET. In this paper, analyzing the temperature characteristics for different number bonding for SJ TMOSFET with an embedded temperature sensor is carried out after designing the diode temperature sensor at the surface of SJ TMOSFET for the class of 100 V and 100 A for a BLDC motor.

Optimal Linear Income Tax in a Worldwide Setting

(Lho Sang Whan) 한양대학교 경제연구소 1999 JOURNAL OF ECONOMIC RESEARCH Vol.4 No.2

콘크리트 슬래브의 미진동 제어

Lho, Byeong Cheol,Byun, Keun Joo,Yang, Jae Sung 한국지진공학회 1998 한국지진공학회논문집 Vol.2 No.4

본 연구는 허용진동환경을 만족하기 위한 콘크리트 슬래브의 미진동해석 및 제어기법에 관한 것이다. 본 연구에서는 제시된 방법은 임의 두 점간의 전달 함수와 가속 도로부터 미지의 가진력을 산정하고 수치해석 및 구조실험의 검증을 통하여 콘크리트 슬래브의 미진동해석 및 제어를 실시하였다. 미진동제어 설계를 위한 구조물의 고유진동수는 25-30Hz 이상이 되는 것인 바람직하며 콘크리트 구조물에서의 감쇠가 3%-5%인 경우 가진력 진동성분의 1.5배 이상 되는 것이 바람직함을 밝혔다. This study is to develop a technique for micro-vibration analysis and control of concrete slabs to fulfil the vibration criteria for working environments. The proposed technique is for determining the unknown forces from accelerance of two concerned points and the micro-vibration analysis and control of concrete slabs are then validated by numerical model and structural tests. And it is recommended that the natural frequency of structures for micro-vibration control design should be above 25 Hz~30 Hz, and 1.5 times forcing frequency in case of 3~5% structural damping ratio of concrete structures.

OPTIMAL TAXATION OF FDI IN A SMALL OPEN ECONOMY

Lho, Sang Whan 한국경제학회 1998 The Korean Economic Review Vol.14 No.2

Model Identification and Attitude Control Methodology for the Flexible Body of a Satellite

Lho, Young-Hwan The Korean Society for Aeronautical and Space Scie 2010 International Journal of Aeronautical and Space Sc Vol.11 No.3

The controller of a model reference adaptive control monitors the plant's inputs and outputs to acknowledge its characteristics. It then adapts itself to the characteristics it encounters instead of behaving in a fixed manner. An important part of every adaptive scheme is the adaptive law for estimating the unknown parameters on line. A more precise model is required to improve performance and to stabilize a given dynamic system, such as a satellite in which performance varies over time and the coefficients change due to disturbances, etc. After model identification, the robust controller ($H{\infty}$) is designed to stabilize the rigid body and flexible body of a satellite, which can be perturbed due to disturbance. The result obtained by the $H{\infty}$ controller is compared with that of the proportional and integration controller which is commonly used for stabilizing a satellite.

A Study on the Design of a Pulse-Width Modulation DC/DC Power Converter

Lho, Young-Hwan The Korean Society for Aeronautical and Space Scie 2010 International Journal of Aeronautical and Space Sc Vol.11 No.3

DC/DC Switching power converters are commonly used to generate regulated DC output voltages with high-power efficiencies from different DC input sources. A switching converter utilizes one or more energy storage elements such as capacitors, or transformers to efficiently transfer energy from the input to the output at periodic intervals. The fundamental boost converter studied here consists of a power metal-oxide semiconductor field effect transistor switch, an inductor, a capacitor, a diode, and a pulse-width modulation circuit with oscillator, amplifier, and comparator. A buck converter containing a switched-mode power supply is also studied. In this paper, the electrical characteristics of DC/DC power converters are simulated by simulation program with integrated circuit emphasis (SPICE). Furthermore, power efficiency was analyzed based on the specifications of each component.

Seeding of Meningeal Sarcoma Along a Surgical Trajectory on the Scalp

( Lho Hyoung Woo ),( Yoon Wan Soo ),( Chung Dong Sup ) 대한뇌종양학회·대한신경종양학회·대한소아뇌종양학회 2016 Brain Tumor Research and Treatment Vol.4 No.2

Primary sarcomas of the central nervous system are rare. These tumors is rapid growth often produces mass effect on the brain. Diagnosis is rendered pathologically after resection. Surgical resection is the mainstay treatment and need the adjuvant therapy. We report a 44-year-old female with a meningeal sar-coma of frontal meninges. She complained headache for 2 months and palpable forehead mass for 3 weeks. Brain MRI demonstrated a soft tissue mass sized as 5.3×3.7×3.1 cm with well-defined osteolysis on the midline of the frontal bone. The mass attached to anterior falx without infiltration into the brain parenchyme. The tumor had extracranial and extraaxial extension with bone destruction. The tumor was totally removed with craniectomy and she had an adjuvant radiotherapy. However, an isolated subcutaneous metastasis developed at the both preauricular area of the scalp, originating from the scar which was remained the first surgery. After complete removal of this metastasis, she had an adjuvant radiotherapy in other hospital. However, she expired after six months after first surgery. We believe that the occurrence of tumor seeding at the site of incision in the scalp is related to using the fluid for irrigation after tumor resection and the same surgical instruments for the removal of the brain tumor.