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.

A Study on Temperature Dependent Super-junction Power TMOSFET

Lho, Young Hwan 한국전기전자학회 2016 전기전자학회논문지 Vol.20 No.2

It is important to operate the driving circuit under the optimal condition through precisely sensing the power consumption causing the temperature made mainly by the MOSFET (metal-oxide semiconductor field-effect transistor) when a BLDC (Brushless Direct Current) motor operates. In this letter, a Super-junction (SJ) power TMOSFET (trench metal-oxide semiconductor field-effect transistor) with an ultra-low specific on-resistance of 0.96mΩ·cm² under the same break down voltage of 100 V is designed by using of the SILVACO TCAD 2D device simulator, Atlas, while the specific on-resistance of the traditional power MOSFET has tens of mΩ·cm² , which makes the higher power consumption. The SPICE simulation for measuring the power distribution of 25 cells for a chip is carried out, in which a unit cell is a SJ Power TMOSFET with resistor arrays. In addition, the power consumption for each unit cell of SJ Power TMOSFET, considering the number, pattern and position of bonding, is computed and the power distribution for an ANSYS model is obtained, and the SJ Power TMOSFET is designed to make the power of the chip distributed uniformly to guarantee it's reliability.

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.

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.

A Study on Design of PWM DC/DC Power Converter

Lho Young Hwan(노영환),Lee Sang Yong(이상용),Kim Yoon Ho(김윤호) 한국철도학회 2009 한국철도학회 학술발표대회논문집 Vol.2009 No.11월

DC/DC Switching power converters are commonly used to generate a regulated DC output voltage with high-power efficiency from a different DC input source. 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 basic boost converter studied here are consisted of a power MOSFET switch, an inductor, a capacitor, a diode, and a PWM (pulse-width modulation) circuit with oscillator, amplifier, and comparator. In this paper, the electrical characteristics of DC/DC power converter are simulated by SPICE and analyzed based on each component specification.

Design of Main Body and Edge Termination of 100 V Class Super-junction Trench MOSFET

Lho, Young Hwan Institute of Korean Electrical and Electronics Eng 2018 전기전자학회논문지 Vol.22 No.3

For the conventional power MOSFET (metal-oxide semiconductor field-effect transistor) device structure, there exists a tradeoff relationship between specific on-state resistance (Ron,sp) and breakdown voltage (BV). In order to overcome this tradeoff, a super-junction (SJ) trench MOSFET (TMOSFET) structure with uniform or non-uniform doping concentration, which decreases linearly in the vertical direction from the N drift region at the bottom to the channel at the top, for an optimal design is suggested in this paper. The on-state resistance of $0.96m{\Omega}-cm2$ at the SJ TMOSFET is much less than that at the conventional power MOSFET under the same breakdown voltage of 100V. A design methodology for the edge termination is proposed to achieve the same breakdown voltage and on-state resistance as the main body of the super-junction TMOSFET by using of the SILVACO TCAD 2D device simulator, Atlas.

A Study on Mathematical Modeling and Parameter Optimization for Automatic Pipe Welding Process

Lho, Tae-Jung 동명정보대학교 1999 東明情報大學校論文集 Vol.2 No.-

An efficient finite difference model was adopted for calculating the three-dimensional transient temperature distribution in circumferential gas tungsten arc(GTA) welding of pipes. Its solution was obtained by employing the alternating direction implicit(ADI) finite difference method, in which a periodic boundary condition and a periodic cubic spline function were used. For calculating the weld pool surface profiles in full penetration circumferential welding of pipes, a generating equation was derived in the cylindrical coordinate and solved using a simple finite difference model with the ADI scheme. An efficient parameter optimization method is used to evaluate the optimal welding current for a required bead width when the welding velocity is given.

A Feedback Circuit of Effective Wireless Power Transfer for Low Power System

Lho, Young Hwan Institute of Korean Electrical and Electronics Eng 2018 전기전자학회논문지 Vol.22 No.2

Wireless power transfer (WPT) is the technology that forces the power to transmit electromagnetic field to an electrical load through an air gap without interconnecting wires. This technology is widely used for the applications from low power smartphone to high power electric railroad. In this paper, the model of wireless power transfer circuit for the low power system is designed for a resonant frequency of 13.45 MHz. Also, a feedback WPT circuit to improve the power transfer efficiency is proposed and shown better performance than the original open WPT circuit, and the methodology for power efficiency improvement is studied as the coupling coefficient increases above 0.01, at which the split frequency is made.

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.

The Implementation of Testing Board forSingle Event Upsets

Lho, Young-Hwan,Kim, Ki-Yup The Korean Society for Aeronautical and Space Scie 2004 International Journal of Aeronautical and Space Sc Vol.5 No.2

One of the major problem encountered in nuclear plants and satellites design isEMI (Electro-Magnetic Interference) and EMC (Electro-Magnetic Compatibility).Here, our focus is to implement the test board for checking SEU (Single EventUpsets); the effects of protons on the electronic system. The SEU results from thelevel change of stored information due to photon radiation and temperature in thespace environment. The impact of SEU on PLD (Programmable Logic Devices)technology is most apparent in ROM/SRAM/DRAM devices wherein the state ofstorage cell can be upset. In this paper, a simple and powerful test techniques issuggested, and the results are presented for the analysis and future reference. In ourexperiment, the proton radiation facilitv (having the energy of 50 MeV with a beamcurrent of 60 uA of cyclotron) available at KIRAMS (Korea Institute of RadiologicalMedical Sciences) has been applied on a commercially available SRAM manufacturedby Hynix Semiconductor Company.