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.

Implementation of Effective Wireless Power Transmission Circuit for Low Power System

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

Wireless power transfer (WPT) is the technology that enables the power to transmit electromagnetic field to an electrical load without the use of wires. There are two kinds of magnetic resonant coupling and inductive coupling ways transmitting from the source to the output load. Compared with microwave method for energy transfer over a long distance, the magnetic resonance method has the advantages of reducing the barrier of electromagnetic wave and enhancing the efficiency of power transmission. In this paper, the wireless power transfer circuit having a resonant frequency of 13.45 MHz for the low power system is studied, and the hardware implementation is accomplished to measure the power transmission efficiency for the distance between the transmitter and the receiver.

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.

Implementation of an Underwater ROV for Detecting Foreign Objects in Water

Lho, Tae-Jung The Korea Institute of Information and Commucation 2021 Journal of information and communication convergen Vol.19 No.1

An underwater remotely operated vehicle (ROV) has been implemented. It can inspect foreign substances through a CCD camera while the ROV is running in water. The maximum thrust of the ROV's running thruster is 139.3 N, allowing the ROV to move forward and backward at a running speed of 1.03 m/s underwater. The structural strength of the guard frame was analyzed when the ROV collided with a wall while traveling at a speed of 1.03 m/s underwater, and found to be safe. The maximum running speed of the ROV is 1.08 m/s and the working speed is 0.2 m/s in a 5.8-m deep-water wave pool, which satisfies the target performance. As the ROV traveled underwater at a speed of 0.2 m/s, the inspection camera was able to read characters that were 3 mm in width at a depth of 1.5 m, which meant it could sufficiently identify foreign objects in the water.

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.

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.

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.

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.

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.

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.