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유승우,이한신,강이구,성만영,Yu, Seung-Woo,Lee, Han-Shin,Kang, Ey-Goo,Sung, Man-Young 한국전기전자학회 2007 전기전자학회논문지 Vol.11 No.4
The recessed gate IGBT has a lower on-state voltage drop compared with the DMOS IGBT, because there is no JFET resistance. But because of the electric field concentration in the corner of the gate edge, the breakdown voltage decreases. This paper is about the new structure to effectively improve the Vce(sat) voltage without breakdown voltage drop in 1700V NPT type recessed gate IGBT with p floating shielding layer. For the fabrication of the recessed gate IGBT with p floating shielding layer, it is necessary to perform the only one implant step for the shielding layer. Analysis on the Breakdown voltage shows the improved values compared to the conventional recessed gate IGBT structures. The result shows the improvement on Breakdown voltage without worsening other characteristics of the device. The electrical characteristics were studied by MEDICI simulation results.
장봉렬,박호동,이경중,Jang, Bong-Ryeol,Park, Ho-Dong,Lee, Kyoung-Joung 대한의용생체공학회 2007 의공학회지 Vol.28 No.1
MR(magnetic resonance) image of moving organ such as heart shows serious distortion of MR image due to motion itself. To eliminate motion artifacts, MRI(magnetic resonance imaging) scan sequences requires a trigger pulse like ECG(electro-cardiography) R-wave. ECG-gating using cardiac cycle synchronizes the MRI sequence acquisition to the R-wave in order to eliminate image motion artifacts. In this paper, we designed ECG/PPG(photo-plethysmography) gating system which is for eliminating motion artifacts due to moving organ. This system uses nonmagnetic carbon electrodes, lead wire and shield case for minimizing RF(radio-frequency) pulse and gradient effect. Also, we developed a ECG circuit for preventing saturation by magnetic field and a finger plethysmography sensor using optic fiber. And then, gating pulse is generated by adaptive filtering based on NLMS(normalized least mean square) algorithm. To evaluate the developed system, we measured and compared MR imaging of heart and neck with and without ECG/PPG gating system. As a result, we could get a clean image to be used in clinically. In conclusion, the designed ECG/PPG gating system could be useful method when we get MR imaging of moving organ like a heart.
정헌석 한국전기전자재료학회 2018 Transactions on Electrical and Electronic Material Vol.19 No.4
This paper designed a structure of the shielded trench gate power MOSFET device, which has been applied to small capacity(less than or equal to 100 V) and high-speed operation as the next generation power semiconductor device, based onthe optimally developed design and process parameters using 2D device and process simulator, and then compared andanalyzed the electrical characteristics between existing and shielded trench gate power MOSFET devices. The breakdownvoltage characteristic, which was regarded as the core characteristic of power semiconductor device, showed that both ofthe devices had around 120 V, indicating no signifi cant change. However, the threshold voltage characteristic, which wasone of the characteristics present in power semiconductor devices for mobile phone battery, exhibited that turn-on voltagewas comparable with each other but the fl owing current characteristic was signifi cantly improved in the shielded trench gatepower MOSFET. Furthermore, the on-resistance characteristic was analyzed according to the oxide thickness of shieldedMOSFET, and the optimal value was obtained when oxide thickness was 0.3 μm.
치과 방사선촬영 시 구내 센서 내 차폐체 삽입을 통한 피폭선량 감소 연구
김아연,이승재 한국방사선학회 2022 한국방사선학회 논문지 Vol.16 No.3
In order to reduce the absorbed dose given to the patient during dental radiography, a sensor that inserts a shield into the intraoralsensor was designed. Using the designed sensor, the change in absorbed dose depending on whether or not a shield was used was evaluated. The system used to evaluate the absorbed dose is VEX-S300C from Vatech, and the energy spectrum of X-rays was obtained through SPEKTR simulation based on the irradiation conditions of 65 kV, 3 mA, and 0.15 sec, and the number of photons for each energy was derived. After designing the system through Genat4 Application for Tomographic Emission(GATE) simulation, the energy spectrum obtained was used as a radiation source to calculate the absorbed dose. Lead was used for the shield, and simulations were performed at 0.1 mm thickness intervals from 0.1 mm to 0.5 mm was evaluated. In the case of using an X-ray field with a diameter of 60 mm, the decrease in absorbed dose according to the presence or absence of a shield decreased exponentially as the thickness of the shield increased. In addition, when a 20 mm X 30 mm field was used, the absorbed dose was significantly reduced even when no shield was used, and it was confirmed that the absorbed dose was further reduced when a shield was used. 치과 방사선촬영 시 환자에게 부여되는 피폭선량을 감소시키기 위해 구내 센서 내에 차폐체를 삽입하는 센서를 설계하였다. 설계한 센서를 사용하여 차폐체의 사용 유무에 따른 피폭선량의 변화를 평가하였다. 피폭선량 평가에 사용한 시스템은 바텍 사의 VEX-S300C이며, 65 kV, 3 mA, 0.15 sec의 조사 조건을 바탕으로 SPEKTR 시뮬레이션을 통해 X-선의 에너지스펙트럼을 획득하고, 각 에너지별 광자수를 도출하였다. Genat4 Application for Tomographic Emission(GATE) 시뮬레이션을 통해 시스템을 설계한 후 획득한 에너지스펙트럼을 방사선원으로 사용하여 피폭선량을 산출하였다. 차폐체는 납을 사용하였으며, 0.1 mm ~ 0.5 mm까지 0.1 mm 두께 간격으로 시뮬레이션을 수행하였으며, 이때 설계한 조사야는 직경 60 mm와 시스템의 선택 사항으로 사용 가능한 20 mm 30 mm의 조사야에 대한 피폭선량을 평가하였다. 직경 60 mm 조사야를 사용할 경우 차폐체의 유무에 따른 피폭선량의 감소는 차폐체의 두께가 증가함에 따라 지수함수적으로 감소하였다. 또한 20 mm 30 mm 조사야를 사용할 경우 차폐체를 사용하지 않았음에도 피폭선량은 상당히 감소하였고, 차폐체를 사용할 경우 더욱 피폭선량은 감소하는 것을 확인할 수 있었다.
Consideration to minimize power losses in Synchronous Rectification
Wonsuk Choi,Sungmo young,Dongkook Son,Seunghwan Shin,Dongseok Hyun 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
A synchronous rectification in high performance converter design is an essential block for low voltage and high current applications since significant efficiency and power density improvements can be achieved by replacing schottky rectification with synchronous rectification MOSFETs. Many critical parameters for synchronous rectification MOSFETs and even parasitic components in devices and printed circuit board directly affect to system efficiency of synchronous rectifications. Optimization of the MOSFETs plays an important role in improving efficiency of synchronous rectification. This paper shows the impact of power MOSFET parameters and parasitic inductance on efficiency of synchronous rectification through loss analysis of power MOSFET from an experiment and a simulation results.