Design and control of a permanent magnet spherical wheel motor

박준보,김민기,장현규,정동윤,박종문 한국전자통신연구원 2019 ETRI Journal Vol.41 No.6

We present a permanent magnet–based spherical wheel motor that can be used in omnidirectional mobility applications. The proposed motor consists of a ball‐shaped rotor with a magnetic dipole and a hemispherical shell with circumferential air‐core coils attached to the outer surface acting as a stator. Based on the rotational symmetry of the rotor poles and stator coils, we are able to model the rotor poles and stator coils as dipoles. A simple physical model constructed based on a torque model enables fast numerical simulations of motor dynamics. Based on these numerical simulations, we test various control schemes that enable constant‐speed rotation along arbitrary axes with small rotational attitude error. Torque analysis reveals that the back electromotive force induced in the coils can be used to construct a control scheme that achieves the desired results. Numerical simulations of trajectories confirm that even without explicit methods for correcting the rotational attitude error, it is possible to drive the motor with a low attitude error (<5°) using the proposed control scheme.

고지질이 유발된 흰쥐에서 버섯된장 추출물의 Hypolipidemic 효과

양병근,박준보,하상오,김기영,금교혁,박건영,윤종원,송치현 한국산업미생물학회 2000 한국미생물·생명공학회지 Vol.28 No.4

버섯된장 추출물이 고지혈증에 미치는 영향을 알아보기 위하여 고지혈증이 유도된 흰쥐에 세 종류의 버섯된장 추출물을 경구투여한 후 혈청 및 간장에서의 지질 성분을 측정하였다. 그 결과 체중 증가량에 있어서 영지버섯 된장군(ESG)이 대조군에 비해 10%가 유의하게 낮았으나, 다른 군들은 차이가 없었다. 식이 섭취량, 식이 효율 및 간과 신장의 무게에 있어서는 버섯된장 추출물 투여군들이 대조군과 별다른 차이가 없었으나, 비장 무게는 ESG군이 다른 군에 비해 유의하게 낮았다. 혈청 총 cholesterol, LDL-cholesterol 및 간장 총 cholesterol 농도는 버섯된장 추출물 투여군 모두가 대조군에 비해 유의하게 낮았으며, 특히 ESG군이 대조군보다 혈청 총 cholesterol 20%, LDL-cholesterol 33%, 및 간장 총 cholesterol 17%가 낮게 나타났다. 버섯된장 추출물 투여군들이 대조군에 비해 유의적인 차이는 없었지만, 혈청 HDL-cholesterol은 높았고, triglyceride와 동맥경화지수는 낮게 나타났다. 혈청 총 cholesterol에 대한 HDL-cholesterol의 농도비는 버섯된장 추출물 투여균 모두에서 대조군에 비해 유의적으로 높았으며, 특히 ESG군이 대조군에 비해 35%가 높게 나타났다. 이상의 결과로 버섯된장 추출물들, 특히 ESG가 고지혈증 억제작용뿐만 아니라 관상동맥경화증을 비롯한 각종 동맥 경화증을 예방할 수 있는 가능성과 간장에서 지질 농도의 억제효과가 있음을 시사해주고 있다. The hypolipidemic effects of soybean paste containing mycelia of Phellinus linteus, Cordyceps militaris, Ganoderma lucidum were evaluated in hyperlipidemic rats. Body weight of the rats fed with soybean paste containing mycelia of Ganoderma lucidum (ESG) were significantly lower than control group whereas, there was no significant difference in body weight in other diet groups. Food intake, food efficiency ratio, and liver and kidney weights were not significantly different among the diet groups examined. However, the spleen weight of ESG group was markedly lower than other groups. Significant decreases in serum total cholesterol, LDL-cholesterol and liver total cholesterol were also observed in all diet groups tested. All groups fed with soybean paste containing mycelia of mushroom were almost equally effective in increasing plasma HDL level and decreasing the atherogenic index, whereas the ratio of HDL to total cholesterol was significantly increased in all experimental diet groups.

Pulse-Mode Dynamic Ron Measurement of Large-Scale High-Power AlGaN/GaN HFET

김민기,박영락,박준보,정동윤,전치훈,고상춘 한국전자통신연구원 2017 ETRI Journal Vol.39 No.2

We propose pulse-mode dynamic Ron measurement as a method for analyzing the effect of stress on large-scale high-power AlGaN/GaN HFETs. The measurements were carried out under the soft-switching condition (zero-voltage switching) and aimed to minimize the self-heating problem that exists with the conventional hard-switching measurement. The dynamic Ron of the fabricated AlGaN /GaN MIS-HFETs was measured under different stabilization time conditions. To do so, the drain-gate bias is set to zero after applying the off-state stress. As the stabilization time increased from 0.1 μs to 100 ms, the dynamic Ron decreased from 160 Ω to 2 Ω. This method will be useful in developing high-performance GaN power FETs suitable for use in high-efficiency converter/inverter topology design.

생식이 고지혈증 흰쥐에 미치는 영향

양병근,정상철,박준보,조성필,최영선,임상규,송치현 한국생명과학회 2001 생명과학회지 Vol.11 No.4

The hypolipidemic effect of the diet containing uncooked food was evaluated in hyperlipidemic rats. Body weightgain, food intake and food efficiency ratio were not significantly different among the diet groups examined. Significant decrease in plasma total cholesterol(8.8%), triglyceride(10.0%) and LCL-cholesterol(34.8%) were observed in uncooked food diet groups, and the liver total cholesterol and triglyceride level to the extent of 8.7% and 16.7%, respectively. Uncooked food groups substantially increased the plasma HDL to total cholesterol ratio(47.2%) and decreased the atherogenic index(37.6%) as well. Gut transit time for uncooked food was significantly higher, up to 104 minutes, compared to that of control diet group. These results suggest that uncooked food may have beneficial effects on blood lipid level and gut transit time in hyperlipidemc rats.

Efficiency improvement of a DC/DC converter using LTCC substrate

정동윤,장현규,김민기,박준보,전치훈,박종문,고상춘 한국전자통신연구원 2019 ETRI Journal Vol.41 No.6

We propose a substrate with high thermal conductivity, manufactured by the low‐temperature co‐fired ceramic (LTCC) multilayer circuit process technology, as a new DC/DC converter platform for power electronics applications. We compare the reliability and power conversion efficiency of a converter using the LTCC substrate with the one using a conventional printed circuit board (PCB) substrate, to demonstrate the superior characteristics of the LTCC substrates. The power conversion efficiencies of the LTCC‐ and PCB‐based synchronous buck converters are 95.5% and 94.5%, respectively, while those of nonsynchronous buck converters are 92.5% and 91.3%, respectively, at an output power of 100 W. To verify the reliability of the LTCC‐based converter, two types of tests were conducted. Storage temperature tests were conducted at −20 °C and 85 °C for 100 h each. The variation in efficiency after the tests was less than 0.3%. A working temperature test was conducted for 60 min, and the temperature of the converter was saturated at 58.2 °C without a decrease in efficiency. These results demonstrate the applicability of LTCC as a substrate for power conversion systems.

Power Semiconductor SMD Package Embedded in Multilayered Ceramic for Low Switching Loss

정동윤,장현규,김민기,전치훈,박준보,이현수,박종문,고상춘 한국전자통신연구원 2017 ETRI Journal Vol.39 No.6

We propose a multilayered-substrate-based power semiconductor discrete device package for a low switching loss and high heat dissipation. To verify the proposed package, cost-effective, low-temperature co-fired ceramic, multilayered substrates are used. A bare die is attached to an embedded cavity of the multilayered substrate. Because the height of the pad on the top plane of the die and the signal line on the substrate are the same, the length of the bond wires can be shortened. A large number of thermal vias with a high thermal conductivity are embedded in the multilayered substrate to increase the heat dissipation rate of the package. The packaged silicon carbide Schottky barrier diode satisfies the reliability testing of a high-temperature storage life and temperature humidity bias. At 175 °C, the forward current is 7 A at a forward voltage of 1.13 V, and the reverse leakage current is below 100 μA up to a reverse voltage of 980 V. The measured maximum reverse current (IRM), reverse recovery time (Trr), and reverse recovery charge (Qrr) are 2.4 A, 16.6 ns, and 19.92 nC, respectively, at a reverse voltage of 300 V and di/dt equal to 300 A/μs.

Design and Evaluation of Cascode GaN FET for Switching Power Conversion Systems

정동윤,박영락,이현수,전치훈,장현규,박준보,김민기,고상준,남은수 한국전자통신연구원 2017 ETRI Journal Vol.39 No.1

In this paper, we present the design and characterization analysis of a cascode GaN field-effect transistor (FET) for switching power conversion systems. To enable normally-off operation, a cascode GaN FET employs a low breakdown voltage (BV) enhancement-mode Si metal-oxide-semiconductor FET and a high-BV depletion-mode (D-mode) GaN FET. This paper demonstrates a normally-on D-mode GaN FET with high power density and high switching frequency, and presents a theoretical analysis of a hybrid cascode GaN FET design. A TO-254 packaged FET provides a drain current of 6.04 A at a drain voltage of 2 V, a BV of 520 V at a drain leakage current of 250 μA, and an on-resistance of 331 mΩ. Finally, a boost converter is used to evaluate the performance of the cascode GaN FET in power conversion applications.

전력소자의 애벌런치 에너지 분석을 위한 FPGA 설계

장현규(Hyungyu Jang),김민기,정동윤,이현수,박준보,원종일,조두형,전치훈,고상춘,박건식,박종문 대한전자공학회 2017 대한전자공학회 학술대회 Vol.2017 No.6

Analysis of Electrical Characteristics of AlGaN/GaN on Si Large SBD by Changing Structure

이현수,정동윤,박영락,장현규,이형석,전치훈,박준보,문재경,류상욱,고상춘,남은수 대한전자공학회 2017 Journal of semiconductor technology and science Vol.17 No.3

We investigated the improvement in electrical characteristics of large AlGaN/GaN on Si Schottky barrier diode (SBD) induced by structural change to achieve a better trade-off between the forward and reverse performance to obtain high power conversion efficiency in PFC converter. Using an optimized dry etch condition for a large device, we fabricated three-types of SBD with 63 mm channel width: conventional, recessed, recessed dual-anode-metal SBD. The recessed dual-anode-metal SBD exhibited a very low turn-on voltage of 0.34 V, a high forward current of 1.63 A at 1.5 V, a leakage current of 114 μA at -15 V, a breakdown voltage of 794 V.

GaN을 이용한 48-to-12 V, 100 W급 DC-DC 컨버터

장현규(Hyungyu Jang),김민기,정동윤,이현수,박준보,전치훈,고상춘,박종문 대한전자공학회 2017 대한전자공학회 학술대회 Vol.2017 No.11