• 전력전자학회논문지
• /
• 제25권3호
• /
• pp.195-203
• /
• 2020

This paper presents a parasitic inductance reduction design method for the stable driving of GaN HEMT. To reduce the parasitic inductance, we propose a vertical lattice loop structure with multiple loops that is not affected by the GaN HEMT package. The proposed vertical lattice loop structure selects the reference loop and designs the same loop as the reference loop by layering. The design reverses the current direction of adjacent current paths, increasing magnetic flux cancellation to reduce parasitic inductance. In this study, we validate the effectiveness of the parasitic inductance reduction method of the proposed vertical lattice loop structure.

• 한국전자파학회논문지
• /
• 제21권6호
• /
• pp.706-713
• /
• 2010

본 논문에서는 기생 루프 구조를 이용한 휴대 단말기용 5중 대역 초소형 루프 안테나를 제안한다. 제안된 안테나는 급전 모노폴, 기생 루프 구조를 가진 방사 루프 안테나, 추가 방사 소자로 구성되며, 매우 얇은 연성기판으로 제작된 안테나는 40 mm$\times$11 mm$\times$3 mm 크기의 유전체 캐리어에 장착된다. 제안된 안테나의 대역폭은 저대역에서 402 MHz(773~1,175 MHz)이고, 고대역에서 583 MHz(1,622~2,205 MHz)이다. 그 결과, 제안된 안테나는 VSWR 3:1 기준으로 GSM850, GSM900, DCS1800, PCS1,900, WCDMA 대역을 모두 만족함을 확인할 수 있었고, 방사 패턴, 이득, 효율 측면에서 휴대용 단말기에 적용되기에 적합한 성능을 얻었다. 따라서 제안된 안테나는 초소형 다중 대역 휴대 단말기의 응용 분야에 적합할 것으로 판단된다.

• 한국전자파학회논문지
• /
• 제14권6호
• /
• pp.550-557
• /
• 2003

본 논문에서는 GPS/PCS 단말기에 적합한 두 가지 형태의 듀얼밴드 내장형 안테나를 제안하였다. 먼저 기생 다이폴이 포함된 모노폴 안테나는 단말기 기판에 직접 인쇄가 가능하도록 설계하였고, 격자형 루프구조의 안테나는 단말기의 내부 공간을 최대한으로 활용하기 위하여 격자형으로 구부러진 형태로 디자인하여 단말기 내부 에 내장이 가능하도록 설계하였다. 제안된 두 가지 형태의 듀얼밴드 내장형 안테나의 대역폭은 정재파비 2:1 기준으로 최소 19.1 % 이상으로 GPS 대역과 PCS 대역을 동시에 만족할 수 있고 전 대역에서 -0.4 ㏈i~3.33 ㏈i의 만족할만한 이득을 얻었으며 방사패턴은 전 방향성에 가까움을 확인하였다.

• Journal of Power Electronics
• /
• 제13권6호
• /
• pp.964-974
• /
• 2013

A modified direct torque control (DTC) method based on torque angle is proposed for interior permanent-magnet synchronous motor (IPMSM) drivers used in electric vehicles (EVs). Given the close relationship between torque and torque angle, proper voltage vectors are selected by the proposed DTC method to change the torque angle rapidly and regulate the torque quickly. The amplitude and angle of the voltage vectors are determined by the torque loop and stator flux-linkage loop, respectively, with the help of the position of the stator flux linkage. Furthermore, to satisfy the torque performance request of EVs, the nonlinear dead-time of the invertor caused by parasitic capacitances is considered and compensated to improve steady torque performance. The stable operation region of the IPMSM DTC driver for voltage and current limits is investigated for reliability. The experimental results prove that the proposed DTC has good torque performance with a brief control structure.

• 한국진공학회지
• /
• 제8권4B호
• /
• pp.536-540
• /
• 1999

We have developed a refractory WNx self-aligned gate GaAs metal-semiconductor field-effect transistor(MESFET) using $SiO_2$ side-wall process. The MESFET hasa fully ion-implanted, planar, symmetric self-alignment structure, and it is quite suitable for integration. The uniform trans-conductance of 354nS/mm up to Vgs=+0.6V and the saturation current of 171mA/mm were obtained. As high as 43GHz of cut-off frequency hs been realized without any de-embedding of parasitic effects. The refractory WNx self-aligned gate GaAs MESFET technology is one of the most promising candidates for realizing linear power amplifier ICs and multifunction monolithic ICs for use in the digital mobile communication systems such as hand-held phone(HHP), personal communication system (PCS) and wireless local loop(WLL).

• Journal of Power Electronics
• /
• 제18권2호
• /
• pp.375-382
• /
• 2018

A novel active controlled primary current cutting-off zero-voltage and zero-current switching (ZVZCS) PWM three-level dc-dc converter (TLC) is proposed in this paper. The proposed converter has some attractive advantages. The OFF voltage on the primary switches is only Vin/2 due to the series connected structure. The leading-leg switches can obtain zero-voltage switching (ZVS), and the lagging-leg switches can achieve zero-current switching (ZCS) in a wide load range. Two MOSFETs, referred to as cutting-off MOSFETs, with an ultra-low on-state resistance are used as active controlled primary current cutting-off components, and the added conduction loss can be neglected. The added MOSFETs are switched ON and OFF with ZCS that is irrelevant to the load current. Thus, the auxiliary switching loss can be significantly minimized. In addition, these MOSFETs are not series connected in the circuit loop of the dc input bus bar and the primary switches, which results in a low parasitic inductance. The operation principle and some relevant analyses are provided, and a 6-kW laboratory prototype is built to verify the proposed converter.

• 한국신재생에너지학회:학술대회논문집
• /
• 한국신재생에너지학회 2010년도 추계학술대회 초록집
• /
• pp.73.1-73.1
• /
• 2010

For the successful cold starting of a fuel cell engine, either internal of external heat supply must be made to overcome the formation of ice from water below the freezing point of water. In the present study, switchable vanadium oxide compounds as variable temperature-electrical resistance materials onto the surface of flat metallic bipolar plates have been prepared by a dip-coating technique via an aqueous sol-gel method. Subsequently, the chemical composition and micro-structure of the polycrystalline solid thin films were analyzed by X-ray diffraction, X-ray fluorescence spectroscopy, and field emission scanning electron microscopy. In addition, it was carefully measured electrical resistance hysteresis loop over a temperature range from $-20^{\circ}C$ to $80^{\circ}C$ using the four-point probe method. The experimental results revealed that the thin films was mainly composed of Karelianite $V_2O_3$ which acts as negative temperature coefficient materials. Also, it was found that thermal dissipation rate of the vanadium oxide thin films partially satisfy about 50% saving of the substantial amount of energy required for ice melting at $-20^{\circ}C$. Moreover, electrical resistances of the vanadium-based materials converge on an extremely small value similar to that of pure flat metallic bipolar plates at higher temperature, i.e. $T{\geq}40^{\circ}C$. As a consequence, experimental studies proved that it is possible to apply the variable temperature-electrical resistance material based on vanadium oxides for the cold starting enhancement of a fuel cell vehicle and minimize parasitic power loss and eliminate any necessity for external equipment for heat supply in freezing conditions.