• 전력전자학회논문지
• /
• 제26권1호
• /
• pp.25-31
• /
• 2021

This paper describes the design of a power cell-based pulsed power modulator with fast rise times. The pulse-generating section of the pulse power modulator is a series stack of power cells. Each power cell is composed of a storage capacitor, a pulse switch, and a bypass diode. When the pulse switches are turned on, the capacitors are connected in series and the sum of voltages is applied to the load. For output pulses with fast rise times, an IGBT with fast turn-on characteristics is adopted as a pulse switch and the optimized gate driving method is used. Pspice simulation is performed to account for the gate driving method. A 10 kV, 12-power cell-based pulsed power modulator is tested under resistive load and plasma reactor load. The rise times of output pulses less than 20 ns are confirmed, showing that the pulsed power modulator can be effectively applied to pulsed power applications with fast rise times.

• 한국진공학회지
• /
• 제18권3호
• /
• pp.176-185
• /
• 2009

ICP source의 성능과 구현 가능성은 impedance와 전기장, 자기장의 공간 분포에 큰 영향을 받는다. ICP source의 impedance는 ICP 안테나와 플라즈마의 impedance에 의해 결정된다. 안테나 설계에 있어서 안테나에 형성되는 고전압을 방지하고 공정 중 급격한 impedance 변화를 방지하기 위해서는 ICP source의 허수 impedance가 $-100\;ohm{\sim}+100\;ohm$의 영역에 존재하는 것이 유리하다. 플라즈마 균일도는 안테나에 흐르는 전류와 전압에 의해 형성되는 전기장 세기와 자기장 세기에 영향을 받는다. 원형 안테나와 대칭성이 개선된 안테나에 대해 전자기 simulation과 플라즈마 밀도의 공간분포를 측정하였으며 안테나 형태에 따른 전자기장과 플라즈마 밀도 분포의 개선을 확인하였다. 반경 방향 균일도를 조절하기 위해서는 일반적으로 지름이 다른 복수개의 안테나를 동심원 상에 배치하는 방법을 사용한다. 각 안테나들을 병렬로 연결한 경우 각각의 안테나의 임피던스에 따른 전류 분배 비율이 상이하며, 분배 비율을 조절하기 위해 코일 또는 capacitor를 연결할 경우 나타나는 현상을 계산하였다.

• Journal of Electrical Engineering and information Science
• /
• 제3권2호
• /
• pp.239-244
• /
• 1998

Piezoelectric pressure sensors and pyroelectric infrared detectors based on ZnO thin film have been integrated with GaAs metal-semiconductor field effect transistor (MESFET) amplifiers. Surface micromachining techniques have been applied in a GaAs MESFET process to form both microsensors and electronic circuits. The on-chip integration of microsensors such as pressure sensors and infrared detectors with GaAs integrated circuits is attractive because of the higher operating temperature up to 200 oC for GaAs devices compared to 125 oC for silicon devices and radiation hardness for infrared imaging applications. The microsensors incorporate a 1${\mu}$m-thick sputtered ZnO capacitor supported by a 2${\mu}$m-thick aluminum membrane formed on a semi-insulating GaAs substrate. The piezoelectric pressure sensor of an area 80${\times}$80 ${\mu}$m2 designed for use as a miniature microphone exhibits 2.99${\mu}$V/${\mu}$ bar sensitivity at 400Hz. The voltage responsivity and the detectivity of a single infrared detector of an area 80${\times}$80 $\mu\textrm{m}$2 is 700 V/W and 6${\times}$108cm$.$ Hz/W at 10Hz respectively, and the time constant of the sensor with the amplifying circuit is 53 ms. Circuits using 4${\mu}$m-gate GaAs MESFETs are fabricated in planar, direct ion-implanted process. The measured transconductance of a 4${\mu}$m-gate GaAs MESFET is 25.6 mS/mm and 12.4 mS/mm at 27 oC and 200oC, respectively. A differential amplifier whose voltage gain in 33.7 dB using 4${\mu}$m gate GaAs MESFETs is fabricated for high selectivity to the physical variable being sensed.

• 한국산학기술학회논문지
• /
• 제15권3호
• /
• pp.1700-1706
• /
• 2014

본 논문에서는 휴대기기용 LED 백라이트를 위한 감압형 DC-DC 변환기를 제안한다. 제안하는 변환기는 4 MHz의 높은 주파수에서 동작하며, 이것은 파워 스테이지와 컨트롤 블록의 수동소자의 면적 감소효과를 가진다. 파워스테이지는 인덕터와 출력 커패시터, 파워트랜지스터, 피드백 저항으로 이루어지며, 컨트롤 블록은 펄스폭 변조기, 오차증폭기, 오실레이터 등으로 이루어진다. 회로는 $0.35{\mu}m$ 1-poly 4-metal BCD 공정을 사용하여 설계 검증 및 레이아웃 하였다. SPICE 모의 실험 결과 시비율이 0.4 이고, 입력전압이 3.7 V 일 때, 1.8 V의 출력 전압을 가지며, 출력전류는 100 mA를 가진다. 제안하는 회로는 기존의 25~50 mA보다 큰 출력을 나타내어 고휘도의 LED 센서 구동이 가능할 것으로 보이며, 4 MHz의 스위칭 주파수를 사용하여, 변환기의 실장 면적이 종래에 비하여 30 % 정도의 감소가능할 것으로 보인다.

• Journal of Power Electronics
• /
• 제17권5호
• /
• pp.1298-1307
• /
• 2017

The constant on-time current-mode controlled (COT-CMC) switching dc-dc converter is stable, with no subharmonic oscillation in its current loop when a voltage ripple in its outer voltage loop is ignored. However, when its output capacitance is small or its feedback gain is high, subharmonic oscillation may occur in a COT-CMC buck converter with a proportional-integral (PI) compensator. To investigate the subharmonic instability of COT-CMC buck converters with a PI compensator, an accurate reduced-order asynchronous-switching map model of a COT-CMC buck converter with a PI compensator is established. Based on this, the instability behaviors caused by output capacitance and feedback gain are investigated. Furthermore, an approximate instability condition is obtained and design-oriented stability boundaries in different circuit parameter spaces are yielded. The analysis results show that the instability of COT-CMC buck converters with a PI compensator is mainly affected by the output capacitance, output capacitor equivalent series resistance (ESR), feedback gain, current-sensing gain and constant on-time. The study results of this paper are helpful for the circuit parameter design of COT-CMC switching dc-dc converters. Experimental results are provided to verify the analysis results.

• 한국재료학회지
• /
• 제17권2호
• /
• pp.96-99
• /
• 2007

The effects of post-annealing of high-k $HfO_2$ thin films grown by atomic layer deposition method were investigated by the annealing treatments of $400-600^{\circ}C$. $Pt/HfO_2/p-Si\;MOS$ capacitor structures were fabricated, and then the capacitance-voltage and current-voltage characteristics were measured to analyze the electrical characteristics of dielectric layers. The X-ray diffraction analyses revealed that the $500^{\circ}C-annealed\;HfO_2$ film remained to be amorphous, and the $600^{\circ}C-annealed\;HfO_2$ film was crystallized. The annealing treatment at $500^{\circ}C$ resulted in the highest capacitance and the lowest leakage current due to the reduction of defects in the $HfO_2$ films and non-crystallization. Our results suggest that post-annealing treatments are a critical factor in improving the characteristics of gate dielectric layer.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
• /
• 제3B권3호
• /
• pp.147-154
• /
• 2003

This paper presents a high-frequency boost type ZVS-PWM chopper-fed DC-DC power converter with a single active auxiliary edge-resonant snubber at the load stage which can be designed for power conditioners such as solar photovoltaic generation, fuel cell generation, battery and super capacitor energy storages. Its principle operation in steady-state is described in addition to a prototype setup. The experimental results of boost type ZVS-PWM chopper proposed here, are evaluated and verified with a practical design model in terms of its switching voltage and current waveforms, the switching v-i trajectory and the temperature performance of IGBT module, the actual power conversion efficiency, and the EMI of radiated and conducted emissions, and then discussed and compared with the hard switching scheme from an experimental point of view. Finally, this paper proposes a practical method to suppress parasitic oscillation due to the active auxiliary resonant switch at ZCS turn-off mode transition with the aid of an additional lossless clamping diode loop, and can be reduced the EMI conducted emission.

• 한국산업융합학회 논문집
• /
• 제23권2_1호
• /
• pp.115-124
• /
• 2020

In wireless power transfer (WPT) system, the conventional compensation topologies only can provide a constant current (CC) or constant voltage (CV) output under their resonant conditions. It is difficult to meet the CC and CV hybrid charging requirements without any other schemes. In this study, a switching hybrid topology (SHT) is proposed for CC and CV electric vehicle (EV) battery charging. By utilizing an additional capacitor and two AC switches (ACSs), a double-side LCC (DS-LCC) and an inductor and double capacitors-series (LCC-S) topologies are combined. According to the specified CC and CV charging profile, the CC and CV charging modes can be flexibly converted by the two additional ACSs. In addition, zero phase angle (ZPA) also can be achieved in both charging modes. In this method, because the operating frequency is fixed, without using PWM control, and only a small number of devices are added, it has the benefits of low-cost, easy-controllability and high efficiency. A 3.3-kW experimental prototype is configured to verify the proposed switching hybrid charger. The maximum DC efficiencies (at 3.3-kW) of the proposed SHT is 92.58%.

• 전기전자학회논문지
• /
• 제23권3호
• /
• pp.994-1002
• /
• 2019

본 논문은 농업용 전기차량의 전기식 동력인출장치용 전력변환시스템에 대해 제안한다. 대부분의 전기식 동력인출장치(Electric Power Take-Off : e-PTO)는 상용전원 $220V_{AC}$를 사용한다. 농업용 전기차량의 낮은 배터리 전압을 사용하여 높은 출력 전압을 공급하기 위한 DC-DC 컨버터와 DC-AC 인버터로 구성된 2단 구조를 갖는 양방향 전력변환시스템이 적합하다. 제안하는 전력변환시스템은 1단의 Dual Active Bridge(DAB)컨버터와 2단의 양방향 풀 브릿지 인버터로 구성된다. 또한, 초기 구동시 DC 버스단 커패시터 충전에 의해 발생되는 돌입 전류 저감을 위해 소프트 스타트 알고리즘을 제안한다. 3kW급 전력변환시스템 시제품 및 알고리즘을 구현하고 실험을 통해서 실용성을 입증하였다.

• Journal of Power Electronics
• /
• 제19권3호
• /
• pp.702-713
• /
• 2019

Multilevel Inverters (MLIs) are widely used in medium voltage applications due to their various advantages. In addition, there are numerous types of MLIs for such applications. However, the diode-less 3-level (3L) T-type Neutral Point Clamped (NPC) MLI is the most advantageous due to its low conduction losses and high potential efficiency. The power circuit of a 3L T-type NPC is derived by the conventional two level inverter by a slight modification. In order to explore the MLI performance for various Pulse Width Modulation (PWM) schemes, this paper examines the operation of a 3L (five level line to line) T-type NPC MLI for various types of Multi-Carriers Pulse Width Modulation (MCPWM) schemes. These PWM schemes are compared in terms of their voltage profile, total harmonic distortion (THD) and conduction losses. In addition, a 3L T-type NPC MLI is also compared with the conventional NPC in terms of number of switches, clamping diodes, main diodes and capacitors. Moreover, the capacitor-balancing problem is also investigated using the Neutral Point Fluctuation (NPF) method with all of the MCPWM schemes. A 1kW 3L T-type NPC MLI is simulated in MATLAB/Simulink and implemented experimentally and its performance is tested with a 1HP induction motor. The results indicate that the 3L T-type NPC MLI has better performance than conventional NPC MLIs.