• The Korean Journal of Ceramics
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• 제5권4호
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• pp.353-356
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• 1999

Highly proten-conductive elastic composites have been successfully prepared from $H_3PO_4$-doped silica gel and styrene-ethylene-butylene-styrene block elastic copolymer. In addition solid state electric double-layer capacitors have been fabricated using the composite as an electrolyte and activated carbon powders(ACP) hybridized with the composite as a polrizable electrode. The cyclic voltammogram of the electric double-layer capacitor fabricated demonstrated that electric charge was stored in the elecric double-layer at the interface between the polarizable electrode and the electrolyte. The value of capacitance of the capacitor was 10 F/(gram of total ACP), which was comparable to that of the capacitors using conventional liquid electrolytes.

• 전기학회논문지P
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• 제61권1호
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• pp.41-46
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• 2012

Electrolytic power capacitors have been widely used in power conversion system such as inverter or UPS because of characteristics of large capacitance, high-voltage and low-cost. The electrolytic capacitor, which is most of the time affected by the aging effect, plays a very important role for the power-electronics system quality and reliability. Therefore it is important to diagnosis monitoring the condition of an electrolytic capacitor in real-time to predict the failure. In this paper, the on-line remote diagnosis monitoring system for UPS DC link electrolytic capacitors using low-cost single-chip zigbee communication modules is developed. To estimate the health status of the capacitor, the equivalent series resistor(ESR) of the component has to be determined. The capacitor ESR is estimated by using RMS computation using BPF modeling of DC link ripple voltage/current. Zigbee-based hardware experimental results show that the proposed remote capacitor diagnosis monitoring system can be applied to UPS successfully.

• 전기학회논문지
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• 제61권11호
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• pp.1625-1633
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• 2012

In the lighting industry, a Lighting Emitting Diode (LED) is increasingly used because of many advantages and a eco-friendly product comparing with the conventional lighting. However, the LED lighting has to include various AC/DC converters because the direct current is used for the LED lighting. Among a lot of power converters, the flyback converter is widely used for the LED lighting and includes some electrolytic capacitors for the voltage regulation. But the electrolytic capacitor has shorter lifetime than the LED element. It makes the expected life-time of the converter having the electrolytic capacitor shorter than the LED element. This paper proposes the single-stage PFC flyback converter without electrolytic capacitors. To verify the performance of the proposed converter, simulated and experimental works were carried out.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(2)
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• pp.606-610
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• 2003

This paper presents a simple carrier symmetric method for the voltage balance of flying capacitors in FCMLI(flying capacitor multi-level inverter). To achieve the voltage balance of flying capacitors, the utilization of each carrier must be balanced during a half-cycle of the switching period such as PSPWM(Phase-Shifted PWM). However, the CRPWM(Carrier Redistribution PWM) method causes the fluctuation of flying capacitor voltages because the balanced utilization of carriers is not achieved. Moreover, it does not consider that the load current change has an influence on flying capacitor voltages by assuming that the current flows Into the load. To overcome the drawbacks of CRPWM, it is modified by the technique that carriers of each band are disposed symmetrically at every fundamental period. Firstly, the CRPWN method is reviewed and the theory on voltage balance of flying capacitors is analyzed. The proposed method Is introduced and is verified through the experiment result.

• 전력전자학회논문지
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• 제22권4호
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• pp.277-284
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• 2017

For passive power factor correction, the valley fill circuit approach is attractive for low power applications because of low cost, high efficiency, and simple circuit design. However, to vouch for the product quality, two dc-link capacitors in the valley fill circuit should be selected to withstand the peak rectified ac input voltage. The common mode (CM) and differential mode (DM) choke should be used to suppress the electromagnetic interference (EMI) noise, thereby resulting in large size volume product. This paper presents the practical design and implementation of a valley fill flyback converter with reduced dc link capacitors and EMI magnetic volumes. By using the proposed over voltage protection circuit, dc-link capacitors in the valley fill circuit can be selected to withstand half the peak rectified ac input voltage, and the proposed CM/DM choke can be successfully adopted. The proposed circuit effectiveness is shown by simulation and experimentally verified by a 78W prototype.

• 전력전자학회논문지
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• 제22권4호
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• pp.369-372
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• 2017

This paper presents a control scheme for three-level NPC inverters using small DC-link capacitors. To reduce the inverter system volume, the film capacitor with small capacitance is a promising candidate for the DC-link. When small capacitors are applied in a three level inverter, however, the AC ripple component increases in the DC-link NPV (neutral point voltage). In addition, the three-phase input grid currents are distorted when the DC-link capacitors are fed by diode rectifier. In this paper, the additional circuit is applied to compensate for small capacitor systems defect, and the offset voltage injection method is presented for the stabilization in NPV. These two proposed processes evidently ensure the quality improvement of the input grid currents and output load currents. The feasibility of the proposed method is verified by experimental results.

• 대한전자공학회논문지SD
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• 제37권10호
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• pp.25-32
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• 2000

본 연구에서는 강유전체의 이력 특성을 정밀하게 계산하기 위한 모델을 제공하였다. 본 모델은 2중 전위우물에 근거한 반경험적 분극 천이 모델에 기초하고 있으며 프라이사흐의 이력 함수의 분포 모델의 물리적 특성과도 잘 일치되고 있음을 보였다. 본 모델은 강유전체 이력 특성의 천이 경사도와 임프린트 특성을 고려하고 있으며 인가 전압의 극성이 바뀌는 경우에 발생되는 부 이력 경로에 대해서도 정확하게 분극 전하의 변화를 표현하고 있음을 보였다. 본 모델의 예측 결과는 PZT와 SBT의 두 종류의 강유전체에 대해서 측정 결과와 잘 일치하고 있음을 보였다. 또한, 본 모델을 AHDL 코드로 구현하여 스펙트레 시뮬레이터를 통하여 회로 설계를 할 수 있는 환경을 제공하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2005년도 전력전자학술대회 논문집
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• pp.298-301
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• 2005

The flying capacitor voltage control of the flying capacitor multi-level inverter (FCMLI) is very important for safe operation. The voltage unbalancing of flying capacitors caused serious problems in safety and reliability of system. In the FCMLI, balancing problem of the flying capacitor has its applications limited. The voltage unbalance is occurred by the difference of each capacitors charging and discharging time applied to FCMLI. This paper investigates and analyzes multi-carrier PWM methods to solve capacitor voltage balancing problem. The Phase-Shift PWM (PSPWM) method that is commonly used, The Modified Carrier-Redistribution PWM (MCRPWM) method and The Saw-Tooth-Rotation PWM (STRPWM) method are discussed and compared with respect to switching state, balancing voltage of capacitors and output waveform. These three PWM methods are analyzed by using a flying capacitor three-level inverter and provided result through simulation. Finally, the harmonics about the output voltages of their methods are compared using the harmonic distortion factor (HDF).

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
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• pp.329-332
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• 1999

In this paper, BST((Bao.&o,dTi0:3) thin films were deposited by the rf magnetron sputtering method on Pt/$SiO_2$/Si substrate. Pt, $RuO_2$, Ag, Cu films for the formation of top electrode were deposited on BST thm films. And then Top Electrodes/BST/Pt capacitors were annealed with rapid thermal annealing(RTA) at various temperature. We have investigated effect of post-annealing on the electrical properties such as dielectric constant and leakage current of the capacitors. It was found that electrical properties of the capacitors were greatly depended on the annealing temperatures as well as the materials of top electrodes. In BST thin films with Pt top electrode was annealed at $700^{\circ}C$. the dielectric constant was measured to the value of 346 at l[kHzl and the leakage current was obtained to the value of $8.76\times10^8$[A/$\textrm{cm}^2$] at the forward bias of 2[V].

• Journal of Power Electronics
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• 제15권1호
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• pp.31-38
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• 2015

In this paper, a buck-boost type battery charger is developed for charging battery set with a lower voltage. This battery charger is configured by a rectifier circuit, an integrated boost/buck power converter and a switched capacitors circuit. A boost power converter and a buck power converter sharing a common power electronic switch are integrated to form the integrated boost/buck power converter. By controlling the common power electronic switch, the battery charger performs a hybrid constant-current/constant-voltage charging method and gets a high input power factor. Accordingly, both the power circuit and the control circuit of the developed battery charger are simplified. The switched capacitors circuit is applied to be the output of the boost converter and the input of the buck converter. The switched capacitors circuit can change its voltage according to the utility voltage so as to reduce the step-up voltage gain of the boost converter when the utility voltage is small. Hence, the power efficiency of a buck-boost type battery charger can be improved. Moreover, the step-down voltage gain of the buck power converter is reduced to increase the controllable range of the duty ratio for the common power electronic switch. A prototype is developed and tested to verify the performance of the proposed battery charger.