• Journal of Power Electronics
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• 제12권6호
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• pp.869-877
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• 2012

This paper presents a current-balancing circuit for security lights that uses parallel-connected LEDs. The parallel connection of LEDs causes current differences between the LED strings because of characteristic deviations. These differences can reduce the lifespan of a particular point of LEDs by thermal spotting. They can also cause non-uniform luminance of the lighting device. Among the different methods for solving these problems, the method using current-balancing transformers makes it easy to compensate for current differences and it has a simple circuitry. However, while the balancing transformer has been applied to AC light sources, LEDs operate on a DC source, so the driving circuitry and the design method have to be changed and their performances must be verified. Thus in this paper, a design method of the balancing transformer network and the driving circuitry for LEDs is proposed. The proposed design method could have a smaller size than the conventional design method. The proposed circuitry is applied to three types of 100-watt LED security lights, which use different LEDs. Experimental results are presented to verify the performance of the designed driving circuits.

• 한국산학기술학회논문지
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• 제20권3호
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• pp.491-499
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• 2019

최근에, 전원 공급 장치에 있어서 파워의 품질에 대한 요구가 높아지고 있다. IEC 61000-3-2 규격은 조명을 위한 AC/DC 전원 공급 장치에 대하여 역률(PF)과 전체 파형 왜곡률(THD)에 대한 규격을 만족하도록 요구하고 있다. 또 출력단의 전류 변화에 의해 발광체 광량이 바뀜에 따라 발생되는 플리커 현상에 대해 유럽권 선진국가는 ripple rate의 기준을 15~30%로 설정해 규제하고 있다. 따라서 국내에서도 기준을 마련하고 규제를 추진 중에 있다. 그래서 본 논문은 PFC 규격을 만족하고, 회로 1차, 2차 간 절연 기능을 가지기 위해 Flyback 컨버터를 적용하며, LED 전류의 저주파 리플을 저감하기 위해 Flyback, Coupled Inductor, LC 병렬 공진 필터, LLC 공진 필터, Cuk을 이용한 각각의 LED 구동회로를 PSIM을 통해 시뮬레이션 함으로써 각각의 방식들을 비교하였으며, 출력측 리플 저감을 위해 1차측에 Coupled Inductor와 2차측에 LC 공진을 적용한 Coupled LC 공진 회로를 제안하였으며, Coupled LC 공진 방식은 출력 커패시터가 78uF으로 작으며, 출력 리플은 전압 2.38V, 전류 0.05A로 기존의 방식보다 22%의 출력 리플 저감을 확인 하였다.

• The Korean Journal of Physiology and Pharmacology
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• 제22권6호
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• pp.671-677
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• 2018

In the present study, we investigated whether tussilagone, a natural product derived from Tussilago farfara, significantly affects the production and gene expression of airway MUC5AC mucin. Confluent NCI-H292 cells were pretreated with tussilagone for 30 min and then stimulated with EGF (epidermal growth factor) or PMA (phorbol 12-myristate 13-acetate) for 24 h or the indicated periods. The MUC5AC mucin gene expression was measured by RT-PCR. Production of MUC5AC mucin protein was measured by ELISA. To elucidate the action mechanism of tussilagone, effect of tussilagone on PMA-induced $NF-{\kappa}B$ signaling pathway was investigated by western blot analysis. Tussilagone significantly inhibited the production of MUC5AC mucin protein and down-regulated the expression of MUC5AC mucin gene, induced by EGF or PMA. Tussilagone inhibited PMA-induced activation (phosphorylation) of inhibitory kappa B kinase (IKK), and thus phosphorylation and degradation of inhibitory kappa Ba ($I{\kappa}B{\alpha}$). Tussilagone inhibited PMA-induced phosphorylation and nuclear translocation of nuclear factor kappa B ($NF-{\kappa}B$) p65. This, in turn, led to the down-regulation of MUC5AC protein production in NCI-H292 cells. These results suggest that tussilagone can regulate the production and gene expression of mucin by acting on airway epithelial cells through regulation of $NF-{\kappa}B$ signaling pathway.

• 공업화학
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• 제31권5호
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• pp.552-559
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• 2020

Activated carbon-nickel (II) oxide (AC-NiO) electrodes were studied as materials for the capacitive deionization (CDI) of aqueous sodium chloride solution. AC-NiO electrodes were fabricated through physical mixing and low-temperature heating of precursor materials. The amount of NiO in the electrodes was varied and its effect on the deionization performance was investigated using a single-pass mode CDI setup. The pure activated carbon electrode showed the highest specific surface area among the electrodes. However, the AC-NiO electrode with approximately 10 and 20% of NiO displayed better deionization performance. The addition of a dielectric material like NiO to the carbon material resulted in the enhancement of the electric field, which eventually led to an improved deionization performance. Among all as-prepared electrodes, the AC-NiO electrode with approximately 10% of NiO gave the highest salt adsorption capacity and charge efficiency, which are equal to 7.46 mg/g and 90.1%, respectively. This finding can be attributed to the optimum enhancement of the physical and chemical characteristics of the electrode brought by the addition of the appropriate amount of NiO.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2002년도 추계학술대회 논문집
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• pp.373-378
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• 2002

Metal matrix composites have a great interest in recent years because high specific strength, high specific stiffness characteristics, and application ranges of the composites are extend to variety industry. In this paper, an investigation was performed on the plane strain fracture toughness and slinding wear properties of AC4CH alloy(Al-Si-Mg line) reinforced with 20wt% aluminum borate whisker expect one, which contained a inorganic binder($TiO_2$). the binder led to the formation of strengthen the whisker each other. The test of fracture toughness was using CT(half size) specimen of thickness 12.5mm, width 25mm. and test of slinding wear of using tribo a pin-on-disk machine and lubricant is used without paraffine 8.2CST at room temperature. As results, Fracture toughness $K_{IC}$ is $8.7MPa-m^{05}$ for ABOw/AC4CH, $9.28MPa-m^{05}$ for ABOw/AC4CH added $TiO_2$. but AC4CH alloy was violated the critical stipulated by ASTM standard for valid measurement of $K_{IC}$. In case of, it was performed $J_{IC}$ test instead of $K_{IC}$ based on ASTM E 1820.

• Journal of Power Electronics
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• 제18권2호
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• pp.640-650
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• 2018

A TRIAC dimmable LED driver with a wide tuning range and a two-stage uniform dimming scheme is proposed in this paper. To solve the restricted dimming range problem caused by the limited conduction ratio of TRIAC dimmers, a conduction ratio compensation technique is introduced, which can increase the output current up to the rated output current when the TRIAC dimmer turns to the maximum conduction ratio. For further optimization, a two-stage uniform dimming diagram with a rapid dimming curve and a slow dimming curve is designed to make the LED driver regulated visually uniform in the whole adjustable range of the TRIAC dimmer. The proposed control chip is fabricated in a TSMC $0.35{\mu}m$ 5V/650V CMOS/LDMOS process, and verified on a 21V/500mA circuit prototype. The test results show that, in the 90V/60Hz~132V/60Hz ac input range, the voltage linear regulation is 2.6%, the power factor is 99.5% and the efficiency is 83%. Moreover, in the dimming mode, the dimming rate is less than 1% when the maximum dimming current is 516mA and the minimum dimming current is only about 5mA.

• 한국전기전자재료학회논문지
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• 제14권8호
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• pp.679-687
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• 2001

It is known that amorphous BaTiO$_3$ thin films have good insulating properties[1][2]. In this investigation, amorphous BaTiO$_3$ thin films were deposited by rf magnetron sputtering on thick BaTiO$_3$ films of AC powder EL devices which were fabricated by screen-printing. The electrical and optical properties of the EL devices were then investigated. Adding amorphous BaTiO$_3$ thin film, it showed that leakage current density was decreased. Especially, leakage current density was decreased more with he sample of 0.5-hour deposition than the sample of 4-hours deposition. This result led to the improvement of luminous efficiency by 11%. It could be concluded that proper amorphous BaTiO$_3$ thin film deposition improved the surface property of dielectric layer.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 E
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• pp.2227-2229
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• 1999

As a direct-view flat panel displays, there are many devices, such as plasma display panels(PDPs), vacuum fluorescent displays (VFDs), and light emitting diode(LED). Among these, a PDP is the first type of panel display to be made commercially available. A 'Plasma display' is the general term for a flat display utilizing the light emission that is produced by gas discharge. However, the brightness and Luminous efficiency are still not adequate for consumer television. So, the new sustain electrode type of ac PDP was proposed. By arranging the transparent electrode of quadrangle by zigzag, the area of electrode are reduced, and the length of electrode gap is increased. It generates a high luminous efficiency(corresponding to a 40% improvement of standard type), the same discharge voltage characteristics, and the low power consumption at same luminance.

• 한국안전학회지
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• 제29권3호
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• pp.34-38
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• 2014

In Display such as LCD, LED, and AMOLED or semiconductor related industries are required to have static ionizer in order to produce reliable goods since the ionizer can create balanced ion that is delivered to producing goods to minimize electrical damages when manufacturing. However, the most general type of ionization is called, "Corona Discharge" that has a slight chances to generate unequal and unstable amount of each +/- ion to the target object. Then, the ionization performance will drastically decrease and end up with quality deterioration problem. In this research, our objective to resolve the current issue via applying "Coupling Condenser" on each counter electrodes of Corona discharging type ionizer. The result is that the ion balance was maintained the satisfied range that is within +/-100V when we changed the duty ratio of the High Voltage of Pulse AC about 40 ~ 70%. In addition, when levelling the High Voltage of Pulse AC, the ion balance holds the range within +20 ~ 0V. Even though we have tested the same experiment for a year, we have seen the range changes roughly ${\pm}50V$.

• Journal of Power Electronics
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• 제18권6호
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• pp.1642-1649
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• 2018

A single-stage flyback LED AC-DC converter based on primary-side control under constant current mode is proposed in this study. The proposed converter features low total harmonic distortion (THD) and high power factor (PF). It also consists of a zero-crossing distortion compensation circuit and a variable duty ratio control compensation circuit to deal with the line current distortions caused by fixed duty ratio control. The system model and layout are built in Simplis and Cadence, respectively. The feasibility and performance of the proposed circuit is verified by designing and fabricating an IC controller in the HHNEC $0.35{\mu}m$ 5 V/40 V HVCMOS process. Experimental results show that the PF can reach a level in the range of 0.985-0.9965. Moreover, the average THD of the entire system is approximately 10%, with the minimum being 6.305%, as the input line voltage changes from 85 VAC to 265 VAC.