• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.550-551
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• 2010

본 논문에서는 Buck Converter 동작 원리를 이용한 Full-Bridge Inverter를 제안하였다. 제안한 Full-Bridge Inverter는 왼쪽 브리지와 오른쪽 브리지의 구동 주파수를 각각 저주파와 고주파로 구동하여 Buck Converter의 동작과 유사하게 하였다. 동작은 두 가지 모드로 구분되며, 이로 인해 램프에 저주파수 구형파를 인가한다. 램프를 저주파수 구형파로 구동하여 음향공명현상을 피하게 되었으며, 고주파 스위칭으로 인덕터의 부피를 줄였다. 제안한 방법은 시뮬레이션을 통해 증명하였다.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.552-553
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• 2010

Dual Buck Inverter 구조를 갖는 35W 세라믹 MHL용 전자식 안정기의 제어회로를 설계하였다. 제어회로는 크게 2가지로 나눌 수 있는데 PFC IC를 이용하여 Inverter의 전압과 전류를 센싱하여 80kHz로 Inverter를 구동하기 위한 제어부분과 시간의 경과에 따른 PFC의 출력 전압 제어, Ignition Pulse 제어 및 무부하 보호, 램프의 점등 상태에 따른 Inverter 구동 주파수 제어부분으로 구성되어 있다. 본 논문은 마이크로 컨트롤러(ATmega8)를 이용하여 시간의 경과에 따른 안정기의 제어부분에 대해 설명하고 이를 실험을 통해 검증하였다.

• Journal of Electrical Engineering and Technology
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• v.1 no.4
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• pp.496-502
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• 2006

In this paper, we studied the development of the electronic ballast for 250W MH (Metal-Halide) lamps. We were able to improve the input power factor by using a PFC IC. To provide the lamp with the rated voltage required, we used the buck-type dc-dc converter. The stress of the switching devices in the inverter could be reduced by this method. To eliminate the acoustic resonance phenomena of MH lamps, the voltage of the lamp added the high frequency sine-wave to the low frequency square-wave by using the full bridge typed inverter. We have developed a simple igniter using the L and C elements. We could control the dimness of the lamp by varying the output voltage of the buck converter. The buck converter output voltage could be controlled by using a microprocessor.

• Restorative Dentistry and Endodontics
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• v.36 no.4
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• pp.313-323
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• 2011

Objectives: This study investigated the optimal combination of 3-component photoinitiation system, consisting of CQ, p-octyloxy-phenyl-phenyl iodonium hexafluoroantimonate (OPPI), and 2-dimethylaminoethyl methacrylate (DMAEMA) to increase the degree of conversion of resin monomers, and analyze the effect of the ratio of the photoinitiator to the co-initiator. Materials and Methods: Each photoinitiators (CQ and OPP) and co-initiator (DMAEMA) were mixed in three levels with 0.2 wt.% (low concentration, L), 1.0 wt.% (medium concentration, M), and 2.0 wt.% (high concentration, H). A total of nine groups using the Taguchi method were tested according to the following proportion of components in the photoinitiator system: LLL, LMM, LHH, MLM, MMH, MHL, HLH, HML, HHM. Each monomer was polymerized using a quartz-tungsten-halogen curing unit (Demetron 400, USA) for 5, 20, 40, 60, 300 sec and the degree of conversion (DC) was determined at each exposure time using FTIR. Results: Significant differences were found for DC values in groups. MMH group and HHM group exhibited greater initial DC than the others. No significant difference was found with the ratio of the photoinitiators (CQ, OPPI) to the co-initiator (DMAEMA). The concentrations of CQ didn't affect the DC values, but those of OPPI did strongly. Conclusions: MMH and HHM groups seem to be best ones to get increased DC. MMH group is indicated for bright, translucent color and HHM group is good for dark, opaque colored-resin.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.8
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• pp.20-26
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• 2007

A high ignition voltage is required to turn on the metal halide discharge(MHD) lamp. The igniter with high frequency resonance circuit needs more devices, such as sidac, arc-gab, SCR(silicon control rectifier), DIAC and so of which increase the complexity and decrease the reliability of the ignitor. This paper analyzes and designs a simple LC resonance type igniter without any extra switch devices. Moreover, the igniter will not influence the steady-state operation of the lamp. Through the mathematical analysis, the computer simulation and experiment results of a prototype ballast for 1[kW] metal halide lamp(MHL) lamp, the proposed igniter was verified to be effective.

• Journal of Magnetics
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• v.16 no.2
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• pp.173-176
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• 2011

Fe-Cr alloys with different Cr contents were prepared by an arc melting technique. The alloys were isochronally aged in the range from $400^{\circ}C$ to $900^{\circ}C$ with $50^{\circ}C$ steps with a holding time of 100 hours. The ageing produced embrittlement in the alloys due to either the formation of a Cr-rich ${\alpha}'$ phase or a $\sigma$ phase at high temperatures. Magnetic Hysteresis Loop (MHL) and Micro-Vickers hardness were measured at each step to correlate the magnetic and mechanical properties. Coercivity and hardness of the alloys were increased and remanence decreased up to 500-$550^{\circ}C$ due to formation of a Cr-rich ${\alpha}'$ phase. Beyond 500-$550^{\circ}C$ range, the coercivity and hardness decreased and remanence increased due to the coarsening or dissolution of the Cr-rich ${\alpha}'$ phase. In the Fe-48% Cr alloy, formation of the $\sigma$ phase at $700^{\circ}C$ reduced the maximum induction of the alloy significantly.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.6
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• pp.1-7
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• 2007

In this paper, It evaluated visibility about Metal Halide Lamp(MHL), High Pressure Sodium Lamp(HPS) and PLS(Plasma Lighting System) as Road lighting source in fog conditions. To evaluate visibility, it analyzed valuation of subjects about each light sources in special fog conditions. In result, it obtained that High Pressure Sodium Lamp has best visibility in photopic vision and PLS has best visibility in scotopic vision. This result is expected to help about select of Road lighting source.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.4
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• pp.721-726
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• 2000

The remarkable progress of electronics and radio communications technology has made our life abundant. On the other hand, the countermeasure of EMC becomes more important socially according to the increased use of electromagnetic waves. It had been required that the absorbing ability of an electromagnetic wave absorber is mote than 20 dB, the bandwidth of which is required through 30 MHz to 1,000 MHB for satisfying the international standard about an anechoic chamber lot EMl/EMS measurement. From November of 1998, however, the CISPR11 has accepted the extended frequency band from 30 MHz to 18 GHz in the bandwidth of EMI measurement. In this paper, we proposed the cutting corn-shaped type satisfying the above requirements and carried out broadband design using the equivalent material constants method. Moreover, we have fabricated it and compared its characteristics with simulated one.

• The Transactions of the Korean Institute of Power Electronics
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• v.7 no.1
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• pp.30-40
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• 2002

This paper studies the electronic ballast development for 250w MH lamps. We have improved the input power factor using a PFC IC. To provide the rating voltage required In the lamps, we have used the buck type dc-dc converter By this method, the stress of switching devices in inverter can be reduced. The inverter is the Full-Bridge type. To eliminate the acoustic resonance phenomena of MH lamps, we have added the high frequency sinewave voltage to the low frequency square-wave voltage to the lamp. We hove developed the igniter circuit using the L, C devices. We could control dimming of the lamp by varying the output voltage of the buck converter. The time of illuminating lamps and luminous intensity could be adjusted by season and time band. The buck converter output voltage can be controlled and the no load and over current situation were Protected by the development of the microprocessor Program.