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RISS 인기검색어
- 검색키워드
- 저자 : Cheol-O Yeon (검색결과 43 건)
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Cheol-O Yeon,Dong Kwan Kim,Jae-Bum Lee,Jong-Woo Kim,Cheon-Yong Lim,Gun-Woo Moon 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
In this paper, a half-bridge (HB) LLC resonant converter which has been used for server power supply, is controlled by digital controller. In order to increase the entire load efficiency of HB LLC converter, a synchronous rectifier (SR) should has a robust control at any condition such as PFC noise or the lack of current sensing. For these reason, digital controller with LLC SR control is preferred in server power supply market. In this paper, the optimal SR ON-time control which operates as a constant ON-time at below region, and the same ON-time of primary switch at above region, is implemented. However, the problems of optimal SR ON-time control still exist. Because of senseless operation, when the ON-time of SR is larger than the half period of LLC resonant tank, the current of converter flows reversely and it will make the big surge current which damage to active devices. From this result, the ON-time of SR should be shorter than the half period of LLC resonant tank. Moreover, in the case of current unbalance in center-tapped rectifier, the conducting time of rectifiers is different due to the parasitic components. Since the powering periods of two SR are different, the SR ON-time of HB LLC resonant converter should be determined by minimum conducting time of rectifiers. This result causes a large conduction loss of body diodes which makes the low efficiency or the reliability problem of LLC resonant converter. Therefore, HB LLC resonant converter with optimal SR ON-time control is implemented and the asymmetric duty control is proposed in this paper, which solves the current unbalance problem in center-tapped rectifier. Therefore, the LLC resonant converter which has wide input variation, can achieve the high efficiency with optimal SR ON-time control and eliminate the current unbalance problem with asymmetric duty control.
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Yeon, Cheol-O,Kim, Jong-Woo,Park, Moo-Hyun,Lee, Il-Oun,Moon, Gun-Woo IEEE 2017 IEEE TRANSACTIONS ON POWER ELECTRONICS - Vol.32 No.9
<P>Generally, an LLC series resonant converter (LLC SRC) is an attractive topology for applications, which require wide input variation and high conversion efficiency because of its wide gain capability and soft-switching capability. However, there is a regulation problem in which the output voltage increases as the load current decreases. In this paper, Bode plot and impedance asymptote analysis were conducted to obtain an intuitive sense of the regulation characteristic of LLC SRC under the light-load condition. Moreover, to improve the regulation capability, a new resonant tank with an additional capacitor is proposed. Its design guidelines were determined by Bode plot and impedance asymptote analysis. Therefore, the proposed LLC SRC achieves very light load regulation, while it maintains the advantages of typical LLC SRCs.</P>
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Cheol-O Yeon,Jae-Bum Lee,Il-Oun Lee,Gun-Woo Moon Institute of Electrical and Electronics Engineers 2016 IEEE transactions on industrial electronics Vol.63 No.5
<P>A conventional asymmetrical half-bridge (AHB) converter is widely used for dc-dc stage in low-to-medium power system. However, since the asymmetric operation of AHB converter causes the low efficiency over entire load condition, the conventional AHB converter is not usually considered for the candidate of server power system. In order to overcome the problems of the conventional AHB converter, a wide zero-voltage-switching (ZVS) range AHB converter with a clamp switch and a clamp diode is proposed in this paper. The proposed AHB converter (PAHBC) replaces a low-side clamp diode with a MOSFET switch and adds an auxiliary winding, which changes the transformer turns-ratio. From these modifications and the pulsewidth-modulation (PWM) control of clamp switch, the PAHBC can be designed optimally at nominal input condition and obtains additional dc gain at hold-up time condition. These advantages achieve the high conversion efficiency over the entire load condition. The operational principle and analysis of the PAHBC are presented in this paper and verified by a 340-400 V input and 50 V/500 W output laboratory prototype.</P>
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보행자 보호를 위한 보행자-차량 충돌안전기준 개발 연구
오철(O, Cheol),강연수(Gang, Yeon-Su),이재완(Lee, Jae-Wan),김범일(Kim, Beom-Il) 대한교통학회 2005 대한교통학회 학술대회지 Vol.48 No.-
교통안전 증진을 위한 대응책 마련은 크게 두 가지 관점에서 접근해 볼 수 있다. 첫째는, 사고를 미연에 방지하기 위한 ‘교통사고 예방’이고, 둘째는 사고 발생 후 ‘교통사고 심각도의 최소화’이다. 교통사고 예방분야에서는 법적, 제도적 측면에서 교통안전을 제고하려는 노력과 함께 차량에 첨단기술을 적용하여 안전운전을 지원하는 시스템의 도입 등이 좋은 예이다. 전통적인 교통안전 분야, 첨단교통체계 (ITS: Intelligent Transportation Systems) 및 자동차 공학 분야에서 이미 많은 노력을 기울여 괄목할 만한 성과를 거두고 있으며, 관련 기술의 진보는 앞으로의 전망을 보다 밝게 하고 있다. 한편, 교통사고의 심각도 감소와 관련해서는 주로 차대차 교통사고 발생시 차량탑승자의 보호를 위한 분야 위주로 기술의 연구, 개발 및 실용화가 추진되어 왔다. 반면에 교통체계를 구성하는 주요 요소 중의 하나인 보행자의 보행 안전성을 보장하려는 노력은 상대적으로 미흡했던 것이 사실이다. 특히, 우리나라의 경우 자동차 위주의 교통체계와 보행자 경시 운전습관으로 인하여 도로교통 사망사고 중 차대 보행자 사고의 비율이 38%에 달하고 있다. 이러한 수치는 미국의 14.1%, 프랑스의 12.5%, 독일의 15.9%, 일본의 27.7% 등에 비해 2~3배 높은 것으로 나타나, 이에 따른 대책 마련이 대단히 시급한 때라고 할 수 있다.
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