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이건(Keon Lee),강우성(Woo-Seong Kang),정태진(Tae-Jin Jung),윤광섭(Kwang-Sub Yoon) 대한전자공학회 2013 전자공학회논문지 Vol.50 No.8
본 논문에서는 고전압 공정기술을 이용하여 고속 디밍제어가 가능한 고출력-LED 드라이버를 설계하였다. 제안하는 고출력-LED 드라이버는 디밍신호를 통해서 LED에 필요한 전류량을 예측하고, 예측된 전류의 일부분을 인덕터 전류로 피드백시키는 방법을 사용하여서, LED 전류 상승시간이 최소화되도록 설계하였다. 기존 고출력-LED 드라이버의 최소 LED 전류 상승시간은 3㎲로 제한된 반면 제안하는 고출력-LED 드라이버의 최소 LED전류 상승시간은 1/10 정도로 감소되었다. 설계된 LED 드라이버는 0.35㎛ 60V BCDMOS 2-poly 4-metal 공정으로 제작되었으며 측정 결과 입력전압 12V, 9개의 백색 LED, 353mA LED전류, 1KHz 디밍주파수에서 LED전류 상승시간과 전력전달효율은 각각 240㎱, 93.7%로 측정되었다. This paper presents a high dimming ratio Power-LED driver IC with high power which is capable of controlling LEDs. In order to accomplish a high dimming ratio LED driver, the preloading inductor current methodology is proposed for the power stage of the proposed method to achieve the fast transient response time during the Power-LED load switching. The information containing the current flowing on the LEDs can be utilized to predict the amount of the current on the inductor. The minimum LED current rising time of existing high dimming ratio Power-LED driver is limited by 3㎲, however that of the proposed high dimming ratio Power-LED driver is reduced about 1/10. The LED driver is implemented with 0.35um 60V BCDMOS 2-poly 4-metal process. The measurement results show that the proposed LED driver system features the minimum rising time as small as 240ns at the dimming frequency of 1KHz with a 12V of input voltage, nine white LEDs and 353mA of LED current. The LED rising time and power conversion efficiency of the chip are measured to be 240ns and 93.72%, respectively.
수소연료전지의 성능 향상을 위한 다공성 표면에서의 물 제거에 대한 연구
이경민(Kyeong-Min LEE),박찬경(Chan-Kyung Park),손도협(Do-Hyeop Son),강우성(Woo-Seong Kang),박상혁(Sang-Hyuk Park),현승혁(Seung-Hyuk Hyun),김한상(Han-Sang Kim) 대한기계학회 2023 대한기계학회 춘추학술대회 Vol.2023 No.11
Polymer electrolyte membrane fuel cells (PEMFCs) have been considered as the power sources to replace internal combustion engines. Water is generated in the catalyst layer of PEMFC and excessive water can cause flooding. It is still an important task to remove water properly to prevent flooding. Hence, proper water management in PEMFCs is a core issue for improving performance and longevity. This study presents the experimental approach to understand the water removal behavior on porous gas diffusion layer (GDL) surfaces in the flow channel of PEMFC. To do this, a sample GDL/flow channel model was fabricated to investigate the water transport characteristics in a PEM fuel cell using direct ex-situ water visualization. Using a high-speed camera, the process from growth to detachment of water droplets is photographed for two types of GDL samples (with micro porous layer (MPL) and without MPL). The contact angle hysteresis (CAH) according to droplet aspect ratio (DAR) at water droplet detachment is mainly investigated is compared with the static contact angle (SCA) of the GDL surface. In addition, at detachment, the DAR and CAH according to air Reynolds number are compared with the SCA. These data show that the adhesion of the GDL surface has a dominant effect on water removal on porous surfaces. It is expected that the data from this study can contribute to the basic design of GDL structures with enhanced water removal characteristics.