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2016-10 09

[Faculty]Switching and Upgrading Mobile Device Circuits

Professor Yoo Chang-shik of the Department of Electronic Engineering is a researcher who studies the layouts of integrated, analog and digital circuits at Hanyang University (HYU). For the past year, as shown through his paper, “Switching Battery Charger Integrated Circuit for Mobile Devices in a 130-nm BCD MOSBCDMOS Process,” Yoo has been researching on developing an upgraded integrated circuit for mobile devices that could stand a higher voltage of electric current when charging. His research also encloses data on lengthening the lifespan of mobile phone batteries by retaining the right 'profile' shape when plugged in, which is the key determinant of long-lasting batteries. Battery Charging and Charging Profile According to Yoo’s research, a battery, when charging, must formulate and maintain the proper shape of the charging profile. That is, the time of charging and the battery voltage must meet at the right point, as shown in the diagram below- otherwise, the battery will be short-lived in the long run. When an application is in process, BCDMOS (Bipolar Complementary Metal Oxide Semiconductor) is activated. BCDMOS is an intricate type of an integrated circuit that can tolerate high currencies of electric voltage. Circuits of mobile devices, however, are incapable of enduring such high current and manifest a considerable rate of power consumption. To improve this aspect, Yoo saw the need for a stronger PMIC (Power Management Integrated Circuit) so that the BCDMOS would prevent the high electric voltage from damaging the device itself. PMICs are integrated circuits that handle and manage electric power. Charging profile for a lithium-ion battery. Photo courtesy of Professor Yoo's research paper Additionally, if the mobile device is used when it is being charged, not only the speed of charging slows down but also the amount of power consumed doubles. While this happens, the function of dividing the power for the phone to be used and charged at the same time is crucial. It was essential that Yoo managed both functions in harmony so that the final outcome would be progressive. Possible configurations for a mobile system where a battery charger supplies power (a) only to battery and (b) to both battery and system. Photo courtesy of Professor Yoo's research paper Yoo’s Research and its Meaning Yoo's academic principle as an engineer is not to be a scientist, but to be a practical engineer. Yoo places significance on the fact that his paper is the first to be academically published on the subject material, despite numerous others that virtually cover the necessity of his own research. He puts meaning to his work of systematically putting into an organized research paper what has already been created, in support of the fact that research done at a university can actually be utilized in real life. In this sense, Yoo does not expect a dramatic change or improvement in the field of electronic engineering and mobile devices, since there are plenty that have been put in use already. Nonetheless, he is proud to have turned the import-oriented item PMIC into a domestic product that can be manufactured here in Korea- a necessary development in the powerful semiconductor-producing country. Yoo is currently investing his time in developing a better PMIC. He is working on a project that goes by the name of “Designing an Innovative Analog”. Analogs are systems of displaying the successive changes in electric current or voltage, which is completely different from the digital system, which is required to operate visible and audible functions. He believes in the significance of analogs' roles as humans interact with their devices through touch screens, sound, and vision. With these functions falling behind, digital products will be met by critical hindrance on their way towards advancement. In this sense, improving the sound quality, screen definition, and manual systems of a device is indispensable. “We engineers are not scientists; we are not striving to create what is best. We’re simply making attempts to create what is moderately good at an adequate timing by appropriately applying already-existent principles and theories unveiled by scientists. That’s what engineers do,” remarked Yoo. He wanted the students of his department to invent and present to the world what they themselves need and benefit from. "In order to create something that the world needs, they have got to see the necessity of it first." Jeon Chae-yun chaeyun111@hanyang.ac.kr Photo by Kim Youn-soo