Type of Document Master's Thesis Author Qin, Yaxiao Author's Email Address firstname.lastname@example.org URN etd-08232012-143512 Title High Efficiency SEPIC Converter For High Brightness Light Emitting Diodes (LEDs) System Degree Master of Science Department Electrical and Computer Engineering Advisory Committee
Advisor Name Title Lai, Jih-Sheng Jason Committee Chair Meehan, Kathleen Committee Member Yu, Wensong Committee Member Keywords
- Long lifetime LED driver
- Power Factor Correction
- Light emitting diode
- Electrolytic capacitor
- Interleaved converter
Date of Defense 2012-07-02 Availability unrestricted AbstractThis thesis presents an investigation into the characteristics of and driving methods for light emitting diode (LED) lamp system. A comprehensive overview on the lighting development is proposed. The characteristic of the light emitting diode (LED) lamp is described and the requirements of the ballast for the light emitting diode (LED) lamp are presented.
Although LED lamps have longer lifetime than fluorescent lamps, the short lifetime limitation of LED driver imposed by electrolytic capacitor has to be resolved. Therefore, an LED driver without electrolytic capacitor in the whole power conversion process is preferred. In this thesis, a single phase, power factor correction converter without electrolytic capacitors for LED lighting applications is proposed, which is a modified SEPIC converter working in discontinuous conduction mode (DCM). Different with a conventional SEPIC converter, the middle capacitor is replaced with a valley-fill circuit. The valley-fill circuit could reduce the voltage stress of output diode and middle capacitor under the same power factor condition, thus achieving higher efficiency. Instead of using an electrolytic capacitor for the filter, a polyester capacitor of better lifetime expectancy is used.
An interleaved power factor correction SEPIC with valley fill circuit is proposed to further increase the efficiency and to reduce the input and output filter size and cost. The interleaved converter shows the features such as ripple cancellation, good thermal distribution and scalability.
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