A High-Power-Factor Dimmable LED Driver with Zero-Voltage Switching

• Main Authors: Lin, Cheng-Wei, 林承緯
• Other Authors: Cheng, Hung-Liang
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/09798747397966585884

碩士 === 義守大學 === 電機工程學系 === 101 === This thesis proposes a novel LED driver consisting of a buck-boost converter and a buck converter. The integrated power conversion circuit adopts two power MOSFETs as the active switches. With no need to use any auxiliary reactive components, both active switches can be operated at zero-voltage switching-on (ZVS) by freewheeling the inductor currents of the converters through the intrinsic diodes of the MOSFETs. The buck-boost converter is operated at discontinuous-conduction mode (DCM) to perform the function of power-factor correction (PFC) to ensure almost unity power factor at the input line. The buck converter steps down the output voltage of the buck-boost converter and regulate the current flowing through LEDs. The detailed circuit operations and analysis are provided. A prototype of a 60-W LED driver is built and tested. Experimental results show that the switching losses can be effectively reduced by operating the active switches at ZVS. The measured power factor and circuit efficiency are as high as 0.995 and 92%, respectively, at the rated power.