Study and Implementation of a Dimmable LED Driver with Multi-string Current Balance and Low Switch Voltage Stress

• Main Authors: Cheng-hsien Lin, 林政賢
• Other Authors: Yu-Kang Lo
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/05305942816712179259

碩士 === 國立臺灣科技大學 === 電子工程系 === 101 === This thesis studies and implements a dimmable LED Driver with multi-channel current balance and low switch voltage stress. The front stage is a single-stage flyback power factor corrector (PFC) converter which features high conversion efficiency, high power factor (PF) and simple topology. It supplies the main output current and a constant output voltage to the LED module. The post-stage is a buck converter which outputs an accurate current to the LED module and fulfills the multi-channel current balance and dimming functions. The buck converter is of a floating ground configuration which features small volume and high conversion efficiency. The proposed LED driver is composed of a flyback PFC cascaded by a floating ground buck converter, resembling a voltage source in series with a current source. At most three LED strings can be driven. Within the designed voltage range, the number of LEDs in one string can be adjusted and various types of lamps can be adopted. The proposed dimmable driver with current balance can lower the switch voltage stress. Therefore, the power loss and circuit cost can be reduced.