Design and Implementation of a High Efficiency Flyback LED Driver with Dimming Functions

• Main Authors: You-Ping Tsai, 蔡右平
• Other Authors: Ming-Tse Kuo
• Format: Others
• Language: zh-TW
• Published: 2016
• Online Access: http://ndltd.ncl.edu.tw/handle/76fa32

碩士 === 國立臺灣科技大學 === 電機工程系 === 104 === In terms of the conventional LED drivers, the two-stage circuit is commonly used to achieve functions of power factor correction. However, due to the requirement of an additional converter and feedback control loop respectively, it resulted in low efficiency, high space volume, and extra costs for the system. The purpose of this thesis is to improve the problems by implementing a single-stage flyback LED driver. This thesis is based on theoretical analysis to derive the transfer function of the proposed circuit, and providing the step-by-step procedure for parameter designing as to build realistic power IC module system with utilization of SIMetrix/SIMPLIS software. By analyzing the outcome of simulation, it positively reduced the time for designing and optimizing the circuit performance. The circuit corrected power factor by using boundary conduction voltage-mode control method, which has soft-switching characteristic minimizing the losses of MOSFET. Furthermore, the system owns the output feedback control with Constant Voltage-Constant Current(CV-CC) circuit, and the Pulse Width Modulation(PWM) dimming function, which are both able to increase reliability and adjustability for the system. In conclusion, a T8-LED 16.8W prototype circuit of single-stage flyback LED driver was designed to verify the theory for proving the feasibility of system. The experimental results showed that the system efficiency is up to 88.51%, the highest power factor reached 99.67%, and the output dimming range varies from 6.5% light load to 100% full load condition. Accordingly, the system performance entirely satisfied the new type of Energy-Star regulations. Besides, in comparison with the existing literature, this thesis achieves the higher power factor than the existing one about 1.32% and 1.76% respectively. It proved that the system has not only higher power factor correction ability but also has the characteristics of high-speed dynamic response and high precision for output loads.