Study And Design About A Current Driven Synchronous Rectifier For LLC Converter

With the development and application of power electronics , power technology is becoming mature, and showing the characteristics of small, high-frequency, high power density and low noise. Meanwhile, resources economizing with high efficiency has become the world's theme and hot spot in the field of power development. Due to the unique structure, LLC resonant converter is able to achieve soft-switching and take full advantage of the transformer's magnetizing inductance and leakage inductance. Just with these advantages, it effectively reduces the switching losses and is easy to implement magnetic integration. Synchronous rectification technology is also a hot topic in the field of power, because it can effectively improve the power efficiency and reduce losses in the occasion with low voltage and high current output.This article firstly provides an overview on the development of LLC resonant converter and synchronous rectification technology, and analyzes LLC resonant converter's working principle and the state in the case of f_r2< f_s< f_r1.Then based on FHA AC equivalent circuit, I analyze the impact of the main circuit components'parameter on the convert, and put forward the design method and procedure of LLC resonant converter. At last, taking the case of output 100W 10V, I calculate the corresponding parameter values, which lay foundation for further study.After introducing the development and classification of synchronous rectification technology, this report focuses on the current-driven program's development and its working principle.On the basis of the original drive, for low-voltage and high-current applications, it is proposed and detailedly analysed to three different characteristics of new current drive. And it is offered to the design of important parameters. Simulations are eventually performed. The result shows that the efficiency is increased compared to traditional converters.Finally, based on UCC25600, I make experiments on new current drive program one, which prove that the design is reasonable.