Research On LLC Resonant Converter Based On Digital Control

As distributed power system widely used in areas such as communications, computers, moreelectric aircraft, spacecraft and the international space station, LLC resonant converter graduallybecome a focus of power electronics technology. At present, most of the research on LLC resonantconverter is using the analog control. Although there is mature theory and analysis method of controlin analog control, but there are some inherent disadvantages, such as circuit complexity, low reliability,flexibility of poor. Compared with analog control, digital control can eliminate the instability causedby discrete components and electromagnetic interference.It has short design cycle, high controlprecision and flexibility. Hence, it is very necessary to have a study on digital control of the LLCresonant converter.This thesis first introduces the traditional resonant converter classification and working principle,and compares the advantages and disadvantages of three kinds of resonant converter.Then weintroduces LLC resonant converter on this basis. This paper analysis LLC resonant converter worksand operation performance in time domain and frequency domain respectively. Establish equivalentcircuit model of the LLC using of FHA model. This aricle analysis gain characteristics and the criticalparameters on the performance of LLC resonant converter. The process of parameters and circuitdesign is given according to a specific design requirement. In addition, the small-signal model isestablished based on the equivalent circuit. This paper combines digital control and soft-switchingtechnology to research digital control of LLC resonant converter, using TI’s TMS28027DSP chip tocomplete power control, and using of digital PI algorithm for steady-state regulation system.Finally, a150W LLC resonant converter prototype is built up, simulation and experimentalresults are presented to verify the correctness and effectiveness of theoretical analysis. The prototypehas the following advantages: full range of soft switching can be realizedinherently.Thus highefficient is achieved, and with the step-up characteristic. It can easily meet the wide input voltagerequirement for DC-DC converter in the distributed power systems.