| As the efficiency and power density gradually becoming a major focus in the field of power supply, the LLC resonant converter is recognized as a feasible topology to meet this trend and has got attention in various applications. The bi-frequency control technique is one of frequency modulation techniques with fast transient response. Due to the problems of poor transient performance in LLC resonant converter with pulse frequency modulation, bi-frequency control technique for LLC resonant converter is proposed and studied in this paper.The operation principle and characteristics of LLC resonant converter are studied in this thesis. The initial value of LLC converter’s series resonant inductance current and series resonant capacitor over one period are characterized by approximate expression through time-domain analysis.According to the principle of bi-frequency control technique, the operation characteristics of bi-frequency control LLC resonant converter are researched. The steady-state characteristic and transient characteristic of bi-frequecny control LLC converter are studied. The low frequency oscillation phenomenon and parameter design principles of bi-brequency control LLC converter are analyzed in detail.With the simulation software SABER, the simulation experiment mode of bi-frequency control LLC resonant converter is built and an experimental prototype is built at the last. With the result of simulation and experiment, the resonant LLC converter of bi-frequency control and conventional pulse-frequency control are compared, and it is verified that the bi-frequency control LLC converter has better transient response character. |
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