Abstract：The LLC resonant converter can realize zero-voltage-switching for the switches and zero-current-switching for the rectifier diodes over the full load range, thus a high efficiency is achieved. The output voltage is independent of the load when LLC resonant converter operates at the resonant frequency. Based on this characteristic, this paper proposes a self-oscillating drive circuit for LLC resonant converter. The driving signals of the switches are obtained by the current transformer parallel with a inductor, which is used to sense the resonant inductor current, and the driving circuit is improved to speed up switching. For restraining the current overshoot during the start up period, an improved LLC resonant converter topology is used. The self-oscillating LLC resonant converter has the advantages of reduced cost and size compared with the converter with specific control chip, and it is suitable for the applications where the regulation of the output voltage is not strictly required.
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2011, Vol. 26 
