| LLC resonant converter is widely used in many applications because it has many merits overother power converters. It can realize zero-voltage switching for primary side switches andzero-current switching for secondary side rectifiers in a wide load range. Due to the soft switching, itis convenient to reduce switching loss and increase switching frequency for high efficiency, highpower density and low EMI. This paper is dedicated to research on a400V/12V100A dc/dc converterbased on LLC resonant converter.In this thesis, the operation principle and the features of full bridge LLC resonant converter arediscussed in details. It is found that not only the primary side switches can realize zero-voltageswitching(ZVS), but also the secondary side rectifiers can achieve zero-current switching(ZCS) whenthe switching frequency is not higher than the resonant frequency. Apart from this, the output voltageis independent with the load if LLC resonant converter operates at the resonant frequency. And at thisoperating point, the highest efficiency can be reached. Besides, the principles, implementation ofvoltage mode and average current mode are both presented.Because of the low output voltage and high output current, in order to reduce the loss of therectifier and improve the efficiency further, the synchronous rectification(SR) technology is applied.The principle of SR technology based on the smart IC UCC24610is introduced.Besides, in order to increase the power stage of the converter, this paper presents fourmulti-module parallel schemes. By the method of contrast analysis on load sharing, it is found thattransformed-series-linked LLC resonant converter has good performance on load sharing. In order toverify proposed design consideration, a400V/12V100A prototype has been fabricated and tested inthe laboratory. The experimental results show that the full bridge LLC resonant converter can realizeZVS for the primary switches and ZCS for the rectifier diode. The smart synchronous rectifier IC canprovide accurate drive signal. And the application of synchronous rectifier can improve the efficiencythan diode rectifier. The selected transformed-series-linked LLC resonant converter has a nice outputcurrent sharing performance. |
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