High-Voltage Bus Converter Based On LLC Resonant Converter

Intermediate bus architecture is an important form of distributed power system. Combining thedc/dc stage of the front-end ac/dc converter with the intermediate bus converter can avoid thefunctions repetition such as galvanic isolation and voltage transformation, and reduce the stage ofpower conversion. The resulted converter is called high-voltage bus converter. LLC resonantconverter has the advantage of high effiency and high power density. This thesis is dedicated to thedevelopmeny of the high-voltage bus converter based on LLC resonant converter.This thesis analyzes the operation principle and characteristics of the LLC resonant converter,and it is found that the rectifier diode can realize zero-current-switching (ZCS) when the switchingfrequency is not higher than the resonant frequency. Besides, the output voltage of converter isindependent with the load when LLC resonant converter operates at the resonant frequency, and thehighest efficiency can be achieved. In order to further improve the efficiency, the synchronousrectification is applied to reduce the losses of the rectifier. The requirements of the drive circuit for thesynchronous rectifier are discussed, and the operating principle of the drive circuit is presented.A1kW prototype has been fabricated and tested in the lab. The experimental results show thatthe LLC resonanr converter realizes zero-voltage-switching for the power switches and ZCS for therectifier diode. The adopted synchronous rectifier drive circuit can provide quick and accurate drivesignal, and the application of synchronous rectifier instead of diode rectifier can improve theefficiency of the converter.Finally, the losses of the LLC resonant converter is analyzed and calculated, and the lossdistribution is depicted. The results show that loss of transformer and loss of rectifier diode are themain loss under light load and full load, respectively.