Analysis And Design Of A Single Stage APFC Full Bridge Converter With Stable Bus Voltage

In the kW power level applications, single stage APFC full bridge converter has attracted a lot of attentions and concerns due to its characteristics of simple structure, high power factor and high efficiency. However, this kind of converter can have the problem of bus voltage surge easily under light load working condition, this makes the converter difficult to meet the demand of stable operation in the wide load range when charging an electric vehicle. Thus, the research on the problem of bus voltage surge under light load condition of the single stage APFC full bridge converter is of great significance to the expansion of its application range.In this thesis, a single stage APFC full bridge converter with stable bus voltage is designed, and three part of works are completed in this thesis. Firstly, the structure features and operating principle of the single stage APFC full bridge converter arc analyzed, and the mechanism of the problem of bus voltage surge under light load condition are found. Secondly, based on the asymmetric phase shift driving method and the pseudo continuous conduction mode (PCCM) based control method, a single stage APFC full bridge converter with stable bus voltage is designed. Finally, a 1kW prototype of the single stage APFC full bridge converter with stable bus voltage is made by software and hardware design. The innovation of this thesis is reflected in breaking the minimum duty ratio limit caused by traditional drive method by using asymmetric phase shift driving method, and achieving flexible control of the input power of the converter by using pseudo continuous conduction mode based control method.Based on the 1 kW prototype of the converter, the analysis and design of this thesis is tested. The test results show that, the converter works with the frequency of 50kHz, and has an output voltage range of 45Vdc to 70Vdc, achieves a PF value higher than 0.97 and the overall efficiency higher than 88.4%. Besides, the bus voltage of the prototype converter just increases 15V gradually, instead of increases 40V dramatically, when changing working condition from full load to light load(200W), which can ensure the stable operation of the converter.