一种单级全桥PFC变换器变压器偏磁抑制策略

Bias-magnetic suppression strategy for single-stage full-bridge PFC converter

单相单级全桥PFC变换器变压器双向励磁,具有功率密度高和电气隔离等特点,适用于中大功率场合,但该变换器由于其工作方式的特殊性,存在特有的变压器偏磁现象。通过对单级全桥PFC变换器的工作原理与变压器偏磁产生机理进行分析,得出每1/4工频周期内磁化曲线中心点偏移情况,并递推得到偏移量的最大值。在此基础上,提出一种正负半周对称的数字抑制策略,通过设计开关管的时序,使每个开关周期内变压器正负向励磁时间相等,进而消除了变压器偏磁;与传统偏磁抑制方式相比,该策略不增加电路的复杂程度与系统的体积、重量,实现较为容易。最后,通过搭建额定输出电压/电流为48V/12A的样机验证了所提出的偏磁抑制策略的可行性。

Single-phase single-stage full-bridge PFC converter transformer bi-directional excitation,with high power density and electrical isolation characteristics,is suitable for medium and high power applications. However,due to the particularity of its working mode,the converter has its own transformer bias phenomenon. Through the analysis of the working principle of single-stage full-bridge PFC converter and the generation mechanism of transformer magnetic bias,the central point offset of the magnetization curve was obtained in every quarter of the power frequency cycle,and the maximum value of the offset was obtained recursively. On this basis,a digital suppression strategy with positive and negative half-cycle symmetry was proposed,which makes the positive and negative excitation time of transformer equal in each switching period,then eliminates the transformer bias. Compared with the traditional suppression method,the strategy does not increase the complexity of the circuit and the volume and weight of the system,and the realization method is easier. Finally,a prototype with rated output voltage and output current of48 V/12 A was built to verify the feasibility of the proposed strategy.