全桥变换器中输出变压器偏磁的调节

阐述了全桥变换器由于两桥臂功率器件参数的不对称，引起输出变压器直流磁化，从而带来桥臂电流的不平衡和由此造成变换器性能的恶化。介绍了常用的一些解决方法，诸如变压器初级串联电容，或增加铁芯气隙以及根据检测桥臂电流不平衡用固定的脉冲宽度反向修正桥臂脉冲宽度等方法，并提出了一种新型的直流磁化控制电路，一个桥臂的脉冲宽度取决于输出调节信号，通过检测一个周期内流过两桥臂的平均电荷量为零决定另一个桥臂的脉冲宽度，实时地消除电流不对称引起的偏磁，这一方法得到了实验证实。

Regulation of Magnetic Bias in the Main Power Transformer of Full-Bridge Converter

This paper describes the direct current magnetization of a main output transformer in a full-bridse converter, due to the difference of parameters between two diagonal switches, causing the current Ansymmetry between the two diagonal switches. Three conventional approaches to decrease or eliminate the DC magnetic bias will be discussed, namely, (1)to connect transformer primary coil with a capacitor in series, (2) to increase the gap of a transformer core; (3) to correct pulse-width of switches with a fixed pulse width according to the detected imsymmetric switch current. After discussion, we pressent a novel controlling circuit of DC magnetic bias in which one diagonal switch pulse-width depends on the output regulation sawnals, the other is determined at the moment when average quantity of the charge flowing through two diagonal switches within one period equal to zero. As the result, the DC magnetic bias is eliminated in real take. This approach has been demonstrated in a prototype.