三电平变压器中漏感对二极管换流影响

The Affection of Leakage Inductor of Three-level Transformer on Diode Free-wheeling

针对高频隔离直流变换器初级环流阶段的次级二极管工作状态问题,分析了此工作阶段的等效电路,推导了次级二极管换流条件,指出变压器漏感是决定二极管换流与否的一个关键因素。得到了两种工作模式下各电流变化解析公式,然后分析了两种模式对各工作器件的影响。最后通过实验证明了变压器漏感大的电路在初级环流阶段不会发生二极管换流,反之则会发生二极管换流。

Aiming at the diodes status problem during current-circulating phase in high-frequency isolated converter, the equivalent circuit is proposed and analyzed.The free-wheeling condition of the secondary diodes is derived and it is indicated that the leakage inductor is a key factor.The mathematic equations of each current are derived also.Then the effects on each power components in two operation modes are analyzed.Finally,the experiments verify that there are no diode free-wheeling phenomena when the leakage inductance of transformer is larger, or else there will exist diode free-wheeling.