Study On Cross Regulation In Flyback Converters

In the market of power switch, converters under 400W take up most of the share. Because of the lowcost of flyback converters and appliable for wide voltage, the topoloqical structure is very popular now, a lot of single-output and multiple-output converters are widely used in charge, STB, notebook power adapters and so on.The workstyle of flyback output has great influence on cross regulation of multiple-output. This limited the apply of flyback converters in multiple-output switch supplies, especially in apply of flyback converters with different groups of changeable load current, cross regulation become a big problem, it is difficult to ensure the uncontrollable output voltage precision. We have to add linear voltage regulators or a three terminal regulators to uncontrollable groups in some applications with high precision, on one hand it increases the cost, on the other hand it reduced the overall efficiency of converters for separate circuits have certain voltage drop. Sometimes we also have to add radiators which amplify the volume of converters because of heavy output current and heavy loss.This thesis introduced the operating principle, dynamic procedure, transitivity of electromagnetic energy and control method of flyback converters. It emphasized on main output control method. It derived some parameters about the cross regulation by analysing the reasons of cross regulation in the event that it is continue current mode(CCM) and discontinue current mode(DCM). On the basis of theoretical analysis, it determined separate parameter effect on cross regulation. Meanwhile, it analysised and experimented on arrangement of windding, considered some element to research, such as the extent of continues working, reflected voltage and so on. It made the load could increase to a certain extend, and the flyback converters would expand more applications.