反激变换器次级谐振反射的研究

The Research of Resonant in Secondary Coils of Flyback Converter

阐述了反激变换器次级谐振的来源以及对开关管的影响,给出了高压输出整流二极管串联均压电容的选取原则.实验表明:次级漏感与次级电容会形成LC谐振,如果次级漏感及电容取值不合适,则次级谐振的能量会通过变压器耦合回初级,导致开关管出现负向电流及电压尖峰.次级均压电容的选择应该保证均压效果良好的情况下越小越好.

This paper describes the source of the resonant in secondary coils of flyback converter,and its effects on switches.It also gives the principle of how to choose voltage-sharing capacitors for high voltage output rectifier diode in series.It was found that an LC resonance is formed by secondary leakage inductance and secondary capacitors.If the value of secondary leakage inductance and capacitances are not suitable,the energy of secondary resonant will be coupled to the primary of transformer,which will result in a negative current and voltage spike in the switch.Under the condition of voltage-sharing,the value of voltage-sharing capacitors should be as small as possible.