反激变压器漏感和分布电容的影响分析

针对反激变压器工作在高频情况下寄生参数不可忽略的事实,详细分析了变压器漏感和分布电容给反激变换器带来的影响。首先,分析了理想变压器情况下电流断续模式反激变换器的工作过程;其次,分析了理想变压器中只加入漏感、只加入分布电容、同时加入漏感和分布电容3种情况下寄生参数对反激变换器工作过程的影响;最后,设计了一台反激变换器实验样机对寄生参数的影响进行了验证。实验结果表明,漏感会在开关管关断瞬间的漏源电压上产生一个电压尖峰,分布电容会在开关管开通瞬间的漏极电流上产生一个电流尖峰,同时开关管截止期间漏感和分布电容之间以及励磁电感和分布电容之间产生的谐振会在开关管的漏源电压上叠加相应的振荡。

Analysis of the influence of leakage inductance and stray capacitance of flyback transformer

In view of the fact that parasitic parameters of flyback transformer can not be neglected in high frequency, the influence of transformer leakage inductance and stray capacitance to flyback converter is analyzed in detail. Firstly, the working process of flyback converter using ideal transformer is analyzed in DCM. Secondly, the influence of parasitic parameters to flyback converter is analyzed when leakage inductance and stray capacitance are added in ideal transformer. Finally, a flyback converter prototype is designed to verify the influence of parasitic parameters. The experimental results show that the leakage inductance will produce a voltage spike on the Drain-Source voltage at the moment of turn off, the stray capacitance will produce a current spike on the drain current at the moment of turn on. Meanwhile, the corresponding oscillation is superimposed on the Drain-Source voltage of the switch, resulted by the resonance between the leakage inductance and the stray capacitance as well as between the excitation inductance and the stray capacitance during the turn-off period of the switch.