基于电流纹波率反激式变压器导通模式的分析

Analysis on Conduction Mode of Flyback Transformer Based on Current Ripple Ratio

提出了利用电流纹波率设计反激式变压器和判别其导通模式的方法,用该方法导出了反激式变压器从CCM进入DCM模式的数学式,用MATLAB计算并分析了输入电压、负载电流及反射电压对导通模式的影响。计算表明,最小电流纹波率或反射电压取值越大,反激变压器在输入电压增大或负载电流减小时越容易进入DCM模式。设计了一款24 V 1.5 A反激式开关稳压电源,测量了变压器的电流波形。实验表明,测量结果与推导的数学式相符,用电流纹波率设计反激式变压器比传统的波形系数更直观和便于测量。

A method to design a flyback transformer and distinguish its conduction modes is proposed based on the current ripple ratio. An equation for the flyback transformer going into the discontinuous conduction mode from the initial continuous conduction mode is derived by using this method. According to the equation,the calculation is performed by MATLAB,and the effects of the input voltage,load current or reflected secondary voltage on the con-duction mode of the flyback transformer are analyzed. The calculation indicates the greater the minimum current ripple ratio or reflection voltage is,the more easily the flyback transformer goes into the discontinuous conduction mode when the input voltage increases or load current decreases. Then,a 24 V 1.5 A flyback switching power supply is designed,and the current waveforms of the flyback transformer are measured. The experiment shows that the measured results are agreement with the derived equation,and the current ripple ratio is more intuitive and easier to be measured than the current wave factor.