非理想正激变换器的负载瞬态建模与分析

Load-transient Modeling and Analysis of the Non-ideal Forward Converter

负载瞬态响应是DC/DC变换器设计中的重要指标,通常在基于理想模型的计算中难以准确预估,从而导致调试时发生器件过压损坏。在考虑了主要寄生参数后,对峰值电流模式正激(PCMF)变换器的功率级进行非理想建模。根据非理想小信号模型推导出了控制-输出传递函数与输出阻抗的非理想表达式。然后给出了负载瞬态下过冲电压与恢复时间的表达式,并根据100 W/15 V原理样机的电参数进行了瞬态参数计算。对原理样机进行波形测试,得到穿越频率、相位裕度、过冲电压、恢复时间等参数,与计算值吻合较好,证明了该模型的精确性与推导的正确性。

Load-transient response is important index in DC/DC converter design.It is difficult to accurately calculate based on the ideal model,resulting in overvoltage of components during the circuit experiments.The power stage of a nonideal,peak current mode controlled forward(PCMF)converter is modeled when considering parasitic parameters.According to the non-ideal small-signal model,the non-ideal control-to-output transfer functions and output impedance are derived.The load-transient expressions of output voltage,overshoot voltage,and recovery time are given,then the load-transient parameters of a 100 W/15 V prototype are calculated and measured.The experimental results show that the waveforms are in good agreement with the calculated values,including crossing frequency,phase margin,overshoot voltage,recovery time,etc.It proves the accuracy of the model and the correctness of derivation.