基于有效占空比的ZVZCS全桥变换器建模与仿真

摘要

The principle of zero-voltage zero-current switching (ZVZCS)full-bridge PWM converter is analyzed. By introducing the effective duty cycle of the transformer's secondary side voltage ,considering the parasitic parameters of the circuit elements, and basing on the switching equivalent model of Buck PWM converter, the small-signal equivalent model of ZVZCS full-bridge converter is established. This method can be used in any full-bridge converter of which the effective duty cycle can be calculated. The small-signal transfer function's amplitude-frequency and phase-frequency as well as the step function in the open-loop are analyzed. The results not only prove that the method has definite physical meaning, simple calculation and high precision, but also reveal that the ZVZCS full-bridge soft-switching converter has a higher stability comparing with conventional Buck converter.%分析了零电压-零电流开关(ZVZCS)全桥脉宽调制(PWM)变换器的工作原理,引入变压器副边电压有效占空比的概念并考虑电路元件的寄生参数,在Buck变换器的PWM开关等效模型的基础上,建立了ZVZCS全桥软开关变换器的小信号等效模型,该方法通用于任何可以计算出有效占空比的全桥变换器.通过对小信号传递函数的幅频和相频特性以及开环情况下的阶跃函数的仿真分析,证明了该方法具有物理意义明确、计算简单、精确度高等特点,也揭示了ZVZCS全桥软开关变换器相对于常规Buck变换器具有更高的稳定性.