基于TCM控制的多相交错并联Buck/Boost软开关变换器的变频范围优化方法

A Frequency Variation Range Reduction Method for Multi-phase Parallel Interleaved Buck/Boost ZVS Converter Under TCM Control

多相交错并联Buck/Boost变换器采用三角电流模式控制实现软开关时,存在随负载变化开关频率变化范围过宽的问题。文中提出一种并联桥臂的退出机制,在不同负载下实时动态增减并联桥臂的运行数目,可以有效解决开关频率变化范围过宽带来的驱动电路和滤波器设计复杂、高频时关断损耗高以及PWM控制精度低等问题。文中基于不同桥臂数目下开关频率的变化曲线和损耗模型确定切换电流点以及桥臂数目的分配方案。为避免开关器件承受不均匀的热应力,进一步基于温度参量提出桥臂的投切顺序和轻载时桥臂交替运行的方案。通过搭建一台6相交错并联12kW实验样机对该方法进行验证,仿真和实验结果都表明了所提优化方法的有效性。

Triangle current mode(TCM)control has been proposed for multi-phase parallel interleaved Buck/Boost converter to achieve zero voltage switching(ZVS).However,the switching frequency variation range will become too wide with the change of load.It not only increases the design complexity of the filter and the driving circuit,but also reduces the conversion efficiency and the accuracy of the PWM control,especially at high frequencies.In order to solve these problems,a phase-shedding mechanism for multi-phase Buck/Boost converter was proposed.The number of the operating phase-legs was dynamically adjusted with the load percent,leading to lower switching frequency and higher efficiency at light load.The switching current points were determined based on the variation curves of the switching frequency and loss model.A phase-leg alternative operating method based on the device temperature was further proposed to guarantee even thermal stresses among all the phase-legs.The simulation and experimental results from a 6-phase parallel interleaved 12k W experimental prototype were illustrated to verify the effectiveness of the proposed optimization method.