三电平CLLLC谐振变换器的变频移相混合控制策略

PFM+PSM hybrid control strategy of three level CLLLC resonant converter

三电平CLLLC谐振变换器因功率开关管承受电压应力低、功率密度大、软开关范围广的特点而闻名,但同时也存在启动电流过大、可调输出电压范围窄等问题。本文以正反向结构完全对称的三电平CLLLC谐振变换器为研究对象,详细分析了该拓扑结构的工作原理及其增益特性;在此基础上研究三电平CLLLC谐振变换器的软启动控制策略和变频控制(pulse-frequency modulation,PFM)升压、变频移相混合控制(pulse-frequency modulation+phase-shift modulation,PFM+PSM)降压的混合控制策略;最后通过Matlab/Simulink仿真验证本文所研究控制策略的有效性。仿真结果表明:本文研究的软启动控制能有效抑制启动阶段的电流过冲,变频加移相的混合控制策略能保证在宽输出电压范围的条件下满足开关管软开关特性,并且在模式切换和负载切换下都拥有较好的动态性能。

The three level CLLLC resonant converter has the characteristics of low voltage stress of the power switch pipe,high power density and wide soft switching range,but it also has problems such as excessive starting current and narrow adjustable output voltage range.This paper takes a three level CLLLC resonant converter with a completely symmetrical positive and reverse structures as the research object,and analyzes the working principle and gain characteristics of the topology in detail.On this basis,the soft start control strategy and the pulse-frequency modulation(PFM)boost,hybrid control strategy for pulse-frequency modulation+phase-shift modulation(PFM+PSM)buck are studied.Finally,the effectiveness of the control strategy investigated in this paper is verified by Matlab/Simulink emulation.The results show that the soft start control studied in this paper can effectively suppress the current overshoot during the start-up phase.The hybrid control strategy of pulse-frequency and phase shift can ensure that the soft switching characteristics of the switch tube are met under the wide output voltage conditions,and that it has good dynamic performance under both mode switching and load switching.