一种高功率因数低母线电压单级LLC AC/DC变换器

Single-stage LLC AC/DC Converter with High Power Factor and Low Bus Voltage

传统单级Boost型LLC谐振AC/DC变换器因具有转换级数少、功率因数高和软开关等优点而受到广泛研究,但同时它存在直流母线电压太高以及开关器件应力太大等缺点,一般应用于110 V以下的电网中。为克服该问题,提出了一种适用于220 V电网的新型Buck-Boost LLC谐振AC/DC变换器。该变换器除了具有传统结构的特点外,还具备输入电压较高时母线电压不高的优点,采用脉冲频率调制PFM(pulse frequency modulation)方式进行控制。分析了变换器的工作过程,阐述了功率因数校正和软开关的实现机理,给出了变换器主电路关键参数设计方法。最后,搭建了一台170 V~230 V输入、48 V/100 W输出的实验样机,实验结果验证了变换器理论分析的正确性以及该拓扑结构的电网适用性。

The traditional single-stage Boost LLC resonant AC/DC converter has been widely concerned because of its advantages such as less conversion stages,a high power factor and soft switching.However,due to its disadvantages such as a high DC bus voltage and a large stress in switching devices,it is generally applied in power grids with voltage below 110 V.To overcome this problem,a novel type of Buck-Boost LLC resonant AC/DC converter for 220 V power grid is proposed,which not only has the characteristics of traditional structures,but also has the advantage of adjustable bus voltage in the case of a high input voltage.The working process of the converter controlled by pulse frequency modulation(PFM)is analyzed,the realization mechanism of power factor correction and soft switching are elaborated upon,and a design method for the key parameters of its main circuit is also given.Finally,an experimental prototype with 170-230 V input and 48 V/100 W output was built,and experimental results verified the theoretical analysis and the grid applicability of the proposed topology.