基于图腾柱无桥PFC的软开关控制变换研究

Soft switch control transformation based on totem pole bridgeless PFC

随着数据中心所需能量的日益增长,对于变换器高性能指标的追求十分迫切。文中设计了基于图腾柱结构实现高效高功率密度的软开关功率因数校正(PFC)电路,采用无桥PFC拓扑结合第三代宽禁带氮化镓器件,通过全数字控制方法实现电路在电流临界和准方波2种状态下切换工作,保证变换器在具备PFC功能的同时实现开关管零电压开关(ZVS)。首先介绍了图腾柱无桥PFC基本电路结构,通过分析电路暂态过程得出实现软开关特性的条件;然后根据全数字双闭环控制方法实现系统PFC功能,结合数学仿真模拟不同状态下图腾柱PFC输出特性;最终搭建了1台输入有效值220 V,输出48 V/400 W的AC/DC变换器。结果表明,系统在实现PFC功能的同时,可在全输入电压范围内保持ZVS特性,验证了电路设计及控制策略的可行性。

With the increasing energy required by data center,a soft switch power factor correction(PFC)circuit based on totem pole structure is designed to meet the urgent need of high performance index of converter.A soft-switching PFC circuit based on the totem pole structure that can achieve high efficiency and high power density is proposed.The bridgeless PFC topology is combined with the third-generation wide bandgap GaN device,and it is realized through a fully digital control method.The circuit is switched to work in two states of critical current and quasi-square wave to ensure that the converter has the power factor correction function and realizes zero voltage switch(ZVS).The basic circuit structure of the totem pole bridgeless PFC is first introduced.The conditions for realizing the soft switching characteristics are obtained through the analysis of the circuit transient process.Then the system power factor correction function is realized according to the all-digital double closed-loop control method,combined with mathematical simulation to analyze different states totem pole PFC output characteristics.Finally,an AC/DC converter with 220 V input and 48 V/400 W output is built.The results show that while the PFC function is implemented,it can maintain ZVS characteristics in the full input voltage range,verifying the feasibility of the circuit design and control strategy.