一种基于Burst-PWM混合控制的LLC谐振变换器宽电压范围输出策略  

A Burst-PWM Hybrid Control Method for Wide Output Voltage Range of LLC Converter

作　　者：石林[1] 刘邦银[1] 段善旭[1] Shi Lin;Liu Bangyin;Duan Shanxu(State Key Laboratory of Advanced Electromagnetic Engineering and Technology School of Electrical and Electronic Engineering Huazhong University of Science and Technology,Wuhan 430074 China)

机构地区：[1]强电磁工程与新技术国家重点实验室(华中科技大学电气与电子工程学院)

出　　处：《电工技术学报》2019年第22期4772-4780,共9页Transactions of China Electrotechnical Society

基　　金：国家重点研发计划(2018YFB0106300);国家自然科学基金(51777084)资助项目

摘　　要：LLC谐振变换器一般采用脉冲频率调节(PFM)方式控制输出电压,因此在最大开关频率受限的情况下输出电压范围同样会受到限制。该文提出一种基于突发控制-变占空比控制(Burst-PWM)的混合控制模式以实现LLC变换器的宽电压范围输出。首先分析Burst控制与PWM控制应用在LLC变换器中的特性及其不足之处。采用Burst-PWM混合控制时,PWM控制能够减小Burst开通(Burst-on)时段内谐振腔电流峰值,而Burst控制能够在Burst-on时段内为PWM控制下的开关管提供足够的零电压开通(ZVS)电流。这种方式能够保证变换器在宽电压范围内的特性和稳定性。然后采用状态空间轨迹法给出了谐振腔参数优化设计方法以及确定PWM控制下的最小占空比。最终实验证明了分析的正确性以及所述方法的有效性。PFM control is generally used in conventional LLC converter whose output voltage range is restricted by the limited operating frequency. A Burst-PWM hybrid control method is proposed to expand the output voltage range of the LLC converter. The characteristics and disadvantages of PWM control and Burst-mode control are firstly analyzed. When the hybrid control method is used, PWM control can reduce the resonant current and Burst-mode control can produce enough resonant current for soft switching. Then ZVS for all switches and low resonant current during burst-on time are realized over a wide range of output voltage. The stability and output performance of the converter are improved as well. The optimized design of the resonant parameters and the minimum PWM duty cycle are also analyzed based on state-plane trajectory. The experimental results verify the effectiveness and feasibility of the proposed method.

关 键 词：LLC谐振变换器 Burst控制 PWM控制 混合控制 

分 类 号：TM46[电气工程—电器]