CCVM-DCVM边界模式定频LCC谐振变换器设计

Design of Fixed Frequency LCC Resonant Converter Operating in CCVM-DCVM Boundary Mode

定频LCC谐振变换器具有传统变频LCC谐振变换器软开关工作、EMI干扰小等优点,显著降低了磁性元件与EMI滤波器的设计难度。但定频LCC谐振变换器存在软开关条件丢失、谐振元件与开关元件电压电流应力大等问题。此外,对于定频LCC谐振变换器,目前还缺乏较好的参数设计方法。针对以上问题,通过定频LCC谐振变换器的功率分析,提出了一种工作于CCVM-DCVM边界模式的定频LCC谐振变换器参数设计方法。该方法在保证变换器软开关工作条件的同时,有效降低了定频LCC谐振变换器中谐振元件与开关元件的电压电流应力。分析了定频LCC谐振变换器工作模态,采用基波近似法建立了LCC谐振变换器等效电路模型,得到了LCC谐振变换器的软开关实现条件。在此基础上,通过变换器的功率分析,得到了变换器元件参数与谐振元件功率的关系,给出了工作于CCVM-DCVM边界模式的定频LCC谐振变换器参数设计过程。最后,通过仿真与实验验证了理论分析与参数设计方案的有效性。

While inherit many advantages from traditional LCC resonant converter, fixed frequency LCC resonant converter greatly reduces its design difficulty of magnetic elements and simplifies design procedure of EMI filter. However, adapting improper parameters in such implementation leads to serious problems such as high voltage/current stress and/or the loss of soft switching operation. So far, an appropriate parameter design procedure is still demanded for fixed frequency LCC resonant converter. Based on the power analysis of fixed frequency LCC resonant converter, this paper proposed a parameter design procedure which makes the converter operate under CCVM-DCVM boundary mode, limiting the voltage and current stress of the converter while maintaining the soft switching condition under rated working operation. And by adapting the fundamental harmonic approximation the system is equivalent to a linear circuit. Through the linear circuit, the soft switching condition is derived. Furthermore, power analysis is given to unveil the relationship between the power of elements and element parameters, based on which a clear parameter design procedure is derived. The time domain simulation and experimental results show the validity of the theory and parameter design procedure in this paper.