LLC谐振变换器典型分析方法对比

Comparative study of typical analysis methods for the LLC resonant converter

LLC谐振变换器可以在高频运行的同时实现软开关,对于提高开关电源的功率密度和效率意义重大。基波近似法和运行模态分析法是现阶段研究LLC谐振变换器的2种经典方法,但目前缺乏针对二者在电压增益精确性、效率、应用场合等方面的研究。该文首先分析这2种方法的原理;然后,在PSIM环境下对LLC谐振变换器工作模态进行仿真分析;基于LLC运行模态,在仿真电路中对比2种方法下的电压增益精确性;最后,基于峰值电压增益选择谐振参数,搭建1.5 kW/28 V输出等级的实验样机。实验结果表明,在下谐振区,基波近似法的电压增益比实际低10%~15%,而运行模态分析法迭代出的电压增益在全频率范围内与实际增益具有高度一致性,且基于运行模态分析法得到的谐振参数应用于样机时具有更高的效率。

The LLC resonant converter can achieve soft-switching while it operates in high-frequency and then improves the power density and efficiency of power supply.The fundamental approximation and mode analysis are two classic analysis methods of LLC resonant converter,but the comparative studies in the voltage gain accuracy,efficiency and application is not intensively discussed.On this background,the principle of the above methods is illustrated firstly.Then,the operation mode of LLC resonant converter is analyzed in PSIM simulation environment.Based on the operation modes,the voltage gain accuracy of the two methods is compared in simulation.Finally,the resonant parameters are selected based on the peak voltage gain,and a 1.5 kW/28 V prototype is set up.The experimental results show that actual gain is higher than the gain curve based on FHA 10%to 15%below the resonant zone,and have high accordance with the voltage gain based on the mode analysis in whole frequency range.And the iterative parameters based on mode analysis have higher efficiency with the experimental prototype.