半桥三电平LLC谐振变换器的调制方法

Modulation methods of half-bridge three-level LLC resonant converters

为了得到适合高输入电压、宽增益范围应用的优选拓扑,从混合调制方法的角度对4种常见的半桥三电平LLC拓扑进行分析和对比.混合调制策略可以在不改变谐振腔参数、不增加额外元器件的前提下,使LLC谐振变换器的增益范围加倍.使用穷举法分析各三电平结构所有可能的具有零电压开关特性的调制方法,按照调制自由度和直流增益的不同分为高增益频率调制、低增益频率调制和脉冲宽度调制3大类.对比从元件的数量与应力、自动均压能力和对调制方法的兼容性3个方面进行展开,结果表明,桥臂串联型全桥拓扑具有最优的综合性能.实验结果验证理论分析的正确性.

Four half-bridge three-level LLC topologies were analyzed and compared from the perspective of hybrid modulation method in order to obtain an optimal topology which is suit for high input voltage and wide dc gain range application.The hybrid modulation strategy can double the dc gain range of the LLC resonant converter,without altering the resonant tank parameters or adding any extra component.All possible zero-voltage switching（ZVS）modulation methods of each topology were analyzed by the exhaustive method.These modulation methods can be divided into three categories,according to the modulation degree of freedom and dc gain：high gain frequency modulation（HGFM）,low gain frequency modulation（LGFM）and pulse-width modulation（PWM）.Comparison was conducted from three aspects：the number and electrical stress of components,automatic voltage-sharing capability,and compatibility with different modulation methods.The leg-series full-bridge topology has the best overall preformance.The experimental results verified the correctness of the theoretical analysis.