三电平LLC谐振型DC/DC变换器的分析和设计

将三电平技术和LLC谐振变换器结合起来，提出三电平LLC谐振变换器。根据等效电路模型推导出该变换器输入输出电压的增益与开关频率、负载之间的关系，揭示其开路和短路特性，为该变换器的空载工作和短路保护的设计提供了理论基础。提供了该变换器两个死区时间的设计方法，从而保证了开关电压应力限制在输入电压的一半，同时满足每个开关零电压关断的实现条件。谐振参数可用推荐的方法依照变比n谐振电容Cs、谐振电感Ls、谐振电感Lm、的次序来设计。最后根据所提供的设计方法设计了一个540W样机，性能和结果满足要求，效率达94．7％。

ANALYSIS AND DESIGN OF A THREE LEVEL LLC RESONANT DC/DC CONVERTER

A three level LLC resonant converter is proposed by combining three level technique and LLC resonant technique. According to the equivalent circuit, relationships among DC gain, switching frequency and load are deduced. Its open circuit characteristic and short circuit characteristic are also disclosed to provide theory for no load operation and over current protection. The design consideration for two dead times is presented to assure that voltage stress for main switches is within half of input voltage and ZVS for each main switch is achieved. Resonant parameters can be designed in sequence of turn ratio n, resonant capacitance Cs, resonant inductance Ls, and resonant inductance Lm by the proposed method. Finally, the advantages and the presented design methods are verified by an experimental prototype of 540 W, whose performance and experimental results satisfy the requirement. The highest efficiency of the converter reaches 94.7%.