中文摘要：

提出一种副边侧LLC谐振的直流变换器拓扑。原边4个开关管采用一种桥型结构,并利用增加的一个储能电容Cc实现原边同时具有两个电流回路,达到两个变压器原边绕组并联工作而高频谐振电流均流的目的。副边采用倍压结构,利用变压器漏感、励磁电感和倍压电容构成LLC谐振来传递能量。原边开关管能实现零电压开通,且关断时的励磁电流小。副边两个二极管零电流关断,且额定电压为输出电压。分析电路各阶段的工作原理,详细推导电路与传统LLC谐振电路不一样的增益特性。设计一款40～56 V输入/360 V输出/额定负载300 W的样机,在不同输入下电路最高效率都大于95.5%。实验测试波形验证了电路的正确性及可行性。

英文摘要：

A secondary-side LLC resonant converter was proposed. On the primary side, four power switches form a bridge-type construer, and a bulk capacitor is inserted between two primary windings. Then two primary current loops always exist at the same time, and two primary windings flow the same high-frequency resonant current. A voltage-doubling circuit construct is applied on the secondary side. LLC resonance is formed by the magnetic inductance, the leakage inductance and a voltage-doubling capacitance Cc. The power switches can achieve zero-voltage turn-on and are turned off at a little magnetic current. The power diodes can achieve zero-current turn-off and their rated-voltage is equal to output voltage. The operation theory of each stage is analyzed. The conversion gain characteristic, not similar with that of the traditional LLC resonant converter, was also elaborated. A 40～56 V input/360 V output/rated power 300 W prototype was built and tested. Its peak efficiency can over 95.5% in the rated input voltage range. Experimental waveforms also verify the theory and the converter is available.