适合大电流输入高压输出的软开关直流变换器

首先,提出了一种LLC谐振的软开关直流变换器,其中原边包含4个开关管、2个变压器绕组和1个耦合电容,并利用耦合电容构造了2个变压器绕组同时工作的回路,实现了两者的均流;副边包含2个二极管和2个谐振电容,构成了一个谐振式倍压电路;然后,利用变压器漏感、励磁电感和谐振电容产生LLC谐振来传递能量,各开关管能实现零电流开通,二极管零电流关断,且承受的反向电压为输出电压,关断损耗也很小;最后,分析了电路各阶段的工作原理,推导了电压增益特性,并设计了一款22~28 V输入、360 V输出、额定负载800 W的样机。实验测试结果证明,电路最高效率达到93.5%,同时也证明了电路的有效性。

A Soft-switching Converter for High-current Input and High-voltage Output Field

A LLC resonant converter soft-switching was proposed. On the primary side, there are four power switches, two primary windings and one coupled-capacitor. Two primary windings can operate commonly and realize current-sharing by the coupled capacitor. On the secondary side, a voltage-doubling construct consists of two diodes and two resonant capacitors. This converter transfer energy by LLC resonance formed by the magnetizing inductance, leakage inductor and resonant capacitor. There exist two current loops respectively both on the primary side and on the secondary side during LLC resonance process. All power switches can realize zero-current switching-on and have an negligible turn-off losses. Two power diodes can realize zero-current switching-off, and their rated voltage is equal to the output voltage. The operation theory of each stage is analyzed. The DC voltage gain characteristic is elaborated. A 22V~28V input/360V output/rated power 800W prototype was built and tested. Its peak efficiency can over 93.5%. Experimental waveforms also verify the converter available.