组合式前端DC-DC变换器

保持时间是直流分布式电源系统中前端DC-DC变换器的一项特殊的性能指标。它要求该DC-DC变换器必须能工作在很宽的输入电压范围内，因此导致正常工作状态下的变换效率大大降低。该文提出了一种不对称半桥与后备升压单元组合的电路拓扑，特殊控制的升压单元仅在保持时间工作、保证主功率变换单元的输入电压变化范围很小因而总是工作在最佳状态，而在正常工作模式下被自然旁路。并且变换器正常，保持工作模式转换平滑。实现了整个前端变换器模块的高效率、高功率密度和足够的保持时间。详细分析了新拓扑的工作原理及其控制方法，并给出了600W样机的仿真和实验验证结果。

A COMBINED TOPOLOGY WITH BACK-UP BOOST AND ASYMMETRICAL HALF BRIDGE FOR FRONT END DC-DC CONVERTER

Holdup time is a special requirement for front-end DC-DC converter in distributed power supplies. It forces the converter to operate in a wide input voltage range, which greatly degrades the converter's normal efficiency. A novel back up boost and asymmetrical half bridge combined topology with a special control,for front-end DC-DC conversion,is proposed in the paper.The back up boost unit operates inherently only during the hold up time to ensure the input voltage for the asymmetrical half bridge,the normal power stage, within a narrow range and stands by under normal condition with no power loss.Therefore the combined converter can be designed in a very small size. And no spike is induced during operation modes switching of the converter. As a result, the overall performances of high efficiency, high power density and sufficient holdup time are obtained for the proposed converter.The Topology and operation principles are analyzed,and simulated and experimental results are given in details.