The traditional single-stage boost LLC resonant AC/DC converter has been widely studied due to advantages such as few power stages, high power factor, and soft switching. However, it also has several disadvantages, such as a low and narrow input voltage, a DC bus voltage that is much higher than the input voltage, and high stress of the switching devices. Therefore, it is generally used in power grids under 110 V. In order to overcome the above problems, this paper proposed a buck-boost LLC resonant AC/DC converter for both 110 V and 220 V power grids. In addition to its traditional structure, the proposed converter has the advantages of a wide input voltage range and a low bus voltage. The proposed converter adopts the PFM–PWM hybrid control strategy. In this paper, the working principle of the proposed converter is analyzed in detail, the realization of the power factor correction mechanism and the soft switching are described, and the design methods of the key parameters are given. Finally, an experimental prototype with a 110 V-250 V input and a 48 V/100 W output is built. Experimental results verify the correctness of the theoretical analysis of the converter and its applicability to power grids.

中文翻译：

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具有宽输入范围和低总线电压的单级 LLC AC/DC 转换器

传统的单级升压 LLC 谐振 AC/DC 转换器因其功率级少、功率因数高、开关软等优点而受到广泛研究。但是，它也有几个缺点，例如输入电压低而窄，直流母线电压远高于输入电压，开关器件的应力高。因此，它一般用于110 V以下的电网。为了克服上述问题，本文提出了一种适用于110 V和220 V电网的升降压LLC谐振AC/DC变换器。除了其传统结构外，所提出的转换器还具有输入电压范围宽和总线电压低的优点。所提出的转换器采用 PFM-PWM 混合控制策略。在本文中，详细分析了所提出的转换器的工作原理，描述了功率因数校正机制和软开关的实现，并给出了关键参数的设计方法。最后，构建了具有 110 V-250 V 输入和 48 V/100 W 输出的实验原型。实验结果验证了换流器理论分析的正确性及其在电网中的适用性。