同步控制双向LLC谐振变换器

Bidirectional LLC Resonant Converter with Synchronous Control Method

本文提出了一种同步控制的双向LLC谐振变换器。为使变换器在正向、反向工作时拓扑结构相同,在电路中增加了一个辅助电感。该辅助电感除了可以使双向LLC谐振变换器的双向工作特性完全对称外,还可以帮助开关管实现软开关。文章提出的双向LLC谐振变换器结构简单、控制方法易于实现。当变换器开关频率小于谐振频率时,所有开关管均可以实现零电压开通(ZVS);当变换器开关频率大于等于谐振频率时,软开关特性与传统LLC谐振变换器相同。因此变换器具有较高的效率,很适合应用于能量双向流动的场合。同步控制的双向LLC谐振变换器与传统二极管整流的单向LLC谐振变换器的工作特性存在差别,为了精确分析,文章提出了新的等效电路模型,并给出了同步控制双向LLC谐振变换器的电压增益公式和软开关条件。最后通过实验验证了理论分析的结果。

A bidirectional LLC resonant converter with synchronous control method is proposed in this paper. In order to achieve the bidirectional operation capability, an auxiliary inductor is added in the converter. In this way the topology in forward operation and backward operation is exactly the same. Also, the auxiliary inductor can help the MOSFETs to achieve soft switching. The control scheme of the proposed bidirectional LLC converter is very simple and it's easy to be achieved. When the switching frequency is lower than the resonant frequency, all the switches can achieve ZVS; when the switching frequency is higher than the resonant frequency, soft switching condition is same with the traditional LLC resonant converter. So the efficiency of the proposed converter is high, and it's attractive in the applications which required bidirectional power flow capability. The operation principle of the proposed synchronous LLC resonant converter is different from the traditional LLC converter, and a new equivalent model is proposed to analyze the characters in detail. A prototype is built and experimental results are given to verify the theoretical analysis.