In high-load-current LLC dc–dc converter, synchronous rectification (SR) is usually used to reduce the secondary loss. As a lossless, low-cost, and small-volume SR control strategy, the drain–source voltage of SR switches sensing method is used widely in industrial applications. However, when the load current increases, the voltage ringing across SR switches during O stage is more and more severe and reaches zero eventually. When the voltage ringing reaches around zero in LLC converter, the voltage-sensing-method SR controller will generate the false driving signal, which makes SR switches turn on early and causes the converter works abnormally. This article presents the accurate analysis and design of the circuit parameters of LLC dc–dc converter to prevent the voltage ringing across the SR switches reaches around zero. The voltage ringing model is established, and the parameters design principle is given. By using the proposed design guideline, the voltage ringing across SR switches will always be higher than zero over the full load range, which eliminates the turn- on early issue or turn- on several times in one cycle issue. Therefore, this article can provide a design reference and guideline for the high-load-current and high-output-power LLC converter with voltage sensing SR control strategy. A 2.16 kW SR LLC dc–dc converter prototype is built according to the proposed design guideline, and the experimental results verify the correctness and effectiveness of the analysis.

中文翻译：

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同步整流LLC DC-DC变换器电路参数的精确分析与设计

在高负载电流LLC dc-dc 转换器，同步整流 (SR) 通常用于降低次级损耗。作为一种无损、低成本、小体积的SR控制策略，SR开关检测方法的漏源电压在工业应用中得到广泛应用。然而，当负载电流增加时，在 O 阶段 SR 开关两端的电压振铃越来越严重，最终达到零。当电压振铃达到零附近LLC 转换器，电压感应方式的 SR 控制器会产生虚假的驱动信号，使 SR 开关导通过早导致转换器工作异常。本文介绍了对电路参数的准确分析和设计LLC dc-dc 转换器，以防止 SR 开关上的电压振铃达到零附近。建立了电压振铃模型，给出了参数设计原则。通过使用建议的设计指南，SR 开关上的电压振铃在整个负载范围内将始终高于零，从而消除了转向 在早期发行或转向 在一个周期中多次发行。因此，本文可为高负载电流和高输出功率的设计提供参考和指导。具有电压感应 SR 控制策略的 LLC 转换器。2.16 kW SRLLC dc-dc 转换器原型是根据提出的设计指南构建的，实验结果验证了分析的正确性和有效性。