LLC Large Current Equalization Technology Based on Adjustable Capacitance

为了减小输入输出电流纹波、提高功率密度、降低开关损耗，LLC谐振变换器多采用多相交错并联结构。然而，受限于实际制造工艺，各元器件(主要为电感和电容)参数存在不可避免的偏差，这一现象在多相交错并联LLC谐振变换器中，引发各相电压增益不一致的问题，进而导致各相电流不均衡。针对这一问题，本文依托三相交错LLC谐振变换器展开研究，提出一种基于可调电容的均流模块，在不增加控制复杂度和各模块间的耦合的前提下，采用结合前馈控制与离散PID控制策略，精准控制可调电容模块对谐振电路进行容差补偿，成功实现LLC各相电路一次侧电流与负载电流的均衡分配，不仅控制策略简单，还完好保持了LLC谐振变换器固有的软开关特性，同时提升变换器的工作效率。In order to reduce input and output current ripple, improve power density, and minimize switching losses, LLC resonant converters often employ multi-phase interleaved parallel structures. However, due to inherent manufacturing tolerances, parameters of various components (mainly inductors and capacitors) inevitably deviate, which in multi-phase interleaved LLC resonant converters lead to inconsistent voltage gain across phases, resulting in current imbalance. To address this issue, this paper conducts research based on a three-phase interleaved LLC resonant converter. A current sharing module based on adjustable capacitors is proposed. Without increasing the control complexity or the coupling between modules, a control strategy that combines feed-forward control and discrete PID control is employed. This strategy precisely controls the adjustable capacitor module to perform tolerance compensation on the resonant circuit. As a result, the balanced distribution of the primary side current in each phase of the LLC circuit and the load current is successfully achieved. The proposed control strategy is not only simple but also well maintains the inherent soft-switching characteristics of the LLC resonant converter.