基于电流平衡单元的输入并联输出并联型LLC谐振变换器模块

输入并联输出并联(IPOP)型直流变换器广泛适用于低电压大电流工作场合,难点在于如何实现各子模块之间的输入电流均流(ICS)和输出电流均流(OCS)问题,现有解决方法均为闭环控制策略。提出了基于电流平衡单元的IPOP型LLC谐振变换器模块,通过电流平衡单元电磁耦合作用可以开环实现LLC谐振变换器模块间ICS和OCS,使整体IPOP型直流变换器稳定工作。LLC谐振变换器工作在近似谐振频率下可实现高频隔离直流变压器功能,保证逆变侧零电压开关(ZVS)及整流侧零电流开关(ZCS),同时具备高功率密度和高效率。采用电流平衡单元代替传统闭环控制策略解决IPOP系统模块间电流不平衡问题,省去采样和控制电路,提高系统稳定性,降低系统成本。通过对电流平衡单元的电磁模型分析,导出等效电路模型,并通过其工作暂态电流与稳态电流仿真说明电流平衡原理。最后搭建基于电流平衡单元的IPOP型LLC直流变换器实验系统,验证所提出电流平衡方案的有效性和正确性。

Current Balancing Cell Based IPOP LLC Resonant Converter Modules

The input-parallel output-parallel ( IPOP) DC-DC converters are very suitable for low voltage and high current applications. For the IPOP converter, the way to ensure input-current sharing ( ICS ) and output-current sharing ( OCS) among the constituent modules is difficult. All the existing methods are closed-loop control schemes. In this paper, the IPOP LLC resonant converter modules are developed based on current balancing cells. Through the magnetic-coupling effect of the current balancing cell, the LLC resonant converter modules can achieve ICS and OCS that guarantee that the IPOP system work stably. The LLC resonant converter can be used as a high-frequency isolation DC transformer under the quasi-resonant mode, which can achieve zero voltage switching ( ZVS) for the inverter side and zero current switching ( ZCS) for the rectifier side so as to ensure high power density and high efficiency. By employing the current balancing cell instead of the traditional control schemes to solve the unequal current-sharing problem of IPOP system, the sampling and control circuit can be saved, which ensures high reliability and low cost. From analyzing the electromagnetic mode of the current balancing cell, its electrical circuit model can be built. And the simulations of the current balancing cell ’ s steady-state and dynamic-state current-sharing performances demonstrate the working principle. Finally, an IPOP LLC resonant converter module hardware prototype based on the current balancing cell is designed and built up to verify the validity and performance of the proposed solution.