移相全桥变换器中RC缓冲电路对系统影响机理与优化研究

移相全桥ZVS变换器副边整流二极管电压应力较高,需要设计缓冲电路来保证系统性能。然而,加入RC缓冲电路的变换器在某种工作模式下近似为LCL三阶谐振系统,导致接近开关频率的谐振甚至在整流二极管两侧产生更高的电压应力。通过建立移相全桥ZVS变换器在能量传输模式期间的等效电路模型,揭示RC缓冲电路对系统稳定性产生影响机理及电路参数对振荡的影响规律,通过分析选取合理的RC缓冲电路参数,不仅有效降低整流二极管电压应力,同时抑制由缓冲电路带来的振荡问题,进而提高系统的效率。设计了一个3.2 k W(10 A,320 V)的实验样机,验证了理论分析的正确性。

Mechanism and optimized research on influence of RC snubber circuit in phase-shifted full-bridge ZVS converter

There are high voltage stress through rectifier diodes in phase-shifted full-bridge ZVS converter,so snubber circuit is needed to ensure performance of the system.Therefore,converter with RC snubber circuit in some cases becomes third-order unstable system,which leads to resonance close to switching frequency and even higher voltage stress through diodes.Equivalent circuit model during the energy transfer mode of phase-shifted full-bridge ZVS converter was established,and mechanism of how the RC circuit effect stability of the system and principle of how circuit parameters affect the oscillation were revealed.By analyzing and selecting appropriate parameters of RC snubber circuit,not only can the voltage stress of rectifier diodes in the transformer secondary side be inhibited,but also the oscillation brought by RC circuit be solved.In addition the efficiency of the whole system can be improved.A prototype of 3.2 kW(10 A,320 V)was designed to verify the theoretical analysis.