知识与财富的链接
SiC MOSFET工作频率高,温度稳定性好,应用于三电平Buck变换器中可以减小系统损耗,提高系统效率,但SiC MOSFET的高频特性会使其开关过程中的电压尖峰更为严重。针对该问题,分析了三电平Buck电路SiC MOSFET开关过程及瞬态电压尖峰产生机理;在传统的充放电型RCD吸收电路的基础上加以优化改进,设计了一种低损耗型RCD吸收电路作为电压尖峰抑制方法。首先,对充放电型RCD吸收电路和改进后的低损耗型RCD吸收电路的工作原理及损耗进行对比分析;其次,搭建了三电平Buck变换器实验装置,对吸收电容和电阻进行参数设计;最后,通过实验验证了低损耗型RCD吸收电路的有效性、参数设计的合理性;结合理论分析和实验结果表明,相比于带充放电型RCD吸收电路,带低损耗型RCD吸收电路的三电平Buck变换器具有更低的损耗。
SiC MOSFET has a high operating frequency and a good temperature stability, which can reduce the system loss and improve the system efficiency when applied to a three-level Buck converter. However, its high-frequency charac-teristics will make its voltage spike more serious during the switching process. To solve this problem, its switching process in the three-level Buck converter is analyzed, and the generation mechanism of transient voltage spikes is explored. Based on the optimization and improvement of a traditional charge-discharge RCD snubber, a low-loss RCD snubber is designed as a voltage spike suppression method. First, the working principle and loss of the charge-discharge RCD snubber and the improved low-loss RCD snubber were compared and analyzed. Second, a three-level Buck converter experimental unit was built, and the absorption capacitor and resistance of the low-loss RCD snubber were parameterized. Finally, the effectiveness of the low-loss RCD snubber and the rationality of the parameter design were verified experimentally. The combination of theoretical analysis and experimental results indicate that the three-level Buck converter with the low-loss RCD snubber has a lower system loss than that with the charge-discharge RCD snubber.
