Input filter interactions in multi-module parallel switching-mode power supplies

One of critical issues when integrating subsystems is the stability problems, robustness of the subsystems and degradation resulting from interaction between the subsystems. Even though the subsystems may be well-designed for stand-alone operation, this interaction can leads to instability and performance problems after system integration. In this paper, a generalized method to analyze the effect of EMI filter to the stability and performance of the multi-module parallel converters is discussed. The reason of instability is analyzed and the design criteria EMI filter is presented. Switched-mode converters and input filters are modeled using two-port modeling technique and the reflected transfer functions are characterized by using linear fractional transformation (LFT).