Multi-cell DC-DC converters - Input differential mode filtering generic design rules and implementation

This paper deals with conducted differential mode (DM) EMI analysis and filtering for DC-DC multi-cell converters. Networking of conversion standard cells by associating them in series or in parallel faces the design of conducted EMI filtering according to the number of cells and their configuration. The problem is addressed at two levels; distributed filtering (each converter has its own DM EMI filter stage) and centralized filtering (an EMI filter stage placed upstream of the multi-cell converter association). The paper presents how to generalize and to automate the filter design and how to set the values of the components of the filters (distributed and centralized) in order to have a standard filter that is suitable regardless of the number of conversion standard cells implemented and their association type. The paper details the filter architecture selection and design methodology. The work is illustrated with practical results from a study case. This work comes in complement to past literature.