Active EMI filters for automotive motor drives

EM1 filters for automotive motor drives must achieve stringent EM1 specifications while meeting tight cost constraints. This paper explores the use of low-cost active circuitry to suppress motor drive emissions, thus reducing passive filtration requirements. Challenges to the use of active EM1 filters in this application are outlined, and means for addressing these challenges are presented. A voltage sense, current drive active filter is developed that greatly enhances the performance of filter capacitors. The proposed approach is applied to an input filter for an automotive electro-hydraulic power steering pump drive. Experimental results are presented that demonstrate the feasibility and high performance of this approach and illustrate its advantages over conventional filter designs.