Modeling and Stability Analysis of Voltage Sensing based Differential Mode Active EMI Filters for AC-DC Power Converters

Passive EMI filters occupy significant volume in a power converter. Active EMI Filters (AEF) are a means to reduce the volume of passive filter components. It is essential to identify the boundaries within which the AEF could be designed and the possible volume reduction that is achievable. This work involves the modeling and stability analysis of Feedback Voltage Sense Current Cancellation (VSCC) Active EMI Filters. Type of applications that benefit from using voltage sensing over current sensing for is identified. An example of a non-PFC AC-DC converter is considered. Noise sensing networks comprising high voltage capacitors and high pass filter networks are designed for sensing noise. The overall filter implementation is modeled, and stability analysis is carried out. Suitable compensation networks are designed to make the filter viable. Major bottlenecks that limit the maximum attenuation are identified and general guidelines for the application of Feedback VSCC topology are proposed.