Real-time median filtering with a fast hardware sorter

The authors describe a fast hardware implementation of a median filter with emphasis on possible applications to power electronics. The authors focus on the median filter as a relatively easily understood example which illustrates the potential of nonlinear filtering in power electronics. To show the power of the median filter, a review of offline results first presented by W. C. Karl et al. (1990) compares output from the median and linear filters for a common input waveform: a switch voltage transient in a flyback power converter. New offline results show the result of filtering a noisy motor tachometer signal with the median filter. Some of the problems and tradeoffs associated with several traditional median filtering architectures are outlined. The proposed architecture for a real-time median filter and the benefits of the design are discussed. Results from a prototype of the design are presented