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Recently, there has been an increase in the application of fuzzy logic controllers (FLCs) for control of power electronic converters. Due to FLCs complex algorithm, their realization often calls for a compromise between cost and performance. In this paper, it is shown that the rule table of most of the two-input FLCs used with power converters can be approximated into a single non-linearity. This allows the controller to be easily realized using simple, fast, and inexpensive analog circuits. The simplified 'non-linear function controller (NLFC)' developed in this manner is shown to be equivalent in performance to the original FLC through simulations. The NLFC concept is then applied to PI-FLC, a type of FLC popular in power converter control applications. This results in the PI-FLC being replaced by a simple 'non-linear PI controller (NPIC)'. Using this simplification, the design of NPICs to obtain good dynamic performance in power converters is explained. An example design of NPIC for controlling a DC-DC boost power converter is presented. Experimental results are also presented to demonstrate the superior dynamic performance of the converter with NPIC as against that with linear-PI controller.