Using a simple charge-discharge circuit to estimate capacitors equivalent circuit at their operating conditions

The aim of this paper is to present a very simple, cheap and practical experimental technique that is able to estimate capacitors equivalent circuit for a wide range of frequencies. Capacitors equivalent circuit changes with temperature, aging and frequency. Thus, since capacitors have a wide range of applications, particularly in power electronics applications, the knowledge of their model at their operating conditions can lead to better design proposals. This issue is particularly important for aluminum electrolytic capacitors since they are the preferred capacitor type in power electronics applications, and simultaneously one of the most critical components in such applications. The proposed technique uses a very simple charge-discharge circuit together with an oscilloscope connected to a PC with MATLAB software. Thus, using capacitor current and voltage and the Least Mean Square Algorithm it is possible to compute the capacitors capacitance and their intrinsic resistance for a wide range of frequencies.