Output Filtering Capacitor Bank Monitoring for a DC–DC Buck Converter

The remote prognostic, diagnosis, and maintenance of electrolytic capacitors are research topics of interest due to their presence in numerous electronic devices and their increased susceptibility to degradation over time. The authors’ focus in this article is on the proposal of a new diagram for monitoring the parameters of the capacitors that compose the filter bank of a DC–DC buck converter by connecting them in parallel. Each capacitor is modeled by an equivalent series R–C circuit composed of an equivalent capacitance and an equivalent series resistance (ESR). The method used allows successive investigation of the three capacitors that compose the bank by triggering discharge/charge sequences, acquiring the voltages at the capacitor terminals, and estimating the time constants of each capacitor using a parameter observer. During the estimation of the parameters of a capacitor, the converter uses the other two capacitors maintained in operation. The monitoring cycle of all capacitors of the bank lasts less than 40 ms, not significantly affecting the operation of the converter. The study undertaken is correlated with the thermal map of the board on which the converter is made. The dispersion of the measured values of the equivalent capacitances is below 0.25%, and of the ESR below 2.6%. The major advantage of the method is that the monitoring is performed online and in real time.