Online Output Capacitor Monitor for Buck DC-DC Converter

Electrolytic capacitor is widely used in switching power supply module as filter capacitor, but it has higher failure rate than other components in DC-DC converter. In order to monitor the performance of the electrolytic capacitor, the equivalent series resistance (ESR) is selected as monitoring target. This paper presents an online monitor method for Buck converter output capacitor's ESR and C, by sampling output voltage at falling edges and rising edges of the switching signal. A trigger circuit and a amplify circuit are analyzed. The effectiveness of the proposed method is verified by the experimental system. The proposed method avoids measuring the inductor current, simplifies the trigger circuit structure, and keeps the topology of the switching power supply module, which improve the convenience of the application of the scheme.