A Current-Sensorless Online ESR and C Identification Method for Output Capacitor of Buck Converter

As electrolytic capacitor is apt to fail in power circuits, it is very important to identify its electrical parameters, mainly the equivalent series resistance (ESR) and capacitance (C). A noninvasive online identification method of capacitor´s ESR and C for continuous-conduction-mode (CCM) buck converter is proposed in this paper. Based on the ac component of capacitor voltage, the calculation model is founded. By sampling the pulse width modulation signal and output voltage, the method needs no current sensor and is effective for the CCM buck converter operating at different conditions. Implementation of the identification system is presented. The tests are carried out for different aged capacitors and ambient temperatures. The experimental results validate the effectiveness of the method.