Capacitor Degradation Monitoring for LLC Resonant Converter based on Discharging Profile

The Multi-layer Ceramic (MLC) capacitor is a critical yet vulnerable component in power electronic converters, where degradation leads to a decrease in capacitance. Monitoring capacitance is crucial for predicting the lifespan of MLC capacitors, ensuring the safe and reliable operation of converters. This paper introduces a monitoring scheme specifically for LLC resonant converters that estimates the capacitance of its capacitor on the output side. The scheme leverages large-signal discharging transient trajectories for estimating MLC capacitor parameters without the need for extra sensors. By examining the relationship between these trajectories and the capacitor parameters, capacitance is determined using a calculation model based on the output voltage and current transient trajectory. Corresponding simulation and experimental analysis is conducted in the end.