Research On Reliability Of Aluminum Electrolytic Capacitor In Smps

Switching Mode Power Supply (SMPS) is the most important source for electric or electronic equipments. Due to the features of large capacitance, high resisting voltage and high cost performance, aluminum electrolytic capacitors have been widely applied in SMPS. Their main functions such as smoothing ripple voltages, filtering noises, storing energy and so on make them to be necessary components for SMPS while their failure rates are the most in these devices unfortunately. So the reliability problem of aluminum electrolytic capacitors is the essential part of the one of SMPS. Traditional method for researching reliability is based on lots of success-failure experiments. But presently design cycles of products are more and more short, which makes the traditional method ineffective, while the method based on performance degradation matches this situation much. This paper has studied the reliability of aluminum electrolytic capacitor by the approach of the degradation, analyzed its degenerate mechanism and process, got some degenerate data by experiments, summarized the rule, built the models and analyzed the problem about its maintenance.This paper has studied the mechanism of degradation and failure of aluminum electrolytic capacitor, built the equivalent circuit model based on its physical structure, researched the degenerate representation on the parameters in the circuit model based on the raison of the degradation. Meanwhile this paper has also summarized the basic theory of the reliability analysis method based on performance degradation, described the process of single factor degradation and final failure and built the corresponding model.This dissertation has designed a target circuit, an APFC (Active Power Factor Correction) circuit, and its monitoring equipment for experiments, and chose the output capacitor of the target circuit as the target component. By mean of experiments to the target circuit in different environments whose temperatures are respectively 20℃, 60℃and 80℃, this dissertation has recorded the voltage waveform data of expected points. Then by processing these data with certain algorithms, this paper calculated the values of the capacitance and ESR (Equivalent Serial Resistance) of the target component, and painted the time variation curves of these parameters. Based on the results, this dissertation regressed the data to build models of the parameters'degradation, summarized the rules and designed the corresponding reliability prognostic models.Finally this dissertation described the strategies of maintenance based on conditions monitored and then modeled the strategy utilizing prognostic models. Depending them this paper described and analyzed the maintenance of aluminum electrolytic capacitors, and derived the related optimization problem with the help of the reliability prognostic model built before.This research has studied every part of reliability problem of aluminum electrolytic capacitors and in particular will help solute its status monitoring, parameter calculation, lifespan prognosis, maintenance strategy optimization and so on. This research has applied reliability analysis method based on performance degradation in each period and built corresponding models, and will help pack up related theories and methods.