A simple ESR identification methodology for electrolytic capacitors condition monitoring

Electrolytic capacitors are usually used in power electronic systems for smoothing, energy storage or filtering. They have the best overall performance for these objectives being a critical element in the design of these systems, in several applications, with different requirements. But, unfortunately, in most cases, they are the most life-limiting device. The expected life of electrolytic capacitors depends on their internal temperature and is determined by the ratio of the electrolyte solution evaporation used in their fabrication. The deterioration caused by this evaporation is reflected in electrical parameters, mainly the equivalent series resistance (ESR). As the volume of the electrolyte decreases, ESR increases and capacitance decreases. Additionally, the increase in ESR has a positive feedback effect since it leads the temperature to increase and this in turn leads to further evaporation of the electrolyte leading to the ESR increase and so forth. This paper presents a simple ESR identification methodology for electrolytic capacitors condition monitoring in view of preventive maintenance to signal the need of maintenance and or replacement. The identification methodology is based on a simple continuous-time model and some recursive prediction error methods, namely, Kalman filter, gradient and forgetting factor approaches. Simulation and experimental data acquired from a step down converter were used with these algorithms. The identification methodology is also suitable for different power converter topologies

Physics Based Electrolytic Capacitor Degradation Models for Prognostic Studies under Thermal Overstress

Electrolytic capacitors are used in several applications ranging from power supplies on safety critical avionics equipment to power drivers for electro-mechanical actuators. This makes them good candidates for prognostics and health management research. Prognostics provides a way to assess remaining useful life of components or systems based on their current state of health and their anticipated future use and operational conditions. Past experiences show that capacitors tend to degrade and fail faster under high electrical and thermal stress conditions that they are often subjected to during operations. In this work, we study the effects of accelerated aging due to thermal stress on different sets of capacitors under different conditions. Our focus is on deriving first principles degradation models for thermal stress conditions. Data collected from simultaneous experiments are used to validate the desired models. Our overall goal is to derive accurate models of capacitor degradation, and use them to predict performance changes in DC-DC converters

A life prediction scheme for electrolytic capacitors in power converters without current sensor

Predicting the expected life of switching power supply is essential since unexpected failure of the subsystem can produce enormous loss. Electrolytic capacitor is the weakest among various power components in a power converter. Monitoring the Equivalent Series Resistance (ESR) variation of the electrolytic capacitor, achieving by voltage and current ripple, can estimate the converter life. Currently, Hall Effect sensor or others are current sensing options but all of them add series impedance to the capacitor and deteriorate capacitor voltage waveform. A sensor-less current waveform prediction method is proposed. Popular current mode control with the switch current signal is used. Repetitive sampling on the switch current allows capacitors current waveforms prediction without any current sensor at capacitor nodes. Together with the voltage waveform acquired, the ESR value can be calculated. ©2010 IEEE.published_or_final_versionThe 25th Annual IEEE Applied Power Electronics Conference and Exposition (APEC 2010), Palm Springs, CA., 21-25 February 2010. In Proceedings of the 25th APEC, 2010, p. 973-97

Review of Health Prognostics and Condition Monitoring of Electronic Components

To meet the specifications of low cost, highly reliable electronic devices, fault diagnosis techniques play an essential role. It is vital to find flaws at an early stage in design, components, material, or manufacturing during the initial phase. This review paper attempts to summarize past development and recent advances in the areas about green manufacturing, maintenance, remaining useful life (RUL) prediction, and like. The current state of the art in reliability research for electronic components, mainly includes failure mechanisms, condition monitoring, and residual lifetime evaluation is explored. A critical analysis of reliability studies to identify their relative merits and usefulness of the outcome of these studies' vis-a-vis green manufacturing is presented. The wide array of statistical, empirical, and intelligent tools and techniques used in the literature are then identified and mapped. Finally, the findings are summarized, and the central research gap is highlighted

Physics Based Modeling and Prognostics of Electrolytic Capacitors

This paper proposes first principles based modeling and prognostics approach for electrolytic capacitors. Electrolytic capacitors have become critical components in electronics systems in aeronautics and other domains. Degradations and faults in DC-DC converter unit propagates to the GPS and navigation subsystems and affects the overall solution. Capacitors and MOSFETs are the two major components, which cause degradations and failures in DC-DC converters. This type of capacitors are known for its low reliability and frequent breakdown on critical systems like power supplies of avionics equipment and electrical drivers of electromechanical actuators of control surfaces. Some of the more prevalent fault effects, such as a ripple voltage surge at the power supply output can cause glitches in the GPS position and velocity output, and this, in turn, if not corrected will propagate and distort the navigation solution. In this work, we study the effects of accelerated aging due to thermal stress on different sets of capacitors under different conditions. Our focus is on deriving first principles degradation models for thermal stress conditions. Data collected from simultaneous experiments are used to validate the desired models. Our overall goal is to derive accurate models of capacitor degradation, and use them to predict performance changes in DC-DC converters

Accelerated Aging in Electrolytic Capacitors for Prognostics

The focus of this work is the analysis of different degradation phenomena based on thermal overstress and electrical overstress accelerated aging systems and the use of accelerated aging techniques for prognostics algorithm development. Results on thermal overstress and electrical overstress experiments are presented. In addition, preliminary results toward the development of physics-based degradation models are presented focusing on the electrolyte evaporation failure mechanism. An empirical degradation model based on percentage capacitance loss under electrical overstress is presented and used in: (i) a Bayesian-based implementation of model-based prognostics using a discrete Kalman filter for health state estimation, and (ii) a dynamic system representation of the degradation model for forecasting and remaining useful life (RUL) estimation. A leave-one-out validation methodology is used to assess the validity of the methodology under the small sample size constrain. The results observed on the RUL estimation are consistent through the validation tests comparing relative accuracy and prediction error. It has been observed that the inaccuracy of the model to represent the change in degradation behavior observed at the end of the test data is consistent throughout the validation tests, indicating the need of a more detailed degradation model or the use of an algorithm that could estimate model parameters on-line. Based on the observed degradation process under different stress intensity with rest periods, the need for more sophisticated degradation models is further supported. The current degradation model does not represent the capacitance recovery over rest periods following an accelerated aging stress period

Study of Capacitor & Diode Aging effects on Output Ripple in Voltage Regulators and Prognostic Detection of Failure

Objectives: To design and simulate a buck converter and detector circuit which can prognostically indicate the power supply failure. Failure of Aluminium Electrolytic Capacitor (AEC) is considered as the parameter causing the power supply failure. To analyse variation of output ripple voltage due to possible changes in the Equivalent Series Resistance (ESR) and effective capacitance of the capacitor and design a detector to detect the failure of power supply prognostically.Methods:  A DC-DC buck converter in SMPS topology is designed by assuming an input voltage of 12V with 3 volts possible fluctuations and an output voltage of 3.3 volts is desired. Simulation is carried out to measure the variation in output ripple voltage caused due to aging of electrolytic capacitor using TINA by Texas Instruments. A detector is also designed to compare the ripple voltage and a predefined threshold voltage so as to indicate the possible failure of Switched Mode Power Supply (SMPS) well in advance by monitoring the output ripple increase.Novelty:    Having a fault tolerant power supply is very important in safety critical applications. Here by monitoring the output ripple variation, the degradation of AEC is predicted by calculating the ESR and capacitance variation. This simple yet effective prognostic detection will support in the design of fault tolerant power supplies.Highlight: It is found that, the ripple at the output increases with aging of the electrolytic capacitor, as with time the equivalent capacitance decreases and Equivalent Series Resistance (ESR) of the capacitor increases. The designed detector output is found to prognostically indicate the failure of SMPS