Simulation for reliability design of power electronic circuits

This thesis presents and applies an approach for reliability analysis of power electronic circuits using simulation. The approach is based on the First-Order Reliability Method (FORM) and is applied to a closed-loop up-down converter design that is currently in mass production.; Recent reductions in computation time for power circuit simulation motivated this work. These reductions make it practical to use simulation to analyze weaknesses in design. The ultimate goal is to increase yield, the percentage of acceptable circuits, by identifying components or component combinations whose variations result in higher failure rates. For future applications, the adopted analysis method satisfies two important requirements: it is amenable to analyzing circuits with a large number of varying parameters (a high-dimensional parameter space); and it is able to analyze the reliability of designs adhering to six sigma standards (a failure rate of less than four in one million).; FORM was developed in the civil engineering reliability community to analyze the structural reliability of a single structure which ideally has an extremely low failure rate. Conceptually, the method is equally applicable to determining the yield, a measure of the design reliability, of an ensemble of circuits under parameter variation. The methodology is based on efficient calculation of the multivariate failure probability integral, which is equivalent to the multivariate yield integral. The calculation involves transforming variables to a standard normal space and linearizing performance criteria failure surfaces near the points of most-likely failure. Properties of the standard normal space facilitate evaluation of the multivariate yield integral.; The reliability analysis of power electronic circuits is implemented by the development of a simulation environment which consists of three main blocks of software: reliability analysis software, circuit simulation software, and a program to interface the two. A specialized interface was developed to coordinate parallel calculation of the gradient. The gradient calculation is typically one of the most time-consuming steps of an optimization procedure, when a finite-difference approximation is needed. Parallel calculations were executed on six networked workstations.; Reliability analysis methods were applied to a voltage divider, rectifier, an open-loop up-down converter and a similar closed-loop circuit that is currently in mass production. The voltage divider, rectifier, and open-loop up-down converter represented relatively simple circuitry for which an initial validation of the simulation environment and confirmation of results were possible. Confirmation of results were determined by several reliability analysis methods: the First-Order Reliability Method, the Second-Order Reliability Method, Monte Carlo and importance sampling analyses. The closed-loop production design circuit represented relatively complex circuitry whose analysis demonstrated the application of FORM to a circuit with pulse-width modulation feedback. Analyzing this circuit also provided the impetus for the development of the parallel simulation infrastructure and motivated other hardware and software design considerations which are potentially useful for future applications.