A Case Study for Reliability Evaluation of an External Computer Power Supply

This paper analyzes the reliability calculation method and elaborates on lifetime implications for an external computer power supply unit. Calculation is performed following MIL-HDBK-217 specifications for reliability of each individual module and the paper can be seen as an example for using this method. Design of the power supply is constrained due to requirements for safety of consumer products, and this somewhat influences the lifetime and reliability aspects. This paper provides a clear perspective on contribution of protection circuits to total reliability. The output capacitor bank yields as the most critical component and options for reliability improvement are next discussed. The effect of voltage derating and the effect of capacitor technology improvement are quantified through calculation of the system reliability and lifetime. Bringing into discussion real numerical values for failure rates, this paper helps knowledge development in the upcoming field of reliability of power converters.