Effect of the Mission Profile on the Reliability of a Power Converter Aimed at Photovoltaic Applications—A Case Study

This paper presents the reliability analysis of a push-pull converter intended for connection to a 125-W photovoltaic (PV) panel. Four prototypes of the converter were built and tested, using transistors with different ratings. Failure rates were calculated using the MIL HDBK 217 and the IEC TR 62380 procedures. In the latter case, the prediction was performed taking into account an annual mission profile obtained from the intended installation site, in an area with desert climate temperatures. Failure rate results obtained with MIL HDBK 217 show small differences among the converters, the best performance obtained from the prototype with the lowest on-resistance. Results obtained with IEC TR 62380 indicate that thermal cycles have a significant effect in reliability performance, and should be considered carefully, because PV systems often see large temperature variations. With both procedures, the failure rate contributions from magnetic devices were higher than expected.