Reliability Comparison of Bidirectional Automotive DC/DC Converters

The energy consumption of modern vehicles has increased rapidly in the last years. Hence, future vehicles require larger batteries and a higher generator power to supply the vehicle loads. For an efficient transport of energy an additional voltage level is introduced, so that dc/dc converters are necessary to couple the different voltage levels. Besides the increased energy consumption a higher safety level is required for the energy net due to modern assistance systems and for the purpose of autonomous driving. Faced with these requirements, it is necessary to investigate the components of an energy net regarding their reliability. This paper provides an overview of possible bidirectional dc/dc converter topologies to couple two voltage levels and analyses their reliability. A method is presented to calculate the failure in time values of the devices of a single-phase, a multi-phase and a multi-phase buck-boost converter with coupled inductors, based on an automotive driving cycle. Furthermore, typical converter faults are investigated and fault probabilities are compared between dc/dc converter topologies. The results show that the multi-phase converter has a significantly lower failure probability than the single-phase converter, while the multi-phase converter with coupled inductors has the least probability with respect to some individual faults.