Reliability analysis and enhancement of the AC/DC stage of a 3.3 kW onboard vehicle battery charger

A modern 3.3 kW onboard battery charger typically includes a grid-connected AC/DC rectifier stage with a unity power factor operation and a transformer isolated DC/DC converter. The failure modes and effect analysis (FMEA) is one of the main tools to evaluate the charger reliability. The main specifications, circuit configurations, control structures and analysis of the AC/DC stage of the charger for a normal operation is presented and discussed. Some important electrical faults are selected for further investigations, analysis and reliability enhancement. For each case, the circuit is analyzed and an appropriate detection algorithm is proposed. Moreover, some post-fault actions are suggested for each case. Some design recommendations are provided to improve the reliability.