Two-stage vs One-stage Design for A Bidirectional 400V/12V 6kW Auxiliary Power Module in Electric Vehicles

A 250V similar to 450V/10 similar to 16V auxiliary power module (APM) is needed for electric vehicles to power the 12V load, such as on-board PbA battery, GPS and steering motor. With the era of connected and autonomous vehicles starting, the load of the 12V system is even higher given numbers of sensors and radars being equipped. In some cases, the 12V system needs to be able to provide 6kW instantaneous power, yielding >500A output current. This paper compared two design candidates, i.e., single-stage LLC design with a two-stage interleaved Buck + DCX design, aiming at 3.5kW rated power and 6kW peak power. Simulation results show the two-stage design is a more qualified candidate for this high-power application. Then a two-stage prototype was built and tested. Experimental results show similar to 96% efficiency with a power density of >2kW/L, thanks to the excellent switching performance of SiC MOSFETs and low switching stress by DCX.