Features and challenges for Auxiliary Power Module (APM) design for hybrid/electric vehicle applications

Electric and hybrid electric vehicle (EV/HEV) architectures require a small DC/DC converter to replace a conventional vehicle's alternator. The small DC/DC converter, also described as the vehicle Auxiliary Power Module (APM), provides power flow between the vehicle high voltage (HV) and low voltage (LV) DC bus. The APM HV interface is connected to the HV DC bus that contains energy storage system (e.g., HV Battery) and multiple power conversion units (e.g., Traction Inverters). The APM LV interface is connected to the vehicle LV DC bus along with low voltage battery, and provides power to vehicle 12V accessory loads and other electronic control modules. Therefore, the design and operational features of the APM have significant impact on vehicle performance, overall efficiency, electric range, and to ensure a continuous power source for all the LV DC bus components. In this paper, features, performance, modes of operation, design challenges and system integration of an APM are presented with simulation results. Detail experimental results are also presented with conclusive comparison between design prediction and test data. This paper also describes power flow, load shedding, sizing and other electrical/mechanical design considerations of the APM.