In this thesis, integrated active filter auxiliary power modules (AFAPMs) is presented in electrified vehicle applications. A topological evaluation is conducted particularly for the auxiliary power module (APM) applications in the electrified vehicles. Several primary and secondary base topologies are compared in terms of VA rating and performance. Multiple input/output topology configurations are compared with different connection configurations and control schemes. The MOSFET loss analysis is given. Based on the MOSFET loss analysis, the modular full bridge current doubler with input-series-output-parallel configuration presents better performance in terms of the switch efficiency and cost analysis. Bulk capacitor banks occupy large volume and impact the reliability in the traction inverter and HV battery charger in the vehicle applications. A capacitor-less design is relatively urgent for the next generation electrified vehicle. Active filter (AF) is one potential solution to reduce the corresponding dc-link capacitance. However, additional components are required which increases the system complicity and decreases its reliability. Hence, it would be great to integrate the AF into the LV battery charger for the vehicle applications. Based on the power switch requirements, the AFAPM is evaluated for traction inverter and HV battery charger, respectively. The evaluation result shows that the AFAPM for the HV battery charger system is a feasible and attractive solution. Furthermore, a simple and effective dual-mode dual-voltage charging system operating principle is proposed. The integrated AFAPM converter charges the LV battery when the vehicle is running and operates as an AF when the vehicle is connected to the grid and the HV battery is charging. Hence, the low-frequency second-order harmonic current is alleviated without a bulk capacitor bank or an extra AF circuit in the HV battery charger. For magnetic design, there is a trend toward integration and planarization. Two planar transformers are built for two different AFAPM prototypes. A minimized leakage inductance method is presented and implemented on a 20:1 center-tapped planar transformer. Three different integrated AFAPM converters are proposed. By applying these AFAPM converters, the required extra components to form the AF for the HV battery charger are reduced and thus the cost, size and weight for the dual-voltage charging system in the electrified vehicle applications can be reduced. Two prototypes are built. The experiments show promising results confirming the effectiveness of the proposed converters. / Dissertation / Doctor of Philosophy (PhD)