On-board electric vehicle (EV) chargers convert grid ac voltage to dc voltage to charge a high-voltage battery pack. High efficiency and high power density single-phase ac-dc converters are desirable in such applications to reduce the heat loss, volume and weight of these chargers. Moreover, the capability of bidirectional conversion is preferred for potential vehicle-to-grid applications. This paper presents the system ar-chitecture and embedded digital control implementation of a 7 kW, universal ac (120-240 VAC) to 400 VDC single-phase ac-dc bidirectional converter. The converter features an interleaved 6-level flying capacitor multilevel (FCML) ac-dc stage and a series-stacked buffer for buffering twice-line frequency pulsating power to achieve high efficiency and power density. Test results that demonstrate both ac-dc power factor correction (PFC) and inverter operation at kilowatt levels are provided.

There is an increasing need for more efficient power conversion from 48 Vdc to point-of-load (PoL) applications in datacenters. This work presents a new hybrid converter with Multi-Level Binary (MLB) voltages on the flying capacitors that is well-suited for PoL applications with very high conversion ratios. The proposed MLB-PoL converter can be viewed as an 8-to-1 multi-phase doubler switched-capacitor (SC) converter merged with a two-phase interleaved buck converter. Compared to other two-phase hybrid SC topologies, multi-phase operation can help achieve higher conversion ratio in the SC stage with an equal or fewer number of components, and thus reduce the switch andinductor stress of the following buck stage. In addition, the output inductors in the proposed topology benefit from a frequency multiplication effect similar to that of the flying capacitor multilevel (FCML) converter. This can help further reduce the inductor size without increasing the switching frequency. A 48 V to 2.5-1.0 V converter prototype with 65 A output current was built and tested. At 48 V to 2 V, the prototype achieved 95.1% peak efficiency (94.3% including gate drive loss) and 395 W/in3 power density.