Flying capacitor based variable voltage converter

A method of controlling a powertrain converter comprising:

• directing current into an inductor of the converter to create a field;
• in response to a power demand signal exceeding a threshold, collapsing the field to flow a charge to a flying capacitor to boost a voltage of a bus capacitor such that the voltage of the bus capacitor exceeds a voltage of the flying capacitor;
• and
• in response to a power demand signal dropping below the threshold, coupling the flying capacitor and the bus capacitor in parallel and directing charge into both the flying capacitor and the bus capacitor as the field collapses.

A vehicle comprising:

• an electric machine configured to propel the vehicle;
• a variable voltage converter (VVC) including an inductor, a bus capacitor and a flying capacitor;
• and
• a controller configured to modulate switches of the VVC in a boost mode such that an inductor current created by a collapsing field of the inductor is boosted by the flying capacitor and directed into the bus capacitor at a drive voltage of the electric machine and, in response to a power demand signal transitioning to negative, operate, in a steady-state, the switches in a pass-through mode to couple the flying capacitor and the bus capacitor in parallel and flow charge.