A power supply system includes a power source; a load device configured to receive power from the power source; and a power interface device coupled to the power source and the load device and configured to change a first voltage provided by the power source to a second voltage for operating the load device. The power interface device include a main switching converter configured to operate at a first switching frequency and source low frequency current to the load device and an auxiliary switching converter coupled in parallel with the main switching converter and configured to operate at a second and different switching frequency and source fast transient high frequency current to the load device.
