A power interface device includes a main switching converter, an auxiliary switching converter, a feedback sense circuit, an error amplifier, a high pass filter, a transient detection circuit, and an auxiliary control circuit. The transient detection circuit is configured to receive the higher frequency component of the transient signal and output an enable signal when the higher frequency component of the transient signal falls outside of an operating window range defined by a first threshold and a second threshold and output a disable signal when the higher frequency component of the transient signal stays within the operating window range. The auxiliary control circuit configured to activate the auxiliary switching converter in accordance with the enable signal and to deactivate the auxiliary switching converter in accordance with the disable signal.
