Adaptive model following control for switching regulators with input filters

Abstract

A switching power supply (SPS) requires an input filter to reduce the high frequency current harmonics generated by switch action that are returned to the source. The interaction between the input filter and control loop of the SPS can adversely affect loop stability, audiosusceptibility and output impedance. A novel input filter compensation approach, based on the positivity and hyperstability approach to Adaptive Model Following Control (AMFC), is proposed. A modified implementation of AMFC (mAMFC), which also mitigates the effects of parameter uncertainty and drift on converter stability, is shown to reduce the disruptive effects of input filters on the control loop. An analog hardware implementation of mAMFC of a buck converter with an input filter is demonstrated and compared to simulation results. The data demonstrates that mAMFC reduces the adverse effects of an input filter on the open-loop frequency response and audiosusceptibility of a buck converter and lowers its output impedance.