Load-Impedance Based Interactions in Regulated Converters

Abstract:
The effect of load impedance on the dynamics and performance of a regulated converter is investigated. Theoretical formulation is derived utilizing two-port modelling technique. It is definitively shown that the load interactions are reflected into the converter dynamics via the internal open-loop output impedance. At the frequencies, where the loop gain is much higher than unity, the internal closed-loop output impedances acts as a boundary for the control-bandwidth reduction. The loop gain is always affected, whenever the internal open-loop output impedance is equal or greater than the load impedance. The converters are sensitive especially to the capacitive and resonant-type loads. The sensitivity is dependent on control mode, and cannot be much reduced by means of basic controller design.