Dynamical Characterization of Input-Voltage-Feedforward-Controlled Buck Converter

The use of input-voltage-feedforward (IVFF) control has become a popular method to implement a low-cost bus converter in the telecommunications distributed power architectures because the IVFF control can provide adequate output-voltage accuracy in respect to the variations in the input voltage even at open loop, when applied to a buck converter. The method in itself is well known from the 1980s, but the dynamical features that the method would provide have not been fully investigated and reported. The results of the investigations made in this paper show that the IVFF control would provide input-noise attenuation comparable to the peak-current-mode control, voltage-loop gain largely independent of input voltage, and highly reduced input-filter interactions as compared to the voltage-mode control. The main disadvantage is the reduced output-voltage-load-transient response due to the input-voltage-dependent maximum duty ratio. The observations are supported with comprehensive experimental measurements