Open loop small-signal control-to-output transfer function of PWM buck converter for CCM: modeling and measurements

A practical procedure for measuring the control-to-output transfer function of a PWM buck converter operated in continuous current mode (CCM) is given. It is shown that a simple, low cost measurement setting can be used. The results of the presented procedure shows that the frequency behavior of a PWM buck converter depends on the filter capacitor equivalent series resistance (ESR). It is also shown that models of a PWM buck converter presented in previous works yields an accurate result only if the capacitor ESR variation with the operating frequency is taken into account. The result of this work can be used in designing an appropriate feedback loop of the converters.