A new large signal average model for variable frequency pulse-width modulators

This paper introduces a large signal average model of a voltage regulator controlled by a variable frequency pulse width modulator (PWM). Variable frequency PWM techniques significantly reduce switching action delays and improve transient response compared to fixed frequency PWMs. The conventional average model cannot accurately predict the modulator behavior during variable frequency operation. In this paper, the effect on the modulator gain of the variable frequency operation is analyzed and incorporated in the average model. Using a variable frequency multiphase buck regulator in CPU core power applications as an example, the new large signal model is derived and demonstrated.