A Soft-Defined Pulse Width Modulation Approach—Part II: System Modeling

In this work we model from a system design perspective the realization of a novel mixed-signal approach to pulse width modulation (PWM). The working principle for the approach, along with an implementation scheme comprised of a digital zero-positioning (ZP) followed by a proper digital-to-analog converter (DAC) and comparator, has been introduced in a companion paper. We here focus on analyzing the global system in order to get a model of its performances in terms of dynamic range and non-linearity. Since non-linearities and quantization noise occur between the ZP and the comparator, firstly, upstream models for them are provided; then their effect on the PWM signal is calculated by means of a downstream model of perturbations at the input of an ideal natural sampling PWM. Finally, an exhaustive formula for the resulting dynamic range is given and some configurations of practical interest are proposed.