27th International AES Conference
 

PAPER SESSION 3: MODULATION AND CONTROL



3-5 Discrete-Time Modeling of Continuous-Time Pulse Width Modulator Loop


Lars Risbo. Texas Instruments Denmark, Lyngby, Denmark


Traditionally, the dynamics of continuous-time PWM loops are analyzed by using linearized continuous-time models where the comparator is modeled as a linear gain. However, this method fails to accurately explain several important characteristics such as noise aliasing, image components, and loop stability. This paper analyzes the sampling nature of the comparator and derives a general linear discrete-time loop small-signal model that can be applied to loops of any orderóboth driven (synchronized) and free running (self-oscillating).


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