Sampled-Data Modeling and Analysis of the Power Stage of PWM DC-DC Converters

Abstract

The power stage of the PWM DC-DC converter is modeledand analyzed using the sampled-data approach.The work addressescontinuous and discontinuous conduction mode under voltage mode control,and continuous conduction mode under current mode control.For each configuration, nonlinear and linearized sampled-data models andcontrol-to-output transfer function are derived. <p>Using this approach, both current mode control and discontinuous conduction modecan be handled systematically in a unified framework,making the modeling for these cases simpler than with the use of averaging.The results of this paper are similar to the results of Tymerski,but they are presented in a simpler manner tailored to facilitate immediate application to specific circuits. <p>It is shown howsampling the output at certain instants improves the obtained phase response.Frequency responses obtained from the sampled-data model aremore accurate than those obtained from various averaged models. In addition, a new ("lifted")continuous-time switching frequency-dependent model of the power stage isderived from the sampled-data model. Detailed examples illustrate themodeling tools presented here, and also provide a means of comparingresults obtained from the sampled-data approach with those obtainedfrom averaging.