Effects of Non-ideal Compensators on DC Converter Feedback Control Stability
Date Issued
2015
Date
2015
Author(s)
Yin, Ching-Wei
Abstract
DC power converters have been a crucial part of the power system for computer central processor units (CPU), the so-called “v-core” application. The feedback design of a DC converter plays an important role for the system behavior. In such a system, the information contained in the control loop gain function is essential to the system stability and load transient response. An accurate modeling of the loop gain function is therefore an important task for the overall design. The loop gain function consists of two parts. One is the small-signal low-frequency model of the converter switching circuit and duty-cycle modulator, and the other is the feedback compensator. Continuously efforts have been reported, even until very recently, to improve the accuracy of the small-signal model. The feedback compensator part, however, has received little attention. As the requirement of the control bandwidth is drastically increased for future v-core applications, both parts need accurate higher-frequency modeling. In this thesis, the effects of the non-ideal characteristics of the operational amplifier on the compensator transfer functions are investigated. The results show surprising behavior that has not been reported elsewhere. This includes the possibility of generating new complex poles and a positive zero in the compensator transfer function that may affect the stability margin of the converters. Several commonly-used compensator types are analyzed. Two practical DC converter examples are used for illustration. Simulations and experimental results are used for verification. The theory and equations developed in this thesis can be used for better assessments of the converter stability performances and better optimization of the controller chips.
Subjects
voltage regulator (VR)
adaptive voltage positioning (AVP)
high bandwidth
modeling
operational amplifier (OP)
stability criteria
Type
thesis
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