Practical Simulations of Control Characteristics of a Current-Mode DC/DC Converter
Date Issued
2006
Date
2006
Author(s)
Wang, Ting-Hung
DOI
en-US
Abstract
In a current-mode controlled DC converter, there are two feedback loops: a current loop and a voltage loop. There are, therefore, two loop-gain functions T1 and T2 involved. Behavior of the two loop-gain functions affects system stability and converter performances. Therefore, knowledge about the actual circuit loop gains is critically important in the design of the converters. Two approaches to the design of current-mode converters are often mentioned. One uses the concept of the two loopgain
functions T1 and T2, and the other uses a new converter transfer function Fin to describe the control plant when only the current loop is closed. Fin not only reveals
stability issue but also provides information for the design of voltage-loop compensation. Obtaining these three functions under a realistic environment is the main focus of this thesis.
In this thesis, procedures were proposed to simulate the two loop-gain functions T1 and T2, the inner loop transfer function Fin, current-loop gain Ti and voltage-loop gain Tv, for a current-mode controlled DC/DC Buck converter using SIMPLIS software. These models are practical to obtain, simple to use, accurate beyond switching frequency and are easily amendable to incorporate new converter
configurations and new control schemes. Furthermore, the same SIMPLIS models can also be used to simulate time-domain waveforms without losing PWM switching frequency information. These models should provide useful information for both the converter circuit designers and the IC controller designers.
In the thesis, a brief review of the control schemes of both voltage-mode and current-mode is given in Chapter 2. Basic concept of small-signal loop gain transfer functions is reviewed. A detailed description of the two loop gain functions T1 and T2 in current-mode controlled Buck converters in this chapter lays the foundation for
Chapter 3, which is the main focus of this thesis. A step-by-step procedure is proposed to simulate loop gain T1 which is difficult to obtain using any other way. These simulation results were verified by using theoretical models. Chapter 4 concludes the thesis and suggests future research topics.
Subjects
電流型態
直流/直流電壓轉換器
控制
模擬
Simulation
Control
Current-Mode
DC/DC Converter
Type
thesis
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