The Stability Analysis of a Ripple-Based Constant On-Time Voltage Regulator with a DC-Offset Correcting Circuit
Date Issued
2014
Date
2014
Author(s)
Lu, Yu-Hsuan
Abstract
In recent years, the ripple-based constant on-time (RBCOT) control scheme for voltage regulators has been adopted in many applications because of its high efficiency feature under both the heavy-load and the light-load conditions. However, the basic RBCOT control suffers from output-voltage offset problem. Therefore, an offset correcting circuit (OC) is sometimes added to the basic RBCOT scheme to correct the problem for the applications in which output voltage precision is critical. This control scheme is abbreviated as OCRBCOT in this thesis. The main focus of this thesis is on the stability issue of a buck converter regulator using the OCRBCOT control scheme.
Traditional low-frequency small-signal average models cannot be applied to the basic RBCOT due to inaccuracy [1]. A describing function approach was proposed and applied to model the behavior of a buck converter regulator employing the basic RBCOT scheme [2]. To model the conventional regulator using describing function approach is mathematically too complicated to be feasible.
In this thesis, a time-domain analysis approach with a semi-empirical observation is used to address this issue. Experimental and simulation results are given to verify the stability criterion derived. The result obtained in the thesis, while not analytically proved, provides a useful tool for addressing the stability issue of a buck regulator with OCRBCOT control scheme. It also provides a way to eliminate the proper RC value of the offset correcting circuit to minimize the chip area of the OCRBCOT controller integrated circuit.
Subjects
電壓調節器
漣波調變定導通時間
直流準位校正
描述函數
時域分析
穩定度準則
Type
thesis
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