A Constant On-Time Control With Internal Active Ripple Compensation Strategy for Buck Converter With Ceramic Capacitors

Constant on-time control has been widely used due to its advantages of fast transient response and light load efficiency. However, the control scheme is intrinsically unstable if the output capacitor's equivalent series resistance (ESR) is not large enough, which needs ripple injection techniqu...

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Bibliographic Details
Published inIEEE transactions on power electronics Vol. 34; no. 9; pp. 9263 - 9278
Main Authors Ming, Xin, Xin, Yang-Li, Li, Tian-Sheng, Liang, Hua, Li, Zhao-Ji, Zhang, Bo
Format Journal Article
LanguageEnglish
Published New York IEEE 01.09.2019
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects
Active control
Active ripple compensation (ARC)
Alternating current
Amplifier design
Buck converters
Capacitors
Ceramics
Circuit stability
CMOS
Compensation
constant on-time (COT)
Inductors
low equivalent series resistance (ESR) capacitor
output-voltage dc offset
Passive components
ripple-based control
Sensors
Stability
subharmonic instability
Switching theory
Transient response
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Summary:Constant on-time control has been widely used due to its advantages of fast transient response and light load efficiency. However, the control scheme is intrinsically unstable if the output capacitor's equivalent series resistance (ESR) is not large enough, which needs ripple injection techniques to enhance loop stability. The traditional passive ripple compensation technique uses only passive component networks to realize this function, which exhibits some inherent shortcomings, including difficulties in high-speed current sensing amplifier design and large chip area consumption. This paper proposes an internal active ripple compensation strategy that senses the low-side power mosfet current and extracts relevant ac information for feedback-ripple enhancement. Output-voltage dc offset does not occur and subharmonic instability is significantly improved even with ceramic capacitors. The circuit architecture has been realized in a synchronous buck regulator with a 0.5 μm 40 V bipolar-CMOS-DMOS (BCD) process. The programmable switching frequency is up to 1 MHz and the maximum load current is 4 A. Simulation and experimental results are given to prove the proposed high performance.
ISSN:0885-8993
1941-0107
DOI:10.1109/TPEL.2018.2885778