Synchronized Zero-Crossing-Based Self-Tuning Capacitor Time-Constant Estimator for Low-Power Digitally Controlled DC-DC Converters

A hardware efficient method and system for estimating the time constant and measuring the current of the output capacitors in digitally controlled switch-mode power supplies is introduced. The estimator emulates the equivalent RC circuit of the output capacitor with a much smaller version, placed in...

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Bibliographic Details
Published inIEEE transactions on power electronics Vol. 29; no. 10; pp. 5106 - 5110
Main Authors Radic, Aleksandar, Straka, Adrian, Prodic, Aleksandar
Format Journal Article
LanguageEnglish
Published New York IEEE 01.10.2014
The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subjects
Capacitors
Current measurement
Electric power
Electrical engineering
Electrical equipment
Estimation
Resistors
Switched-mode power supply
Switches
estimation
DC-DC power converters
digital control
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Summary:A hardware efficient method and system for estimating the time constant and measuring the current of the output capacitors in digitally controlled switch-mode power supplies is introduced. The estimator emulates the equivalent RC circuit of the output capacitor with a much smaller version, placed in parallel, and adjusts its own resistance until the two circuits have the same time constant. The adjustment is based on a novel zero voltage crossing detection method and on synchronization with the digital pulse-width modulator operation. The effectiveness of the new estimator is verified with a 5 V to 1 V/5 A, 500-kHz buck converter prototype utilizing an optimal response controller. The experimental results show accuracy within a few tens of nanoseconds in the detection of capacitor zero-current crossing points, corresponding to a smaller than a 1.5% error in the time constant estimation, and, compared to an imperfectly tuned system, about 40% smaller voltage deviation during transients.
ISSN:0885-8993
1941-0107
DOI:10.1109/TPEL.2014.2313727