Estimation and Control Techniques in Power Converters

Gabriel Eirea

PhD thesis from University of California, Berkeley - 2006

Advisor:

Research Group(s): (unspecified)

Department(s): (unspecified)

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## Resumen

This thesis develops estimation and control techniques in power
converters. The target applications are voltage regulators for
modern microprocessors (VRM) and distributed DC power systems (DPS).
A method for the on-line calibration of a circuit board trace
resistance at the output of a buck converter is described. This
method is applied to obtain an accurate and high-bandwidth measurement
of the load current in the VRM applications, thus enabling an accurate
DC load-line regulation as well as a fast transient response.
Experimental results show an accuracy well within the tolerance band
of this application, and exceeding all other popular methods.
A method for estimating the phase current unbalance in a multi-phase
buck converter is presented. The method uses the information contained
in the voltage drop at the input capacitor's ESR to estimate the
average current in each phase. The method can be implemented with a
low-rate down-sampling A/D converter and is not computationally
intensive. Experimental results are presented, showing good agreement
between the estimates and the measured values.
An online adaptation method of the gain of an output current
feedforward path in VRM applications is developed. The feedforward
path can improve substantially the converter's response to load
transients but it depends on parameters of the power train that are
not known with precision. By analyzing the error voltage and finding
its correlation with the parameter error, a gradient algorithm is
derived that makes the latter vanish. Experimental results show a
substantial improvement of the transient response to a load current
step in a prototype VRM.
Impedance interactions between interconnected power subsystems are
analyzed. Typical examples of these interconnections are a power
converter with a dynamic load, a power converter with an input line
filter, power converters connected in parallel or cascade, and
combinations of the above. A survey of the most relevant results in
this area is presented together with detailed examples. Fundamental
limits on the performance of the interconnected systems are exposed
and a system-level design approach is proposed and corroborated with
simulations.

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