Single Conversion stage AMplifier - SICAM

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Single Conversion stage AMplifier - SICAM
Ljusev, Petar
Publication date:
2006
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Citation (APA):
Ljusev, P. (2006). Single Conversion stage AMplifier - SICAM. Technical University of Denmark.

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Petar Ljuˇsev
SIngle Conversion stage AMplifier
- SICAM
PhD thesis, December 2005

To Elena and Emma,
for their endless love and devotion

Preface
The work presented in this thesis is part of the project ”SICAM - SIngle Conversion
stage AMplifier”, funded by the Danish Energy Authority under the EFP2002 program,
J.nr. 1273/02-0001. The project was carried out at the Ørsted DTU Automation depart-
·
ment within its Power Electronics Group (PEG) during the period November 15th 2002
to December 31st 2005. On the industry side, the cooperation with Bang & Olufsen ICE-
power a/s in Kgs. Lyngby has given additional quality to the project, by emphasizing its
relevance and importance within the extremely ”crowded” consumer audio market.
Part of the work concerning the direct audio power amplifiers for portable applications
and their digital modulators was conducted during my 1,5 months long external research
stayintheLaboratoryforLowPowerManagementandIntegratedSMPSattheUniversity
of Toronto in Canada, under the supervision of Professor Aleksandar Prodi´c.
First I would like to express deepest gratitude to my supervisor Professor Michael
A.E. Andersen for taking me as his Ph.D. student to work on this highly interesting
topic,providingunboundedsupportformywideresearchinterests,managingthepractical
issuesaboutthedemandingproject,aswellasspendinglotsofhoursonfruitfuldiscussions
and sharing his vast knowledge. Together with the colleagues from the Power Electronics
Group and the Ørsted DTU Department, they are most responsible for making me feel
·
so comfortable and secure.
The practical relevance and technical appeal of the project would be much less pro-
nounced, if it was not for the tremendous effort shown by my second supervisor Lars
Petersen, from the cooperating company Bang & Olufsen ICEpower. His curious remarks
and on-place questions have always provoked me to rejudge the conclusions and find a
way out of the large maze I was put into when undertaking this project. The enthusiastic
B&O ICEpower employees showing me around the labs and attending my presentations
helped me build a serious approach so needed when tackling such a relevant subject.
Another thanks goes to my external research supervisor Professor Aleksandar Prodi´c
from the University of Toronto, for allowing me to spend a challenging few weeks in his
”fully digital world” and sharing his ideas and opinions, making the time spent in Toronto
an unforgettable experience.
During these three stressful years of hard work, tight schedules and numerous obliga-
tions, I have always found a peaceful shelter and source of endless joy and fulfilment in my
closest family - my wife Elena and our little daughter Emma. I would like to thank you
for being always by my side and showing me that the most important things in life cannot
be represented by equations, expressed in numbers nor measured in physical units...
Kongens Lyngby Petar Ljuˇsev
December 2005

Abstract
This Ph.D. thesis presents a thorough analysis of the so called SICAM - SIngle Converter
stage AMplifier approach to building direct energy conversion audio power amplifiers.
The mainstream approach for building isolated audio power amplifiers today consists
of isolated DC power supply and Class D amplifier, which essentially represents a two
stage solution, where each of the components can be viewed as separate and independent
part. The proposed SICAM solution strives for direct energy conversion from the mains
to the audio output, by dedicating the operation of the components one to another and
integratingtheirfunctions,sothatthefinalaudiopoweramplifierrepresentsasingle-stage
topology with higher efficiency, lower volume, less board space, lower component count
and subsequently lower cost.
The SICAM approach is both applicable to non-isolated and isolated audio power
amplifiers, but the problems encountered in these two cases are different. Non-isolated
SICAM solutions are intended for both AC mains-connected and battery-powered de-
vices. In non-isolated mains-connected SICAMs the main idea is to simplify the power
supply or even provide integrated power factor correction (PFC) functions, while still
maintaining low component stress and good audio performance by generally decreasing
the input voltage level to the Class D audio power amplifier. On the other hand, non-
isolatedbattery-poweredSICAMshavetocopewiththeeverchangingbatteryvoltageand
provide output voltage levels which are both lower and higher than the battery voltage,
while still being simple and single-stage energy conversion solutions. In isolated SICAMs
the isolation transformer adjusts the voltage level on the secondary side to the desired
level, so the main challenges here are decreasing the size of themagnetic core and reducing
the number and size of bulky reactive components as much as possible.
ThemainfocusofthisthesisisdirectedtowardstheisolatedSICAMsandespeciallythe
so called isolated SICAM with non-modulated transformer voltages. The latter is found
to be the most interesting isolated SICAM solution for the modern multichannel audio
power amplification systems, since all of the output stages corresponding to the different
audio channels can reuse the same input stage and transformer core. While the proposed
approach tends to be very simple from topological perspective and allows for reduction of
reactive component count, the commutation of the load current in the output bridge and
the bridge itself are much more complicated than their Class D predecessors.
The main contribution of the thesis can be found in the thorough analysis of the
present topologies for isolated SICAMs, as well as the numerous structural improvements
and several newly proposed control methods for alleviating the problem of load current
commutation and high-performance control of the whole SICAM. Another significant
contribution is the presentation of several interesting topologies and associated control
principles in the field of non-isolated SICAMs for mains-connected and portable audio
amplifiers.

Resum`e (Abstract in Danish)
Denne Ph.D. afhandling giver en grundig analyse af den s˚a kaldte SICAM - SIngle Con-
verter stage AMplifier fremgangsm˚ade til opbygning af audio effektforstærkere til direkt
energiomforming. Den aktuelle fremgangsm˚ade til opbygning af isolerede audio effekt-
forstærkere i dag best˚ar af en isoleret DC elforsyning efterfulgt af en Klasse D audio
effektforstærker, som faktisk repræsenterer to-trins løsning, hvor hver halvdel kan ses som
seperatoguafhengigdel.Denforesl˚aedeSICAM-løsningstræberefters˚adirekteenergiom-
forming fra lysnetindgangen til audioudgangen som overhovedet muligt, ved at dedikere
virkningsm˚aden af delene til hinanden og integrere deres funktioner s˚aledes, at den en-
delige audio effektforstærker repræsentere en en-trins topologi med højere effektivitet,
mindre volumen, mindre printareal, færre komponenter og dermed lavere omkostninger.
SICAM fremgangsm˚aden kan bruges til b˚ade uisolerede og isolerede audio effekt-
forstærkere, men problemstillingerne som i de to tilfælde er i grunden meget forskellige.
Uisolerede SICAMs anvendes til b˚ade lysnettilsluttede og batteridrevne apparater. Hov-
edideen i de uisolerede lysnettilsluttede SICAMs er at forenkle spændingsforsyningen og
lave PFC-funktion, mens det lav komponentstress og den god audioperformance bevares
ved at reducere indgangsspændingen til Klasse D forstærkeren. Uisolerede batteridrevne
SICAMs skal klare den varierende batterispænding og skabe en udgangsspænding, som er
b˚ade lavere og højere end batterispænding, men de skal stadigvæk være simple og en en-
trins energiomformer. I transformatoren i isolerede SICAMs designes spændingsniveauet
p˚asekundærentildetønskedeniveauogderforerdevigtigsteudfordringerheratreducere
volumen af den magnetiske kerne og reducere antallet af reaktive komponenter s˚a meget
som muligt.
Hovedfokus i denne afhandling ligger p˚a isolerede SICAMs og især de s˚akaldte isol-
erede SICAM med umodulerede transformatorspændinger. Den ovennævnte omformer er
den mest interessante SICAM-løsning til multikanalens audio effektforstærkersystemer,
fordi alle udgangstrinnene kan bruge det samme indgangstrin og den samme transforma-
torkerne. Den foresl˚aede løsning er meget enkelt fra en topologiside og tillader reduktion
af antalet of reaktive komponenter p˚a sekundærsiden, men kommuteringen af belast-
ningsstrømmen i udgangstrinnet og udgangstrinnets ombygning selv er mere indviklet
end i Klasse D forstærkeren.
Afhandlingens hovedbidrag findes i den grundige analyse af nuværende topologier for
isolerede SICAMs, s˚avel som flere strukturele forbedringer og nogle foresl˚aede kontrol
metoder til at forbedre kommuteringen af belastningsstrømmen i udgangstrinnet og re-
alisere højperformance styring af hele SICAM-trinnet. Det anden væsentlige bidrag er
fremvisningen af adskillige interessanter topologier og deres styrestrategier til uisolerede
SICAMs til lysnettilslutning og brbare audio effektforstærkere.