Improvement of out-of-band Behaviour in Switch-Mode Amplifiers and Power Supplies by their ...

278 Pages·2010·11.85 MB·English

Arnold Knott
Improvement of out-of-band
Behaviour in Switch-Mode
Amplifiers and Power Supplies by
their Modulation Topology
Ph.d. Thesis, August 2010

Arnold Knott
Improvement of out-of-band
Behaviour in Switch-Mode
Amplifiers and Power Supplies by
their Modulation Topology
Ph.d. Thesis, August 2010
Preface
The Ph.D. project“Improvement of out-of-band Behaviour in Switch-Mode
Amplifiers and Power Supplies by their Modulation Topology”was carried
outunderthePh.D.schoolat“DTUElektro”atthe“TechnicalUniversityof
Denmark”inKongensLyngbyinclosecollaborationwiththeamplifiergroup
from“Harman/Becker Automotive Systems GmbH”in Straubing, Germany.
During the project, a research visit was carried out at the“Power Electron-
ics Systems Laboratory”at the“Eidgen¨ossische Technische Hochschule”in
Zu¨rich. During the project time, I had the pleasure to meet and discuss
with many specialists in the field. Special thanks goes to
• the students Martin Persson, Jacob Mebus Meyer, Annie Rydholm,
Daniel Nilsson, Søren Pedersen, Nicholai Rudbeck Zickert, Dennis
Nielsen,TheisChristiansen,TokeAndersen,KristianLindberg-Poulsen,
Tore Stegenborg-Andersen, Rasmus Trock Kinnerup, Jakob Døllner
Mønster, Niels Christian Buhl, Lasse Emil Korff, Johan Grundtvig,
Søren Jørgensen Herslund and all other participants in the“Electron-
ics Group”, for being interested in exploring switch-mode power elec-
tronics together with me,
• the supervisors Gerhard Paffinger and Prof. Michael A. E. Andersen,
for their inspiration and excellent mentoring along the way,
• the“Electronics Group”, especially Assoc. Prof. Ole Cornelius Thom-
sen, Mikkel Christian Kofod Høyerby, Lars Tønnes Jacobsen, Zhe
Zhang, Kaspar Sinding Meyer and Thomas Andersen, for there rich
discussions,
• the colleagues at “Harman/Becker Automotive Systems GmbH”, for
keeping my research efforts practically relevant,
• thecolleaguesGeraldStanleyat“CrownInternationalInc.” andDavid
McCorkleat“McCorkle Design Group”, for preventingme from falling
into pitfalls, that have been solved many decades ago,
• the“Power Electronics Systems”group at the ETH Zu¨rich for showing
me world-class approaches to build even better switch-mode power
electronics.
Summary
Switch-modepowerelectronicsisdisturbingotherelectroniccircuitsbyemis-
sionofelectromagneticwavesandsignals. Toallowtransmissionofinforma-
tion, a set of regulatory rules (electromagnetic compatibility (EMC)) were
created to limit this disturbance. To fulfill those rules in power electronics,
shielding and filtering is required, which is limiting the size reduction. The
motivationforthisprojectwastofindalternativewaystoavoidtroublewith
interference of switch-mode power electronics and transmission and receiver
circuits. An especial focus is given to audio power amplifiers.
After a historical overview and description of interaction between power
electronics and electromagnetic compatibility (chapter 1), the thesis will
first show the impact of the high frequency signals on the audio perfor-
mance of switch-mode audio power amplifiers (chapter 2). Therefore the
work of others will be put into perspectiveand self-oscillatingamplifiers will
be compared with external synchronized topologies.
After that, solutions to the problem, which are widespread in industry will
be given and explained (chapter 3). The challenges and advantages will be
described.
The improvement of the described problem where four different approaches:
• Multi Carrier Modulation (MCM)
• Active Electromagnetic Cancellation (AEC)
• Current Driven Power Stages (CDP)
• Radio Frequency Power Electronics (RF SMPS)
Multi Carrier Modulation (chapter 4) is using more than one external car-
rier and generating multiple PWM signals. Those are combined by a logic
circuit to one pulse coded information stream. The average of this stream is
proportionaltothemodulatedsignal, whilethespectralpeaksoftheswitch-
ingfrequenciesarehalfcomparedtostate-of-theartpulsewidthmodulation
(PWM).
Active Electromagnetic Cancellation (chapter 5) has been known as active
filtering in power electronics. It has been applied to switch mode audio
power amplifiers. The specialty for the later will be described and a design
is shown, decreasing the undesired spectrum by 15 dB.
A different approach to tackle the problem is given by an alternative power
stageinCurrentdrivenPowerStages(chapter6). Afocusofthisapproachis
to minimize the biggest components, the inductors, in the filters of switch-
mode power electronics. This approach results in a size reduction of the
filters by around 84 %.
A very promising approach to remove the interference of power electronics
circuits and telecommunication circuits is to stay away from the frequen-
cies used for information transmission. Even though the electromagnetic
spectrum is used without any exceptions, the situation can be optimized for
audio applications. This is done by using switching frequencies beyond the
communication frequencies and will be described in Radio Frequency Power
Electronics (chapter 7).
Each chapter ends with a section printed in italic. These paragraphs are
meant to link the respective chapter with the rest of the work and therefore
enables the reader to investigate only parts of the work, while getting the
perspective to the rest.
Dansk Resum´e
Switch-modeeffektelektronikforstyrrerandreelektroniskekredsløbvedemis-
sion af elektromagnetiske felter og signaler. Derfor blev en række regula-
toriske regler (elektromagnetisk kompatibilitet) sat op, som muliggør trans-
mission af informationer. For at opfylde disse regler, er skærmning og
filtrering nødvendig, disse begrænser størrelsesreduktion af effektelektron-
ikkredsløb. Motivationen til projektet var, at finde andre muligheder for
at forhindre problemer med kobling mellem switch-mode effektelektronik og
transmission- eller modtagerkredsløb. Der var specielt fokus p˚a audio effek-
tforstærker.
Efter et historisk overblik og beskrivelse om vekselvirkning mellem effek-
telektronik og elektromagnetisk kompatibilitet (kapitel 1), beskriver afhan-
dlingen p˚avirkning af højfrekvente signaler p˚a lydkvalitet af switch-mode
audio effektforstærkere (kapitel 2). Andres arbejde vil blive perspektiveret
og selvoscillerende systemer vil blive sammenlignet med ekstern synkronis-
erede topologier.
Efterfølgende vil nuværende udbredte løsninger, som anvendes i industrien,
blive forklaret (kapitel 3). Deres udfordringer og fordele vil blive beskrevet.
Forbedring af det beskrevede problem var fire løsninger:
• Multi Carrier Modulation (MCM)
• Active Electromagnetic Cancellation (AEC)
• Strømdrevet effekttrin (CDP)
• Radiofrekvens effektelektronik (RF SMPS)
MultiCarrierModulation(kapitel4)benyttermereendeneksterncarrierog
generer derfor flere pulsebredemodulation (PWM) signaler. Disse signaler
bliver kombineret ved logiske kredsløb og skaber en pulstog. I gennemsnit
er pulsene proportionale med modulationssignalet, mens de spektrale toppe
kun er halvt s˚a store som i konventionel PWM.
ActiveElectromagneticCancellation(kapitel5)harværetkendtieffektelek-
tronik som aktiv filtrering. Princippet blev anvendt p˚a switch-mode audio
effektforstærkere. Det specielle hermed er beskrevet og en prototype viser
en forbedring p˚a 15 dB.
Etandetforsøgp˚aatangribeproblemetergjortvedetalternativeeffekttrin
i CDPen (kapitel 6). M˚alet af forsøget er at mindske de største komponen-
ter, nemlig spolerne, i filtre fra switch-mode effektelektronik. Metoden giver
en formindskelse p˚a cirka 84 %.
En meget lovende mulighed for at fjerne interferens mellem effektelektronik
og telekommunikationskredsløb er at undg˚a frekvenser, som benyttes til in-
formationstransmission. Selvom hele det elektromagnetiske spektrum bliver
benyttetudenundtagelser,kansituationenforbedresindenforaudioapplika-
tioner. Det bliver gjort ved at sætte switch-frekvensen over de benyttede
kommunikationsfrekvenser og er beskrevet i radiofrekvens effektelektronik
(kapitel 7).
Hvert kapitel slutter med en paragraf i kursiv. Denne paragraf forbinder
kapitlet med resten af afhandlingen og skal derfor give mulighed for læseren
for at undersøge dele af beskrivelsen, mens man beholder sammenhængen til
resten.
Deutsche Zusammenfassung
Schaltnetzteile st¨oren andere elektronische Schaltungen durch Aussendung
elektromagnetischerFelderundSignale. UmdieU¨bermittlungvonInforma-
tionen zu erm¨oglichen, wurden regulative Bestimmungen (Elektromagnetis-
che Vertr¨aglichkeit) geschaffen, welche die St¨orungen limitieren sollen. Um
dieseRegelnzuerfu¨llen,isteserforderlich,dieleistungselektronischenSchal-
tungen zu schirmen und zu filtern, was deren physikalische Gr¨oße bestimmt.
Motivation dieses Projekts ist es, Alternativen zu finden, die die Probleme
der Beeintr¨achtigung von Sendern und Empf¨angern durch Schaltnetzteile
verhindern. Spezieller Fokus liegt dabei auf geschalteten Audioverst¨arkern.
NacheinemhistorischenU¨berblickundderBeschreibungderWechselwirkung
vonLeistungselektronikundelektromagnetischerVertr¨aglichkeit(Kapitel1),
zeigt diese Arbeit den Einfluss hochfrequenter Signale auf die Audioperfor-
mance von geschalteten Audioleistungsverst¨arkern (Kapitel 2). Dazu wird
dieArbeitvonanderenerl¨autertundselbstoszillierendeSystemewerdenmit
extern synchronisierten verglichen.
Danach werden die in der Industrie weitverbreiteten L¨osungen vorgestellt
(Kapitel 3) und deren Herausforderungen und M¨oglichkeiten aufgezeigt.
DieVerbesserungderProblemstellungsindvierverschiedeneVorgehensweisen:
• Multi Carrier Modulation (MCM)
• Active Electromagnetic Cancelation (AEC)
• Stromgespeiste Leistungsstufen (CDP)
• Radiofrequenzleistungselektronik (RF SMPS)
MultiCarrierModulation(Kapitel4)benu¨tztmehralseinexternesTr¨agersig-
nal und generiert damit mehrere PWM-Signale. Diese werden anhand einer