Switching Power Supply Design (Second Edition) by Abraham L

678 Pages·2003·23.76 MB·English

Second Edition
Abraham LPressman
Switching
Power Supply
Design
Abraham I. Pressman
President,SwitchtronixPower, Inc.
Waban,Massachusetts
Second Edition
McGraw-Hili
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Caracas Lisbon London Madrid MexicoCity Milan
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l.ibraryofConllJ'II'HIICataloging·in·l·ublieation Uata
Presaman.Abruham I.
Switchingpowersupplydesign I Abraham '- Pn.-","'mlln _ 2ndroo
p. em,
Indude'"index.
ISBN 0-07-0-52236-7
I Switchingpowersupplies. 2. Eleetromcapparatus and
appliances-c-Pow..rsupply. 3. "-licrot"l('Ctronics--l'ower"upply.
4. Electriccurrentconverters. r.Titlt'.
TK786K.P6P75 1998
621.381'044-dc21 97...:11668
CIP
McGraw-Hill
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Contents
Preface xix
Part1 Topologies
Chapter 1. Fundamental Switching Regulators-Buck, Boost,
andInverterTopologies 3
1.1 Introduction 3
1.2 LinearRegulators-Swtiching RegulatorAncestors 4
1.2.1 Basicoperation-meritsand drawbacks 4
1.2.2 Linearregulatordrawbacks 5
1.2.3 Powerdissipation inthe series-passtransistor 5
1.2.4 Linearregulatorefficiencyversusoutputvoltage 6
1.2.5 LinearregulatorswithPNPseries-passtransistors
forlesserrequired headroom 8
1.3 "Buck"Switching RegulatorTopology 9
1.3.1 Basicoperation 9
1.3.2 Significantcurrentwaveformsinbuckregulator 12
1.3.3 BuckregulatorefficiencyneglectingACswitching losses 13
1.3.4 BuckregulatorefficiencyincludingACswitching losses 13
1.3.5 Optimumswitchingfrequency in buckregulator 16
1.3.6 Designrelations-outputfilterinductorselection 17
1.3.7 Designrelations-outputfiltercapacitorselection 21
1.3.8 DC-isolated, regulated voltagefrom abuckregulator 23
1.4 BoostSwitching RegulatorTopology 24
1.4.1 Basicoperation 24
1.4.2 Quantitativerelations-boostregulator 26
1.4.3 Discontinuousand continuousmodesin boostregulator 27
1.4.4 Discontinuous-modeboostregulatordesign relations 28
1.4.5 Boostregulatorapplicationsand flybackcomparison 31
1.5 PolarityInvertingSwitching RegulatorTopology 32
1.5.1 Basicoperation 32
1.5.2 Design relationsin polarityinverter 34
Reference 35
v
vi Contents
Chapter2. Push-Pull and Forward ConverterTopologies 37
2.1 Introduction 37
2.2 Push-PullTopology 37
2.2.1 Basicoperation-master/slaveoutputs 37
2.2.2 Slaveline-load regulation 40
2.2.3 Slaveabsoluteoutputvoltagelevels 41
2.2.4 Masteroutputinductorminimumcurrentlimitations 41
2.2.5 Fluximbalancein push-pulltopology 42
2.2.6 Indicationsof flux imbalance 45
2.2.7 Testing forflux imbalance 48
2.2.8 Copingwithflux imbalance 49
2.2.9 Powertransformerdesignrelations 51
2.2.10 Primary,secondarypeakand rmscurrents 55
2.2.11 Transistorvoltagestressand leakageinductance
spikes 58
2.2.12 Powertransistorlosses 60
2.2.13 Outputpowerand inputvoltagelimitationsin push-pull
topology 63
2.2.14 Outputfilterdesign relations 64
2.3 ForwardConverterTopology 66
2.3.1 Basicoperation 66
2.3.2 Designrelations: output/inputvoltage, on time,turns
ratios 70
2.3.3 Slaveoutputvoltages 71
2.3.4 Secondaryload,free-wheeling diode,and inductor
currents 72
2.3.5 Relationsbetweenprimarycurrent,outputpower,
and inputvoltage 73
2.3.6 Maximumoff-voltagestressin powertransistor 74
2.3.7 Practical inputvoltage/outputpowerlimits 74
2.3.8 Forwardconverterwithunequal powerand reset
winding turns 75
2.3.9 Forwardconvertermagnetics 78
2.3.10 Powertransformerdesignrelations 81
2.3.11 Outputfilterdesign relations 84
2.4 Double-Ended ForwardConverterTopology 86
2.4.1 Basicoperation 86
2.4.2 Designrelationsand transformerdesign 88
2.5 InterleavedForwardConverterTopology 89
2.5.1 Basicoperation-merits,drawbacks,and outputpower
limits 89
2.5.2 Transformerdesign relations 92
2.5.3 Outputfilterdesign 92
Chapter3. Half- and Full-Bridge ConverterTopologies 93
3.1 Introduction 93
3.2 Half-BridgeConverterTopology 93
3.2.1 Basicoperation 93
3.2.2 Half-bridgemagnetics 95
3.2.3 Outputfiltercalculations 97
3.2.4 Blockingcapacitorto avoidflux imbalance 97
3.2.5 Half-bridgeleakageinductanceproblems 98
3.2.6 Double-endedforward converterversushalfbridge 99
Contents vii
3.2.7 Practicaloutputpowerlimitsin halfbridge 100
3.3 Full-BridgeConverterTopology 101
3.3.1 Basicoperation 101
3.3.2 Full-bridgemagnetics 103
3.3.3 Outputfiltercalculations 104
3.3.4 Transformerprimaryblockingcapacitor 104
Chapter4. Flyback ConverterTopologies 105
4.1 Introduction 105
4.2 FlybackConverter-Areasof Application 105
4.3 Discontinuous-ModeFlybacks-BasicOperation 107
4.3.1 Relation betweenoutputvoltageversusinputvoltage,
on time, outputload 108
4.3.2 Design relationsand sequentialdecision requirements 109
4.3.3 Flybackmagnetics 114
4.3.4 Flybackdisadvantages 121
4.3.5 Flybacksfor120-or 220-V-ACoperationwithno
doublerand full-wave rectifierswitching 125
4.4 Continuous-ModeFlybacks-BasicOperation 127
4.4.1 Discontinuous-modeto continuous-modetransition 130
4.4.2 Designrelations-continuous-modeflybacks 132
4.5 InterleavedFlybacks 137
4.5.1 Summationof secondarycurrentsin interleaved
flybacks 138
4.6 Double-Ended Discontinuous-ModeFlyback 138
4.6.1 Area of application 138
4.6.2 Basicoperation 139
4.6.3 Leakageinductanceeffectindouble-endedflyback 140
References 141
Chapter5. Current-Modeand Current-FedTopologies 143
5.1 Introduction 143
5.2 Current-ModeAdvantages 144
5.2.1 Avoidanceoffluximbalancein push-pullconverters 144
5.2.2 Instantaneouscorrection againstlinevoltagechanges
withoutthe delayinanerroramplifier(voltage
feedforwardcharacteristics) 145
5.2.3 Easeand simplicityof feedback-loopstabilization 145
5.2.4 Parallelingoutputs 146
5.2.5 Improvedload currentregulation 146
5.3 Current-ModeversusVoltage-ModeControlCircuits 146
5.3.1 Voltage-modecontrolcircuitry 146
5.3.2 Current-modecontrolcircuitry 149
5.4 Detailed Explanationof Current-ModeAdvantages 154
5.4.1 Linevoltageregulation 154
5.4.2 Eliminationoffluximbalance 154
5.4.3 Simplified loopstabilizationresultingfromelimination
of outputinductorinsmall-signalanalysis 155
5.4.4 Mechanismof load currentregulation 156
5.5 Current-ModeDeficienciesand Problems 158
5.5.1 Constantpeak versusconstantaverageoutputinductor
problems 158
viii Contents
5.5.2 Responseto anoutputinductorcurrentdisturbance 161
5.5.3 Slopecompensationto correctproblemsin current
mode 161
5.5.4 Slopecompensationwith apositive-goingramp voltage 163
5.5.5 Implementingslopecompensation 164
5.6 Voltage-Fedand Current-FedTopologies 165
5.6.1 Introductionand definitions 165
5.6.2 Deficienciesof voltage-fed,width-modulatedfull-
wave bridge 166
5.6.3 Buck-voltage-fedfull-wavebridgetopology-basic
operation 170
5.6.4 Buck-voltage-fedfull-wavebridgeadvantages 172
5.6.5 Drawbacksin buck-voltage-fedfull-wave bridge 174
5.6.6 Buck-current-fedfull-wavebridgetopology-basic
operation 175
5.6.7 Flyback-current-fed push-pulltopology 189
References 208
Chapter6. MiscellaneousTopologies 211
6.1 SCRResonantTopologies-Introduction 211
6.2 SCRBasics 213
6.3 SCRTurnoffby ResonantSinusoidalAnodeCurrents-
Single-Ended ResonantInverterTopology 216
6.4 SCRResonantBridgeTopologies-Introduction 222
6.4.1 SCRhalf-bridgeresonantconverter,series-Ioaded-
basicoperation 224
6.4.2 Designcalculations-SCRhalf-bridgeresonant
converter, series-loaded 226
6.4.3 Designexample-SCRhalf-bridgeresonantconverter,
series-loaded 229
6.4.4 SCRhalf-bridgeresonantconverter,shunt-loaded 230
6.4.5 Single-endedSCRresonantconvertertopologydesign 230
6.5 Cuk ConverterTopology-Introduction 237
6.5.1 Cuk converter-basicoperation 237
6.5.2 Relationbetweenoutput/Inputvoltageand Qon time 239
6.5.3 Ratesof changeof currentsin L1,L2 240
6.5.4 Reducinginputripplecurrentsto zero 241
6.5.5 Isolatedoutputsin the Cuk converter 242
6.6 Low OutputPower"Housekeeping"or "Auxiliary"Topologies-
Introduction 242
6.6.1 Housekeeping powersupply-onoutputor inputground 243
6.6.2 Housekeepingsupplyalternatives 244
6.6.3 Specifichousekeepingsupplyblockdiagrams 245
6.6.4 Royer oscillatorhousekeepingsupply-basicoperation 248
6.6.5 Minimum-parts-countflybackasahousekeepingsupply 260
6.6.6 Buckregulatorwith DC-isolatedoutputasa
housekeepingsupply 262
References 263
Contents ix
Part2 Magnetics and Circuits Designs
Chapter7. Transformerand Magnetics Design 267
7.1 Introduction 267
7.2 TransformerCore Materialsand Geometriesand PeakFlux
DensitySelection 268
7.2.1 Ferritecorelossesversusfrequencyand fluxdensity
forwidelyused corematerials 268
7.2.2 Ferritecoregeometries 271
7.2.3 Peakfluxdensityselection 275
7.3 MaximumTransformerCore OutputPower, PealFlux Density,
Core and BobbinAreas, and Coil CurrentDensity 277
7.3.1 Derivationof outputpowerrelationsforforward
convertertopology 277
7.3.2 Derivationof outputpowerrelationsfor push-pull
topology 280
7.3.3 Derivationof outputpowerrelationsforhalf-bridge
topology 286
7.3.4 Outputpowerrelationsinfull-bridgetopology 287
7.3.5 Conversionof outputpowerequationsintocharts
permitting coreand operatingfrequencyselection
ataglance 288
7.4 TransformerTemperatureRise Calculations 294
7.5 TransformerCopperLosses 298
7.5.1 Introduction 298
7.5.2 Skineffect 300
7.5.3 Skineffect-quantitativerelations 301
7.5.4 AC/DCresistanceratiofor variouswiresizesatvarious
frequencies 303
7.5.5 Skineffectwithrectangularcurrentwaveshapes 306
7.5.6 Proximityeffect 308
References 317
Chapter8. Bipolar PowerTransistor Base Drives 319
8.1 Introduction 319
8.2 Objectivesof BipolarBase DriveCircuits 320
8.2.1 Sufficientlyhighcurrentthroughoutthe on time 320
8.2.2 Aspikeof highbase inputcurrentI atinstantof
b1
turnon 321
8.2.3 Aspikeof highreversebase currentI atthe instant
b2
ofturnoff 322
8.2.4 Abase-to-emitterreversevoltagespike -1 to -5Vin
amplitudeatthe instantofturnoff 324
8.2.5 Aschemeto permitthe circuitto workequallywell
withhigh-or low-betatransistors 324
8.2.6 High efficiency 325
8.3 BakerClamps 325
x Contents
8.3.1 Bakerclampoperation 328
8.3.2 Transformercoupling intoaBakerclamp 330
8.3.3 Transformerized Bakerclamp 336
8.3.4 InherentBakerclampingin Darlingtontransistors 338
8.3.5 Proportional base drive 329
8.3.6 Miscellaneousbase driveschemes 345
References 351
Chapter9. MOSFETPower Transistorsand Input Drive Circuits 353
9.1 Introduction 353
9.2 MOSFETBasics 354
9.2.1 MOSFETdraincurrentversusdrain-to-sourcevoltage
characteristics(Id - VdC) 356
9.2.2 MOSFETinputimpedanceand required gate currents 359
9.2.3 MOSFETgate rise and fall timesfordesireddrain
currentrise and falltimes 361
9.2.4 MOSFETgate drivecircuits 362
9.2.5 MOSFETR temperaturecharacteristicsand safe
dC
operatingarea limits 365
9.2.6 MOSFETgate threshold voltageand temperature
characteristic 369
9.2.7 MOSFETswitchingspeedand temperature
characteristics 370
9.2.8 MOSFETcurrentratings 371
9.2.9 Parallelling MOSFETs 374
9.2.10 MOSFETsin push-pulltopology 377
9.2.11 MOSFETmaximumgate voltagespecifications 378
9.2.12 MOSFETdrain-to-source("body")diode 379
References 380
Chapter10. Magnetic-AmplifierPostregulators 381
10.1 Introduction 381
10.2 Linearand BuckRegulatorPostregulators 382
10.3 MagneticAmplifiers-Introduction 383
10.3.1 Squarehysteresislookmagneticcoreasafast acting
on/offswitchwithelectricallyadjustableon/offtime 385
10.3.2 Blockingand firingtimesin magnetic-amplifier
postregulators 388
10.3.3 Magnetic-amplifiercoreresetting and voltageregulation 389
10.3.4 Slave outputvoltageshutdownwith magneticamplifiers 390
10.3.5 Squarehysteresisloopcorecharacteristicsand
sources 391
in_?{;squranrrenJnnnnnrJJru",,,,.,rnJJJrn,Jrnn~Jn.J.JJ'-?-';L').Dr ~.2~
10.3.5 IfY€'f~(lf!f"(sIUc:rfTC<7("cC7rrcrra<u",,·_..- 391
sources . 396
6 Core lossand temperaturerisec~l.culatlons
402
10.3. Designexample-magnetic-amphflerpostregulator
10.3.7 407
10.3.8 Magnetic-amplifiergain 408
10.3.9 Magneticamplifiersforapush-pulloutput ..
ModUI~t?r 408
MagneticAmplifierPulse-Width and Erro.rAmphfler
10.4
10.4.1 Circuitdetails,magneticamphflerpulse-width
409
modulator-erroramplifier
412
References
Contents xi
Chapter 11. Tuman, TurnoffSWitching Lossesand Snubbers 413
11.1 Introduction 413
11.2 TransistorTurnoffLosseswithoutaSnubber 414
11.3 RCDTurnoffSnubberOperation 416
11.4 Selectionof CapacitorSize in RCDSnubber 418
11.5 Design Example-RCDSnubber 419
11.5.1 RCDsnubberreturned to positivesupplyrail 420
11.6 NondissipativeSnubbers 421
11.7 SnubberReduciton of LeakageInductanceSpiketo Avoid
Second Breakdown 422
11.8 Transformer-AidedSnubber 425
References 426
Chapter 12. Feedback-LoopStabilization 427
12.1 Introduction 427
12.2 Mechanismof LoopOscillation 429
12.2.1 Gain citerionforastablecircuit 429
12.2.2 Gain slopecriteriaforastablecircuit 430
12.2.3 Gaincharacteristicof LCoutputfilterwithand without
equivalentseriesresistance(ESR) in outputcapacitor 433
12.2.4 Pulse-width-modulatorgain 436
12.2.5 Total output LCfilterplusmodulatorand sampling
networkgain 437
12.3 Shaping Error-AmplifierGain-versus-FrequencyCharacteristic 437
12.4 Error-AmplifierTransferFuction, Polesand Zeros 440
12.5 Rules forGain SlopeChangesDue to Zero and Pole Frequencies 442
12.6 Derivationof TransferFunctionof an ErrorAmplifierwithSingle
Zero and SinglePole fromIts Schematic 444
12.7 Calculationof Type 2Error-AmplifierPhaseShiftfromIts Zero
and Pole Locations 445
12.8 Phase Shiftthrough LC FilterHaving ESRin Its OutputCapacitor 446
12.9 Design Example-StabilizingaForwardConverterFeedback
LoopwithaType 2ErrorAmplifier 448
12.10 Type 3ErrorAmplifier-When Used and TransferFunction 451
12.11 Phase Lag throughaType 3ErrorAmplifieras Functionof Zero
and Pole Locations 453
12.12 Type 3ErrorAmplifierSchematic,TransferFunction,and Zero
and Pole Locations 454
12.13 Design Example-StabilizingaForwardConverterFeedback
Loopwith aType 3ErrorAmplifier 456
12.14 ComponentSelectionto Yield DesiredType 3Error-Amplifer
Gain Curve 458
12.15 ConditionalStabilityin FeedbackLoops 459
12.16 StabilizingaDiscontinuous-ModeFlybackConverter 461
12.16.1 DCgainfromerror-amplifieroutputto outputvoltagenode 461
12.16.2 Discontinuous-modeflybacktransferfunction or AC
voltagegainfromerror-amplifieroutputto output
voltagenode 462