DC power supplies by nihal kularatna

DC Power Supplies Power Management Electronic Systems Nihal Kularatna Electrical Engineering As we increasingly use electronic devices to direct our daily lives, so grows our dependence

DC Power Supplies Power Management

Electronic Systems

Nihal Kularatna

Electrical Engineering

As we increasingly use electronic devices to direct our daily lives, so grows

our dependence on reliable energy sources to power them Because modern

electronic systems demand steady, efficient, reliable DC voltage sources—often

at a sub-1V level—commercial AC lines, batteries, and other common resources

no longer suffice New technologies also require intricate techniques to protect

against natural and manmade disasters Still, despite its importance, practical

information on this critical subject remains hard to find.

Using simple, accessible language to balance coverage of theoretical and

practical aspects, DC Power Supplies: Power Management and Surge

Protection for Power Electronic Systems details the essentials of power

electronics circuits applicable to low-power systems, including modern portable

devices A summary of underlying principles and essential design points, it

compares academic research and industry publications and reviews DC power

supply fundamentals, including linear and low-dropout regulators Content

also addresses common switching regulator topologies, exploring resonant

conversion approaches.

Coverage includes other important topics such as:

• Control aspects and control theory

• Digital control and control ICs used in switching regulators

• Power management and energy efficiency

• Overall power conversion stage and basic protection strategies for

higher reliability

• Battery management and comparison of battery chemistries and

charge/discharge management

• Surge and transient protection of circuits designed with modern

semiconductors based on submicron dimension transistors

This specialized design resource explores applicable fundamental elements of

power sources, with numerous cited references and discussion of commercial

components and manufacturers Regardless of their previous experience level,

this information will greatly aid designers, researchers, and academics who

study, design, and produce the viable new power sources needed to propel

our modern electronic world.

DC Power Supplies Power Management

Electronic Systems

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DC Power Supplies Power Management

Electronic Systems

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This book is dedicated to Sir Arthur C Clarke (the scientist who

predicted satellite communication in the year 1945) and Prof John

Robinson Pierce (who named the transistor) … they inspired me …

With loving thanks to my wife Priyani and daughters Dulsha and Malsha and their families, who tolerate

my addiction to tech writing and electronics.

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Preface xi

Acknowledgments xiii

About.the.Author xv

Contributors xvii

1 Review.of.Fundamentals.Related.to.DC.Power.Supply.

Design.and.Linear.Regulators

1.1 Introduction 1-1

1.2 Simple.Unregulated.DC.Power.Supply.and.Estimating.the.Essential

Component.Values 1-2 1.3 Linear.Regulators 1-3

1.4 Low-Dropout.Regulators 1-18

2 Switching.Power.Supply.Topologies.and.Design.Fundamentals

2.1 Introduction 2-1

2.2 Why.Switch.Modes:.An.Overall.Approach 2-2

2.3 Basic.Switch-Mode.Power.Supply.Topologies 2-3

2.4 Applications.and.Industry-Favorite.Configurations 2-33

2.5 A.Few.Design.Examples.and.Guidelines 2-39

3 Power.Semiconductors

3.1 Introduction 3-1

3.2 Power.Diodes.and.Thyristors 3-2

3.3 Gate.Turn-Off.Thyristors 3-18

3.4 Bipolar.Power.Transistors 3-20

3.5 Power.MOSFETs 3-28

3.6 Insulated.Gate.Bipolar.Transistor.(IGBT) 3-45

3.7 MOS-Controlled.Thyristor.(MCT) 3-50

4 Resonant.Converters.and.Wireless.Power.Supplies

4.1 Introduction 4-1

4.2 Fundamentals.of.Resonant.Converters 4-1

4.3 Resonant.DC-DC.Converters 4-5

4.4 Load.Resonant.Converters.for.Contactless.Power.Supplies 4-11

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microprocessor-based systems were there at that time), and showed me a massive.

30-volume documentation set He said when the system fails, you have read these

Many.published.articles.in.Power Electronics Technology.(formerly.PCIM).magazine

Industry magazines such as EDN, Electronic Design, and Test & Measurement

About the Author

Former.CEO.of.the.Arthur.C Clarke.Institute.for.Modern.Technologies.(ACCIMT)

in.Sri.Lanka,.Nihal Kularatna is.an.electronics.engineer.with.more.than.35.years.of.

experience.in.professional.and.research.environments He.is.the.author.of.two.Electrical

Measurement Series books for the IEE (London), titled Modern Electronic Test and

Measuring Instruments (1996).and.Digital and Analogue Instrumentation: Testing and

Measurement (2003/2008),.and.two.Butterworth.(USA).titles,.Power Electronics Design

Handbook: Low Power Components and Applications (1998).and.Modern Component

Families and Circuit Block Design (2000) He coauthored Essentials of Modern

Telecommunications Systems for.Artech.House.Publishers.(2004).

Electronic Circuit Design: From Concept to Implementation.was.his.first.CRC.Press.

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he has published over 80 papers and holds 6 patents in the area of inductive power.

transfer He is the author of Wireless/Contactless Power Supply—Inductively Coupled

Resonant Converter Solutions.[2009].and.a.Senior.Member.of.IEEE

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Review of Fundamentals Related to DC Power Supply Design and Linear Regulators

peak D L

DC≈ −2 −

Smoothing capacitor Earth

(a)

C

L N

Rectification stage

Rectification stage

Smoothing capacitor Earth

Filter for noise, surges or transients

For maximum RMS line voltage

For minimum RMS line voltage

11

where.the.coefficient.k1.represents.the.Thevenin.resistance,.R o ,.of.the.circuit,.k2

rep-resents the.coefficient.representing.line.regulation,.and.k3

R R s z z R R s r z S

=+

Review of Fundamentals 1-7

If the temperature effects on the breakdown voltage can be simplified by V z (T) =.

V z nom, (1+ ∆ where.T.is.the.absolute.temperature,.k k T T ) T is.the.temperature.coefficient.of

the.zener,.related.to.the.nominal.zener.voltage,.V z,nom,.at.a.specified.temperature

FE FE

.(1.21)

FIGure 1.8 Typical.example.of.temperature.characteristics.of.reverse-biased.silicon.diodes:.(a).

Zener.breakdown;.(b).avalanche.breakdown (From.Motorola-BZX.series.)

where J1 and J2 are the current densities of transistors Q1 and Q2 respectively Since.

the.sum.of.the.two.transistor.currents.flows.through.R1,.the.voltage.across.R1.can.be

+Vin

R2 R1

Vout

V1

Q1 Q2

∆VBE V

BE

FIGure 1.9 The.circuit.diagram.of.a.bandgap.reference.

Zener breakdown region

N+ diffusion emitter

(a) (b)

6.95 Buried zener Isolation

diode

Temperature stabilizer

1

2 4

used.in.tandem.with.switching.regulators.to.power.noise-sensitive.mixed-signal.cir-cuits, RF circuit blocks, and other noise-sensitive circuits LDOs are available in a.

wide variety of output voltages and current capacities Many LDOs are tailored to

Feedback Network CapacitorOutput

Pass Element

Dynamic Load Input

FIGure 1.11 Simplified.block.diagram.of.an.LDO.

B o op

o L

I L

Vref

– +

+ –

G

S D

(a)

(b)

FIGure 1.13 PMOS.LDO:.(a).architecture;.(b).small.signal.representation.

V R

DIV

X Y

o X

A common application area of LDOs is the portable products where processors are.

coupled with many mixed-signal circuitries In these circumstances two important

V I – Input Voltage – V

2.0

3.3

3.6 10 0

Review of Fundamentals 1-23

load.transient.performance.for.a.chip.such.as.TPS763650.from.Texas.Instruments.is

shown in Figure  1.15(a), while steady-state performance is shown in Figure  1.15(b)

In Figure  1.15(a), ΔVLDR indicates the steady-state response, which is the same value

safe-operating.area.(SOA).of.

the.series.pass.device Load/line.transient.regulation A.measure.of.speed.of.the.LDO.

processor.power.supplies.with.

high.current.slew.rates Power.supply.rejection This.is.the.ability.of.the.LDO.to.

SOA.of.the.pass.transistor Output.capacitor.range Value.of.the.output.capacitance.

that.can.also.accept.any.

capacitor.value Overshoot At.startup.or.during.load.current.

transients,.output.voltage.may.

overshoot This.should.be.

within.a.maximum.limit

150 0 0

50 100

∆VLDR

t – Time – µs 150

(b) 0

50

25 0

120 80

1.0 10 100 Frequency (Hz) (b1)

Gain Phase

1.0 k 10 k 100 k 100 M

100 m –40 –400°>>

Gain

in db

0 40

120 80

1.0 10 100 Frequency (Hz) (b3)

(b)

Gain Phase

1.0 Hz 10 Hz 100 Hz

Frequency (Hz) (b2)

Gain Phase

First-Gain = 60 dB

10 Hz, Order Butterworth Highpass

Second-100 kHz, Order Butterworth Lowpass

Fourth-5 Hz Order Highpass

Single-(a)

FIGure 1.17 Noise.measurements.for.LDOs:.(a).block.diagram.of.a.filter.arrangement;.(b).a.

typical.circuit.configuration (Courtesy.of.Williams,.J.,.and.T Owen,.EDN,.May.11,.2000,.149.)

110 k

17.8 k

110 k

LT1562 IC4

12 13 14 15 16 17 18 19 20

–4.5 V 4.5 V

–4.5 V +

2.49 k

4.7 uF 4.7 uF External input

Normal input

IC1 LT1028 + –

IC2 LT1028 + – 100

2 k 6.19 k 5.9 k

4.99 k 3.16 k

FILTER INPUT

BATTERY STACK

OUTPUT TO THERMALLY RESPONDING RMS VOLTMETER.

0.1 V FULL SCALE = 100 UV RMS OF NOISE IN A 10 Hz TO 100 KHz BANDWIDTH.

100

330 uF +

RLOAD

(TYPICALLY

100 mA)

10 uF + 0.01 uF

CBYP

LT1761-5

IN OUT BYP GND SHDN

1 uF +

Typical Regulator Under Test

5 V Output

IC3 LT1224 4.5 V

–4.5 V

+ –

(b)

FIGure 1.17 (Continued)

TC1070 TC1071 TC1187 (SOT-23A-5)

ADJ

+ _

FIGure 1.18

Adjustable.LDO.circuits:.(a).a.simple.circuit.with.two.resistors.to.adjust.the.out-put;.(b).use.of.an.adjustable.reference.source.for.improving.accuracy (Courtesy.of.Paglia,.EDN,.

September.1,.1998.)

100 200 300 400

100 1000 10000

Pass element

Iout

Iin

Reference

Error amplifier

Sampling network

IGND

– +

dropout.regulator IEEE International Symposium on Circuits and Systems.4:IV–735.

20 Chava, C K., and J Silva-Martinez 2002 A robust frequency compensation

scheme.for.LDO.regulators IEEE International Symposium on Circuits and Systems.

5:V–825

21

Bontempo,.G.,.T Signorelli,.and.F Pulvirenti 2001 Low.supply.voltage,.low.qui-escent current ULDO linear regulator 8th IEEE International Conference on

Electronics, Circuits and Systems.1:409.

reference.control.and.dynamic.push-pull.techniques.for.enhancing.transient.perfor-mance.IEEE Transactions on Power Electronics.24.(4,.April):.1016–22.

31 Sandler, S., and C E Hymowitz 2005 SPICE model supports LDO regulator

designs Power Electronics Technology,.May,.26–31.

35 Kularatna, N., and J Fernando 2009 A supercapacitor technique for efficiency

improvement in linear regulators In IEEE Proceedings of IECON 09, Portugal,.

132–35

36

Kularatna,.N.,.J Fernando,.K Kankanamge,.and.L Tilakaratna 2010 Very.low.fre-quency.supercapacitor.techniques.to.improve.the.end-to-end.efficiency.of.DC-DC

converters.based.on.commercial.off.the.shelf.LDOs In.IECON.2010,.36th Annual

Conference on IEEE Industrial Electronics Society,.721–26.

37 Kularatna, N., J Fernando, K Kankanamge and X Zhang 2011 Low frequency

supercapacitor.circulation.technique.to.improve.the.efficiency.of.linear.regulators

based.on.LDO.ICs,.Proceedings.of.APEC.2011,.TX,.USA,.1161–65

used.in.these,.Figure 2.1(a).depicts.a.simple.resistor.in.series.with.a.switch.that.oper-ates.at.a.switching.frequency.of.f c where the.total.cycle.time.T s.is.comprised.of.an.on.

time.of.t on and.an.off.duration.of.t off Figure 2.1(b).depicts.the.output.voltage.appearing

across.the.resistor.R.and.with.an.average.value.of.V o Figure 2.1(c).illustrates.a.basic

concept.to.generate.the.switch.control.signal.using.a.simple.amplifier.and.a.comparator

V o

(a)

On On Off Off

Comparator Switch control

signal

+ –

v V

on s

c p

o in

on S

switching.frequency.f s , L, D, and V in.constant.while.the.load.current.keeps.dropping.

below.I OB This.makes.the.average.inductor.current.drop.below.I LB.and.dictates.a.higher

0.7 0.9

D = 1.0

0.75 0.5 0.25

of.boundary.condition:.(a).waveforms;.(b).characteristics.under.constant.V in;.(c).characteristics.

under.constant.V o.

Switching Power Supply Topologies and Design Fundamentals 2-11

while.(D + Δ1.< 1),.this.gives,

V V

D D

Discontinuous

0.25 0.50 0.75 1.0 1.25 0

V o = Constant

0.25 0.50 0.75 1.0

V V

Figure  2.4(b) indicates the operation of the buck converter characteristics in both

modes.of.operation.for.a.constant.input.voltage.V in The.conversion.ratio,.V o /V in , is.plotted

as.a.function.of.I o /I LB,.max.at.different.duty.ratios.in.this.plot,.where.we.can.recognize.the

/1

2-14 DC Power Supplies

From.Figure 2.2(b),.during.t off ,.which.is.equal.to.(1–D)T s,

.

∆I L=V L o(1−D T) s. (2.21b)From.Equations.(2.21a).and.(2.21b),

o o

T

o in

s off

– (a)

+

FIGure 2.6 Step-up.converter:.(a).basic.power.stage;.(b).CCM.waveforms;.(c).switch.on.state;.

(d).switch.off.state.