Switching Power Supply Design-ocr, zasilacze
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Switching
Power
Supply
Abraham
I.
Pressman
President, Switchtronix Power,
Inc.
Waban, Massachusefts
Second
Edition
New York
San Francisco Washington, D.C.
Auckland
Bogota
Caracas
Lisbon London Madrid Mexico City Milan
Montreal New Delhi San Juan Singapore
Sydney
Tokyo
Toronto
Library
of
Congress Cataloging-in-PublicationData
Pressman,
Abraham
I.
Switching power
supply
design
/
Abraham
1.
F'ressman.
-
2nd
cd.
p.
cm.
Tncludea index.
ISRN 0-07-052236-7
1.
Switching power supplies.
2.
Electmn~capparatus and
appliance-Power
supply. 3. Mrcroelectronics-Power
supply.
4.
Electric current converters.
I.
Title.
TK7868.PtiP75
1998
621.381'04Lde21
97-31688
GIP
4 Division
~['l'htt
McGrmu.ffiB
hpnies
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McGraw
-Hill
Copyright
0
1998
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Contents
Preface
xix
Part
I
Topologies
Chapter
1.
Fundamental Switching Regulators-Buck,
Boost,
and Inverter Topologies
1.1
Introduction
1.2
Linear Regulators-Swtiching Regulator Ancestors
1.2.1
Basic operation-merits and drawbacks
1.2.2
Linear regulator drawbacks
1.2.3
Power dissipation in the series-pass transistor
1.2.4
Linear regulator efficiency versus output voltage
1.2.5
Linear regulators with PNP series-pass transistors
for lesser required headroom
1.3
"Buck" Switching Regulator Topology
1.3.1
Basic operation
1.3.2
Significant current waveforms in buck regulator
1.3.3
Buck regulator efficiency neglecting AC switching losses
1.3.4
Buck regulator efficiency including AC switching losses
Optimum switching frequency in buck regulator
1.3.5
1.3.6
Design relations-output
filter inductor selection
Design relations-output filter capacitor selection
1.3.7
1.3.8
DC-isolated, regulated voltage from a buck regulator
1.4
Boost Switching Regulator Topology
1.4.1
Basic operation
1.4.2
Quantitative relations-boost regulator
Discontinuous and continuous modes in boost regulator
1.4.3
1.4.4
Discontinuous-mode boost regulator design relations
Boost regulator applications and flyback comparison
1.4.5
Polarity Inverting Switching Regulator Topology
1.5.1
1.5
Basic operation
Design relations in polarity inverter
1.5.2
Reference
vi
Contents
Chapter 2. Push-Pull and Forward Converter Topologies
2.1
lntroduction
2.2
Push-Pull Topology
2.2.1
Basic operation-masterislave
outputs
2.2.2
Slave line-load regulation
2.2.3
Slave absolute output voltage levels
2.2.4
Master output inductor minimum current limitations
2.2.5
Flux imbalance in push-pull topology
2.2.6
Indications of flux imbalance
2.2.7
Testing for flux imbalance
2.2.8
Coping with flux imbalance
2.2.9
Power transformer design relations
2.2.10
Primary, secondary peak and rms currents
2.2.11
Transistor voltage stress and leakage inductance
spikes
2.2.12
Power transistor losses
2.2.13
Output power and input voltage limitations in push-pull
topology
2.2.14
Output filter design relations
2.3
Forward Converter Topology
2.3.1
Basic operation
2.3.2
Design relations: outputiinput voltage, on time, turns
ratios
2.3.3
Slave output voltages
2.3.4
Secondary load, free-wheeling diode, and inductor
currents
2.3.5
Relations between primary current, output power,
and input voltage
2.3.6
Maximum off-voltage stress in power transistor
2.3.7
Practical input voltageioutput power limits
2.3.8
Forward converter with unequal power and reset
winding turns
2.3.9
Forward converter magnetics
2.3.10
Power transformer design relations
2.3.11
Output filter design relations
2.4
Double-Ended Forward Converter Topology
2.4.1
Basic operation
2.4.2
Design relations and transformer design
2.5
Interleaved Forward Converter Topology
2.5.1
Basic operation-merits,
drawbacks, and output power
limits
Transformer design relations
2.5.2
2.5.3
Output filter design
Chapter 3. Half- and Full-Bridge Converter Topologies
3.1
lntroduction
3.2
Half-Bridge Converter Topology
3.2.1
Basic operation
3.2.2
Half-bridge magnetics
3.2.3
Output filter calculations
3.2.4
Blocking capacitor to avoid flux imbalance
3.2.5
Half-bridge leakage inductance problems
3.2.6
Double-ended forward converter versus half bridge
Contenl
3.2.7
Practical output power limits in half bridge
3.3
Full-Bridge Converter Topology
3.3.1
Basic operation
3.3.2
Full-bridge magnetics
3.3.3
Output filter calculations
3.3.4
Transformer primary blocking capacitor
Chapter 4. Flyback Converter Topologies
4.1
lntroduction
4.2
Flyback Converter-Areas of Application
4.3
Discontinuous-Mode Flybacks-Basic
Operation
4.3.1
Relation between output voltage versus input voltage,
on time, output load
4.3.2
Design relations and sequential decision requirements
4.3.3
Flyback magnetics
4.3.4
Flyback disadvantages
Flybacks for 120- or 220-V-AC operation with no
doubler and full-wave rectifier switching
4.3.5
4.4
Continuous-Mode Flybacks-Basic
Operation
4.4.1
Discontinuous-mode to continuous-mode transition
4.4.2
Design relations-continuous-mode
flybacks
4.5
Interleaved Flybacks
4.5.1
Summation of secondary currents in interleaved
flybacks
4.6
Double-Ended Discontinuous-Mode Flyback
4.6.1
Area of application
4.6.2
Basic operation
4.6.3
Leakage inductance effect in double-ended flyback
References
Chapter
5.
Current-Mode and Current-Fed Topologies
5.1
lntroduction
5.2
Current-Mode Advantages
5.2.1
Avoidance of flux imbalance in push-pull converters
5.2.2
Instantaneous correction against line voltage changes
without the delay in an error amplifier (voltage
feedforward characteristics)
5.2.3
Ease and simplicity of feedback-loop stabilization
5.2.4
Paralleling outputs
5.2.5
Improved load current regulation
5.3
Current-Mode versus Voltage-Mode Control Circuits
5.3.1
Voltage-mode control circuitry
5.3.2
Current-mode control circuitry
5.4
Detailed Explanation of Current-Mode Advantages
5.4.1
Line voltage regulation
5.4.2
Elimination of flux imbalance
5.4.3
Simplified loop stabilization resulting from elimination
of output inductor in small-signal analysis
5.4.4
Mechanism of load current regulation
5.5
Current-Mode Deficiencies and Problems
5.5.1
Constant peak versus constant average output inductor
problems
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